i am clear now, and thank you very very much for explain this point to me
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=23821&t=23764 -------------------------------------------------- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
