Columbia, MO Columns and Jesse Hall

Video Quality of Service (QoS)

Technical Bulletin, Feb. 19, 2004

Quality of Service (QoS) is determined by video queue size and IP precedence. To ensure bi-directional QoS, both MOREnet and its customers must enable IP precedence 5 on outbound video packets. MOREnet marks all outbound video traffic as it leaves the MCUs and requires customers to mark their packets as they leave their location.

For MOREnet to determine the correct bandwidth allocation for a videoconference, customers must let MOREnet know how many concurrent video sessions they will be running. Each video session requires 420 Kbps of bandwidth. Cisco recommends that no more than 75% of the total bandwidth be used by the video queue. Following this guideline, one T-1 line could carry a maximum of three video sessions. If the calls go through a MOREnet MCU, however, the additional overhead of MCU traffic will reduce the maximum number of available video sessions to two. Customers who have only part of a T-1 may only be able to run one video session at a time. In order to run more concurrent sessions, customers will have to upgrade their circuit.

Since the video queue determines the amount of video traffic that can pass unhindered, customers must notify MOREnet when adding codecs and/or sessions to their network. MOREnet will then adjust the video queue on the customer's connection to MOREnet. It is important to note that, even though all of the bandwidth is not being used, video drops may occur if the queue is not large enough.