VoIP & ENUM Performance Update - PDNS Server Testing and Telephony Delay Analysis

1. VoIP & Enum Performance Charles Shen, Henning Schulzrinne Dept. of Computer Science Columbia University New York, NY March 30, 2006

2. Status Update • PDNS ENUM Server Performance • Instrumenting PDNS source code done • Writing Performance Test Tool done • Tests at Columbia in analysis phase • Ready to port to Fibernet Phonomenun infrastructure for tests • VoIP/Enum call setup delay • Studied existing work on call setup delay in both PSTN and VoIP world • Ready for next step measurement

3. Outline • ENUM query performance • Enumperf tool • PDNS internal • What’s being measured • PSTN/ISDN and VoIP call setup delay • Targets values • Expectations • Case studies

4. Enumperf • Testing scripts we wrote, built on PDNS, Nominum QueryPerf, and modeled from SIPstone. • Supply parameters through the configuration file, the scripts handle the tests and output result curves at the end. • Output parsing is currently specific to PDNS. Not difficult to adapt it to be used with other authoritative DNS servers.

5. PDNS Internal Thread View Server control input server control listening Main Thread Query input Distributor Query Listening N threads to serve queries DB Pkt Cache Query Cache

6. PDNS Query Processing Flow

7. Things being investigated • Three types of queries • With matching records • No matching records, but with subdomain SOA • No matching records, no matching subdomain SOA • Bottom line performance (no caching) • Caching effect • PDNS Packet Cache • PDNS Query Cache • MySQL Cache • Effect of number of threads • Effect of database scaling • Effect of Collocated vs. Separate MySQL/PDNS Server • Anything else?

8. Telephony Setup Delay Definitions • Post-dialing delay (aka post-selection delay) • interval between entering the last dialed digit and receiving ringback. • Dial-to-ring delay • the interval between entering the last dialed digit and when the callee's phone starts to ring. • Answer-Signal Delay • interval between when callee picks-up the phone, and the time the caller receives indication of this. • Call Release Delay • interval between when the releasing party hangs-up and the time he can initiate/receive a new call.

9. Telephony Delay Target E721

10. Telephony Delay Target (Cont) • Based on overall target values in ITU-T E721, E723 provides • delay target values for SS7 Initial Addressing Message (IAM) and Answer Message (ANM) • partition for national and international portions

11. Intelligent Network Service Delay • ITU-T E724 defines incremental post-selection delay for processing IN services. • Such as database query, call redirection, multiple setup attempts, multiple processing locations, user interaction with the network, non-call related messaging. • 12s 99th Percentile for processing all IN services in local connections. • 4s mean delay for a single IN service for which the caller is unaware that IN processing is involve led (e.g. call forwarding) • Rest undefined.

12. Reference Connection Model • Reference connection model correlates delays incurred in each network component with E2E delay. • E723 specifies basic reference connection for NISDN. • Q709 specifies a more detailed Hypothetical Signaling Reference Connection model (HSRC) that: • contains national components and international components. • international working consists of one international and two national components. • the size of the country roughly defined as large or average • the respective number of nodes in each components. • E728 specifies the reference connection for BISDN signaling.

13. Delay Expectations from Users • A no-longer-available ATT link said to have reported that calls in US typically set up in 1-2 seconds. • An expired Internet Draft estimates the international call expectation to be roughly less than three times of the national call 2.5-5s. (based on maximum number of nodes in connection model) • A Nominum white paper says PSTN call establishment is expected to take less than 200 milliseconds. • ITU-T E724 describes mean user threshold for IN: • processing all IN Services: 3.5s in local and 4.5s in toll connections • Single IN service 1.5s for caller unaware services and 1.0 s for freephone-type services.

14. Computing Telephony Delay • Cross Switch Delay • Q725 (processing intensive/simple messages); • Telecordia spec (ISUP etc. Q931 message types); • Q766 (IAM, ANM etc) • Cross STP Delay • Processor Handling time - Q706 • Outgoing link delay (queuing + emission) – Q706 • Signaling link propagation delay – Q706 • E2e - Reference connection Model, e.g. Q709 • Call setup - Signaling exchange flow, SS7

15. Case Studies • Case I HSRC Q709 • Used Q706 and Q725/Q766 • maximum single message signaling delays for simple/intensive message in each national component (0.3~0.4s), international component (0.3~0.5s) and e2e (range of 1s). • Adding Message specific delay values to get delays for specific message (rather than just processing simple/intensive). (ID ref) • Consideration of database query delay (Q709).

16. Case Studies (cont.) • Case II BISDN Q728 • Used Q706 and Q725. • IAM (0.8/1.5/2.5) and ANM (0.5/1.0/1.8) mean for local, toll, international. • Case III PLMS Q771 • The E721 delay targets were assumed for the fixed network • Added Authentication, paging/alerting, routing number transfer delays. • 9-11-14 for F-M; 5.5-7.5-10.5 for M-F and 11.5-13.5-16.5 for M-M for local – toll – international connections.

17. Mapping Delay to VoIP world

18. VoIP Call Setup Case Studies • Pure SIP or H.323 Call Flow (Eyers) • Simulation based on Internet trace analysis • 95th percentile of < 1 s mostly achieved for simple SIP setups • Results vary for more complex paths or over the public Internet. • Compared with TCP-based H323 call setup, retransmission timer is important.

19. VoIP Call Setup Case Studies • SIP call setup in 3GPP (Kist) • Based on traces and added DNS delay estimation • Applied in 3GPP architecture with roaming • Simulation shows a mean delay of around 1800ms. • SIP call setup in 3GPP rel.99. (Curcio) • Simulation shows call setup over 3GPP rel99 emulator is close to that in national Intranet calls. Delay below 100ms. • call setup over emulated low bit-rate channel (up to 2kbps) is below 1 second.

20. Wrap-up Remarks • Make the target of VoIP calls no worse than those of PSTN/ISDN. • E721 target values seem to be longer than what many case studies have shown. • Allocation of delay budget depends on the VoIP call architecture and whether PSTN is involved, may refer to PSTN national/ international allocation for various VoIP network domains. • Delay Measurement Traces • Traffic model and link loading for Queuing analysis

21. To be discussed • ENUM query measurement • Detailed logistics to test ENUM in Fibernet infrastructure and the testing plan. • Call setup delay • The architecture assumption for end-to-end VoIP/ENUM network for call setup delay analysis. • The measurement proposal – what to measure (capacity? Delay?) and the scale (end-to-end? Components?) • Anything else that might be interested

22. Thank You!