Polycom V2IU 4350 user manual Classifying, Upstream Traffic Management

User Manual V2IU 4350 Converged Network Appliance

applied to traffic in both the upstream (LAN to WAN) and downstream (WAN to LAN) direction. Each direction is independent of the other and can support different size priority queues.

Classifying

High priority voice and video traffic generated by endpoint devices is automatically identified by the V2IU’s VoIP Application Layer Gateway. Other VoIP devices (not making use of the ALG) can be defined as high-priority by their IP address. The user configures these addresses into the priority list in the Traffic Shaper section of the 4350 web GUI.

As the 4350 processes packets they are identified as either high or low priority based on this configuration. Packets identified as high priority are marked as such in the TOS bits of their IP header, allowing prioritization by downstream routers. The TOS field is set to 12 hexadecimal “minimize delay and maximize throughput.” This value overwrites any prior value.

Upstream Traffic Management

The 4350 appliance uses a combination of Class Based Queuing and simple classless queuing to send data in the upstream direction. The Class Based Queue (CBQ) consists of two priority classes (high and low), a scheduler to decide when packets need to be sent, and a traffic shaper to rate-limit by delaying packets before they are sent. Each of these is described in more detail below.

Priority classes

Voice and video traffic is placed in the high-priority queue and data traffic is placed in the low-priority queue. The IP header TOS field of packets in the high-priority queue is set to “minimize delay and maximize throughput”.

Scheduler

High-priority data is polled before low priority data, thereby minimizing the latency for voice and video traffic. High-priority data is allowed to use up to 85% of the total WAN bandwidth. Although preferential treatment is given to high-priority data, 15% of the WAN link is always reserved so that low-priority data is not starved.

High priority data is polled before lower priority data to reduce overall latency for voice traffic.

Traffic shaper

To smooth bursts from high speed data links (typically from the LAN Ethernet heading to the WAN) the 4350 appliance uses a buffer that clocks data out at rates not exceeding automatically-calculated maximums. Low-priority data is

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