draft-ietf-tsvwg-natsupp-02.txt   draft-ietf-tsvwg-natsupp-03.txt 
Network Working Group R. Stewart Network Working Group R. Stewart
Internet-Draft Adara Networks Internet-Draft Adara Networks
Intended status: Standards Track M. Tuexen Intended status: Standards Track M. Tuexen
Expires: September 13, 2012 I. Ruengeler Expires: April 12, 2013 I. Ruengeler
Muenster Univ. of Appl. Sciences Muenster Univ. of Appl. Sciences
March 12, 2012 October 9, 2012
Stream Control Transmission Protocol (SCTP) Network Address Translation Stream Control Transmission Protocol (SCTP) Network Address Translation
Support for Endpoints
draft-ietf-tsvwg-natsupp-02.txt draft-ietf-tsvwg-natsupp-03.txt
Abstract Abstract
Stream Control Transmission Protocol [RFC4960] provides a reliable Stream Control Transmission Protocol [RFC4960] provides a reliable
communications channel between two end-hosts in many ways similar to communications channel between two end-hosts in many ways similar to
TCP [RFC0793]. With the widespread deployment of Network Address TCP [RFC0793]. With the widespread deployment of Network Address
Translators (NAT), specialized code has been added to NAT for TCP Translators (NAT), specialized code has been added to NAT for TCP
that allows multiple hosts to reside behind a NAT and yet use only a that allows multiple hosts to reside behind a NAT and yet use only a
single globally unique IPv4 address, even when two hosts (behind a single globally unique IPv4 address, even when two hosts (behind a
NAT) choose the same port numbers for their connection. This NAT) choose the same port numbers for their connection. This
skipping to change at page 1, line 48 skipping to change at page 1, line 48
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/. Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on September 13, 2012. This Internet-Draft will expire on April 12, 2013.
Copyright Notice Copyright Notice
Copyright (c) 2012 IETF Trust and the persons identified as the Copyright (c) 2012 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of (http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents publication of this document. Please review these documents
skipping to change at page 2, line 26 skipping to change at page 2, line 26
include Simplified BSD License text as described in Section 4.e of include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License. described in the Simplified BSD License.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Conventions . . . . . . . . . . . . . . . . . . . . . . . . . 4 2. Conventions . . . . . . . . . . . . . . . . . . . . . . . . . 4
3. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4 3. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4
4. Problem Space Overview . . . . . . . . . . . . . . . . . . . . 5 4. Problem Space Overview . . . . . . . . . . . . . . . . . . . . 5
5. Association Setup Considerations . . . . . . . . . . . . . . . 5 5. Handling of Internal Port Number and Verification Tag
6. Handling of Internal Port Number and Verification Tag Collisions . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Collisions . . . . . . . . . . . . . . . . . . . . . . . . . . 6 6. Handling of Missing State . . . . . . . . . . . . . . . . . . 7
7. Handling of Internal Port Number Collisions . . . . . . . . . 7 7. Multi Point Traversal Considerations . . . . . . . . . . . . . 8
8. Handling of Missing State . . . . . . . . . . . . . . . . . . 9 8. Handling of Internal Port Number Collisions . . . . . . . . . 8
9. Multi Point Traversal Considerations . . . . . . . . . . . . . 11 9. SCTP Socket API Considerations . . . . . . . . . . . . . . . . 10
10. Socket API Considerations . . . . . . . . . . . . . . . . . . 11 10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10
10.1. Get or Set the NAT Friendliness (SCTP_NAT_FRIENDLY) . . . 11 11. Security Considerations . . . . . . . . . . . . . . . . . . . 10
11. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 12 12. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 10
11.1. New Chunk Flags for Two Chunk Types . . . . . . . . . . . 12 13. References . . . . . . . . . . . . . . . . . . . . . . . . . . 10
11.2. Three New Error Causes . . . . . . . . . . . . . . . . . 13 13.1. Normative References . . . . . . . . . . . . . . . . . . 10
11.3. Two New Chunk Parameter Types . . . . . . . . . . . . . . 13 13.2. Informative References . . . . . . . . . . . . . . . . . 11
12. Security Considerations . . . . . . . . . . . . . . . . . . . 14 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 11
13. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 14
14. References . . . . . . . . . . . . . . . . . . . . . . . . . . 14
14.1. Normative References . . . . . . . . . . . . . . . . . . 14
14.2. Informative References . . . . . . . . . . . . . . . . . 14
