| Author |
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Still Hunting
Guest
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 Posted:
Fri Oct 08, 2004 1:35 pm Post subject:
SIP clarifications? |
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SIP is supposed to be an "application layer control protocol" in the
RFC. What exactly does the phrase mean?
What is a control protocol and what is an application layer control
protocol? Could someone give examples?
Secondly, the RFC says SIP is not a vertically integrated
communications system. I am interpreting this
statement to mean that SIP does not provide details of every layer of
the protocol stack, and different
solutions for these layers can be mixed and matched to provide a
functioning communications infrastructure. Am I right? |
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Phil McKerracher
Guest
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| Posted:
Sun Oct 10, 2004 4:52 pm Post subject:
Re: SIP clarifications? |
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"Still Hunting" <hunt4blueseptember@yahoo.co.uk> wrote in message
news:f6d99f40.0410080135.38f054e4@posting.google.com...
| Quote: | SIP is supposed to be an "application layer control protocol" in the
RFC. What exactly does the phrase mean?
What is a control protocol and what is an application layer control
protocol? Could someone give examples?
|
An "application" is typically a program running on a PC or in a phone that
interacts with the user. In this case, the user would control the call
somehow by instructing the application, for example by lifting a handset or
clicking a mouse. SIP doesn't care how this is done, because that detail is
"above" the application layer.
The particular format and timing that SIP uses for the control information
is the "protocol". The messages would typically be carried over an IP
connection, but SIP doesn't really care if they go by carrier pigeon or
smoke signals, because this mechanism is "below" the application layer.
Also, SIP doesn't care how the voice information is carried once the call is
set up. It would typically be in an RTP session but this detail is also
outside the application layer. All SIP specifies is how to initiate a
session, hence the name.
| Quote: | ...different
solutions for these layers can be mixed and matched to provide a
functioning communications infrastructure. Am I right?
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Right.
--
Phil McKerracher
www.mckerracher.org |
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Still Hunting
Guest
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| Posted:
Tue Oct 12, 2004 8:39 am Post subject:
Re: SIP clarifications? |
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Thanks Phil.
Cheers,
SH
"Phil McKerracher" <phil@mckerracher.org> wrote in message news:<1gaad.5913$xb.5403@text.news.blueyonder.co.uk>...
| Quote: | "Still Hunting" <hunt4blueseptember@yahoo.co.uk> wrote in message
news:f6d99f40.0410080135.38f054e4@posting.google.com...
SIP is supposed to be an "application layer control protocol" in the
RFC. What exactly does the phrase mean?
What is a control protocol and what is an application layer control
protocol? Could someone give examples?
An "application" is typically a program running on a PC or in a phone that
interacts with the user. In this case, the user would control the call
somehow by instructing the application, for example by lifting a handset or
clicking a mouse. SIP doesn't care how this is done, because that detail is
"above" the application layer.
The particular format and timing that SIP uses for the control information
is the "protocol". The messages would typically be carried over an IP
connection, but SIP doesn't really care if they go by carrier pigeon or
smoke signals, because this mechanism is "below" the application layer.
Also, SIP doesn't care how the voice information is carried once the call is
set up. It would typically be in an RTP session but this detail is also
outside the application layer. All SIP specifies is how to initiate a
session, hence the name.
...different
solutions for these layers can be mixed and matched to provide a
functioning communications infrastructure. Am I right?
Right. |
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