Library items tagged:

Academic Networks Janet Development Programme – includes work on QoS, Multicast, IPv6 etc. http://www.ja.net/development/ The JANET VTAS (Video Technology Advisory Service) provides advice to the UK education community through publications and their web site: http://www.video.ja.net/
CISCO, 2001. Deploying QoS for Voice and Video in IP Networks. Cisco® Networkers 2001Conference presentation VVT-213. Cisco®CISCO, 2003a. How LAN Switches Work. [WWW 6 February 2004] http://www.cisco.com/warp/public/473/lan-switch-cisco.pdfCISCO, 2003b. Understanding and Configuring the Unidirection Link Detection Protocol Feature. [WWW 6 February 2004] http://www.cisco.com/warp/public/473/77.pdf
The UWA (University of Wales, Aberystwyth) gatekeeper currently has seven H.323 videoconferencing endpoints in its zone. These consist of: four UWA WVN PictureTel 970 CODECs (each with a potential bandwidth of up to 2Mbit/s). two Leadtek BVP 8770 H.323 videophones. These have a maximum bandwidth of 640kbit/s. a Tandberg® 8000, with a maximum bandwidth of 768kbit/s. These are distributed around the University as follows:
Local area networks of any significant size, which almost certainly encompasses all those at educational organisations, are complex and unpredictable systems. The traffic flows produced within these networks, and the interactions between different flows within network components such as switches, are highly complex. Classifying, policing and priority queuing allow the network administrator some control over how these flows transit the network, and – crucially for voice and video traffic – allow time-critical traffic to have priority over other, less time-sensitive traffic.
In many cases, it will not be possible to physically separate H.323 and campus network traffic, and it will be necessary for all traffic to share the same physical links. In this case there are some methods that can be used to provide some level of protection to H.323 traffic, above that provided to the campus traffic.
This section examines the role of physical separation in the provision of reliable and secure links for real-time traffic.
Layer 1 - The Physical Layer Most modern campuses have installed switched networks but there remain sections of some networks that have hubs or co-axial cabling with repeaters. Because these networks are built on protocols that accept collisions, and hence congestion, as a normal part of network life, their traffic forwarding algorithms will back off from sending frames in the face of congestion.
This chapter aims to describe in some detail the demands that videoconferencing traffic places on the network, along with the metrics that can be used to predict – to a certain extent – the behaviour of a videoconference. Readers who may be less interested in the specifics of ‘Why is this important?’, and would like to move swiftly on to ‘What should I look at and do?’ are welcome to skip this section completely and move along to chapter 3.
This guide is aimed at network engineers and technicians, primarily in educational organisations, who need to provide a network capable of handling videoconferencing traffic.
This checklist is intended as a guide for site administrators. It may not be an exhaustive list of issues (this will vary depending on the site security policy, for example), but should be of assistance as a starting point.