MPLS Upstream Label Assignment and Context-Specific Label Space
RFC 5331
Document | Type |
RFC - Proposed Standard
(August 2008; Errata)
Updated by RFC 7274
|
|
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Authors | Yakov Rekhter , Rahul Aggarwal , Eric Rosen | ||
Last updated | 2020-01-21 | ||
Stream | IETF | ||
Formats | plain text html pdf htmlized with errata bibtex | ||
Reviews | |||
Stream | WG state | WG Document | |
Document shepherd | No shepherd assigned | ||
IESG | IESG state | RFC 5331 (Proposed Standard) | |
Consensus Boilerplate | Unknown | ||
Telechat date | |||
Responsible AD | Ross Callon | ||
Send notices to | (None) |
Network Working Group R. Aggarwal Request for Comments: 5331 Juniper Networks Category: Standards Track Y. Rekhter Juniper Networks E. Rosen Cisco Systems, Inc. August 2008 MPLS Upstream Label Assignment and Context-Specific Label Space 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 3031 limits the MPLS architecture to downstream-assigned MPLS labels. This document introduces the notion of upstream-assigned MPLS labels. It describes the procedures for upstream MPLS label assignment and introduces the concept of a "Context-Specific Label Space". Table of Contents 1. Introduction ....................................................2 2. Specification of Requirements ...................................2 3. Context-Specific Label Space ....................................2 4. Upstream Label Assignment .......................................3 4.1. Upstream-Assigned and Downstream-Assigned Labels ...........4 5. Assigning Upstream-Assigned Labels ..............................5 6. Distributing Upstream-Assigned Labels ...........................5 7. Upstream Neighbor Label Space ...................................6 8. Context Label on LANs ...........................................9 9. Usage of Upstream-Assigned Labels ..............................10 10. Security Considerations .......................................10 11. Acknowledgements ..............................................11 12. References ....................................................11 12.1. Normative References .....................................11 12.2. Informative References ...................................11 Aggarwal, et al. Standards Track [Page 1] RFC 5331 August 2008 1. Introduction RFC 3031 [RFC3031] limits the MPLS architecture to downstream- assigned MPLS labels. To quote from RFC 3031: "In the MPLS architecture, the decision to bind a particular label L to a particular Forwarding Equivalence Class (FEC) F is made by the Label Switching Router (LSR) which is DOWNSTREAM with respect to that binding. The downstream LSR then informs the upstream LSR of the binding. Thus labels are "downstream-assigned", and label bindings are distributed in the "downstream to upstream" direction." This document introduces the notion of upstream-assigned MPLS labels to the MPLS architecture. The procedures for upstream assignment of MPLS labels are described. RFC 3031 describes per-platform and per-interface label space. This document generalizes the latter to a "Context-Specific Label Space" and describes a "Neighbor Label Space" as an example of this. Upstream-assigned labels are always looked up in a context-specific label space. 2. Specification of Requirements The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in [RFC2119]. 3. Context-Specific Label Space RFC 3031 describes per-platform and per-interface label spaces. This document introduces the more general concept of a "Context-Specific Label Space". An LSR may maintain one or more context-specific label spaces. In general, labels MUST be looked up in the per-platform label space unless something about the context determines that a label be looked up in a particular context-specific label space. One example of a context-specific label space is the per-interface label space discussed in RFC 3031. When an MPLS packet is received over a particular interface, the top label of the packet may need to be looked up in the receiving interface's per-interface label space. In this case, the receiving interface is the context of the packet. Whether MPLS packets received over a particular interface need to have their top labels looked up in a per-interface label space depends on some characteristic or configuration of the interface. Aggarwal, et al. Standards Track [Page 2] RFC 5331 August 2008 Per-interface label space [RFC3031] is an example of a context-Show full document text