draft-ietf-hip-mm-01.txt   draft-ietf-hip-mm-02.txt 
Network Working Group P. Nikander Network Working Group T. Henderson (editor)
Internet-Draft J. Arkko Internet-Draft The Boeing Company
Expires: August 21, 2005 Ericsson Research Nomadic Lab Expires: January 18, 2006 July 17, 2005
T. Henderson
The Boeing Company
February 20, 2005
End-Host Mobility and Multi-Homing with the Host Identity Protocol End-Host Mobility and Multihoming with the Host Identity Protocol
draft-ietf-hip-mm-01 draft-ietf-hip-mm-02
Status of this Memo Status of this Memo
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Abstract Abstract
This document defines a "locator" parameter for the Host Identity This document defines mobility and multihoming extensions to the Host
Protocol and specifies an end-host mobility mechanism. Identity Protocol (HIP). Specifically, this document defines a
general "LOCATOR" parameter for HIP messages that allows for a HIP
host to notify peers about alternate addresses at which it may be
reached. This document also defines elements of procedure for
mobility of a HIP host-- the process by which a host dynamically
changes the primary locator that it uses to receive packets. While
the same LOCATOR parameter can also be used to support end-host
multihoming, detailed procedures are left for further study.
Table of Contents Table of Contents
1. Introduction and Scope . . . . . . . . . . . . . . . . . . . . 3 1. Introduction and Scope . . . . . . . . . . . . . . . . . . . . 4
2. Conventions used in this document . . . . . . . . . . . . . . 5 2. Terminology and Conventions . . . . . . . . . . . . . . . . . 5
3. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 6 3. Protocol Model . . . . . . . . . . . . . . . . . . . . . . . . 6
4. LOCATOR parameter format . . . . . . . . . . . . . . . . . . . 7 3.1 Operating Environment . . . . . . . . . . . . . . . . . . 6
4.1 Traffic Type and Preferred Locator . . . . . . . . . . . . 8 3.1.1 Locator . . . . . . . . . . . . . . . . . . . . . . . 6
4.2 Locator Type and Locator . . . . . . . . . . . . . . . . . 8 3.1.2 Mobility . . . . . . . . . . . . . . . . . . . . . . . 7
4.3 UPDATE packet with included LOCATOR . . . . . . . . . . . 9 3.1.3 Multihoming . . . . . . . . . . . . . . . . . . . . . 7
5. Overview of HIP basic mobility and multi-homing 3.2 Protocol Overview . . . . . . . . . . . . . . . . . . . . 8
functionality . . . . . . . . . . . . . . . . . . . . . . . . 10 3.2.1 Mobility with single SA pair . . . . . . . . . . . . . 8
5.1 Informing the peer about multiple or changed locator(s) . 10 3.2.2 Host multihoming . . . . . . . . . . . . . . . . . . . 10
5.2 Address verification . . . . . . . . . . . . . . . . . . . 13 3.2.3 Site multihoming . . . . . . . . . . . . . . . . . . . 12
5.3 Preferred locator . . . . . . . . . . . . . . . . . . . . 13 3.2.4 Dual host multihoming . . . . . . . . . . . . . . . . 12
5.4 Locator data structure and status . . . . . . . . . . . . 14 3.2.5 Combined mobility and multihoming . . . . . . . . . . 13
6. Protocol overview . . . . . . . . . . . . . . . . . . . . . . 15 3.2.6 Using LOCATORs across addressing realms . . . . . . . 13
6.1 Mobility with single SA pair . . . . . . . . . . . . . . . 15 3.2.7 Network renumbering . . . . . . . . . . . . . . . . . 13
6.2 Host multihoming . . . . . . . . . . . . . . . . . . . . . 17 3.2.8 Initiating the protocol in R1 or I2 . . . . . . . . . 13
6.3 Site multi-homing . . . . . . . . . . . . . . . . . . . . 19 3.3 Other Considerations . . . . . . . . . . . . . . . . . . . 15
6.4 Dual host multi-homing . . . . . . . . . . . . . . . . . . 19 3.3.1 Address Verification . . . . . . . . . . . . . . . . . 15
6.5 Combined mobility and multi-homing . . . . . . . . . . . . 20 3.3.2 Credit-Based Authorization . . . . . . . . . . . . . . 15
6.6 Using LOCATORs across addressing realms . . . . . . . . . 20 3.3.3 Preferred locator . . . . . . . . . . . . . . . . . . 16
6.7 Network renumbering . . . . . . . . . . . . . . . . . . . 20 3.3.4 Interaction with Security Associations . . . . . . . . 17
6.8 Initiating the protocol in R1 or I2 . . . . . . . . . . . 20 4. LOCATOR parameter format . . . . . . . . . . . . . . . . . . . 20
7. Processing rules . . . . . . . . . . . . . . . . . . . . . . . 22 4.1 Traffic Type and Preferred Locator . . . . . . . . . . . . 21
7.1 Sending LOCATORs . . . . . . . . . . . . . . . . . . . . . 22 4.2 Locator Type and Locator . . . . . . . . . . . . . . . . . 22
7.2 Handling received LOCATORs . . . . . . . . . . . . . . . . 23 4.3 UPDATE packet with included LOCATOR . . . . . . . . . . . 22
7.3 Verifying address reachability . . . . . . . . . . . . . . 24 5. Processing rules . . . . . . . . . . . . . . . . . . . . . . . 23
7.4 Changing the preferred locator . . . . . . . . . . . . . . 24 5.1 Locator data structure and status . . . . . . . . . . . . 23
8. Policy considerations . . . . . . . . . . . . . . . . . . . . 26 5.2 Sending LOCATORs . . . . . . . . . . . . . . . . . . . . . 24
9. Security Considerations . . . . . . . . . . . . . . . . . . . 27 5.3 Handling received LOCATORs . . . . . . . . . . . . . . . . 25
10. IANA Considerations . . . . . . . . . . . . . . . . . . . . 28 5.4 Verifying address reachability . . . . . . . . . . . . . . 26
11. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . 29 5.5 Credit-Based Authorization . . . . . . . . . . . . . . . . 28
12. References . . . . . . . . . . . . . . . . . . . . . . . . . 30 5.5.1 Handling Payload Packets . . . . . . . . . . . . . . . 28
12.1 Normative references . . . . . . . . . . . . . . . . . . . . 30 5.5.2 Credit Aging . . . . . . . . . . . . . . . . . . . . . 29
12.2 Informative references . . . . . . . . . . . . . . . . . . . 30 5.6 Changing the preferred locator . . . . . . . . . . . . . . 30
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . 30 6. Policy considerations . . . . . . . . . . . . . . . . . . . . 32
A. Changes from previous versions . . . . . . . . . . . . . . . . 32 7. Security Considerations . . . . . . . . . . . . . . . . . . . 33
A.1 From nikander-hip-mm-00 to nikander-hip-mm-01 . . . . . . 32 7.1 Impersonation attacks . . . . . . . . . . . . . . . . . . 33
A.2 From nikander-hip-mm-01 to nikander-hip-mm-02 . . . . . . 32 7.2 Denial of Service attacks . . . . . . . . . . . . . . . . 34
A.3 From -02 to draft-ietf-hip-mm-00 . . . . . . . . . . . . . 32 7.2.1 Flooding Attacks . . . . . . . . . . . . . . . . . . . 34
A.4 From draft-ietf-hip-mm-00 to -01 . . . . . . . . . . . . . 33 7.2.2 Memory/Computational exhaustion DoS attacks . . . . . 35
Intellectual Property and Copyright Statements . . . . . . . . 34 7.3 Mixed deployment environment . . . . . . . . . . . . . . . 35
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 37
9. Authors . . . . . . . . . . . . . . . . . . . . . . . . . . . 38
10. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . 39
11. References . . . . . . . . . . . . . . . . . . . . . . . . . 40
11.1 Normative references . . . . . . . . . . . . . . . . . . . 40
11.2 Informative references . . . . . . . . . . . . . . . . . . 40
Author's Address . . . . . . . . . . . . . . . . . . . . . . . 41
A. Changes from previous versions . . . . . . . . . . . . . . . . 42
A.1 From nikander-hip-mm-00 to nikander-hip-mm-01 . . . . . . 42
A.2 From nikander-hip-mm-01 to nikander-hip-mm-02 . . . . . . 42
A.3 From -02 to draft-ietf-hip-mm-00 . . . . . . . . . . . . . 42
A.4 From draft-ietf-hip-mm-00 to -01 . . . . . . . . . . . . . 43
A.5 From draft-ietf-hip-mm-01 to -02 . . . . . . . . . . . . . 43
Intellectual Property and Copyright Statements . . . . . . . . 44
1. Introduction and Scope 1. Introduction and Scope
The Host Identity Protocol [1] (HIP) defines a mechanism 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). When a host uses HIP, the internetworking layer (IPv4 and IPv6) by using public/private key
overlying protocol sublayers (e.g., transport layer sockets and ESP pairs, instead of IP addresses, as host identities. When a host uses
Security Associations) are not bound to IP addresses but instead to HIP, the overlying protocol sublayers (e.g., transport layer sockets
Host Identifiers. However, the hosts must also know at least one IP and ESP Security Associations) are instead bound to representations
address where their peers are reachable. Initially these IP of these host identities, and the IP addresses are only used for
addresses are the ones used during the HIP base exchange. packet forwarding. However, each host must also know at least one IP
address at which its peers are reachable. Initially, these IP
This document defines a generalization of an address called a addresses are the ones used during the HIP base exchange [2].