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 15
1. Introduction 1. Introduction
Stream Control Transmission Protocol [RFC4960] provides a reliable Stream Control Transmission Protocol [RFC4960] provides a reliable
communications channel between two end-hosts in many ways similar to communications channel between two end-hosts in many ways similar to
TCP [RFC0793]. With the widespread deployment of Network Address TCP [RFC0793]. With the widespread deployment of Network Address
Translators (NAT), specialized code has been added to NAT for TCP Translators (NAT), specialized code has been added to NAT for TCP
that allows multiple hosts to reside behind a NAT using private that allows multiple hosts to reside behind a NAT and yet use only a
addresses (see [RFC5735]) and yet use only a single globally unique single globally unique IPv4 address, even when two hosts (behind a
IPv4 address, even when two hosts (behind a NAT) choose the same port NAT) choose the same port numbers for their connection. This
numbers for their connection. This additional code is sometimes additional code is sometimes classified as Network Address and Port
classified as Network Address and Port Translation (NAPT). To date, Translation (NAPT). To date, specialized code for SCTP has not yet
specialized code for SCTP has not yet been added to most NATs so that been added to most NATs so that only true NAT is available. The end
only true NAT is available. The end result of this is that only one result of this is that only one SCTP capable host can be behind a
SCTP capable host can be behind a NAT. NAT.
This document describes an SCTP specific chunks and procedures to This document describes an SCTP specific chunks and procedures to
help NAT's provide similar features of NAPT in the single point and help NAT's provide similar features of NAPT in the single point and
multi-point traversal scenario. An SCTP implementation supporting multi-point traversal scenario. An SCTP implementation supporting
this extension will follow these procedures to assure that in both this extension will follow these procedures to assure that in both
single homed and multi-homed cases a NAT will maintain the proper single homed and multi-homed cases a NAT will maintain the proper
state without needing to change port numbers. state without needing to change port numbers.
A NAT will need to follow these procedures for generating appropriate A NAT will need to follow these procedures for generating appropriate
SCTP packet formats. NAT's should refer to [I-D.ietf-behave-sctpnat] SCTP packet formats. NAT's should refer to [I-D.ietf-behave-sctpnat]
skipping to change at page 5, line 27 skipping to change at page 5, line 27
4. Problem Space Overview 4. Problem Space Overview
When an SCTP endpoint is behind a NAT which supports When an SCTP endpoint is behind a NAT which supports
[I-D.ietf-behave-sctpnat] a number of problems may arise as it tries [I-D.ietf-behave-sctpnat] a number of problems may arise as it tries
to communicate with its peer: to communicate with its peer:
o More than one server behind a NAT may pick the same VTag and o More than one server behind a NAT may pick the same VTag and
source port when talking to the same peer server. This creates a source port when talking to the same peer server. This creates a
situation where the NAT will not be able to tell the two situation where the NAT will not be able to tell the two
associations apart. This situation is discussed in Section 6. associations apart. This situation is discussed in Section 5.
o When an SCTP endpoint is a server and talking with multiple peers o When an SCTP endpoint is a server and talking with multiple peers
and the peers are behind the same NAT, to the server the two and the peers are behind the same NAT, to the server the two
endpoints cannot be distinguished. This case is discussed in endpoints cannot be distinguished. This case is discussed in
Section 7. Section 8.
o A NAT could at one point during a conversation restart causing all o A NAT could at one point during a conversation restart causing all
of its state to be lost. This problem and its solution is of its state to be lost. This problem and its solution is
discussed in Section 8. discussed in Section 6.
o An SCTP endpoint may be behind two NAT's giving it redundancy. o An SCTP endpoint may be behind two NAT's giving it redundancy.
The method to set up this scenario is discussed in Section 9. The method to set up this scenario is discussed in Section 7.
Each of these solutions requires additional chunks and parameters, Each of these solutions requires additional chunks and parameters,
defined in this document, and possibly modified handling procedures defined in this document, and possibly modified handling procedures
from those specified in [RFC4960]. from those specified in [RFC4960].
