Library items tagged: H.323

Anonymous
References CISCO, 2001. Deploying QoS for Voice and Video in IP Networks. Cisco® Networkers 2001 Conference presentation VVT-213. Cisco®. CISCO, 2003a. How LAN Switches Work. [WWW 6 February 2004] http://www.cisco.com/warp/public/473/lan-switch-cisco.pdf
Anonymous
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:
Anonymous
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.
Anonymous
This section examines the role of physical separation in the provision of reliable and secure links for real-time traffic. In many cases equipment can be directly connected together without being also plugged into the campus LAN directly. This can be especially beneficial when equipment is dedicated to a task – such as videoconferencing equipment – that operates stand-alone, i.e. is not part of a desktop PC used for normal network access/applications.
Anonymous
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.
Anonymous
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.
Anonymous
Anonymous
An Introduction to H.323 Videoconferencing, June 2002, D. E. Price and A.J. Spence Security Guide for H.323 Videoconferencing, Jan 2004, Tim Chown and Ben Juby
Anonymous
NAT should be familiar to network managers – it is widely deployed in large private networks. NAT is described fully in RFC1918 “Address Allocation for Private Internets”. NAT was introduced partly as a means of conserving real or public (also sometimes called 'routable') IP addresses. The deployment of NAT allows large organisations to give every computer a unique Internet address without diminishing the available pool of public IP addresses.
Anonymous
A simple firewall uses rules based on virtual 'ports' and IP addresses to filter traffic. Most Internet applications and services have well known ports on which machines 'listen' for communications (as standardised by the Internet Assigned Numbers Authority (IANA)). Firewalls will generally be configured to block anything by default but then allow traffic to flow through certain ports, either to and from any IP address or to a subset of IP addresses.