draft-ietf-mmusic-sdp4nat-05.txt   rfc3605.txt 
INTERNET DRAFT C. Huitema
<draft-ietf-mmusic-sdp4nat-05.txt> Microsoft
Expires November 30, 2003 May 30, 2003
RTCP attribute in SDP
Status of this memo Network Working Group C. Huitema
Request for Comments: 3605 Microsoft
Category: Standards Track October 2003
This document is an Internet-Draft and is in full conformance with Real Time Control Protocol (RTCP) attribute in
all provisions of Section 10 of RFC2026. Session Description Protocol (SDP)
This document is an Internet-Draft. Internet-Drafts are working Status of this Memo
documents of the Internet Engineering Task Force (IETF), its areas,
and its working groups. Note that other groups may also distribute
working documents as Internet-Drafts.
Internet-Drafts are draft documents valid for a maximum of six This document specifies an Internet standards track protocol for the
months and may be updated, replaced, or obsoleted by other documents Internet community, and requests discussion and suggestions for
at any time. It is inappropriate to use Internet- Drafts as improvements. Please refer to the current edition of the "Internet
reference material or to cite them other than as "work in progress." Official Protocol Standards" (STD 1) for the standardization state
and status of this protocol. Distribution of this memo is unlimited.
The list of current Internet-Drafts can be accessed at Copyright Notice
http://www.ietf.org/ietf/1id-abstracts.txt.
The list of Internet-Draft Shadow Directories can be accessed at Copyright (C) The Internet Society (2003). All Rights Reserved.
http://www.ietf.org/shadow.html.
Abstract Abstract
The session description protocol (SDP) is used to describe the The Session Description Protocol (SDP) is used to describe the
parameters of media streams used in multimedia sessions. When a parameters of media streams used in multimedia sessions. When a
session requires multiple ports, SDP assumes that these port have session requires multiple ports, SDP assumes that these ports have
consecutive numbers. However, when the session crosses a network consecutive numbers. However, when the session crosses a network
address translation device that also uses port mapping, the ordering address translation device that also uses port mapping, the ordering
of ports can be destroyed by the translation. To handle this, we of ports can be destroyed by the translation. To handle this, we
propose an extension attribute to SDP. propose an extension attribute to SDP.
1. Introduction 1. Introduction
The session invitation protocol (SIP, [RFC3261]) is often used to The session invitation protocol (SIP, [RFC3261]) is often used to
establish multi-media sessions on the Internet. There are often establish multi-media sessions on the Internet. There are often
cases today in which one or both end of the connection are hidden cases today in which one or both ends of the connection are hidden
behind a network address translation device [RFC2766]. In this case, behind a network address translation device [RFC2766]. In this case,
the SDP text must document the IP addresses and UDP ports as they the SDP text must document the IP addresses and UDP ports as they
appear on the "public Internet" side of the NAT; in this memo, we appear on the "public Internet" side of the NAT. In this memo, we
will suppose that the host located behind a NAT has a way to obtain will suppose that the host located behind a NAT has a way to obtain
these numbers; a possible way to learn these numbers is briefly these numbers. A possible way to learn these numbers is briefly
outlined in section 3. However, just learning the numbers is not outlined in section 3, however, just learning the numbers is not
enough. enough.
The SIP messages use the encoding defined in SDP [RFC2327] to The SIP messages use the encoding defined in SDP [RFC2327] to
describe the IP addresses and TCP or UDP ports used by the various describe the IP addresses and TCP or UDP ports used by the various
media. Audio and video are typically sent using RTP [RTP-NEW], which media. Audio and video are typically sent using RTP [RFC3550], which
requires two UDP ports, one for the media and one for the control requires two UDP ports, one for the media and one for the control
protocol (RTCP). SDP carries only one port number per media, and protocol (RTCP). SDP carries only one port number per media, and
states that "other ports used by the media application (such as the states that "other ports used by the media application (such as the
RTCP port) should be derived algorithmically from the base media RTCP port) should be derived algorithmically from the base media
port." RTCP port numbers were necessarily derived from the base port." RTCP port numbers were necessarily derived from the base
media port in older versions of RTP (such as [RFC1889]), but now media port in older versions of RTP (such as [RFC1889]), but now that
that this restriction has been lifted, there is a need to specify this restriction has been lifted, there is a need to specify RTCP
RTCP ports explicitly in SDP. Note, however, that implementations of ports explicitly in SDP. Note, however, that implementations of RTP
RTP adhering to the earlier [RFC1889] specification may not be able adhering to the earlier [RFC1889] specification may not be able to
to make use of the SDP attributes specified in this document. make use of the SDP attributes specified in this document.