5. Association Setup Considerations 5. Handling of Internal Port Number and Verification Tag Collisions
Every association MUST initially be set up single-homed. There MUST
NOT be any IPv4 Address parameter, IPv6 Address parameter, or
Supported Address Types parameter in the INIT-chunk. The INIT-ACK
chunk MUST NOT contain any IPv4 Address parameter or IPv6 Address
parameter.
If the association should finally be multi-homed, the procedure in
Section 9 MUST be used.
The INIT and INIT-ACK chunk SHOULD contain the Disable Restart
parameter defined in Section 7.
6. Handling of Internal Port Number and Verification Tag Collisions
Consider the case where two hosts in the Private-Address space want Consider the case where two hosts in the Private-Address space want
to set up an SCTP association with the same server running on the to set up an SCTP association with the same server running on the
same host in the Internet. This means that the External-Port and the same host in the Internet. This means that the External-Port and the
External-Address are the same. If they both choose the same External-Address are the same. If they both choose the same
Internal-Port and Internal-VTag, the NAT box cannot distinguish Internal-Port and Internal-VTag, the NAT box cannot distinguish
incoming packets anymore. But this is very unlikely. The Internal- incoming packets anymore. But this is very unlikely. The Internal-
VTags are chosen at random and if the Internal-Ports are also chosen VTags are chosen at random and if the Internal-Ports are also chosen
from the ephemeral port range at random this gives a 46-bit random from the ephemeral port range at random this gives a 46-bit random
number which has to match. In the TCP like NAPT case the NAT box can number which has to match. In the TCP like NAPT case the NAT box can
control the 16-bit Natted Port. control the 16-bit Natted Port.
The same can happen when the INIT-ACK is processed by the NAT.
However, in this unlikely event the NAT box MUST respond to the INIT However, in this unlikely event the NAT box MUST respond to the INIT
chunk by sending an ABORT chunk with the M-bit set. The M-bit is a chunk by sending an ABORT chunk with the M-bit set. The M-bit is a
new bit defined by this document to express to SCTP that the source new bit defined by this document to express to SCTP that the source
of this packet is a "middle" box, not the peer SCTP endpoint. The of this packet is a "middle" box, not the peer SCTP endpoint. The
source address of the packet containing the ABORT chunk MUST be the source address of the packet containing the ABORT chunk MUST be the
destination address of the SCTP packet containing the INIT chunk. destination address of the SCTP packet containing the INIT chunk.
The sender of the packet containing the INIT chunk, upon reception of The sender of the packet containing the INIT chunk, upon reception of
an ABORT with M-bit set SHOULD reinitiate the association setup an ABORT with M-bit set SHOULD reinitiate the association setup
procedure after choosing a new initiate tag. These procedures SHOULD procedure after choosing a new initiate tag. These procedures SHOULD
skipping to change at page 7, line 15 skipping to change at page 6, line 39
0 1 2 3 0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type = 6 | Reserved |M|T| Length | | Type = 6 | Reserved |M|T| Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
\ \ \ \
/ zero or more Error Causes / / zero or more Error Causes /
\ \ \ \
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Extended ABORT chunk The following error cause with cause code 0x00B0 (Colliding NAT table
entry) MUST be included in the ABORT chunk:
The following error cause with cause code 0x00B0 (V-tag and Port
Number Collision) MUST be included in the ABORT chunk:
0 1 2 3 0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Cause Code = 0x00B0 | Cause Length = Variable | | Cause Code = 0x00B0 | Cause Length = Variable |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
\ INIT chunk / \ INIT chunk /
/ \ / \
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
V-tag and Port Number Collision error cause 6. Handling of Missing State
FIXME: What to do when this is collision happens when processing an
ASCONF chunk?
7. Handling of Internal Port Number Collisions
When two SCTP hosts are behind a NAT and using the recommendations in
[I-D.ietf-behave-sctpnat] it is possible that two SCTP hosts in the
Private-Address space will want to set up an SCTP association with
the same server running on the same host in the Internet. For the
NAT appropriate tracking may be performed by assuring that the VTags
are unique between the two hosts as defined in
[I-D.ietf-behave-sctpnat]. But for the external SCTP server on the
internet this means that the External-Port and the External-Address
are the same. If they both have chosen the same Internal-Port the
server cannot distinguish both associations based on the address and
port numbers. For the server it looks like the association is being
restarted. To overcome this limitation the client sends a Disable
Restart parameter in the INIT-chunk which is defined as follows:
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 = 0xC007 | Length = 4 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Disable Restart parameter
When the server receives this parameter it MUST do the following:
o Include in the INIT-ACK a Disable Restart parameter to inform the
client that it will support the feature.
o Disable the restart procedures defined in [RFC4960] for this
association.
