[Freeswitch-users] Hostname vs IP in SDP

Colin Morelli colin.morelli at gmail.com
Thu Aug 4 16:25:15 MSD 2016


Hey Steven,

I did check that as well. So far as I can tell, most of the shared portions
of the SDP come from RFC 4566. The ICE additions in RFC 5245 also claim to
allow FQDNs for candidate addresses.

My assumption is that it's just not commonly used. But it seems much easier
to support hostnames everywhere as more and more dual stack endpoints.

Any thoughts on a per-channel advertised address?

Best,
Colin

On Thu, Aug 4, 2016 at 8:14 AM Steven Ayre <steveayre at gmail.com> wrote:

> Should point out that although it might be allowed in SDP's RFC that
> doesn't necessarily mean it isn't restricted by other WebRTC
> specifications. You'll probably want to look into those as well.
>
> On 4 August 2016 at 12:17, Colin Morelli <colin.morelli at gmail.com> wrote:
>
>> Steven,
>>
>> Thanks for the clarification - that's really helpful (it also means I can
>> go file browser bugs which I'll do)
>>
>> Agreed it'll cause interop issues (for example the ones seen in WebRTC).
>> It's too bad, because it could be helpful in a few different scenarios.
>>
>> That said, for now I'm just looking to slowly start using it on devices
>> that will have problems with IP addresses. Does anyone know if there's a
>> way, via a channel var, to set the advertised address in the SDP?
>>
>> Best,
>> Colin
>>
>> On Thu, Aug 4, 2016 at 7:03 AM Steven Ayre <steveayre at gmail.com> wrote:
>>
>>> 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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>>
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>
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