Think of it like this. Shared is as many people in a 10 foot by 10 foot room as you can stuff. The size of the room can be an analogy for the bandwidth of the network and the number of people in the room are analogous to PC's connected to the shared bandwidth.
The rules of conversation are this: You can only talk if you perceive that no one else is talking. If you hear someone else talking, you must stop immediately, and wait a random period until you are able to try speaking again. Of course, before you begin speaking, you must determine whether someone else is speaking. That's shared bandwidth. In this environment where only 1 PC can speak at a time, that PC is able to use the entire bandwidth of the pipe to send one frame. That frame travels at 10 Mbps. Each PC however must pause briefly between sending frames in an effort to let others talk... Now just because you have 10 PC's, each PC won't necessarily have traffic to send when all 9 others do. Thus, never make the comparison that if you have 10 PC's, on a shared 10 Mbps link, that each PC has 1 Mbps of bandwidth. Not true. Each PC has the ability to use 10 Mbps of bandwidth just like each person has the ability to speak in our 10 foot by 10 foot room--but as the number of people in that room increase in their desire to speak, the ability of others to "get a word in edgewise" decreases. The more PC's, the more difficult to utilize that shared bandwidth. Now the term "switched" is also known as "dedicated". Switched is a point-to-point link between the connected device and the switch. Think of it like our telephone system. I'm able to pick up my phone and dial whomever I like. When I lift the receiver, I have a dialtone. I couldn't care less if my neighbor is on the phone--I have a link to the telephone company's central office. I don't care who my neighbors are talking to. I don't hear that conversation. I can use as much of my bandwidth as I have available because I've got a dedicated, point-to-point link between myself and the telephone exchange (aka in networking terms, PC and LAN Switch port). Now let me throw a bit of a curve into this discussion. In a half-duplex switched environment, just because I'm able to use the full bandwidth between myself and the telephone company's central office, that in itself doesn't guarantee that my call will get through. Switched networks operating in half-duplex mode are able to suffer from collisions. If I try and phone my mom at the same time some goofy telemarketer does, our phone calls collide. Likely, I get a busy signal. In a full-duplex environment, this type of collision won't occur. One of us will get the "answering service" which will take a message, forwarding it when the line becomes free. In the full-duplex switching world, the switch buffers the traffic, forwarding it when the destination port is available. To go on a bit of a tangent here... Now of course, the telephone company only has a limited number of circuits that it can carry at one time. In networking terms, this is known as the capacity of the backplane of the switch. The switch is not able to forward unlimited traffic rates. For example, the Catalyst 5000 series switch can only forward 1.2 Gbps of traffic at any given time. > -----Original Message----- > From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]] > Sent: Monday, October 22, 2001 9:57 AM > To: [EMAIL PROTECTED] > Subject: RE: a question from lan switching book [7:23764] > > > is shared means that there is a 10M ethernet, if there are 10 station in > this network, every station has the 1M? > > or is shared means that there is a 10M ethernet, if there are 10 > station in > this network every station has the 10M bandwidth when you transmisstion, > (csma/cd) after this station trasmisted, another can transmit and has 10M > bandwidth. > > which is right? > > thanks for answered :) Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=23788&t=23764 -------------------------------------------------- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