Servers that support this feature will need to be capable of
maintaining multiple connections to what appears to be the same peer
(behind the NAT) differentiated only by the VTags.
The NAT, when processing the INIT-ACK, should note in its internal
table that the association supports the Disable Restart extension.
This note is used when establishing future associations (i.e. when
processing an INIT from an internal host) to decide if the connection
should be allowed. The NAT MUST do the following when processing an
INIT:
o If the INIT is destined to an external address and port for which
the NAT has no outbound connection, allow the INIT creating an
internal mapping table.
o If the INIT matches the external address and port of an already
existing connection, validate that the external server supports
the Disable Restart feature. If it does allow the INIT to be
forwarded.
o If the external server does not support the Disable Restart
extension the NAT MUST send an ABORT with the M-bit set.
The following error cause with cause code 0x00B2 (Port Number
Collision) MUST be included in the ABORT chunk:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Cause Code = 0x00B2 | Cause Length = Variable |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
\ INIT chunk /
/ \
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Port Number Collision error cause
8. Handling of Missing State
If the NAT box receives a packet from the internal network for which If the NAT box receives a packet for which the lookup procedure does
the lookup procedure does not find an entry in the NAT table, a not find an entry in the NAT table, a packet containing an ERROR
packet containing an ERROR chunk is sent back with the M-bit set. packet is sent back with the M-bit set. The source address of the
The source address of the packet containing the ERROR chunk MUST be packet containing the ERROR chunk MUST be the destination address of
the destination address of the incoming SCTP packet. The the incoming SCTP packet. The verification tag is reflected.
verification tag is reflected and the T-bit is set. Please note that
such an packet containing an ERROR chunk SHOULD NOT be sent if the
received packet contains an ABORT, SHUTDOWN-COMPLETE or INIT-ACK
chunk.
The ERROR chunk defined in [RFC4960] is therefore extended by using The ERROR chunk defined in [RFC4960] is therefore extended by using
the following format: the following format:
0 1 2 3 0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type = 9 | Reserved |M|T| Length | | Type = 9 | Reserved |M|T| Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
\ \ \ \
/ zero or more Error Causes / / zero or more Error Causes /
\ \ \ \
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Extended ERROR chunk The following error cause with cause code 0x00B1 (Missing NAT table
entry) SHOULD be included in the ERROR chunk:
The following error cause with cause code 0x00B1 (Missing State)
SHOULD be included in the ERROR chunk:
0 1 2 3 0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Cause Code = 0x00B1 | Cause Length = Variable | | Cause Code = 0x00B1 | Cause Length = Variable |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
\ Incoming Packet / \ Incoming Packet /
/ \ / \
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Missing State error cause
Upon reception by an SCTP end-point with this ERROR chunk the Upon reception by an SCTP end-point with this ERROR chunk the
receiver SHOULD take the following actions: receiver SHOULD take the following actions:
o Validate the verification tag is reflected by looking at the VTag o Validate the verification tag is reflected by looking at the VTag
that would have been included in the outgoing packet. that would have been included in the outgoing packet.
o Validate that the peer of the SCTP association supports the o Validate that the peer of the SCTP association supports the
dynamic address extension, if it does not discard the incoming dynamic address extension, if it does not discard the incoming
ERROR chunk. ERROR chunk.
o Generate a new ASCONF chunk containing the V-tags parameter as o Generate a new ASCONF chunk as defined below including both sets
defined in Figure 2 and the Disable Restart parameter if the of VTags so that the NAT may recover the appropriate state. The
association is using the disabled restart feature. By processing
this packet the NAT can recover the appropriate state. The
procedures for generating an ASCONF chunk can be found in procedures for generating an ASCONF chunk can be found in
[RFC5061]. [RFC5061].
