Subject: [AVTCORE] WG last call on draft-ietf-avtcore-6222bis-01

From: Magnus Westerlund <[email-masked]>
Date: Tue, 12 Mar 2013 15:04:59 -0400

WG,

This is to announce the start of a WG last call on:

Guidelines for Choosing RTP Control Protocol (RTCP) Canonical Names
(CNAMEs) to be published as a proposed standard.

Document can be retrieved here:
https://datatracker.ietf.org/doc/draft-ietf-avtcore-6222bis/

Please provide any feedback by the 31st of March.

Regards

Magnus Westerlund
WG chair

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Multimedia Technologies, Ericsson Research EAB/TVM
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Ericsson AB                | Phone  +46 10 7148287
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From: Magnus Westerlund <[email-masked]>
Date: Mon, 25 Mar 2013 17:07:35 +0100

WG & Authors,

I have reviewed this document as an individual and have the following
comments:

1. Section 4.2, second bullet:

      To produce a short-term persistent RTCP CNAME, an RTP endpoint
      MUST either (a) use the numeric representation of the layer-2
      (Media Access Control (MAC)) address of the interface that is used
      to initiate the RTP session as the "host" part of its RTCP CNAME
      or

Is using the MAC really that unique? In these days of MAC cloning is
this good enough to use as long term persistent CNAME identifier? I also
wonder of its persistence behavior as it says to use the MAC of the
Interface that ones initiate the communication over. With multiple
interfaces, I can in the context of an application use all of these
interfaces over a set of calls. Thus it doesn't have particular good
long term stability either.

Should this option simply be removed? Or at least some discussion of
these deficiencies?

2. Section 6.1:

Secure RTP (SRTP) [RFC3711] keeps unauthorized entities out of an RTP
   session, but it does not aim to prevent impersonation attacks from
   unauthorized entities.

Shouldn't the last "unauthorized" be "authorized". Unauthorized packets
will never be processed where the impersonation matters.

Otherwise this looks good.

Cheers

Magnus

On 2013-03-12 20:04, Magnus Westerlund wrote:
> _______________________________________________
> Audio/Video Transport Core Maintenance
> [email-masked]
> https://www.ietf.org/mailman/listinfo/avt
> 
> 

-- 

Magnus Westerlund

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From: "Ali C. Begen (abegen)" <[email-masked]>
Date: Mon, 25 Mar 2013 20:00:58 +0000

Thanks for the review. 

> this good enough to use as long term persistent CNAME identifier? I also

The probability of clash is pretty small but we can make a note of this. 

> long term stability either.

I think it is meant to say the interface over which the initial connection was made not all other possible interfaces that could be used during the rtp session. 
> will never be processed where the impersonation matters.

Yup. 
> Otherwise this looks good.

Thanks.

---

From: Steve Underwood <[email-masked]>
Date: Tue, 26 Mar 2013 07:39:30 +0800

> The probability of clash is pretty small but we can make a note of this.
That depends on the platform. If you use the MAC address on a virtual 
machine it always clashes, as it always appears to be zero.

Steve

---

From: Magnus Westerlund <[email-masked]>
Date: Tue, 26 Mar 2013 10:49:22 +0100

On 2013-03-25 21:00, Ali C. Begen (abegen) wrote:
>> wonder of its persistence behavior as it says to use the MAC of
>> the Interface that ones initiate the communication over. With
>> multiple interfaces, I can in the context of an application use all
>> of these interfaces over a set of calls. Thus it doesn't have
>> particular good long term stability either.
> 
> I think it is meant to say the interface over which the initial
> connection was made not all other possible interfaces that could be
> used during the rtp session.
>> 

The main point I try to get across is that which interface you use for
the initial connection varies between different communication
establishments. If your goal is to have a long term persistent
identifier then you need to store the first one used in the context of
an application and use that, rather than take the interface you used for
the SIP dialog, or similar, used to establish this particular RTP
session(s).

