[rrg] Fundamental objections to a host-based scalable routing solution

[Christian Vogt]

Luigi Iannone wrote:

> symmetric traffic : is the same remark as Dino, i.e., unidirectional
> traffic.
> 
> symmetric routing: your data packet and your ack do not pass necessarily
> through the same LOCs (which limits the capacity of discover the broken
> link). Am I wrong?

Luigi and Dino:

The problem of asymmetric routing exists independently of whether you
probe explicitly, or implicitly using payload traffic.  Also, probing in
hosts (rather than in the network) does not make the problem harder.  In
fact, the problem gets harder if you probe in the network, because only
then do you potentially have to synchronize state over multiple boxes.

Regarding unidirectional traffic:  Yes, this requires explicit probing
into the silent direction.  And for host-based solutions, explicit
probing cannot easily be aggregated.  Having said this, I wouldn't take
it for granted that aggregation of probing traffic in network-based
solutions will in all situation yield a noticeable reduction in probing
traffic either.  The number of sessions between a given pair of networks
may be very small.

- Christian