🚀 go-pugleaf

In article <199703022320.XAA02670@mauve.demon.co.uk>
           root@mauve.demon.co.uk "Ian Stirling" writes:

> Derek Scott (derek@teri-odin.demon.co.uk) wrote:
> 
> : WS_Ping is a nice utulity that will not only ping a site but
> : TRACE-ROUTE it too, listing the time taken from one stage in the
> : packet's journey to the next router.
> 
> Strictly, it can't do this, it can only time how long packets from
> each router take to return to you.
> This may also be affected by other factors, such as some routers
> will drop the ICMP packets used for this, or at least slow them.

The way route-tracing works is quite sneaky and hackerish.  One of the 
features of the protocols is a limit to the number of hops a packet can 
be sent over (necessary in case, as sometimes happens, routing sets up 
an infinite loop), and the protocols also require a warning message that 
this has happened (also useful when loops appear).

So a packet is sent out with a time-to-live of 1, and gets stopped, and 
the warning comes back, and the program measures the time.

One factor not mentioned above is that there is no guarantee that the 
return route is the same.  So a bad response time from one site could be 
a consequence of a route from that site to you, which is not used by 
other sites in the chain.

Incidentally, there are now web pages from which a route can be traced 
to a user-specified site.  Which can sometimes help decide where a delay 
might be, as well as provide a little more info about internet 
connectivity.


-- 
David G. Bell -- Farmer, SF Fan, Filker, Furry, and Punslinger..