[VoiceOps] Broadworks media server not playing well with early media

[Scott Berkman]

ALU Usually just mean Alcatel/Lucent, and they have a number of different
models of switches.

 

RFC 3398 (Integrated Services Digital Network (ISDN) User Part (ISUP) to
Session Initiation Protocol (SIP) Mapping) usually makes me think of
"SIP-T", and BroadSoft doesn't really speak SIP-T (or didn't when I last
looked into it) well enough to handle some of these situations.  I've also
seen issues with "NPDI" fields that come down to something similar.  More
importantly, I don't think BroadSoft normally benefits in any major way from
the extra information SIP-T provides.

 

So one thing to check with your ITSP is if they have the trunk built as SIP
or SIP-T (or whatever terminology goes with this in their switch).

 

If they can re-build your trunk as "plain" SIP, it should stop sending the
extra 18X's because it will no longer be trying to pass along the ISUP
information that BroadSoft is likely ignoring or improperly handling anyway.
If you have done any packet captures and see an ISUP body section below the
SDP body, this basically confirms they are doing SIP-T with you.

 

If the AS now has the means to support RFC3398 and you can't get the ITSP to
reconfigure or rebuild the trunk, changing that settings certainly may fix
your issue.  My concern about "testing" that on a production system is that
the AS may change its behavior in other scenarios where right now its
ignoring a value in the SIP-T encapsulated ISUP body, but once it starts
paying attention you could have any number of other issues instead or in
addition.

 

Hope that helps,

 

-Scott

 

From: voiceops-bounces at voiceops.org [mailto:voiceops-bounces at voiceops.org]
On Behalf Of John Myhre
Sent: Wednesday, April 25, 2012 12:56 PM
To: voiceops at voiceops.org
Subject: Re: [VoiceOps] Broadworks media server not playing well with early
media

 

There's a (ALU?) sip/isup gateway on the far side of the itsp I shipping the
call to.  The gateway's attempt to following rfc 3398, and is therefore
mapping isup cpgs to 18x messages.

 

I've gotten pointed to the supportRFC3398 setting under interface>sip on the
Broadworks AS.  Setting it to true is supposed to inhibit the AS from
attempting to transition the call back to local ring when it receives a 18x
message with no sdp, after receiving on with sdp.

 

That seems to match my issue.  I've got a maintenance window coming up and
will see if reality matches the theory.

 

/John

 

From: Scott Berkman [mailto:scott at sberkman.net] 
Sent: Tuesday, April 24, 2012 2:01 PM
To: 'John Myhre'; voiceops at voiceops.org
Subject: RE: [VoiceOps] Broadworks media server not playing well with early
media

 

What is on the network side?

 

I don't believe BroadSoft allows for multiple 18X responses, and in my
opinion no system should.  Once you have sent an offer, the only way to
modify it should be a RE-INVITE.  I believe the RFC's do technically allow
for this though, and in that case the newer 18X message will
override/replace the previous.

 

Another issue may be that 183 messages usually are accompanied with SDP,
where 180 message are used when no early media (and therefore no SDP) is to
be used.  So a second 183 with no SDP is all kinds of wrong to me.

 

Hope that helps,

 

-Scott

 

From: voiceops-bounces at voiceops.org [mailto:voiceops-bounces at voiceops.org]
On Behalf Of John Myhre
Sent: Monday, April 23, 2012 4:19 PM
To: voiceops at voiceops.org
Subject: [VoiceOps] Broadworks media server not playing well with early
media

 

I seem to be having a problem with Broadworks thinking an early media stream
has ended.

 

I'm sending a call out to the PSTN and receiving back a 183 with SDP
(presumably early media).  Broadworks is dutifully passing everything down
to the device.

 

I'm then receiving a second 183, this time with no SDP (presumably because
someone's gateway received a CPG).  In this case, Broadworks appears to
interpret the lack of SDP as meaning the early media has ended (not the
case) and plumbs the media server into the bearer path to play ringing.  

 

Anyone run into this problem?  Any ideas for a way around it?  

 

I've found a reference for dealing with this problem from the access side,
but not when the 183s are coming from the network side.

 

I'm running Broadworks Rel14sp4.

 

Many thanks for any ideas!

 

/John

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