Subject: Re: [Sip] I-D ACTION:draft-mills-sip-access-network-info-01.txt

From: [email-masked]
Date: Wed, 15 May 2002 15:41:37 +0100 (BST)

Bob,

Many thanks for your comments.  It is re-assuring to know that some IETF experts have reviewed my draft.

Please consider my comments below.  I look forward to your further input, if necessary.

Regards,

Duncan

Hi,

1) The examples given in section 4 (a laptop in an airport or hotel) do not
sound like access networks that will provide the "transitive trust" required
to protect privacy as described in section 6. Are these really valid
examples for usage of this header? Or are you assuming that this would only
work for local ISPs and airports that had a business relationship with the
home network? How does the UA know if these types of access networks can be
trusted?

The model I was thinking of is that the user trusts the access network, because his home network provider trusts the access network.  This is stated in my draft.

2) Does this draft need an explicit Applicability Statement?

I think the draft could be applicable to various systems, but obviously I am writing it primarily with a 3GPP requirement in mind.  Do you think I need to add an explicit Applicability Statement?  My IETF procedural knowledge is (I'm afraid) limited.

3) Section 6 says:

    The serving proxy MUST delete this header before
    forwarding the message outside of the its domain.

but section 7 says:

    A serving proxy, typically located in the home network, and therefore
    trusted, SHOULD delete the header when the SIP signaling is forwarded
    beyond the home network domain

and section 8 says:

    This header SHOULD always be deleted by the serving network prior to
    forwarding it outside of the home network domain, as described in
    section 7.

Is it MUST or SHOULD? Also, I think it is sufficient to have the MUST or
SHOULD once (in the Proxy behavior section) or maybe twice, and then say
"...serving proxies will delete..." in other places you need to talk about
it. I realize it is very important.

You are correct, there is inconsistency.  I'll correct this.

4) The document has weird characters where single quotes (i.e. ') should be.

My version doesn't.  I'll check this out.

5) You say "... where the access-type is æ3GPP-GERANÆ, the access-info
SHALL be "3GPP-CGI".", but go on to says the mapping of access-type to
access-info is defined elsewhere. Can you provide a reference? Also, I don't
think you should use the requirements language (SHALL) for an example like
this. If there are mapping requirement, they should all be included or you
should refer to a document that defines them.

Okay, I was told I couldn't refer to a 3GPP document in an RFC.  I don't think it matters.  The fields specified in the draft are containers that can carry anything anyone defines or doesn't define.  It's just that in our 3GPP specifications, we say "we're going to use the access-network-info header, and we're going to put parameter x in the 'Access-Info' field.  The receiver knows parameter x will be in that field.  I don't want to have this defined in two documents.  Maybe I should just remove the statement saying that it is defined elsewhere?

6) The period is missing between 'request' and 'The' in section 7.1 "... SIP
message request The UAC SHOULD ..."

Thanks.

7) Section 7.1, 2nd paragraph. Should "the nature or the information" be
"the nature *of* the information"?

Ooops.  Thanks.

8) Section 7.2 is labeled "UAS behavior", but talks only about proxy
behavior. I don't think there is any UAS behavior for this header.

Does 'Proxy behaviour' cover the case of a B2BUA?

9) In section 7.2 you say the proxy "MAY use the contents to, e.g., provide
...". I suggest you remove the "e.g." and say something like "... MAY use
the contents to provide a different service or apply performance enhancement
measures depending on the network through which the UA is
accessing the server. For example, ....".

Sounds reasonable, I'll make this change.

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---

From: "Bob Penfield" <[email-masked]>
Date: Mon, 20 May 2002 09:51:40 -0400

----- Original Message -----
>From: <[email-masked]>
>
>Bob,
>
<snip>
>I think the draft could be applicable to various systems,
>but obviously I am writing it primarily with a 3GPP
>requirement in mind.  Do you think I need to add an
>explicit Applicability Statement?  My IETF procedural
>knowledge is (I'm afraid) limited.
>
Almost all of the other P-header proposals include one. I think due to the
special circumstances required for this header, there needs to be one. I
think it is just a matter of organizing all of the applicability information
you already have into a formal Applicability Statement section.

<snip>
>Does 'Proxy behaviour' cover the case of a B2BUA?
There is no mention of a B2BUA, and I don't see anything in this draft would
turn a proxy into a B2BUA. In any event, you are talking about an
intermediary (proxy, B2BUA, or whatever you call it) as opposed to an
endpoint. It seems to me both 7.2 and 7.3 are talking about the same thing.

cheers,
(-:bob