Measure overall network availability

Fri Jan 7 15:43:40 UTC 2005

On Fri, Jan 07, 2005 at 12:23:48PM +0800, Joe Shen wrote:
> 
> Hi,
> 
> is there any recommended method to measure overall
> network availability? 

The problem is, that most people have no definition when they
consider their network available. And without that definition it
seems impossible to monitor it.

In the end it all comes down to defining service
Levels which are acceptable. That might be as simple as defining how
long round trip times are allowed to be (is a link packets need 16seconds
to pass still available?) or as complicated as "is my network reachable
from at least 99.8% of the ASes on the internet". Some things are easy
to monitor, some are difficult, some are virtually impossible.

Is your network still available if packets reach your webserver really
fast from everywhere in the world, but the Firewall drops outgoing packets
with source port 80? Technically the network is there, but practically it
is unusable for many things. So availability might also be a value that is
useless in real life.

Nils