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

More DNS is better:

     3. DHCP provides no mechanism for a client to request configuration
        options without also requesting address lease renewal.  Lease
        renewal would be a highly undesirable side-effect of service
        discovery.

     4. Service discover is often initiated by applications (rather than
        by the IP stack).  DNS is an application-level, request-response,
        protocol that is supported by established APIs.  DHCP, on the other
        hand, is an integral part of the IP stack -- DHCP implementations
        that I know of don't provide an API.

     5. DHCP client requests (DHCPREQUEST) must be subnet-broadcast and
        perhaps relayed, while DNS queries are unicast.

I have to agree that DNS SRV doesn't address topology-based server
assignment.

-- CCP

-----Original Message-----
From: Ted Lemon [mailto:Ted.Lemon@nominum.com]
Sent: Tuesday, July 16, 2002 3:21 AM
To: Stuart Cheshire
Cc: DHCP discussion list
Subject: Re: [dhcwg] Review of Service-Discovery-Type options in DHCP

What you propose is perfectly workable, but I don't see how it's *better* 
than what DHCP already provides.   That is, we have something that works 
now.   Why is the DNS a better choice as a resource discovery server?   I 
can think of some reasons, but I'm not sure why you think this makes sense,
  so I'm grasping at straws a bit - the reasons I can think of in favor of 
DNS are ones you have stated, and I don't have a real problem with them, 
but I don't find them particularly compelling either.

DNS is better:

     1. I already have to have a DNS server.   With IPv6,
        I don't have to have a DHCP server.   So this is
        one less thing I have to configure/deploy.
     2. DNS servers understand administrative domains,
        and administrative domains are a good way to
        determine which clients should use which servers.

DHCP is better:

     1. DHCP already solves the problem of locating services,
        so we don't have to kludge something into the DNS
        namespace.
     2. DHCP servers understand the network topology, and
        topology is a good way to determine which clients
        should use which servers.
     3. You have to have a DHCP server anyway - how are you
        going to get the IP address of your DNS server?

Arguments (1) are true, although I don't find argument 1 for DNS 
particularly compelling.   The other arguments aren't true - they're just 
opinions, and not necessarily even particularly valid opinions.   My 
feeling here is that using DNS as a server location protocol is chancy at 
best, and so I don't want to switch from DHCP to DNS, but I can't prove 
that I'm right on this.

Can you come up with a really compelling argument for using one over the 
other?

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