Subject: multiple routers in ZC? (was: Re: draft-ietf-zeroconf-reqts-08.txt)

From: Erik Guttman <[email-masked]>
Date: Fri, 13 Jul 2001 11:37:34 +0200 (MET DST)

> > draft-ietf-zeroconf-reqts-08.txt:
> > >    - MUST have unique IP subnets within an internetwork
> > >      (only for the internetwork scenario).

> "Thomas Narten" <[email-masked]> wrote: 
> > Do you need to scope this more? I.e., can't an "internetwork" consist
> > of the entire Internet (per the earlier definition?)

Aidan William <[email-masked]> replied:
> Perhaps "internetwork" should be a "zeroconf internetwork" in this
> section, where a "zeroconf internetwork" is the bunch of subnets
> connected to exactly one router.

The text above is sufficiently general that it leaves room for multiple
router zeroconf interface autoconfiguration to be standardized in the 
future.  

We did not preclude multiple routers from our charter because we thought 
it was a bad idea.  Rather, we did not think we could standardize 
multi-router zeroconf protocols in a timely manner.  The requirements 
document does not need to echo our charter humility, restricting future 
(perhaps immanent) standardization efforts. 

> Zeroconfiguration of a single subnet, and zeroconfiguration of a set
> of subnets hanging off a single router should be allowed for (as per
> the charter). 

It is allowed for.

> Communication with the global internet should not be
> precluded, and seems to be largely a matter of obtaining a default
> route, and a working DNS.

I do not believe stateless addrconf of global IPv4 addresses will ever 
be standardized.  Stateful addrconf (DHCP) for IPv4 is the mechanism
by which devices can obtain dynamic configuration and communicate with
the global internet.

There are interesting questions which we do not address, and should
not in the requirements document.  These are questions we could take
up in the ZEROCONF WG, if we were to expand on our charter:  

 - What do you do on a network with multiple routers but no administration?
   Such a network would not necessarily be zeroconf from the hosts'
   perspective, but could be from the routers'.
 - Should there be some standard way to attach a mini-dhcp to a configured
   network and 'inject' global configuration?  (see figure below).

           zero-admin network
          ----------[mini-DHCP]    ->  --------[DHCP]------<administered>
                     local-conf              global-conf       network

> > Indeed, I'm a bit confused about whether this document assumes
> > multiple subnets are present. It seems to, but I thought the WG
> > decided that a single router was assumed. It would be good to state up
> > front what the assumptions are for the enivironment zeroconf is
> > operating in. Will there be just one router? Or multiple routers? Or
> > no routers?

Why do we have to make that decision?  As long as the requirements
fit those different cases, aren't we OK?  Clearly we want to support
zero routers.  One router is an important case, where we have very
different link layers (802, firewire, PPP) tied together, each link
of which configured by a mini-DHCP server.  These links could all use 
mDNS, SLP, ZMAAP, etc.

Erik