draft-ietf-hip-mm-02.txt   draft-ietf-hip-mm-03.txt 
Network Working Group T. Henderson (editor) Network Working Group T. Henderson (editor)
Internet-Draft The Boeing Company Internet-Draft The Boeing Company
Expires: January 18, 2006 July 17, 2005 Expires: August 28, 2006 February 24, 2006
End-Host Mobility and Multihoming with the Host Identity Protocol End-Host Mobility and Multihoming with the Host Identity Protocol
draft-ietf-hip-mm-02 draft-ietf-hip-mm-03
Status of this Memo Status of this Memo
By submitting this Internet-Draft, each author represents that any By submitting this Internet-Draft, each author represents that any
applicable patent or other IPR claims of which he or she is aware applicable patent or other IPR claims of which he or she is aware
have been or will be disclosed, and any of which he or she becomes have been or will be disclosed, and any of which he or she becomes
aware will be disclosed, in accordance with Section 6 of BCP 79. aware will be disclosed, in accordance with Section 6 of BCP 79.
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF), its areas, and its working groups. Note that Task Force (IETF), its areas, and its working groups. Note that
skipping to change at page 1, line 33 skipping to change at page 1, line 33
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
The list of current Internet-Drafts can be accessed at The list of current Internet-Drafts can be accessed at
http://www.ietf.org/ietf/1id-abstracts.txt. http://www.ietf.org/ietf/1id-abstracts.txt.
The list of Internet-Draft Shadow Directories can be accessed at The list of Internet-Draft Shadow Directories can be accessed at
http://www.ietf.org/shadow.html. http://www.ietf.org/shadow.html.
This Internet-Draft will expire on January 18, 2006. This Internet-Draft will expire on August 28, 2006.
Copyright Notice Copyright Notice
Copyright (C) The Internet Society (2005). Copyright (C) The Internet Society (2006).
Abstract Abstract
This document defines mobility and multihoming extensions to the Host This document defines mobility and multihoming extensions to the Host
Identity Protocol (HIP). Specifically, this document defines a Identity Protocol (HIP). Specifically, this document defines a
general "LOCATOR" parameter for HIP messages that allows for a HIP general "LOCATOR" parameter for HIP messages that allows for a HIP
host to notify peers about alternate addresses at which it may be host to notify peers about alternate addresses at which it may be
reached. This document also defines elements of procedure for reached. This document also defines elements of procedure for
mobility of a HIP host-- the process by which a host dynamically mobility of a HIP host-- the process by which a host dynamically
changes the primary locator that it uses to receive packets. While changes the primary locator that it uses to receive packets. While
the same LOCATOR parameter can also be used to support end-host the same LOCATOR parameter can also be used to support end-host
multihoming, detailed procedures are left for further study. multihoming, detailed procedures are left for further study.
Table of Contents Table of Contents
1. Introduction and Scope . . . . . . . . . . . . . . . . . . . . 4 1. Introduction and Scope . . . . . . . . . . . . . . . . . . . . 4
2. Terminology and Conventions . . . . . . . . . . . . . . . . . 5 2. Terminology and Conventions . . . . . . . . . . . . . . . . . 6
3. Protocol Model . . . . . . . . . . . . . . . . . . . . . . . . 6 3. Protocol Model . . . . . . . . . . . . . . . . . . . . . . . . 7
3.1 Operating Environment . . . . . . . . . . . . . . . . . . 6 3.1. Operating Environment . . . . . . . . . . . . . . . . . . 7
3.1.1 Locator . . . . . . . . . . . . . . . . . . . . . . . 6 3.1.1. Locator . . . . . . . . . . . . . . . . . . . . . . . 9
3.1.2 Mobility . . . . . . . . . . . . . . . . . . . . . . . 7 3.1.2. Mobility overview . . . . . . . . . . . . . . . . . . 10
3.1.3 Multihoming . . . . . . . . . . . . . . . . . . . . . 7 3.1.3. Multihoming overview . . . . . . . . . . . . . . . . . 10
3.2 Protocol Overview . . . . . . . . . . . . . . . . . . . . 8 3.2. Protocol Overview . . . . . . . . . . . . . . . . . . . . 10
3.2.1 Mobility with single SA pair . . . . . . . . . . . . . 8 3.2.1. Mobility with single SA pair (no rekeying) . . . . . . 11
3.2.2 Host multihoming . . . . . . . . . . . . . . . . . . . 10 3.2.2. Host multihoming . . . . . . . . . . . . . . . . . . . 13
3.2.3 Site multihoming . . . . . . . . . . . . . . . . . . . 12 3.2.3. Site multihoming . . . . . . . . . . . . . . . . . . . 15
3.2.4 Dual host multihoming . . . . . . . . . . . . . . . . 12 3.2.4. Dual host multihoming . . . . . . . . . . . . . . . . 15
3.2.5 Combined mobility and multihoming . . . . . . . . . . 13 3.2.5. Combined mobility and multihoming . . . . . . . . . . 16
3.2.6 Using LOCATORs across addressing realms . . . . . . . 13 3.2.6. Using LOCATORs across addressing realms . . . . . . . 16
3.2.7 Network renumbering . . . . . . . . . . . . . . . . . 13 3.2.7. Network renumbering . . . . . . . . . . . . . . . . . 16
3.2.8 Initiating the protocol in R1 or I2 . . . . . . . . . 13 3.2.8. Initiating the protocol in R1 or I2 . . . . . . . . . 16
3.3 Other Considerations . . . . . . . . . . . . . . . . . . . 15 3.3. Other Considerations . . . . . . . . . . . . . . . . . . . 17
3.3.1 Address Verification . . . . . . . . . . . . . . . . . 15 3.3.1. Address Verification . . . . . . . . . . . . . . . . . 17
3.3.2 Credit-Based Authorization . . . . . . . . . . . . . . 15 3.3.2. Credit-Based Authorization . . . . . . . . . . . . . . 18
3.3.3 Preferred locator . . . . . . . . . . . . . . . . . . 16 3.3.3. Preferred locator . . . . . . . . . . . . . . . . . . 19
3.3.4 Interaction with Security Associations . . . . . . . . 17 3.3.4. Interaction with Security Associations . . . . . . . . 20
4. LOCATOR parameter format . . . . . . . . . . . . . . . . . . . 20 4. LOCATOR parameter format . . . . . . . . . . . . . . . . . . . 23
4.1 Traffic Type and Preferred Locator . . . . . . . . . . . . 21 4.1. Traffic Type and Preferred Locator . . . . . . . . . . . . 24
4.2 Locator Type and Locator . . . . . . . . . . . . . . . . . 22 4.2. Locator Type and Locator . . . . . . . . . . . . . . . . . 25
4.3 UPDATE packet with included LOCATOR . . . . . . . . . . . 22 4.3. UPDATE packet with included LOCATOR . . . . . . . . . . . 25
5. Processing rules . . . . . . . . . . . . . . . . . . . . . . . 23 5. Processing rules . . . . . . . . . . . . . . . . . . . . . . . 26
5.1 Locator data structure and status . . . . . . . . . . . . 23 5.1. Locator data structure and status . . . . . . . . . . . . 26
5.2 Sending LOCATORs . . . . . . . . . . . . . . . . . . . . . 24 5.2. Sending LOCATORs . . . . . . . . . . . . . . . . . . . . . 26
5.3 Handling received LOCATORs . . . . . . . . . . . . . . . . 25 5.3. Handling received LOCATORs . . . . . . . . . . . . . . . . 28
5.4 Verifying address reachability . . . . . . . . . . . . . . 26 5.4. Verifying address reachability . . . . . . . . . . . . . . 30
5.5 Credit-Based Authorization . . . . . . . . . . . . . . . . 28 5.5. Credit-Based Authorization . . . . . . . . . . . . . . . . 31
5.5.1 Handling Payload Packets . . . . . . . . . . . . . . . 28 5.5.1. Handling Payload Packets . . . . . . . . . . . . . . . 31
5.5.2 Credit Aging . . . . . . . . . . . . . . . . . . . . . 29 5.5.2. Credit Aging . . . . . . . . . . . . . . . . . . . . . 33
5.6 Changing the preferred locator . . . . . . . . . . . . . . 30 5.6. Changing the preferred locator . . . . . . . . . . . . . . 34
6. Policy considerations . . . . . . . . . . . . . . . . . . . . 32 6. Security Considerations . . . . . . . . . . . . . . . . . . . 36
7. Security Considerations . . . . . . . . . . . . . . . . . . . 33 6.1. Impersonation attacks . . . . . . . . . . . . . . . . . . 36
7.1 Impersonation attacks . . . . . . . . . . . . . . . . . . 33 6.2. Denial of Service attacks . . . . . . . . . . . . . . . . 37
7.2 Denial of Service attacks . . . . . . . . . . . . . . . . 34 6.2.1. Flooding Attacks . . . . . . . . . . . . . . . . . . . 37
7.2.1 Flooding Attacks . . . . . . . . . . . . . . . . . . . 34 6.2.2. Memory/Computational exhaustion DoS attacks . . . . . 38
7.2.2 Memory/Computational exhaustion DoS attacks . . . . . 35 6.3. Mixed deployment environment . . . . . . . . . . . . . . . 38
7.3 Mixed deployment environment . . . . . . . . . . . . . . . 35 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 40
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 37 8. Authors . . . . . . . . . . . . . . . . . . . . . . . . . . . 41
9. Authors . . . . . . . . . . . . . . . . . . . . . . . . . . . 38 9. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 42
10. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . 39 10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 43
11. References . . . . . . . . . . . . . . . . . . . . . . . . . 40 10.1. Normative references . . . . . . . . . . . . . . . . . . . 43
11.1 Normative references . . . . . . . . . . . . . . . . . . . 40 10.2. Informative references . . . . . . . . . . . . . . . . . . 43
11.2 Informative references . . . . . . . . . . . . . . . . . . 40 Appendix A. Changes from previous versions . . . . . . . . . . . 44
Author's Address . . . . . . . . . . . . . . . . . . . . . . . 41 A.1. From nikander-hip-mm-00 to nikander-hip-mm-01 . . . . . . 44
A. Changes from previous versions . . . . . . . . . . . . . . . . 42 A.2. From nikander-hip-mm-01 to nikander-hip-mm-02 . . . . . . 44
A.1 From nikander-hip-mm-00 to nikander-hip-mm-01 . . . . . . 42 A.3. From -02 to draft-ietf-hip-mm-00 . . . . . . . . . . . . . 44
A.2 From nikander-hip-mm-01 to nikander-hip-mm-02 . . . . . . 42 A.4. From draft-ietf-hip-mm-00 to -01 . . . . . . . . . . . . . 45
A.3 From -02 to draft-ietf-hip-mm-00 . . . . . . . . . . . . . 42 A.5. From draft-ietf-hip-mm-01 to -02 . . . . . . . . . . . . . 45
A.4 From draft-ietf-hip-mm-00 to -01 . . . . . . . . . . . . . 43 A.6. From draft-ietf-hip-mm-02 to -03 . . . . . . . . . . . . . 45
A.5 From draft-ietf-hip-mm-01 to -02 . . . . . . . . . . . . . 43 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 47
Intellectual Property and Copyright Statements . . . . . . . . 44 Intellectual Property and Copyright Statements . . . . . . . . . . 48
1. Introduction and Scope 1. Introduction and Scope
The Host Identity Protocol [1] (HIP) supports an architecture that The Host Identity Protocol [1] (HIP) supports an architecture that
decouples the transport layer (TCP, UDP, etc.) from the decouples the transport layer (TCP, UDP, etc.) from the
internetworking layer (IPv4 and IPv6) by using public/private key internetworking layer (IPv4 and IPv6) by using public/private key
pairs, instead of IP addresses, as host identities. When a host uses pairs, instead of IP addresses, as host identities. When a host uses
HIP, the overlying protocol sublayers (e.g., transport layer sockets HIP, the overlying protocol sublayers (e.g., transport layer sockets
and ESP Security Associations) are instead bound to representations and ESP Security Associations) are instead bound to representations
of these host identities, and the IP addresses are only used for of these host identities, and the IP addresses are only used for
packet forwarding. However, each host must also know at least one IP packet forwarding. However, each host must also know at least one IP
address at which its peers are reachable. Initially, these IP address at which its peers are reachable. Initially, these IP
addresses are the ones used during the HIP base exchange [2]. addresses are the ones used during the HIP base exchange [2].
This document defines a generalized LOCATOR parameter for use in HIP One consequence of such a decoupling is that new solutions to
messages. The LOCATOR parameter allows a HIP host to notify a peer network-layer mobility and host multihoming are possible. There are
about alternate addresses at which it is reachable. The LOCATORs may potentially many variations of mobility and multihoming possible.
be merely IP addresses, or they may have additional multiplexing and The scope of this document encompasses messaging and elements of
demultiplexing context to aid the packet handling in the lower procedure for basic network-level mobility and simple multihoming,
layers. For instance, an IP address may need to be paired with an leaving more complicated scenarios and other variations for further
ESP SPI so that packets are sent on the correct SA for a given study. Specifically,
address.
This document also specifies the messaging and elements of procedure This document defines a generalized LOCATOR parameter for use in
for end-host mobility of a HIP host-- the sequential change in HIP messages. The LOCATOR parameter allows a HIP host to notify a
preferred IP address used to reach a host. In particular, message peer about alternate addresses at which it is reachable. The
flows to enable successful host mobility, including address LOCATORs may be merely IP addresses, or they may have additional
verification methods, are defined herein. However, while the same multiplexing and demultiplexing context to aid the packet handling
LOCATOR parameter is intended to support host multihoming (parallel in the lower layers. For instance, an IP address may need to be
support of a number of addresses), and experimentation is encouraged, paired with an ESP SPI so that packets are sent on the correct SA
detailed elements of procedure for host multihoming are left for for a given address.
further study.
This document also specifies the messaging and elements of
procedure for end-host mobility of a HIP host-- the sequential
change in preferred IP address used to reach a host. In
particular, message flows to enable successful host mobility,
including address verification methods, are defined herein.
