[Kamailio-Users] Translate "486 Busy Here" to "600 Busy Everwhere"

Alex Balashov abalashov at evaristesys.com
Tue Nov 10 18:27:55 CET 2009

Geoffrey Mina wrote:

> CallID: 604627041_120490736 at
> Level3 --> INVITE --> Kamailio --> Asterisk
> Asterisk --> 183 Progress --> Kamailio --> Level3
> Asterisk --> 486 Busy --> Kamailio --> Level3
> Level3 --> ACK --> Kamailio --> Asterisk

I can't explain the presentation of a new and different Caller ID; 
that's bizarre.

As far as failing over on response codes that really, logically should 
not be failed on, well, that's a fairly standard bit of idiocy on the 
part of virtually all the Tier 1s and/or nationwide CLECs and/or big 
origination carriers.  Their gear is just configured to roll over on any 
4xx/5xx class errors.

I'll tell you what my solution is to this problem:

Since many of these origination providers don't properly map SIP replies 
to ISUP in ways that result in correspondingly meaningful messages being 
played to callers by originating switches[1], I take matters into my own 
hands - at the risk of burning up some trunks.  I have my customers run 
SEMS (media server) with their own recordings of busy signals and other 
messages they want played and have the proxy serially fork/branch to it 
when such a media rsource is needed, e.g.


    $rU = "busy";
    $rd = "mediaserver.ip";


Perhaps you should investigate that as a solution to your problem;  if 
the callee is busy, "trap" the initial call leg and send it to your own 
feature box.

Of course, this can burn up trunks in perpetuity if the caller doesn't 
hang up.  It is also quite undesirable if you're paying usage on inbound.

-- Alex

[1] One big Level3 reseller - it rhymes with candbidth.zom - reacts to 
all negative SIP replies with the propogation of a "this number is out 
of service" reply on the ISUP layer regardless of what the SIP reply 
code actually was, including 486 Busy!

Alex Balashov - Principal
Evariste Systems
Web     : http://www.evaristesys.com/
Tel     : (+1) (678) 954-0670
Direct  : (+1) (678) 954-0671

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