HP-UX C SIP Stack Programmer's Guide (Novembery 2007)

SIP Stack 17
SIP Stack Architecture
SIP STACK
A
RCHITECTURE
The SIP Stack consists of five main layers. The Stack Manager, User Agent,
Transaction Layer and Message Layer each export a dedicated API. Figure 2-2
shows the relationship between the various layers under the application.
Figure 2-2 SIP Stack Architecture
STACK MANAGER
LAYER
The Stack Manager layer sets the system configuration, memory allocation,
logging, and other resources. The Stack Manager is also responsible for the
initialization and shutdown of all other layers.
USER AGENT LAYER The User Agent layer creates and manages call-leg, subscription and register-
clients. The User Agent layer also maps incoming transactions to call-leg and
register-client objects.
Note The User Agent layer can be used for both client and server applications.
Stack
Manager
Layer
Call-Leg API
Register-Client API
Authenticator API
Subscription API
Transaction API
Application
Message
API
Message
Layer
Transport
API
Transport
Layer
User Agent Layer
Transaction Layer
Stack
Manager
API