However, while the same LOCATOR parameter is intended to support
host multihoming (parallel support of a number of addresses), and
experimentation is encouraged, detailed elements of procedure for
host multihoming are left for further study.
While HIP can potentially be used with transports other than the ESP
transport format [5], this document largely assumes the use of ESP
and leaves other transport for further study.
There are a number of situations where the simple end-to-end There are a number of situations where the simple end-to-end
readdressing functionality is not sufficient. These include the readdressing functionality is not sufficient. These include the
initial reachability of a mobile host, location privacy, end-host and initial reachability of a mobile host, location privacy, simultaneous
site multihoming with legacy hosts, simultaneous mobility of both mobility of both hosts, and some modes of NAT traversal. In these
hosts, and NAT traversal. In these situations there is a need for situations there is a need for some helper functionality in the
some helper functionality in the network, such as a HIP Rendezvous network, such as a HIP Rendezvous server [3]. Such functionality is
server [3]. Such functionality is out of scope of this document. out of scope of this document. We also do not consider localized
Finally, making underlying IP mobility transparent to the transport mobility management extensions; this document is concerned with end-
layer has implications on the proper response of transport congestion to-end mobility. Finally, making underlying IP mobility transparent
control, path MTU selection, and QoS. Transport-layer mobility to the transport layer has implications on the proper response of
triggers, and the proper transport response to a HIP mobility or transport congestion control, path MTU selection, and QoS.
multihoming address change, are outside the scope of this document. Transport-layer mobility triggers, and the proper transport response
to a HIP mobility or multihoming address change, are outside the
scope of this document.
2. Terminology and Conventions 2. Terminology and Conventions
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC2119 [6]. document are to be interpreted as described in RFC2119 [6].
Locator. A name that controls how the packet is routed through the Locator. A name that controls how the packet is routed through the
network and demultiplexed by the end host. It may include a network and demultiplexed by the end host. It may include a
concatenation of traditional network addresses such as an IPv6 concatenation of traditional network addresses such as an IPv6
skipping to change at page 5, line 29 skipping to change at page 6, line 29
The two most common examples are an IPv4 address and an IPv6 The two most common examples are an IPv4 address and an IPv6
address. The set of possible addresses is a subset of the set of address. The set of possible addresses is a subset of the set of
possible locators. possible locators.
Preferred locator. A locator on which a host prefers to receive data. Preferred locator. A locator on which a host prefers to receive data.
With respect to a given peer, a host always has one active With respect to a given peer, a host always has one active
preferred locator, unless there are no active locators. By preferred locator, unless there are no active locators. By
default, the locators used in the HIP base exchange are the default, the locators used in the HIP base exchange are the
preferred locators. preferred locators.
Credit Based Authorization. A host must must verify a mobile or Credit Based Authorization. A host must verify a mobile or multi-
multi-homed peer's reachability at a new locator. Credit-Based homed peer's reachability at a new locator. Credit-Based
Authorization authorizes the peer to receive a certain amount of Authorization authorizes the peer to receive a certain amount of
data at the new locator before the result of such verification is data at the new locator before the result of such verification is
known. known.
3. Protocol Model 3. Protocol Model
3.1 Operating Environment 3.1. Operating Environment
The Host Identity Protocol (HIP) [2] is a key establishment and The Host Identity Protocol (HIP) [2] is a key establishment and
parameter negotiation protocol. Its primary applications are for parameter negotiation protocol. Its primary applications are for
authenticating host messages based on host identities, and authenticating host messages based on host identities, and
establishing security associations (SAs) for ESP transport format [5] establishing security associations (SAs) for ESP transport format [5]
and possibly other protocols in the future. and possibly other protocols in the future.
+--------------------+ +--------------------+ +--------------------+ +--------------------+
| | | | | | | |
| +------------+ | | +------------+ | | +------------+ | | +------------+ |
skipping to change at page 6, line 40 skipping to change at page 7, line 40
| | | | | | | |
| | | | | | | |
| Initiator | | Responder | | Initiator | | Responder |
+--------------------+ +--------------------+ +--------------------+ +--------------------+
Figure 1: HIP deployment model Figure 1: HIP deployment model
The general deployment model for HIP is shown above, assuming The general deployment model for HIP is shown above, assuming
operation in an end-to-end fashion. This document specifies operation in an end-to-end fashion. This document specifies
extensions to the HIP protocol to enable end-host mobility and extensions to the HIP protocol to enable end-host mobility and
multihoming. In a nutshell, the HIP protocol can carry new multihoming. In summary, these extensions to the HIP protocol can
addressing information to the peer and can enable direct carry new addressing information to the peer and can enable direct
authentication of the message via a signature based on its host authentication of the message via a signature or keyed hash message
identity. This document specifies the format of this new addressing authentication code (HMAC) based on its host identity. This document
(LOCATOR) parameter, the procedures for sending and processing this specifies the format of this new addressing (LOCATOR) parameter, the
parameter to enable basic host mobility, and procedures for a procedures for sending and processing this parameter to enable basic
concurrent address verification mechanism. host mobility, and procedures for a concurrent address verification
mechanism.
3.1.1 Locator ---------
| TCP | (sockets bound to HITs)
---------
|
---------
----> | ESP | {HIT_s, HIT_d} <-> SPI
| ---------
| |
---- ---------
| MH |-> | HIP | {HIT_s, HIT_d, SPI} <-> {IP_s, IP_d, SPI}
---- ---------
|
---------
| IP |
---------
Figure 2: Architecture for HIP mobility and multihoming
Figure 2 depicts a layered architectural view of a HIP-enabled stack
using ESP transport format. In HIP, upper-layer protocols (including
TCP and ESP in this figure) are bound to HITs and not IP addresses.
The HIP sublayer is responsible for maintaining the binding between
HITs and IP addresses. The SPI (or other context tag if ESP is not
used with HIP), and not necessarily the IP addresses, is used to
associate an incoming packet with the right HITs. The block labeled
"MH" is introduced below.
Consider first the case in which there is no mobility or multihoming,
as specified in the base protocol specification [2]. The HIP base
exchange establishes the HITs in use between the hosts, the SPIs to
use for ESP, and the IP addresses (used in the HIP signaling
packets). Note that there can only be one such binding in the
outbound direction for any given packet, and the only selectors for
the binding at the HIP layer are the fields exposed by ESP (the SPI
and HITs). For the inbound direction, the SPI is all that is
required to find the right host context. ESP rekeying events change
the mapping between the HIT pair and SPI, but do not change the IP
addresses.
Consider next a mobility event, in which a host is still single-homed
but moves to another IP address. Two things must occur in this case.
First, the peer must be notified of the address change using a HIP
UPDATE message. Second, each host must change its local bindings at
the HIP sublayer (new IP addresses). It may be that both the SPIs
and IP addresses are changed simultaneously in a single UPDATE; the
protocol described herein supports this. This document specifies the
messaging and elements of procedure for such a mobility event.
However, simultaneous movement of both hosts, notification of
transport layer protocols of the path change, and procedures for
possibly traversing middleboxes are not covered by this document.
Finally, consider the case when a host is multihomed (has more than
one globally routable address) and wants to make these multiple
addresses available for use by the upper layer protocols, for fault
tolerance. Examples include the use of (possibly multiple) IPv4 and
IPv6 addresses on the same interface, or the use of multiple
interfaces attached to different service providers. Such host
multihoming generally necessitates that a separate ESP SA is
maintained for each interface in order to prevent packets that arrive
over different paths from falling outside of the ESP replay
protection window. Multihoming thus makes possible that the bindings
shown on the right side of Figure 2 are one to many (in the outbound
direction, one HIT pair to multiple SPIs, and possibly then to
multiple IP addresses). However, only one SPI and address can be
used for any given packet, so the job of the "MH" block depicted
above is to dynamically manipulate these bindings. Beyond locally
managing such multiple bindings, the peer-to-peer HIP signaling
protocol needs to be flexible enough to define the desired mappings
between HITs, SPIs, and addresses, and needs to ensure that UPDATE
messages are sent along the right network paths so that any HIP-aware
middleboxes can observe the SPIs. This document does not specify the
"MH" block, nor does it specify detailed elements of procedure for
how to handle various multihoming (perhaps combined with mobility)
scenarios. However, this document does describe a basic multihoming
case (one host adds one address to its initial address and notifies
the peer) and leave more complicated scenarios for experimentation
and future documents.
3.1.1. Locator
This document defines a generalization of an address called a This document defines a generalization of an address called a
"locator". A locator specifies a point-of-attachment to the network "locator". A locator specifies a point-of-attachment to the network
but may also include additional end-to-end tunneling or per-host but may also include additional end-to-end tunneling or per-host
demultiplexing context that affects how packets are handled below the demultiplexing context that affects how packets are handled below the
logical HIP sublayer of the stack. This generalization is useful logical HIP sublayer of the stack. This generalization is useful
because IP addresses alone may not be sufficient to describe how because IP addresses alone may not be sufficient to describe how
packets should be handled below HIP. For example, in a host packets should be handled below HIP. For example, in a host
multihoming context, certain IP addresses may need to be associated multihoming context, certain IP addresses may need to be associated
with certain ESP SPIs, to avoid violation of the ESP anti-replay with certain ESP SPIs, to avoid violation of the ESP anti-replay
window [4]. Addresses may also be affiliated with transport ports in window [4]. Addresses may also be affiliated with transport ports in
certain tunneling scenarios. Or locators may merely be traditional certain tunneling scenarios. Or locators may merely be traditional
network addresses. network addresses. In Section 4, a generalized HIP LOCATOR parameter
is defined that can contain one or more locators (addresses).
3.1.2 Mobility 3.1.2. Mobility overview
When a host moves to another address, it notifies its peer of the new When a host moves to another address, it notifies its peer of the new
address by sending a HIP UPDATE packet containing a LOCATOR address by sending a HIP UPDATE packet containing a LOCATOR
parameter. This UPDATE packet is acknowledged by the peer, and is parameter. This UPDATE packet is acknowledged by the peer, and is
protected by retransmission. The peer can authenticate the contents protected by retransmission. The peer can authenticate the contents
of the UPDATE packet based on the signature and keyed hash of the of the UPDATE packet based on the signature and keyed hash of the
packet. The host may at the same time decide to rekey its security packet.
association and possibly generate a new Diffie-Hellman key; all of
these actions are triggered by including additional parameters in the
UPDATE packet, as defined in the base protocol specification [2].
When using ESP Transport Format [5], the host is able to receive When using ESP Transport Format [5], the host may at the same time
packets that are protected using a HIP created ESP SA from any decide to rekey its security association and possibly generate a new
address. Thus, a host can change its IP address and continue to send Diffie-Hellman key; all of these actions are triggered by including
packets to its peers. However, the peers are not able to reply additional parameters in the UPDATE packet, as defined in the base
before they can reliably and securely update the set of addresses protocol specification [2] and ESP extension [5].
that they associate with the sending host. Furthermore, mobility may
change the path characteristics in such a manner that reordering
occurs and packets fall outside the ESP anti-replay window.
3.1.3 Multihoming When using ESP (and possibly other transport modes in the future),
the host is able to receive packets that are protected using a HIP
created ESP SA from any address. Thus, a host can change its IP
address and continue to send packets to its peers without necessarily
rekeying. However, the peers are not able to reply before they can
reliably and securely update the set of addresses that they associate
with the sending host. Furthermore, mobility may change the path
characteristics in such a manner that reordering occurs and packets
fall outside the ESP anti-replay window for the SA, thereby requiring
rekeying.
3.1.3. Multihoming overview
A related operational configuration is host multihoming, in which a A related operational configuration is host multihoming, in which a
host has multiple locators simultaneously rather than sequentially as host has multiple locators simultaneously rather than sequentially as
in the case of mobility. By using the locator parameter defined in the case of mobility. By using the LOCATOR parameter defined
herein, a host can inform its peers of additional (multiple) locators herein, a host can inform its peers of additional (multiple) locators
at which it can be reached, and can declare a particular locator as a at which it can be reached, and can declare a particular locator as a
"preferred" locator. Although this document defines a mechanism for "preferred" locator. Although this document defines a mechanism for
multihoming, it does not define associated policies and procedure multihoming, it does not define detailed policies and procedures such
details such as which locators to choose when more than one pair is as which locators to choose when more than one pair is available, the
available, the operation of simultaneous mobility and multihoming, operation of simultaneous mobility and multihoming, and the
and the implications of multihoming on transport protocols and ESP implications of multihoming on transport protocols and ESP anti-
anti-replay windows. Additional definition of HIP-based multihoming replay windows. Additional definition of HIP-based multihoming is
is expected to be part of a future document. expected to be part of future documents.
3.2 Protocol Overview 3.2. Protocol Overview
In this section we briefly introduce a number of usage scenarios In this section we briefly introduce a number of usage scenarios for
where the HIP mobility and multihoming facility is useful. These HIP mobility and multihoming. These scenarios assume that HIP is
scenarios assume that HIP is being used with the ESP Transform, being used with the ESP transform [5], although other scenarios may
although other scenarios may be defined in the future. To understand be defined in the future. To understand these usage scenarios, the
these usage scenarios, the reader should be at least minimally reader should be at least minimally familiar with the HIP protocol
familiar with the HIP protocol specification [2]. However, for the specification [2]. However, for the (relatively) uninitiated reader
(relatively) uninitiated reader it is most important to keep in mind it is most important to keep in mind that in HIP the actual payload
that in HIP the actual payload traffic is protected with ESP, and traffic is protected with ESP, and that the ESP SPI acts as an index
that the ESP SPI acts as an index to the right host-to-host context. to the right host-to-host context.
Each of the scenarios below assumes that the HIP base exchange has Each of the scenarios below assumes that the HIP base exchange has
completed, and the hosts each have a single outbound SA to the peer completed, and the hosts each have a single outbound SA to the peer
host. Associated with this outbound SA is a single destination host. Associated with this outbound SA is a single destination
address of the peer host-- the source address used by the peer during address of the peer host-- the source address used by the peer during
the base exchange. the base exchange.
