draft-ietf-mpls-explicit-null-00.txt   draft-ietf-mpls-explicit-null-01.txt 
Network Working Group Eric C. Rosen Network Working Group Eric C. Rosen
Internet Draft Cisco Systems, Inc. Internet Draft Cisco Systems, Inc.
Expiration Date: September 2004 Expiration Date: October 2004
Updates RFC 3032 Updates RFC 3032
March 2004 April 2004
Removing a Restriction on the use of MPLS Explicit NULL Removing a Restriction on the use of MPLS Explicit NULL
draft-ietf-mpls-explicit-null-00.txt draft-ietf-mpls-explicit-null-01.txt
Status of this Memo Status of this Memo
This document is an Internet-Draft and is in full conformance with This document is an Internet-Draft and is in full conformance with
all provisions of Section 10 of RFC2026. all provisions of Section 10 of RFC2026.
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF), its areas, and its working groups. Note that other Task Force (IETF), its areas, and its working groups. Note that other
groups may also distribute working documents as Internet-Drafts. groups may also distribute working documents as Internet-Drafts.
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reserved label value known as "IPv6 Explicit NULL". Previously, reserved label value known as "IPv6 Explicit NULL". Previously,
these labels were only legal when they occurred at the bottom of the these labels were only legal when they occurred at the bottom of the
MPLS label stack. This restriction is now removed, so that these MPLS label stack. This restriction is now removed, so that these
label values may legally occur anywhere in the stack. label values may legally occur anywhere in the stack.
Contents Contents
1 Introduction ......................................... 2 1 Introduction ......................................... 2
2 Detail of Change ..................................... 2 2 Detail of Change ..................................... 2
3 Reasons for Change ................................... 4 3 Reasons for Change ................................... 4
4 Acknowledgments ...................................... 5 4 Security Considerations .............................. 5
5 Normative References ................................. 5 5 Acknowledgments ...................................... 5
6 Informative References ............................... 5 6 Normative References ................................. 6
7 Author's Address ..................................... 6 7 Informative References ............................... 6
8 Intellectual Property Notice ......................... 6 8 Author's Address ..................................... 6
9 Copyright Notice ..................................... 6 9 Intellectual Property Notice ......................... 6
10 Copyright Notice ..................................... 7
1. Introduction 1. Introduction
RFC 3032 defines a reserved label value known as "IPv4 Explicit NULL" RFC 3032 defines a reserved label value known as "IPv4 Explicit NULL"
and a reserved label value known as "IPv6 Explicit NULL". It states and a reserved label value known as "IPv6 Explicit NULL". It states
that these label values are only legal at the bottom of the MPLS that these label values are only legal at the bottom of the MPLS
label stack. However, no reason is given for this restriction. label stack. However, no reason is given for this restriction.
It has turned out that in practice there are some situations in which It has turned out that in practice there are some situations in which
it is useful to send MPLS packets which have Explicit NULL occur it is useful to send MPLS packets which have Explicit NULL occur
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using Explicit NULL enables the egress to determine immediately using Explicit NULL enables the egress to determine immediately
(i.e., without need for lookup in the Label Information Base) that (i.e., without need for lookup in the Label Information Base) that
the further forwarding of the packet is to be determined by whatever the further forwarding of the packet is to be determined by whatever
is below the label. Avoiding this lookup can have favorable is below the label. Avoiding this lookup can have favorable
implications on forwarding performance. implications on forwarding performance.
Removing the restriction that Explicit Null only occur at the bottom Removing the restriction that Explicit Null only occur at the bottom
of the stack is the simplest way to facilitate the proper operation of the stack is the simplest way to facilitate the proper operation
of the Pipe Model. of the Pipe Model.
4. Acknowledgments 4. Security Considerations
This document updates RFC 3032 by allowing Explicit NULL to occur at
any position in the label stack. This modification does not impose
any new security considerations beyond those discussed in RFC 3032.
5. Acknowledgments
Thanks to Rahul Aggarwal, Francois LeFaucheur, Yakov Rekhter, and Dan Thanks to Rahul Aggarwal, Francois LeFaucheur, Yakov Rekhter, and Dan
Tappan for their helpful comments. Tappan for their helpful comments.
5. Normative References 6. Normative References
[RFC3032] "MPLS Label Stack Encoding", Rosen, et. al., January 2001 [RFC3032] "MPLS Label Stack Encoding", Rosen, et. al., January 2001
6. Informative References 7. Informative References
[RFC3270] "Multi-Protocol Label Switching (MPLS) Support of [RFC3270] "Multi-Protocol Label Switching (MPLS) Support of
Differentiated Services", Le Faucheur, et. al., May 2002 Differentiated Services", Le Faucheur, et. al., May 2002
7. Author's Address 8. Author's Address
Eric C. Rosen Eric C. Rosen
Cisco Systems, Inc. Cisco Systems, Inc.
1414 Massachusetts Avenue 1414 Massachusetts Avenue
Boxborough, MA 01719 Boxborough, MA 01719
Email: erosen@cisco.com Email: erosen@cisco.com
8. Intellectual Property Notice 9. Intellectual Property Notice
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 of the technology described in pertain to the implementation or use of the technology described in
this document or the extent to which any license under such rights this document or the extent to which any license under such rights
might or might not be available; 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 of claims of rights made available for publication and any assurances of
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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 implementors or users of this specification can proprietary rights by implementors or users of this specification 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. Copyright Notice 10. Copyright Notice
"Copyright (C) The Internet Society (2004). All Rights Reserved. "Copyright (C) The Internet Society (2004). All Rights Reserved.
This document and translations of it may be copied and furnished to This document and translations of it may be copied and furnished to
others, and derivative works that comment on or otherwise explain it others, and derivative works that comment on or otherwise explain it
or assist in its implementation may be prepared, copied, published or assist in its implementation may be prepared, copied, published
and distributed, in whole or in part, without restriction of any and distributed, in whole or in part, without restriction of any
kind, provided that the above copyright notice and this paragraph are kind, provided that the above copyright notice and this paragraph are
included on all such copies and derivative works. However, this included on all such copies and derivative works. However, this
document itself may not be modified in any way, such as by removing document itself may not be modified in any way, such as by removing
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