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My concern is the buffers may be to small to handle that type of traffic in a sustained manner, say 20Mb of G711 traffic.
Ah, an excellent concern. However, for something like VoIP, you don't want to oversubscribe the available bandwidth, i.e. if you need to (excessively) buffer VoIP bearer packets, you likely don't have enough bandwidth.
That noted, since devices often implement queue limits based on packets/frame count, small frames/packets might exceed queue limits even through there is adequate buffer space. So, you might need to adjust logical queue limits.
Since G.711 is sort of CBR, you can push the link/interface to very high utilization, predicting average queue depth assuming a M/M/1 solution.
For example, let's assume our G.711 packets are 200 bytes, and we don't want to exceed 10 ms. Also assume we're using a gig link. First we calculate the number of packets that use 10 ms on a gig link, each 200 bytes. I calculate 6,250 such packets (or 1.25 MB). M/M/1 predicts 99.985 utilization would average 6,665 in the queue.
Also assuming about 87.2 Kbps per G.711 call, a gig would support about 11 thousand calls.
So, how many calls were you intending to pass across a gig interface? What's acceptable queuing delay?