"locator". A locator specifies a point-of-attachment to the network
but may also include additional end-to-end tunneling or per-host
demultiplexing context that affects how packets are handled below the
logical HIP sublayer. This generalization is useful because IP
addresses alone may not be sufficient to describe how packets should
be handled below HIP. For example, in a host multihoming context,
certain IP addresses may need to be associated with certain ESP SPIs,
to avoid violation of the ESP anti-replay window [2]. Addresses may
also be affiliated with transport ports in certain tunneling
scenarios. Or locators may merely be traditional network addresses.
Using the locator concept, this document specifies extensions to HIP
to allow a mobile host to directly inform a correspondent host, with
whom the host has an active HIP association, of a locator change.
The extensions consist of a new LOCATOR parameter for use in HIP
messages, packet processing procedures for using HIP messages to
securely notify the peer of a locator change, and additional
procedures such as an address check mechanism.
When using ESP, since the SAs are not bound to IP addresses, 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. However, unless the host is
sufficiently trusted by its peers, 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.
A related operational configuration is host multihoming, in which a This document defines a generalized LOCATOR parameter for use in HIP
host has multiple locators simultaneously rather than sequentially as messages. The LOCATOR parameter allows a HIP host to notify a peer
in the case of mobility. By using the locator parameter defined about alternate addresses at which it is reachable. The LOCATORs may
herein, a host can inform its peers of additional (multiple) locators be merely IP addresses, or they may have additional multiplexing and
at which it can be reached, and can declare a particular locator as a demultiplexing context to aid the packet handling in the lower
"preferred" locator. Although this document defines a mechanism for layers. For instance, an IP address may need to be paired with an
multihoming, it does not define associated policies such as which ESP SPI so that packets are sent on the correct SA for a given
locators to choose when more than one pair is available, the address.
operation of simultaneous mobility and multihoming, and the
implications of multihoming on transport protocols and ESP
anti-replay windows. Additional definition of HIP-based multihoming
is expected to be part of a future document.
Due to the danger of flooding attacks (see [3]), the peers must This document also specifies the messaging and elements of procedure
always check the reachability of the host at a new IP address, unless for end-host mobility of a HIP host-- the sequential change in
a sufficient level of trust exists between the hosts. The preferred IP address used to reach a host. In particular, message
reachability check is implemented by the challenger sending some flows to enable successful host mobility, including address
piece of unguessable information to the new address, and waiting for verification methods, are defined herein. However, while the same
some acknowledgment from the responder that indicates reception of LOCATOR parameter is intended to support host multihoming (parallel
the information at the new address. This may include exchange of a support of a number of addresses), and experimentation is encouraged,
nonce, or generation of a new SPI and observing data arriving on the detailed elements of procedure for host multihoming are left for
new SPI. 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, end-host and
site multi-homing with legacy hosts, and NAT traversal. In these site multihoming with legacy hosts, simultaneous mobility of both
situations there is a need for some helper functionality in the hosts, and NAT traversal. In these situations there is a need for
network. Such functionality is out of scope of this document. some helper functionality in the network, such as a HIP Rendezvous
server [3]. Such functionality is out of scope of this document.
Finally, making underlying IP mobility transparent to the transport Finally, making underlying IP mobility transparent to the transport
layer has implications on the proper response of transport congestion layer has implications on the proper response of transport congestion
control, path MTU selection, and QoS. Transport-layer mobility control, path MTU selection, and QoS. Transport-layer mobility
triggers, and the proper transport response to a HIP mobility or triggers, and the proper transport response to a HIP mobility or
multi-homing address change, are outside the scope of this document. multihoming address change, are outside the scope of this document.
2. Conventions used in this document 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 [4]. document are to be interpreted as described in RFC2119 [6].
3. Terminology
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
address and end-to-end identifiers such as an ESP SPI. It may address and end-to-end identifiers such as an ESP SPI. It may
also include transport port numbers or IPv6 Flow Labels as also include transport port numbers or IPv6 Flow Labels as
demultiplexing context, or it may simply be a network address. demultiplexing context, or it may simply be a network address.
Address. A name that denotes a point-of-attachment to the network. Address. A name that denotes a point-of-attachment to the network.
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. With respect to a given peer, a host always has one active Preferred locator. A locator on which a host prefers to receive data.
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.
New preferred locator. A new preferred locator sent by a host to its
peers. The reachability of the new preferred locator often needs
to be verified before it can be put into use. Consequently, there
may simultaneously be an active preferred locator, being used, and
a new preferred locator, the reachability of which is being
verified.
4. LOCATOR parameter format
The LOCATOR parameter is a critical parameter as defined by [1]. The
LOCATOR parameter is also abbreviated as "LOC" in the figures herein.
It consists of the standard HIP parameter Type and Length fields,
plus one or more locator sub-parameters. Each Locator sub-parameter
contains a Traffic Type, Locator Type, Locator Length, Preferred
Locator bit, Locator Lifetime, and a Locator encoding.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Traffic Type | Locator Type | Locator Length | Reserved |P|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Locator Lifetime |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Locator |
| |
| |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. .
. .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Traffic Type | Locator Type | Locator Length | Reserved |P|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Locator Lifetime |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Locator |
| |
| |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type: 3
Length: Length in octets, excluding Type and Length fields, and
excluding padding.
Traffic Type: Defines whether the locator pertains to HIP signaling,
user data, or both.
Locator Type: Defines the semantics of the Locator field.
Locator Length: Defines the length of the Locator field, in units of
4-byte words (Locators up to a maximum of 4*255 bytes are
supported).
Reserved: Zero when sent, ignored when received.
P: Preferred locator. Set to one if the locator is preferred for
that Traffic Type; otherwise set to zero.
Locator Lifetime: Locator lifetime, in seconds.
Locator: The locator whose semantics and encoding are indicated by
the Locator Type field. All Locator sub-fields are integral
multiples of four bytes in length.
The Locator Lifetime indicates how long the following locator is
expected to be valid. The lifetime is expressed in seconds. Each
locator MUST have a non-zero lifetime. The address is expected to
become deprecated when the specified number of seconds has passed
since the reception of the message. A deprecated address SHOULD NOT
be used as an destination address if an alternate (non-deprecated) is
available and has sufficient scope.
4.1 Traffic Type and Preferred Locator
The following Traffic Type values are defined:
0: Both signaling (HIP control packets) and user data.
1: Signaling packets only.
2: Data packets only.
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",
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
both "0" and "2"), the more specific Traffic Type rule applies. By
default, the IP addresses used in the base exchange are preferred
locators for both signaling and user data, unless a new preferred
locator supersedes them. If no locators are indicated as preferred
for a given Traffic Type, the implementation may use an arbitrary
locator from the set of active locators.
4.2 Locator Type and Locator
The following Locator Type values are defined, along with the
associated semantics of the Locator field:
0: An IPv6 address or an IPv4-in-IPv6 format IPv4 address [5] (128
bits long).
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
128 bits).
4.3 UPDATE packet with included LOCATOR
A number of combinations of parameters in an UPDATE packet are
possible (e.g., see Section 6). Any UPDATE packet that includes a
LOCATOR parameter SHOULD include both an HMAC and a HIP_SIGNATURE
parameter.>
5. Overview of HIP basic mobility and multi-homing functionality
HIP mobility and multi-homing is fundamentally based on the HIP
architecture [3], 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 [1] is expected to be commonly
used with the ESP Transport Format [6] 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 Informing the peer about multiple or changed locator(s)
This document specifies a new HIP protocol parameter, the LOCATOR
parameter (see Section 4), that allows the hosts to exchange
information about their locator(s), and any changes in their
locator(s). The logical structure created with LOCATOR parameters
has three levels: hosts, Security Associations (SAs) indexed by
Security Parameter Indices (SPIs), and addresses.
The relation between these entities for an association negotiated as
defined in the base specification [1] and ESP transform [6] is
illustrated in Figure 2.
-<- SPI1a -- -- SPI2a ->-
host1 < > addr1a <---> addr2a < > host2
->- SPI2a -- -- SPI1a -<-
Figure 2: Relation between hosts, SPIs, and addresses (base
specification)
In Figure 2, host1 and host2 negotiate two unidirectional SAs, and
each host selects the SPI value for its inbound SA. The addresses
addr1a and addr2a are the source addresses that each host uses in the
base HIP exchange. These are the "preferred" (and only) addresses
conveyed to the peer for each SA; even though packets sent to any of
the hosts' interfaces can arrive on an inbound SPI, when a host sends
packets to the peer on an outbound SPI, it knows of a single
destination address associated with that outbound SPI (for host1, it
sends a packet on SPI2a to addr2a to reach host2), unless other
mechanisms exist to learn of new addresses.
In general, the bindings that exist in an implementation Credit Based Authorization. A host must must verify a mobile or
corresponding to this draft can be depicted as shown in Figure 3. In multi-homed peer's reachability at a new locator. Credit-Based
this figure, a host can have multiple inbound SPIs (and, not shown, Authorization authorizes the peer to receive a certain amount of
multiple outbound SPIs) between itself and another host. data at the new locator before the result of such verification is
Furthermore, each SPI may have multiple addresses associated with it. known.
These addresses bound to an SPI are not used as SA selectors.
