Subject: [MMUSIC] Question on draft-ietf-mmusic-kmgmt-ext-15

From: "Elwell, John" <[email-masked]>
Date: Thu, 20 Oct 2005 14:48:33 +0100

In section 7.1, first bullet it states:
"When referring to streams described in SDP, MIKEY SHALL allocate two
consecutive numbers for the related Crypto Session indexes (as each stream
can be bi-directional). An example: if the SDP contains two m lines
(specifying whatever direction of the streams), and MIKEY is at the session
level, then MIKEY allocates e.g. the Crypto Sessions Identifiers (CS IDs,
see [MIKEY)] '1' and '2' for the first m line, and '3' and '4' for the
second m line."
My question is, what if not all m= lines use SRTP transport, e.g., some use
RTP transport? Must MIKEY still allocate Crypto Sessions for each m= line,
even though there is no way of indicating anything other than "SRTP" as the
protocol type in the security profile of a Crypto Session? Or does the
statement quoted above apply only to media that require a security profile?

Consider this example:
m=xxxx ppp RTP/SAVP
m=xxxx ppp RTP/AVP
m=xxxx ppp RTP/SAVP
Must I allocate 6 Crypto Sessions (2 for each m= line) for this, i.e, CS ID
1 and 2 to the first, CS ID 3 and 4 to the second, etc.? If so, what goes in
the protocol type of the security profile for the CS ID 3 and CS ID 4
entries in the CS ID map?
Or can I allocate just 4 Crypto Sessions, which implicitly would apply to
the first and last m= lines?

Consider also this example:
m=xxxx ppp RTP/SAVP
m=xxxx ppp RTP/SAVP
m=xxxx ppp RTP/AVP
A similar question, although note here that the SRTP media are contiguous,
so if I only allocate 4 Crypto Session, then they would map to the first and
second m= lines (i.e., no gap). Would this be preferable, or do I still need
to allocate 6?

John

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From: "Karl Norrman (KI/EAB)" <[email-masked]>
Date: Fri, 21 Oct 2005 16:21:16 +0200

Hello!

A Crypto session is equivalent to an SRTP session 
when using the SRTP profile in MIKEY (see Appendix 
A of RFC 3830).  Hence, no other media than SAVP (in your example) can 
be regarded as a Crypto Session.  So for your examples below, 
4 is the answer (only SAVP counts).

Regards,
Karl

> -----Original Message-----
> From: Elwell, John [mailto:[email-masked]]
> Sent: den 20 oktober 2005 15:49
> To: Jari Arkko (JO/LMF); [email-masked]; Fredrik
> Lindholm (AL/EAB); Mats Näslund (KI/EAB); Karl Norrman (KI/EAB)
> Cc: [email-masked]; Fries, Steffen
> Subject: Question on draft-ietf-mmusic-kmgmt-ext-15
> 
>