0 1 2 3 0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Parameter Type = 0xC008 | Parameter Length = 16 | | Parameter Type = 0xC008 | Parameter Length = 16 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ASCONF-Request Correlation ID | | ASCONF-Request Correlation ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Internal Verification Tag | | Internal Verification Tag |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| External Verification Tag | | External Verification Tag |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 2: V-tags parameter
If the NAT box receives a packet for which it has no NAT table entry If the NAT box receives a packet for which it has no NAT table entry
and the packet contains an ASCONF chunk with the V-tags parameter, and the packet contains an ASCONF chunk with a VTAG parameter, the
the NAT box MUST update its NAT table according to the verification NAT box MUST update its NAT table according to the verification tags
tags in the V-tags parameter and the optional Disable Restart in the VTAG parameter.
parameter.
The peer SCTP endpoint receiving such an ASCONF chunk SHOULD either The peer SCTP endpoint receiving such an ASCONF chunk SHOULD either
add the address and respond with an acknowledgment, if the address is add the address and respond with an acknowledgment, if the address is
new to the association (following all procedures defined in new to the association (following all procedures defined in
[RFC5061]). Or, if the address is already part of the association, [RFC5061]). Or, if the address is already part of the association,
the SCTP endpoint MUST NOT respond with an error, but instead should the SCTP endpoint MUST NOT respond with an error, but instead should
respond with an ASCONF-ACK chunk acknowledging the address but take respond with an ASCONF-ACK chunk acknowledging the address but take
no action (since the address is already in the association). no action (since the address is already in the association).
9. Multi Point Traversal Considerations 7. Multi Point Traversal Considerations
If a multi-homed SCTP end-point behind a NAT connects to a peer, it If a multi-homed SCTP end-point behind a NAT connects to a peer, it
SHOULD first set up the association single-homed with only one SHOULD first set up the association single-homed with only one
address causing the first NAT to populate its state. Then it SHOULD address causing the first NAT to populate its state. Then it SHOULD
add each IP address using ASCONF chunks sent via their respective add each IP address using ASCONF chunks sent via their respective
NATs. The address to add is the wildcard address and the lookup NATs. The address to add is the wildcard address and the lookup
address SHOULD also contain the V-tags parameter and optionally the address SHOULD also contain the VTAG parameter pair illustrated
Disable Restart parameter as illustrated above. above.
10. Socket API Considerations
This section describes how the socket API defined in [RFC6458] is
extended to provide a way for the application to control NAT
friendliness.
Please note that this section is informational only.
A socket API implementation based on [RFC6458] is extended by
supporting one new read/write socket option.
10.1. Get or Set the NAT Friendliness (SCTP_NAT_FRIENDLY)
This socket option can be used to set the NAT friendliness for future
associations and and retrieve the value for future and current ones.
struct sctp_assoc_value {
sctp_assoc_t assoc_id;
uint32_t assoc_value;
};
assoc_id: This parameter is ignored for one-to-one style sockets.
For one-to-many style sockets the application may fill in an
association identifier or SCTP_FUTURE_ASSOC for this query. It is
an error to use SCTP_{CURRENT|ALL}_ASSOC in assoc_id.
assoc_value: A non-zero value indicates a NAT-friendly mode.
11. IANA Considerations
[NOTE to RFC-Editor:
"RFCXXXX" is to be replaced by the RFC number you assign this
document.
]
[NOTE to RFC-Editor:
The suggested values for the chunk type and the chunk parameter
types are tentative and to be confirmed by IANA.
] 8. Handling of Internal Port Number Collisions
This document (RFCXXXX) is the reference for all registrations When two SCTP hosts are behind a NAT and using the recommendations in
described in this section. The suggested changes are described [I-D.ietf-behave-sctpnat] it is possible that two SCTP hosts in the
below. Private-Address space will want to set up an SCTP association with
the same server running on the same host in the Internet. For the
NAT appropriate tracking may be performed by assuring that the VTags
are unique between the two hosts as defined in
[I-D.ietf-behave-sctpnat]. But for the external SCTP server on the
internet this means that the External-Port and the External-Address
are the same. If they both have chosen the same Internal-Port the
server cannot distinguish both associations based on the address and
port numbers. For the server it looks like the association is being
restarted. To overcome this limitation the client sends a
DISABLE_RESTART parameter in the INIT-chunk which is defined as
follows:
11.1. New Chunk Flags for Two Chunk Types 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 = 0xC007 | Length = 4 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
As defined in [RFC6096] two chunk flags have to be assigned by IANA When the server receives this parameter it MUST do the following:
for the ERROR chunk. The suggested value for the T bit is 0x01 and
for the M bit is 0x02.
