Some descriptions of Ethernet refer to a segment as one side of a hub, i.e. just one link. The propagation delay information for a hubbed networks takes into account the small amount of time for a repeater to repeat. The repeater doesn't do much, but it does regenerate the preamble and signal. A set of link "segments" connected via hubs is all one collision domain.
Anyway, read my book! Please! :-) It covers all of this in gory detail. An earlier version of the Ethernet chapter is also available at http://www.certificationzone.com/. _______________________________ Priscilla Oppenheimer www.troubleshootingnetworks.com www.priscilla.com Priscilla Oppenheimer wrote: > > Newell Ryan D SrA 18 CS/SCBT wrote: > > > > If two 10 Base T Ethernet stations transmit at the same they > > receive data on > > their receive pins. Will both stations send out a 32 bit jam > > sequence? > > Yes. > > > If both stations do send a jam signal, why is the slot time > > closely related > > to round trip propagation delay? I would think it would be one > > way. > > A collision could happen at the other end of the network > segment. News of the collision has to travel back to the > senders. The signal travels outwards; the collision news > travels back. > > The goal is to make sure that the sender is still sending when > the news travels back, even if the news had to come from the > far end of the network segment. If the sender weren't still > sending, it wouldn't know that its transmission got damaged and > wouldn't back off and retransmit. You would lose the feature of > the NIC ensuring succussful transmission, which happens in a > microsecond time span, and have to depend on an upper layer > figuring out that there's a missing ACK, which happens in a > millisecond or worse time span. So, slot time is dependent on > round trip time because it considers the time for news of the > collision to travel back. > > Both senders transmit a jam signal to busy out the network for > another 32 bit times. At least one of them has to do it, but > they can't know that the other one did, so they both do it. > > Your question doesn't make sense, but hopefully there's some > info in that which will help you. > > > > > Ethernet, The Definitive Guide page 182 they have some values > > to use to > > figure out propagation delay on 10 MB networks. There is a > base > > value to > > start with and from there you add delay per meter. Why is the > > base value not > > zero? > > Even light in a vacuum takes some time to travel any distance. > It travels 299,792,458 meters per second to be exact, but > still, it's not zero. A signal on a network cable travels about > 2/3 the speed of light. > > I don't know what base value you are referring to, but zero > times anything is zero, so I doubt they could use a base value > of zero regardless. > > > Also between segments the numbers do not make any sense. > > Going from > > Base to Max I understand but between segments. > > A collision domain stops at the boundary between network > segments. A network segment is devices connected via hubs or > coax cable. In fact, it might help you to remember that > Ethernet was originally a long bus, like a link of Christmas > tree lights. The signal propagated outwards from the sender in > both directions and travelled to the end of the segment, and > hopefully not back if the segment was terminated correctly. But > if there was a collision, the signal did bounce back. > > All hubs are is a way to gather this Christmas tree string of > lights into a manageable structure. But when first learning > CSMA/CD details, it helps to think of the segment like that > string of lights. > > There's a ton of information about CSMA/CD in my book > "Troubleshooting Camus Networks." > > Also, "Ethernet: The Definitive Guide" really is definitive. > It's the bible. Don't doubt it. Try to understand it. > > _______________________________ > > Priscilla Oppenheimer > www.troubleshootingnetworks.com > www.priscilla.com > > > > > > > Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=63590&t=63581 -------------------------------------------------- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