Rather, the addresses are those addresses that are provided to the
peer host, as hints for which addresses to use to reach the host on
that SPI. The LOCATOR parameter allows for IP addresses and SPIs to
be combined to form generalized locators. The LOCATOR parameter is
used to change the set of addresses that a peer associates with a
particular SPI.
address11
/
SPI1 - address12
/
/ address21
host -- SPI2 <
\ address22
\
SPI3 - address31
\
address32
Figure 3: Relation between hosts, SPIs, and addresses (general case)
A host may establish any number of security associations (or SPIs)
with a peer. The main purpose of having multiple SPIs is to group
the addresses into collections that are likely to experience fate
sharing. For example, if the host needs to change its addresses on
SPI2, it is likely that both address21 and address22 will
simultaneously become obsolete. In a typical case, such SPIs may
correspond with physical interfaces; see below. Note, however, that
especially in the case of site multi-homing, one of the addresses may
become unreachable while the other one still works. In the typical
case, however, this does not require the host to inform its peers
about the situation, since even the non-working address still
logically exists.
A basic property of HIP SAs is that the inbound IP address is not
used as a selector for the SA. Therefore, in Figure 3, it may seem
unnecessary for address31, for example, to be associated only with
SPI3-- in practice, a packet may arrive to SPI1 via destination
address address31 as well. However, the use of different source and
destination addresses typically leads to different paths, with
different latencies in the network, and if packets were to arrive via
an arbitrary destination IP address (or path) for a given SPI, the
reordering due to different latencies may cause some packets to fall
outside of the ESP anti-replay window. For this reason, HIP provides
a mechanism to affiliate destination addresses with inbound SPIs, if
there is a concern that anti-replay windows might be violated
otherwise. In this sense, we can say that a given inbound SPI has an
"affinity" for certain inbound IP addresses, and this affinity is
communicated to the peer host. Each physical interface SHOULD have a
separate SA, unless the ESP anti-replay window is loose.
Moreover, even if the destination addresses used for a particular SPI
are held constant, the use of different source interfaces may also
cause packets to fall outside of the ESP anti-replay window, since
the path traversed is often affected by the source address or
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
SHOULD consistently use the same source interface when sending to a
particular destination IP address and SPI. For this reason, a host
may find it useful to change its SPI or at least reset its ESP
anti-replay window when the peer host readdresses.
An address may appear on more than one SPI. This creates no
ambiguity since the receiver will ignore the IP addresses as SA
selectors anyway.
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 3. Protocol Model
receiver will respond with an UPDATE acknowledgment. If the LOCATOR
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
to activate a new address. The use of LOCATOR in a NOTIFY message
may not be compatible with middleboxes.
5.2 Address verification 3.1 Operating Environment
When a HIP host receives a set of locators from another HIP host in a The Host Identity Protocol (HIP) [2] is a key establishment and
LOCATOR, it does not necessarily know whether the other host is parameter negotiation protocol. Its primary applications are for
actually reachable at the claimed addresses. In fact, a malicious authenticating host messages based on host identities, and
peer host may be intentionally giving bogus addresses in order to establishing security associations (SAs) for ESP transport format [5]
cause a packet flood towards the given addresses [9]. Thus, before and possibly other protocols in the future.
the HIP host can actually use a new address, it must first check that
the peer is reachable at the new address.
A second benefit of performing an address check is to allow any +--------------------+ +--------------------+
possible middleboxes in the network along the new path to obtain the | | | |
peer host's inbound SPI. | +------------+ | | +------------+ |
| | Key | | HIP | | Key | |
| | Management | <-+-----------------------+-> | Management | |
| | Process | | | | Process | |
| +------------+ | | +------------+ |
| ^ | | ^ |
| | | | | |
| v | | v |
| +------------+ | | +------------+ |
| | IPsec | | ESP | | IPsec | |
| | Stack | <-+-----------------------+-> | Stack | |
| | | | | | | |
| +------------+ | | +------------+ |
| | | |
| | | |
| Initiator | | Responder |
+--------------------+ +--------------------+
A simple technique to verify addresses is to send an UPDATE to the Figure 1: HIP deployment model
host at the new address. The UPDATE packet SHOULD include a nonce,
unguessable by anyone not on the path to the new address, that forces
the host to reply in a manner that confirms reception of the nonce.
One direct way to perform this is to include an ECHO_REQUEST
parameter with some piece of unguessable information such as a random
number. If the host is sending a NES parameter, the ECHO_REQUEST MAY
contain the new SPI, for example. If the peer host is rekeying by
sending an UPDATE with NES to the new address, the arrival of data on
the new SPI can also be used to verify the address.
If middlebox traversal is possible along the path, and the peer host The general deployment model for HIP is shown above, assuming
is not rekeying, the peer host SHOULD include a SPI parameter as part operation in an end-to-end fashion. This document specifies
of its UPDATE, with the SPI corresponding to its active inbound SPI. extensions to the HIP protocol to enable end-host mobility and
It is not specified how a host knows whether or not middleboxes might multihoming. In a nutshell, the HIP protocol can carry new
lie on its path, so a conservative assumption may be to always addressing information to the peer and can enable direct
include the SPI parameter. authentication of the message via a signature based on its host
identity. This document specifies the format of this new addressing
(LOCATOR) parameter, the procedures for sending and processing this
parameter to enable basic host mobility, and procedures for a
concurrent address verification mechanism.
In certain networking scenarios, hosts may be trusted enough to 3.1.1 Locator
bypass performing address verification. In such a case, the host MAY
bypass the address verification step and put the addresses into
immediate service. Note that this may not be compatible with
middlebox traversal.
5.3 Preferred locator This document defines a generalization of an address called a
"locator". A locator specifies a point-of-attachment to the network
but may also include additional end-to-end tunneling or per-host
demultiplexing context that affects how packets are handled below the
logical HIP sublayer of the stack. This generalization is useful
because IP addresses alone may not be sufficient to describe how
packets should be handled below HIP. For example, in a host
multihoming context, certain IP addresses may need to be associated
with certain ESP SPIs, to avoid violation of the ESP anti-replay
window [4]. Addresses may also be affiliated with transport ports in
certain tunneling scenarios. Or locators may merely be traditional
network addresses.
When a host has multiple locators, the peer host must decide upon 3.1.2 Mobility
which to use for outbound packets. It may be that a host would
prefer to receive data on a particular inbound interface. HIP allows
a particular locator to be designated as a preferred locator, and
communicated to the peer (see Section 4).
In general, when multiple locators are used for a session, there is When a host moves to another address, it notifies its peer of the new
the question of using multiple locators for failover only or for address by sending a HIP UPDATE packet containing a LOCATOR
load-balancing. Due to the implications of load-balancing on the parameter. This UPDATE packet is acknowledged by the peer, and is
transport layer that still need to be worked out, this draft assumes protected by retransmission. The peer can authenticate the contents
that multiple locators are used primarily for failover. An of the UPDATE packet based on the signature and keyed hash of the
implementation may use ICMP interactions, reachability checks, or packet. The host may at the same time decide to rekey its security
other means to detect the failure of a locator. 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].
5.4 Locator data structure and status When using ESP Transport Format [5], 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. 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.
In a typical implementation, each outgoing locator is represented as 3.1.3 Multihoming
a piece of state that contains the following data:
the actual bit pattern representing the locator,
lifetime (seconds),
status (UNVERIFIED, ACTIVE, DEPRECATED).
The status is used to track the reachability of the address embedded
within the LOCATOR parameter:
UNVERIFIED indicates that the reachability of the address has not
been verified yet,
ACTIVE indicates that the reachability of the address has been
verified and the address has not been deprecated,
DEPRECATED indicates that the locator lifetime has expired
The following state changes are allowed: A related operational configuration is host multihoming, in which a
UNVERIFIED to ACTIVE The reachability procedure completes host has multiple locators simultaneously rather than sequentially as
successfully. in the case of mobility. By using the locator parameter defined
UNVERIFIED to DEPRECATED The locator lifetime expires while it is herein, a host can inform its peers of additional (multiple) locators
UNVERIFIED. at which it can be reached, and can declare a particular locator as a
ACTIVE to DEPRECATED The locator lifetime expires while it is ACTIVE. "preferred" locator. Although this document defines a mechanism for
ACTIVE to UNVERIFIED There has been no traffic on the address for multihoming, it does not define associated policies and procedure
some time, and the local policy mandates that the address details such as which locators to choose when more than one pair is
reachability must be verified again before starting to use it available, the operation of simultaneous mobility and multihoming,
again. and the implications of multihoming on transport protocols and ESP
DEPRECATED to UNVERIFIED The host receives a new lifetime for the anti-replay windows. Additional definition of HIP-based multihoming
locator. is expected to be part of a future document.
If a host is verifying reachability with another host, a DEPRECATED
address MUST NOT be changed to ACTIVE without first verifying its
reachability. If reachability is not being verified, then the
UNVERIFIED state is a transient state that transitions immediately to
ACTIVE.
6. 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
where the HIP mobility and multi-homing facility is useful. These where the HIP mobility and multihoming facility is useful. These
scenarios assume that HIP is being used with the ESP Transform, scenarios assume that HIP is being used with the ESP Transform,
although other scenarios may be defined in the future. To understand although other scenarios may be defined in the future. To understand
these usage scenarios, the reader should be at least minimally these usage scenarios, the reader should be at least minimally
familiar with the HIP protocol specification [1]. However, for the familiar with the HIP protocol specification [2]. However, for the
(relatively) uninitiated reader it is most important to keep in mind (relatively) uninitiated reader it is most important to keep in mind
that in HIP the actual payload traffic is protected with ESP, and that in HIP the actual payload traffic is protected with ESP, and
that the ESP SPI acts as an index to the right host-to-host context. that the ESP SPI acts as an index 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 one host,
called the mobile host, informs another host, called the peer host, called the mobile host, informs another host, called the peer host,
about changes of IP addresses on affected SPIs. The readdressing about changes of IP addresses on affected SPIs. The readdressing
exchange is designed to be piggybacked on a number of existing HIP exchange is designed to be piggybacked on existing HIP exchanges.
exchanges. The main packets on which the LOCATOR parameters are The main packets on which the LOCATOR parameters are expected to be
expected to be carried on are UPDATE packets. However, some carried are UPDATE packets. However, some implementations may want
implementations may want to experiment with sending LOCATOR to experiment with sending LOCATOR parameters also on other packets,
parameters also on other packets, such as R1, I2, and NOTIFY. such as R1, I2, and NOTIFY.
