A HUB can work in Full-duplex mode? [7:52973]
Just I want to know can a Hub work in full-duplex mode? Saravanan *** This message is proprietary to Future Software Limited (FSL) and is intended solely for the use of the individual to whom it is addressed. It may contain privileged or confidential information and should not be circulated or used for any purpose other than for what it is intended. If you have received this message in error, please notify the originator immediately. If you are not the intended recipient, you are notified that you are strictly prohibited from using, copying, altering, or disclosing the contents of this message. FSL accepts no responsibility for loss or damage arising from the use of the information transmitted by this email including damage from virus. *** Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=52973&t=52973 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: A HUB can work in Full-duplex mode? [7:52973]
No. The collision domain on a hub is shared throughout causing each port to listen before transmitting. A switch on the other had limits the collision domains by port therefore allowing the host to transmit at will. - Original Message - From: "Saravanan L" To: Sent: Tuesday, September 10, 2002 2:59 AM Subject: A HUB can work in Full-duplex mode? [7:52973] > Just I want to know can a Hub work in full-duplex mode? > > Saravanan > *** > This message is proprietary to Future Software Limited (FSL) > and is intended solely for the use of the individual to whom it > is addressed. It may contain privileged or confidential information > and should not be circulated or used for any purpose other than for > what it is intended. > > If you have received this message in error, please notify the > originator immediately. If you are not the intended recipient, > you are notified that you are strictly prohibited from using, > copying, altering, or disclosing the contents of this message. > FSL accepts no responsibility for loss or damage arising from > the use of the information transmitted by this email including > damage from virus. > *** Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=52979&t=52973 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: A HUB can work in Full-duplex mode? [7:52973]
r34rv13wm1rr0r wrote: > > No. The collision domain on a hub is shared throughout causing > each port to > listen before transmitting. No is correct. A hub can't be configured for full-duplex. If it can be, it's been misnamed. It's really a switch. But the explanation is not correct. A hub port doesn't listen before sending. It doesn't do MAC data-link-layer tasks. It simply forward bits that come in one port out all other ports. On a proper-sized network, the sending end hosts will still be monitoring their transmission, notice any collisions, and retransmit. In my new book, Troubleshooting Campus Networks, I have the following relevant paragraphs: "Collisions on Networks with Hubs and Switches A hub is a repeater that simplifies cabling designs, permitting a star configuration with a hub at the center, like the hub in an old hub-and-spoke wheel. Repeaters and hubs have a few other important jobs and characteristics also. Signals going through a repeater are retimed using the repeater’s timing circuitry to prevent the accumulation of signal jitter. A repeater also regenerates the signal to the proper amplitude and symmetry. Another job of a repeater is to rebuild a received preamble to avoid preambles getting shorter as they go through repeaters’ timing circuits. Repeaters also extend any fragments that have resulted from frames that collided and were cut short. The repeater extends the signal so that the total number of bits output equals 96 bits. Fragment extension ensures that short collision fragments survive a trip through a maximum-size network in the correct time frame. Stations receiving the extended fragment discard it and also defer from sending until the collision event is over. One of the most important tasks of a repeater is to enforce collisions on each connected segment. Repeaters enforce collisions by transmitting a collision-enforcement jam signal. Upon detecting a collision on one segment, a repeater transmits a collision enforcement jam signal on that segment and all other connected segments. This ensures that any station trying to send at that moment hears the collision. In this way, a repeater makes sure all stations are in the same collision domain and can react to collisions correctly. When a repeater detects a collision, it sends a 96-bit jam composed of alternating ones and zeros. Switches are replacing hubs in large campus networks. It is a common misconception that switches don’t need to know about CSMA/CD and that collisions don’t