Overview
The Media Path settings determine the path taken by media after a call is established by CUBE.
Note |
H.323 protocol is no longer supported from Cisco IOS XE Bengaluru 17.6.1a onwards. Consider using SIP for multimedia applications. |
You can configure the media path in the following modes:
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Media flow-through: where media and signaling packets terminate and originate on CUBE. As CUBE is an active participant of the call, this mode is recommended when connected outside an enterprise (untrusted endpoints). -
Media flow-around: where signaling packets terminate and originate on CUBE, but media flows directly between endpoints. As media bypasses CUBE, this mode is recommended when connected within an enterprise (trusted endpoints).
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Media antitrombone: where CUBE is allowed to detect and avoid loops that are created by call transfers or call forwards. Loops are restricted to the SIP signaling path and removed from the RTP media path.
The user agent may initiate call forwards and call transfers that are sent towards CUBE as a new SIP INVITE dialog. CUBE considers the original call and the forwarded call as separate unrelated calls. Media antitromboning allows CUBE to detect the relation between the calls and resolve the media loop by sending SDP packets back to the sender.
The figure below illustrates how media is needlessly looped over the WAN when loops are not detected.
The figure below illustrates how CUBE detects and avoids the loop with the antitromboning feature.
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SDP Pass–Through: CUBE is configured to pass SDP information transparently, so that both the remote ends can negotiate media independently. SDP pass-through is addressed in two modes:
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Flow-through—CUBE plays no role in media negotiation, it terminates and reoriginates the RTP packets irrespective of the content type that is negotiated by both the ends. This supports address hiding and NAT traversal.
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Flow-around—CUBE neither plays a part in media negotiation, nor does it terminate and reoriginate media. Media negotiation and media exchange is end-to-end.
For more information, refer to the “Configurable Pass-through of SIP INVITE Parameters” section in the Cisco Unified Border Element SIP Support Configuration Guide .
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Restrictions for Media Anti-Tromboning
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Anti-Tromboning is possible for secure (SRTP) calls only when SDP passthrough is enabled.
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Anti-Tromboning is not possible if one call leg is media flow-through and the other call leg is Media Flow-Around. Similarly, antitromboning is not possible if one call leg is configured for Session Description Protocol (SDP) passthrough.
Feature Information
The following table provides release information about the feature or features described in this module. This table lists only the software release that introduced support for a given feature in a given software release train. Unless noted otherwise, subsequent releases of that software release train also support that feature.
Use Cisco Feature Navigator to find information about platform support and Cisco software image support. To access Cisco Feature Navigator, go to www.cisco.com/go/cfn. An account on Cisco.com is not required.
Feature Name |
Releases |
Feature Information |
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Configuring Media Path |
Baseline functionality |
The following commands were introduced by this feature: media-flow around, media flow-through, media anti-trombone . |