Subject: Re: [VRRP] newbie vrrp question

From: "M. T. Hollinger" <[email-masked]>
Date: Tue, 11 Nov 2003 15:55:03 -0500

On October 22, 2003, Bob Hinden wrote:
> The reason for not accepting packets addressed to the IP address of the
> owner, if not the owner, is to make it easier to detect that one of the
> routers is down.  People have had problems with other redundancy protocols
> that did not have the behavior that their network management systems would
> not detect that one of the routers had failed because the IP address still
> responded to pings, SNMP queries, etc.  It is also confusing for routing
> protocols.  The desired behavior when one of the routers fails is to have
> user traffic keep flowing, but to have all network management bells start
> ringing.

Please, think of the poor end-user!  I know that when I visit a new network
(such as the flaky wireless LAN here at the IETF), and I am having trouble
communicating, one of the first things I do is try to PING the default
router.  If the default router doesn't respond to PINGs, I will assume it is
down and either report the problem to local network management folks or give
up on connecting and just try later.

Some hosts may use ICMP ECHO_REQUEST messages in the context of a network
troubleshooting wizard, essentially automating the same interactive
procedure I use to figure out whether my network connection is any good.

Although as you know, I like the idea of making router failure visible to
interested hosts, having the Backup Router not respond to PINGs is not a
good way to provide such visibility.  Surely, we can find some way to let
VRRP-aware network management stations detect and report failures without
causing the router to appear dead to non-VRRP-aware troubleshooting
procedures.  I disagree with that provision of the current VRRPv3 draft and
suggest that it be removed.

            - Mark

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From: "M. T. Hollinger" <[email-masked]>
Date: Wed, 12 Nov 2003 00:11:53 -0500

Hi, Don.  Thanks for the response!

> Does the end user want to detect whether he has outside
> connectivity? Then he pings something outside to see if
> he has outside connectivity.

Sure, but what?  For the first 10 years I was out of college, I always used
to ping one of the servers back at school.  I couldn't ping any of the
systems at work from out on the open Internet because of our firewall, and I
wanted to ping something whose IP address I had memorized in order to take
DNS out of the equation (troubleshoot one thing at a time).

An automated diagnostic tool might do the same: try pinging a few hard-coded
addresses out on the net.  But if you just want to find out how well your
local link (e.g. wireless) is working, it's hard to match a quick 10-packet
ping of the default router to get statistics on loss and latency.

> So I think it's a case where you decide whether to continue
> to support what the end user learned to do back when he had
> one rickety router that failed all the time, or do you move
> on into the brave new world and let him discover new techniques.

Well, I think that depends.on how widely deployed VRRP becomes.  If VRRPv3
retains this behavior and becomes ubiquitous, then users (and automated
wizards) will eventually develop new techniques.  If VRRP remains a relative
rarity, then users (especially mobile users) won't learn.  When they visit a
network that does use VRRP, and a Backup Router happens to be active,
they'll think the network is really flaky.

            - M

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From: "Don Provan" <[email-masked]>
Date: Tue, 11 Nov 2003 18:04:13 -0800

Does the end user want to detect that his router is down?
Then he pings the address and that tells him whether his
router is down.

VRRP is just providing one more way in which the two are
different and, in particular, where a failure of the
router does not mean loss of connectivity.

So I think it's a case where you decide whether to continue
to support what the end user learned to do back when he had
one rickety router that failed all the time, or do you move
on into the brave new world and let him discover new techniques.
Personally, I don't particularly care which path is taken,
but it appears the decision was to proceed along the second.

-don

> -----Original Message-----
> From: [email-masked] [mailto:[email-masked]]On
> Behalf Of M. T.
> Hollinger
> Sent: Tuesday, November 11, 2003 12:55 PM
> To: [email-masked]
> Subject: Re: [VRRP] newbie vrrp question
>
>

---

From: Dmitry Golubev <[email-masked]>
Date: Thu, 13 Nov 2003 21:44:52 +0200

Hello, 

from the draft (in RFC there is, I think, the exact wording?):

IP Address Owner       The VRRP router that has the virtual router's
            		            IP address(es) as real interface address(es).
               		           This is the router that, when up, will respond
                 		    to packets addressed to one of these IP
                    		   addresses for ICMP pings, TCP connections,
                      		   etc.

From this may appear misunderstanding (or maybe it is not a
misunderstanding, but the way it actual should work????) that
IP address owner is not required to have ALL the IP addresses
of the VR, and, furthermore, that there might be more than one
owners in the VR. Further in the text it is, of course, it becomes
clear, that this is really my misunderstanding (although there is
no single place where it is said directly).

So I think the word "all" should be added in the definition to
eliminate the possibility of such misunderstanding:
...router that has all the virtual router's...

Also I think that the wording "...to one of these..." need to be
replaced to "...to any of these..." as I cannot imagine any other
need of having an IP address except for "ICMP pings, TCP
connections, etc."

Dmitry