Internet Backbone Index

Sun Jul 13 23:44:06 UTC 1997

On Sun, Jul 13, 1997 at 03:08:00PM -0800, Randy Bush wrote:
> There is one significant difference between routed and switched backbones.
> The hops on routed backbones can be seen by end users using tools such as
> traceroute.  On switched backbones, the hops are still there, but can not be
> seen by end users.  Hence the marketing perception is different though the
> results are really the same.

Actually, from the IP packet's standpoint, no, the results aren't
necessarily the same.  It's unlikely, but possible, that a switched
mesh backbone could forward some packets that a routed one couldn't,
due to TTL issues.  

Didn't some older kernels set rediculously low TTLs on IP packets?

> The router side could turn the argument.  "With a routed backbone, you can
> actually SEE what is happening to your packets.  It is not a hidden unknown,
> thus prone to failure you can not diagnose.  With routers you know it went
> bad at nqu1.  With switches, it just went bad."

It's a problem I'd accept for this amount of debugging flexibility,
though.

Cheers,
-- jra
-- 
Jay R. Ashworth                                                jra at baylink.com
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