MPLS-TP Packet Loss and Delay Measurement draft-frost-mpls-tp-loss-delay-00

1. IETF 76 November 2009 MPLS-TP MPLS-TP Packet Loss and Delay Measurement draft-frost-mpls-tp-loss-delay-00 Dan Frost danfrost@cisco.com Stewart Bryant stbryant@cisco.com

2. Protocol mechanisms to enable efficient and accurate measurement of • One-way and Two-way Packet Delay • Packet Loss for MPLS-TP PWs, LSPs, and Sections • Applicable to • Bidirectional point-to-point • Unidirectional point-to-point • Unidirectional point-to-multipoint MPLS-TP LSPs The Problem

3. Accurate Delay Measurement (DM) and Loss Measurement (LM) may require hardware timestamping and “counterstamping” support • Protocol design should support efficient hardware packet identification and processing • Protocol should be simple, streamlined and fit to purpose • Multiple timestamp formats in use in deployed networks and devices: NTP, IEEE 1588 v1/v2 Considerations

4. LM/DM approach follows basic measurement approach of ITU-T Recommendation Y.1731, adapted for MPLS-TP • LM/DM messages flow over the Generic Associated Channel (G-ACh) of MPLS-TP PWs, LSPs, and Sections • Only two message types: LM and DM. Packet formats are similar and can easily be combined into a third compound message type that performs both functions • DM mechanism useful even without hardware support, but LM without hw support may require a different approach. • Other LM approaches include using existing OAM messages as a proxy for client packets to measure loss, and sustained invasive generation of test messages. • Currently out of scope of this draft, but may be worth exploring in parallel • DM supports multiple timestamp formats Approach

5. Bidirectional Connection: Measurement carried out at the initiator • Unidirectional Connection: Measurement carried out either at the receiver or (if a backward out-of-band link is available) the initiator • DM message contains 4 timestamp fields for T1-T4 • LM message contains 4 counter fields for initiator/responder Tx/Rx packet counts • DM protocol is stateless • LM protocol is “almost” stateless: loss is measured as a delta between messages Measurement Model

6. Very simple mechanism to permit interop between devices with different preferred timestamp formats • DM messages include three 4-bit fields that specify: • Querier Timestamp Format • Responder Timestamp Format • Responder’s Preferred Timestamp Format • Querier sets QTF in the initial message to its preferred format. Responder sets RTF in the response either to QTF (if it can support it) or else to RPTF. • Querier now knows the state of the world and can decide what to do • Support for multiple timestamp formats is OPTIONAL. For an implementation that supports only one format, this procedure reduces to a no-op or single format compatibility test. Timestamp Formats

7. Say more about P2MP measurement options: measurement at TTL radii, message consolidation for multi-level monitoring • Clarify LM/DM apply on a per-QoS-class basis • Decide best way to handle lost/duplicated/out-of-order LM messages and misordering of data traffic relative to LM messages; adjust packet format accordingly (sequence number / timestamp) • Determine/document approach for handling metadata such as node/connection identifiers and authentication keys • Collaboration, comments and text welcome! Work In Progress / Open Issues

8. 広島市 76 Thank you!