Time Division Multiplexing over IP (TDMoIP)
RFC 5087
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
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