Call

Call: A call consists of all participants in a conference invited by

a common source. A SIP call is identified by a globally unique

call-id (Section 6.12). Thus, if a user is, for example, invited

to the same multicast session by several people, each of these

invitations will be a unique call. A point-to-point Internet

telephony conversation maps into a single SIP call. In a

multiparty conference unit (MCU) based call-in conference, each

participant uses a separate call to invite himself to the MCU.