1. University of Wollongong AUSTRALIA The Institute for Telecommunications and Information Technology Research (TITR) 1 Call Setup Delay Modelling for Internet Telephony Dr. Tony Eyers TITR University of Wollongong Australia June, 1999

2. University of Wollongong AUSTRALIA The Institute for Telecommunications and Information Technology Research (TITR) 2 Where is Wollongong?

3. University of Wollongong AUSTRALIA The Institute for Telecommunications and Information Technology Research (TITR) 3 Research at Wollongong u Wollongong University is regarded by the Industry as Australia’s premier IT&T R&D site The Institute for Telecommunications and Information Technology Research (TITR) operates within the University TITR has successfully undertaken over $13 million worth of R&D for Industry during the past 5 years Around 50 full time researchers (including graduate students) Major industrial funding sources include: Telstra, Motorola, Vodafone, Ericsson, BNR Research areas: QOS issues for fixed and mobile networks, Audio coding, Security

4. University of Wollongong AUSTRALIA The Institute for Telecommunications and Information Technology Research (TITR) 4 Internet Telephony QOS u Major focus on protocol development H.323, SIP/SDP RTP Gateway Location Protocol (GLP) u Variable QOS As yet, no standard definitions IETF work underway to adapt ITU performance targets u Current work on Internet voice QOS focus on UDP delay over public Internet u Current work on Internet call setup delay some IETF drafts on IP signalling transport [Elawid97] considers delay performance of a Lucent H.323 exchange

5. University of Wollongong AUSTRALIA The Institute for Telecommunications and Information Technology Research (TITR) 5 Problem Statement u Determine Internet Telephony Call Setup delay distribution, over public Internet Measure Post Dial delay, ie between sending Setup message and receiving Alerting message Key parameters -propagation delay -queueing delay -retransmission delay Processing delay not considered Aim: compare SIP and H.323 setup delay performance -key difference: recovery scheme for lost messages -SIP uses UDP, with timeout/retransmission mechanism -H.323 uses TCP

6. University of Wollongong AUSTRALIA The Institute for Telecommunications and Information Technology Research (TITR) 6 Current Objectives for Call Setup Delay u ITU Rec E.721 (1988) Mean post dial delay  3 seconds 95th percentile for further study u ITU rec Q.709 maxm number of STP/SPs for national/international component of connections u ITU rec Q.725 (and Telcordia GR-1364) mean and 95th percentiles for switch response delay (ie IAM, ANM message processing) u ITU Q.706 STP message transfer delay u New IETF draft combines these to form call setup delay targets eg large country: 95% of connections have mean of 3040-3158 msec, 95th %ile 3947-3615msec

7. University of Wollongong AUSTRALIA The Institute for Telecommunications and Information Technology Research (TITR) 7 Call Setup Delay Observations u Signalling Queueing delay not included in IETF draft Queueing delay includes transmission/retransmission delays SS7 queueing delay targets outlined in ITU rec E.733 u IETF call setup delay target implies routing and resource reservation u My study ignores these, focuses on queueing delays only results provide a lower bound for Call Setup delay

8. University of Wollongong AUSTRALIA The Institute for Telecommunications and Information Technology Research (TITR) 8 Call Setup: SIP INVITE PROVISIONAL RESPONSE Message lost timeout INVITE PROVISIONAL RESPONSE Call Established

9. University of Wollongong AUSTRALIA The Institute for Telecommunications and Information Technology Research (TITR) 9 Call Setup: SIP u Provisional response retransmissions prompted by INVITE arrivals an optional mechanism is provided for provisonal response timeouts u Final response messages always timeout Final responses also retransmitted when retransmitted INVITES arrive u SIP timeouts 500 msec initially Retransmissions increase timeout by factor of two Maximum value 4 seconds Retransmissions stop after 7 attempts

10. University of Wollongong AUSTRALIA The Institute for Telecommunications and Information Technology Research (TITR) 10 Call Setup: H.323 (Fast Connect) TCP SYN TCP ACK SETUP CONNECT Call Established

11. University of Wollongong AUSTRALIA The Institute for Telecommunications and Information Technology Research (TITR) 11 H.323 Call Setup u TCP connection establishment adds additional round trip propagation delay SYN retransmission delay u SYN, SETUP, CONNECT use ‘standard’ TCP timeouts u TCP timeouts Recommended initial value 3 seconds (RFC 1122) Some implementations start at 6 seconds [Stevens94], Solaris allows initial timeout to be set Timeout value increases by a factor of two for each retransmission Maximum number of retransmissions varies between implementations

12. University of Wollongong AUSTRALIA The Institute for Telecommunications and Information Technology Research (TITR) 12 Simulation: Modelling Scenarios 1) SIP: INVITE - Provisional Response messages can pass through stateless proxies 2) SIP: INVITE - Redirect Server, then INVITE - Provisional Response 3) H.323 Fast Connect TCP connection setup Exchange H.323 SETUP/CONNECT messages TCP timeouts assumed to be the same as the SIP ones

13. University of Wollongong AUSTRALIA The Institute for Telecommunications and Information Technology Research (TITR) 13 UDP Delay: the Surveyor Project u Run byAdvanced Networks and Services u Measures one way UDP delay Currently 38 sites (mostly USA, some in Europe, Korea, New Zealand) Each site exchanges 4x40 byte UDP packets each second (2 each way) One way delay measured, resolution 50 usec Packet loss also recorded u Surveyor site provides delay/loss histograms for each day, for all site pairs (measurements began in 1997) located at http://www.advanced.org/csg-ippm/ u Have been able to access the Surveyor traces for this project provide delay/loss for each UDP packet

