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Session Initiation Protocol (SIP) is a signaling communications protocol, widely used for controlling multimedia communication sessions such as voice and video calls over Internet Protocol (IP) networks. The protocol defines the messages that are sent between peers and govern establishment, termination and other essential elements of a call. SIP can be used for creating, modifying and terminating two-party (unicast) or multiparty (multicast) sessions consisting of one or several media streams.

A SIP message consists of headers, each of which has a name (before the colon) and value (after the colon).  The value can consist other specific parts, such as tokens and parameters.

Example SIP message:

INVITE sip:4448451148@10.34.20.100:5060 SIP/2.0
Via: SIP/2.0/UDP 10.34.13.56:23012;branch=z9hG4bK0cB4182841436;maddr=10.34.20.80
Max-Forwards: 70
From: <sip:13032220008@10.34.13.56:23012>;tag=4182841436
To: <sip:4448451148@10.34.20.100:5060>
Call-ID: 4182841436@10.34.13.56
CSeq: 10 INVITE
Contact: <sip:13032220008@10.34.13.56:23012;transport=udp>
Content-Type: application/sdp
Content-Length: 153
Expires: 90
User-Agent: ST Simulation
Accept: application/sdp
Accept-Encoding: gzip
Accept-Language: da, en-gb;q=0.8, en;q=0.7
Alert-Info: <http://www.example.com/sounds/moo.wav>
Allow: INVITE, ACK, OPTIONS, CANCEL, BYE
server: East

SIP Message Manipulation (SMM) allows you to modify SIP messages as they are processed by the SBC in both inbound and outbound directions. SMM involves defining a set of criteria and actions in a SIP Adapter Profile against select SIP messages in order to modify their headers and/or parameters.

A SIP adaptor profile contains a set of rules for how a SIP message should be manipulated. Each SIP adaptor profile is attached to a trunk group (or zone), and assigned to act on incoming or outgoing SIP messages. When a message comes into or out of a trunk group that has a SIP adaptor profile assigned to it, the message is evaluated based on a set of criteria in the profile. If it meets those criteria, it is modified according to actions defined in the profile.

A SIP Adaptor Profile contains one or more rules. Each rule contains one or more criteria, for example:

  • Check if the message is a request message of the type Invite
  • Check if a header name “From” is present in the message.

Each rule contains one or more actions, for example:

  • Delete the “From” header.
  • Add a “To” header
  • Modify the message body.

Here’s a simple example, in plain English, of what a SMM rule might do:

Check all Request messages of the type Invite to see if they have “Supported” header with the value 100rel.  If so, delete the “Supported” header.

The SBC 5000 series provides a set of powerful mechanisms to manage the processing of SIP messages between ingress and egress SIP Trunk groups using the SIP Adaptor Profile. For example, in Figure 1 a SIP Adaptor Profile is configured on ingress and egress trunk groups to apply rules to messages sequentially as the messages traverse the route.

SIP Adaptor Profiles are SBC objects associated with ingress and egress SIP Trunk Groups and Zones. Each profile consists of a collection of rules. Each rule consists of a set of criteria and actions. When enabled, the rules are applied to each SIP message. If all the criteria for a rule match the message, then the actions associated with the rule are applied to the message. Up to 256 SIP adaptor profiles may be provisioned on each SBC server.

Figure : SBC SMM Mechanisms

For SMM provisioning details, see the following pages:


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