[reSIProcate] RFC Question...

[John Draper]

kaiduan xie wrote:

>John,
>
>Please see the inline comments.
>
>kaiduan
>--- John Draper <lists at webcrunchers.com> wrote:
>
>  
>
>>Hi,
>>
>>I have a question about the interpretation of the
>>RFC 3261.  Cam someone 
>>explain a few
>>things for me?  It is part of my feeble effort to
>>understand what A 
>>dialog is,
>>and how it relates to requests, when they are
>>created, and what they 
>>contain.
>>
>>The RFC says....
>>
>>12.2.1.1 Generating the Request   
>>
>>     A request within a dialog is constructed by
>>using many of the   
>>     components of the state stored as part of the
>>dialog.
>>
>>Ok - what do they mean by a request within a dialog?
>>  Does this mean
>>I instantiate a "dialog" object at the same time I
>>send the INVITE?
>>    
>>
>
>The request in a dialog may be re-INVITE, BYE message
>if the dialog is created by INVITE message. For
>SUBSCRIBE created dialog, the in-dialog request may be
>SUBSCRIBE which is used to refresh the subscription.
>  
>
So - you say a SUBSCRIBE would be a request within a dialog?

>"12.1 Creation of a Dialog
>
>   Dialogs are created through the generation of
>non-failure responses to requests with specific
>methods.  Within this specification, only 2xx and
>101-199 responses with a To tag, where the request was
>  INVITE, will establish a dialog."
>  
>
I just got to this section last night.  But I'm still trying understand it.
For instance "Within this specification, only 2xx and 101-199 responses 
with
a To tag...."  was it implying that responses will have a "To" tag in it?

>>and a request that is NOT in the dialog,  would be
>>like the REGISTER?
>>is that right?
>>    
>>
>
>REGISTER message does not create dialog, now only
>INVITE and SUBSCRIBE message creates dialog.
>  
>
This answered my question I had above this.

>  
>
>>The RFC goes on to say.... "using many of the
>>components of the state".
>>What is the meaning of the word "components" in this
>>context?  and
>>it states that the state is stored as part of the
>>dialog.  If that's the
>>case, then why is it part of SipSession?  Do all
>>dialogs have SipSessions?
>>
>>But the word "components" really confuses me when
>>used in this context.
>>    
>>
>
>The components of the state means: dialog ID, a local
>sequence number, a remote sequence number, a local
>URI, a remote URI, remote target, ...
>  
>
Oh,  so a Component is like a "header field" or related to them.  Right?

>Please see Page 70 of RFC 3261.
>
>"A dialog contains certain pieces of state needed for
>further message transmissions within the dialog.  This
>state consists of the dialog ID, a local sequence
>number (used to order requests from the UA to
>   its peer), a remote sequence number (used to order
>requests from its peer to the UA), a local URI, a
>remote URI, remote target, a boolean flag called
>"secure", and a route set, which is an ordered list of
>URIs.  The route set is the list of servers that need
>to be traversed to send a request to the peer."
>  
>
I had trouble associating a "Piece of state" with a header field.
But interpreting what you said,  this is what I understand.

John