Cheers

Magnus Westerlund

---

From: "Ali C. Begen (abegen)" <[email-masked]>
Date: Tue, 26 Mar 2013 09:57:02 +0000

-----Original Message-----
From: Magnus Westerlund <[email-masked]>
Date: Tuesday, March 26, 2013 11:49 AM
To: "Ali C. Begen" <[email-masked]>
Cc: "[email-masked]" <[email-masked]>,
"[email-masked]"
<[email-masked]>
Subject: Re: [AVTCORE] WG last call on draft-ietf-avtcore-6222bis-01

>the SIP dialog, or similar, used to establish this particular RTP

The text is not saying to use MAC for long-term persistent CNAME. It says
to use it for *short-term* persistency. Sorry, I am not getting where
there is unclarity.

---

From: "Ali C. Begen (abegen)" <[email-masked]>
Date: Tue, 26 Mar 2013 09:58:05 +0000

-----Original Message-----
From: Steve Underwood <[email-masked]>
Date: Tuesday, March 26, 2013 1:39 AM
To: "[email-masked]" <[email-masked]>
Subject: Re: [AVTCORE] WG last call on draft-ietf-avtcore-6222bis-01

>machine it always clashes, as it always appears to be zero.

I checked mine and that is not the case for mine. If an OS uses a MAC of
all zeros, I think it would have more serious issues than the uniqueness
of its CNAME.

---

From: Dan Wing <[email-masked]>
Date: Tue, 26 Mar 2013 08:45:51 -0700

> to use it for *short-term* persistency. Sorry, I am not getting where

I think what Magnus is saying is that one person's long term is another person's short term, and the text needs to explain this situation.  How about this:

    For the duration of an RTP session, different interfaces
    might be used.  For example, a single RTP session might be
    established on a WiFi interface and a mobility event moves
    that session to a 3G interface.  When such an interface change
    occurs, the same CNAME MUST be retained.

-d

---

From: "Ali C. Begen (abegen)" <[email-masked]>
Date: Tue, 26 Mar 2013 15:51:43 +0000

-----Original Message-----
From: Dan Wing <[email-masked]>
Date: Tuesday, March 26, 2013 5:45 PM
To: "Ali C. Begen" <[email-masked]>
Cc: Magnus Westerlund <[email-masked]>,
"[email-masked]"
<[email-masked]>, "[email-masked]" <[email-masked]>
Subject: Re: [AVTCORE] WG last call on draft-ietf-avtcore-6222bis-01

>I think what Magnus is saying is that one person's long term is another
>person's short term, and the text needs to explain this situation.  How
>about this:
>

Regardless of what method you use to produce a CNAME or how many
interfaces you have or whether you roam from one to another during an RTP
session, you must keep the same CNAME anyway. I think we wanted to say
this thru "In either case, the procedure is performed once per
initialization of the software." But your clarification is helpful, I
agree.

---

From: Magnus Westerlund <[email-masked]>
Date: Tue, 26 Mar 2013 17:40:44 +0100

> to use it for *short-term* persistency. Sorry, I am not getting where

Sorry, about the short term vs. long term persistence. My mixup.

I think the text that exist is likely to produce the desired result, but
not really clear. As the aspect that the same short term persistent
CNAME needs to be used over all the RTP sessions part of the same
communication session is not that explicit.

One improvement could be to say:

   o  To produce a short-term persistent RTCP CNAME, an RTP endpoint
      MUST either (a) use the numeric representation of the layer-2
      (Media Access Control (MAC)) address of the interface that is used
      to initiate the initial set of RTP sessions as the "host" part of
                      ^^^^^^^^^^^^^^            ^
its RTCP CNAME or

Cheers

Magnus Westerlund

---

From: Magnus Westerlund <[email-masked]>
Date: Tue, 26 Mar 2013 17:45:31 +0100

> initialization of the software." But your clarification is helpful, I

Exactly, this what was I was after. The main point is the need to
continue using the same CNAME during the whole communication session
that include any set of RTP sessions.

I will leave it the authors hands to do what you think are the best word
smithing to improve this.

Cheers

Magnus Westerlund

---

From: Magnus Westerlund <[email-masked]>
Date: Thu, 28 Mar 2013 11:01:38 +0100

WG,

So far there has be no other reviews of this document than mine.

Can someone please review this document?

I hereby extended the WG last call with one week until the 7th of April.

Cheers

Magnus

-- 

Magnus Westerlund