Network Working Group M. Townsley
Request for Comments: 4817 C. Pignataro
Category: Standards Track S. Wainner
Cisco Systems
T. Seely
Sprint Nextel
J. Young
March 2007
Encapsulation of MPLS over Layer 2 Tunneling Protocol Version 3
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.
Copyright Notice
Copyright (C) The IETF Trust (2007).
Abstract
The Layer 2 Tunneling Protocol, Version 3 (L2TPv3) defines a protocol
for tunneling a variety of payload types over IP networks. This
document defines how to carry an MPLS label stack and its payload
over the L2TPv3 data encapsulation. This enables an application that
traditionally requires an MPLS-enabled core network, to utilize an
L2TPv3 encapsulation over an IP network instead.
Townsley, et al. Standards Track [Page 1]
RFC 4817 MPLS over L2TPv3 March 2007
Table of Contents
1. Introduction ....................................................2
1.1. Specification of Requirements ..............................2
2. MPLS over L2TPv3 Encoding .......................................2
3. Assigning the L2TPv3 Session ID and Cookie ......................4
4. Applicability ...................................................4
5. Congestion Considerations .......................................6
6. Security Considerations .........................................6
6.1. In the Absence of IPsec ....................................7
6.2. Context Validation .........................................7
6.3. Securing the Tunnel with IPsec .............................8
7. Acknowledgements ................................................9
8. References .....................................................10
8.1. Normative References ......................................10
8.2. Informative References ....................................10
1. Introduction
This document defines how to encapsulate an MPLS label stack and its
payload inside the L2TPv3 tunnel payload. After defining the MPLS
over L2TPv3 encapsulation procedure, other MPLS over IP encapsulation
options, including IP, Generic Routing Encapsulation (GRE), and IPsec
are discussed in context with MPLS over L2TPv3 in an Applicability
section. This document only describes encapsulation and does not
concern itself with all possible MPLS-based applications that may be
enabled over L2TPv3.
1.1. Specification of Requirements
In this document, several words are used to signify the requirements
of the specification. These words are often capitalized. 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].
2. MPLS over L2TPv3 Encoding
MPLS over L2TPv3 allows tunneling of an MPLS stack [RFC3032] and its
payload over an IP network, utilizing the L2TPv3 encapsulation
defined in [RFC3931]. The MPLS Label Stack and payload are carried
in their entirety following IP (either IPv4 or IPv6) and L2TPv3
headers.
Townsley, et al. Standards Track [Page 2]
RFC 4817 MPLS over L2TPv3 March 2007
+-+-+-+-+-+-+-+-+-+-+
| IP |
+-+-+-+-+-+-+-+-+-+-+
| L2TPv3 |
+-+-+-+-+-+-+-+-+-+-+
| MPLS Label Stack |
+-+-+-+-+-+-+-+-+-+-+
| MPLS Payload |
+-+-+-+-+-+-+-+-+-+-+
Figure 2.1 MPLS Packet over L2TPv3/IP
The L2TPv3 encapsulation carrying a single MPLS label stack entry is
datatracker.ietf.org