70 likes | 212 Views
draft-frost-pwe3-timing-pw-reqs-00. IETF 63 PWE3 Working Group Paris, August 2005. Why do we need this draft?. Purpose: To define the requirements of a protocol suitable for conveying Timing and Synchronization over Pseudo-Wires Haven’t we done this already (e.g. TDM PWs with timing)?
E N D
draft-frost-pwe3-timing-pw-reqs-00 IETF 63 PWE3 Working Group Paris, August 2005
Why do we need this draft? • Purpose: To define the requirements of a protocol suitable for conveying Timing and Synchronization over Pseudo-Wires • Haven’t we done this already (e.g. TDM PWs with timing)? • there are applications for more general timing distribution, outside the TDM context • some applications require absolute time alignment, not just phase and frequency • separating the transport of timing and data allows improvement in the quality of the recovered clock • Aren’t there existing solutions (e.g. NTP, IEEE1588)? • these describe how to carry timing across a LAN or the internet • they don’t explain how to distribute timing over PW services • they may be candidates for a protocol to be re-used over a timing PW
Potential Applications • There are many applications that require distribution of accurate synchronization and timing: • Industrial applications • Real-time services • Packet voice and video • Telecom applications • Synchronization of IP PBXs or Voice Gateways • Synchronization of cellular base-stations • TDM emulation • Improvement in timing quality over what can be achieved with existing TDM PWs
Possible Timing PW scenario ~ PRS timing attachment circuits Secondary Time Server ~ PRS timing pseudo-wires PE PE timing pseudo-wires Primary Time Server Carrier Packet Network tunnel tunnel PE PE CE timing attachment circuits CE CE CE
Main Requirements • Performance • Requirements are application-specific, and are defined in the normative references for the applications • For example, G.pactiming is in the process of specifying the timing performance requirements for wired TDM emulation • Connectivity and compatibility • Robustness • Should be robust in the presence of common PSN error conditions • Redundancy • Should be able to monitor and switch over to alternative timing sources • Needs an indication of the quality of timing sources • Security • Authentication of timing sources
Comparison of draft-ietf-ntp-reqs-00 and draft-frost-timing-pw-reqs-00
SIMPLY COMMUNICATING c e s o p . z a r l i n k . c o m w w w . z a r l i n k . c o m