1. 1 draft-ietf-ippm-loss-episode-metrics-00 Loss Episode Metrics for IPPM Nick Duffield, Al Morton, AT&T Joel Sommers, Colgate University IETF 79, Beijing, 11/8/2010

2. 2 Agenda  Changes since IETF 77  One page summary of draft  Q&A from last IETF  Conclusion

3. 3 Changes since IETF 77,78  Draft adopted as WG item  Previous individual draft draft-duffield-ippm-burst-loss-metrics  IPR disclosure  Supersedes IPR disclosure for previous individual draft  https://datatracker.ietf.org/ipr/1354/ https://datatracker.ietf.org/ipr/1354/

4. 4 A one page summary of the draft  Fact: packets in a flow are not generally lost independently  Motivation: metrics of temporal structure of packet loss  Target use: SLAs, application requirements (e.g VoIP)  Object of study: loss episodes (of consecutively loss packets)  Metrics: average duration and frequency of loss episodes  Methodology: bi-packet probes, sent as discrete Poisson stream  Analysis: metrics depend only on frequencies of probe outcomes  4 possible outcomes (0,0), (0,1), (1,1), (1,0) where 1 = lost, 0 = not lost  Summary: extension of RFC 2680 to case of correlated loss XXXX X XX X Frequent small glitches vs. local burst (at same average loss rate) (0,0)(0,1)(1,1)(0,0)

5. 5 Relation to Gilbert Model  Metric maps to 2-state Gilbert model  Draft seeks to provide simplest extension of RFC2680 that can capture dependent loss without reference to a model  Possible work for future WG drafts?  Standardize specific measurement methodology for estimating the parameters of the 4-state Gilbert model:  It should be coordinated with related work, such as RFC 3611 (RTCP- XR) and ITU-T Rec. G.1020

6. 6 Sampling Packet Pairs vs. Capture All Packets  Draft Approach: Sample packet pairs.  Sample transitions between runs of lost/not_lost packets  These are sufficient to compute draft metrics Don’t need to capture all packets in a loss episode  Relation to other measurement methodologies 1.Passive measurement of existing stream Yes, you can measure all packets (work on Stream-Repair metrics in SG12) Equivalent to setting launch probability q = 1 Metrics are identical with computation based on runs of successive losses. 2.Active probing ANY probing scheme samples loss at a sequence of instants –Example RFC 2680 Packet pairs are more efficient at sampling the transitions –For a given accuracy, less probing bandwidth required than for stream of single packets

7. 7 Conclusion  Please read the draft and comment  Please post any questions from this WG session to the mailing list