14. University of Wollongong AUSTRALIA The Institute for Telecommunications and Information Technology Research (TITR) 14 Simulation Methodology u Periods of up to 1 hour are examined u Instantaneous Delay/Loss probabilities constructed from trace records two state error model used 200 sample and 20 sample moving windows maintained -if 20 sample window has one error or less, current error prob. calculated from previous 200 samples -otherwise bad state assumed, error prob. calculated from 20 sample window u Simulated Calls then arrive 50/sec, poisson call arrivals u Call Setup Delay distribution/Call loss rate recorded over simulated interval u Statistics for a one hour period generated from  6000000 calls

15. University of Wollongong AUSTRALIA The Institute for Telecommunications and Information Technology Research (TITR) 15 Case Study u Simulation runs over the first 90 business days in 1999 60 minutes per day starting at 16:00 u Source Destination pairs New York-Boston New York-Chicago New York-West Coast New York-Hawaii u Variations All calls visit a redirect server in Washington DC All calls visit a redirect server in Washington DC, then transit a proxy server in Indiana H.323 (eg TCP) u Plots show 0th percentile (‘+’) and 95th percentile of call setup delay (‘o’)

16. University of Wollongong AUSTRALIA The Institute for Telecommunications and Information Technology Research (TITR) 16 New York/Boston

17. University of Wollongong AUSTRALIA The Institute for Telecommunications and Information Technology Research (TITR) 17 New York/Chicago

18. University of Wollongong AUSTRALIA The Institute for Telecommunications and Information Technology Research (TITR) 18 New York/West Coast

19. University of Wollongong AUSTRALIA The Institute for Telecommunications and Information Technology Research (TITR) 19 New York/Hawaii

20. University of Wollongong AUSTRALIA The Institute for Telecommunications and Information Technology Research (TITR) 20 New York/Boston (DC redirect)

21. University of Wollongong AUSTRALIA The Institute for Telecommunications and Information Technology Research (TITR) 21 New York/Chicago (DC redirect)

22. University of Wollongong AUSTRALIA The Institute for Telecommunications and Information Technology Research (TITR) 22 New York/West Coast (DC redirect)

23. University of Wollongong AUSTRALIA The Institute for Telecommunications and Information Technology Research (TITR) 23 New York/Hawaii (DC redirect)

24. University of Wollongong AUSTRALIA The Institute for Telecommunications and Information Technology Research (TITR) 24 New York/Boston (DC redirect,via Indiana)

25. University of Wollongong AUSTRALIA The Institute for Telecommunications and Information Technology Research (TITR) 25 New York/Chicago (DC redirect, via Indiana)

26. University of Wollongong AUSTRALIA The Institute for Telecommunications and Information Technology Research (TITR) 26 New York/West Coast (DC redirect, via Indiana)

27. University of Wollongong AUSTRALIA The Institute for Telecommunications and Information Technology Research (TITR) 27 New York/Hawaii (DC redirect, via Indiana)

28. University of Wollongong AUSTRALIA The Institute for Telecommunications and Information Technology Research (TITR) 28 New York/Boston TCP comparison

29. University of Wollongong AUSTRALIA The Institute for Telecommunications and Information Technology Research (TITR) 29 New York/Chicago TCP Comparison

30. University of Wollongong AUSTRALIA The Institute for Telecommunications and Information Technology Research (TITR) 30 New York/West Coast TCP Comparison

31. University of Wollongong AUSTRALIA The Institute for Telecommunications and Information Technology Research (TITR) 31 New York/Hawaii TCP Comparison

32. University of Wollongong AUSTRALIA The Institute for Telecommunications and Information Technology Research (TITR) 32 Conclusions u 95th percentile of Call setup delays mostly under 1 second relatively small sample missing days may hide poor results relies on error probability modelling assumptions u 95th delay percentile determined by error threshold as additional paths are added (ie redirect servers/proxy servers), increased error probability eventually raises 95th percentile u TCP shows, in some cases, a marked increase in 95th delay percentile due to increased error probability arising from connection setup TCP delay will increase markedly if standard TCP timeout values used

33. University of Wollongong AUSTRALIA The Institute for Telecommunications and Information Technology Research (TITR) 33 Future Work u This project Extend experiments to consider -TCP/UDP performance during very high error periods -Full H.323 call setup Develop analytical model for delay/loss -based on mean error rate Determine effect/prevalence of bursty errors u Related Projects Determine targets for signalling message transport delay (as a component of overall call setup delay) Design procedures for dedicated IP signalling networks

34. University of Wollongong AUSTRALIA The Institute for Telecommunications and Information Technology Research (TITR) 34 New York-Indiana

35. University of Wollongong AUSTRALIA The Institute for Telecommunications and Information Technology Research (TITR) 35 New York-Boston (error window =600)

36. University of Wollongong AUSTRALIA The Institute for Telecommunications and Information Technology Research (TITR) 36 New York-Boston (error window = 4)

37. University of Wollongong AUSTRALIA The Institute for Telecommunications and Information Technology Research (TITR) 37 New York-Chicago (error window = 600)

38. University of Wollongong AUSTRALIA The Institute for Telecommunications and Information Technology Research (TITR) 38 New York-Chicago (error window = 4)