Subject: Re: default router selection based on network topology

From: JINMEI Tatuya / 神明達哉<[email-masked]>
Date: Fri, 15 Dec 2000 03:53:37 +0900

>>>>> On Fri, 17 Nov 2000 14:28:31 +0900, 
>>>>> JINMEI Tatuya <[email-masked]> said:

>>> i'm still having fuzzy feeling about ICMPv6 redirects - if we have
>>> famous web server in our network, and the web server picked
>>> wrong (downstream) router as its default router, i'm not sure if
>>> the amount of ICMPv6 redirects will be acceptable for us.

>> I don't have any data to say how much it will be in such a case.
>> The worst case is clearly something that exchanges exactly one packet
>> with every IPv6 address on the planet where you'll see one redirect
>> per sent IP packet. A web server typically sends a lot more than
>> one IP packet per destination. But as I said I don't have any hard data
>> here.

> So, how about letting all routers in the segment where our "famous"
> web server is located advertise RA, and checking the ratio of outgoing
> TCP (or IP6) packets to incoming redirects on the server?

(Maybe no one remembered the context...)

I've taken some statistics on www.kame.net, which should be one of
famous IPv6 web servers, for two weeks. The network topology is as
follows:

      to the 6bone
          |
        router1
          |
|---+-----+-------+--|
    |             |
  www.kame.net  router2
                  |
              (leaf segment) 
 
I configured both two routers so that redirection always happened when
the web server sent packets toward the 6bone. The web server is based
on FreeBSD 2.2.8, which keeps a host route for redirection at least
one hour.

Here are the results:

number of incoming redirects: 24,779
number of outgoing IPv6 packets: 1,020,239
number of outgoing TCP/IPv6 packets: 334,724
number of established TCP connections: 3863
---
(rough) average of outgoing TCP packets per connection: 86.6
ratio of incoming redirects to outgoing IPv6 packets: 2.4%
(rough) ratio of incoming redirects to outgoing TCP packets: 7.4%

I'm not sure whether the ratio is high or low at this moment, though.

					JINMEI, Tatuya
					Communication Platform Lab.
					Corporate R&D Center, Toshiba Corp.
					[email-masked]
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