The BIG-IP® system includes a services profile that you can use to manage Session Initiation Protocol (SIP) traffic. Session Initiation Protocol is an application-layer protocol that manages sessions consisting of multiple participants, thus enabling real-time messaging, voice, data, and video. A session can be a simple two-way telephone call or Instant Message dialogue, or a complex, collaborative, multi-media conference call that includes voice, data, and video.
SIP sessions, which are application level sessions, run through one of three Layer 4 protocols: SCTP, TCP, or UDP. The SIP profile configures how the system handles SIP sessions. The specified Layer 4 protocol profile configures the virtual server to open the required port to allow data to flow through the BIG-IP® system. When you assign a SIP profile to a virtual server, you can also assign an SCTP, TCP, or UDP profile to the server. If you do not assign one of these protocol profiles to the server, the BIG-IP system automatically assigns one for you.
The SIP profile automatically configures the BIG-IP system to handle persistence for SIP sessions using Call-ID. The Call-ID is a globally unique identifier that groups together a series of messages, which are sent between communicating applications. You can customize how the system handles persistence for SIP sessions.
The BIG-IP system accepts incoming SIP messages that are 65535 bytes or smaller. If a SIP message exceeds this value, the system drops the connection.
The BIG-IP system can snoop SIP dialog information and automatically forward SIP messages to the known SIP dialog. To forward these messages, you can specify a SIP proxy functional group.
You can specify the name of a proxy functional group. You use this setting in the case where you need multiple virtual servers, each referencing a SIP-type profile, and you want more than one of those profiles to belong to the same proxy functional group.
The BIG-IP system terminates a SIP connection when either the application that initiated the session (client) or the application that answered the initiated session (server) issues a BYE transaction. This is appropriate when a SIP session is running on UDP. However, if a SIP session is running on a SCTP or TCP connection, you can prevent the system from terminating the SIP connection.
An optional feature in a SIP profile is header insertion. You can specify whether the BIG-IP system inserts Via, Secure Via, and Record-Route headers into SIP requests. When you assign the configured SIP profile to a virtual server, the BIG-IP system then inserts the header specified in the profile into any SIP request that the BIG-IP system sends to a pool or pool member.
The SIP OneConnect™ feature allows connection flow reuse between inbound and outbound virtual servers for UDP connections. This feature addresses common SIP client behavior where source and destination ports are both 5060.
SIP OneConnect features a built-in dialog-aware behavior that addresses scenarios where the BIG-IP is the intermediary between more than two parties, creating an ambiguity between source and destination for the dialog. For example, in scenarios where an internal client initiates an outbound call using the wildcard virtual server to an external client that already has an existing flow on the inbound virtual server, the SIP OneConnect dialog-aware behavior correctly routes the response traffic.
To activate the SIP OneConnect feature, type identical community strings in both SIP profiles used for the two virtual servers responsible for inbound and outbound SIP connections.
To disable the SIP OneConnect dialog-aware behavior and re-enable the default dialog-aware behavior, check the Dialog Aware setting when both community strings are set.