Comments inline...
-----Original Message-----
From: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED] On Behalf Of Zhenyu Wu
Sent: Sunday, March 05, 2006 7:25 PM
To: [email protected]
Subject: [Sip-implementors] A confusion about RFC3261
Hello,
Please read the paragraph in RFC3261 below:
SIP does not provide services. Rather, SIP provides primitives that
can be used to implement different services. For example, SIP can
locate a user and deliver an opaque object to his current location.
If this primitive is used to deliver a session description written in
SDP, for instance, the endpoints can agree on the parameters of a
session. If the same primitive is used to deliver a photo of the
caller as well as the session description, a "caller ID" service can
be easily implemented. As this example shows, a single primitive is
typically used to provide several different services.
In the first sentence, what does the "services" mean? I think it must
not have the same meaning as the "service" which defined in the
protocol. That is, if there is a layered protocol, layer N will provide
service to layer N+1.
[ABN] In simple terms, the services mean that end user features. Just
SIP stack without any other protocols can't be used.
[ABN] Here the services mean that SIP services like voice call,
offer-answer negotiation, or any new features you can think of assuming
SIP as a platform.
[ABN] Just for instance physical layer of the OSI stack can't be used
alone, but should be used in conjunction with other upper layers. In a
similar way SIP has to be used in conjunction with other upper layers to
define the services. And SIP itself does not define any features.
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