Comments
snad.ncsl.nist.gov/proj/iptel/jain-sip-1.2/.../Request.html
Posted by saqlain231
It indicates the user or service to which this request is being addressed. Unlike the To field, the Request-URI MAY be re-written by proxies.
When used as a Request-URI, a SIP-URL MUST NOT contains the transport-param, maddr-param, ttl-param, or headers elements. A server that receives a SIP-URL with these elements removes them before further processing.
Typically, the UAC sets the Request-URI and To to the same SIP URL, presumed to remain unchanged over long time periods. However, if the UAC has cached a more direct path to the callee, e.g., from the Contact header field of a response to a previous request, the To would still contain the long-term, "public" address, while the Request-URI would be set to the cached address.
Proxy and redirect servers MAY use the information in the Request-URI and request header fields to handle the request and possibly rewrite the Request-URI. For example, a request addressed to the generic address sip:sales@acme.com is proxied to the particular person, e.g.,sip:bob@ny.acme.com , with the To field remaining as sip:sales@acme.com. At ny.acme.com , Bob then designates Alice as the temporary substitute.
The host part of the Request-URI typically agrees with one of the host names of the receiving server. If it does not, the server SHOULD proxy the request to the address indicated or return a 404 (Not Found) response if it is unwilling or unable to do so. For example, the Request-URI and server host name can disagree in the case of a firewall proxy that handles outgoing calls. This mode of operation is similar to that of HTTP proxies.
If a SIP server receives a request with a URI indicating a scheme other than SIP which that server does not understand, the server MUST return a 400 (Bad Request) response. It MUST do this even if the To header field contains a scheme it does understand. This is because proxies are responsible for processing the Request-URI; the To field is of end-to-end significance.
Posted by yogendra
A SIP request consists of a method token, a request URI, and the SIP version. A method token is used to identify the request. The request URI is the address of the device where the request is being sent.
Posted by sagitraz
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