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

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

Hi Jari,

I hope this is a helpful response...

Jari Arkko wrote:
[description snipped]
>>
>> There is currently a BoF proposed for IETF57 which
>> aims to discuss issues uncovered in DHC, Mobile-IP
>> and Zeroconf WGs.  The hope is that getting together
>> people from these (and other) groups who are interested
>> in the problems may lead to a unified approach
>> to these problems (or at least only one approach each
>> for IPv4 and IPv6).
> 
> 
> I suspect v4 md and v6 md are parallel, mostly independent
> processes. There might be some joint probing and l2 assist
> going on, though. In any case, a roaming DHCP user should
> be able to use md such that he gets either v4, v6, or both
> depending on availability.

I think that there are significant differences between
what can be expected upon arrival on a link in IPv4 and IPv6,
so I think you are correct in the parallelism.

Certainly initiation of DHC (or use of DHC mechanisms to
confirm attachment to a new net) is valid in some v6
domains.  It is probably part of the primary detection
mechanism for v4 devices though.

Whether this needs standardization work in a separate
group (than DHC) certainly needs to be discussed.

>> Here is the proposed BoF's description:
>>
>>
>> Detecting Network Attachment (DNA) Proposed BoF Description:
>>
>> Network Attachment occurs when a host arrives on a new
>> IP subnet.  When attaching to a network, a host either
>> already has a valid configuration for this subnet or
>> must configure addresses.  A host determines whether
>> it requires additional configuration by Detecting Network
>> Attachment.
>>
>> When a host has existing upper layer protocols sessions,
>> it is important to receive a timely indication that
>> attachment has occurred.  This may be the case if a host
>> is connected intermittently, is moving or has urgent data
>> to transmit upon attachment to a link.
>>
>> For these nodes, it is also important detect if an acquired
>> link is new, or has already been visited. This information
>> may be used to distinguish between events where
>> configuration must be initiated, or a host already has
>> valid configuration.
> 
> 
> Interesting... For example, an address we used a while
> ago on this link could be reused? Would DAD still
> need to be run, or can we avoid that if we did it on the
> first time we arrived at that link?

I think that things are more straightforward in IPv4
than in IPv6.  There is a chance that someone can
configure your address while your node is away with
IPv4 manually, but little chance otherwise (within
the lease lifetime).

In IPv6, one of the goals is to determine that the host
has indeed attached to the same network which it
has now got configured.  It may be necessary to define
how long you can be away from a network before
additional configuration checks like DAD are
required though (< 1 second is ok ??).

I think that the task of actual configration may be
outside the scope of the work (since that is covered
by stateless address autoconfiguration).
Do people think that it is important to look at this?

>> This meeting hopes to providing a forum for those
>> interested in developing generic attachment detection
>> technologies for IPv4 and IPv6.
>>
>> The BOF aims to:
>>
>> * 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).

If you think that we should advertise on that list,
that is certainly possible.

> 
>> * Define the problem scope, and environments where network
>>   attachment detection is desirable.
> 
> 
> Scope has to be defined. Can you give an example of
> what "environment" would mean in this case? Some properties
> of link layers perhaps?

Yes, but I may have to have a think about it :)

I'll try to follow this up today.

>> * Determine if sufficient interest exists to form a
>>   Working Group on this topic.
> 
> 
> Ok.
> 
>> * Reach consensus on the area of work for a potential WG,
>>   including which problems are outside scope.
> 
> 
> This is the interesting question.

Indeed.

Thanks for your comments,

Greg