CODEWITHSUNDEEP
sipvoipsdp
user2818782
user2818782

Reputation: 756

Can a SIP call's media address changed mid-call?

I am referring to the c value of an SDP header. enter image description here

Is it possible that the media stream address changes during a call? And it what scenarios?

Upvotes: 0

Views: 783

Answers (1)

TMSZ
TMSZ

Reputation: 687

It may be changed with re-INVITE or UPDATE. Some example scenarios:

  • PABX system consisting of multiple machines decides to route media through another media endpoint because of e.g. high server load or some other problem with this machine
  • after receiving FAX CNG, CED and/or modem preamble PABX passes the call to fax server
  • call is passed to specialized music-on-hold or IVR server

Also, addresses advertised in SIP headers or in SDP quite often are not matching real addresses used for communication because of NAT or misconfiguration - for best results B2BUAs often may ignore them.

Upvotes: 1

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