occur on switched networks. In fact, each switch port implements the CSMA/CD standard. When sending a frame, a half-duplex switch port senses carrier, defers if necessary, detects collisions, backs off, and retransmits. Whether a collision might occur or not depends on what is connected to the switched port. If a shared medium is connected to the switch, collisions may occur. Ethernet troubleshooters often wonder about cut-through switches and collisions. A cut-through switch outputs bits as soon as the destination address has been received and the destination port determined. What if there is a collision on that port? Should the switch send a collision enforcement jam on the port that received the frame so the original sender knows to try again? Or has the switch cached the frame so that it can do the retransmitting? Some troubleshooters assume that cut-through processing means that the frame was not cached. Vendor implementations may vary, but Cisco cut-through switches cache all frames, even when in cut-through mode. In this way, each port can handle CSMA/CD duties for that port and no other port. A switch retransmits if a collision occurs and does not notify the original sender in any way. Each port truly delimits a collision domain." Priscilla Oppenheimer > A switch on the other had limits > the collision > domains by port therefore allowing the host to transmit at will. > > > - Original Message - > From: "Saravanan L" > To: > Sent: Tuesday, September 10, 2002 2:59 AM > Subject: A HUB can work in Full-duplex mode? [7:52973] > > > > Just I want to know can a Hub work in full-duplex mode? > > > > Saravanan > > > *** > > This message is proprietary to Future Software Limited (FSL) > > and is intended solely for the use of the individual to whom > it > > is addressed. It may contain privileged or confidential > information > > and should not be circulated or used for any purpose other > than for > > what it is intended. > > > > If you have received this message in error, please notify the > > originator immediately. If you are not the intended recipient, > > you are notified that you are strictly prohibited from using, > > copying, altering, or disclo
Re: A HUB can work in Full-duplex mode? [7:52973]
But can the internal switch in a 10/100 hub work in full duplex??? (Don't know why I decided to ask that question other than to cause trouble...) Ken the Trouble Maker >>> "Priscilla Oppenheimer" 09/10/02 03:18PM >>> r34rv13wm1rr0r wrote: > > No. The collision domain on a hub is shared throughout causing > each port to > listen before transmitting. No is correct. A hub can't be configured for full-duplex. If it can be, it's been misnamed. It's really a switch. But the explanation is not correct. A hub port doesn't listen before sending. It doesn't do MAC data-link-layer tasks. It simply forward bits that come in one port out all other ports. On a proper-sized network, the sending end hosts will still be monitoring their transmission, notice any collisions, and retransmit. [snip] Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=53045&t=52973 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: A HUB can work in Full-duplex mode? [7:52973]
Ken Diliberto wrote: > > But can the internal switch in a 10/100 hub work in full > duplex??? What is an "internal switch in a hub?" Is that another case of a marketing term? ;-) I've never heard of the term. If it's really a hub, then it's just a repeater. Full duplex has no meaning in this contect. Keep in mind that no self-respecting Ethernet guru EVER used the terms half-duplex or full-duplex when talking about Ethernet until a few years ago. Ethernet was plainly and simply CSMA/CD. (MA stands for multiple access, and is of course not full duplex.) Hubs come from this environment. Nobody used the term "switch fabric" or "hub fabric" or "internal switch" either. ;-) A hub was a dumb physical-layer repeater that did the things I mentioned below, (with a few data-link-layer jobs thrown in to ensure collision detection works correctly for the end hosts in a network extended with repeaters/hubs.) Priscilla > > (Don't know why I decided to ask that question other than to > cause > trouble...) > > Ken the Trouble Maker > > >>> "Priscilla Oppenheimer" 09/10/02 > 03:18PM > >>> > r34rv13wm1rr0r wrote: > > > > No. The collision domain on a hub is shared throughout > causing > > each port to > > listen before transmitting. > > No is correct. A hub can't be configured for full-duplex. If it > can be, > it's > been misnamed. It's really a switch. But the explanation is not > correct. A > hub port doesn't listen before sending. It doesn't do MAC > data-link-layer > tasks. It simply forward bits that come in one port out all > other > ports. On > a proper-sized network, the sending end hosts will still be > monitoring > their > transmission, notice any collisions, and retransmit. > [snip] > > Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=53046&t=52973 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: A HUB can work in Full-duplex mode? [7:52973]