This requires an update of the "ERROR Chunk Flags" registry for SCTP: o Include in the INIT-ACK a DISABLE_RESTART parameter to inform the
client that it will support the feature.
ERROR Chunk Flags o Disable the restart procedures defined in [RFC4960] for this
association.
Chunk Flag Value Chunk Flag Name Reference Servers that support this feature will need to be capable of
0x01 T bit [RFCXXXX] maintaining multiple connections to what appears to be the same peer
0x02 M Bit [RFCXXXX] (behind the NAT) differentiated only by the VTags.
0x04 Unassigned
0x08 Unassigned
0x10 Unassigned
0x20 Unassigned
0x40 Unassigned
0x80 Unassigned
As defined in [RFC6096] one chunk flag has to be assigned by IANA for The NAT, when processing the INIT-ACK, should note in its internal
the ABORT chunk. The suggested value of the M bit is 0x02. table that the external server supports the DISABLE_RESTART
extension. This note is used when establishing future associations
(i.e. when processing an INIT from an internal host) to decide if the
connection should be allowed. The NAT MUST do the following when
processing an INIT:
This requires an update of the "ABORT Chunk Flags" registry for SCTP: o If the INIT is destined to an external address and port for which
the NAT has no outbound connection, allow the INIT creating an
internal mapping table.
ABORT Chunk Flags o If the INIT matches the external address and port of an already
existing connection, validate that the external server supports
the DISABLE_RESTART feature. If it does allow the INIT to be
forwarded.
Chunk Flag Value Chunk Flag Name Reference o If the external server does not support the DISABLE_RESTART
0x01 T bit [RFC4960] extension the NAT MUST send an ABORT with the M-bit set.
0x02 M Bit [RFCXXXX]
0x04 Unassigned
0x08 Unassigned
0x10 Unassigned
0x20 Unassigned
0x40 Unassigned
0x80 Unassigned
11.2. Three New Error Causes The following error cause with cause code 0x00B2 (Duplicate Local
Port with DISABLE_RESTART not Supported) MUST be included in the
ABORT chunk:
Three error causes have to be assigned by IANA. It is suggested to 0 1 2 3
use the values given below. 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Cause Code = 0x00B2 | Cause Length = Variable |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
\ INIT chunk /
/ \
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
This requires three additional lines in the "Error Cause Codes" 9. SCTP Socket API Considerations
registry for SCTP:
Chunk Parameter Types TBD
Value Cause Code Reference 10. IANA Considerations
-------- ------------------------------------------------ ---------
176 V-tag and Port Number Collision [RFCXXXX]
177 Missing State [RFCXXXX]
178 Port Number Collision [RFCXXXX]
11.3. Two New Chunk Parameter Types M-Bit for ABORT and ERROR chunk (0x02).
Two chunk parameter types have to be assigned by IANA. It is Error cause Colliding NAT table entry, (0x00B1).
suggested to use the values given below. IANA should assign these
values from the pool of parameters with the upper two bits set to
'11'.
This requires two additional lines in the "Chunk Parameter Types" Error cause Duplicate Local Port with DISABLE_RESTART not Supported,
registry for SCTP: (0x00B2).
Chunk Parameter Types Disable restart parameter (0xC007).
ID Value Chunk Parameter Type Reference ASCONF Parameter (0xC008).
-------- ------------------------------------------------ ---------
49159 Disable Restart (0xC007) [RFCXXXX]
49160 V-tags (0xC008) [RFCXXXX]
12. Security Considerations 11. Security Considerations
The document does not add any additional security considerations to TBD
the ones given in [RFC4960], [RFC4895], and [RFC5061].
13. Acknowledgments 12. Acknowledgments
The authors wish to thank Jason But, Bryan Ford, David Hayes, Alfred The authors wish to thank Jason But, Bryan Ford, David Hayes, Alfred
Hines, Henning Peters, Timo Voelker, Dan Wing, and Qiaobing Xie for Hines, Henning Peters, Timo Voelker, Dan Wing, and Qiaobing Xie for
their invaluable comments. their invaluable comments.
