see I've had very interesting debates on QOS. Having recently put up a +10G core, I found it hard to understand why QOS was such a big deal. We did do it, we have a very kickass QOS policy. It is even implemented and documented and alot of guys using our network mark packets appropriately.
While 'random surfing' today, turns out there's a weird phenomenon known as instantaneous buffer utilization/congestion.
This instantaneous buffer utilization can lead to a difference in delay times between packets in the same voice stream. This difference - jitter, is the variation between when a packet is expected to arrive and when it actually is received. To compensate for these delay variations between voice packets in a conversation, VoIP endpoints use jitter buffers to turn the delay variations into a constant value so that voice can be played out smoothly.
Hence the primary role of QoS in a network like ours is not to control latency or jitter but to manage packet loss. In 10GE campus networks, it takes only a few milliseconds of congestion to cause instantaneous buffer overruns resulting in packet drops. That single drop is what we take care of with QOS on a 10G core, its why we'll do it on the 40G core...it's why we'll keep doing QOS....I still suck abit at QOS....its just too nuanced for my attention span..
Monday, August 8, 2011
Subscribe to:
Post Comments (Atom)
No comments:
Post a Comment