Purpose of a Transform in Expressway Server

Transform in Expressway Server

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Question

What is the purpose of a transform in the Expressway server?

Answers

A. A transform has the function as a neighbor zone in the Expressway. It creates a connection with another server.

B. A transform changes the audio codec when the call goes through the Expressway.

C. A transform is used to route calls to a destination.

D. A transform changes an alias that matches certain criteria into another alias.

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Explanations

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A. B. C. D.

In Cisco Expressway, a transform is a set of rules that allow manipulation of various SIP message parameters, including headers, SDP attributes, and aliases. The purpose of a transform is to enable interoperability between different types of systems, including those that have different addressing schemes, codecs, or network topologies.

Specifically, transforms are used to modify SIP messages as they pass through the Expressway, with the goal of adapting the messages to the requirements of the recipient system. Some examples of transforms include:

Changing the format of an alias to match the requirements of the destination system. For example, the Expressway may receive a SIP message that contains an alias in E.164 format, but the destination system requires a SIP URI format. A transform can be used to convert the E.164 format alias to the SIP URI format.
Modifying the audio codec used in a call to ensure compatibility between the endpoints. For example, the Expressway may receive a call that uses the G.711 codec, but the destination system only supports the G.729 codec. A transform can be used to modify the SDP parameters in the SIP message to indicate that the call should use the G.729 codec instead.
Manipulating the headers in a SIP message to enable routing of the call to the correct destination. For example, the Expressway may receive a call that is addressed to a specific endpoint on the internal network, but the destination system is unable to route the call based on that address. A transform can be used to modify the headers in the SIP message to include additional routing information that the destination system can use to route the call.

In summary, the purpose of a transform in the Expressway server is to enable interoperability between different systems by modifying SIP messages as they pass through the Expressway. Transforms can be used to manipulate various SIP message parameters, including headers, SDP attributes, and aliases, to ensure compatibility between different types of systems.

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