The readdressing protocol is an asymmetric protocol where one host, The readdressing protocol is an asymmetric protocol where a mobile or
called the mobile host, informs another host, called the peer host, multihomed host informs a peer host about changes of IP addresses on
about changes of IP addresses on affected SPIs. The readdressing affected SPIs. The readdressing exchange is designed to be
exchange is designed to be piggybacked on existing HIP exchanges. piggybacked on existing HIP exchanges. The main packets on which the
The main packets on which the LOCATOR parameters are expected to be LOCATOR parameters are expected to be carried are UPDATE packets.
carried are UPDATE packets. However, some implementations may want However, some implementations may want to experiment with sending
to experiment with sending LOCATOR parameters also on other packets, LOCATOR parameters also on other packets, such as R1, I2, and NOTIFY.
such as R1, I2, and NOTIFY.
3.2.1 Mobility with single SA pair Hosts that use link-local addresses as source addresses in their HIP
handshakes may not be reachable by a mobile peer. Such hosts SHOULD
provide a globally routable address either in the initial handshake
or via the LOCATOR parameter.
3.2.1. Mobility with single SA pair (no rekeying)
A mobile host must sometimes change an IP address bound to an A mobile host must sometimes change an IP address bound to an
interface. The change of an IP address might be needed due to a interface. The change of an IP address might be needed due to a
change in the advertised IPv6 prefixes on the link, a reconnected PPP change in the advertised IPv6 prefixes on the link, a reconnected PPP
link, a new DHCP lease, or an actual movement to another subnet. In link, a new DHCP lease, or an actual movement to another subnet. In
order to maintain its communication context, the host must inform its order to maintain its communication context, the host must inform its
peers about the new IP address. This first example considers the peers about the new IP address. This first example considers the
case in which the mobile host has only one interface, IP address, and case in which the mobile host has only one interface, IP address, a
a single pair of SAs (one inbound, one outbound). single pair of SAs (one inbound, one outbound), and no rekeying
occurs on the SAs. We also assume that the new IP addresses are
1. The mobile host is disconnected from the peer host for a brief within the same address family (IPv4 or IPv6) as the first address.
period of time while it switches from one IP address to another. This is the simplest scenario, depicted in Figure 3.
Upon obtaining a new IP address, the mobile host sends a LOCATOR
parameter to the peer host in an UPDATE message. The LOCATOR
indicates the new IP address and the SPI associated with the new
IP address by using a Locator Type of "1", the locator lifetime,
and whether the new locator is a preferred locator. The mobile
host may optionally send an ESP_INFO to create a new inbound SA,
in which case it transitions to state REKEYING. In this case,
the Locator contains the new SPI to use. Otherwise, the existing
SPI is identified in the Locator parameter, and the host waits
for its UPDATE to be acknowledged.
2. Depending on whether the mobile host initiated a rekey, and on
whether the peer host itself wants to rekey, a number of
responses are possible. Figure 2 illustrates an exchange for
which neither side initiates a rekeying, but for which the peer
host performs an address check. If the mobile host is rekeying,
the peer will also rekey, as shown in Figure 3. If the mobile
host did not decide to rekey but the peer desires to do so, then
it initiates a rekey as illustrated in Figure 4. The UPDATE
messages sent from the peer back to the mobile are sent to the
newly advertised address.
3. While the peer host is verifying the new address, the address is
marked as UNVERIFIED in the interim. Once it has received a
correct reply to its UPDATE challenge, or optionally, data on the
new SA, it marks the new address as ACTIVE and removes the old
address.
Mobile Host Peer Host Mobile Host Peer Host
UPDATE(ESP_INFO, LOC, SEQ) UPDATE(ESP_INFO, LOCATOR, SEQ)
-----------------------------------> ----------------------------------->
UPDATE(ESP_INFO, SEQ, ACK, ECHO_REQUEST) UPDATE(ESP_INFO, SEQ, ACK, ECHO_REQUEST)
<----------------------------------- <-----------------------------------
UPDATE(ACK, ECHO_RESPONSE) UPDATE(ACK, ECHO_RESPONSE)
-----------------------------------> ----------------------------------->
Figure 2: Readdress without rekeying, but with address check Figure 3: Readdress without rekeying, but with address check
1. The mobile host is disconnected from the peer host for a brief
period of time while it switches from one IP address to another.
Upon obtaining a new IP address, the mobile host sends a LOCATOR
parameter to the peer host in an UPDATE message. The UPDATE
message also contains an ESP_INFO parameter with the "Old SPI"
and "New SPI" parameters both set to the value of the pre-
existing incoming SPI; this ESP_INFO does not trigger a rekeying
event but is instead included for possible parameter-inspecting
middleboxes on the path. The LOCATOR parameter contains the new
IP address (Locator Type of "1", defined below) and a locator
lifetime. The mobile host waits for this UPDATE to be
acknowledged, and retransmits if necessary, as specified in the
base specification [2].
2. The peer host receives the UPDATE, validates it, and updates any
local bindings between the HIP association and the mobile host's
destination address. The peer host MUST perform an address
verification by placing a nonce in the ECHO_REQUEST parameter of
hte UPDATE message sent back to the mobile host. It also
includes an ESP_INFO parameter with the "Old SPI" and "New SPI"
parameters both set to the value of the pre-existing incoming
SPI, and sends this UPDATE (with piggybacked acknowledgment) to
the mobile host at its new address. The peer MAY use the new
address immediately, but it MUST limit the amount of data it
sends to the address until address verification completes.
3. The mobile host completes the readdress by processing the UPDATE
ACK and echoing the nonce in an ECHO_RESPONSE. Once the peer
host receives this ECHO_RESPONSE, it considers the new address to
be verified and can put it into full use.
While the peer host is verifying the new address, the new address is
marked as UNVERIFIED in the interim, and the old address is
DEPRECATED. Once the peer host has received a correct reply to its
UPDATE challenge, it marks the new address as ACTIVE and removes the
old address.
3.2.1.1. Mobility with single SA pair (mobile-initiated rekey)
The mobile host may decide to rekey the SAs at the same time that it
is notifying the peer of the new address. In this case, the above
procedure described in Figure 3 is slightly modified. The UPDATE
message sent from the mobile host includes an ESP_INFO with the "Old
SPI" set to the previous SPI, the "New SPI" set to the desired new
SPI value for the incoming SA, and the Keymat Index desired.
Optionally, the host may include a DIFFIE_HELLMAN parameter for a new
Diffie-Hellman key. The peer completes the request for rekey as is
normally done for HIP rekeying, except that the new address is kept
as UNVERIFIED until the UPDATE nonce challenge is received as
described above. Figure 4 illustrates this scenario.
Mobile Host Peer Host Mobile Host Peer Host
UPDATE(ESP_INFO, LOC, SEQ, [DIFFIE_HELLMAN]) UPDATE(ESP_INFO, LOCATOR, SEQ, [DIFFIE_HELLMAN])
-----------------------------------> ----------------------------------->
UPDATE(ESP_INFO, SEQ, ACK, [DIFFIE_HELLMAN,] ECHO_REQUEST) UPDATE(ESP_INFO, SEQ, ACK, [DIFFIE_HELLMAN,] ECHO_REQUEST)
<----------------------------------- <-----------------------------------
UPDATE(ACK, ECHO_RESPONSE) UPDATE(ACK, ECHO_RESPONSE)
-----------------------------------> ----------------------------------->
Figure 3: Readdress with mobile-initiated rekey Figure 4: Readdress with mobile-initiated rekey
3.2.1.2. Mobility with single SA pair (peer-initiated rekey)
A second variation of this basic mobility scenario covers the case in
which the mobile host does not attempt to rekey the existing SAs, but
the peer host decides to do so. This typically results in a four
packet exchange, as shown in Figure 5. The initial UPDATE packet
from the mobile host is the same as in the scenario for which there
is no rekey (Figure 3). The peer may decide to rekey, however, in
which case the subsequent three packets follow the normal rekeying
procedure described in the ESP specification [5], with the addition
of the ECHO_REQUEST and ECHO_RESPONSE nonce for verification of the
new address.
Mobile Host Peer Host Mobile Host Peer Host
UPDATE(LOC, SEQ) UPDATE(ESP_INFO, LOCATOR, SEQ)
-----------------------------------> ----------------------------------->
UPDATE(ESP_INFO, SEQ, ACK, [DIFFIE_HELLMAN], ECHO_REQUEST) UPDATE(ESP_INFO, SEQ, ACK, [DIFFIE_HELLMAN], ECHO_REQUEST)
<----------------------------------- <-----------------------------------
UPDATE(ESP_INFO, SEQ, ACK, [DIFFIE_HELLMAN,] ECHO_RESPONSE) UPDATE(ESP_INFO, SEQ, ACK, [DIFFIE_HELLMAN,] ECHO_RESPONSE)
-----------------------------------> ----------------------------------->
UPDATE(ACK) UPDATE(ACK)
<----------------------------------- <-----------------------------------
Figure 4: Readdress with peer-initiated rekey Figure 5: Readdress with peer-initiated rekey
Hosts that use link-local addresses as source addresses in their HIP
handshakes may not be reachable by a mobile peer. Such hosts SHOULD
provide a globally routable address either in the initial handshake
or via the LOCATOR parameter.
3.2.2 Host multihoming 3.2.2. Host multihoming
A (mobile or stationary) host may sometimes have more than one A (mobile or stationary) host may sometimes have more than one
interface. The host may notify the peer host of the additional interface or global address. The host may notify the peer host of
interface(s) by using the LOCATOR parameter. To avoid problems with the additional interface or address by using the LOCATOR parameter.
the ESP anti-replay window, a host SHOULD use a different SA for each To avoid problems with the ESP anti-replay window, a host SHOULD use
interface used to receive packets from the peer host. a different SA for each interface or address used to receive packets
from the peer host.
When more than one locator is provided to the peer host, the host When more than one locator is provided to the peer host, the host
SHOULD indicate which locator is preferred. By default, the SHOULD indicate which locator is preferred. By default, the
addresses used in the base exchange are preferred until indicated addresses used in the base exchange are preferred until indicated
otherwise. otherwise.
Although the protocol may allow for configurations in which there is Although the protocol may allow for configurations in which there is
an asymmetric number of SAs between the hosts (e.g., one host has two an asymmetric number of SAs between the hosts (e.g., one host has two
interfaces and two inbound SAs, while the peer has one interface and interfaces and two inbound SAs, while the peer has one interface and
one inbound SA), it is RECOMMENDED that inbound and outbound SAs be one inbound SA), it is RECOMMENDED that inbound and outbound SAs be
created pairwise between hosts. When an ESP_INFO arrives to rekey a created pairwise between hosts. When an ESP_INFO arrives to rekey a
particular outbound SA, the corresponding inbound SA should be also particular outbound SA, the corresponding inbound SA should be also
rekeyed at that time. Although asymmetric SA configurations might be rekeyed at that time. Although asymmetric SA configurations might be
experimented with, their usage may constrain interoperability at this experimented with, their usage may constrain interoperability at this
time. However, it is recommended that implementations attempt to time. However, it is recommended that implementations attempt to
support peers that prefer to use non-paired SAs. It is expected that support peers that prefer to use non-paired SAs. It is expected that
this section and behavior will be modified in future revisions of this section and behavior will be modified in future revisions of
this protocol, once the issue and its implications are better this protocol, once the issue and its implications are better
understood. understood.
To add both an additional interface and SA, the host sends a LOCATOR Consider the case between two single-homed hosts, in which one of the
with an ESP_INFO. The host uses the same (new) SPI value in the host notifies the peer of an additional address. It is RECOMMENDED
LOCATOR and both the "Old SPI" and "New SPI" values in the ESP_INFO-- that the host set up a new SA pair for use on this new address. To
this indicates to the peer that the SPI is not replacing an existing do this, the multihomed host sends a LOCATOR with an ESP_INFO,
SPI. The multihomed host transitions to state REKEYING, waiting for indicating the request for a new SA by setting the "Old SPI" value to
a ESP_INFO from the peer and an ACK of its own UPDATE. As in the zero, and the "New SPI" value to the newly created incoming SPI. A
mobility case, the peer host must perform an address check while it Locator Type of "1" is used to associate the new address with the new
is rekeying. Figure 5 illustrates the basic packet exchange. SPI. The LOCATOR parameter also contains a second Type 1 locator:
that of the original address and SPI. To simplify parameter
processing and avoid explicit protocol extensions to remove locators,
each LOCATOR parameter must list all locators in use on a connection
(a complete listing of inbound locators and SPIs for the host). The
multihomed host transitions to state REKEYING, waiting for a ESP_INFO
(new outbound SA) from the peer and an ACK of its own UPDATE. As in
the mobility case, the peer host must perform an address verification
before putting the new address into active use. Figure 6 illustrates
the basic packet exchange.
Multi-homed Host Peer Host Multi-homed Host Peer Host
UPDATE(ESP_INFO, LOC, SEQ, [DIFFIE_HELLMAN]) UPDATE(ESP_INFO, LOCATOR, SEQ, [DIFFIE_HELLMAN])
-----------------------------------> ----------------------------------->
UPDATE(ESP_INFO, SEQ, ACK, [DIFFIE_HELLMAN,] ECHO_REQUEST) UPDATE(ESP_INFO, SEQ, ACK, [DIFFIE_HELLMAN,] ECHO_REQUEST)
<----------------------------------- <-----------------------------------
UPDATE(ACK, ECHO_RESPONSE) UPDATE(ACK, ECHO_RESPONSE)
-----------------------------------> ----------------------------------->
Figure 5: Basic multihoming scenario Figure 6: Basic multihoming scenario
For the case in which multiple locators are advertised in a LOCATOR,
the peer does not need to send ACK for the UPDATE(LOCATOR) in every
subsequent message used for the address check procedure of the
multiple locators. Therefore, a sample packet exchange might look as
shown in Figure 6.
