Re: [OSPF] OSPFv3 Autoconfiguration - draft-ietf-ospf-ospfv3-autoconfig-05.txt

So, I am one person who raised this concern to Acee - but the proposal outlined by Acee is not what I had in mind. There is no need to use "uptime" or to invent some unusual exchange of LSAs prior to Exchange state.

Also, in regards to Curtis's comment - it is not DOS attacks that I am trying to mitigate here. As he says if an attacker is in your network and able to originate credible packets no strategy is safe.

The motivating use case is to minimize disruption of a stable network when a new router is added or an existing router is replaced/rebooted. In other words non-disruptive handling of the common maintenance/upgrade scenarios.

What I have in mind is this:

1)A router needs a way to advertise that it has been up and running for a minimum length of time - for the sake of discussion let's say 20 minutes. Routers then fall into two categories:

  o Old routers (up >= minimum time)
  o New routers (up < minimum time)

2)When a duplicate router-id is detected, the first tie breaker is between old routers and new routers. The old router gets to keep its router-id and the new router picks a new router-id.
If both routers are "new" or both routers are "old" then we revert to the existing tie breakers defined in the document (link local address for directly connected routers and fingerprint info for non-neighbors).

3)Advertisement of the "old/new" state requires a single bit - but it has to be available both in hellos and the new AC-LSA. Adding it to the AC-LSA is easy to do. For hellos, there are two possibilities:

   o Use one of the Options Bits
   o Use LLS

Be interested in how folks feel about this.

   Les

> -----Original Message-----
> From: OSPF [mailto:ospf-bounces@ietf.org] On Behalf Of Acee Lindem
> Sent: Thursday, February 06, 2014 5:12 PM
> To: Curtis Villamizar
> Cc: OSPF List
> Subject: Re: [OSPF] OSPFv3 Autoconfiguration - draft-ietf-ospf-ospfv3-
> autoconfig-05.txt
> 
> Hi Curtis,
> I agree and believe the significance of this use case where a new router is
> inserted into an auto-configured domain has been greater exaggerated.
> Thanks,
> Acee
> On Feb 5, 2014, at 3:58 PM, Curtis Villamizar <curtis@ipv6.occnc.com> wrote:
> 
> >
> > In message <CF17DD4E.2696B%acee.lindem@ericsson.com>
> > Acee Lindem writes:
> >
> >> The OSPFv3 autoconfiguration draft was cloned and presented in the
> >> ISIS WG (http://www.ietf.org/id/draft-liu-isis-auto-conf-00.txt). In
> >> the ISIS WG, there was a concern that the resolution of a duplicate
> >> system ID did not include the amount of time the router was
> >> operational when determining which router would need to choose a new
> >> router ID. With additional complexity, we could incorporate router
> >> uptime into the resolution process. One way to do this would be to:
> >>
> >>     1. Add a Router Uptime TLV to the OSPFv3 AC-LSA. It would include
> >>        the uptime in seconds.
> >>
> >>     2. Use the Router Uptime TLV as the primary determinant in
> >>        deciding which router must choose a new OSPFv3 Router
> >>        ID. Router uptimes less than 3600 (MaxAge) seconds apart are
> >>        considered equal.
> >>
> >>     3. When an OSPFv3 Hello is received with a different link-local
> >>     	source address but a different router-id, unicast the OSPFv3
> >>     	AC-LSA to the neighbor so that OSPFv3 duplicate router
> >>     	resolution can proceed as in the case where it is received
> >>     	through the normal flooding process. This is somewhat of a
> >>     	hack as the we'd also need to accept OSPF Link State Updates
> >>     	from a neighbor that is not in Exchange State or greater.
> >>
> >> An alternative to #3 would be to use Link-Local Signaling (LLS) for
> >> signaling the contents of the OSPFv3 AC-LSA. However, you'd only want
> >> to send the Router-Uptime and Router Hardware Fingerprint when a
> >> duplicate Router-ID is detected. This requires implementing the
> >> resolution two ways but may be preferable since it doesn't require
> >> violating the flooding rules.
> >>
> >> In any case, I'd like to get other opinions as to whether this problem
> >> is worth solving.
> >>
> >> Thanks,
> >> Acee
> >
> >
> > Acee,
> >
> > If the basis for router-id on boot up results in a fixed value, and if
> > a duplicate will occur on a give network, then which of two duplicate
> > routers gets that value may change after one of them reboots.  If
> > uptime is not considered, it will never change as long as one router
> > stays up at any given time.
> >
> > We are talking about a very low probability event (a duplicate) except
> > if this is a DoS attack and then either using or not using uptime
> > won't matter since the attacker will claim an impossibly long uptime.
> >
> > Curtis
> 
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