Layer Two Tunneling Protocol - Version 3 (L2TPv3)
RFC 3931
Document | Type |
RFC - Proposed Standard
(March 2005; Errata)
Updated by RFC 5641
|
|
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Last updated | 2013-03-02 | ||
Stream | IETF | ||
Formats | plain text pdf html bibtex | ||
Stream | WG state | (None) | |
Document shepherd | No shepherd assigned | ||
IESG | IESG state | RFC 3931 (Proposed Standard) | |
Consensus Boilerplate | Unknown | ||
Telechat date | |||
Responsible AD | Thomas Narten | ||
Send notices to | <mark@townsley.net> |
Network Working Group J. Lau, Ed. Request for Comments: 3931 M. Townsley, Ed. Category: Standards Track Cisco Systems I. Goyret, Ed. Lucent Technologies March 2005 Layer Two Tunneling Protocol - Version 3 (L2TPv3) 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 Internet Society (2005). Abstract This document describes "version 3" of the Layer Two Tunneling Protocol (L2TPv3). L2TPv3 defines the base control protocol and encapsulation for tunneling multiple Layer 2 connections between two IP nodes. Additional documents detail the specifics for each data link type being emulated. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 1.1. Changes from RFC 2661. . . . . . . . . . . . . . . . . . 4 1.2. Specification of Requirements. . . . . . . . . . . . . . 4 1.3. Terminology. . . . . . . . . . . . . . . . . . . . . . . 5 2. Topology . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 3. Protocol Overview. . . . . . . . . . . . . . . . . . . . . . . 9 3.1. Control Message Types. . . . . . . . . . . . . . . . . . 10 3.2. L2TP Header Formats. . . . . . . . . . . . . . . . . . . 11 3.2.1. L2TP Control Message Header. . . . . . . . . . . 11 3.2.2. L2TP Data Message. . . . . . . . . . . . . . . . 12 3.3. Control Connection Management. . . . . . . . . . . . . . 13 3.3.1. Control Connection Establishment . . . . . . . . 14 3.3.2. Control Connection Teardown. . . . . . . . . . . 14 3.4. Session Management . . . . . . . . . . . . . . . . . . . 15 3.4.1. Session Establishment for an Incoming Call . . . 15 3.4.2. Session Establishment for an Outgoing Call . . . 15 Lau, et al. Standards Track [Page 1] RFC 3931 L2TPv3 March 2005 3.4.3. Session Teardown . . . . . . . . . . . . . . . . 16 4. Protocol Operation . . . . . . . . . . . . . . . . . . . . . . 16 4.1. L2TP Over Specific Packet-Switched Networks (PSNs) . . . 16 4.1.1. L2TPv3 over IP . . . . . . . . . . . . . . . . . 17 4.1.2. L2TP over UDP. . . . . . . . . . . . . . . . . . 18 4.1.3. L2TP and IPsec . . . . . . . . . . . . . . . . . 20 4.1.4. IP Fragmentation Issues. . . . . . . . . . . . . 21 4.2. Reliable Delivery of Control Messages. . . . . . . . . . 23 4.3. Control Message Authentication . . . . . . . . . . . . . 25 4.4. Keepalive (Hello). . . . . . . . . . . . . . . . . . . . 26 4.5. Forwarding Session Data Frames . . . . . . . . . . . . . 26 4.6. Default L2-Specific Sublayer . . . . . . . . . . . . . . 27 4.6.1. Sequencing Data Packets. . . . . . . . . . . . . 28 4.7. L2TPv2/v3 Interoperability and Migration . . . . . . . . 28 4.7.1. L2TPv3 over IP . . . . . . . . . . . . . . . . . 29 4.7.2. L2TPv3 over UDP. . . . . . . . . . . . . . . . . 29 4.7.3. Automatic L2TPv2 Fallback. . . . . . . . . . . . 29 5. Control Message Attribute Value Pairs. . . . . . . . . . . . . 30 5.1. AVP Format . . . . . . . . . . . . . . . . . . . . . . . 30 5.2. Mandatory AVPs and Setting the M Bit . . . . . . . . . . 32 5.3. Hiding of AVP Attribute Values . . . . . . . . . . . . . 33 5.4. AVP Summary. . . . . . . . . . . . . . . . . . . . . . . 36 5.4.1. General Control Message AVPs . . . . . . . . . . 36 5.4.2. Result and Error Codes . . . . . . . . . . . . . 40 5.4.3. Control Connection Management AVPs . . . . . . . 43 5.4.4. Session Management AVPs. . . . . . . . . . . . . 48 5.4.5. Circuit Status AVPs. . . . . . . . . . . . . . . 57 6. Control Connection Protocol Specification. . . . . . . . . . . 59 6.1. Start-Control-Connection-Request (SCCRQ) . . . . . . . . 60 6.2. Start-Control-Connection-Reply (SCCRP) . . . . . . . . . 60 6.3. Start-Control-Connection-Connected (SCCCN) . . . . . . . 61 6.4. Stop-Control-Connection-Notification (StopCCN) . . . . . 61 6.5. Hello (HELLO). . . . . . . . . . . . . . . . . . . . . . 61Show full document text