VoIP

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
• Whats 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
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PDNS Query Processing Flow
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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.

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Telephony Delay Target E721
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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.

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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.

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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 (0.30.4s), international component
  (0.30.5s) 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).

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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
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VoIP Call Setup Case Studies

• Pure SIP or H.323 Call Flow (Eyers)
• Simulation based on Internet trace analysis
• 95th percentile of lt 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.

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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.

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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

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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

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Thank You!