14. References 13. References
14.1. Normative References 13.1. Normative References
[RFC0793] Postel, J., "Transmission Control Protocol", STD 7, [RFC0793] Postel, J., "Transmission Control Protocol", STD 7,
RFC 793, September 1981. RFC 793, September 1981.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997. Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC4895] Tuexen, M., Stewart, R., Lei, P., and E. Rescorla, [RFC4895] Tuexen, M., Stewart, R., Lei, P., and E. Rescorla,
"Authenticated Chunks for the Stream Control Transmission "Authenticated Chunks for the Stream Control Transmission
Protocol (SCTP)", RFC 4895, August 2007. Protocol (SCTP)", RFC 4895, August 2007.
skipping to change at page 14, line 42 skipping to change at page 11, line 24
[RFC5061] Stewart, R., Xie, Q., Tuexen, M., Maruyama, S., and M. [RFC5061] Stewart, R., Xie, Q., Tuexen, M., Maruyama, S., and M.
Kozuka, "Stream Control Transmission Protocol (SCTP) Kozuka, "Stream Control Transmission Protocol (SCTP)
Dynamic Address Reconfiguration", RFC 5061, Dynamic Address Reconfiguration", RFC 5061,
September 2007. September 2007.
[RFC6096] Tuexen, M. and R. Stewart, "Stream Control Transmission [RFC6096] Tuexen, M. and R. Stewart, "Stream Control Transmission
Protocol (SCTP) Chunk Flags Registration", RFC 6096, Protocol (SCTP) Chunk Flags Registration", RFC 6096,
January 2011. January 2011.
14.2. Informative References [I-D.ietf-tsvwg-sctp-udp-encaps]
Tuexen, M. and R. Stewart, "UDP Encapsulation of SCTP
Packets", draft-ietf-tsvwg-sctp-udp-encaps-04 (work in
progress), July 2012.
13.2. Informative References
[RFC5735] Cotton, M. and L. Vegoda, "Special Use IPv4 Addresses", [RFC5735] Cotton, M. and L. Vegoda, "Special Use IPv4 Addresses",
BCP 153, RFC 5735, January 2010. BCP 153, RFC 5735, January 2010.
[RFC6083] Tuexen, M., Seggelmann, R., and E. Rescorla, "Datagram
Transport Layer Security (DTLS) for Stream Control
Transmission Protocol (SCTP)", RFC 6083, January 2011.
[RFC6458] Stewart, R., Tuexen, M., Poon, K., Lei, P., and V. [RFC6458] Stewart, R., Tuexen, M., Poon, K., Lei, P., and V.
Yasevich, "Sockets API Extensions for the Stream Control Yasevich, "Sockets API Extensions for the Stream Control
Transmission Protocol (SCTP)", RFC 6458, December 2011. Transmission Protocol (SCTP)", RFC 6458, December 2011.
[I-D.ietf-behave-sctpnat] [I-D.ietf-behave-sctpnat]
Stewart, R., Tuexen, M., and I. Ruengeler, "Stream Control Stewart, R., Tuexen, M., and I. Ruengeler, "Stream Control
Transmission Protocol (SCTP) Network Address Translation", Transmission Protocol (SCTP) Network Address Translation",
draft-ietf-behave-sctpnat-06 (work in progress), draft-ietf-behave-sctpnat-06 (work in progress),
March 2012. March 2012.
Authors' Addresses Authors' Addresses
Randall R. Stewart Randall R. Stewart
Adara Networks Adara Networks
Chapin, SC 29036 Chapin, SC 29036
US USA
Email: randall@lakerest.net Email: randall@lakerest.net
Michael Tuexen Michael Tuexen
Muenster University of Applied Sciences Muenster University of Applied Sciences
Stegerwaldstrasse 39 Stegerwaldstrasse 39
48565 Steinfurt 48565 Steinfurt
DE DE
Email: tuexen@fh-muenster.de Email: tuexen@fh-muenster.de
 End of changes. 51 change blocks. 
264 lines changed or deleted 128 lines changed or added

This html diff was produced by rfcdiff 1.41. The latest version is available from http://tools.ietf.org/tools/rfcdiff/