Patton electronic SmartNode 4110 Series manual Routing Architecture

SmartWare Software Configuration Guide 46 • Context SIP gateway overview

Introduction

This chapter provides an overview of the context SIP gateway. The main purpose of a context SIP gateway is forwarding and reception of SIP packets according to a RFC 3261 User Agent. In SmartWare, the context SIP gateway represents the interface between the Call-Router (Context CS) and the IP Router (Context IP). It is responsible for dispatching incoming initial SIP requests to the right call control SIP interface and for the determination of the right IP interface for outgoing SIP messages. This is also called SIP Transport Routing. Figure 78 shows where the context SIP gateway is located in SmartWare and how it interacts with other com- ponents.

Context

Call Routing CS

Tables

Call Routing

Context CS Interfaces

	Context
Location Services	SIP
	Gateway

Transport Routing

Context SIP - Gateway Interfaces

Network Routing

Context IP Interfaces

Context

IP Routing IP

Tables

Figure 78. Routing Architecture

There is a relationship between the call control SIP interface and the context SIP gateway. Every call control SIP interface must be bound to a context SIP gateway. One of the responsibilities of this interface is to build Request-URI and to determine a possible outbound proxy. If a proxy is available, it represents the next SIP hop and all outgoing messages will be sent to this host. If no proxy has been configured, the messages will be sent to the Request-URI's host. Depending on these two SIP parameters, the context SIP gateway chooses the right outgoing IP interface. The IP address of the outgoing IP interface will be placed in all SIP and SDP headers that need a direct routable contact address (VIA, Contact).

In the other direction, the context SIP gateway dispatches incoming SIP requests according to the Request- URI and the From-URI. The call control SIP interface has configuration parameters called “remote” and “local” to build the Request-URI, the To-URI and the From-URI for outgoing requests. These parameters will also used for identifying the best matching call control SIP interface for incoming requests according to the fol- lowing rule:

Introduction 560