Re: draft-wing-sipping-srtp-key-00.txt

[dan_york@xxxxxxxxx]

Dan,

Thanks for putting forward an interesting
draft.  I'm still thinking it through but in the meantime I have a
couple of questions related to the text of what you wrote.

1. In Figure 1 in section 3.2 you show
two lines of "rcrypto" and it's not clear to me why.  If
I understand the idea correctly, in a "normal" voice conversation
between two phones would there not be one "crypto" line and ONE
"rcrypto" line?    Is the example in Figure 1 just
to show that there *could* be multiple rcrypto lines?  (If that's
the case, for the sake of clarity can I suggest that the first example
only have the "regular" number of lines.)

2. I notice the extension of crypto
with "SSRC".  How is it to be delimited within the crypto
value?  Is it just on its own line?  I have not worked enough
with the parsing of the crypto line to know how SIP implementations handle
it, but purely reading the spec, seeing a separate line and an additional
"=" sign would make me curious how this would be parsed.

3. In Section 7, "Examples",
none of the examples contain the SSRC line.  Was this intentional
or just an oversight?

4. I think it would be helpful to include
in the draft an example or narrative description from a slightly higher
level view of where this PUBLISH message fits into the overall SIP call
flow. In order to have both keys, it obviously has to occur after the SIP
INVITEs, etc. where the call has been established... yet also needs to
occur before the audio really starts streaming.  (Or does it?  Is
there a race condition here?)  I'm not saying you have to rehash the
whole of RFC 3903, but a quick summary of the process and/or another example
showing the high-level packet flow would be very helpful to those seeking
to understand the proposal.

As I said, I'm still thinking through
the implications of the proposal, but thought I throw out these more formatting-related
questions in the meantime.

My 2 cents,
Dan

-- 
Dan York, CISSP
Dir of IP Technology, Office of the CTO
Mitel       http://www.mitel.com
dan_york@xxxxxxxxx +1-613-592-2122
PGP key (F7E3C3B4) available for 
secure communication