Priscilla Oppenheimer wrote: > > What is an "internal switch in a hub?" Is that another case of a marketing > term? ;-) I've never heard of the term. I believe that it is usually a bridge between the 10mb segment and 100Mb segment in a dual speed hub. Naturally the marketing people use the term switch :-) Peter Walker CISSP, CSS1, CIPTSS, CCIP, CCNP, etc Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=53068&t=52973 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: A HUB can work in Full-duplex mode? [7:52973]
My understanding of a 10/100 hub is it has a bridge/switch internally to connect the 10Mbps side to the 100Mbps side (a repeater wouldn't be able to do this). >>> "Priscilla Oppenheimer" 09/10/02 05:03PM >>> Ken Diliberto wrote: > > But can the internal switch in a 10/100 hub work in full > duplex??? What is an "internal switch in a hub?" Is that another case of a marketing term? ;-) I've never heard of the term. If it's really a hub, then it's just a repeater. Full duplex has no meaning in this contect. Keep in mind that no self-respecting Ethernet guru EVER used the terms half-duplex or full-duplex when talking about Ethernet until a few years ago. Ethernet was plainly and simply CSMA/CD. (MA stands for multiple access, and is of course not full duplex.) Hubs come from this environment. Nobody used the term "switch fabric" or "hub fabric" or "internal switch" either. ;-) A hub was a dumb physical-layer repeater that did the things I mentioned below, (with a few data-link-layer jobs thrown in to ensure collision detection works correctly for the end hosts in a network extended with repeaters/hubs.) Priscilla > > (Don't know why I decided to ask that question other than to > cause > trouble...) > > Ken the Trouble Maker [snip] Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=53106&t=52973 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: A HUB can work in Full-duplex mode? [7:52973]
Ken Diliberto wrote: > > My understanding of a 10/100 hub is it has a bridge/switch > internally to Technically there's no such thing as a 10/100 hub. If a device connects two different speed networks, it has to do store and forward of frames (not just forwarding of bits) and hence is a bridge or switch. I wouldn't call a device that does both, includes hub ports and an internal bridge/switch as you mention, "a hub," but product names are chosen by marketing people not engineers. Shall we create a new term? Brub or swub or hubge or hubtch. To quote my co-author in Troubleshooting Campus Networks, it's amazing the terminology that can result when one engineer and two marketing people go out to lunch. He threw that in a few times in our book. :-) Priscilla > connect the 10Mbps side to the 100Mbps side (a repeater > wouldn't be able > to do this). > > >>> "Priscilla Oppenheimer" 09/10/02 > 05:03PM > >>> > Ken Diliberto wrote: > > > > But can the internal switch in a 10/100 hub work in full > > duplex??? > > What is an "internal switch in a hub?" Is that another case of a > marketing > term? ;-) I've never heard of the term. If it's really a hub, > then it's > just > a repeater. Full duplex has no meaning in this contect. Keep in > mind > that no > self-respecting Ethernet guru EVER used the terms half-duplex or > full-duplex > when talking about Ethernet until a few years ago. Ethernet was > plainly > and > simply CSMA/CD. (MA stands for multiple access, and is of > course not > full > duplex.) Hubs come from this environment. > > Nobody used the term "switch fabric" or "hub fabric" or > "internal > switch" > either. ;-) A hub was a dumb physical-layer repeater that did > the > things I > mentioned below, (with a few data-link-layer jobs thrown in to > ensure > collision detection works correctly for the end hosts in a > network > extended > with repeaters/hubs.) > > Priscilla > > > > > (Don't know why I decided to ask that question other than to > > cause > > trouble...) > > > > Ken the Trouble Maker > > [snip] > > Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=53129&t=52973 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: A HUB can work in Full-duplex mode? [7:52973]
