SIP Delayed Media Update
The Oracle® Enterprise Session Border Controller supports SIP delayed media update. When enabled, this feature keeps the Oracle® Enterprise Session Border Controller from updating its media flow information for flows established after an offer-answer exchange. The Oracle® Enterprise Session Border Controller does not update the flow information until a new offer and answer arrive for a specific set of media flows.
The (subsequent) offer does not have to be for the same session; rather, it can appear as a new SIP INVITE that uses the same SDP.
Delayed Media Update Disabled
When this feature is disabled (which is the default behavior), the Oracle® Enterprise Session Border Controller updates media flow entries in its CAM based on signaled SDP when it processes the SDP. If it processes an SDP offer, Oracle® Enterprise Session Border Controller allocates steering port resources; the Oracle® Enterprise Session Border Controller updates any missing elements for the flow when the answer is returned.
In cases when a secondary offer arrives (either a reINVITE, an UPDATE, or the original INVITE is hairpinned back through the Oracle® Enterprise Session Border Controller), the Oracle® Enterprise Session Border Controller updates the following media flow information at the time of the offer
- Destination IP address
- Destination port
- Realm for the media flows
- Media release settings
This behavior affects specific applications that are better served by the Oracle® Enterprise Session Border Controller waiting to update media flow information until it receives the answer to the second offer.
Delayed Media Update Enabled
When you enable the SIP delayed media update feature, the Oracle® Enterprise Session Border Controller:
- Delays changing the active media flow CAM entry for a new offer if a previous offer and answer have been received for the same media flows; it encodes new SDP information in an outgoing offer, but does not change the CAM entry until the answer is received
- Delays changing the active media flow CAM entry even when the new offer is for a new session
- Supports media release when performing delayed media update changes
- Offers per-realm configuration
This section describes how the delayed media update feature works for hairpinned call flows and for an SDP offer arriving for installed flows.
- Hairpinned call flows—In this type of call flow, the application server (AS) sends an INVITE back to the
Oracle® Enterprise Session Border Controller and that INVITE needs to be forwarded to another user (user B). When it receives the offer in this INVITE and delayed media update is disabled, the
Oracle® Enterprise Session Border Controller determines that the call is hairpinned and deletes the CAM entry for the flow for user A, who has sent the initial INVITE. The
Oracle® Enterprise Session Border Controller deletes the CAM entry for the flow from the AS to user A.
With delayed media update enabled, the CAM entry for the flow from the AS to user A is not deleted. Instead, the Oracle® Enterprise Session Border Controller waits until it has an answer from user B, and then performs the necessary updates and deletions.
- SDP offer for installed media flows—With delayed media update enabled, if it has received an offer and answer and a new offer arrives for the same flow, the Oracle® Enterprise Session Border Controller delays updating the CAM entries until an answer is received for the new offer.