SigComp
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... Via: SIP/2.0/UDP server1.foo.com:5060;branch=z9hG4bK87a7;comp=sigcomp
The presence of this parameter (comp=sigcomp ...
... sigcomp
The presence of this parameter (comp=sigcomp) in a URI indicates that
the request has to be compressed using SigComp ...
... sigcomp) in a URI indicates that
the request has to be compressed using SigComp, as defined in [2].
The presence of comp=sigcomp ...
... SigComp, as defined in [2].
The presence of comp=sigcomp in a Via header field indicates that the
response has to be compressed using SigComp ...
... sigcomp in a Via header field indicates that the
response has to be compressed using SigComp.
Therefore, the presence of comp=sigcomp ...
... SigComp.
Therefore, the presence of comp=sigcomp indicates that the SIP entity
identified by the URI ...
... identified by the URI or by the Via header field supports SigComp and
is willing to receive compressed messages. Having comp=sigcomp mean
...
... header field supports SigComp and
is willing to receive compressed messages. Having comp=sigcomp mean
"willingness" as well as "support" allows the receiver of a SIP
message ...
... "willingness" as well as "support" allows the receiver of a SIP
message to influence the decision of whether or not to use SigComp at
a given time.
...
...
Every SIP implementation that supports SigComp MUST implement the
procedures described in this document.
...
... If the next-hop URI contains the parameter comp=sigcomp, the client
SHOULD compress the request using SigComp ...
... A client MUST NOT send a compressed request to a server if it does
not know whether or not the server supports SigComp.
Regardless of whether the request is sent compressed or not, if a
...
... UAC direction compressed, this client SHOULD add
the parameter comp=sigcomp to the URI in the Contact header field if
...
... client is a proxy, it SHOULD add
the parameter comp=sigcomp to its URI in the Record-Route header
field.
...
... If a 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 that Record-Routes sends a compressed request, it SHOULD add
comp=sigcomp to its URI in the Record-Route header field.
...
... If a client sends a compressed request, it SHOULD add the parameter
comp=sigcomp to the topmost entry of the Via header field.
...
...
If a client does not know whether or not the server supports SigComp,
but in case the server supported it, it would like to receive
compressed responses, this client ...
... compressed responses, this client SHOULD add the parameter
comp=sigcomp to the topmost entry of the Via header field. The
request, however, as stated above, will not be compressed.
...
... For requests within a dialog, a next-hop URI with the comp=sigcomp
parameter is obtained from a Record-Route ...
... can also obtain SIP URIs with comp=sigcomp in a Contact header field
in a 3xx or 485 response to the request.
...
... session will not typically be willing
to wait until the dialog is established in order to begin compressing
messages. One of the biggest gains that SigComp can bring to SIP is
the ability to compress the initial INVITE ...
... session to be established. Therefore, clients
need a means to obtain a comp=sigcomp URI from their outbound proxy
...
... outbound proxy. The outbound
proxy can provide an alternative SIP URI with the comp=sigcomp
parameter in a Contact header field in a 200 OK response to the
...
... REGISTER a SIP URI
with comp=sigcomp in their registrar. All incoming requests for the
user will be sent to this SIP URI using compression ...
... header field. If the topmost Via header field contains the parameter
comp=sigcomp, the response SHOULD be compressed. Otherwise, the
response MUST NOT be compressed.
...
... route set. If this URI
contains the parameter comp=sigcomp, the proxy SHOULD add
comp=sigcomp ...
... sigcomp, the proxy SHOULD add
comp=sigcomp to its entry in the Record-Route header field. If this
URI ...
... Record-Route header field. If this
URI does not contain the parameter comp=sigcomp, the proxy SHOULD
remove ...
... proxy SHOULD
remove comp=sigcomp (if it is present) from its entry in the Record-
Route header field ...
...
The same way, a user agent server SHOULD add comp=sigcomp to the
Contact header field of the response if the URI ...
... proxy MAY choose not to compress the request even if the URI contains
the comp=sigcomp parameter.
...
... SIP request arrives to a SIP server that does not
understand SigComp, the server will not have any means to indicate
the error to the client. The message will be impossible to parse,
...
... header fields. We have rather focus on the contents of the header
fields and on the presence (or absence) of the "comp=sigcomp"
parameter.
...
... P1 is the outbound proxy of the UAC, and it supports SigComp. The
UAC is configured to send compressed traffic ...
... UAC wants to receive
future requests and responses for this dialog compressed. Therefore,
it adds the comp=Sigcomp parameter to the Via and to the Contact
header fields.
...
... Record-Route header field of the 200 OK (5). In the
INVITE (3), P2 did not used the comp=sigcomp parameter. Now it adds
it in the 200 OK (5). This will allow the UAC sending compressed
...
... P1 sends the 200 OK (6) compressed to the UAC because the Via header
field contained the comp=sigcomp parameter.
(7) ACK ...
... could make a SIP entity send compressed messages to another SIP
entity that did not support SigComp. Appropriate integrity
mechanisms should be used to avoid this attack.
...
... Price, R., Bormann, C., Christoffersson, J., Hannu, H., Liu, Z. and J. Rosenberg, "Signaling Compression (SigComp)", RFC 3320prop, January 2003. ...