Classify RTP Traffic

Interactive Realtime Transport Protocol (RTP) traffic can be further classified by media type, encoding name, or clock rate. For example, you can differentiate between different audio and video streams. Or, you could set the encoding name to a value such as G729, PCMA, GSM, or JPEG so that you can manage streams differently based on how they are encoded.

RTP also includes criteria for SIP-based RTP traffic so that you can classify by caller, callee, user-agent, source IP address of the call setup (SIP) flow, or destination IP address of the flow. For example, suppose all VoIP calls go through a SIP Gateway as shown in the diagram below:

Host1 ------- SIP Gateway1 ----------------- SIP Gateway2 ------- Host2

If you want to classify all VoIP traffic going through a specific SIP Gateway, you can create an RTP class with criteria that identifies the source or destination IP address of the SIP Gateway.

To create classes based on an RTP attribute, you must specify RTP-I as the service type.

Note: To perform this task from PolicyCenter, you must first select a configuration from the Editing Configuration drop-down list at the top of the page.

To classify interactive RTP traffic:

1. Click the manage tab.

2. In the left window pane, select the class or folder that will be the parent of the class you are about to define.

3. Click class and select add.

4. In the Name field, type a descriptive name (up to 31 characters; hyphens, underscores, and periods are acceptable).

5. For the Service, select RTP-I.

6. Scroll down to the Criterion field, and select the desired criterion from the drop-down list and then enter a text string in the empty text field. For example, to create a class for a specific VoIP caller, select SIP Caller Identifier in the Criterion field and then type the identifier (such as agb@bell-telephone.com) in the text field.

Note: For SIP attributes, you can enter a substring of the attribute. For example, to match all Motorola models, you can enter Motorola for the SIP User-Agent criteria.

8. Click add class.

For more information about the other entries in the New Traffic Class window, see Matching Rules.

Note: A matching rule can contain only one application-specific criterion. To combine multiple criteria, use two traffic classes, a parent and a child.