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What are Most Important QoS Design Principles for ShoreTel

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What are Most Important QoS Design Principles for ShoreTel

Postby chicagotech » Wed May 10, 2017 2:34 pm

Q: We are planning to use ShoreTel VoIP service. What are the Most Important QoS Design Principles for ShoreTel?

A: Quoted
1. Critical applications such as VoIP require service guarantees regardless of network conditions. The only way
to provide service guarantees is to enable QoS queuing at any node that has the potential for congestion,
regardless of how rarely this may occur.
2. If you assign too much traffic for strict priority queuing (i.e. EF), beyond voice RTP traffic, then the overall
effect is a dampening of QoS functionality.
3. Voice media is time-sensitive and voice signalling is drop-sensitive. Due to different sensitivities, map EF
voice media to the strict priority queue, exlusively, and AF31/CS3 signalling to a medium priority queue.
Never map VoIP media and VoIP signaling together in the same queue.
4. Allow VoIP endpoints to self-mark QoS values for VoIP traffic and trust throughout the network. Only
remark if VoIP traffic is from an untrusted source.
5. RTP traffic should always be marked as EF, designated signaling traffic should be marked as CS3, and all
other traffic should not be marked, also called default traffic, while each is mapped to separate queues at
each interface via QoS.
6. With QoS disabled, all traffic goes through one queue to egress an interface so prioritization cannot occur.
With QoS enabled, multiple queues with separate, reserved packet buffer memory are activated for
prioritized classes of traffic to pass thru the interface before non-prioritized traffic.
7. If VoIP traffic passes any single interface without QoS configured, the effects of quality issues are felt on a
call as if no QoS is configured anywhere along the path.
8. Congested packet buffer memory is most often the QoS bottleneck rather than a congested link.
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