6.1 Mobility with single SA pair 3.2.1 Mobility with single SA pair
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, and
a single pair of SAs (one inbound, one outbound). a single pair of SAs (one inbound, one outbound).
1. The mobile host is disconnected from the peer host for a brief 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. period of time while it switches from one IP address to another.
Upon obtaining a new IP address, the mobile host sends a LOCATOR Upon obtaining a new IP address, the mobile host sends a LOCATOR
parameter to the peer host in an UPDATE message. The LOCATOR parameter to the peer host in an UPDATE message. The LOCATOR
indicates the new IP address and the SPI associated with the new indicates the new IP address and the SPI associated with the new
IP address by using a Locator Type of "1", the locator lifetime, IP address by using a Locator Type of "1", the locator lifetime,
and whether the new locator is a preferred locator. The mobile and whether the new locator is a preferred locator. The mobile
host may optionally send a NES to create a new inbound SA, in host may optionally send an ESP_INFO to create a new inbound SA,
which case it transitions to state REKEYING. In this case, the in which case it transitions to state REKEYING. In this case,
Locator contains the new SPI to use. Otherwise, the existing SPI the Locator contains the new SPI to use. Otherwise, the existing
is identified in the Locator parameter, and the host waits for SPI is identified in the Locator parameter, and the host waits
its UPDATE to be acknowledged. for its UPDATE to be acknowledged.
2. Depending on whether the mobile host initiated a rekey, and on 2. Depending on whether the mobile host initiated a rekey, and on
whether the peer host itself wants to rekey or verify the mobile whether the peer host itself wants to rekey, a number of
host's new address, a number of responses are possible. Figure 4 responses are possible. Figure 2 illustrates an exchange for
illustrates an exchange for which neither side initiates a which neither side initiates a rekeying, but for which the peer
rekeying, but for which the peer host performs an address check. host performs an address check. If the mobile host is rekeying,
If the peer host chooses not to perform an address check, the the peer will also rekey, as shown in Figure 3. If the mobile
UPDATE that it sends will only acknowledge the mobile host's host did not decide to rekey but the peer desires to do so, then
update but will not solicit a response from the mobile host. If it initiates a rekey as illustrated in Figure 4. The UPDATE
the mobile host is rekeying, the peer will also rekey, as shown messages sent from the peer back to the mobile are sent to the
in Figure 5. If the mobile host did not decide to rekey but the newly advertised address.
peer desires to do so, then it initiates a rekey as illustrated
in Figure 6. The UPDATE messages sent from the peer back to the 3. While the peer host is verifying the new address, the address is
mobile are sent to the newly advertised address. marked as UNVERIFIED in the interim. Once it has received a
3. If the peer host is verifying the new address, the address is correct reply to its UPDATE challenge, or optionally, data on the
marked as UNVERIFIED in the interim. Once it has successfully new SA, it marks the new address as ACTIVE and removes the old
received a reply to its UPDATE challenge, or optionally, data on address.
the new SA, it marks the new address as ACTIVE and removes the
old address.
Mobile Host Peer Host Mobile Host Peer Host
UPDATE(LOC, SEQ) UPDATE(ESP_INFO, LOC, SEQ)
-----------------------------------> ----------------------------------->
UPDATE(SPI, SEQ, ACK, ECHO_REQUEST) UPDATE(ESP_INFO, SEQ, ACK, ECHO_REQUEST)
<----------------------------------- <-----------------------------------
UPDATE(ACK, ECHO_RESPONSE) UPDATE(ACK, ECHO_RESPONSE)
-----------------------------------> ----------------------------------->
Figure 4: Readdress without rekeying, but with address check Figure 2: Readdress without rekeying, but with address check
Mobile Host Peer Host Mobile Host Peer Host
UPDATE(LOC, NES, SEQ, [DIFFIE_HELLMAN]) UPDATE(ESP_INFO, LOC, SEQ, [DIFFIE_HELLMAN])
-----------------------------------> ----------------------------------->
UPDATE(NES, 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: Readdress with mobile-initiated rekey Figure 3: Readdress with mobile-initiated rekey
Mobile Host Peer Host Mobile Host Peer Host
UPDATE(LOC, SEQ) UPDATE(LOC, SEQ)
-----------------------------------> ----------------------------------->
UPDATE(NES, SEQ, ACK, [DIFFIE_HELLMAN], ECHO_REQUEST) UPDATE(ESP_INFO, SEQ, ACK, [DIFFIE_HELLMAN], ECHO_REQUEST)
<----------------------------------- <-----------------------------------
UPDATE(NES, SEQ, ACK, [DIFFIE_HELLMAN,] ECHO_RESPONSE) UPDATE(ESP_INFO, SEQ, ACK, [DIFFIE_HELLMAN,] ECHO_RESPONSE)
-----------------------------------> ----------------------------------->
UPDATE(ACK) UPDATE(ACK)
<----------------------------------- <-----------------------------------
Figure 6: Readdress with peer-initiated rekey Figure 4: Readdress with peer-initiated rekey
Hosts that use link-local addresses as source addresses in their HIP Hosts that use link-local addresses as source addresses in their HIP
handshakes may not be reachable by a mobile peer. Such hosts SHOULD handshakes may not be reachable by a mobile peer. Such hosts SHOULD
provide a globally routable address either in the initial handshake provide a globally routable address either in the initial handshake
or via the LOCATOR parameter. or via the LOCATOR parameter.
6.2 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. The host may notify the peer host of the additional
interface(s) by using the LOCATOR parameter. To avoid problems with interface(s) by using the LOCATOR parameter. To avoid problems with
the ESP anti-replay window, a host SHOULD use a different SA for each the ESP anti-replay window, a host SHOULD use a different SA for each
interface used to receive packets from the peer host. interface 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 a NES 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 To add both an additional interface and SA, the host sends a LOCATOR
with a NES. The host uses the same (new) SPI value in the LOCATOR with an ESP_INFO. The host uses the same (new) SPI value in the
and both the "Old SPI" and "New SPI" values in the NES-- this LOCATOR and both the "Old SPI" and "New SPI" values in the ESP_INFO--
indicates to the peer that the SPI is not replacing an existing SPI. this indicates to the peer that the SPI is not replacing an existing
The multihomed host transitions to state REKEYING, waiting for a NES SPI. The multihomed host transitions to state REKEYING, waiting for
from the peer and an ACK of its own UPDATE. As in the mobility case, a ESP_INFO from the peer and an ACK of its own UPDATE. As in the
the peer host can perform an address check while it is rekeying. mobility case, the peer host must perform an address check while it
Figure 7 illustrates the basic packet exchange. is rekeying. Figure 5 illustrates the basic packet exchange.
Multi-homed Host Peer Host Multi-homed Host Peer Host
UPDATE(LOC, NES, SEQ, [DIFFIE_HELLMAN]) UPDATE(ESP_INFO, LOC, SEQ, [DIFFIE_HELLMAN])
-----------------------------------> ----------------------------------->
UPDATE(NES, SEQ, ACK, [DIFFIE_HELLMAN,] ECHO_REQUEST) UPDATE(ESP_INFO, SEQ, ACK, [DIFFIE_HELLMAN,] ECHO_REQUEST)
<----------------------------------- <-----------------------------------
UPDATE(ACK, ECHO_RESPONSE) UPDATE(ACK, ECHO_RESPONSE)
-----------------------------------> ----------------------------------->
Figure 7: Basic multihoming scenario Figure 5: Basic multihoming scenario
For the case in which multiple locators are advertised in a LOCATOR, 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 the peer does not need to send ACK for the UPDATE(LOCATOR) in every
subsequent message used for the address check procedure of the subsequent message used for the address check procedure of the
multiple locators. Therefore, a sample packet exchange might look as multiple locators. Therefore, a sample packet exchange might look as
shown in Figure 8. shown in Figure 6.
Multi-homed Host Peer Host Multi-homed Host Peer Host
UPDATE(LOC(addr_1,addr_2), SEQ) UPDATE(LOC(addr_1,addr_2), SEQ)
-----------------------------------> ----------------------------------->
UPDATE(ACK) UPDATE(ACK)
<----------------------------------- <-----------------------------------
sent to addr_1:UPDATE(SPI, SEQ, ECHO_REQUEST) sent to addr_1:UPDATE(ESP_INFO, SEQ, ECHO_REQUEST)
<----------------------------------- <-----------------------------------
UPDATE(ACK, ECHO_RESPONSE) UPDATE(ACK, ECHO_RESPONSE)
-----------------------------------> ----------------------------------->
sent to addr_2:UPDATE(SPI, SEQ, ECHO_REQUEST) sent to addr_2:UPDATE(ESP_INFO, SEQ, ECHO_REQUEST)
<----------------------------------- <-----------------------------------
UPDATE(ACK, ECHO_RESPONSE) UPDATE(ACK, ECHO_RESPONSE)
-----------------------------------> ----------------------------------->
Figure 8: LOCATOR with multiple addresses 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, a host uses the destination address of the UPDATE
containing LOCATOR as the local address to which the LOC plus NES is containing LOCATOR as the local address to which the LOC plus
targeted. Hosts may send LOCATOR with the same IP address to ESP_INFO is targeted. Hosts may send LOCATOR with the same IP
different peer addresses-- this has the effect of creating multiple address to different peer addresses-- this has the effect of creating
inbound SAs implicitly affiliated with different source addresses. multiple inbound SAs implicitly affiliated with different source
addresses.
