Re: SRV RRs support in Internet Explorer?

Tech-Archive recommends: Repair Windows Errors & Optimize Windows Performance

From: William Stacey (staceywREMOVE_at_mvps.org)
Date: 02/09/04 

Date: Mon, 9 Feb 2004 13:59:44 -0500

> 1. The first one, general in scope, is being able to define a backup site,
> and/or mirror sites with load sharing, for a particular resource.
> For this, using the (clean) DNS-SRV mechanism, seems an obvious idea.
> It would logically involve just a simple extension of IE whereby if it
> receives a "nonexistent domain" error code in an answer to an A or AAAA
> request for domain name xxx.yyy, then it would try the standard SRV
request
> for such a resource, i.e. _HTTP._TCP.xxx.yyy.

I see what your saying. However, you can do much of that today. If you
have 4 A records for the host name, then IE will try the first, second, etc.
The srv record approach does not really help here, cause in either case, you
still need to fall down to next host, which IE does today. Also, in the
case of http, dynamic ports would probably cause more issues then it fixes.
Port 80 is standard for general access. I can't think of a good reason to
change that or allow dynamic port changes. If you have 20 web servers, they
just listen on 80 - simple. I would not use srv records to get around
needing host headers either. Ports are valuable, I would not use them as an
alternative to host headers. I don't get the "nonexistent domain" reason.
If the name does not exist, then it was not setup for a reason and you don't
want another "solution" that somehow "finds" names that don't exist for a
reason. If I miss what your saying, please correct me as this is an
interesting idea. I just don't see the exact value from the text at this
point. The load balancing, IMO, is the real winner. DNS load balancing is
lacking. You can do round robin to get cheap LB, but we all know the issues
with that. That said, if you require real LB, you implement a LB
gateway/host that does that and/or use a LB dns like akadns does. I don't
see how srv records help here.

> 2. The second objective, more specific, and for a project of my own,
> involves using the DNS-SRV capability of dynamically indicating which TCP
> port has to be used on which host.

Any client app can use SRV records if they need or want. You get to decide
how and why to use them.

Please post back. Cheers. 

-- 
William Stacey, MVP

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