[jdev] [ANN] Google Talk engineering manager live chat

Richard Dobson richard at dobson-i.net
Fri Sep 23 02:55:58 CDT 2005

> I think this is simply something terribly broken about most XMPP
> implementations.

Im not convinced of this, personally I think the DNS situation is exactly as
it should be, lets use some examples of other situations.

Lets say a users email address is user at email.isp.com and no MX records or A
records are setup for email.isp.com, the email server will not try to lookup
isp.com to see if that is setup, why should it?, if it did it might actually
connect to something completely unrelated which is bad.

If a website is www.website.isp.com but the DNS is not setup a web browser
will not check www.isp.com to see if that exists, it will just assume that
as the DNS says "not found" that that is an invalid address, just as it
should IMO.

> Users don't think of MUC as "another server"

Whether users think it is or not doesnt really change the fact that it is
effectively another server, the physical setup of the software/hardware is
irrelivant the only thing that matters is that it has a different domain

> and the reality is that many people in large organizations don't have the
> ability to manage DNS or getting DNS changes is a huge burden that could
> lead them to another "SIMPLEr" (ha ha) IM system.

Maybe so, but someone in that organisation will have the ability, and the
difficulty in getting things added or modified is really an issue for that
organisation and the people implementing IM to resolve, if they wont allow
it to be added then there must be a reason for it (i.e. the people
installing IM for that domain havent been given permission to install it),
also the DNS admins should be the ones making the decisions as to what DNS
addresses the XMPP services should have so they have to be involved anyway,
also im unsure as to how using SIMPLE instead helps matters if they arnt
being allowed to setup DNS entries.

Sorry its just im finding this hard to understand why organisations arnt
allowing the setting up of appropriate DNS entries for their IM system if
the installation of that system has been authorised by the appropriate
people at that organisation, if its not been authorised then it shouldnt
really be being installed in the first place, and if its just an issue of
not being able to setup sub domains in their dns system then my suggestion
of just getting a new domain for the conference server (or whatever sub
server it is) will work fine, be inline with the standards and work fine
with all currently deployed implementations without any need for the
workaround you have implemented.

> If everybody implemented the same logic that we do in Jive Messenger, it
> seems like it would mostly solve the problem. Since we can't enforce
> that, we still recommend DNS entries and will continue to do careful
> testing to make sure that we work with all the other s2s implementations

Maybe so, but im not convinced the stated reasons for implementing this
workaround are enough, IMO the fact DNS says it doesnt exist should be
enough for servers to know its an invalid server address, this is how things
seem to work for practically every other internet protocol ive ever looked
into so I dont see why it should be different for XMPP.

Sorry im not trying to argue for the sake of it, I truely cannot see enough
of a reason for it could you provide some examples of when this has been an
real issue and what the reasons for it were? As the only reasons I can think
of are the following, along with a possible solution that is to the specs:

- Problem
Their dns provider doesnt support subdomains.
- Solution
Switch dns providers or register a new domain for the MUC server.

- Problem
Their companies dns admins refuse to add the entries.
- Potensial reasons
The people installing the IM service have not gained the appropriate
permission to setup the service.
The appropriate channels have not been followed.
The dns admins have not been consulted during deployment.
- Solutions
Get permission before deploying.
Go through the appropriate comapny channels in order to get it added.
Ensure admins are consulted with regards to dns entries to pick.

- Problem
Cant be bothered with the effort to get the appropriate dns entries
- Solution
Dont cut corners and go ahead and get the dns entries, must have had gone to
the effort to get the entries for the root domain in the first place anyway.

If you can provide some other reasons that I havent thought of please do, so
far I cant think of any without obvious solutions but im sure you must have
come across some others. Of course its up to you if you want to implement
these workarounds in your implementation, but if you want it to become a
standard it would be better to have some firmer reasons for doing so.

Now partly off topic, something which has come to mind to me is that if say
you have the following two SRV records:

_xmpp-server._tcp.example.com                s2s.example.com
_xmpp-server._tcp.muc.example.com        s2s.example.com

if the two SRV records point to the same server then it would be nice if you
are already connected to s2s.example.com for communication with example.com
then when you try to communicate with an address at muc.example.com it
negotiates it over the existing connection to s2s.example.com rather than
opening a new one.


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