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Signalling of Modem-On-Hold status in Layer 2 Tunneling Protocol (L2TP)
RFC 3573

Document type: RFC - Proposed Standard (July 2003)
Document stream: IETF
Last updated: 2013-03-02
Other versions: plain text, pdf, html

IETF State: (None)
Consensus: Unknown
Document shepherd: No shepherd assigned

IESG State: RFC 3573 (Proposed Standard)
Responsible AD: Thomas Narten
IESG Note: 2003-07-17: RFC 3573 appears.
Send notices to: <mark@townsley.net>

Network Working Group                                          I. Goyret
Request for Comments: 3573                           Lucent Technologies
Category: Standards Track                                      July 2003

                   Signaling of Modem-On-Hold status
                  in Layer 2 Tunneling Protocol (L2TP)

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 (2003).  All Rights Reserved.

Abstract

   The Layer 2 Tunneling Protocol (L2TP) defines a mechanism for
   tunneling Point-to-Point Protocol (PPP) sessions.  It is common for
   these PPP sessions to be established using modems connected over the
   public switched telephone network.

   One of the standards governing modem operation defines procedures
   that enable a client modem to put the call on hold and later, re-
   establish the modem link with minimal delay and without having to
   redial.  While the modem call is on hold, the client phone line can
   be used to place or receive other calls.

   The L2TP base protocol does not provide any means to signal these
   events from the L2TP Access Controller (LAC), where the modem is
   physically connected, to the L2TP Network Server (LNS), where the PPP
   session is handled.

   This document describes a method to let the LNS know when a client
   modem connected to a LAC has placed the call on hold.

Goyret                      Standards Track                     [Page 1]
RFC 3573       Signaling of Modem-On-Hold status in L2TP       July 2003

Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  2
       1.1.  Specification of Requirements. . . . . . . . . . . . . .  3
       1.2.  Terminology. . . . . . . . . . . . . . . . . . . . . . .  3
   2.  Protocol Operation . . . . . . . . . . . . . . . . . . . . . .  3
       2.1.  Typical Modem on Hold Usage Scenario . . . . . . . . . .  4
       2.2.  Capability Negotiation . . . . . . . . . . . . . . . . .  4
       2.3.  Modem On-Hold. . . . . . . . . . . . . . . . . . . . . .  5
       2.4.  Modem Online . . . . . . . . . . . . . . . . . . . . . .  5
   3.  New Control Messages . . . . . . . . . . . . . . . . . . . . .  5
       3.1.  Modem-Status (MDMST) . . . . . . . . . . . . . . . . . .  5
   4.  New Attribute Value Pairs. . . . . . . . . . . . . . . . . . .  6
       4.1.  Modem On-Hold Capable AVP. . . . . . . . . . . . . . . .  6
       4.2.  Modem On-Hold Status AVP . . . . . . . . . . . . . . . .  6
   5.  Sample LNS Actions . . . . . . . . . . . . . . . . . . . . . .  7
   6.  IANA Considerations. . . . . . . . . . . . . . . . . . . . . .  8
   7.  Security Considerations. . . . . . . . . . . . . . . . . . . .  9
   8.  References . . . . . . . . . . . . . . . . . . . . . . . . . .  9
       8.1.  Normative References . . . . . . . . . . . . . . . . . .  9
       8.2.  Informative References . . . . . . . . . . . . . . . . .  9
   9.  Acknowledgments. . . . . . . . . . . . . . . . . . . . . . . . 10
   Appendix A: Vendor Specific Assignments. . . . . . . . . . . . . . 11
   Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 12
   Full Copyright Statement . . . . . . . . . . . . . . . . . . . . . 13

1.  Introduction

   The Layer 2 Tunneling Protocol (L2TP) [RFC2661] defines a general
   purpose mechanism for tunneling Point-to-Point Protocol (PPP) [STD51]
   sessions over various media.  By design, the operation of L2TP is
   insulated from the details of the media from which the PPP session
   originated.

   It is common for PPP sessions to be established using modems
   connected over the public switched telephone network.  The ITU-T
   Recommendation V.92 [V92] is one of the standards governing modem
   operation and it defines procedures that enable a client modem to put
   the call on hold and later, re-establish the modem link without
   having to redial.  While the modem call is on hold, the client phone
   line can be used for another phone call.

   The L2TP base protocol does not provide any means to signal these
   events from the L2TP Access Controller (LAC), where the modem is
   physically connected, to the L2TP Network Server (LNS), where the PPP
   session is handled.  It may be desirable for this information (which
   is available only on the LAC) to be provided to the LNS.

Goyret                      Standards Track                     [Page 2]
RFC 3573       Signaling of Modem-On-Hold status in L2TP       July 2003

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