Multi-homed Host Peer Host
UPDATE(LOC(addr_1,addr_2), SEQ)
----------------------------------->
UPDATE(ACK)
<-----------------------------------
sent to addr_1:UPDATE(ESP_INFO, SEQ, ECHO_REQUEST)
<-----------------------------------
UPDATE(ACK, ECHO_RESPONSE)
----------------------------------->
sent to addr_2:UPDATE(ESP_INFO, SEQ, ECHO_REQUEST)
<-----------------------------------
UPDATE(ACK, ECHO_RESPONSE)
----------------------------------->
Figure 6: LOCATOR with multiple addresses
When processing inbound LOCATORs that establish new security When processing inbound LOCATORs that establish new security
associations, a host uses the destination address of the UPDATE associations on an interface with multiple addresses, a host uses the
containing LOCATOR as the local address to which the LOC plus destination address of the UPDATE containing LOCATOR as the local
ESP_INFO is targeted. Hosts may send LOCATOR with the same IP address to which the LOCATOR plus ESP_INFO is targeted. Hosts may
address to different peer addresses-- this has the effect of creating send UPDATEs with the same IP address in the LOCATOR to different
multiple inbound SAs implicitly affiliated with different source peer addresses-- this has the effect of creating multiple inbound SAs
addresses. implicitly affiliated with different peer source addresses.
When rekeying in a multihoming situation in which there is an
asymmetric number of SAs between two hosts, a respondent to the
ESP_INFO/UPDATE procedure may have some ambiguity as to which inbound
SA it should update in response to the peer's UPDATE. In such a
case, the host SHOULD choose an SA corresponding to the inbound
interface on which the UPDATE was received.
3.2.3 Site multihoming 3.2.3. Site multihoming
A host may have an interface that has multiple globally reachable IP A host may have an interface that has multiple globally reachable IP
addresses. Such a situation may be a result of the site having addresses. Such a situation may be a result of the site having
multiple upper Internet Service Providers, or just because the site multiple upper Internet Service Providers, or just because the site
provides all hosts with both IPv4 and IPv6 addresses. It is provides all hosts with both IPv4 and IPv6 addresses. It is
desirable that the host can stay reachable with all or any subset of desirable that the host can stay reachable with all or any subset of
the currently available globally routable addresses, independent on the currently available globally routable addresses, independent on
how they are provided. how they are provided.
This case is handled the same as if there were different IP This case is handled the same as if there were different IP
addresses, described above in Section 3.2.2. Note that a single addresses, described above in Section 3.2.2. Note that a single
interface may experience site multihoming while the host itself may interface may experience site multihoming while the host itself may
have multiple interfaces. have multiple interfaces.
Note that a host may be multi-homed and mobile simultaneously, and Note that a host may be multi-homed and mobile simultaneously, and
that a multi-homed host may want to protect the location of some of that a multi-homed host may want to protect the location of some of
its interfaces while revealing the real IP address of some others. its interfaces while revealing the real IP address of some others.
This document does not presently specify additional site multihoming This document does not presently specify additional site multihoming
extensions to HIP to further align it with the requirements of the extensions to HIP; further alignment with the IETF shim6 working
multi6 working group. group may be considered in the future.
3.2.4 Dual host multihoming 3.2.4. Dual host multihoming
Consider the case in which both hosts would like to add an additional Consider the case in which both hosts would like to add an additional
address after the base exchange completes. In Figure 7, consider address after the base exchange completes. In Figure 7, consider
that host1 wants to add address addr1b. It would send a LOCATOR to that host1 wants to add address addr1b. It would send an UPDATE with
host2 located at addr2a, and a new set of SPIs would be added between LOCATOR to host2 located at addr2a, and a new set of SPIs would be
hosts 1 and 2 (call them SPI1b and SPI2b). Next, consider host2 added between hosts 1 and 2 (call them SPI1b and SPI2b). Next,
deciding to add addr2b to the relationship. host2 now has a choice of consider host2 deciding to add addr2b to the relationship. host2 now
which of host1's addresses to initiate LOCATOR to. It may choose to has a choice to which of host1's addresses to initiate an UPDATE. It
initiate a LOCATOR to addr1a, addr1b, or both. If it chooses to send may choose to initiate an UPDATE to addr1a, addr1b, or both. If it
to both, then a full mesh (four SA pairs) of SAs would exist between chooses to send to both, then a full mesh (four SA pairs) of SAs
the two hosts. This is the most general case; it may be often the would exist between the two hosts. This is the most general case; it
case that hosts primarily establish new SAs only with the peer's often may be the case that hosts primarily establish new SAs only
preferred locator. The readdressing protocol is flexible enough to with the peer's preferred locator. The readdressing protocol is
accommodate this choice. flexible enough to accommodate this choice.
-<- SPI1a -- -- SPI2a ->- -<- SPI1a -- -- SPI2a ->-
host1 < > addr1a <---> addr2a < > host2 host1 < > addr1a <---> addr2a < > host2
->- SPI2a -- -- SPI1a -<- ->- SPI2a -- -- SPI1a -<-
addr1b <---> addr2b addr1b <---> addr2a (second SA pair)
addr1a <---> addr2b (third SA pair)
addr1b <---> addr2b (fourth SA pair)
Figure 7: Dual multihoming case in which each host uses LOCATOR to Figure 7: Dual multihoming case in which each host uses LOCATOR to
add a second address add a second address
3.2.5 Combined mobility and multihoming 3.2.5. Combined mobility and multihoming
It looks likely that in the future many mobile hosts will be It looks likely that in the future many mobile hosts will be
simultaneously mobile and multi-homed, i.e., have multiple mobile simultaneously mobile and multi-homed, i.e., have multiple mobile
interfaces. Furthermore, if the interfaces use different access interfaces. Furthermore, if the interfaces use different access
technologies, it is fairly likely that one of the interfaces may technologies, it is fairly likely that one of the interfaces may
appear stable (retain its current IP address) while some other(s) may appear stable (retain its current IP address) while some other(s) may
experience mobility (undergo IP address change). experience mobility (undergo IP address change).
The use of LOCATOR plus ESP_INFO should be flexible enough to handle The use of LOCATOR plus ESP_INFO should be flexible enough to handle
most such scenarios, although more complicated scenarios have not most such scenarios, although more complicated scenarios have not
been studied so far. been studied so far.
3.2.6 Using LOCATORs across addressing realms 3.2.6. Using LOCATORs across addressing realms
It is possible for HIP associations to migrate to a state in which It is possible for HIP associations to migrate to a state in which
both parties are only using locators in different addressing realms. both parties are only using locators in different addressing realms.
For example, the two hosts may initiate the HIP association when both For example, the two hosts may initiate the HIP association when both
are using IPv6 locators, then one host may loose its IPv6 are using IPv6 locators, then one host may loose its IPv6
connectivity and obtain an IPv4 address. In such a case, some type connectivity and obtain an IPv4 address. In such a case, some type
of mechanism for interworking between the different realms must be of mechanism for interworking between the different realms must be
employed; such techniques are outside the scope of the present text. employed; such techniques are outside the scope of the present text.
If no mechanism exists, then the UPDATE message carrying the new If no mechanism exists, then the UPDATE message carrying the new
LOCATOR will likely not be acknowledged anyway, and the HIP state may LOCATOR will likely not reach the destination anyway, and the HIP
time out. state may time out.
3.2.7 Network renumbering 3.2.7. Network renumbering
It is expected that IPv6 networks will be renumbered much more often It is expected that IPv6 networks will be renumbered much more often
than most IPv4 networks are. From an end-host point of view, network than most IPv4 networks are. From an end-host point of view, network
renumbering is similar to mobility. renumbering is similar to mobility.
3.2.8 Initiating the protocol in R1 or I2 3.2.8. Initiating the protocol in R1 or I2
A Responder host MAY include one or more LOCATOR parameters in the R1 A Responder host MAY include one or more LOCATOR parameters in the R1
packet that it sends to the Initiator. These parameters MUST be packet that it sends to the Initiator. These parameters MUST be
protected by the R1 signature. If the R1 packet contains LOCATOR protected by the R1 signature. If the R1 packet contains LOCATOR
parameters with a new preferred locator, the Initiator SHOULD parameters with a new preferred locator, the Initiator SHOULD
directly set the new preferred locator to status ACTIVE without directly set the new preferred locator to status ACTIVE without
performing address verification first, and MUST send the I2 packet to performing address verification first, and MUST send the I2 packet to
the new preferred locator. The I1 destination address and the new the new preferred locator. The I1 destination address and the new
preferred locator may be identical. All new non-preferred locators preferred locator may be identical. All new non-preferred locators
must still undergo address verification. must still undergo address verification.
Initiator Responder Initiator Responder
R1 with LOCATOR R1 with LOCATOR
<----------------------------------- <-----------------------------------
record additional addresses record additional addresses
change responder address change responder address
I2 with new SPI in ESP_INFO parameter I2 sent to newly indicated preferred address
-----------------------------------> ----------------------------------->
(process normally) (process normally)
R2 R2
<----------------------------------- <-----------------------------------
(process normally) (process normally, later verification of non-preferred locators)
Figure 8: LOCATOR inclusion in R1 Figure 8: LOCATOR inclusion in R1
An Initiator MAY include one or more LOCATOR parameters in the I2 An Initiator MAY include one or more LOCATOR parameters in the I2
packet, independent on whether there was LOCATOR parameter(s) in the packet, independent of whether there was a LOCATOR parameter in the
R1 or not. These parameters MUST be protected by the I2 signature. R1 or not. These parameters MUST be protected by the I2 signature.
Even if the I2 packet contains LOCATOR parameters, the Responder MUST Even if the I2 packet contains LOCATOR parameters, the Responder MUST
still send the R2 packet to the source address of the I2. The new still send the R2 packet to the source address of the I2. The new
preferred locator SHOULD be identical to the I2 source address. If preferred locator SHOULD be identical to the I2 source address. If
the I2 packet contains LOCATOR parameters, all new locators must the I2 packet contains LOCATOR parameters, all new locators must
undergo address verification as usual. If any of these locators is a undergo address verification as usual.
new preferred locator, an efficient method to verify this is to
piggyback an ECHO_REQUEST parameter with some unguessable data to the
R2 packet.
Initiator Responder Initiator Responder
I2 with LOCATOR I2 with LOCATOR
-----------------------------------> ----------------------------------->
(process normally) (process normally)
record additional addresses record additional addresses
R2 with new SPI in ESP_INFO parameter R2 sent to source address of I2
<----------------------------------- <-----------------------------------
(process normally) (process normally)
data on new SA
------------------------------------>
(process normally)
Figure 9: LOCATOR inclusion in I2 Figure 9: LOCATOR inclusion in I2
3.3 Other Considerations 3.3. Other Considerations
3.3.1 Address Verification 3.3.1. Address Verification
When a HIP host receives a set of locators from another HIP host in a When a HIP host receives a set of locators from another HIP host in a
LOCATOR, it does not necessarily know whether the other host is LOCATOR, it does not necessarily know whether the other host is
actually reachable at the claimed addresses. In fact, a malicious actually reachable at the claimed addresses. In fact, a malicious
peer host may be intentionally giving bogus addresses in order to peer host may be intentionally giving bogus addresses in order to
cause a packet flood towards the target addresses [10]. Likewise, cause a packet flood towards the target addresses [8]. Likewise,
viral software may have compromised the peer host, programming it to viral software may have compromised the peer host, programming it to
redirect packets to the target addresses. Thus, the HIP host must redirect packets to the target addresses. Thus, the HIP host must
first check that the peer is reachable at the new address. first check that the peer is reachable at the new address.
An additional potential benefit of performing address verification is An additional potential benefit of performing address verification is
to allow middleboxes in the network along the new path to obtain the to allow middleboxes in the network along the new path to obtain the
peer host's inbound SPI. peer host's inbound SPI.
Address verification is implemented by the challenger sending some Address verification is implemented by the challenger sending some
piece of unguessable information to the new address, and waiting for piece of unguessable information to the new address, and waiting for
some acknowledgment from the responder that indicates reception of some acknowledgment from the responder that indicates reception of
the information at the new address. This may include exchange of a the information at the new address. This may include exchange of a
nonce, or generation of a new SPI and observing data arriving on the nonce, or generation of a new SPI and observing data arriving on the
new SPI. new SPI.
3.3.2 Credit-Based Authorization 3.3.2. Credit-Based Authorization
Credit-Based Authorization allows a host to securely use a new Credit-Based Authorization allows a host to securely use a new
locator even though the peer's reachability at the address embedded locator even though the peer's reachability at the address embedded
in this locator has not yet been verified. This is accomplished in this locator has not yet been verified. This is accomplished
based on the following three hypotheses: based on the following three hypotheses:
1. A flooding attacker typically seeks to somehow multiply the 1. A flooding attacker typically seeks to somehow multiply the
packets it generates itself for the purpose of its attack because packets it generates itself for the purpose of its attack because
bandwidth is an ample resource for many attractive victims. bandwidth is an ample resource for many attractive victims.
skipping to change at page 16, line 7 skipping to change at page 18, line 50
On this basis, rather than eliminating malicious packet redirection On this basis, rather than eliminating malicious packet redirection
in the first place, Credit-Based Authorization prevents any in the first place, Credit-Based Authorization prevents any
amplification that can be reached through it. This is accomplished amplification that can be reached through it. This is accomplished
by limiting the data a host can send to an unverified address of a by limiting the data a host can send to an unverified address of a
peer by the data recently received from that peer. Redirection-based peer by the data recently received from that peer. Redirection-based
flooding attacks thus become less attractive than, e.g., pure direct flooding attacks thus become less attractive than, e.g., pure direct
flooding, where the attacker itself sends bogus packets to the flooding, where the attacker itself sends bogus packets to the
victim. victim.
Figure 10 illustrates Credit-Based Authorization: Host B measures Figure 10 illustrates Credit-Based Authorization: Host B measures the
the bytes recently received from peer A and, when A readdresses, bytes recently received from peer A and, when A readdresses, sends
sends packets to A's new, unverified address as long as the sum of packets to A's new, unverified address as long as the sum of their
their sizes does not exceed the measured, received data volume. When sizes does not exceed the measured, received data volume. When
insufficient credit is left, B stops sending further packets to A insufficient credit is left, B stops sending further packets to A
until A's address becomes ACTIVE. The address changes may be due to until A's address becomes ACTIVE. The address changes may be due to
mobility, due to multihoming, or due to any other reason. mobility, due to multihoming, or due to any other reason.
