Re: administrivia (on avoiding injury)

[Thomas Narten <narten@raleigh.ibm.com>]

Jim Bound <seamus@bit-net.com> writes:

> > Well, if there are multiple hosts on a local net who are using those
> > addresses for communications among themselves, I have some real concerns
> > about sending them messages to cease such communications. The routers
> > may not be a party to all conversations, after all.

> Just as note.  The addconf spec prohibits sending rtr advs with lifetimes
> less than 2 hours for valid lifetime.  This was to prevent DOS on the
> link.  So the app has time to use new address that are not involved with
> multihoming for 2 hours.

Clarification: Lifetimes of less than 2 hours _in the absence of
proper authentication_ are ignored in some circumstances (e.g., a
router can't just drop the lifetime from (say) 1 day to 0 or 3 or 20
minutes). Authenticated RAs can reset the Lifetimes to any value.

This authentication step was added after it was pointed out that any
node (e.g. an intruder on a wirless link) could send out a bogus RA
telling all nodes on the link to invalidate its addresses, a rather
catastrophic result. That was deemed to large a DOS vulnerability to
leave in place.

Thomas