network based videoconferencing steve williams. why don’t people use ilt / ict not relevant not...
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Network based Videoconferencing
Steve Williams
Why don’t people use ILT / ICT
•Not relevant•Not easy to use•Not integrated•Not reliable •Not effective
• £5.5million project with £2.1m European funding
• European open procurement• Rollout and procurement group membership
– Technical– Non technical– HE and FE representatives
• Focus on– Ease of use– Suitability for use in a teaching environment– Appropriate use of effective technology
• 3 x 29” monitors, 2 x cameras + document camera
• High quality audio and video• Interactive whiteboard / Large video screen• Dedicated ‘data PC’ for application sharing
– We do not use data sharing facilities in VC equipment
• Laptop connection• Up to 4Mbps connection speed
The Beginning…
You have diverse groups of users on diverse network connected machines wanting to do
different things at different times and they all want the network to respond in an
appropriate manner.
If you do not have an adequately ‘overprovisioned’ network…
…the network must be able to differentiate between real-time critical and non-real time
services.
Real-Time critical traffic
Video ConferencingIP Telephony
Video Streaming
Web browsingMLE/VLE
Network Applications
WWWE-mail
MLE/VLE
VideoconferencingIP Telephony
Streamed Video
WWWE-mail
MLE/VLE
VideoconferencingIP Telephony
Streamed Video
An overprovisioned network is one where the traffic is able to flow freely from any point on
the network to any other point without suffering from delays by being queued.
If your network has bottlenecks or ‘low’ speed links and you want to run
videoconferencing you must consider providing some guarantee of service to
certain types of traffic…
…or it will not be reliable.
Differentiated Services
•Ability to provide Quality of Service based on classes or types of traffic•Expedited forwarding (EF-PHB)
•Real-time critical traffic•Low-loss, low jitter, fastest throughput up to limit•E.g. 1Mbps continuous throughput
•Videoconferencing and voice traffic•Assured Forwarding (AF-PHB)
•‘Guaranteed’ bandwidth over time x•E.g. 1Mbps averaged over 10 seconds
•Video Streaming
Network Metrics for Videoconferencing
•Available bandwidth•Enough! – actually enough x 1.5 minimum
•Availability•Should never be < 99.95% (22 minutes/month)
•SLA should state measured per rolling month max
•Packet Loss •<0.25% absolute max
•Inter Packet Delay Variation (IPDV or Jitter)• +- 30ms
•Round Trip Time (RTT) or One Way Delay(OWD)
•<100ms (50ms)
• Three normal classes + an option– EF (Voice and Video)– AF (Video Streaming and network updates)– BE (Best Effort – everything else)– LBE (Less than BE – throw away first)
Providing Guaranteed Service
EF – 20% of linkAF - 15% of link
BE - remainder
Think about
•The whole network path and the equipment in that path
•The type of traffic on each link•The worst link in the chain•Providing Quality of service•Engineering connections
WVN Switch WVN Gatekeeper/proxy
WVN Studio
WVN StudioWVN Studio
MAN Access Router
4 ports
SWMAN / NWMAN
MAN QoS
WVN QoS
H.323 only
Campus QoSVLAN & queuing
Campus core switch/routerRemote Campus
switch/router
Firewall
Institution Network Topology
• WVN is hybrid ISDN & IP solution
• ISDN = circuit switched– Call setup, dedicated
bandwidth• Just like a telephone
call
• IP = packet switched– Call setup,
contended bandwith• More like a very fast
postal service
