Re: network speed question

On Sat, 22 Apr 2006 00:25:58 GMT, "Jim" <j.n@xxxxxxxxxx> wrote:


"Chuck" <none@xxxxxxxxxxx> wrote in message
news:rvbi425suiouohvr687ltq8qkhnh0gfcuv@xxxxxxxxxx
On Fri, 21 Apr 2006 10:49:21 -0700, "Steve T" <stumas@xxxxxxxxxxxxxxxxxx>
wrote:

Running three XP-Home SP-2 PC's with a D-Link wireless router.
PC #1 is the PC that has the cable modem connected to it. The network icon
states Local Area Connection Speed 100.0 Mbps.
PC#2 is wired to the wireless router and connection is through the NIC.
It's
network icon states 1394 Connection Speed 400.0 Mbps.
PC#3 has a wireless desktop adapter from D-Link and the Network icon on it
states Wireless Network Speed 108.0 Mbps.
The router is wireless but #1 and #2 are wired into it with network
cables.
Why the big discrepancy in speed between the wired PC's and what do the
numbers really mean? Thanks, Steve T

Steve,

The numbers refer to the bit rate on each medium. Overhead, of various
nature,
will decrease actual numbers, more or less substantially.

Firewire aka 1394 is a cabled point to point connection, ie one computer
to
another computer. Ethernet supports cabled multi point connections, ie
LANs.
If you're really going to connect multiple computers, for serious
networking,
you'll use Ethernet. For convenience, you may use WiFi, but you need to
be
aware of the limitations.

Wireless, aka WiFi, has a theoretical maximum of 10M for 802.11b, 54M for
802.11g, and 108M for 802.11g with proprietary enhancements. There are so
many
reasons why WiFi never yields actual speeds any where near the theoretical
maximum. I wrote a couple articles to discuss that.
<http://nitecruzr.blogspot.com/2005/10/wifi-will-never-be-as-fast-as-ethernet.html>
http://nitecruzr.blogspot.com/2005/10/wifi-will-never-be-as-fast-as-ethernet.html
<http://nitecruzr.blogspot.com/2006/01/proper-network-design.html#WiFi>
http://nitecruzr.blogspot.com/2006/01/proper-network-design.html#WiFi

--
Cheers,
Chuck, MS-MVP [Windows - Networking]
http://nitecruzr.blogspot.com/
Paranoia is not a problem, when it's a normal response from experience.
My email is AT DOT
actual address pchuck mvps org.
And, Ethernet tends to become saturated by collisions at somewhere around
60% of the quoted speed.

An interesting detail. Wasn't that more likely with classical Ethernet, and
CSMA/CD?

Steve,

classical Ethernet was similar to WiFi - there was a single medium (Ethernet was
a single long bus, to which all computers connected, randomly). With all
computers sharing one cable, the absolute maximum throughput was the published
speed of the cable. With WiFi, the absolute maximum throughput is the published
speed of the WiFi channel. With both, actual throughput drops dramatically, the
more devices you add to each channel, as collisions become normal.
<http://searchnetworking.techtarget.com/sDefinition/0,,sid7_gci213869,00.html>
http://searchnetworking.techtarget.com/sDefinition/0,,sid7_gci213869,00.html

Modern, or switched Ethernet, has a switch connected to each individual
computer. Each computer talks to the switch, which then talks to another
computer (or other switch or router). Collisions are virtually eliminated.

You can, theoretically, have up to 200M of throughput in each conversation
(between each pair of computers), or 100M / active computer. With switched
Ethernet, actual throughput goes up, the more devices you add to a switch.
There's only 3 devices (a switch, and 2 computers) in each conversation, and the
switch actively controls the conversation.

If you think modern Ethernet is interesting, you should try debugging a
classical Ethernet problem. That's when the 60% figure was relevant. Modern
Ethernet is boring (which is good).

--
Cheers,
Chuck, MS-MVP [Windows - Networking]
http://nitecruzr.blogspot.com/
Paranoia is not a problem, when it's a normal response from experience.
My email is AT DOT
actual address pchuck mvps org.
.

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