[Freeswitch-users] Hostname vs IP in SDP

Steven Ayre steveayre at gmail.com
Thu Aug 4 14:59:51 MSD 2016

RFC4566 5. SDP Specification
"A session description can contain domain names in the "o=", "u=", "e=",
"c=", and "a=" lines."

It's a detail I'd expect some implementations may have skipped over though
so I'd expect it could lead to interop issues. Also you need to assume it
will resolve to the IP you expect, not necessarily the case if it resolves
to multiple IPs for example or it has changed and the TTL has not expired
yet. And it might not play well with SIP ALGs. I'd avoid it. That's not
evidence based, purely gut instinct.

On 3 August 2016 at 06:10, Michael Jerris <mike at jerris.com> wrote:

> I have not once in my life seen someone use a hostname instead of an ip in
> an sdp, and I do not believe it is legal.
> > On Aug 2, 2016, at 1:00 PM, Colin Morelli <colin.morelli at gmail.com>
> wrote:
> >
> > Hey all,
> >
> > So it looks like WebRTC has issues dealing with hostnames in the SDP
> instead of IP addresses. Particularly, when including a hostname in the SDP
> there's no audio in either direction. This is the case in both the latest
> Firefox + Chrome browsers.
> >
> > This is particularly problematic for applications that are WebRTC +
> mobile, now that Apple is enforcing applications to support IPv6-only
> networks. Using hostnames in the record-route and SDP addresses meets the
> requirement since the OS will synthesize an IPv6 address when a DNS query
> is performed, but according to the documentation they strongly urge
> applications to avoid using address literals in their applications.
> >
> > Has anyone had success with methods to switch between advertising a
> hostname vs IP address in the SDP? Or other methods for solving this
> problem?
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