Internet Communications Using SIP : Delivering VoIP and Multimedia Services With Session Initiation Protocol {2Nd Ed.}

sends a set of ENUM queries in step 7 to DNS to find the corresponding URI address, which is returned and used as sip:userb@100. ...

Session-Related Functions Most SIP functions involve setting up sessions or occur during an established session. Although some a ...

Media Negotiation Media negotiationis part of the INVITE/200/ACKsequence used to establish a SIP session between two endpoints. ...

Figure 6.3 Successful session establishment example using INVITE SDP was initially developed in the framework of the Internet mu ...

Table 6.4 SDP Offer Example with Line-by-Line Description LINE DESCRIPTION v=0 Version — Current version number of SDP ( 0 ) — n ...

tentatively called “SDPng” for Next Generation [13]. This new protocol will have more advanced media negotiation and description ...

In the example of Figure 6.4, a call is set up between two user agents using the media description sdp1, carried in the initial ...

Session Termination and Cancellation Session termination and cancellationare two separate operations in SIP but are often confus ...

A user agent receiving a CANCELreplies with a 200 OKif a final response has not yet been sent, or a 481 Transaction Unknown resp ...

Figure 6.6 Session cancellation example using CANCEL Call Control The SIP architecture is one of peer-to-peer communication and ...

Figure 6.7 Mid-call signaling example using INFO There are two ways of implementing third-party control. The first uses a contro ...

Figure 6.8 Call control example using REFER The resulting INVITEmessage (Message 8) would then have the following form: INVITE s ...

Preconditions For Call Setup SIP has extensions to require preconditions. Quality of service (QoS) can be supported in the netwo ...

have been met and that the user may now be alerted, and the 180 Ringing response sent. The call then continues as per normal. No ...

Figure 6.9 Preconditions of call setup using UPDATEand PRACK Nonsession-Related Functions Some SIP functions do not relate direc ...

Mobility The registration function of SIP is very similar to registration in cell phones. In a registration message, a user send ...

A user agent can be configured to automatically register upon initialization, at preset intervals, or whenever a new user signs ...

with the reverse result. In this way, SIP allows user preferences to be carried with a request message. For example, a SIP reque ...

between two user agents, a MESSAGErequest can be sent at any time. SIP sup- port for presence and instant messaging includes SIP ...

The subscription request has the following form: SUBSCRIBE sip:[email protected] SIP/2.0 Via: SIP/2.0/UDP 4.3.2.1;branch=z9hG4bK34 ...