Subject: [AVT] CNAME question

From: "Peter Barany" <[email-masked]>
Date: Wed, 11 Dec 2002 07:26:38 -0600

Hi,

RFC 1889 (and the RFC 1889bis Internet draft) state that the use of the
CNAME in RTCP SDES packets is mandatory.

Regarding the format of CNAME, the following is written:

The CNAME item SHOULD have the format "user@host", or "host" if a user name
is not available as on single- user systems. For both formats, "host" is
either the fully qualified domain name of the host from which the real-time
data originates, formatted according to the rules specified in RFC 1034 [6],
RFC 1035 [7] and Section 2.1 of RFC 1123 [8]; or the standard ASCII
representation of the host's numeric address on the interface used for the
RTP communication. 

Question: Does this imply that there SHOULD be a DNS entry for the client
(i.e., A/AAAA records that map FQDNs to IPv4/IPv6 addresses and PTR records
that map IPv4/IPv6 addresses to FQDNs)? If so, does the IPv4/IPv6 source
address of the RTCP packet (and associated RTP packets) have to match the
DNS entry? Thanks.

Regards,

Pete

---

From: Colin Perkins <[email-masked]>
Date: Wed, 11 Dec 2002 08:52:02 -0500

Hi,

>address of the RTCP packet (and associated RTP packets) have to match the

RTP does not require the client to have a DNS entry, since the numeric
address can be used in the CNAME instead. Also, receivers cannot assume
that the source address of an RTCP packet matches the address in the CNAME
since the RTCP packet may have passed through an application level gateway.

Colin
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