Re: [DNA-BOF] Re: [mobile-ip] Announce: BoF Proposal: DetectingNetwork Attachment

[Greg Daley <greg.daley@eng.monash.edu.au>]

Hi Jari,

Jari Arkko wrote:
> Greg Daley wrote:
> 
>>>> * Describe existing issues encountered in DHC, ZEROCONF
>>>>   and Mobileip WGs, which could benefit from work on
>>>>   detecting network attachment.
>>>
>>>
>>> Hmm... I don't see IPv6 WG mentioned above. Does this imply that
>>> movement issues related to stateless autoconfiguration are
>>> out of scope, but stateful autoconfiguration is in?
>>
>>
>> I think that I was aiming at groups for which this is
>> strictly on-topic for a first advertisement (once again
>> aimed at the idea that the issue is not the actual
>> configuration, rather the assessment that config is required).
> 
> 
> (My question relates more to the scope of the work
> than the groups who got the advertisement for the
> BoF.)
> 
> I agree that the group should avoid looking at
> the configuration task itself. But still, aren't DHCPv4,
> DHCPv6, ZEROCONF, and ND all about configuration? Why
> is ND any different in this respect, particularly
> considering that ZEROCONF appears to do exactly what
> stateless addresss autoconfiguration does in ND. (I
> have to confess this is more or less my first exposure
> to ZEROCONF, so I'm probably missing something.)

I think that we're bound in some sense to make
use of deployed technology to achieve the detection.
In fact, the existing signalling and configuration
systems which are widely deployed are candidates
for use in network attachment detection (just because
they exist).

It's worth saying that I prefer not to undertake the
description of dynamic configuration in this BoF,
but the presence of ARP and DHCP on IP links can be used
to ensure contactability of devices on a particular
IP subnet (see Bernard's document).  Similar things
may not reliably be said for IPv4 Router Advertisements.

I don't see ND as different at all, although SAA has been
defined in a different document to ND.  This gives a
cleaner distinction between (address) configuration and
network identity.

> In practical terms, if you detect that you have
> moved, you'll have to redo DHCPv4 if you were doing
> that, redo ND stateless autoconfig and DAD if you were
> doing that, redo ZEROCONF if you were doing that, etc.
> In fact, you might have been doing DHCPv4 and now you
> have to go for ND-only. Or you might have been doing
> ND+DHCPv6 and now you have to do ND without DHCPv6.
> Also, the ND case is interesting in the sense that
> since it is not a single monolithic thing like DHCPv4,
> we might have to redo only parts of it.

I'm not sure myself (have not though much) about the
implications for DHCPv4, although I guess that the
changes would principally be in host interpretation
and transmission of messages.

Certainly the consequences of detecting that you have
joined a new IP subnet are clear:  (Re)configuration
based on that network's constraints.

What is not clear is if there needs to be a non-configuring
mechanism in IPv4 which will provide complete
detection of a new network.

v6 is safer, since we can attempt an RS in most cases.

Greg