Media Description - Can values be used for routing purposes?

[Tata]

! in the front of the regex value expresses "NOT".

"RTP/AVP.* 0" means "if there is 0" because the value doesn't have !.
"! RTP/AVP.* 0" means "if there is no 0" because the value has !.

Since 0 is G711U's payload type, the "! RTP/AVP.* 0" means "if the caller does NOT support G711U".



> $body("(m = audio .+)") = !RTP/AVP.* 0 0
> Even that 503's!!! What the heck!?

Because there is not "0 0" in m=audio line.


> $body("(m = audio .+)") = !RTP/AVP.* 0
> Call still comes in.

Because there is " 0 " in m=audio line.



> Media Attribute (a): rtpmap:101 telephone-event/8000

It is for telephone-events such as DTMF. It is not a codec.