When rekeying in a multihoming situation in which there is an When rekeying in a multihoming situation in which there is an
asymmetric number of SAs between two hosts, a respondent to the NES/ asymmetric number of SAs between two hosts, a respondent to the
UPDATE procedure may have some ambiguity as to which inbound SA it ESP_INFO/UPDATE procedure may have some ambiguity as to which inbound
should update in response to the peer's UPDATE. In such a case, the SA it should update in response to the peer's UPDATE. In such a
host SHOULD choose an SA corresponding to the inbound interface on case, the host SHOULD choose an SA corresponding to the inbound
which the UPDATE was received. interface on which the UPDATE was received.
6.3 Site multi-homing 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 6.2. Note that a single addresses, described above in Section 3.2.2. Note that a single
interface may experience site multi-homing 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 to further align it with the requirements of the
multi6 working group. multi6 working group.
6.4 Dual host multi-homing 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 9, 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 a LOCATOR to
host2 located at addr2a, and a new set of SPIs would be added between host2 located at addr2a, and a new set of SPIs would be added between
hosts 1 and 2 (call them SPI1b and SPI2b). Next, consider host2 hosts 1 and 2 (call them SPI1b and SPI2b). Next, consider host2
deciding to add addr2b to the relationship. host2 now has a choice deciding to add addr2b to the relationship. host2 now has a choice of
of which of host1's addresses to initiate LOCATOR to. It may choose which of host1's addresses to initiate LOCATOR to. It may choose to
to initiate a LOCATOR to addr1a, addr1b, or both. If it chooses to initiate a LOCATOR to addr1a, addr1b, or both. If it chooses to send
send to both, then a full mesh (four SA pairs) of SAs would exist to both, then a full mesh (four SA pairs) of SAs would exist between
between the two hosts. This is the most general case; it may be the two hosts. This is the most general case; it may be often the
often the case that hosts primarily establish new SAs only with the case that hosts primarily establish new SAs only with the peer's
peer's preferred locator. The readdressing protocol is flexible preferred locator. The readdressing protocol is flexible enough to
enough to accommodate this choice. accommodate this choice.
-<- SPI1a -- -- SPI2a ->- -<- SPI1a -- -- SPI2a ->-
host1 < > addr1a <---> addr2a < > host2 host1 < > addr1a <---> addr2a < > host2
->- SPI2a -- -- SPI1a -<- ->- SPI2a -- -- SPI1a -<-
addr1b <---> addr2b addr1b <---> addr2b
Figure 9: 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
6.5 Combined mobility and multi-homing 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 NES should be flexible enough to handle most The use of LOCATOR plus ESP_INFO should be flexible enough to handle
such scenarios, although more complicated scenarios have not been most such scenarios, although more complicated scenarios have not
studied so far. been studied so far.
6.6 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 be acknowledged anyway, and the HIP state may
time out. time out.
6.7 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.
6.8 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, the Initiator SHOULD send the I2 packet to the new parameters with a new preferred locator, the Initiator SHOULD
preferred locator. The I1 destination address and the new preferred directly set the new preferred locator to status ACTIVE without
locator may be identical. performing address verification first, and MUST send the I2 packet to
the new preferred locator. The I1 destination address and the new
preferred locator may be identical. All new non-preferred locators
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 SPI parameter I2 with new SPI in ESP_INFO parameter
-----------------------------------> ----------------------------------->
(process normally) (process normally)
R2 R2
<----------------------------------- <-----------------------------------
(process normally) (process normally)
Figure 10: 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 on whether there was LOCATOR parameter(s) 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. preferred locator SHOULD be identical to the I2 source address. If
the I2 packet contains LOCATOR parameters, all new locators must
undergo address verification as usual. If any of these locators is a
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 SPI parameter R2 with new SPI in ESP_INFO parameter
<----------------------------------- <-----------------------------------
(process normally) (process normally)
data on new SA data on new SA
------------------------------------> ------------------------------------>
(process normally) (process normally)
Figure 11: LOCATOR inclusion in I2 Figure 9: LOCATOR inclusion in I2
7. Processing rules 3.3 Other Considerations
7.1 Sending LOCATORs 3.3.1 Address Verification
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
actually reachable at the claimed addresses. In fact, a malicious
peer host may be intentionally giving bogus addresses in order to
cause a packet flood towards the target addresses [10]. Likewise,
viral software may have compromised the peer host, programming it to
redirect packets to the target addresses. Thus, the HIP host must
first check that the peer is reachable at the new address.
An additional potential benefit of performing address verification is
to allow middleboxes in the network along the new path to obtain the
peer host's inbound SPI.
Address verification is implemented by the challenger sending some
piece of unguessable information to the new address, and waiting for
some acknowledgment from the responder that indicates reception of
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
new SPI.
3.3.2 Credit-Based Authorization
Credit-Based Authorization allows a host to securely use a new
locator even though the peer's reachability at the address embedded
in this locator has not yet been verified. This is accomplished
based on the following three hypotheses:
1. A flooding attacker typically seeks to somehow multiply the
packets it generates itself for the purpose of its attack because
bandwidth is an ample resource for many attractive victims.
2. An attacker can always cause unamplified flooding by sending
packets to its victim directly.
3. Consequently, the additional effort required to set up a
redirection-based flooding attack would pay off for the attacker
only if amplification could be obtained this way.
On this basis, rather than eliminating malicious packet redirection
in the first place, Credit-Based Authorization prevents any
amplification that can be reached through it. This is accomplished
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
flooding attacks thus become less attractive than, e.g., pure direct
flooding, where the attacker itself sends bogus packets to the
victim.
Figure 10 illustrates Credit-Based Authorization: Host B measures
the bytes recently received from peer A and, when A readdresses,
sends packets to A's new, unverified address as long as the sum of
their sizes does not exceed the measured, received data volume. When
insufficient credit is left, B stops sending further packets to A
until A's address becomes ACTIVE. The address changes may be due to
mobility, due to multihoming, or due to any other reason.
+-------+ +-------+
| A | | B |
+-------+ +-------+
| |
address |------------------------->| credit += size(packet)
ACTIVE | |
|------------------------->| credit += size(packet)
|<-------------------------| don't change credit
| |
+ address change |
address |<-------------------------| credit -= size(packet)
UNVERIFIED |------------------------->| credit += size(packet)
|<-------------------------| credit -= size(packet)
| |
|<-------------------------| credit -= size(packet)
| X credit < size(packet)=> drop!
| |
+ address change |
address | |
ACTIVE |<-------------------------| don't change credit
| |
Figure 10: Readdressing Scenario
3.3.3 Preferred locator
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
prefer to receive data on a particular inbound interface. HIP allows
a particular locator to be designated as a preferred locator, and
communicated to the peer (see Section 4).
In general, when multiple locators are used for a session, there is
the question of using multiple locators for failover only or for
load-balancing. Due to the implications of load-balancing on the
transport layer that still need to be worked out, this draft assumes
that multiple locators are used primarily for failover. An
implementation may use ICMP interactions, reachability checks, or
other means to detect the failure of a locator.
3.3.4 Interaction with Security Associations
This document specifies a new HIP protocol parameter, the LOCATOR
parameter (see Section 4), that allows the hosts to exchange
information about their locator(s), and any changes in their
locator(s). The logical structure created with LOCATOR parameters
has three levels: hosts, Security Associations (SAs) indexed by
Security Parameter Indices (SPIs), and addresses.
The relation between these entities for an association negotiated as
defined in the base specification [2] and ESP transform [5] is
illustrated in Figure 11.
-<- SPI1a -- -- SPI2a ->-
host1 < > addr1a <---> addr2a < > host2
->- SPI2a -- -- SPI1a -<-
Figure 11: Relation between hosts, SPIs, and addresses (base
specification)
In Figure 11, host1 and host2 negotiate two unidirectional SAs, and
each host selects the SPI value for its inbound SA. The addresses
addr1a and addr2a are the source addresses that each host uses in the
base HIP exchange. These are the "preferred" (and only) addresses
conveyed to the peer for each SA; even though packets sent to any of
the hosts' interfaces can arrive on an inbound SPI, when a host sends
packets to the peer on an outbound SPI, it knows of a single
destination address associated with that outbound SPI (for host1, it
sends a packet on SPI2a to addr2a to reach host2), unless other
mechanisms exist to learn of new addresses.
In general, the bindings that exist in an implementation
corresponding to this draft can be depicted as shown in Figure 12.
In this figure, a host can have multiple inbound SPIs (and, not
shown, multiple outbound SPIs) between itself and another host.
Furthermore, each SPI may have multiple addresses associated with it.
These addresses bound to an SPI are not used as SA selectors.
