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

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

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

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.

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

PDNS Query Processing Flow

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?

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.

Telephony Delay Target E721

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 TotalInternationalNational IAM ANM

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 99 th 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.

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.

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.

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

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).

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 for F-M; for M-F and for M-M for local – toll – international connections.

Mapping Delay to VoIP world

VoIP Call Setup Case Studies Pure SIP or H.323 Call Flow (Eyers) Simulation based on Internet trace analysis 95 th 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.

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.

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

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

Thank You!