+-------+ +-------+ +-------+ +-------+
| A | | B | | A | | B |
+-------+ +-------+ +-------+ +-------+
| | | |
address |------------------------->| credit += size(packet) address |------------------------->| credit += size(packet)
ACTIVE | | ACTIVE | |
skipping to change at page 16, line 39 skipping to change at page 19, line 34
|<-------------------------| credit -= size(packet) |<-------------------------| credit -= size(packet)
| X credit < size(packet)=> drop! | X credit < size(packet)=> drop!
| | | |
+ address change | + address change |
address | | address | |
ACTIVE |<-------------------------| don't change credit ACTIVE |<-------------------------| don't change credit
| | | |
Figure 10: Readdressing Scenario Figure 10: Readdressing Scenario
3.3.3 Preferred locator 3.3.3. Preferred locator
When a host has multiple locators, the peer host must decide upon When a host has multiple locators, the peer host must decide upon
which to use for outbound packets. It may be that a host would which to use for outbound packets. It may be that a host would
prefer to receive data on a particular inbound interface. HIP allows prefer to receive data on a particular inbound interface. HIP allows
a particular locator to be designated as a preferred locator, and a particular locator to be designated as a preferred locator, and
communicated to the peer (see Section 4). communicated to the peer (see Section 4).
In general, when multiple locators are used for a session, there is In general, when multiple locators are used for a session, there is
the question of using multiple locators for failover only or for the question of using multiple locators for failover only or for
load-balancing. Due to the implications of load-balancing on the load-balancing. Due to the implications of load-balancing on the
transport layer that still need to be worked out, this draft assumes transport layer that still need to be worked out, this draft assumes
that multiple locators are used primarily for failover. An that multiple locators are used primarily for failover. An
implementation may use ICMP interactions, reachability checks, or implementation may use ICMP interactions, reachability checks, or
other means to detect the failure of a locator. other means to detect the failure of a locator.
3.3.4 Interaction with Security Associations 3.3.4. Interaction with Security Associations
This document specifies a new HIP protocol parameter, the LOCATOR This document specifies a new HIP protocol parameter, the LOCATOR
parameter (see Section 4), that allows the hosts to exchange parameter (see Section 4), that allows the hosts to exchange
information about their locator(s), and any changes in their information about their locator(s), and any changes in their
locator(s). The logical structure created with LOCATOR parameters locator(s). The logical structure created with LOCATOR parameters
has three levels: hosts, Security Associations (SAs) indexed by has three levels: hosts, Security Associations (SAs) indexed by
Security Parameter Indices (SPIs), and addresses. Security Parameter Indices (SPIs), and addresses.
The relation between these entities for an association negotiated as The relation between these entities for an association negotiated as
defined in the base specification [2] and ESP transform [5] is defined in the base specification [2] and ESP transform [5] is
skipping to change at page 19, line 6 skipping to change at page 22, line 6
"affinity" for certain inbound IP addresses, and this affinity is "affinity" for certain inbound IP addresses, and this affinity is
communicated to the peer host. Each physical interface SHOULD have a communicated to the peer host. Each physical interface SHOULD have a
separate SA, unless the ESP anti-replay window is loose. separate SA, unless the ESP anti-replay window is loose.
Moreover, even if the destination addresses used for a particular SPI Moreover, even if the destination addresses used for a particular SPI
are held constant, the use of different source interfaces may also are held constant, the use of different source interfaces may also
cause packets to fall outside of the ESP anti-replay window, since cause packets to fall outside of the ESP anti-replay window, since
the path traversed is often affected by the source address or the path traversed is often affected by the source address or
interface used. A host has no way to influence the source interface interface used. A host has no way to influence the source interface
on which a peer uses to send its packets on a given SPI. Hosts on which a peer uses to send its packets on a given SPI. Hosts
SHOULD consistently use the same source interface when sending to a SHOULD consistently use the same source interface and address when
particular destination IP address and SPI. For this reason, a host sending to a particular destination IP address and SPI. For this
may find it useful to change its SPI or at least reset its ESP anti- reason, a host may find it useful to change its SPI or at least reset
replay window when the peer host readdresses. its ESP anti-replay window when the peer host readdresses.
An address may appear on more than one SPI. This creates no An address may appear on more than one SPI. This creates no
ambiguity since the receiver will ignore the IP addresses as SA ambiguity since the receiver will ignore the IP addresses as SA
selectors anyway. selectors anyway. However, this document does not specify such
cases.
A single LOCATOR parameter contains data only about one SPI. To
simultaneously signal changes on several SPIs, it is necessary to
send several LOCATOR parameters. The packet structure supports this.
If the LOCATOR parameter is sent in an UPDATE packet, then the If the LOCATOR parameter is sent in an UPDATE packet, then the
receiver will respond with an UPDATE acknowledgment. If the LOCATOR receiver will respond with an UPDATE acknowledgment. If the LOCATOR
parameter is sent in a NOTIFY, I2, or R2 packet, then the recipient parameter is sent in a NOTIFY, I2, or R2 packet, then the recipient
may consider the LOCATOR as informational, and act only when it needs may consider the LOCATOR as informational, and act only when it needs
to activate a new address. The use of LOCATOR in a NOTIFY message to activate a new address. The use of LOCATOR in a NOTIFY message
may not be compatible with middleboxes. may not be compatible with middleboxes.
4. LOCATOR parameter format 4. LOCATOR parameter format
The LOCATOR parameter is a critical parameter as defined by [2]. The The LOCATOR parameter is a critical parameter as defined by [2]. It
LOCATOR parameter is also abbreviated as "LOC" in the figures herein. consists of the standard HIP parameter Type and Length fields, plus
It consists of the standard HIP parameter Type and Length fields, one or more Locator sub-parameters. Each Locator sub-parameter
plus one or more Locator sub-parameters. Each Locator sub-parameter
contains a Traffic Type, Locator Type, Locator Length, Preferred contains a Traffic Type, Locator Type, Locator Length, Preferred
Locator bit, Locator Lifetime, and a Locator encoding. Locator bit, Locator Lifetime, and a Locator encoding.
0 1 2 3 0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length | | Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Traffic Type | Locator Type | Locator Length | Reserved |P| | Traffic Type | Locator Type | Locator Length | Reserved |P|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
skipping to change at page 21, line 30 skipping to change at page 24, line 28
multiples of four bytes in length. multiples of four bytes in length.
The Locator Lifetime indicates how long the following locator is The Locator Lifetime indicates how long the following locator is
expected to be valid. The lifetime is expressed in seconds. Each expected to be valid. The lifetime is expressed in seconds. Each
locator MUST have a non-zero lifetime. The address is expected to locator MUST have a non-zero lifetime. The address is expected to
become deprecated when the specified number of seconds has passed become deprecated when the specified number of seconds has passed
since the reception of the message. A deprecated address SHOULD NOT since the reception of the message. A deprecated address SHOULD NOT
be used as an destination address if an alternate (non-deprecated) is be used as an destination address if an alternate (non-deprecated) is
available and has sufficient scope. available and has sufficient scope.
4.1 Traffic Type and Preferred Locator 4.1. Traffic Type and Preferred Locator
The following Traffic Type values are defined: The following Traffic Type values are defined:
0: Both signaling (HIP control packets) and user data. 0: Both signaling (HIP control packets) and user data.
1: Signaling packets only. 1: Signaling packets only.
2: Data packets only. 2: Data packets only.
The "P" bit, when set, has scope over the corresponding Traffic Type The "P" bit, when set, has scope over the corresponding Traffic Type
that precedes it. That is, if a "P" bit is set for Traffic Type "2", that precedes it. That is, if a "P" bit is set for Traffic Type "2",
for example, that means that the locator is preferred for data for example, that means that the locator is preferred for data
packets. If there is a conflict (for example, if P bit is set for packets. If there is a conflict (for example, if P bit is set for an
both "0" and "2"), the more specific Traffic Type rule applies. By address of Type "0" and a different address of Type "2"), the more
default, the IP addresses used in the base exchange are preferred specific Traffic Type rule applies. By default, the IP addresses
locators for both signaling and user data, unless a new preferred used in the base exchange are preferred locators for both signaling
locator supersedes them. If no locators are indicated as preferred and user data, unless a new preferred locator supersedes them. If no
for a given Traffic Type, the implementation may use an arbitrary locators are indicated as preferred for a given Traffic Type, the
locator from the set of active locators. implementation may use an arbitrary locator from the set of active
locators.
4.2 Locator Type and Locator 4.2. Locator Type and Locator
The following Locator Type values are defined, along with the The following Locator Type values are defined, along with the
associated semantics of the Locator field: associated semantics of the Locator field:
0: An IPv6 address or an IPv4-in-IPv6 format IPv4 address [7] (128 0: An IPv6 address or an IPv4-in-IPv6 format IPv4 address [7] (128
bits long). bits long).
1: The concatenation of an ESP SPI (first 32 bits) followed by an 1: The concatenation of an ESP SPI (first 32 bits) followed by an
IPv6 address or an IPv4-in-IPv6 format IPv4 address (an additional IPv6 address or an IPv4-in-IPv6 format IPv4 address (an additional
128 bits). 128 bits).
4.3 UPDATE packet with included LOCATOR 4.3. UPDATE packet with included LOCATOR
A number of combinations of parameters in an UPDATE packet are A number of combinations of parameters in an UPDATE packet are
possible (e.g., see Section 3.2). Any UPDATE packet that includes a possible (e.g., see Section 3.2). Only one LOCATOR parameter is used
LOCATOR parameter SHOULD include both an HMAC and a HIP_SIGNATURE in any HIP packet, and this LOCATOR SHOULD list all of the locators
parameter. that the host wishes to make available for the HIP association. Any
UPDATE packet that includes a LOCATOR parameter SHOULD include both
an HMAC and a HIP_SIGNATURE parameter.
5. Processing rules 5. Processing rules
HIP mobility and multihoming is fundamentally based on the HIP 5.1. Locator data structure and status
architecture [1], where the transport and internetworking layers are
decoupled from each other by an interposed host identity protocol
layer. In the HIP architecture, the transport layer sockets are
bound to the Host Identifiers (through HIT or LSI in the case of
legacy APIs), and the Host Identifiers are translated to the actual
IP address.
The HIP base protocol specification [2] is expected to be commonly
used with the ESP Transport Format [5] to establish a pair of
Security Associations (SA). The ESP SAs are then used to carry the
actual payload data between the two hosts, by wrapping TCP, UDP, and
other upper layer packets into transport mode ESP payloads. The IP
header uses the actual IP addresses in the network.
Although HIP may also be specified in the future to operate with an
alternative to ESP providing the per-packet HIP context, the
remainder of this document assumes that HIP is being used in
conjunction with ESP. Future documents may extend this document to
include other behaviors when ESP is not used.
The base specification does not contain any mechanisms for changing
the IP addresses that were used during the base HIP exchange. Hence,
in order to remain connected, any systems that implement only the
base specification and nothing else must retain the ability to
receive packets at their primary IP address; that is, those systems
cannot change the IP address on which they are using to receive
packets without causing loss of connectivity until a base exchange is
performed from the new address.
5.1 Locator data structure and status
In a typical implementation, each outgoing locator is represented as In a typical implementation, each outgoing locator is represented by
a piece of state that contains the following data: a piece of state that contains the following data:
o the actual bit pattern representing the locator, o the actual bit pattern representing the locator,
o lifetime (seconds), o lifetime (seconds),
o status (UNVERIFIED, ACTIVE, DEPRECATED). o status (UNVERIFIED, ACTIVE, DEPRECATED).
The status is used to track the reachability of the address embedded The status is used to track the reachability of the address embedded
within the LOCATOR parameter: within the LOCATOR parameter:
skipping to change at page 24, line 34 skipping to change at page 26, line 50
some time, and the local policy mandates that the address some time, and the local policy mandates that the address
reachability must be verified again before starting to use it reachability must be verified again before starting to use it
again. again.
DEPRECATED to UNVERIFIED The host receives a new lifetime for the DEPRECATED to UNVERIFIED The host receives a new lifetime for the
locator. locator.
A DEPRECATED address MUST NOT be changed to ACTIVE without first A DEPRECATED address MUST NOT be changed to ACTIVE without first
verifying its reachability. verifying its reachability.
5.2 Sending LOCATORs 5.2. Sending LOCATORs
The decision of when to send LOCATORs is basically a local policy The decision of when to send LOCATORs is basically a local policy
issue. However, it is RECOMMENDED that a host sends a LOCATOR issue. However, it is RECOMMENDED that a host sends a LOCATOR
whenever it recognizes a change of its IP addresses, and assumes that whenever it recognizes a change of its IP addresses in use on an
the change is going to last at least for a few seconds. Rapidly active HIP association, and assumes that the change is going to last
sending conflicting LOCATORs SHOULD be avoided. at least for a few seconds. Rapidly sending conflicting LOCATORs
SHOULD be avoided.
When a host decides to inform its peers about changes in its IP When a host decides to inform its peers about changes in its IP
addresses, it has to decide how to group the various addresses, and addresses, it has to decide how to group the various addresses with
whether to include any addresses on multiple SPIs. Since each SPI is SPIs. The grouping should consider also whether middlebox
associated with a different Security Association, the grouping policy interaction requires sending (the same) LOCATOR in separate UPDATEs
may be based on ESP anti-replay protection considerations. In the on different paths. Since each SPI is associated with a different
typical case, simply basing the grouping on actual kernel level Security Association, the grouping policy may also be based on ESP
physical and logical interfaces is often the best policy. Virtual anti-replay protection considerations. In the typical case, simply
interfaces, such as IPsec tunnel interfaces or Mobile IP home basing the grouping on actual kernel level physical and logical
addresses SHOULD NOT be announced. interfaces may be the best policy. Grouping policy is outside of the
scope of this document.