When the NAT device performs port mapping, there is no guarantee When the NAT device performs port mapping, there is no guarantee that
that the mappings of two separate ports reflects the sequencing and the mappings of two separate ports reflects the sequencing and the
the parity of the original port numbers; in fact, when the NAT parity of the original port numbers; in fact, when the NAT manages a
manages a pool of IP addresses, it is even possible that the RTP and pool of IP addresses, it is even possible that the RTP and the RTCP
the RTCP ports may be mapped to different addresses. In order to ports may be mapped to different addresses. In order to successfully
successfully establish connections despite the misordering of the establish connections despite the misordering of the port numbers and
port numbers and the possible parity switches caused by the NAT, we the possible parity switches caused by the NAT, we propose to use a
propose to use a specific SDP attribute to document the RTCP port specific SDP attribute to document the RTCP port and optionally the
and optionally the RTCP address. RTCP address.
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]. document are to be interpreted as described in [RFC2119].
2. Description of the solution 2. Description of the Solution
The main part of our solution is the declaration of an SDP attribute The main part of our solution is the declaration of an SDP attribute
for documenting the port used by RTCP. for documenting the port used by RTCP.
2.1. The RTCP attribute 2.1. The RTCP Attribute
The RTCP attribute is used to document the RTCP port used for media The RTCP attribute is used to document the RTCP port used for media
stream, when that port is not the next higher (odd) port number stream, when that port is not the next higher (odd) port number
following the RTP port described in the media line. The RTCP following the RTP port described in the media line. The RTCP
attribute is a "value" attribute, and follows the general syntax attribute is a "value" attribute, and follows the general syntax
specified page 18 of [RFC2327]: "a=<attribute>:<value>". For the specified page 18 of [RFC2327]: "a=<attribute>:<value>". For the
RTCP attribute: RTCP attribute:
* the name is the ascii string "rtcp" (lower case), * the name is the ascii string "rtcp" (lower case),
* the value is the RTCP port number and optional address. * the value is the RTCP port number and optional address.
The formal description of the attribute is defined by the following The formal description of the attribute is defined by the following
ABNF syntax: ABNF [RFC2234] syntax:
rtcp-attribute = "a=rtcp:" port [nettype space addrtype space rtcp-attribute = "a=rtcp:" port [nettype space addrtype space
connection-address] CRLF connection-address] CRLF
In this description, the "port", "nettype", "addrtype" and In this description, the "port", "nettype", "addrtype" and
"connection-address" tokens are defined as specified in "Appendix A: "connection-address" tokens are defined as specified in "Appendix A:
SDP Grammar" of [RFC2327]. SDP Grammar" of [RFC2327].
Example encodings could be: Example encodings could be:
m=audio 49170 RTP/AVP 0 m=audio 49170 RTP/AVP 0
a=rtcp:53020 a=rtcp:53020
m=audio 49170 RTP/AVP 0 m=audio 49170 RTP/AVP 0
skipping to change at page 3, line 17 skipping to change at page 3, line 20
m=audio 49170 RTP/AVP 0 m=audio 49170 RTP/AVP 0
a=rtcp:53020 a=rtcp:53020
m=audio 49170 RTP/AVP 0 m=audio 49170 RTP/AVP 0
a=rtcp:53020 IN IP4 126.16.64.4 a=rtcp:53020 IN IP4 126.16.64.4
m=audio 49170 RTP/AVP 0 m=audio 49170 RTP/AVP 0
a=rtcp:53020 IN IP6 2001:2345:6789:ABCD:EF01:2345:6789:ABCD a=rtcp:53020 IN IP6 2001:2345:6789:ABCD:EF01:2345:6789:ABCD
The RTCP attribute MAY be used as a media level attribute; it MUST The RTCP attribute MAY be used as a media level attribute; it MUST
NOT be used as a session level attribute. NOT be used as a session level attribute. Though the examples below
relate to a method that will return only unicast addresses, both
unicast and multicast values are valid.
