Re: [dhcwg] DHCPv6 Client address prefix

[Ted Lemon <Ted.Lemon at nominum.com>]

On Sep 9, 2008, at 3:38 PM, David W. Hankins wrote:
> On Thu, Aug 21, 2008 at 08:11:11PM -0700, Ted Lemon wrote:
>> For my own part I don't really see the point of using anything but a
>> link-local address on a routerless subnet.   So whatever the spec  
>> says, I
>> think this is a bit of a moot point.
>>
>> Do y'all see some reason why a link-local address wouldn't do the  
>> job in
>> this situation?
>
> Link-local addresses are not comfortable in DNS zones without playing
> dirty tricks, and it might not be clear to an application at that
> layer which interface the link local address is applicable to.

This is an easy problem for an IPv6 stack to solve - if the host isn't  
in your routing table, you do neighbor discovery to find it.   A link- 
local address should always be discoverable; if it is not, it is not  
reachable.

> The hosts are not necessarily "off net" beacuse they may have multiple
> interfaces, or multiple virtual points of attachment.

Okay, sure, but the particular network interface we are talking about  
is off-net, isn't it?

> RFC4193 addresses are more likely to be used in this scenario than
> link-local addresses.

I've never seen one of these in the wild, so I'm skeptical of your  
theory.   In practice, hosts get link-local addresses, and the RFC  
you're referring to seems to be talking about something that would  
happen on a wire with a router, not on a wire without one.


> In addition, there's the case where the network is online and running,
> but the router is offline for the time being.  In this situation, the
> client becomes dependent upon the router(s) in order to be able to
> talk with the rest of the (working) network, which violates the law of
> least astonishment for the user.

This seems like a somewhat contrived scenario.   How likely is it that  
a user would have time to become astonished before the router came  
back?   Wouldn't they notice other problems as well, problems that  
would lead them to try to take some action to fix the router?   Why is  
a routed IPv6 network without its router?

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