Subject: RE: VRRPv6?

From: "Smith, Mark" <[email-masked]>
Date: Tue, 9 Oct 2001 08:19:20 +0800

Well, there is a IPv6 draft which allows preference to be assigned between
multiple default routers :

http://www.ietf.org/internet-drafts/draft-ietf-ipngwg-router-selection-00.tx
t

If IPv6 Node Unreachable Discovery is as prompt as VRRP failover (ie around
< 3 seconds to discover a dead router), NUD with the above default router
preference would provide similar functionality to IPv4 VRRP, with the
difference being the mechanism is implemented in the hosts rather than the
routers.

I'm sure somebody on the ipng list could provide further clarification.

Regards,
Mark.

> -----Original Message-----
> From: Aron Silverton [mailto:[email-masked]]
> Sent: Saturday, 6 October 2001 4:28
> To: [email-masked]
> Subject: VRRPv6?
> 
> 
> Hello,
> 
> I've looked through some of the archives, and haven't found mention of
> IPv6 VRRP.  Can somebody update me on the status of that effort?
> 
> Thank you,
> 
> Aron
> -- 
> Aron J. Silverton
> Senior Research Engineer
> Motorola Labs, Networks and Infrastructure Research
> Motorola, Inc.
> 
> Telephone: (847) 576-8747    
> Fax:       (847) 576-3420
> Pager:     (800) 759-8888 PIN 1147344
> Email:     [email-masked]
> 
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---

From: Erik Nordmark <[email-masked]>
Date: Tue, 9 Oct 2001 14:41:45 +0200 (CEST)

> difference being the mechanism is implemented in the hosts rather than the

The default timers in NUD result in a failure detection in about 40 seconds
as I recall. There is the capability for the routers to advertise diffferent
ReachableTime and RetransTime (with the unit of milliseconds) so that in
theory the NUD failure detection could be as low as 5 seconds or so
	(ReachableTime + DELAY_FIRST_PROBE_TIME + 
	 (MAX_UNICAST_SOLICIT+1)*RetransTime)

However, there is an engineering tradeoff between using NUD vs. VRRP to detect
router failures. In order for NUD to detect failures on the order of N seconds
every node that is actively sending packets need to probe their neighbor more
often than every N seconds (this includes host to router probes, router to
host, and host to host). Thus with R routers and H hosts this traffic has
elements that depend on R*H as well as H*H (but if there is little
host-to-host traffic the latter part might not be that significant). Worst
case is clearly a probe traffic order H-squared.

Contrast with VRRP which, but virtue of only looking at router failures and
not host failures, can limit the probe traffic to be order R (or perhaps even
constant independent of the number of routers).

So NUD does a fine job of recovering from hosts changing their link-layer 
address and sooner or later detecting that a router is dead. But if the goal
is to quickly fail over between a set of routers then VRRP make more sense.

  Erik

---

From: "Brian Haberman" <[email-masked]>
Date: Tue, 09 Oct 2001 09:38:44 -0400

> is to quickly fail over between a set of routers then VRRP make more sense.

I agree with your assessment.  Having VRRP functionality accomplishes
more than simply depending on NUD.  However, the current VRRP spec
has no support whatsoever for IPv6.  In addition, there may be issues
that need to be addressed where VRRP, as defined for IPv4, causes
operational problems in IPv6 (DAD for instance).

Anyone in VRRP looking at VRRPv6???

Brian

---

From: Bob Hinden <[email-masked]>
Date: Tue, 09 Oct 2001 16:11:56 -0700

Brian,

>Anyone in VRRP looking at VRRPv6???

Other than some discussion, there hasn't been any work done on an IPv6 
version of VRRP.  It is within the scope of the VRRP w.g., so if there was 
sufficient interest (i.e., someone wanted to write a draft), it could be 
done there.  Also, there is still time to request a meeting slot for VRRP 
to meet in Salt Lake City.

Are you interested in working on this?  I have the nroff for the current 
version of VRRP.  I don't think it would be too hard to adapt it to IPv6.

Bob