URI
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... Clients send SIP requests to the host part of a URI and servers send
responses to the host in the sent-by parameter of the Via header
field ...
...
We define two parameters, one for SIP URIs and the other for the Via
header field. The format of both parameters is the same, as shown in
...
...
The presence of this parameter (comp=sigcomp) in a URI indicates that
the request has to be compressed using SigComp, as defined in [2 ...
... sigcomp indicates that the SIP entity
identified by the URI or by the Via header field supports SigComp and
...
... URI, referred to
as the next-hop URI, is the Request-URI of the request or an entry in
the Route ...
... as the next-hop URI, is the Request-URI of the request or an entry in
the Route header field ...
...
If the next-hop URI is a SIPS URI, the request SHOULD be compressed
before it is passed to the TLS ...
... If the next-hop URI is a SIPS URI, the request SHOULD be compressed
before it is passed to the TLS layer ...
... client SHOULD add
the parameter comp=sigcomp to the URI in the Contact header field if
it is a user agent client ...
... proxy, it SHOULD add
the parameter comp=sigcomp to its URI in the Record-Route header
field.
...
... user agent client sends a compressed request, it SHOULD add the
parameter comp=sigcomp to the URI in the Contact header field. If a
proxy ...
... proxy that Record-Routes sends a compressed request, it SHOULD add
comp=sigcomp to its URI in the Record-Route header field.
...
...
For requests within a dialog, a next-hop URI with the comp=sigcomp
parameter is obtained from a Record ...
... client sending a request outside a dialog
can also obtain SIP URIs with comp=sigcomp in a Contact header field
...
... clients
need a means to obtain a comp=sigcomp URI from their outbound proxy
before the user decides to establish a session ...
...
client with URI parameters. In this case, the client SHOULD send an
uncompressed OPTIONS request to its outbound proxy ...
... uncompressed OPTIONS request to its outbound proxy. The outbound
proxy can provide an alternative SIP URI with the comp=sigcomp
parameter in a Contact header field ...
... header field in a 200 OK response to the
OPTIONS. The client can use this URI for subsequent requests that
are sent through the same outbound proxy using compression ...
... We extend this behavior to proxy servers responding to OPTIONS
addressed to them. They MAY list a set of alternative URIs to
contact the proxy.
...
... compressed is not a problem, since user agents can REGISTER a SIP URI
with comp=sigcomp in their registrar. All incoming requests for the
...
... with comp=sigcomp in their registrar. All incoming requests for the
user will be sent to this SIP URI using compression.
...
... Contact header field in the request that triggered this response (see
example in Section 9). It looks for the URI of the next upstream
(closer to the user agent client ...
... (closer to the user agent client) hop in the route set. If this URI
contains the parameter comp=sigcomp, the proxy ...
... sigcomp to its entry in the Record-Route header field. If this
URI does not contain the parameter comp=sigcomp, the proxy SHOULD
...
... sigcomp to the
Contact header field of the response if the URI of the next upstream
hop in the route ...
... network, the
proxy MAY choose not to compress the request even if the URI contains
the comp=sigcomp parameter.
...
... call flow below. Only some parts of each message are shown, namely
the Method name, the Request-URI and the Via, Route, Record-Route and
...