RFC 3032 (rfc3032) - Page 2 of 23

MPLS Label Stack Encoding

RFC 3032               MPLS Label Stack Encoding            January 2001


Table of Contents

    1      Introduction  ...........................................  2
    1.1    Specification of Requirements  ..........................  3
    2      The Label Stack  ........................................  3
    2.1    Encoding the Label Stack  ...............................  3
    2.2    Determining the Network Layer Protocol  .................  5
    2.3    Generating ICMP Messages for Labeled IP Packets  ........  6
    2.3.1  Tunneling through a Transit Routing Domain  .............  7
    2.3.2  Tunneling Private Addresses through a Public Backbone  ..  7
    2.4    Processing the Time to Live Field  ......................  8
    2.4.1  Definitions  ............................................  8
    2.4.2  Protocol-independent rules  .............................  8
    2.4.3  IP-dependent rules  .....................................  9
    2.4.4  Translating Between Different Encapsulations  ...........  9
    3      Fragmentation and Path MTU Discovery  ................... 10
    3.1    Terminology  ............................................ 11
    3.2    Maximum Initially Labeled IP Datagram Size  ............. 12
    3.3    When are Labeled IP Datagrams Too Big?  ................. 13
    3.4    Processing Labeled IPv4 Datagrams which are Too Big  .... 13
    3.5    Processing Labeled IPv6 Datagrams which are Too Big  .... 14
    3.6    Implications with respect to Path MTU Discovery  ........ 15
    4      Transporting Labeled Packets over PPP  .................. 16
    4.1    Introduction  ........................................... 16
    4.2    A PPP Network Control Protocol for MPLS  ................ 17
    4.3    Sending Labeled Packets  ................................ 18
    4.4    Label Switching Control Protocol Configuration Options  . 18
    5      Transporting Labeled Packets over LAN Media  ............ 18
    6      IANA Considerations  .................................... 19
    7      Security Considerations  ................................ 19
    8      Intellectual Property  .................................. 19
    9      Authors' Addresses  ..................................... 20
   10      References  ............................................. 22
   11      Full Copyright Statement  ............................... 23

1. Introduction

   "Multi-Protocol Label Switching (MPLS)" [1] requires a set of
   procedures for augmenting network layer packets with "label stacks",
   thereby turning them into "labeled packets".  Routers which support
   MPLS are known as "Label Switching Routers", or "LSRs".  In order to
   transmit a labeled packet on a particular data link, an LSR must
   support an encoding technique which, given a label stack and a
   network layer packet, produces a labeled packet.







Rosen, et al.               Standards Track