About Session Description Protocol Transparency Profile Setup
The Session Description Protocol (SDP) Transparency Profile can be configured to selectively allow declarative parameters or to allow all unrecognized parameters to pass from the ingress call leg to the egress call leg.
Session Description Protocol Transparency for Declarative Parameters
The Session Description Protocol Transparency for Declarative Parameters allows the administrator to specify declarative SDP attributes that are not natively supported by Cisco Unified Communications Manager (Unified Communications Manager) to be passed from the ingress call leg to the egress call leg. If the Unified Communications Manager receives attributes that are not explicitly identified by the administrator to send to the egress leg, Unified Communications Manager drops the attribute from the outgoing SDP similar to previous versions of Unified Communications Manager. This feature allows the administrator to identify attributes that are sent to the egress leg in multiple ways, such as configuring all property attributes with a particular name, all value attributes with a particular name, or all value attributes with a specific name and specific value to be passed through. The administrator can also configure all unrecognized attributes to be passed along in the outgoing SDP.
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SDP Transparency for Declarative Parameters only applies to declarative attributes, not to negotiated attributes. |
The Cisco Unified Communications Manager first looks at the name field of an incoming attribute. If the default "Pass all unknown SDP attributes" profile is not used, Unified Communications Manager looks for an exact match among the attributes designated to be passed through. An exact match between the name field of the attribute arriving on the ingress call leg and the name defined by the administrator occurs only if the two strings are identical (case sensitive). If an exact match is not found, then the attribute is not passed through.
The following are the three attributes that can be configured:
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Property attributes: When an administrator configures a property attribute in the SDP Transparency Profile, the attribute is passed through unless the incoming attribute has a value. If the incoming attribute has a value, Unified Communications Manager categorizes the incoming attribute as a value attribute and it is not passed through.
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Value attributes: When an administrator configures a value attribute of any value in the SDP Transparency Profile to be passed through, the attribute is passed through if it contains a value that includes at least one non-white space character (horizontal tab or space). If the value payload consists of all white space characters, Unified Communications Manager categorizes it as a value attribute and it is not passed through.
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Value attributes configured for value from list: The attribute is passed through only if the value matches one of the five specified values identified by the administrator. If the value does not match one of the five specified values or the there is no value, then the attribute is not passed through.
Session Description Protocol Transparency for All Unrecognized Attributes
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Standard SIP Profile for Cisco VCS
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Standard SIP Profile for Telepresence Conferencing
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Standard SIP Profile for Telepresence Endpoints
Limitations
This feature does not support attribute names longer than 64 characters.
Errors can also result from non-standard attribute formatting. It is recommended that devices passing SDP to the Unified Communications Manager in the ingress leg conform to RFC 4566 which define attribute syntax as:
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a=<name> for property attributes
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a=<name>:<value> for value attributes
Exceptions
Unknown attributes are not passed through if:
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One or more of Media Termination Point (MTP), Transcoder (Xcoder), RSVP, and/or Trusted Relay Point (TRP) that does not support pass through are allocated.
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Media Termination Point Required is selected.
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The ingress call leg is using Delayed Offer and the egress call leg is using Early Offer.
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Attributes belonging to a media line that is rejected in the process of negotiating media (the port is set to 0) are not passed through.