3. Discussion of the solution 3. Discussion of the Solution
The implementation of the solution is fairly straightforward. The The implementation of the solution is fairly straightforward. The
questions that have been most often asked regarding this solution questions that have been most often asked regarding this solution are
are whether this is useful, i.e. whether a host can actually whether this is useful, i.e., whether a host can actually discover
discover port numbers in an unmodified NAT, whether it is port numbers in an unmodified NAT, whether it is sufficient, i.e.,
sufficient, i.e. whether or not there is a need to document more whether or not there is a need to document more than one ancillary
than one ancillary port per media type, and whether why should not port per media type, and whether why should not change the media
change the media definition instead of adding a new attribute. definition instead of adding a new attribute.
3.1. How do we discover port numbers? 3.1. How do we Discover Port Numbers?
The proposed solution is only useful if the host can discover the The proposed solution is only useful if the host can discover the
"translated port numbers", i.e. the value of the ports as they "translated port numbers", i.e., the value of the ports as they
appear on the "external side" of the NAT. One possibility is to ask appear on the "external side" of the NAT. One possibility is to ask
the cooperation of a well connected third party that will act as a the cooperation of a well connected third party that will act as a
server according to STUN [RFC3489]. We thus obtain a four step server according to STUN [RFC3489]. We thus obtain a four step
process: process:
1- The host allocates two UDP ports numbers for an RTP/RTCP pair, 1- The host allocates two UDP ports numbers for an RTP/RTCP pair,
2- The host sends a UDP message from each port to the STUN server, 2- The host sends a UDP message from each port to the STUN server,
3- The STUN server reads the source address and port of the packet, 3- The STUN server reads the source address and port of the packet,
skipping to change at page 3, line 44 skipping to change at page 4, line 4
the cooperation of a well connected third party that will act as a the cooperation of a well connected third party that will act as a
server according to STUN [RFC3489]. We thus obtain a four step server according to STUN [RFC3489]. We thus obtain a four step
process: process:
1- The host allocates two UDP ports numbers for an RTP/RTCP pair, 1- The host allocates two UDP ports numbers for an RTP/RTCP pair,
2- The host sends a UDP message from each port to the STUN server, 2- The host sends a UDP message from each port to the STUN server,
3- The STUN server reads the source address and port of the packet, 3- The STUN server reads the source address and port of the packet,
and copies them in the text of a reply, and copies them in the text of a reply,
4- The host parses the reply according to the STUN protocol and 4- The host parses the reply according to the STUN protocol and
learns the external address and port corresponding to each of the learns the external address and port corresponding to each of the
two UDP port. two UDP ports.
This algorithm supposes that the NAT will use the same translation This algorithm supposes that the NAT will use the same translation
for packets sent to the third party and to the "SDP peer" with which for packets sent to the third party and to the "SDP peer" with which
the host wants to establish a connection. There is no guarantee that the host wants to establish a connection. There is no guarantee that
all NAT boxes deployed on the Internet have this characteristic. all NAT boxes deployed on the Internet have this characteristic.
Implementers are referred to the STUN specification [RFC3489] for an Implementers are referred to the STUN specification [RFC3489] for an
extensive discussion of the various types of NAT. extensive discussion of the various types of NAT.
3.2. Do we need to support multiple ports? 3.2. Do we need to Support Multiple Ports?
Most media streams are transmitted using a single pair of RTP and Most media streams are transmitted using a single pair of RTP and
RTCP ports. It is possible, however, to transmit a single media over RTCP ports. It is possible, however, to transmit a single media over
several RTP flows, for example using hierarchical encoding. In this several RTP flows, for example using hierarchical encoding. In this
case, SDP will encode the port number used by RTP on the first flow, case, SDP will encode the port number used by RTP on the first flow,
and the number of flows, as in: and the number of flows, as in:
m=video 49170/2 RTP/AVP 31 m=video 49170/2 RTP/AVP 31
In this example, the media is sent over 2 consecutive pairs of In this example, the media is sent over 2 consecutive pairs of ports,
ports, corresponding respectively to RTP for the first flow (even corresponding respectively to RTP for the first flow (even number,
number, 49170), RTCP for the first flow (odd number, 49171), RTP for 49170), RTCP for the first flow (odd number, 49171), RTP for the
the second flow (even number, 49172), and RTCP for the second flow second flow (even number, 49172), and RTCP for the second flow (odd
(odd number, 49173). number, 49173).
