Subject: RE: Comments to date on "IPv6 Host to Router Load Sharing"

From: Pekka Savola <[email-masked]>
Date: Fri, 1 Feb 2002 08:16:30 +0200 (EET)

On Thu, 31 Jan 2002, Bob Hinden wrote:
> Another approach is add text to make it clear that when there are multiple 
> administrative domains involved that the preferences can only be compared 
> it they are being set in the same manner.  I don't think there is any 
> simple automatic way of doing this (and I think we would want to avoid some 
> sort of policy certificates....).
> 
> This is probably another reason why only a few preference values are needed.

Well, it would be possible chop off a few more reserved bits (e.g. 2), and 
make this "domain of applicability" preference: two preferences would only 
be valid inside the same "domain" class.

But this relies on the advertising parties making this right.. and 
otherwise sounds like a bad (==unnecessary) idea too.

-- 
Pekka Savola                 "Tell me of difficulties surmounted,
Netcore Oy                   not those you stumble over and fall"
Systems. Networks. Security.  -- Robert Jordan: A Crown of Swords

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From: "Hesham Soliman (ERA)" <[email-masked]>
Date: Tue, 5 Feb 2002 11:14:56 +0100

Can't find Bob's original email !
So I'll respond to this part.

  > > it they are being set in the same manner.  

=> In theory that is feasible, but let's 
consider the basic problem: One domain is 
advertising to one or more hosts. The router 
has no clue which other domains this host is 
connected to. So (especially on shared media)
there is no way that a generic RA can do this. 
Unless the RA includes all domain identities
that it has agreements with... just too hard. 
I can't imagine domain admins organising meetings
to decide on how they would set the preference
values :) 

I think we should just add text to say that 
this value can not be compared when received
from different administrative domains.

I don't think 
  > there is any 

=> Agreed.

  > > This is probably another reason why only a few preference 

=> The only difference I see between having a small
range of values vs a large range is that a large
range would give better granularity. 

Either way, the draft should really give some 
rough guidlines on what each preference means. 
Even if they're not used across different domains.

  > otherwise sounds like a bad (==unnecessary) idea too.

=> eeehh, yeah I agree it's unnecessay. 
For hosts to decide to route their traffic through
a different domain or do some load balancing
we need a lot more than what the draft currently
specifies, just KISS. 

Hesham

PS: I'm obviously thinking of a mobile host 
that might have several differnt flows and 
would like to route these flows through the 
right access, depending on the characteristics
of this access. This draft is more relevant
to a dedicated server (e.g. HTTP) that needs to 
load balance traffic between two links.
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From: "Hesham Soliman (ERA)" <[email-masked]>
Date: Tue, 5 Feb 2002 11:14:56 +0100

I don't think 

=> Agreed.

Hesham

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From: Francis Dupont <[email-masked]>
Date: Tue, 22 Jan 2002 15:55:26 +0100

In your previous mail you wrote:

   1) Requirement level of SHOULD would make existing implementations 
   non-compliant.
   
   2) Relationship of this change to Neighbor Discovery and Default Router 
   Preferences draft.  Should they be combined?
   
=> what we asked is not really a combinaison, it was to get the
default router preference not after the load sharing.

   The Default Router Preferences draft is an optional mechanism (see
   the draft). It may not always be used and/or implemented.

=> I'd like to see the same argument than in (1) applied to the default
router preferences!

   Note this draft is not replacing the router preferences draft.  Both are 
   expected to go forward.  This draft only changes the case when there is 
   more than one default routers.  It does not provide the optimum solution 
   when there are multiple routers with different characteristics.  That case 
   is covered by the router preferences draft.
   
=> you know what we'd (people who did comments) like: to get both.

   3) General statement load-distribution is not predictable behavior and is 
   undesirable (e.g., using a single router until it fails is better).
   
   There is considerable current practice that disputes this.

=> there are situations where load sharing is better and others where it
is a disaster. The only good solution is to get load-sharing with a way
to control it, i.e. the default router preferences.
I sent in July 1995 a mail about default router preferences, I never
changed my opinion about this...

Regards

[email-masked]