Sorry dudes...been out for the holidays. Back and cranking on the ONT. Passed the ISCW a while back with a decent score, but really want to kill this one to complete the CCNP. Here we go...
Default Cisco Voice sample size is 20ms
***Large sample sizes cause more coding delay, and result in greater, more noticeable ruined audio if the packet is lost or dropped.
http://www.voip-calculator.com/calculator -- a good voip calculator
Total packet size/payload size = total bandwidth requirement/total codec requirement
so to get total bandwidth requirement take:
total packet size * codec requirement / payload size = total bandwidth required
so for G.729 on a frame relay take this:
(6 (for frame header)+40 (l3 and l4)+ 20 (payload size for g.729) * 8kbps (codec req.)
20 (payload size for g.729)
= 26.4 kbps(multiply by total number of calls you expect at 1 time)
VAD- Voice activity detection is a mechanism that stops sending traffic during periods of silence
Thats a start. Also watched the VOIP design considerations video. Contained tidbits about call managers, phones, voip design models, and call admission controls.