[cisco-voip] SCCP Delay Tolerance CallManager versions 4.2 and 6.x

[Peter Slow]

Tim,
  This does have the potential to affect your user experience. You
need to consider operations where messages require acknowledgement.
this even counts for tcp layer stuff. This will also affect your audio
delay. For instance audio setup delay

with h.322 where you've got 150 msec delay between:
Two endpoints using fast connect = minimum of 600 msec
Two endoints using normal h.245 messaging = > 1.2 seconds

This is being generous and not accouting for the fact that messages
need to be relayed to other endpoints after they are received as H.323
(for instance, info in an h.323 OLCAck needs to be passed via SCCP to
a phone as a startmediaTransmission msg,  that could potentially take
another 150 msec, these times don't account for that =)

This same sort of thing would mean a call between two people in the
same office you're talking about would take a mimimum of >.6 seconds
to establish audio in ideal coditions, starting from the point where
the called party goes off hook.

-Peter


On 6/26/08, Tim Smith <thsglobal at gmail.com> wrote:
> Hi Guys,
>
> Anyone have any idea on what is the maximum acceptable RTT for SCCP between
> phones and CallManager. And I guess also either H323 or MGCP.
>
> I'm aware of the the voice recommendations for 150ms one way for the actual
> media stream so I'm assuming SCCP is ok anywhere under this as well..
>
> I'm considering running a small office in New York off a cluster in Europe.
>
> I'm going to do some testing. But wondering what people have actually
> deployed, and if there are any problems.
>
> Cheers,
>
> Tim
>
>
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