In theory, it would be possible to modify SDP and document the many In theory, it would be possible to modify SDP and document the many
ports corresponding to the separate encoding layers. However, ports corresponding to the separate encoding layers. However,
layered encoding is not much used in practice, and when used is layered encoding is not much used in practice, and when used is
mostly used in conjunction with multicast transmission. The mostly used in conjunction with multicast transmission. The
translation issues documented in this memo apply uniquely to unicast translation issues documented in this memo apply uniquely to unicast
transmission, and thus there is no short term need for the support transmission, and thus there is no short term need for the support of
of multiple port descriptions. It is more convenient and more robust multiple port descriptions. It is more convenient and more robust to
to focus on the simple case in which a media is sent over exactly focus on the simple case in which a media is sent over exactly one
one RTP/RTCP stream. RTP/RTCP stream.
3.3. Why not expand the media definition? 3.3. Why not Expand the Media Definition?
The RTP ports are documented in the media description line, and it The RTP ports are documented in the media description line, and it
would seem convenient to document the RTCP port at the same place, would seem convenient to document the RTCP port at the same place,
rather than create an RTCP attribute. We considered this design rather than create an RTCP attribute. We considered this design
alternative and rejected it for two reasons: adding an extra port alternative and rejected it for two reasons: adding an extra port
number and an option address in the media description would be number and an option address in the media description would be
awkward, and more importantly it would create problems with existing awkward, and more importantly it would create problems with existing
applications, which would have to reject the entire media applications, which would have to reject the entire media description
description if they did not understand the extension. On the if they did not understand the extension. On the contrary, adding an
contrary, adding an attribute has a well defined failure mode: attribute has a well defined failure mode: implementations that don't
implementations that don't understand the "a=rtcp" attribute will understand the "a=rtcp" attribute will simply ignore it; they will
simply ignore it; they will fail to send RTCP packets to the fail to send RTCP packets to the specified address, but they will at
specified address, but they will at least be able to receive the least be able to receive the media in the RTP packets.
media in the RTP packets.
4. UNSAF considerations 4. UNSAF Considerations
The RTCP attribute in SDP is used to enable establishment of The RTCP attribute in SDP is used to enable establishment of RTP/RTCP
RTP/RTCP flows through NAT. This mechanism can be used in flows through NAT. This mechanism can be used in conjunction with an
conjunction with an address discovery mechanism such as STUN address discovery mechanism such as STUN [RFC3489]. STUN is a short
[RFC3489]. STUN is a short term fix to the NAT traversal problem, term fix to the NAT traversal problem, which requires thus
which requires thus consideration of the general issues linked to consideration of the general issues linked to "Unilateral self-
"Unilateral self-address fixing" [RFC3424]. address fixing" [RFC3424].
The RTCP attribute addresses a very specific problem, the The RTCP attribute addresses a very specific problem, the
documentation of port numbers as they appear after address documentation of port numbers as they appear after address
translation by a port-mapping NAT. The RTCP attribute SHOULD NOT be translation by a port-mapping NAT. The RTCP attribute SHOULD NOT be
used for other applications. used for other applications.
We expect that, with time, one of two exit strategies can be We expect that, with time, one of two exit strategies can be
developed. The IETF may develop an explicit "middlebox control" developed. The IETF may develop an explicit "middlebox control"
protocol that will enable applications to obtain a pair of port protocol that will enable applications to obtain a pair of port
numbers appropriate for RTP and RTCP. Another possibility is the numbers appropriate for RTP and RTCP. Another possibility is the
skipping to change at page 5, line 26 skipping to change at page 5, line 38
ports. In both cases, there will be no need for documenting a "non ports. In both cases, there will be no need for documenting a "non
standard" RTCP port with the RTCP attribute. standard" RTCP port with the RTCP attribute.
5. Security Considerations 5. Security Considerations
This SDP extension is not believed to introduce any significant This SDP extension is not believed to introduce any significant
security risk to multi-media applications. One could conceive that a security risk to multi-media applications. One could conceive that a
malevolent third party would use the extension to redirect the RTCP malevolent third party would use the extension to redirect the RTCP
fraction of an RTP exchange, but this requires intercepting and fraction of an RTP exchange, but this requires intercepting and
rewriting the signaling packet carrying the SDP text; if an rewriting the signaling packet carrying the SDP text; if an
interceptor can do that, many more attacks are available, including interceptor can do that, many more attacks are available, including a
a wholesale change of the addresses and port numbers at which the wholesale change of the addresses and port numbers at which the media
media will be sent. will be sent.