Note that the purpose of announcing IP addresses in a LOCATOR is to Note that the purpose of announcing IP addresses in a LOCATOR is to
provide connectivity between the communicating hosts. In most cases, provide connectivity between the communicating hosts. In most cases,
tunnels (and therefore virtual interfaces) provide sub-optimal tunnels or virtual interfaces such as IPsec tunnel interfaces or
connectivity. Furthermore, it should be possible to replace most Mobile IP home addresses provide sub-optimal connectivity.
tunnels with HIP based "non-tunneling", therefore making most virtual Furthermore, it should be possible to replace most tunnels with HIP
interfaces fairly unnecessary in the future. On the other hand, based "non-tunneling", therefore making most virtual interfaces
there are clearly situations where tunnels are used for diagnostic fairly unnecessary in the future. Therefore, virtual interfaces
and/or testing purposes. In such and other similar cases announcing SHOULD NOT be announced in general. On the other hand, there are
the IP addresses of virtual interfaces may be appropriate. clearly situations where tunnels are used for diagnostic and/or
testing purposes. In such and other similar cases announcing the IP
addresses of virtual interfaces may be appropriate.
Once the host has decided on the groups and assignment of addresses Once the host has decided on the groups and assignment of addresses
to the SPIs, it creates a LOCATOR parameter for each group. If there to the SPIs, it creates a LOCATOR parameter that serves as a complete
are multiple LOCATOR parameters, the parameters MUST be ordered so representation of the addresses and affiliated SPIs intended for
that the new preferred locator is in the first LOCATOR parameter. active use. We now describe a few cases introduced in Section 3.2.
Only one locator (the first one, if at all) may be indicated as We assume that the Traffic Type for each locator is set to "0" (other
preferred for each distinct Traffic Type in the LOCATOR parameter. values for Traffic Type may be specified in documents that separate
HIP control plane from data plane traffic). Other mobility and
multihoming cases are possible but are left for further
experimentation.
If addresses are being added to an existing SPI, the LOCATOR 1. Host mobility with no multihoming and no rekeying. The mobile
parameter includes the full set of valid addresses for that SPI, each host creates a single UPDATE containing a single ESP_INFO with a
using a Locator Type of "1" and each with the same value for SPI. single LOCATOR parameter. The ESP_INFO contains the current
Any locators previously ACTIVE on that SPI that are not included in value of the SPI in both the "Old SPI" and "New SPI" fields. The
the LOCATOR will be set to DEPRECATED by the receiver. LOCATOR contains a single Locator with a "Locator Type" of "1";
the SPI must match that of the ESP_INFO. The Preferred bit
SHOULD be set and the "Locator Lifetime" is set according to
local policy. The UPDATE also contains a SEQ parameter as usual
and is protected by retransmission. The UPDATE should be sent to
the peer's preferred IP address with an IP source address
corresponding to the address in the LOCATOR parameter.
If a mobile host decides to change the SPI upon a readdress, it sends 2. Host mobility with no multihoming but with rekeying. The mobile
a LOCATOR with the SPI field within the LOCATOR set to the new SPI, host creates a single UPDATE containing a single ESP_INFO with a
and also an ESP_INFO parameter with the Old SPI field set to the single LOCATOR parameter (with a single address). The ESP_INFO
previous SPI and the New SPI field set to the new SPI. If multiple contains the current value of the SPI in the "Old SPI" and the
LOCATOR and ESP_INFO parameters are included, the ESP_INFO MUST be new value of the SPI in the "New SPI", and a "Keymat Index" as
ordered such that they appear in the same order as the set of selected by local policy. Optionally, the host may choose to
corresponding LOCATORs. The decision as to whether to rekey and send initiate a Diffie Hellman rekey by including a DIFFIE_HELLMAN
a new Diffie-Hellman parameter while performing readdressing is a parameter. The LOCATOR contains a single Locator with "Locator
local policy decision. Type" of "1"; the SPI must match that of the "New SPI" in the
ESP_INFO. Otherwise, the steps are identical to the case when no
rekeying is initiated.
If new addresses and new SPIs are being created, the LOCATOR 3. Host multihoming (addition of an address). We only describe the
parameter's SPI field contains the new SPI, and the ESP_INFO simple case of adding an additional address to a single-homed,
parameter's Old SPI field and New SPI fields are both set to the new non-mobile host. The host SHOULD set up a new SA pair between
SPI, indicating that this is a new and not a replacement SPI. this new address and the preferred address of the peer host. To
do this, the multihomed host creates a new inbound SA and creates
a new ESP_INFO parameter with an "Old SPI" parameter of "0", a
"New SPI" parameter corresponding to the new SPI, and a "Keymat
Index" as selected by local policy. The host adds to the UPDATE
message a LOCATOR with two Type "1" Locators: the original
address and SPI active on the association, and the new address
and new SPI being added (with the SPI matching the "New SPI"
contained in the ESP_INFO). The Preferred bit SHOULD be set
depending on the policy to tell the peer host which of the two
locators is preferred. The UPDATE also contains a SEQ parameter
and optionally a DIFFIE_HELLMAN parameter, and follows rekeying
procedures with respect to this new address. The UPDATE message
SHOULD be sent to the peer's preferred address with a source
address corresponding to the new locator.
If there are multiple LOCATOR parameters leading to a packet size The sending of multiple LOCATORs, locators with Locator Type "0", and
that exceeds the MTU, HIP fragmentation rules as described in [2] multiple ESP_INFO parameters is for further study.
shall apply.
5.3 Handling received LOCATORs 5.3. Handling received LOCATORs
A host SHOULD be prepared to receive LOCATOR parameters in any HIP A host SHOULD be prepared to receive a LOCATOR parameter in any HIP
packets, excluding I1. packet, excluding I1.
When a host receives a LOCATOR parameter, it first performs the This document describes sending both ESP_INFO and LOCATOR parameters
following operations: in an UPDATE. The ESP_INFO parameter is included if there is a need
to rekey or key a new SPI, and is otherwise included for the possible
benefit of HIP-aware middleboxes. The LOCATOR parameter contains a
complete map of the locators that the host wishes to make or keep
active for the HIP association.
1. For each locator listed in the LOCATOR parameter, check that the In general, the processing of a LOCATOR depends upon the packet type
in which it is included and upon whether ESP_INFO parameter is
included. Here, we describe only the case in which ESP_INFO is
present and a single LOCATOR and ESP_INFO are sent in an UPDATE
message; other cases are for further study. The steps below cover
each of the cases described in Section 5.2.
When a host receives a LOCATOR parameter in a validated HIP packet,
it first performs the following operations:
1. The host checks if the New SPI listed in the ESP_INFO is a new
one. If it is a new one, it creates a new inbound SA with that
SPI that contains no addresses. If it is an existing one, it
prepares to change the address set on the existing SPI.
2. For each locator listed in the LOCATOR parameter, check that the
address therein is a legal unicast or anycast address. That is, address therein is a legal unicast or anycast address. That is,
the address MUST NOT be a broadcast or multicast address. Note the address MUST NOT be a broadcast or multicast address. Note
that some implementations MAY accept addresses that indicate the that some implementations MAY accept addresses that indicate the
local host, since it may be allowed that the host runs HIP with local host, since it may be allowed that the host runs HIP with
itself. itself.
2. For each address listed in the LOCATOR parameter, check if the 3. For each Type 1 address listed in the LOCATOR parameter, check if
address is already bound to the SPI. If the address is already the address is already bound to the SPI indicated. If the
bound, its lifetime is updated. If the status of the address is address is already bound, its lifetime is updated. If the status
DEPRECATED, the status is changed to UNVERIFIED. If the address of the address is DEPRECATED, the status is changed to
is not already bound, the address is added, and its status is set UNVERIFIED. If the address is not already bound, the address is
to UNVERIFIED. Mark all addresses on the SPI that were NOT added, and its status is set to UNVERIFIED. Mark all addresses
listed in the LOCATOR parameter as DEPRECATED. As a result, the on the SPI that were NOT listed in the LOCATOR parameter as
SPI now contains any addresses listed in the LOCATOR parameter DEPRECATED. As a result, the SPI now contains any addresses
either as UNVERIFIED or ACTIVE, and any old addresses not listed listed in the LOCATOR parameter either as UNVERIFIED or ACTIVE,
in the LOCATOR parameter as DEPRECATED. and any old addresses not listed in the LOCATOR parameter as
DEPRECATED.
3. If the LOCATOR is paired with an ESP_INFO parameter, the ESP_INFO 4. If the LOCATOR is paired with an ESP_INFO parameter, the ESP_INFO
parameter is processed. If the LOCATOR is replacing the address parameter is processed as follows:
on an existing SPI, the SPI itself may be changed-- in this case,
the host proceeds according to HIP rekeying procedures. This
case is indicated by the ESP_INFO parameter including an existing
SPI in the Old SPI field and a new SPI in the New SPI field, and
the SPI field in the LOCATOR matching the New SPI in the
ESP_INFO. If instead the LOCATOR corresponds to a new SPI, the
ESP_INFO will include the same SPI in both its Old SPI and New
SPI fields.
4. Mark all locators at the address group that were NOT listed in 1. If the Old SPI indicates an existing SPI and the New SPI is a
the LOCATOR parameter as DEPRECATED. different non-zero value, the existing SA is being rekeyed
and the host follows HIP ESP rekeying procedures. Note that
the Locators in the LOCATOR parameter will use this New SPI
instead of the Old SPI.
2. If the Old SPI value is zero and the New SPI is a new non-
zero value, then a new SA is being requested by the peer.
This case is also treated like a rekeying event; the
receiving host must create a new inbound SA and respond with
an UPDATE ACK.
3. If the Old SPI indicates an existing SPI and the New SPI is
zero, the SPI is being deprecated and all locators uniquely
bound to the SPI are put into DEPRECATED state.
4. If the Old SPI equals the New SPI and both correspond to an
existing SPI, the ESP_INFO is gratuitous (provided for
middleboxes) and no rekeying is necessary.
5. Mark all locators on each SPI that were NOT listed in the LOCATOR
parameter as DEPRECATED.
As a result, each SPI now contains any addresses listed in the
LOCATOR parameter either as UNVERIFIED or ACTIVE, and any old
addresses not listed in the LOCATOR parameter as DEPRECATED.
Once the host has updated the SPI, if the LOCATOR parameter contains Once the host has updated the SPI, if the LOCATOR parameter contains
a new preferred locator, the host SHOULD initiate a change of the a new preferred locator, the host SHOULD initiate a change of the
preferred locator. This requires that the host first verifies preferred locator. This requires that the host first verifies
reachability of the associated address, and only then changes the reachability of the associated address, and only then changes the
preferred locator. See Section 5.6. preferred locator. See Section 5.6.
5.4 Verifying address reachability 5.4. Verifying address reachability
A host MUST verify the reachability of an UNVERIFIED address. The A host MUST verify the reachability of an UNVERIFIED address. The
status of a newly learned address MUST initially be set to UNVERIFIED status of a newly learned address MUST initially be set to UNVERIFIED
unless the new address is advertised in a R1 packet as a new unless the new address is advertised in a R1 packet as a new
preferred locator. A host MAY also want to verify the reachability preferred locator. A host MAY also want to verify the reachability
of an ACTIVE address again after some time, in which case it would of an ACTIVE address again after some time, in which case it would
set the status of the address to UNVERIFIED and reinitiate address set the status of the address to UNVERIFIED and reinitiate address
verification verification
A host typically starts the address-verification procedure by sending A host typically starts the address-verification procedure by sending
a nonce to the new address. For example, if the host is changing its a nonce to the new address. For example, if the host is changing its
SPI and is sending an ESP_INFO to the peer, the new SPI value SHOULD SPI and is sending an ESP_INFO to the peer, the new SPI value SHOULD
be random and the value MAY be copied into an ECHO_REQUEST sent in be random and the value MAY be copied into an ECHO_REQUEST sent in
the rekeying UPDATE. If the host is not rekeying, it MAY still use the rekeying UPDATE. If the host is not rekeying, it MAY still use
the ECHO_REQUEST parameter in an UPDATE message sent to the new the ECHO_REQUEST parameter in an UPDATE message sent to the new
address. A host MAY also use other message exchanges as confirmation address. A host MAY also use other message exchanges as confirmation
of the address reachability. of the address reachability.
Note that in the case of receiving a LOCATOR on an R1 and replying Note that in the case of receiving a LOCATOR on an R1 and replying
skipping to change at page 28, line 5 skipping to change at page 31, line 33
When address verification is in progress for a new preferred locator, When address verification is in progress for a new preferred locator,
the host SHOULD select a different locator listed as ACTIVE, if one the host SHOULD select a different locator listed as ACTIVE, if one
such locator is available, to continue communications until address such locator is available, to continue communications until address
verification completes. Alternatively, the host MAY use the new verification completes. Alternatively, the host MAY use the new
preferred locator while in UNVERIFIED status to the extent Credit- preferred locator while in UNVERIFIED status to the extent Credit-
Based Authorization permits. Credit-Based Authorization is explained Based Authorization permits. Credit-Based Authorization is explained
in Section 5.5. Once address verification succeeds, the status of in Section 5.5. Once address verification succeeds, the status of
the new preferred locator changes to ACTIVE. the new preferred locator changes to ACTIVE.
5.5 Credit-Based Authorization 5.5. Credit-Based Authorization
5.5.1 Handling Payload Packets 5.5.1. Handling Payload Packets
A host maintains a "credit counter" for each of its peers. Whenever A host maintains a "credit counter" for each of its peers. Whenever
a packet arrives from a peer, the host SHOULD increase that peer's a packet arrives from a peer, the host SHOULD increase that peer's
credit counter by the size of the received packet. When the host has credit counter by the size of the received packet. When the host has
a packet to be sent to the peer, if the peers preferred locator is a packet to be sent to the peer, if the peers preferred locator is
listed as UNVERIFIED and no alternative locator with status ACTIVE is listed as UNVERIFIED and no alternative locator with status ACTIVE is
available, the host checks whether it can send the packet to the available, the host checks whether it can send the packet to the
UNVERIFIED locator: The packet SHOULD be sent if the value of the UNVERIFIED locator: The packet SHOULD be sent if the value of the
credit counter is higher than the size of the outbound packet. If credit counter is higher than the size of the outbound packet. If
the credit counter is too low, the packet MUST be discarded or the credit counter is too low, the packet MUST be discarded or
skipping to change at page 29, line 44 skipping to change at page 33, line 44
| |
v v
+---------------+ +---------------+ +---------------+ +---------------+
| Reduce credit | | Send packet | | Reduce credit | | Send packet |
| counter by |----------------> | to preferred | | counter by |----------------> | to preferred |
| packet size | | address | | packet size | | address |
+---------------+ +---------------+ +---------------+ +---------------+
Figure 16: Sending Packets with Credit-Based Authorization Figure 16: Sending Packets with Credit-Based Authorization
5.5.2 Credit Aging 5.5.2. Credit Aging
A host ensures that the credit counters it maintains for its peers A host ensures that the credit counters it maintains for its peers
gradually decrease over time. Such "credit aging" prevents a gradually decrease over time. Such "credit aging" prevents a
malicious peer from building up credit at a very slow speed and using malicious peer from building up credit at a very slow speed and using
this, all at once, for a severe burst of redirected packets. this, all at once, for a severe burst of redirected packets.
