Re: about installing ntop

On Sun, 2 Jul 2006, in the Usenet newsgroup comp.os.linux.networking, in
article <jf2kn3-a0d.ln1@xxxxxxxxxxxxxxx>, Michael Heiming wrote:

In comp.os.linux.networking Moe Trin <ibuprofin@xxxxxxxxxxxxxxxxxxxxxx>:

What's the bandwidth verses cost? I know in 100BaseT, the extra bux buys a
lot more bandwidth.

Iirc switch + 2 intel GB nics (cooper) were about 250,- Euro
(some years ago). Perhaps about 5x the price of 100 MBit/sec for
10x the bandwidth. Hard to compare if you go for 100MBit nics +
switch as cheap as possible it might be even more.

Misunderstood question. Ethernet switches, some dual speed hubs, and
routers are "Store and Forward" devices. The Ethernet switch has no idea
where the packet coming in on port 1 is going until it sees the first six
bytes of the packet. Even if it instantly set up to shuffle the bits to
the "right" output port, it's already 14 bytes behind (8 bytes of sync and
the first 6 bytes of the header), and that assumes that the output port
isn't busy at the time. (A router has an even harder task, because the
destination IP address is the 17th to 20th byte into the packet.) Thus,
the switch has to be able to store (at least some portion of) the packet
and that takes memory space. Don't you be thinkin' to long about this,
because the host on port 1 is being talkative, and here comes another
packet right now. Pull your fingers out!!!

The network interfaces almost certainly are going to convert the serial
bit stream of the Ethernet packet into something parallel - perhaps 32
or 64 bits wide - to gain speed capability. A Gigabit packet on a 64 bit
PCI bus (as an example) is a mere 15.7 mega(really-wide)words per second.
But what happens if a tenth of the hosts connected to your switch are
talking at the moment. Now you know why switches aren't 64 or 100 ports
wide.

A measure of performance is the _total_ bandwidth of the device - what
is the sum of the bits/second that the device itself (not one individual
interface) can handle. I've seen 100BaseT switches with 110 Mbps total
bandwidth - but you can also get total bandwidths up into 5 Gbps range for
a _VERY_ appreciable increase in cost.

Just turned on my mobile dual tube A/C, it's supposed to be hot
again today, it's just 7:30 (GMT+2). About 30-33C, doesn't sound
that much but high humidity kills you off even at those
temperatures in this country. ;(

My Atlas doesn't have a lot of relatively local weather statistics for
cities around the world, but that is 7-10C above average for the lower
elevations in Germany. Yes, I'm aware of humidity, having lived within
20 KM of the Gulf of Mexico (Houston TX sees above 90F and 90% for a lot
of the summer - and even Jean-David Beyer has mentioned similar numbers
a few tens of KM South of New York City) as well as parts of Southeast
Asia (Hong Kong can be extremely miserable for that). For much of the
year, we're at the opposite end - it's normally quite dry, and we average
18 cm of rain a year. It's been rather warm recently, and this creates a
"Thermal Low" pressure area, which tends to suck in moisture from the
oceans (the cause of all that fog in San Francisco is the thermal low in
the Central Valley some 80-120 KM to the East). It's quite sultry right
now, and the 10AM (GMT-7) reports from Phoenix are 94F (34.4C), with a
dew point of 57F which gives a Relative Humidity of 28%. The 10 day
forecast is calling for a 10% chance of scattered thunderstorms in the
afternoons - which is where most of that 18 cm per year comes from.
Before you laugh at that "high" humidity, know that the annual average is
more like 15%, which is how we can (sorta) tolerate those +45C highs that
are not all that uncommon here.

LCD monitors help lots, CRT types produce magnitudes more heat.

You're telling me? Actually, I have four CRTs in this room, and only
one is turned on, along with two LCDs.

Old guy
.

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