Subject: [Sipping] RE: SIPPING WG - 3 - NITS Review - draft-ietf-sip-cc-transfer-05. txt

From: "Mary Barnes" <[email-masked]>
Date: Thu, 15 Nov 2001 20:59:09 -0600

Robert,

The following are the items of note from my NITS review of the cc-transfer
draft:

- Abstract - At just over 2 lines, the abstract could probably contain just
a bit more information.  There is also a typo in the 2nd line as the phrase
"Transfer capabilities" is an incomplete sentence.  I would suggest the
following:
" This document describes providing Call Transfer capabilites using the SIP
REFER [3]. This work is part of the Call Control Framework. This document
describes both basic (blind) and consultation hold transfers. In addition,
mechanisms for hiding information about the Transfer Target, Error Scenarios
and Forking interactions are also described.  This document does not address
Transfer functionality which results in adhoc conferences."

- Section 1, Overview, 1st para, 2nd line - typo - Delete "Transfer
capabilities." incomplete sentence.

- Section 1, Overview, I would suggest rewording the last paragraph just to
summarize that this draft is based upon REFER (I think the "Changes from ...
-04" section can be used to describe the split.) 

- Section 3,definition of Transfer Target should probably be reworded to
remove the use of call and use "dialog" or "session" (although, this is
probably a more general issue with this draft and others that pre-date
bis-05.  Should these drafts all be updated to be consistent with the new
terminology or is the use of this "informal term" okay? )

- Section 5, last para, last sentecnce, the use of hold SDP refers to RFC
2543.  Should this reference not be to the new SDP offer-answer draft? 

- Section 6, 2nd para, 1st sentence, delete the word "indicate" so that the
1st sentence reads:
"The diagrams below show the first line of each message."  

- Section 6, 2nd para, 3rd sentence, for consistency "reINVITE" should be
"re-INVITE"

- Section 6.1 (and a more general comment on the call flows).  
   - Either the flows need to be numbered and each message described or a
bit more should be added to the flows for clarity.  
   - I would also suggest that the INVITE/200OK/ACK be replaced with a
general box or dashed line that reads "SIP Session Established between
Tranferor and Transferee".  
   - Do you really need to show the BYE from the Tranfer Target to the
Transferee?  This really has nothing to do with the REFER or the Transfer.
I would suggest adding a dashed line and the description that reads "SIP
Session Established between Transferee and Transfer Target" and removing the
last BYE/200 OK sequence.  Certainly, anyone that understands basic SIP
should see whats happening, but in the absence of text describing the flows,
annotation of the diagrams is extremely useful.  (Note: this comment applies
to all the flows which seem to have this BYE/200 OK). 

- Section 7.1, per my comments on 6.1, I think some sort or annotation or
detailed text is necessary to add clarity to the call flow with the
following annotation being particularly useful:
    - between the 3rd and 4th messages, some sort of annotation that the
"consultation between transferor and Transfer Target is underway". 

- Section 7.2 and 7.3 - same comments as for 7.1 per the clarity of
annotation or detailed text for the flows. 

- Section 7.5 - Does this really belong in this draft?  I'm asking this more
from a dependency perspective, since I don't see the REPLACES draft being
progressed prior to this draft, thus this seems to be normative
functionality.  Although, I guess it could be argued that you can do the
consultation hold less elegantly without the Replaces header.    

- Section 9 - Open Issues - Since there are none (except perhaps the use of
Replaces header), then the section should be removed.

- Security Considerations - At a minimum, the mechanism to protect the
identity of the Transfer Target could be described.  

- References - need to be updated to most recent versions of drafts and
should probably include a reference to bis-05.

Regards,
Mary H. Barnes
[email-masked]
972-684-5432
Wireless 817-703-4806