tinc - May 2001 - Routing

Hello,
>From the docs, it seems that tinc handles routing itself. Do users need to 
add any routing entries for tunnels at all?

Here is sample scenario. There are six gateways A, B, C, D, E, and F 
connected using tinc. Each gateway is has a separate network attached to it 
and the connections are as follows:

E<-->F
^
|
v
A <--> B <--> C <--> D
^             +
|             |
+-------------+

A, B, C, D, E, and F represent 10.1.{1,2,3,4,5,and 6}.0/24 networks, 
respectively.

Here are my questions:

1. Will tinc handle routing in this case correctly since there is a loop?

2. Since A does not know about D, will tinc propagate routes for D to A?

3. In order to reach D, is tinc going to send packets to B or C (ACD is a 
shorter path).

4. What kind of algorithm does tinc use to propagate routing information? 
Distance vector or link-state maybe?

Thanks,
Oleg Kolesnikov

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On Thu, May 31, 2001 at 12:33:27PM -0000, digi =?ISO-8859-1?Q?=A0 ?= wrote:
> >From the docs, it seems that tinc handles routing itself. Do users need
to
> add any routing entries for tunnels at all?
tinc handles routing. You normally don't need to add any routing entries
except
for the standard route (which is automatically added by ifconfig).

[...]
> Here are my questions:
> 
> 1. Will tinc handle routing in this case correctly since there is a loop?
Yes, it will detect loops and remove them from the connectionlist. Tinc acts
like a simple routing daemon and will make sure the connections always satisfy
the tree property.
> 2. Since A does not know about D, will tinc propagate routes for D to A?
Yes.
> 3. In order to reach D, is tinc going to send packets to B or C (ACD is a 
> shorter path).
Although tinc will form a spanning tree for it's control channels, it will
propagate the real IP address of D to the rest of the network, so also to A.
When sending VPN packets, A will send them directly to D without going via B
and C or C alone. The assumption here is that allo nodes in the VPN have real,
reachable IP addresses on the Internet. If that is not the case, you have to
tell tinc that some hosts are not directly reachable, it will then route it via
B and C or C alone (depending on which tunnel it removed to prevent loops
ofcourse).
> 4. What kind of algorithm does tinc use to propagate routing information? 
> Distance vector or link-state maybe?
It's more like link-state. When a new node connects or an old one
disconnects
or is unreachable, information about the new/gone route is propagated using the
spanning tree that was there before that event. New nodes get information about
the rest of the VPN from the node it connects to.

There is no need for a distance vector algorithm; tinc sends packets to the
destination directly, so the packets take the best route on the underlying
physical network.

-- 
Met vriendelijke groet / with kind regards,
  Guus Sliepen <guus@sliepen.warande.net>
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