[Olsr-users] Sticky gateway

[Henning Rogge]

Am Friday 23 January 2009 01:09:15 schrieb Juliusz Chroboczek:
> > Your example is right in theory, but it's wrong in practice.
>
> I'm not quite sure what to make of this statement.  I've been brought up to
> believe that either theory and practice agree, or the theory is wrong.
Your theory is talking about links with absolute stable ETX values. So your 
theory is wrong for WLAN networks.

> > Our link quality values on a link are never total stable because of the
> > ETX metric we use. Most times they go up and down by 0.1 or more.
>
> Except on wired networks.  You do use cables and/or tunnels, right?
Yes, but I don't think there are any users that are connected ONLY with 
ethernet to their uplink. And if there is an user like this he would never 
choose another uplink because ethernet is always better than multihop WLAN.

So the problem would only happen there is some kind of ethernet loop which has 
multiple connections to an HNA 0.0.0.0 uplink.

> > But we are talking about both problems (the possibility or routing loops
> > to the HNA 0 gateway AND the instable routing metrics) and I hope we will
> > get better solutions for this problems in the next 12 months (much to do,
> > not enough time to do it ;) ).
>
> I'm looking forward to seeing your solution.
After the workshop about the ipv4-to-ipv6 kernel module at CCC I talked with 
one of the programmers. We had the following idea to allow a stable gateway 
selection:

each gateway announce it's 0.0.0.0 IPv4 internet in an unique IPv6 address 
space.

example:
node 1:     ::1:ffff:0:0:0:0/96
node 2:     ::2:ffff:0:0:0:0/96

on the "client router" side the kernel plugin has a sysfs configuration which 
IPv6 address space is used to translate IPv4 into IPv6 traffic, so we can do 
some kind of source routing.

The clients announce the normal IPv6 translated IPv4 address as HNA, so the 
internet gateway does not need to know about namespace stuff.

> In the meantime, I think it'd be a good idea not to recommend the sticky
> gateway feature for general use.
Without the sticky gateway many people in larger networks (like Berlin) have 
gateway changes regularly, so each time all HTTP session will be killed.

Without sticky gateway we cannot solve this problem at the moment.

Henning

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