Re: [PLUG] DSL "guaranteed" speed

[Jim Trocki <trockij@transmeta.com>]

On Sun, 10 Feb 2002, Vince Bernardo wrote:

>     Comcast's subnet mask, as set automatically by your DHCP server, is
> 255.255.248.0. This means you have (8 x 255) - 1 = 2039 nodes on your
> neighborhood ethernet.

a subnet mask of 255.255.248.0 gives 21 bits for the network number and
11 bits for hosts on that network, which is (2^11) - 2 , or 2046 hosts.

>     Of course, this is ultimately meaningless unless you can somehow monitor
> real network performance -- I don't see how us users can do that.
> [Suggestions welcome.]

you can measure the performance of your own use but not the utilization
of the whole segment, without some administrative access to the network
gear. however, you can infer some amount of stuff from heuristics. for
example, traceroutes can show you congestion points, though the output
sometimes must be taken with a grain of salt. the latencies at each
hop may give you an indication of queuing delays at each router, or
serialization delays caused by congestion. keep in mind congestion may
be asymmetric, but sometimes you can get a reasonable idea of where a
performance problem may be (e.g. the first or second hop in a path).



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