Rather, the addresses are those addresses that are provided to the
peer host, as hints for which addresses to use to reach the host on
that SPI. The LOCATOR parameter allows for IP addresses and SPIs to
be combined to form generalized locators. The LOCATOR parameter is
used to change the set of addresses that a peer associates with a
particular SPI.
address11
/
SPI1 - address12
/
/ address21
host -- SPI2 <
\ address22
\
SPI3 - address31
\
address32
Figure 12: Relation between hosts, SPIs, and addresses (general case)
A host may establish any number of security associations (or SPIs)
with a peer. The main purpose of having multiple SPIs is to group
the addresses into collections that are likely to experience fate
sharing. For example, if the host needs to change its addresses on
SPI2, it is likely that both address21 and address22 will
simultaneously become obsolete. In a typical case, such SPIs may
correspond with physical interfaces; see below. Note, however, that
especially in the case of site multihoming, one of the addresses may
become unreachable while the other one still works. In the typical
case, however, this does not require the host to inform its peers
about the situation, since even the non-working address still
logically exists.
A basic property of HIP SAs is that the inbound IP address is not
used as a selector for the SA. Therefore, in Figure 12, it may seem
unnecessary for address31, for example, to be associated only with
SPI3-- in practice, a packet may arrive to SPI1 via destination
address address31 as well. However, the use of different source and
destination addresses typically leads to different paths, with
different latencies in the network, and if packets were to arrive via
an arbitrary destination IP address (or path) for a given SPI, the
reordering due to different latencies may cause some packets to fall
outside of the ESP anti-replay window. For this reason, HIP provides
a mechanism to affiliate destination addresses with inbound SPIs, if
there is a concern that anti-replay windows might be violated
otherwise. In this sense, we can say that a given inbound SPI has an
"affinity" for certain inbound IP addresses, and this affinity is
communicated to the peer host. Each physical interface SHOULD have a
separate SA, unless the ESP anti-replay window is loose.
Moreover, even if the destination addresses used for a particular SPI
are held constant, the use of different source interfaces may also
cause packets to fall outside of the ESP anti-replay window, since
the path traversed is often affected by the source address or
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
SHOULD consistently use the same source interface when sending to a
particular destination IP address and SPI. For this reason, a host
may find it useful to change its SPI or at least reset its ESP anti-
replay window when the peer host readdresses.
An address may appear on more than one SPI. This creates no
ambiguity since the receiver will ignore the IP addresses as SA
selectors anyway.
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
receiver will respond with an UPDATE acknowledgment. If the LOCATOR
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
to activate a new address. The use of LOCATOR in a NOTIFY message
may not be compatible with middleboxes.
4. LOCATOR parameter format
The LOCATOR parameter is a critical parameter as defined by [2]. The
LOCATOR parameter is also abbreviated as "LOC" in the figures herein.
It consists of the standard HIP parameter Type and Length fields,
plus one or more Locator sub-parameters. Each Locator sub-parameter
contains a Traffic Type, Locator Type, Locator Length, Preferred
Locator bit, Locator Lifetime, and a Locator encoding.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Traffic Type | Locator Type | Locator Length | Reserved |P|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Locator Lifetime |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Locator |
| |
| |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. .
. .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Traffic Type | Locator Type | Locator Length | Reserved |P|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Locator Lifetime |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Locator |
| |
| |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type: 193
Length: Length in octets, excluding Type and Length fields, and
excluding padding.
Traffic Type: Defines whether the locator pertains to HIP signaling,
user data, or both.
Locator Type: Defines the semantics of the Locator field.
Locator Length: Defines the length of the Locator field, in units of
4-byte words (Locators up to a maximum of 4*255 bytes are
supported).
Reserved: Zero when sent, ignored when received.
P: Preferred locator. Set to one if the locator is preferred for
that Traffic Type; otherwise set to zero.
Locator Lifetime: Locator lifetime, in seconds.
Locator: The locator whose semantics and encoding are indicated by
the Locator Type field. All Locator sub-fields are integral
multiples of four bytes in length.
The Locator Lifetime indicates how long the following locator is
expected to be valid. The lifetime is expressed in seconds. Each
locator MUST have a non-zero lifetime. The address is expected to
become deprecated when the specified number of seconds has passed
since the reception of the message. A deprecated address SHOULD NOT
be used as an destination address if an alternate (non-deprecated) is
available and has sufficient scope.
4.1 Traffic Type and Preferred Locator
The following Traffic Type values are defined:
0: Both signaling (HIP control packets) and user data.
1: Signaling packets only.
2: Data packets only.
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",
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
both "0" and "2"), the more specific Traffic Type rule applies. By
default, the IP addresses used in the base exchange are preferred
locators for both signaling and user data, unless a new preferred
locator supersedes them. If no locators are indicated as preferred
for a given Traffic Type, the implementation may use an arbitrary
locator from the set of active locators.
4.2 Locator Type and Locator
The following Locator Type values are defined, along with the
associated semantics of the Locator field:
0: An IPv6 address or an IPv4-in-IPv6 format IPv4 address [7] (128
bits long).
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
128 bits).
4.3 UPDATE packet with included LOCATOR
A number of combinations of parameters in an UPDATE packet are
possible (e.g., see Section 3.2). Any UPDATE packet that includes a
LOCATOR parameter SHOULD include both an HMAC and a HIP_SIGNATURE
parameter.
5. Processing rules
HIP mobility and multihoming is fundamentally based on the HIP
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
a piece of state that contains the following data:
o the actual bit pattern representing the locator,
o lifetime (seconds),
o status (UNVERIFIED, ACTIVE, DEPRECATED).
The status is used to track the reachability of the address embedded
within the LOCATOR parameter:
UNVERIFIED indicates that the reachability of the address has not
been verified yet,
ACTIVE indicates that the reachability of the address has been
verified and the address has not been deprecated,
DEPRECATED indicates that the locator lifetime has expired
The following state changes are allowed:
UNVERIFIED to ACTIVE The reachability procedure completes
successfully.
UNVERIFIED to DEPRECATED The locator lifetime expires while it is
UNVERIFIED.
ACTIVE to DEPRECATED The locator lifetime expires while it is ACTIVE.
ACTIVE to UNVERIFIED There has been no traffic on the address for
some time, and the local policy mandates that the address
reachability must be verified again before starting to use it
again.
DEPRECATED to UNVERIFIED The host receives a new lifetime for the
locator.
A DEPRECATED address MUST NOT be changed to ACTIVE without first
verifying its reachability.
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, and assumes that
the change is going to last at least for a few seconds. Rapidly the change is going to last at least for a few seconds. Rapidly
sending conflicting LOCATORs SHOULD be avoided. 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, and
whether to include any addresses on multiple SPIs. Since each SPI is whether to include any addresses on multiple SPIs. Since each SPI is
skipping to change at page 22, line 50 skipping to change at page 25, line 28
preferred for each distinct Traffic Type in the LOCATOR parameter. preferred for each distinct Traffic Type in the LOCATOR parameter.
If addresses are being added to an existing SPI, the LOCATOR If addresses are being added to an existing SPI, the LOCATOR
parameter includes the full set of valid addresses for that SPI, each parameter includes the full set of valid addresses for that SPI, each
using a Locator Type of "1" and each with the same value for SPI. using a Locator Type of "1" and each with the same value for SPI.
Any locators previously ACTIVE on that SPI that are not included in Any locators previously ACTIVE on that SPI that are not included in
the LOCATOR will be set to DEPRECATED by the receiver. the LOCATOR will be set to DEPRECATED by the receiver.
If a mobile host decides to change the SPI upon a readdress, it sends If a mobile host decides to change the SPI upon a readdress, it sends
a LOCATOR with the SPI field within the LOCATOR set to the new SPI, a LOCATOR with the SPI field within the LOCATOR set to the new SPI,
and also a NES parameter with the Old SPI field set to the previous and also an ESP_INFO parameter with the Old SPI field set to the
SPI and the New SPI field set to the new SPI. If multiple LOCATOR previous SPI and the New SPI field set to the new SPI. If multiple
and NES parameters are included, the NES MUST be ordered such that LOCATOR and ESP_INFO parameters are included, the ESP_INFO MUST be
they appear in the same order as the set of corresponding LOCATORs. ordered such that they appear in the same order as the set of
The decision as to whether to rekey and send a new Diffie-Hellman corresponding LOCATORs. The decision as to whether to rekey and send
parameter while performing readdressing is a local policy decision. a new Diffie-Hellman parameter while performing readdressing is a
local policy decision.
If new addresses and new SPIs are being created, the LOCATOR If new addresses and new SPIs are being created, the LOCATOR
parameter's SPI field contains the new SPI, and the NES parameter's parameter's SPI field contains the new SPI, and the ESP_INFO
Old SPI field and New SPI fields are both set to the new SPI, parameter's Old SPI field and New SPI fields are both set to the new
indicating that this is a new and not a replacement SPI. SPI, indicating that this is a new and not a replacement SPI.
If there are multiple LOCATOR parameters leading to a packet size If there are multiple LOCATOR parameters leading to a packet size
that exceeds the MTU, the host SHOULD send multiple packets, each that exceeds the MTU, HIP fragmentation rules as described in [2]
smaller than the MTU. In the case of R1 and I2, the additional shall apply.
packets should be UPDATE packets that are sent after the base
exchange has been completed.
7.2 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 LOCATOR parameters in any HIP
packets, excluding I1. packets, excluding I1.
