Subject: RE: [dhcwg] Review of Service-Discovery-Type options in DHCP

From: "Bernie Volz (EUD)" <[email-masked]>
Date: Wed, 17 Jul 2002 06:51:11 -0500

Yes, but the presumes everyone wants to name their service/server the same
name.

The point of using DHCP is that you don't need to do that since either
the DNS name or IP address is provided. Of course, if DHCP isn't available
(or the option is configured in DHCP), you might be forced to use a
default service name.

Also, with a single DNS name, you have less control over what various
users use and are forced to use alternative solutions such as load
balancing.

- Bernie

-----Original Message-----
From: Ted Lemon [mailto:[email-masked]]
Sent: Wednesday, July 17, 2002 1:30 AM
To: Roop Mukherjee
Cc: Stuart Cheshire; DHCP discussion list
Subject: Re: [dhcwg] Review of Service-Discovery-Type options in DHCP

> It seems that the problem of service discovery, probably better termed as
> server discovery, at the moment is simply that of locating a server for a
> service that a end-node may desire. Locating the address of a server (for
> time, ftp etc.) is a naming function.
>
> That being the case, locating the names of servers seems more up the alley
> of DNS than DHCP.

This seems to be a statement of opinion.   I was looking more for logical 
arguments - that is, you present *reasons* why you believe that DNS is a 
better choice than DHCP.   I don't see any reasons here - just opinions.

I am not saying you are definitely wrong.  I just don't see how this 
statement helps us to decide what to do.

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---

From: Jitesh N Verma <[email-masked]>
Date: Wed, 17 Jul 2002 18:09:31 +0530 (IST)

Hi all,
	Around a year back, I had sent a mail to this mailing list citing 
that other working groups (like Stateless Autoconfiguration, DNS etc.)
are trying to hijack DHCP working group's agenda. Now, I am seeing that fear
becoming realty.
	I just want to raise one point against DNS implementing server location.
DNS name resolution is hitting perfomance bottleneck due to large size of 
database. Sometimes name resolution takes lot of time in larger administrative
domain. Customers are craving for better performance. I am sure the load on
DNS server will increase in future when number of computing nodes increase.
DNS guys are looking for ways to improve performance. Several schemes like
database cache, load-balancing have been used in DNS.
	My point is why to increase load to already overloaded DNS server
with extra features (which are already available in DHCP)? 

Cheers,
Jitesh

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From: David Conrad <[email-masked]>
Date: Wed, 17 Jul 2002 07:24:58 -0700

Jitesh,

> are trying to hijack DHCP working group's agenda. Now, I am seeing that fear

Lots of folks have hammers for all those things they think look like
nails... :-)

> database. 

No it isn't.  Particular implementations are hitting bottlenecks for various
reasons, however I know of a couple of implementations that can do wire
speed on 100 Mbps without breaking a sweat.  There is empirical evidence the
DNS scales to hundreds of millions of zones or tens of millions of names in
a zone while responding to tens of thousands of queries per second. I am
skeptical that any service location use of DNS would add significantly to
the scaling requirements.

However, if you want to talk about scaling, how many DHCP servers out there
can do more than (say) 30,000 lease allocations or even renewals per second?

> with extra features (which are already available in DHCP)?

DNS, in particular the SRV record, was specifically designed to provide
information on where to find a particular service.  Since SRV contains both
a priority and a preference field, I believe it can provide more flexibility
to clients attempting to locate a service than DHCP can.

In any event, I personally believe having multiple tools in a toolbox is a
good thing.  I can imagine scenarios in which either DHCP or DNS or SLP are
better suited to the service location function than the others.  Where it
would be wrong to go would be to twist the protocol to meet a particular
requirement that one of the other protocols already meets.

Rgds,
-drc