MPLS Upstream Label Assignment and Context-Specific Label Space
RFC 5331
| Document | Type |
RFC - Proposed Standard
(August 2008; Errata)
Updated by RFC 7274
|
|
|---|---|---|---|
| Last updated | 2015-10-14 | ||
| Stream | IETF | ||
| Formats | plain text pdf html 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
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