Zeroconf: A Net Admin’s Work is Still Never Done

Printers and other network devices that configure themselves so you
don’t have to – that’s the promise of zero configuration networking
(zeroconf), a set of standard protocols being developed by the Zeroconf
Working Group
of the Internet Engineering
Taskforce (IETF.) And you have to admit, the concept does have a great
deal of appeal – running and managing a corporate network is hard work,
and eliminating tedious configuration tasks would certainly make the job
a little bit easier.

But before you get too excited, it’s worth bearing in mind that,
unlike the auto-configuration capabilities built in to IPv6, zeroconf is
designed for home offices and small company LANs. If you administer a
big corporate network then Zeroconf isn’t going to change you life –
the best you can hope for is that the branch office on the other side of
town will be able to add a printer to its LAN without you or one of your
staff having to go and configure it.


“In theory auto configuration sounds good, but would
you really want to allow it anywhere in your corporation?”

“The idea of zeroconf is that it will simplify enterprise
configuration,” says Erik Guttman, chairman of the Zeroconf Working
Group. “Enterprise network administrators want to control what servers
are where and what they do, but the management of local resources is
tedious. It would be much easier if it was possible to delegate
printers, CD burners and other devices to the local area. So for my
department, I could deploy and control a printer, and everyone could
find it, and it wouldn’t have to be supported by enterprise
administrators.”

The flip side of this, of course, is that the local branch won’t have
to abide by enterprise-wide IT policies anymore, and before you know it,
it could be adding all sorts of equipment from all sorts of vendors
without your say so. But before getting into that, let’s take a look at
how zero configuration networking works.

Essentially, it’s made up of three components needed to get IP
networking going by itself: IP addressing, name resolution, and service
discovery.

Normally, a DHCP server co-ordinates the automatic allocation of IP
addresses to new devices attached to a network, but the Zeroconf Working
Group has devised a standard scheme enabling a host to automatically
configure an interface, without a DHCP server, with an IPv4 address in
the 169.254/16 range that is valid for Link-Local communication on that
interface.

Many applications also assume the existence of a name server, but
clearly on a LAN this will not always be the case. The protocol to make
each host on a LAN its own DNS server is actually quite trivial, and
Link Local Name Resolution is proven and mature.

The final part of the jigsaw is service discovery – the protocol
which enables computers to find the printers or other devices that are
available on the Link Local network. Various proprietary protocols,
like Apple’s Rendezvous and Microsoft’s uPnP, exist already to carry out
this function, although there is as yet no zeroconf-developed standard
solution.

There are a number of problems with zero configuration networking
that everyone should be aware of. The main foreseeable problem is that
if you make something simple so anyone can use it there are bound to be
difficulties when things don’t go according to plan.

“One of the big questions yet to be answered is how to handle network
boundaries,” says Erik Guttman, chairman of the Zeroconf Working Group.
“You could have a user with an autoconfiguring laptop which he uses in
the office on a wireless network, but when he takes it to a conference
it won’t work on the conference’s network and the user won’t know why.
Or if he does get connected to the corporate network, he won’t be able
to see the printer on his own desk. What it comes down to is when you
bring up the WAN, you can’t use the LAN, and vice versa.”

Another problem is the age-old one of proprietary solutions emerging
– while vendors wait for standards to be developed – which don’t
interoperate. The Zeroconf Working Group has been working for over four
years, and there is a danger that if the standards don’t emerge very
soon there will be such a proliferation of non-compatible equipment and
protocols that using zeroconf becomes impractical. “The large vendors
like HP, Apple and IBM are really starting to develop their
configuration capabilities,” says Stephen Elliot, senior analyst at
Framingham, MA-based research house IDC. “A bar to the adoption of
zeroconf would be all these legacy investments, because Apple’s
Rendezvous, for example, won’t be compatible with whatever emerges as
the zeroconf standard.”

The biggest barrier to widespread zeroconf adoption, however, is
probably human: most network managers will be very unwilling to let
unskilled users take control of a branch office LAN. “In theory zeroconf
is interesting, but I don’t know whether IT departments truly want it. I
think many will turn around and say ‘actually this is how we manage
branch offices remotely and we are not going to change,'” Elliot says.
It’s easy to understand why: not having to go and configure a printer
at a branch office may make your job a little easer, but is it worth it
if the price is allowing branches the automomy to do a lot more of what
they want – but without necessarily having the skills to ensure it is
all implemented properly? And guess who is going to have to sort out the
problems when auto-configuring hardware doesn’t work as expected, or
when it suddenly brings the branch LAN to its knees, or starts effecting
WAN connectivity? In theory auto configuration sounds good, but would
you really want to allow it anywhere in your corporation?

The question is a theoretical one at the moment, as the full
zeroconfig standards aren’t likely to be finished and available for
mainstream use any time in the next 18 months or so. For now, at least,
configuration remains a dull but necessary part of the every day life of
the network administrator. Go configure.

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