Desktop & Room Systems • USB or Appliance • Affordable • User Friendly
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
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)
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
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.
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)
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
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
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.
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.
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
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?
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
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/
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
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
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!
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
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
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
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.