In order to avoid attacks of this sort, when SDP is used in a In order to avoid attacks of this sort, when SDP is used in a
signaling packet where it is of the form application/sdp, end-to-end signaling packet where it is of the form application/sdp, end-to-end
integrity using S/MIME [RFC3369] is the technical method to be integrity using S/MIME [RFC3369] is the technical method to be
implemented and applied. This is compatible with SIP [RFC3261]. implemented and applied. This is compatible with SIP [RFC3261].
6. IANA Considerations 6. IANA Considerations
This document defines a new SDP parameter, the attribute field This document defines a new SDP parameter, the attribute field
"rtcp", which per [RFC2327] should be registered by IANA. This "rtcp", which per [RFC2327] has been registered by IANA. This
attribute field is designed for use at media level only. attribute field is designed for use at media level only.
7. Copyright 7. Intellectual Property Statement
The following copyright notice is copied from RFC 2026 [Bradner,
1996], Section 10.4, and describes the applicable copyright for this
document.
Copyright (C) The Internet Society March 21, 2001. All Rights
Reserved.
This document and translations of it may be copied and furnished to
others, and derivative works that comment on or otherwise explain it
or assist in its implementation may be prepared, copied, published
and distributed, in whole or in part, without restriction of any
kind, provided that the above copyright notice and this paragraph
are included on all such copies and derivative works. However, this
document itself may not be modified in any way, such as by removing
the copyright notice or references to the Internet Society or other
Internet organizations, except as needed for the purpose of
developing Internet standards in which case the procedures for
copyrights defined in the Internet Standards process must be
followed, or as required to translate it into languages other than
English.
The limited permissions granted above are perpetual and will not be
revoked by the Internet Society or its successors or assignees.
This document and the information contained herein is provided on an
"AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
8. Intellectual Property
The following notice is copied from RFC 2026 [Bradner, 1996],
Section 10.4, and describes the position of the IETF concerning
intellectual property claims made against this document.
The IETF takes no position regarding the validity or scope of any The IETF takes no position regarding the validity or scope of any
intellectual property or other rights that might be claimed to intellectual property or other rights that might be claimed to
pertain to the implementation or use other technology described in pertain to the implementation or use other technology described in
this document or the extent to which any license under such rights this document or the extent to which any license under such rights
might or might not be available; neither does it represent that it might or might not be available; neither does it represent that it
has made any effort to identify any such rights. Information on the has made any effort to identify any such rights. Information on the
IETF's procedures with respect to rights in standards-track and IETF's procedures with respect to rights in standards-track and
standards-related documentation can be found in BCP-11. Copies of standards-related documentation can be found in BCP-11. Copies of
claims of rights made available for publication and any assurances claims of rights made available for publication and any assurances of
of licenses to be made available, or the result of an attempt made licenses to be made available, or the result of an attempt made to
to obtain a general license or permission for the use of such obtain a general license or permission for the use of such
proprietary rights by implementers or users of this specification proprietary rights by implementers or users of this specification can
can be obtained from the IETF Secretariat. be obtained from the IETF Secretariat.
The IETF invites any interested party to bring to its attention any The IETF invites any interested party to bring to its attention any
copyrights, patents or patent applications, or other proprietary copyrights, patents or patent applications, or other proprietary
rights which may cover technology that may be required to practice rights which may cover technology that may be required to practice
this standard. Please address the information to the IETF Executive this standard. Please address the information to the IETF Executive
Director. Director.
9. Acknowledgements 8. Acknowledgements
The original idea for using the "rtcp" attribute was developed by The original idea for using the "rtcp" attribute was developed by Ann
Ann Demirtjis. The draft was reviewed by the MMUSIC and AVT working Demirtjis. The document was reviewed by the MMUSIC and AVT working
groups of the IETF. groups of the IETF.
10. References 9. References
Normative references
[RFC2327] Handley, M., and V. Jacobson, "SDP: Session Description
Protocol", RFC 2327, April 1998.
