Geat explanation! And one of the best analogies I've seen yet. If you're not an instructor you ought to be...
Leigh Anne Chisholm wrote: > 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=23795&t=23764 -------------------------------------------------- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
