SDP
Short definition
SDP (Session Description Protocol) is a format for describing media-session parameters such as addresses, ports and supported codecs.
Meaning and how it works
SDP is commonly carried within SIP messages so endpoints can negotiate how audio or video will be exchanged. It describes media configuration but does not itself establish a call or transport voice packets. The session description can change during a call.
Business applications
- Business scenario:
Two IP phones exchange SDP offers and answers to select a compatible audio codec and RTP destination.
What to check before implementation
When audio is missing, inspect advertised IP addresses, ports, media directions and codec compatibility. A successful SIP exchange does not guarantee valid media negotiation.