A hub provides shared bandwidth, so in your first example, the five
stations are sharing 10 Mbps. How much of the 10 Mbps they each get depends
on the traffic load that they generate, the timing of their packets, etc.
You plan to move to a switch. A switch provides dedicated bandwidth to each
port on the switch. In your example, you said that you are using 100 Mbps,
so each port on the switch provides 100 Mbps.
Half-duplex means that a station cannot send and receive at the same time.
If an Ethernet station on a twisted pair cable receives on its receive pair
while it is sending on its send pair, that is considered a collision.
If you are connecting just a single station to the switch port, then you
can configure the switch port and the station for full duplex. This allows
the switch port and the end station to send at the same time. They no
longer consider receiving while sending a collision event. Many people call
this 200 Mbps since both stations can theoretically send 100 Mbps at the
same time.
I suggest you read the Ethernet section in any of the many good CCNA or
CCDA books. As the other responder said, you may want to hold off on
learning about spanning tree, VLANs, trunking, etc., for now. You should
focus on basic Ethernet functionality. Also learn more about the switch
commands you can use to measure broadcast traffic, so you can determine if
that really is your problem or not.
When measuring FTP throughput, keep in mind that the results may be in
Bytes per second, so multiply by 8 to get bits per second. Also, FTP
throughput is application-layer throughput and includes header overhead
(IP, TCP and FTP), delay at the client and server side, acknowledgement
time, etc. You should not expect application-layer throughput to equal more
than about 30 or 40 percent of raw data-link-layer capacity.
As far as troubleshooting slow speed is concerned, we would need lots more
data to actually help you, but by using a protocol analyzer you can often
determine if it's the network that is slow, the server, or the client. It's
usually not the network! Proving this may require some advanced techniques
that you could learn in a Sniffer class though....
Priscilla
>>From: "Chee Tong Sim" <[EMAIL PROTECTED]>
>>Reply-To: "Chee Tong Sim" <[EMAIL PROTECTED]>
>>To: [EMAIL PROTECTED]
>>Subject: Slow Speed in 2900 Switches, Pls Help!!
>>Date: Mon, 03 Jul 2000 05:51:36 GMT
>>
>>Dear friends,
>>
>>I have a few questions to ask:
>>
>>1) Our company Network are running at 100M speed. Now if I connect a 10M
>>speed 3com hub to one of the ports in cisco 2900 switches (100M speed) in
>>the company network, and I connect 5 pc to the 3com hub, so, the network
>>speed of PC is 10M divided by 5= 2M each or 10M each?
>>
>>2) As the users complain about the speed, my boss asked me to use the brand
>>new 2900 switch (100M speed) to replace the 3com hub. So I connect 2900
>>switch to 2900 switch that in company network, and connect 5 Pcs to the 2900
>>switch, so the speed of PC should be 100M each or 100M devided by 5= 20M?
>>
>>3) But user still complain about the speed, I use the ftp function to check
>>the speed and found the speed is only 150kb/sec= 0.15M only. I suspect
>>because the switches that I used is a brand new switch, I havent configure
>>VLAN and spanning tree protocol on the new switch to block to packet
>>broadcase, so the speed is slow. If this is the case, can I consult you, how
>>to configure VLAN and spanning tree on the new switches? Can anyone teach
>>me? I ever seen the configuration file of a VLAN switches, but I don't know
>>what command should I type to configure VLAN on 2900 switch. What is the
>>procedures? Please help.
>>
>>Thanks in advance.
>>
>>Regards,
>>Chee Tong
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http://www.priscilla.com
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