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. Internet2
 Commons


3. Desktop & Room Systems

• USB or Appliance
• Affordable
• User Friendly

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. H.323 Audio Standards
 G711 Audio Codec Required
 Optional Codecs: G721, G723, G728,
G729
 Bottom Line – Good Audio Requires
64Kb

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. 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. 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. 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. 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. 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. 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. 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. 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. H.323 Network Requirements:
Latency
 One-Way Delay:
– [ 0 – 150 ms] : Excellent !
– [150 – 300 ms] : OK
– [300 – 400 ms] : Bad
– [400+ ms] : “Fuggedahboudit”

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. 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. Tools for Diagnosing
H.323 Problems
 Ping  GnuPlotPing
 TraceRoute  Sniffer
 PingPlot  ViDeNet Scout
 QCheck
 MRTG
 OARNet H.323
 Iperf “Beacon”

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. Scouting Advanced Networks
10 minute 384kbs simulated conference
SURFNet (Netherlands) CUDI (Mexico)
THROUGHPUT
PACKET LOSS
JITTER

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. 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. 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. 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. 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. Middleware for Video: NSF
National 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. What is ViDe? (www.vide.net)

28. SURA/ViDe Digital Video
Workshop 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.