Explicit Congestion Marking in MPLS
RFC 5129
Document | Type |
RFC - Proposed Standard
(January 2008; No errata)
Updated by RFC 5462
Updates RFC 3032
|
|
---|---|---|---|
Authors | Bob Briscoe , Bruce Davie , June Tay | ||
Last updated | 2015-10-14 | ||
Stream | IETF | ||
Formats | plain text html pdf htmlized bibtex | ||
Reviews | |||
Stream | WG state | (None) | |
Document shepherd | No shepherd assigned | ||
IESG | IESG state | RFC 5129 (Proposed Standard) | |
Consensus Boilerplate | Unknown | ||
Telechat date | |||
Responsible AD | Lars Eggert | ||
Send notices to | mpls-chairs@ietf.org |
Network Working Group B. Davie Request for Comments: 5129 Cisco Systems, Inc. Category: Standards Track B. Briscoe J. Tay BT Research January 2008 Explicit Congestion Marking in MPLS Status of This Memo This document specifies an Internet standards track protocol for the Internet community, and requests discussion and suggestions for improvements. Please refer to the current edition of the "Internet Official Protocol Standards" (STD 1) for the standardization state and status of this protocol. Distribution of this memo is unlimited. Abstract RFC 3270 defines how to support the Diffserv architecture in MPLS networks, including how to encode Diffserv Code Points (DSCPs) in an MPLS header. DSCPs may be encoded in the EXP field, while other uses of that field are not precluded. RFC 3270 makes no statement about how Explicit Congestion Notification (ECN) marking might be encoded in the MPLS header. This document defines how an operator might define some of the EXP codepoints for explicit congestion notification, without precluding other uses. Davie, et al. Standards Track [Page 1] RFC 5129 ECN for MPLS January 2008 Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 1.1. Background . . . . . . . . . . . . . . . . . . . . . . . . 3 1.2. Intent . . . . . . . . . . . . . . . . . . . . . . . . . . 4 1.3. Terminology . . . . . . . . . . . . . . . . . . . . . . . 4 2. Use of MPLS EXP Field for ECN . . . . . . . . . . . . . . . . 5 3. Per-Domain ECT Checking . . . . . . . . . . . . . . . . . . . 7 4. ECN-Enabled MPLS Domain . . . . . . . . . . . . . . . . . . . 8 4.1. Pushing (Adding) One or More Labels to an IP Packet . . . 8 4.2. Pushing One or More Labels onto an MPLS Labeled Packet . . 8 4.3. Congestion Experienced in an Interior MPLS Node . . . . . 8 4.4. Crossing a Diffserv Domain Boundary . . . . . . . . . . . 8 4.5. Popping an MPLS Label (Not the End of the Stack) . . . . . 9 4.6. Popping the Last MPLS Label in the Stack . . . . . . . . . 9 4.7. Diffserv Tunneling Models . . . . . . . . . . . . . . . . 10 5. ECN-Disabled MPLS Domain . . . . . . . . . . . . . . . . . . . 10 6. The Use of More Codepoints with E-LSPs and L-LSPs . . . . . . 10 7. Relationship to Tunnel Behavior in RFC 3168 . . . . . . . . . 11 8. Deployment Considerations . . . . . . . . . . . . . . . . . . 11 8.1. Marking Non-ECN-Capable Packets . . . . . . . . . . . . . 11 8.2. Non-ECN-Capable Routers in an MPLS Domain . . . . . . . . 12 9. Example Uses . . . . . . . . . . . . . . . . . . . . . . . . . 13 9.1. RFC 3168-Style ECN . . . . . . . . . . . . . . . . . . . . 13 9.2. ECN Co-Existence with Diffserv E-LSPs . . . . . . . . . . 13 9.3. Congestion-Feedback-Based Traffic Engineering . . . . . . 14 9.4. PCN Flow Admission Control and Flow Termination . . . . . 14 10. Security Considerations . . . . . . . . . . . . . . . . . . . 14 11. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 15 Appendix A. Extension to Pre-Congestion Notification . . . . . . 16 A.1. Label Push onto IP Packet . . . . . . . . . . . . . . . . . 16 A.2. Pushing Additional MPLS Labels . . . . . . . . . . . . . . 16 A.3. Admission Control or Flow Termination Marking Inside MPLS Domain . . . . . . . . . . . . . . . . . . . . . . . . 17 A.4. Popping an MPLS Label (Not End of Stack) . . . . . . . . . 17 A.5. Popping the Last MPLS Label to Expose IP Header . . . . . . 17 Normative References . . . . . . . . . . . . . . . . . . . . . . . 18 Informative References . . . . . . . . . . . . . . . . . . . . . . 18 Davie, et al. Standards Track [Page 2] RFC 5129 ECN for MPLS January 2008 1. Introduction 1.1. Background [RFC3168] defines Explicit Congestion Notification (ECN) for IP. The primary purpose of ECN is to allow congestion to be signalled without dropping packets. [RFC3270] defines how to support the Diffserv architecture in MPLS networks, including how to encode Diffserv Code Points (DSCPs) in an MPLS header. DSCPs may be encoded in the EXP field, while other uses of that field are not precluded. RFC 3270 makes no statement about how Explicit Congestion Notification (ECN) marking might be encoded in the MPLS header. This document defines how an operator might define some of the EXPShow full document text