Structure-Agnostic Time Division Multiplexing (TDM) over Packet (SAToP)
RFC 4553

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Network Working Group                                 A. Vainshtein, Ed.
Request for Comments: 4553                               Axerra Networks
Category: Standards Track                                 YJ. Stein, Ed.
                                                 RAD Data Communications
                                                               June 2006

          Structure-Agnostic Time Division Multiplexing (TDM)
                          over Packet (SAToP)

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 (2006).

Abstract

   This document describes a pseudowire encapsulation for Time Division
   Multiplexing (TDM) bit-streams (T1, E1, T3, E3) that disregards any
   structure that may be imposed on these streams, in particular the
   structure imposed by the standard TDM framing.

Vainshtein & Stein          Standards Track                     [Page 1]
RFC 4553           Structure-Agnostic TDM over Packet          June 2006

Table of Contents

   1. Introduction ....................................................3
   2. Terminology and Reference Models ................................3
      2.1. Terminology ................................................3
      2.2. Reference Models ...........................................4
   3. Emulated Services ...............................................4
   4. SAToP Encapsulation Layer .......................................5
      4.1. SAToP Packet Format ........................................5
      4.2. PSN and PW Demultiplexing Layer Headers ....................5
      4.3. SAToP Header ...............................................6
           4.3.1. Usage and Structure of the Control Word .............8
           4.3.2. Usage of RTP Header .................................9
   5. SAToP Payload Layer ............................................10
      5.1. General Payloads ..........................................10
      5.2. Octet-Aligned T1 ..........................................11
   6. SAToP Operation ................................................12
      6.1. Common Considerations .....................................12
      6.2. IWF Operation .............................................12
           6.2.1. PSN-Bound Direction ................................12
           6.2.2. CE-Bound Direction .................................13
      6.3. SAToP Defects .............................................14
      6.4. SAToP PW Performance Monitoring ...........................15
   7. Quality of Service (QoS) Issues ................................16
   8. Congestion Control .............................................16
   9. Security Considerations ........................................18
   10. Applicability Statement .......................................18
   11. IANA Considerations ...........................................20
   12. Acknowledgements ..............................................20
   13. Co-Authors ....................................................20
   14. Normative References ..........................................21
   15. Informative References ........................................22
   Appendix A: Old Mode of SAToP Encapsulation over L2TPv3 ...........24
   Appendix B: Parameters That MUST Be Agreed upon during the PW
               Setup .................................................24

Vainshtein & Stein          Standards Track                     [Page 2]
RFC 4553           Structure-Agnostic TDM over Packet          June 2006

1.  Introduction

   This document describes a method for encapsulating Time Division
   Multiplexing (TDM) bit-streams (T1, E1, T3, E3) as pseudowires over
   packet-switching networks (PSN).  It addresses only structure-
   agnostic transport, i.e., the protocol completely disregards any
   structure that may possibly be imposed on these signals, in
   particular the structure imposed by standard TDM framing [G.704].
   This emulation is referred to as "emulation of unstructured TDM
   circuits" in [RFC4197] and suits applications where the PEs have no
   need to interpret TDM data or to participate in the TDM signaling.

   The SAToP solution presented in this document conforms to the PWE3
   architecture described in [RFC3985] and satisfies both the relevant
   general requirements put forward in [RFC3916] and specific
   requirements for unstructured TDM signals presented in [RFC4197].

   As with all PWs, SAToP PWs may be manually configured or set up using
   the PWE3 control protocol [RFC4447].  Extensions to the PWE3 control