Credit aging may be implemented by multiplying credit counters with a Credit aging may be implemented by multiplying credit counters with a
factor, CreditAgingFactor, less than one in fixed time intervals of factor, CreditAgingFactor, less than one in fixed time intervals of
CreditAgingInterval length. Choosing appropriate values for CreditAgingInterval length. Choosing appropriate values for
CreditAgingFactor and CreditAgingInterval is important to ensure that CreditAgingFactor and CreditAgingInterval is important to ensure that
skipping to change at page 30, line 22 skipping to change at page 34, line 22
credit counter might be too low to continue sending packets until credit counter might be too low to continue sending packets until
address verification concludes. address verification concludes.
The parameter values proposed in this document are as follows: The parameter values proposed in this document are as follows:
CreditAgingFactor 7/8 CreditAgingFactor 7/8
CreditAgingInterval 5 seconds CreditAgingInterval 5 seconds
These parameter values work well when the host transfers a file to These parameter values work well when the host transfers a file to
the peer via a TCP connection and the end-to-end round-trip time does the peer via a TCP connection and the end-to-end round-trip time does
not exeed 500 milliseconds. Alternative credit-aging algorithms may not exceed 500 milliseconds. Alternative credit-aging algorithms may
use other parameter values or different parameters, which may even be use other parameter values or different parameters, which may even be
dynamically established. dynamically established.
5.6 Changing the preferred locator 5.6. Changing the preferred locator
A host MAY want to change the preferred outgoing locator for A host MAY want to change the preferred outgoing locator for
different reasons, e.g., because traffic information or ICMP error different reasons, e.g., because traffic information or ICMP error
messages indicate that the currently used preferred address may have messages indicate that the currently used preferred address may have
become unreachable. Another reason is receiving a LOCATOR parameter become unreachable. Another reason may be due to receiving a LOCATOR
that has the P-bit set. parameter that has the P-bit set.
To change the preferred locator, the host initiates the following To change the preferred locator, the host initiates the following
procedure: procedure:
1. If the new preferred locator has ACTIVE status, the preferred 1. If the new preferred locator has ACTIVE status, the preferred
locator is changed and the procedure succeeds. locator is changed and the procedure succeeds.
2. If the new preferred locator has UNVERIFIED status, the host 2. If the new preferred locator has UNVERIFIED status, the host
starts to verify its reachability. The host SHOULD use a starts to verify its reachability. The host SHOULD use a
different locator listed as ACTIVE until address verification different locator listed as ACTIVE until address verification
completes if one such locator is available. Altervatively, the completes if one such locator is available. Alternatively, the
host MAY use the new preferred locator, even though in UNVERIFIED host MAY use the new preferred locator, even though in UNVERIFIED
status, to the extent Credit-Based Authorization permits. Once status, to the extent Credit-Based Authorization permits. Once
address verification succeeds, the status of the new preferred address verification succeeds, the status of the new preferred
locator changes to ACTIVE and its use is no longer governed by locator changes to ACTIVE and its use is no longer governed by
Credit-Based Authorization. Credit-Based Authorization.
3. If the peer host has not indicated a preference for any address, 3. If the peer host has not indicated a preference for any address,
then the host picks one of the peer's ACTIVE addresses randomly then the host picks one of the peer's ACTIVE addresses randomly
or according to policy. This case may arise if, for example, or according to policy. This case may arise if, for example,
ICMP error messages arrive that deprecate the preferred locator, ICMP error messages arrive that deprecate the preferred locator,
but the peer has not yet indicated a new preferred locator. but the peer has not yet indicated a new preferred locator.
4. If the new preferred locator has DEPRECATED status and there is 4. If the new preferred locator has DEPRECATED status and there is
at least one non-deprecated address, the host selects one of the at least one non-deprecated address, the host selects one of the
non-deprecated addresses as a new preferred locator and non-deprecated addresses as a new preferred locator and
continues. If the selected address is UNVERIFIED, this includes continues. If the selected address is UNVERIFIED, this includes
address verification as described above. address verification as described above.
6. Policy considerations 6. Security Considerations
XXX: This section needs to be written.
The host may change the status of unused ACTIVE addresses into
UNVERIFIED after a locally configured period of inactivity.
7. Security Considerations
The HIP mobility mechanism provides a secure means of updating a The HIP mobility mechanism provides a secure means of updating a
host's IP address via HIP REA update packets. Upon receipt, a HIP host's IP address via HIP UPDATE packets. Upon receipt, a HIP host
host cryptographically verifies the sender of a REA update, so cryptographically verifies the sender of an UPDATE, so forging or
forging or replaying a HIP update packet is very difficult (see [2]). replaying a HIP UPDATE packet is very difficult (see [2]).
Therefore, security issues reside in other attack domains. The two Therefore, security issues reside in other attack domains. The two
we consider are malicious redirection of legitimate connections as we consider are malicious redirection of legitimate connections as
well as redirection-based flooding attacks using this protocol. This well as redirection-based flooding attacks using this protocol. This
can be broken down into the following: can be broken down into the following:
Impersonation attacks Impersonation attacks
- direct conversation with the misled victim - direct conversation with the misled victim
- man-in-the-middle attack - man-in-the-middle attack
skipping to change at page 33, line 38 skipping to change at page 36, line 38
* tool 2: flooding by zombies * tool 2: flooding by zombies
* tool 2: redirection-based flooding * tool 2: redirection-based flooding
- memory-exhaustion attacks - memory-exhaustion attacks
- computational exhaustion attacks - computational exhaustion attacks
We consider these in more detail in the following sections. We consider these in more detail in the following sections.
In Section 7.1 and Section 7.2, we assume that all users are using In Section 6.1 and Section 6.2, we assume that all users are using
HIP. In Section 7.3 we consider the security ramifications when we HIP. In Section 6.3 we consider the security ramifications when we
have both HIP and non-HIP users. have both HIP and non-HIP users.
7.1 Impersonation attacks 6.1. Impersonation attacks
An attacker wishing to impersonate will try to mislead its victim An attacker wishing to impersonate will try to mislead its victim
into directly communicating with them, or carry out a man in the into directly communicating with them, or carry out a man in the
middle attack between the victim and the victim's desired middle attack between the victim and the victim's desired
communication peer. Without mobility support, both attack types are communication peer. Without mobility support, both attack types are
possible only if the attacker resides on the routing path between its possible only if the attacker resides on the routing path between its
victim and the victim's desired communication peer, or if the victim and the victim's desired communication peer, or if the
attacker tricks its victim into initiating the connection over an attacker tricks its victim into initiating the connection over an
incorrect routing path (e.g., by acting as a router or using spoofed incorrect routing path (e.g., by acting as a router or using spoofed
DNS entries). DNS entries).
The HIP extensions defined in this specification change the situation The HIP extensions defined in this specification change the situation
in that they introduce an ability to redirect a connection (like in that they introduce an ability to redirect a connection (like
IPv6), both before and after establishment. If no precautionary IPv6), both before and after establishment. If no precautionary
measures are taken, an attacker could misuse this feature to measures are taken, an attacker could misuse this feature to
impersonate a victim's peer from any arbitrary location. The impersonate a victim's peer from any arbitrary location. The
authentication and authorization mechanisms of the HIP base exchange authentication and authorization mechanisms of the HIP base exchange
[2] and the signatures in the new REA update message prevent this [2] and the signatures in the UPDATE message prevent this attack.
offense. Furthermore, ownership of a connection is securely linked Furthermore, ownership of a HIP association is securely linked to a
to a HIP HI/HIT. If an attacker somehow uses a bug in the HIP HI/HIT. If an attacker somehow uses a bug in the implementation
implementation or weakness in some protocol to redirect a HIP or weakness in some protocol to redirect a HIP connection, the
connection, the original owner can always reclaim their connection original owner can always reclaim their connection (they can always
(they can always prove ownership of the private key associated with prove ownership of the private key associated with their public HI).
their public HI).
MitM attacks are always possible if the attacker is present during MitM attacks are always possible if the attacker is present during
the initial HIP base exchange but once the base exchange has taken the initial HIP base exchange and if the hosts do not authenticate
place even a MitM cannot steal a HIP connection because it is very each other's identities, but once the base exchange has taken place
difficult for an attacker to create an REA update packet (or any HIP even a MitM cannot steal an opportunistic HIP connection because it
packet) that will be accepted as a legitimate update. Update packets is very difficult for an attacker to create an UPDATE packet (or any
use HMAC and are signed. Even when an attacker can snoop packets to HIP packet) that will be accepted as a legitimate update. UPDATE
attain the SPI and HIT/HI, they still cannot forge an update packet packets use HMAC and are signed. Even when an attacker can snoop
without knowledge of the secret keys. packets to obtain the SPI and HIT/HI, they still cannot forge an
UPDATE packet without knowledge of the secret keys.
7.2 Denial of Service attacks 6.2. Denial of Service attacks
7.2.1 Flooding Attacks 6.2.1. Flooding Attacks
The purpose of a denial-of-service attack is to exhaust some resource The purpose of a denial-of-service attack is to exhaust some resource
of the victim such that the victim ceases operating correctly. A of the victim such that the victim ceases to operate correctly. A
denial-of-service attack can aim at the victim's network attachment denial-of-service attack can aim at the victim's network attachment
(flooding attack), its memory or its processing capacity. In a (flooding attack), its memory, or its processing capacity. In a
flooding attack the attacker causes an excessive number of bogus or flooding attack the attacker causes an excessive number of bogus or
unwanted packets to be sent to the victim, which fills their unwanted packets to be sent to the victim, which fills their
available bandwidth. Note that the victim does not necessarily need available bandwidth. Note that the victim does not necessarily need
to be a node; it can also be an entire network. The attack basically to be a node; it can also be an entire network. The attack basically
functions the same way in either case. functions the same way in either case.
An effective DoS strategy is distributed denial of service (DDoS). An effective DoS strategy is distributed denial of service (DDoS).
Here, the attacker conventionally distributes some viral software to Here, the attacker conventionally distributes some viral software to
as many nodes as possible. Under the control of the attacker, the as many nodes as possible. Under the control of the attacker, the
infected nodes, or "zombies", jointly send packets to the victim. infected nodes, or "zombies", jointly send packets to the victim.
skipping to change at page 35, line 15 skipping to change at page 38, line 15
checks and credit-based authorization. Both strategies do not checks and credit-based authorization. Both strategies do not
eliminate flooding attacks per se, but they preclude: (i) their use eliminate flooding attacks per se, but they preclude: (i) their use
from a location off the path towards the flooded victim; and (ii) any from a location off the path towards the flooded victim; and (ii) any
amplification in the number and size of the redirected packets. As a amplification in the number and size of the redirected packets. As a
result, the combination of a reachability check and credit-based result, the combination of a reachability check and credit-based
authorization makes a HIP redirection-based flooding attack as authorization makes a HIP redirection-based flooding attack as
effective and applicable as a normal, direct flooding attack in which effective and applicable as a normal, direct flooding attack in which
the attacker itself sends the flooding traffic to the victim. the attacker itself sends the flooding traffic to the victim.
This analysis leads to the following two points. First, when a This analysis leads to the following two points. First, when a
reachability packet is received this nonce packet MUST be ignored if reachability packet is received, this nonce packet MUST be ignored if
the HIT is not one that is currently active. Second, if the attacker the HIT is not one that is currently active. Second, if the attacker
is a MitM and can capture this nonce packet then they can respond to is a MitM and can capture this nonce packet then it can respond to
it, in which case it is possible for an attacker to redirect their it, in which case it is possible for an attacker to redirect the
connection. Note, this attack will always be possible when a connection. Note, this attack will always be possible when a
reachability packet is not sent. reachability packet is not sent.
7.2.2 Memory/Computational exhaustion DoS attacks 6.2.2. Memory/Computational exhaustion DoS attacks
We now consider whether or not the proposed extensions to HIP add any We now consider whether or not the proposed extensions to HIP add any
new DoS attacks (consideration of DoS attacks using the base HIP new DoS attacks (consideration of DoS attacks using the base HIP
exchange and updates is discussed in [2]). A simple attack is to exchange and updates is discussed in [2]). A simple attack is to
send many REA update packets containing many ip addresses that are send many UPDATE packets containing many IP addresses that are not
not flagged as preferred. The attacker continues to send such flagged as preferred. The attacker continues to send such packets
packets until the number of ip addresses associated with the until the number of IP addresses associated with the attacker's HI
attackers HI crashes the system. Therefore, their SHOULD be a limit crashes the system. Therefore, there SHOULD be a limit to the number
to the number of ip addresses that can be associated with any HI. of IP addresses that can be associated with any HI. Other forms of
Other forms of memory/computationally exhausting attacks via the HIP memory/computationally exhausting attacks via the HIP UPDATE packet
update packet are handled in the base HIP draft [2]. are handled in the base HIP draft [2].
7.3 Mixed deployment environment 6.3. Mixed deployment environment
We now assume that we have both HIP and non-HIP aware hosts. Four We now assume an environment with both HIP and non-HIP aware hosts.
cases exist. Four cases exist.