At 6:45 PM + 9/11/02, Priscilla Oppenheimer wrote: >Ken Diliberto wrote: >> >> My understanding of a 10/100 hub is it has a bridge/switch >> internally to > >Technically there's no such thing as a 10/100 hub. If a device connects two >different speed networks, it has to do store and forward of frames (not just >forwarding of bits) and hence is a bridge or switch. I wouldn't call a >device that does both, includes hub ports and an internal bridge/switch as >you mention, "a hub," but product names are chosen by marketing people not >engineers. Shall we create a new term? Brub or swub or hubge or hubtch. In the proposed joint venture between Cisco and Synoptics, the term selected for router/hub technology was called a "rub" or "rubsystem." You can find this in an early version of the Internetworking Glossary. When I brought this up to a CID class, one of my students mused.."router/hub...hub/router...why didn't they call it a hooter?" Priscilla is quite correct technically. There is no standard definition of "hub." Cabletron, for example, had a marketing approach which called any multislot chassis a hub, into which you could plug L1, L2, or L3 boards. Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=53142&t=52973 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: A HUB can work in Full-duplex mode? [7:52973]
It's fun arguing "marketing-speak" with engineering folks. :-) I see a 10/100 Sub (I like that one the best) as two hubs with a bridge between them. Based on the connect speed, a port can participate on either the 10Mbps side or the 100Mbps side. I was just wondering if that bridge was full or half duplex... :-) P.S. I just jumped into this thread for the fun of it. I'm getting my moneys worth. :-) >>> "Priscilla Oppenheimer" 09/11/02 11:45AM >>> Ken Diliberto wrote: > > My understanding of a 10/100 hub is it has a bridge/switch > internally to Technically there's no such thing as a 10/100 hub. If a device connects two different speed networks, it has to do store and forward of frames (not just forwarding of bits) and hence is a bridge or switch. I wouldn't call a device that does both, includes hub ports and an internal bridge/switch as you mention, "a hub," but product names are chosen by marketing people not engineers. Shall we create a new term? Brub or swub or hubge or hubtch. To quote my co-author in Troubleshooting Campus Networks, it's amazing the terminology that can result when one engineer and two marketing people go out to lunch. He threw that in a few times in our book. :-) Priscilla [snip] Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=53166&t=52973 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: A HUB can work in Full-duplex mode? [7:52973]
Ken Diliberto wrote: > > It's fun arguing "marketing-speak" with engineering folks. :-) > > I see a 10/100 Sub (I like that one the best) as two hubs with > a bridge > between them. Based on the connect speed, a port can > participate on > either the 10Mbps side or the 100Mbps side. I was just > wondering if > that bridge was full or half duplex... :-) It would have to be half-duplex since the only ports it can communicate with are hub ports on the hub sides of the "sub." Priscilla > > P.S. > I just jumped into this thread for the fun of it. I'm getting > my > moneys worth. :-) > > >>> "Priscilla Oppenheimer" 09/11/02 > 11:45AM > >>> > Ken Diliberto wrote: > > > > My understanding of a 10/100 hub is it has a bridge/switch > > internally to > > Technically there's no such thing as a 10/100 hub. If a device > connects > two > different speed networks, it has to do store and forward of > frames (not > just > forwarding of bits) and hence is a bridge or switch. I wouldn't > call a > device that does both, includes hub ports and an internal > bridge/switch > as > you mention, "a hub," but product names are chosen by marketing > people > not > engineers. Shall we create a new term? Brub or swub or hubge or > hubtch. > > To quote my co-author in Troubleshooting Campus Networks, it's > amazing > the > terminology that can result when one engineer and two marketing > people > go > out to lunch. He threw that in a few times in our book. :-) > > Priscilla > > [snip] > > Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=53179&t=52973 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: A HUB can work in Full-duplex mode? [7:52973]
I agree with you there. Do you think these boxes run Spamming Tree??? ;-) >>> "Priscilla Oppenheimer" 09/11/02 09:07PM >>> Ken Diliberto wrote: > > It's fun arguing "marketing-speak" with engineering folks. :-) > > I see a 10/100 Sub (I like that one the best) as two hubs with a bridge > between them. Based on the connect speed, a port can participate on > either the 10Mbps side or the 100Mbps side. I was just wondering if > that bridge was full or half duplex... :-) It would have to be half-duplex since the only ports it can communicate with are hub ports on the hub sides of the "sub." Priscilla Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=53183&t=52973 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
