Subject: [Sip] 180 for PRACK

From: "suryakanta mandal" <[email-masked]>
Date: Fri, 25 Jan 2008 17:08:24 +0530

Hi ,

If you look at the RFC 3262, it says in Section 4: UAC behaviour

Header field          where   PRACK
___________________________________
 Alert-Info             180            -
Contact                1xx            -
 Contact                3xx           o
Error-Info           300-699         o
Record-Route      2xx,18x       o

 and If you look at the functionality of these column from RFC 3261
"The "where" column describes the request and response types in which
   the header field can be used.  Values in this column are:

      R: header field may only appear in requests;

      r: header field may only appear in responses;

      2xx, 4xx, etc.: A numerical value or range indicates response
           codes with which the header field can be used;

      c: header field is copied from the request to the response.

      An empty entry in the "where" column indicates that the header
           field may be present in all requests and responses.

   The "proxy" column describes the operations a proxy may perform on a
   header field:

      a: A proxy can add or concatenate the header field if not present.

      m: A proxy can modify an existing header field value.

      d: A proxy can delete a header field value.

      r: A proxy must be able to read the header field, and thus this
           header field cannot be encrypted.

   The next six columns relate to the presence of a header field in a
   method:

      c: Conditional; requirements on the header field depend on the
           context of the message.

      m: The header field is mandatory.

      m*: The header field SHOULD be sent, but clients/servers need to
           be prepared to receive messages without that header field.

      o: The header field is optional.

      t: The header field SHOULD be sent, but clients/servers need to be
           prepared to receive messages without that header field.

           If a stream-based protocol (such as TCP) is used as a
           transport, then the header field MUST be sent.

      *: The header field is required if the message body is not empty.
           See Sections 20.14, 20.15 and 7.4 for details.

      -: The header field is not applicable.
"

I got struck on these above points.
Can you let me know the scenario when the UAS will generate 180 for PRACK ?
 and when UAS will generate 3xx response for PRACK because their it
mentioned optional means UAS may or may not generate 3xx response.

Surya
Aricent

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