1. A HIP user redirects their connection onto a non-HIP user. The 1. A HIP user redirects their connection onto a non-HIP user. The
non-HIP user will drop the reachability packet so this is not a non-HIP user will drop the reachability packet so this is not a
threat unless the HIP user is a MitM and can respond to the threat unless the HIP user is a MitM and can respond to the
reachability packet. reachability packet.
2. A non-HIP user attempts to redirect their connection onto a HIP 2. A non-HIP user attempts to redirect their connection onto a HIP
user. This falls into IPv4 and IPv6 security concerns, which are user. This falls into IPv4 and IPv6 security concerns, which are
outside the scope of this document. outside the scope of this document.
3. A non-HIP user attempts to steal a HIP user's session (assume 3. A non-HIP user attempts to steal a HIP user's session (assume
that SeND is not active for the following). The non-HIP user that Secure Neighbor Discovery is not active for the following).
contacts the service that a HIP user has a connection with and The non-HIP user contacts the service that a HIP user has a
then attempts to use a IPv6 change of address request to steal connection with and then attempts to use a IPv6 change of address
the HIP user's connection. What will happen in this case is request to steal the HIP user's connection. What will happen in
implementation dependent but such a request should be ignored/ this case is implementation dependent but such a request should
dropped. Even if the attack is sucessful, the HIP user can be ignored/dropped. Even if the attack is successful, the HIP
reclaim their connection via HIP. user can reclaim its connection via HIP.
4. A HIP user attempts to steal a non-HIP user's session. This 4. A HIP user attempts to steal a non-HIP user's session. This
could be problematic since HIP sits 'on top of' layer 3. A HIP could be problematic since HIP sits 'on top of' layer 3. A HIP
user could spoof the non-HIP user's ip address during the base user could spoof the non-HIP user's IP address during the base
exhange or set the non-HIP user's ip address as their preferred exchange or set the non-HIP user's IP address as their preferred
address via an REA update. Other possibilities exist but a address via an UPDATE. Other possibilities exist but a simple
simple solution is to add a check which does not allow any HIP solution is to add a check which does not allow any HIP session
session to be moved to or created upon an already existing ip to be moved to or created upon an already existing IP address.
address.
8. IANA Considerations 7. IANA Considerations
9. Authors This document defines a LOCATOR parameter for the Host Identity
Protocol [2]. This parameter is defined in Section 4 with a Type of
193.
8. Authors
Pekka Nikander originated this Internet Draft. Tom Henderson, Jari Pekka Nikander originated this Internet Draft. Tom Henderson, Jari
Arkko, Greg Perkins, and Christian Vogt have each contributed Arkko, Greg Perkins, and Christian Vogt have each contributed
sections to this draft. sections to this draft.
10. Acknowledgments 9. Acknowledgments
The authors thank Mika Kousa for many improvements to the draft. The authors thank Mika Kousa, Jeff Ahrenholz, and Jan Melen for many
improvements to the draft.
11. References 10. References
11.1 Normative references 10.1. Normative references
[1] Moskowitz, R., "Host Identity Protocol Architecture", [1] Moskowitz, R. and P. Nikander, "Host Identity Protocol
draft-ietf-hip-arch-02 (work in progress), January 2005. Architecture", draft-ietf-hip-arch-03 (work in progress),
August 2005.
[2] Moskowitz, R., "Host Identity Protocol", draft-ietf-hip-base-03 [2] Moskowitz, R., "Host Identity Protocol", draft-ietf-hip-base-04
(work in progress), June 2005. (work in progress), October 2005.
[3] Laganier, J. and L. Eggert, "Host Identity Protocol (HIP) [3] Laganier, J. and L. Eggert, "Host Identity Protocol (HIP)
Rendezvous Extension", draft-ietf-hip-rvs-03 (work in progress), Rendezvous Extension", draft-ietf-hip-rvs-04 (work in progress),
July 2005. October 2005.
[4] Kent, S. and R. Atkinson, "IP Encapsulating Security Payload [4] Kent, S., "IP Encapsulating Security Payload (ESP)", RFC 4303,
(ESP)", RFC 2406, November 1998. December 2005.
[5] Jokela, P., "Using ESP transport format with HIP", [5] Jokela, P., "Using ESP transport format with HIP",
draft-ietf-hip-esp-00 (work in progress), July 2005. draft-ietf-hip-esp-01 (work in progress), October 2005.
[6] Bradner, S., "Key words for use in RFCs to Indicate Requirement [6] Bradner, S., "Key words for use in RFCs to Indicate Requirement
Levels", BCP 14, RFC 2119, March 1997. Levels", BCP 14, RFC 2119, March 1997.
[7] Hinden, R. and S. Deering, "IP Version 6 Addressing [7] Hinden, R. and S. Deering, "IP Version 6 Addressing
Architecture", RFC 2373, July 1998. Architecture", RFC 2373, July 1998.
11.2 Informative references 10.2. Informative references
[8] Bellovin, S., "EIDs, IPsec, and HostNAT", IETF 41th,
March 1998.
[9] Rescorla, E. and B. Korver, "Guidelines for Writing RFC Text on
Security Considerations", draft-iab-sec-cons-00 (work in
progress), August 2002.
[10] Nikander, P., "Mobile IP version 6 Route Optimization Security
Design Background", draft-nikander-mobileip-v6-ro-sec-02 (work
in progress), December 2003.
Author's Address
Tom Henderson
The Boeing Company
P.O. Box 3707
Seattle, WA
USA
Email: thomas.r.henderson@boeing.com [8] Nikander, P., Arkko, J., Aura, T., Montenegro, G., and E.
Nordmark, "Mobile IP Version 6 Route Optimization Security
Design Background", RFC 4225, December 2005.
Appendix A. Changes from previous versions Appendix A. Changes from previous versions
A.1 From nikander-hip-mm-00 to nikander-hip-mm-01 A.1. From nikander-hip-mm-00 to nikander-hip-mm-01
The actual protocol has been largely revised, based on the new The actual protocol has been largely revised, based on the new
symmetric New SPI (NES) design adopted in the base protocol draft symmetric New SPI (NES) design adopted in the base protocol draft
version -08. There are no more separate REA, AC or ACR packets, but version -08. There are no more separate REA, AC or ACR packets, but
their functionality has been folded into the NES packet. At the same their functionality has been folded into the NES packet. At the same
time, it has become possible to send REA parameters in R1 and I2. time, it has become possible to send REA parameters in R1 and I2.
The Forwarding Agent functionality was removed, since it looks like The Forwarding Agent functionality was removed, since it looks like
that it will be moved to the proposed HIP Research Group. Hence, that it will be moved to the proposed HIP Research Group. Hence,
there will be two other documents related to that, a simple there will be two other documents related to that, a simple
Rendezvous server document (WG item) and a Forwarding Agent document Rendezvous server document (WG item) and a Forwarding Agent document
(RG item). (RG item).
A.2 From nikander-hip-mm-01 to nikander-hip-mm-02 A.2. From nikander-hip-mm-01 to nikander-hip-mm-02
Alignment with base-00 draft (use of UPDATE and NOTIFY packets). Alignment with base-00 draft (use of UPDATE and NOTIFY packets).
The "logical interface" concept was dropped, and the SA/SPI was The "logical interface" concept was dropped, and the SA/SPI was
identified as the protocol component to which a HIP association binds identified as the protocol component to which a HIP association binds
addresses to. addresses to.
The RR was (again) made recommended, not mandatory, able to be The RR was (again) made recommended, not mandatory, able to be
administratively overridden. administratively overridden.
A.3 From -02 to draft-ietf-hip-mm-00 A.3. From -02 to draft-ietf-hip-mm-00
REA parameter type value is now "3" (was TBD before). REA parameter type value is now "3" (was TBD before).
Recommend that in multihoming situations, that inbound/outbound SAs Recommend that in multihoming situations, that inbound/outbound SAs
are paired to avoid ambiguity when rekeying them. are paired to avoid ambiguity when rekeying them.
Clarified that multihoming scenario for now was intended for failover Clarified that multihoming scenario for now was intended for failover
instead of load-balancing, due to transport layer issues. instead of load-balancing, due to transport layer issues.
Clarified that if HIP negotiates base exchange using link local Clarified that if HIP negotiates base exchange using link local
skipping to change at page 43, line 11 skipping to change at page 45, line 11
SPI but not in the new REA parameter should be DEPRECATED. SPI but not in the new REA parameter should be DEPRECATED.
Clarified that address verification pertains to *outgoing* addresses. Clarified that address verification pertains to *outgoing* addresses.
When discussing inclusion of REA in I2, the draft stated "The When discussing inclusion of REA in I2, the draft stated "The
Responder MUST make sure that the puzzle solution is valid BOTH for Responder MUST make sure that the puzzle solution is valid BOTH for
the initial IP destination address used for I1 and for the new the initial IP destination address used for I1 and for the new
preferred address." However, this statement conflicted with Appendix preferred address." However, this statement conflicted with Appendix
D of the base specification, so it has been removed for now. D of the base specification, so it has been removed for now.
A.4 From draft-ietf-hip-mm-00 to -01 A.4. From draft-ietf-hip-mm-00 to -01
Introduction section reorganized. Some of the scope of the document Introduction section reorganized. Some of the scope of the document
relating to multihoming was reduced. relating to multihoming was reduced.
Removed empty appendix "Implementation experiences" Removed empty appendix "Implementation experiences"
Renamed REA parameter to LOCATOR and aligned to the discussion on Renamed REA parameter to LOCATOR and aligned to the discussion on
redefining this parameter that occurred on the RG mailing list. redefining this parameter that occurred on the RG mailing list.
Aligned with decoupling of ESP from base spec. Aligned with decoupling of ESP from base spec.
A.5 From draft-ietf-hip-mm-01 to -02 A.5. From draft-ietf-hip-mm-01 to -02
Aligned with draft-ietf-hip-base-03 and draft-ietf-hip-esp-00 Aligned with draft-ietf-hip-base-03 and draft-ietf-hip-esp-00
Address verification is a MUST (C. Vogt, list post on 06/12/05) Address verification is a MUST (C. Vogt, list post on 06/12/05)
If UPDATE exceeds MTU because of too many locators, do not split into If UPDATE exceeds MTU because of too many locators, do not split into
multiple UPDATEs, but instead rely on IP fragmentation (C. Vogt, list multiple UPDATEs, but instead rely on IP fragmentation (C. Vogt, list
post on 06/12/05) post on 06/12/05)
New value for LOCATOR parameter type (193), per 05/31/05 discussion New value for LOCATOR parameter type (193), per 05/31/05 discussion
skipping to change at page 44, line 5 skipping to change at page 45, line 47
Vogt Vogt
Security section contributed by Greg Perkins, with subsequent editing Security section contributed by Greg Perkins, with subsequent editing
from C. Vogt and P. Nikander from C. Vogt and P. Nikander
Reorganization according to RFC 4101 guidance on writing protocol Reorganization according to RFC 4101 guidance on writing protocol
models models
Open issue: LOCATOR parameter semantics (implicit/explicit removal) Open issue: LOCATOR parameter semantics (implicit/explicit removal)
A.6. From draft-ietf-hip-mm-02 to -03
Aligned with draft-ietf-hip-base-05 and draft-ietf-hip-esp-02
Further clarification that the scope of this draft is primarily
limited to the case in which ESP is used
New layered architectural overview in Section 3
Limited the scope of multihoming description to just a single host
adding a single new address; other cases left for further study
Require that ESP_INFO be included on all UPDATE packets relating to
mobility and multihoming (for middleboxes)
New convention for use of "Old SPI" and "New SPI" values to signal
new SPIs (Old SPI == 0, New SPI != 0) and gratuitous ESP_INFOs with
no rekeying (Old SPI == New SPI != 0).
Only specify the use of Locator Type of 1 when using ESP, for
simplicity of receiver processing.
Removed multiple addresses in LOCATOR example of section 3.2.2,
because it is not clear that the example is correct (requires further
study)
Corrected mention of sending ECHO_REQUEST nonce in R2 (should be sent
in separate UPDATE because R2 is not an acknowledged packet)
Removed first four paragraphs of Section 5, which were redundant with
previous introductory material.
Rewrote Sections 5.2 and 5.3 on sending and receiving LOCATOR, to
more explicitly cover the scenario scope of this document.
Removed unwritten "Policy Considerations" section
Author's Address
Tom Henderson
The Boeing Company
P.O. Box 3707
Seattle, WA
USA
Email: thomas.r.henderson@boeing.com
Intellectual Property Statement Intellectual Property Statement
The IETF takes no position regarding the validity or scope of any The IETF takes no position regarding the validity or scope of any
Intellectual Property Rights or other rights that might be claimed to Intellectual Property Rights or other rights that might be claimed to
pertain to the implementation or use of the technology described in pertain to the implementation or use of the technology described in
this document or the extent to which any license under such rights this document or the extent to which any license under such rights
might or might not be available; nor does it represent that it has might or might not be available; nor does it represent that it has
made any independent effort to identify any such rights. Information made any independent effort to identify any such rights. Information
on the procedures with respect to rights in RFC documents can be on the procedures with respect to rights in RFC documents can be
found in BCP 78 and BCP 79. found in BCP 78 and BCP 79.
skipping to change at page 44, line 41 skipping to change at page 48, line 41
This document and the information contained herein are provided on an This document and the information contained herein are provided on an
"AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET
ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED, ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED,
INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE
INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
Copyright Statement Copyright Statement
Copyright (C) The Internet Society (2005). This document is subject Copyright (C) The Internet Society (2006). This document is subject
to the rights, licenses and restrictions contained in BCP 78, and to the rights, licenses and restrictions contained in BCP 78, and
except as set forth therein, the authors retain all their rights. except as set forth therein, the authors retain all their rights.
Acknowledgment Acknowledgment
Funding for the RFC Editor function is currently provided by the Funding for the RFC Editor function is currently provided by the
Internet Society. Internet Society.
 End of changes. 132 change blocks. 
518 lines changed or deleted 688 lines changed or added

This html diff was produced by rfcdiff 1.29, available from http://www.levkowetz.com/ietf/tools/rfcdiff/