[RTP-NEW] Schulzrinne, H., Casner, S., Frederick, R., and V. 9.1. Normative References
Jacobson. "RTP: A Transport Protocol for Real-Time Applications",
Work in progress, March 2003.
[RFC1889] Schulzrinne, H., Casner, S., Frederick, R., and V. [RFC1889] Schulzrinne, H., Casner, S., Frederick, R. and V.
Jacobson. "RTP: A Transport Protocol for Real-Time Applications", Jacobson. "RTP: A Transport Protocol for Real-Time
RFC 1889, January 1996. Applications", RFC 1889, January 1996.
[RFC2119] S. Bradner, "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", RFC 2119, March 1997. Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC2234] Crocker, D., and P. Overell, "Augmented BNF for Syntax [RFC2234] Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax
Specifications: ABNF", RFC 2234, November 1997. Specifications: ABNF", RFC 2234, November 1997.
[RFC3489] Rosenberg, J., Weinberger, J., Huitema, C., and R. Mahy. [RFC2327] Handley, M. and V. Jacobson, "SDP: Session Description
"STUN - Simple Traversal of User Datagram Protocol (UDP) Through Protocol", RFC 2327, April 1998.
Network Address Translators (NATs)". RFC 3489, March 2003
Informative references [RFC3489] Rosenberg, J., Weinberger, J., Huitema, C. and R. Mahy.
"STUN - Simple Traversal of User Datagram Protocol (UDP)
Through Network Address Translators (NATs)", RFC 3489,
March 2003.
[RFC2766] Tsirtsis, G., and P. Srisuresh. "Network Address [RFC3550] Schulzrinne, H., Casner, S., Frederick, R. and V.
Translation - Protocol Translation (NAT-PT)", RFC 2766, February Jacobson. "RTP: A Transport Protocol for Real-Time
2000. Applications", RFC 3550, July 2003.
9.2. Informative References
[RFC2766] Tsirtsis, G. and P. Srisuresh. "Network Address
Translation - Protocol Translation (NAT-PT)", RFC 2766,
February 2000.
[RFC3261] Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston, [RFC3261] Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston,
A., Peterson, J., Sparks, R., Handley, M., and E. Schooler. SIP: A., Peterson, J., Sparks, R., Handley, M. and E. Schooler,
Session Initiation Protocol. RFC 3261, June 2002. "SIP: Session Initiation Protocol", RFC 3261, June 2002.
[RFC3369] R. Housley. Cryptographic Message Syntax (CMS). RFC 3369, [RFC3369] Housley, R., "Cryptographic Message Syntax (CMS)", RFC
August 2002. 3369, August 2002.
[RFC3424] L. Daigle, "IAB considerations for UNilateral Self-Address [RFC3424] Daigle, L., "IAB considerations for UNilateral Self-
Fixing (UNSAF) across network address translation," RFC 3424, Address Fixing (UNSAF) across network address
November 2002. translation", RFC 3424, November 2002.
11. Author's Address 10. Author's Address
Christian Huitema Christian Huitema
Microsoft Corporation Microsoft Corporation
One Microsoft Way One Microsoft Way
Redmond, WA 98052-6399 Redmond, WA 98052-6399
Email: huitema@microsoft.com EMail: huitema@microsoft.com
11. Full Copyright Statement
Copyright (C) The Internet Society (2003). All Rights Reserved.
This document and translations of it may be copied and furnished to
others, and derivative works that comment on or otherwise explain it
or assist in its implementation may be prepared, copied, published
and distributed, in whole or in part, without restriction of any
kind, provided that the above copyright notice and this paragraph are
included on all such copies and derivative works. However, this
document itself may not be modified in any way, such as by removing
the copyright notice or references to the Internet Society or other
Internet organizations, except as needed for the purpose of
developing Internet standards in which case the procedures for
copyrights defined in the Internet Standards process must be
followed, or as required to translate it into languages other than
English.
The limited permissions granted above are perpetual and will not be
revoked by the Internet Society or its successors or assignees.
This document and the information contained herein is provided on an
"AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
Acknowledgement
Funding for the RFC Editor function is currently provided by the
Internet Society.
 End of changes. 

This html diff was produced by rfcdiff 1.25, available from http://www.levkowetz.com/ietf/tools/rfcdiff/