Re: [Sipping] Question on draft-ietf-sipping-v6-transition-07

["Elwell, John" <[e-mail]>]

Vijay,

Yes, I know we are talking SDP, but the SDP ABNF was so imprecise that I looked elsewhere. I am not sure where the definitive source is, but I just took SIP as an example, which seemed to suggest that the people who wrote RFC 3261 thought that a single element (without any dot) was wrong. This could mean that if you take a single element and use it as input to the DNS mechanism, you get the wrong outcome, and hence including a single element in SDP would be equally wrong. Kevin's message seems to support that belief.

John
 

> -----Original Message-----
> From: Vijay K. Gurbani [mailto:[e-mail]] 
> Sent: 05 February 2010 16:32
> To: Elwell, John
> Cc: [e-mail]
> Subject: Re: [Sipping] Question on draft-ietf-sipping-v6-transition-07
> 
> Elwell, John wrote:
> > Thanks, but I was concerned that a domain name beginning with "."
> > might be wrong; Taking the SIP ABNF as an example (SDP ABNF isn't so
> > precise), we have:
> > 
> > hostname         =  *( domainlabel "." ) toplabel [ "." ]
> 
> John: Quite true.  However, in the case we are talking about,
> the ".invalid" appears in the SDP, which is governed by the
> SDP ABNF.  The ".invalid" is not appearing in the URI, but
> in the "c=" line in SDP.
> 
> The SDP ABNF in rfc4566 has this grammar for the
> "c=" line:
> 
> connection-field =    [%x63 "=" nettype SP addrtype SP
>                           connection-address CRLF]
> connection-address =  multicast-address / unicast-address
> unicast-address =     IP4-address / IP6-address / FQDN / extn-addr
> extn-addr =           non-ws-string
> non-ws-string =       1*(VCHAR/%x80-FF)
>                        ;string of visible characters
> 
> Does not ".invalid" in the SDP result from the extn-addr
> production rule above?  Consequently, should it not be legal?
> Or am I missing something here?
> 
> Thanks,
> 
> - vijay
> -- 
> Vijay K. Gurbani, Bell Laboratories, Alcatel-Lucent
> 1960 Lucent Lane, Rm. 9C-533, Naperville, Illinois 60566 (USA)
> Email: vkg@{alcatel-lucent.com,bell-labs.com,acm.org}
> Web:   http://ect.bell-labs.com/who/vkg/
>