When a host receives a LOCATOR parameter, it first performs the When a host receives a LOCATOR parameter, it first performs the
following operations: following operations:
1. For each locator listed in the LOCATOR parameter, check that the 1. 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 2. For each address listed in the LOCATOR parameter, check if the
address is already bound to the SPI. If the address is already address is already bound to the SPI. If the address is already
bound, its lifetime is updated. If the status of the address is bound, its lifetime is updated. If the status of the address is
DEPRECATED, the status is changed to UNVERIFIED. If the address DEPRECATED, the status is changed to UNVERIFIED. If the address
is not already bound, the address is added, and its status is set is not already bound, the address is added, and its status is set
to UNVERIFIED. Mark all addresses on the SPI that were NOT to UNVERIFIED. Mark all addresses on the SPI that were NOT
listed in the LOCATOR parameter as DEPRECATED. As a result, the listed in the LOCATOR parameter as DEPRECATED. As a result, the
SPI now contains any addresses listed in the LOCATOR parameter SPI now contains any addresses listed in the LOCATOR parameter
either as UNVERIFIED or ACTIVE, and any old addresses not listed either as UNVERIFIED or ACTIVE, and any old addresses not listed
in the LOCATOR parameter as DEPRECATED. in the LOCATOR parameter as DEPRECATED.
skipping to change at page 23, line 42 skipping to change at page 26, line 22
2. For each address listed in the LOCATOR parameter, check if the 2. For each address listed in the LOCATOR parameter, check if the
address is already bound to the SPI. If the address is already address is already bound to the SPI. If the address is already
bound, its lifetime is updated. If the status of the address is bound, its lifetime is updated. If the status of the address is
DEPRECATED, the status is changed to UNVERIFIED. If the address DEPRECATED, the status is changed to UNVERIFIED. If the address
is not already bound, the address is added, and its status is set is not already bound, the address is added, and its status is set
to UNVERIFIED. Mark all addresses on the SPI that were NOT to UNVERIFIED. Mark all addresses on the SPI that were NOT
listed in the LOCATOR parameter as DEPRECATED. As a result, the listed in the LOCATOR parameter as DEPRECATED. As a result, the
SPI now contains any addresses listed in the LOCATOR parameter SPI now contains any addresses listed in the LOCATOR parameter
either as UNVERIFIED or ACTIVE, and any old addresses not listed either as UNVERIFIED or ACTIVE, and any old addresses not listed
in the LOCATOR parameter as DEPRECATED. in the LOCATOR parameter as DEPRECATED.
3. If the LOCATOR is paired with a NES parameter, the NES parameter
is processed. If the LOCATOR is replacing the address on an 3. If the LOCATOR is paired with an ESP_INFO parameter, the ESP_INFO
existing SPI, the SPI itself may be changed-- in this case, the parameter is processed. If the LOCATOR is replacing the address
host proceeds according to HIP rekeying procedures. This case is on an existing SPI, the SPI itself may be changed-- in this case,
indicated by the NES parameter including an existing SPI in the the host proceeds according to HIP rekeying procedures. This
Old SPI field and a new SPI in the New SPI field, and the SPI case is indicated by the ESP_INFO parameter including an existing
field in the LOCATOR matching the New SPI in the NES. If instead SPI in the Old SPI field and a new SPI in the New SPI field, and
the LOCATOR corresponds to a new SPI, the NES will include the the SPI field in the LOCATOR matching the New SPI in the
same SPI in both its Old SPI and New SPI fields. 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 4. Mark all locators at the address group that were NOT listed in
the LOCATOR parameter as DEPRECATED. 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 usually requires that the host first preferred locator. This requires that the host first verifies
verifies reachability of the associated address, and only then reachability of the associated address, and only then changes the
changes the preferred locator. See Section 7.4. preferred locator. See Section 5.6.
7.3 Verifying address reachability 5.4 Verifying address reachability
A host MUST verify the reachability of an UNVERIFIED address. The
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
preferred locator. A host MAY also want to verify the reachability
of an ACTIVE address again after some time, in which case it would
set the status of the address to UNVERIFIED and reinitiate address
verification
A host typically starts the address-verification procedure by sending
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
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 ECHO_REQUEST parameter in an UPDATE message sent to the new
address. A host MAY also use other message exchanges as confirmation
of the address reachability.
A host MAY want to verify the reachability of any UNVERIFIED address
at any time. It typically does so by sending a nonce to the new
address. For example, if the host is changing its SPI and is sending
a NES to the peer, the new SPI value SHOULD 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 ECHO_REQUEST parameter
in an UPDATE message sent to the new address. A host MAY also use
other message exchanges as confirmation 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
with an I2, receiving the corresponding R2 is sufficient for marking with an I2, receiving the corresponding R2 is sufficient proof of
the Responder's primary address active. reachability for the Responder's preferred address. Since further
address verification of such address can impede the HIP base
exchange, a host MUST NOT verify reachability of a new preferred
locator that was received on a R1.
In some cases, it may be sufficient to use the arrival of data on a In some cases, it may be sufficient to use the arrival of data on a
newly advertised SA as implicit address reachability verification, newly advertised SA as implicit address reachability verification,
instead of waiting for the confirmation via a HIP packet (e.g., instead of waiting for the confirmation via a HIP packet (e.g.,
Figure 12). In this case, a host advertising a new SPI as part of Figure 14). In this case, a host advertising a new SPI as part of
its address reachability check SHOULD be prepared to receive traffic its address reachability check SHOULD be prepared to receive traffic
on the new SA. Marking the address active as a part of receiving on the new SA. Marking the address ACTIVE as a part of receiving
data on the SA is an idempotent operation, and does not cause any data on the SA is an idempotent operation, and does not cause any
harm. harm.
Mobile host Peer host Mobile host Peer host
prepare incoming SA prepare incoming SA
new SPI in R2, or UPDATE new SPI in R2, or UPDATE
<----------------------------------- <-----------------------------------
switch to new outgoing SA switch to new outgoing SA
data on new SA data on new SA
-----------------------------------> ----------------------------------->
mark address ACTIVE mark address ACTIVE
Figure 12: Address activation via use of new SA Figure 14: Address activation via use of new SA
7.4 Changing the 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
such locator is available, to continue communications until address
verification completes. Alternatively, the host MAY use the new
preferred locator while in UNVERIFIED status to the extent Credit-
Based Authorization permits. Credit-Based Authorization is explained
in Section 5.5. Once address verification succeeds, the status of
the new preferred locator changes to ACTIVE.
5.5 Credit-Based Authorization
5.5.1 Handling Payload Packets
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
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
listed as UNVERIFIED and no alternative locator with status ACTIVE is
available, the host checks whether it can send the packet to 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
the credit counter is too low, the packet MUST be discarded or
buffered until address verification succeeds. When a packet is sent
to a peer at an UNVERIFIED locator, the peer's credit counter MUST be
reduced by the size of the packet. The peer's credit counter is not
affected by packets that the host sends to an ACTIVE locator of that
peer.
Figure 15 depicts the actions taken by the host when a packet is
received. Figure 16 shows the decision chain in the event a packet
is sent.
Inbound
packet
|
| +----------------+ +---------------+
| | Increase | | Deliver |
+-----> | credit counter |-------------> | packet to |
| by packet size | | application |
+----------------+ +---------------+
Figure 15: Receiving Packets with Credit-Based Authorization
Outbound
packet
| _________________
| / \ +---------------+
| / Is the preferred \ No | Send packet |
+-----> | destination address |-------------> | to preferred |
\ UNVERIFIED? / | address |
\_________________/ +---------------+
|
| Yes
|
v
_________________
/ \ +---------------+
/ Does an ACTIVE \ Yes | Send packet |
| destination address |-------------> | to ACTIVE |
\ exist? / | address |
\_________________/ +---------------+
|
| No
|
v
_________________
/ \ +---------------+
/ Credit counter \ No | |
| >= |-------------> | Drop packet |
\ packet size? / | |
\_________________/ +---------------+
|
| Yes
|
v
+---------------+ +---------------+
| Reduce credit | | Send packet |
| counter by |----------------> | to preferred |
| packet size | | address |
+---------------+ +---------------+
Figure 16: Sending Packets with Credit-Based Authorization
5.5.2 Credit Aging
A host ensures that the credit counters it maintains for its peers
gradually decrease over time. Such "credit aging" prevents a
malicious peer from building up credit at a very slow speed and using
this, all at once, for a severe burst of redirected packets.
Credit aging may be implemented by multiplying credit counters with a
factor, CreditAgingFactor, less than one in fixed time intervals of
CreditAgingInterval length. Choosing appropriate values for
CreditAgingFactor and CreditAgingInterval is important to ensure that
a host can send packets to an address in state UNVERIFIED even when
the peer sends at a lower rate than the host itself. When
CreditAgingFactor or CreditAgingInterval are too small, the peer's
credit counter might be too low to continue sending packets until
address verification concludes.
The parameter values proposed in this document are as follows:
CreditAgingFactor 7/8
CreditAgingInterval 5 seconds
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
not exeed 500 milliseconds. Alternative credit-aging algorithms may
use other parameter values or different parameters, which may even be
dynamically established.
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 is receiving a LOCATOR parameter
that has the P-bit set. 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. Once the verification has starts to verify its reachability. The host SHOULD use a
succeeded, the preferred locator change is completed, unless a different locator listed as ACTIVE until address verification
new change has been initiated in the meantime. completes if one such locator is available. Altervatively, the
host MAY use the new preferred locator, even though in UNVERIFIED
status, to the extent Credit-Based Authorization permits. Once
address verification succeeds, the status of the new preferred
locator changes to ACTIVE and its use is no longer governed by
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. continues. If the selected address is UNVERIFIED, this includes
address verification as described above.
