Re: [LARTC] Solved: Using more than 1 Internet Line

From: Arthur van Leeuwen <arthurvl@sci.kun.nl>
To: lartc@vger.kernel.org
Subject: Re: [LARTC] Solved: Using more than 1 Internet Line
Date: Tue, 04 Dec 2001 16:20:49 +0000	[thread overview]
Message-ID: <marc-lartc-100748270425235@msgid-missing> (raw)
In-Reply-To: <marc-lartc-100742079800981@msgid-missing>

On Tue, 4 Dec 2001, Don Cohen wrote:

>  ...
>  > > dead. This is *very* cool on UDP, and will make UDP failover to another
>  > > route fully transparent.  However, it will not fix stateful protocols in
>  > > which the server on the other side keeps state on the IP address it was
>  > > talking to, such as SSH.
>
> Sending packets with the same source address out another link only
> helps UDP if it's not necessary to get replies, in which case I
> wouldn't call it a "connection".  If you didn't need the replies then
> you could do the same thing for TCP.

Ah, but the rerouting patch doesn't do that. It reroutes and *remasquerades*
packets going out. You will only lose return packets destined to the other
interface. The problem really only lies in the other end maintaining state
in the higher level protocol.

> This problem could be fixed by extending TCP (and of course, changing
> the kernel) to support multiple IP addresses.  I suggest a new option
> that says "here's another IP address for me" (or perhaps, here's an
> alternative IP/port).  The kernel then has to merge these two input
> streams.  On the output side (when you send to someone who has told
> you about alternative addresses) I can think of several ways to
> control which address you send to.  I suppose the application should
> have some way to influence that, but as a first stab, I suggest that
> whenever tcp has to resend a packet, it should move to the next
> address.

Ooh, that'd be cool. Building your own anycast group dynamically... and
registering on the other side as said anycast group. Unfortunately, IPv4
doesn't allow for IP anycasting. IPv6, anyone? :)

Oh, you're talking about implementing it at the TCP level? Right then...
right. That should be possible... if only programs couldn't bind to specific
addresses...

Doei, Arthur. (Note: the idea is one of the coolest I've seen in a while)

-- 
  /\    / |      arthurvl@sci.kun.nl      | Work like you don't need the money
 /__\  /  | A friend is someone with whom | Love like you have never been hurt
/    \/__ | you can dare to be yourself   | Dance like there's nobody watching

_______________________________________________
LARTC mailing list / LARTC@mailman.ds9a.nl
http://mailman.ds9a.nl/mailman/listinfo/lartc HOWTO: http://ds9a.nl/2.4Routing/