Subject: [MMUSIC] 4566bis and private IP addresses in the origin line

From: "Miguel A. Garcia" <[email-masked]>
Date: Fri, 20 Jan 2012 09:03:48 +0100

<as an individual>

Folks,

you know we have a revision of rfc4566 open in the format of this draft:

http://datatracker.ietf.org/doc/draft-ietf-mmusic-rfc4566bis/

I was reading the description of the origin line, and I found something 
that might be out of date, and we may want to revise. I would like to 
hear other opinions.

The origin line is described in Section 5.2 of RFC 4566, and it has the 
following format:

       o=<username> <sess-id> <sess-version> <nettype> <addrtype>
         <unicast-address>

Let's take a look at the description of <unicast-address>. The RFC says:

                 ... For both IP4 and IP6, the fully
       qualified domain name is the form that SHOULD be given unless this
       is unavailable, in which case a globally unique address MAY be
       substituted.  A local IP address MUST NOT be used in any context
       where the SDP description might leave the scope in which the
       address is meaningful (for example, a local address MUST NOT be
       included in an application-level referral that might leave the
       scope).

Ok, so if I write an IP address, it has to be globally routable, or I 
need to make sure that the SDP is not going beyond the domain where it is 
routable. So, I cannot write private IP addresses... got it!!

But now, take a look at ICE, RFC 5245. I haven't seen ICE saying anything 
about the o= line in SDP, but I can see the examples in Section 4.3, 
where the o= line contains a private IP address. And later in Section 17, 
where again the o= line is populated with a private IP address-

So, I guess RFC 5245 should have updated RFC 4566 at least in this 
aspect. But since that wasn't done, and since we have 4566bis in the 
pipe, I wonder if it is time to amend the quoted paragraph and change the 
MUST NOT by a "SHOULD NOT", and explain that if you are using ICE, as a 
mechanism to traverse NATs, then you can write private IP addresses in 
the origin line.

Comments?

BR,

        Miguel
-- 
Miguel A. Garcia
+34-91-339-3608
Ericsson Spain

---

From: Ari Keranen <[email-masked]>
Date: Tue, 31 Jan 2012 18:23:19 +0200

Hi Miguel,

On 1/20/12 10:03 AM, Miguel A. Garcia wrote:
[...]
> pipe, I wonder if it is time to amend the quoted paragraph and change
> the MUST NOT by a "SHOULD NOT", and explain that if you are using ICE,
> as a mechanism to traverse NATs, then you can write private IP addresses
> in the origin line.
>
> Comments?

I think you are right and your proposal for fixing the issue is good.

Although, later on RFC4566 does say "arbitrary <username> and private 
<unicast-address> MAY be chosen to populate the "o=" field [for privacy 
reasons]", so ICE is not technically violating RFC4566, but definitely 
it would make sense to be more clear with that in the bis version.

By the way, one nit: 4566bis should also say in the abstract that it's 
obsoleting 4566.

Cheers,
Ari