8. Policy considerations 6. Policy considerations
XXX: This section needs to be written. XXX: This section needs to be written.
The host may change the status of unused ACTIVE addresses into The host may change the status of unused ACTIVE addresses into
UNVERIFIED after a locally configured period of inactivity. UNVERIFIED after a locally configured period of inactivity.
9. Security Considerations 7. Security Considerations
Text contribution expected from Greg Perkins 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 cryptographically verifies the sender of a REA update, so
forging or replaying a HIP update packet is very difficult (see [2]).
Therefore, security issues reside in other attack domains. The two
we consider are malicious redirection of legitimate connections as
well as redirection-based flooding attacks using this protocol. This
can be broken down into the following:
10. IANA Considerations Impersonation attacks
11. Acknowledgments - direct conversation with the misled victim
12. References - man-in-the-middle attack
12.1 Normative references DoS attacks
[1] Moskowitz, R., "Host Identity Protocol", draft-ietf-hip-base-01 - flooding attacks (== bandwidth-exhaustion attacks)
(work in progress), October 2004.
[2] Kent, S. and R. Atkinson, "IP Encapsulating Security Payload * tool 1: direct flooding
(ESP)", RFC 2406, November 1998.
[3] Moskowitz, R., "Host Identity Protocol Architecture", * tool 2: flooding by zombies
* tool 2: redirection-based flooding
- memory-exhaustion attacks
- computational exhaustion attacks
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
HIP. In Section 7.3 we consider the security ramifications when we
have both HIP and non-HIP users.
7.1 Impersonation attacks
An attacker wishing to impersonate will try to mislead its victim
into directly communicating with them, or carry out a man in the
middle attack between the victim and the victim's desired
communication peer. Without mobility support, both attack types are
possible only if the attacker resides on the routing path between its
victim and the victim's desired communication peer, or if the
attacker tricks its victim into initiating the connection over an
incorrect routing path (e.g., by acting as a router or using spoofed
DNS entries).
The HIP extensions defined in this specification change the situation
in that they introduce an ability to redirect a connection (like
IPv6), both before and after establishment. If no precautionary
measures are taken, an attacker could misuse this feature to
impersonate a victim's peer from any arbitrary location. The
authentication and authorization mechanisms of the HIP base exchange
[2] and the signatures in the new REA update message prevent this
offense. Furthermore, ownership of a connection is securely linked
to a HIP HI/HIT. If an attacker somehow uses a bug in the
implementation or weakness in some protocol to redirect a HIP
connection, the original owner can always reclaim their connection
(they can always prove ownership of the private key associated with
their public HI).
MitM attacks are always possible if the attacker is present during
the initial HIP base exchange but once the base exchange has taken
place even a MitM cannot steal a HIP connection because it is very
difficult for an attacker to create an REA update packet (or any HIP
packet) that will be accepted as a legitimate update. Update packets
use HMAC and are signed. Even when an attacker can snoop packets to
attain the SPI and HIT/HI, they still cannot forge an update packet
without knowledge of the secret keys.
7.2 Denial of Service attacks
7.2.1 Flooding Attacks
The purpose of a denial-of-service attack is to exhaust some resource
of the victim such that the victim ceases operating correctly. A
denial-of-service attack can aim at the victim's network attachment
(flooding attack), its memory or its processing capacity. In a
flooding attack the attacker causes an excessive number of bogus or
unwanted packets to be sent to the victim, which fills their
available bandwidth. Note that the victim does not necessarily need
to be a node; it can also be an entire network. The attack basically
functions the same way in either case.
An effective DoS strategy is distributed denial of service (DDoS).
Here, the attacker conventionally distributes some viral software to
as many nodes as possible. Under the control of the attacker, the
infected nodes, or "zombies", jointly send packets to the victim.
With such an 'army', an attacker can take down even very high
bandwidth networks/victims.
With the ability to redirect connections, an attacker could realize a
DDoS attack without having to distribute viral code. Here, the
attacker initiates a large download from a server, and subsequently
redirects this download to its victim. The attacker can repeat this
with multiple servers. This threat is mitigated through reachability
checks and credit-based authorization. Both strategies do not
eliminate flooding attacks per se, but they preclude: (i) their use
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
result, the combination of a reachability check and credit-based
authorization makes a HIP redirection-based flooding attack as
effective and applicable as a normal, direct flooding attack in which
the attacker itself sends the flooding traffic to the victim.
This analysis leads to the following two points. First, when a
reachability packet is received this nonce packet MUST be ignored if
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
it, in which case it is possible for an attacker to redirect their
connection. Note, this attack will always be possible when a
reachability packet is not sent.
7.2.2 Memory/Computational exhaustion DoS attacks
We now consider whether or not the proposed extensions to HIP add any
new DoS attacks (consideration of DoS attacks using the base HIP
exchange and updates is discussed in [2]). A simple attack is to
send many REA update packets containing many ip addresses that are
not flagged as preferred. The attacker continues to send such
packets until the number of ip addresses associated with the
attackers HI crashes the system. Therefore, their SHOULD be a limit
to the number of ip addresses that can be associated with any HI.
Other forms of memory/computationally exhausting attacks via the HIP
update packet are handled in the base HIP draft [2].
7.3 Mixed deployment environment
We now assume that we have both HIP and non-HIP aware hosts. Four
cases exist.
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
threat unless the HIP user is a MitM and can respond to the
reachability packet.
2. A non-HIP user attempts to redirect their connection onto a HIP
user. This falls into IPv4 and IPv6 security concerns, which are
outside the scope of this document.
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
contacts the service that a HIP user has a connection with and
then attempts to use a IPv6 change of address request to steal
the HIP user's connection. What will happen in this case is
implementation dependent but such a request should be ignored/
dropped. Even if the attack is sucessful, the HIP user can
reclaim their connection via HIP.
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
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
address via an REA update. Other possibilities exist but a
simple solution is to add a check which does not allow any HIP
session to be moved to or created upon an already existing ip
address.
8. IANA Considerations
9. Authors
Pekka Nikander originated this Internet Draft. Tom Henderson, Jari
Arkko, Greg Perkins, and Christian Vogt have each contributed
sections to this draft.
10. Acknowledgments
The authors thank Mika Kousa for many improvements to the draft.
11. References
11.1 Normative references
[1] Moskowitz, R., "Host Identity Protocol Architecture",
draft-ietf-hip-arch-02 (work in progress), January 2005. draft-ietf-hip-arch-02 (work in progress), January 2005.
[4] Bradner, S., "Key words for use in RFCs to Indicate Requirement [2] Moskowitz, R., "Host Identity Protocol", draft-ietf-hip-base-03
(work in progress), June 2005.
[3] Laganier, J. and L. Eggert, "Host Identity Protocol (HIP)
Rendezvous Extension", draft-ietf-hip-rvs-03 (work in progress),
July 2005.
[4] Kent, S. and R. Atkinson, "IP Encapsulating Security Payload
(ESP)", RFC 2406, November 1998.
[5] Jokela, P., "Using ESP transport format with HIP",
draft-ietf-hip-esp-00 (work in progress), July 2005.
[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.
[5] 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.
[6] Jokela, P., "Host Identity Protocol", draft-ietf-hip-esp-00 11.2 Informative references
(work in progress), February 2005.
12.2 Informative references
[7] Bellovin, S., "EIDs, IPsec, and HostNAT", IETF 41th, March 1998. [8] Bellovin, S., "EIDs, IPsec, and HostNAT", IETF 41th,
March 1998.
[8] Rescorla, E. and B. Korver, "Guidelines for Writing RFC Text on [9] Rescorla, E. and B. Korver, "Guidelines for Writing RFC Text on
Security Considerations", draft-iab-sec-cons-00 (work in Security Considerations", draft-iab-sec-cons-00 (work in
progress), August 2002. progress), August 2002.
[9] Nikander, P., "Mobile IP version 6 Route Optimization Security [10] Nikander, P., "Mobile IP version 6 Route Optimization Security
Design Background", draft-nikander-mobileip-v6-ro-sec-02 (work Design Background", draft-nikander-mobileip-v6-ro-sec-02 (work
in progress), December 2003. in progress), December 2003.
Authors' Addresses Author's Address
Pekka Nikander
Ericsson Research Nomadic Lab
JORVAS FIN-02420
FINLAND
Phone: +358 9 299 1
EMail: pekka.nikander@nomadiclab.com
Jari Arkko
Ericsson Research Nomadic Lab
JORVAS FIN-02420
FINLAND
Phone: +358 9 299 1
EMail: jari.arkko@nomadiclab.com
Tom Henderson Tom Henderson
The Boeing Company The Boeing Company
P.O. Box 3707 P.O. Box 3707
Seattle, WA Seattle, WA
USA USA
EMail: thomas.r.henderson@boeing.com Email: thomas.r.henderson@boeing.com
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.
skipping to change at page 34, line 5 skipping to change at page 43, line 23
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
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)
If UPDATE exceeds MTU because of too many locators, do not split into
multiple UPDATEs, but instead rely on IP fragmentation (C. Vogt, list
post on 06/12/05)
New value for LOCATOR parameter type (193), per 05/31/05 discussion
on the WG list
Various additions related to Credit-Based Authorization due to C.
Vogt
Security section contributed by Greg Perkins, with subsequent editing
from C. Vogt and P. Nikander
Reorganization according to RFC 4101 guidance on writing protocol
models
Open issue: LOCATOR parameter semantics (implicit/explicit removal)
Intellectual Property Statement Intellectual Property Statement
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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
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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.
 End of changes. 

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