H.323

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H.323

  1. 1. Video Development Initiative H.323 Jill Gemmill University of Alabama at Birmingham Doug Pearson Indiana University, Bloomington Tyler Johnson University of North Carolina, Chapel Hill
  2. 2. Internet2 Commons
  3. 3. Desktop & Room Systems • USB or Appliance • Affordable • User Friendly
  4. 4. What is H.323 ? An ITU-T standard for bi-directional exchange of voice, video, and data Applies to an IP network H.323 is a set of standards for group communication TCP Call setup & control UDP for audio/video
  5. 5. H.323 Audio Standards G711 Audio Codec Required Optional Codecs: G721, G723, G728, G729 Bottom Line – Good Audio Requires 64Kb
  6. 6. H.323 Video Standards Video is optional; H.261 required H.261 Picture Size – QCIF (176x44 pixels) is required – CIF (352x288 pixels) optional H.261 Compressed Data Rate – 64kbs – 1.9 kbs H.263 SQCIF, 4CIF, up to 16CIF (1408x1152 pixels)
  7. 7. Point-to-Point & Multipoint Point-to-Point Dial by IP address ! or alias user user Gatekeeper user user MCU user Multipoint user Register with Gatekeeper Connect through MCU
  8. 8. What is ViDe.Net? An international virtual network providing video teleconferencing, telephone and collaboration services over advanced networks. Architecture used in I2 Commons A voluntary collaboration and open forum A mesh of interconnected 75+ H.323 zones Zone: a collection of users administered by the site. RESULT: individual campuses and network providers interconnect, creating a seamless global environment for teleconferencing and collaboration.
  9. 9. Network Requirements Please use switched Ethernet Category 5 wiring is part of the above 10Mb/sec should be adequate for end points Much higher bandwidth at MCU (multiple 100Mb/sec cards in some systems)
  10. 10. Duplex Mismatch: the“Silent Performance Killer” A connection set for auto-negotiation, failing to see auto-negotiation at the other end, sets itself to the default – half-duplex. Auto-negotiation doesn’t always work, even when both sides are set to auto Auto-negotiation occurs repeatedly at intervals; what’s right the first time can be wrong later
  11. 11. Detecting Duplex Mismatch Show switch port stats; if mismatched: – High CRC or Alignment errors at full duplex end – Late collisions at half duplex end UAB sets all user ports to 10/half by default
  12. 12. Firewalls H.323 uses these IP ports: – Statically-assigned TCP ports 1718 – 1720 and 1731 for call setup and control. – Dynamically-assigned UDP ports in the range of 1024 – 65535 for video and audio data streams. Firewalls don’t allow unrestricted ports: typical modern firewalls and H.323 don’t get along so well.
  13. 13. Firewalls – Solutions for H.323• [bad; non-scaleable] Allow unrestricted ports for specific, known, external IP-addresses.• [better, but still not so good] Use feature of some videoconferencing clients to confine dynamic ports to a specific, narrow range.• [OK, but extra admin work and cost] Use an H.323 application proxy.• [best] Use a firewall that snoops on the H.323 call set-up channels (static ports) and opens ports for the audio/video (dynamic ports) as needed.
  14. 14. Network Issues Ongoing, undiagnosed problems with H.323 – Jerky video over uncongested networks; why? – Quality of H.320 vs. H.323 over uncongested networks – >.1% packet loss = unacceptable audio (ITU) – >.5% renders session unusable
  15. 15. H.323 Network Requirements: Latency  One-Way Delay: – [ 0 – 150 ms] : Excellent ! – [150 – 300 ms] : OK – [300 – 400 ms] : Bad – [400+ ms] : “Fuggedahboudit”
  16. 16. H.323 Network Requirements: Jitter  Definition: Variation in latency over time.  For switched end-points, the primary source of jitter is variation in the store-and-forward time, resulting from network load.  H.323 is very intolerant of jitter; clients reduce resolution  Rule of thumb?
  17. 17. H.323 Network Requirements: Packet Loss  Typically due to router or link congestion – >0.1% packet loss (ITU) = unacceptable audio – >0.5% renders session unusable
  18. 18. Tools for Diagnosing H.323 Problems Ping  GnuPlotPing TraceRoute  Sniffer PingPlot  ViDeNet Scout  QCheck MRTG  OARNet H.323 Iperf “Beacon”
  19. 19. Tools: ViDe.Net Scout Scout is a web-based distributed network performance analysis tool developed at the University of North Carolina at Chapel Hill. Scout makes use of the NetIQ Chariot performance testing engine http://scout.video.unc.edu/
  20. 20. Scouting Advanced Networks 10 minute 384kbs simulated conference SURFNet (Netherlands) CUDI (Mexico) THROUGHPUT PACKET LOSS JITTER
  21. 21. Scouting Out Problems Public Health Outreach Project THROUGHPUT Remote Health Clinic connected to Internet2 via xDSL Original diagnosis was h.323 problem ISP refused problem ownership until presented with Scout results PACKET LOSS
  22. 22. Iperf – Example on Intercampus DS3 http://dast.nlanr.net/Projects/Iperf/ MRTG utilization graph showed bandwidth peaking at capacity ~ 10:00am – 2:00pm As utilization peaked on the DS3, jitter measured by Iperf rose to unacceptable level Iperf also reported periodic high packet loss, with no apparent correlation to the low-resolution MRTG utilization reports
  23. 23. The End-to-End Problem Problem: Poor video and/or audio in a conference between campuses Need: Timely, useful assistance If there’s a firewall, it could take weeks!
  24. 24. Suggested Solutions Articulate the E-2-E problem to network management and engineers Bring all engineers together in a place and time to share information. Establish and use reliable communication tools Improve diagnostic tools Have good network documentation for all networks
  25. 25. Future ViDe.Net Direction: Middleware for Video Directories : key enabler of video teleconferencing. Directories : management tool for tracking and supporting users Directory : a portal for account requests, support, user information updates, etc. Goal: Directory lookup, authenticated click & dial
  26. 26. Middleware for Video: NSFNational Middleware Initiative NMI Release 1 due this Spring h323Identify and h323Zone object classes will enable h.323 attributes to be added to campus LDAP directories Coordination with Internet2 Middleware activities will create a globally searchable directory of video users Will allow automatic user account management by integration with enterprise directories
  27. 27. What is ViDe? (www.vide.net)
  28. 28. SURA/ViDe Digital VideoWorkshop April 23-25, 2002 4th Annual Workshop Birmingham, Alabama UAB Campus Digital Video Applications: collaborative conferencing, streaming video, and storing/serving video-on-demand Technical Training & Discussion Program/Technical/Vendor Advisory Committee – please volunteer.

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