[Sip-implementors] Definition of Call-ID

[Hemant Pandey]

Dear All,        To implement multimedia services in 3G network, I recently started studying RFC3261 for SIP protocol. Since i am new to SIP protocol, i have confusion about few terms used in RFC3261. 1. Call-ID   What exactly this Call-ID identifies?    In its definition in RFC3261, Call-ID acts as a unique identifier to group together a series of messages. So what does this group means?   2. What is target refresh requests? How these requests could be differentiated with other requests?   3. which RFC should be referred for latest SIP call flows examples?   i will be obliged if any one help to clear these points.   Regards   Hemant Pandey