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Thursday, 27 September 2012

SIP- Early Offer , Delayed Offer , Eraly Media

Below is The basic Sip messages

In Early offer, SIP Send SDP in the invite , the other part will send the SDP in the ringing message
In delay offer , SIP send the SDP in the ok200 ,the answer will be send back in the ACK message
SDP: Session Description Protocol , this protocol will negotiate codecs , type , encryption ….
Why using Early offer : SIP provider use the early offer to force using their codecs
Don’t  confuse with Early Media
Early Media is the Media that will be sent before completely establishing the SIP session

In the figure above the ring-back tone is generated  on the remote side at step 4

In the figure above the ring-back is generated locally at step 2
To resume early offer and early media are two different things , we can have early media and early offer at the same time ,or to have one but not the second



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