Time Division Multiplexing over IP (TDMoIP)
RFC 5087

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Network Working Group                                        Y(J). Stein
Request for Comments: 5087                                   R. Shashoua
Category: Informational                                        R. Insler
                                                                M. Anavi
                                                 RAD Data Communications
                                                           December 2007

              Time Division Multiplexing over IP (TDMoIP)

Status of This Memo

   This memo provides information for the Internet community.  It does
   not specify an Internet standard of any kind.  Distribution of this
   memo is unlimited.

Abstract

   Time Division Multiplexing over IP (TDMoIP) is a structure-aware
   method for transporting Time Division Multiplexed (TDM) signals using
   pseudowires (PWs).  Being structure-aware, TDMoIP is able to ensure
   TDM structure integrity, and thus withstand network degradations
   better than structure-agnostic transport.  Structure-aware methods
   can distinguish individual channels, enabling packet loss concealment
   and bandwidth conservation.  Accesibility of TDM signaling
   facilitates mechanisms that exploit or manipulate signaling.

Stein, et al.                Informational                      [Page 1]
RFC 5087                         TDMoIP                    December 2007

Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
   2.  TDM Structure and Structure-aware Transport  . . . . . . . . .  4
   3.  TDMoIP Encapsulation . . . . . . . . . . . . . . . . . . . . .  6
   4.  Encapsulation Details for Specific PSNs  . . . . . . . . . . .  9
     4.1.  UDP/IP . . . . . . . . . . . . . . . . . . . . . . . . . .  9
     4.2.  MPLS . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
     4.3.  L2TPv3 . . . . . . . . . . . . . . . . . . . . . . . . . . 14
     4.4.  Ethernet . . . . . . . . . . . . . . . . . . . . . . . . . 15
   5.  TDMoIP Payload Types . . . . . . . . . . . . . . . . . . . . . 17
     5.1.  AAL1 Format Payload  . . . . . . . . . . . . . . . . . . . 18
     5.2.  AAL2 Format Payload  . . . . . . . . . . . . . . . . . . . 19
     5.3.  HDLC Format Payload  . . . . . . . . . . . . . . . . . . . 20
   6.  TDMoIP Defect Handling . . . . . . . . . . . . . . . . . . . . 21
   7.  Implementation Issues  . . . . . . . . . . . . . . . . . . . . 24
     7.1.  Jitter and Packet Loss . . . . . . . . . . . . . . . . . . 24
     7.2.  Timing Recovery  . . . . . . . . . . . . . . . . . . . . . 25
     7.3.  Congestion Control . . . . . . . . . . . . . . . . . . . . 26
   8.  Security Considerations  . . . . . . . . . . . . . . . . . . . 27
   9.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 28
   10. Applicability Statement  . . . . . . . . . . . . . . . . . . . 28
   11. Acknowledgments  . . . . . . . . . . . . . . . . . . . . . . . 29
   Appendix A.  Sequence Number Processing (Informative)  . . . . . . 30
   Appendix B.  AAL1 Review (Informative) . . . . . . . . . . . . . . 32
   Appendix C.  AAL2 Review (Informative) . . . . . . . . . . . . . . 36
   Appendix D.  Performance Monitoring Mechanisms (Informative) . . . 38
     D.1.  TDMoIP Connectivity Verification . . . . . . . . . . . . . 38
     D.2.  OAM Packet Format  . . . . . . . . . . . . . . . . . . . . 39
   Appendix E.  Capabilities, Configuration and Statistics
                (Informative) . . . . . . . . . . . . . . . . . . . . 42
   References . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45
     Normative References . . . . . . . . . . . . . . . . . . . . . . 45
     Informative References . . . . . . . . . . . . . . . . . . . . . 47

Stein, et al.                Informational                      [Page 2]
RFC 5087                         TDMoIP                    December 2007

1.  Introduction

   Telephony traffic is conventionally carried over connection-oriented
   synchronous or plesiochronous links (loosely called TDM circuits
   herein).  With the proliferation of Packet Switched Networks (PSNs),
   transport of TDM services over PSN infrastructures has become
   desirable.  Emulation of TDM circuits over the PSN can be carried out
   using pseudowires (PWs), as described in the PWE3 architecture
   [RFC3985].  This emulation must maintain service quality of native
   TDM; in particular voice quality, latency, timing, and signaling
   features must be similar to those of existing TDM networks, as
   described in the TDM PW requirements document [RFC4197].

   Structure-Agnostic TDM over Packet (SAToP) [RFC4553] is a structure-
   agnostic protocol for transporting TDM over PSNs.  The present
   document details TDM over IP (TDMoIP), a structure-aware method for
   TDM transport.  In contrast to SAToP, structure-aware methods such as
   TDMoIP ensure the integrity of TDM structure and thus enable the PW
   to better withstand network degradations.  Individual multiplexed