Technical data

2 Brocade ServerIron ADX Advanced Server Load Balancing Guide
53-1003441-01
SIP overview
1
SIP packet flow
Figure 1 demonstrates the basic operation of SIP; location of an endpoint, signal of a desire to
communicate, negotiation of session parameters to establish the session, and tear-down of the
session after completion.
FIGURE 1 SIP packet flow
The example in Figure 1 shows packet exchange between two SIP clients, also known as User
Agent Clients (UACs). In the figure each message is labeled with the letter "F" and a number for
reference. The session established between the two end-clients is facilitated by the SIP proxy
server. User1 "calls" User2 using a SIP identity, a type of Uniform Resource Identifier (URI) called a
SIP URI. The SIP URI is similar to an e-mail address, typically containing a username and a host
name. In this case, it is sip:[e-mail], where brocade.com is the domain of User1's SIP
service provider.