Hello,
I have a
conference bridge (Avaya S6200 on SCO Unix) which I'm getting intermittent
reports of 'garbled' audio. The conf bridge uses G.711 u- or a-law, and incoming
audio is provided by an ITSP (who have media gateways (I believe Cisco)
installed in a variety of locations that connect to PSTN).
I've also
got a PSTN connection into the bridge, where there are no reports of poor audio,
so I suspect something on the network (ie this is only effecting calls that come
in via SIP/VoIP).
I have
the following connectivity:
Unix
conference bridge <-> Cisco 2960 switch <-> Juniper SSG5 firewall
<-> datacenter's BGP <-> public internet <-> ITSP's
own POP <-> ITSP's own network <-> local media gateway in local
carrier datacenter
I can't
install Wireshark on the SCO Unix bridge (old 7.1.1 version of OS), so I've got
Wireshark running on a Windows server connected to a Port mirror (or port
span) so it's taking a copy of all the traffic going to the Unix conference
bridge. I also know that Wireshark can't know the state of the various
points on the network, so I'm only posting info on the end-point (ie at the conf
bridge)
I'm also
open to any general suggestions that anyone has, but I know this is a Wireshark
maillist, so what I'm specifically trying to find out about Wireshark (bless
it!) is:
I've used
the Statistics -> RTP -> Show all streams to get a view of the various RTP
streams of reported bad audio. I've a vague idea of the principles behind
calculating jitter, but when I see an 'X' in the 'Pb?' column is this definitely
a problem or just a suggestion that it might be an issue? The following are the
values for one sample call with reported bad audio:
Column - forward value [reverse value]
Lost - 0
(0.0%) [47 (0.0%)]
Max Delta
(ms) - 4119.77 [320.14]
Max
Jitter (ms) - 1.80 [70.12]
Mean
Jitter (ms) - 0.02 [0.30]
Pb? -
blank [X]
The above
is from a sample of about 60 minutes, so is a good
representation.
So which
of the above values (if any) should I be worried about (ie would affect audio
quality)?
Any
information/suggestions/comments appreciated.
Regards,
gdo
