Links. The main difference is the policy for transmission. ALOHA simply sends when it feels, while CSMA/CD listens first to see if the medium is clear. Thus lots of transmissions are spoiled by other hosts starting to send while the current one is still going.
A later version, named slotted ALOHA, used timeslots which mark specific points in time. A host can only start sending at the start of a timeslot. This reduces the spoilage, but it is still not so good as CSMA/CD.
(a) Thick. (i) Heavy, difficult to route cables, awkward plugs and sockets. Strong limitations on lengths of cables and intervals of taps. (ii) Difficult to install both physically and to get electrically correct. (iii) Even when it was popular, it was quite expensive. Now not available.
(b) Thin. (i) Fairly easy to manipulate, but still strong limitations on lengths of cables. Requires an unbroken cable chain past every host, which is problematic as people like to unplug things. (ii) Easy to install, but you must keep an eye on cable lengths and clean connections otherwise you get erratic behaviour. (iii) Lower cost than thick Ether, but now not used.
(c) Twisted. (i) Very easy to manipulate, cables are light and flexible. Cable length rarely a problem. But now must have a cable per host, which means large numbers of cables if you want large numbers of hosts. (ii) Easy to install, but now you must take care over the placement of hubs/switches to ensure cable bundles do not get out of hand and that there is nota bottleneck is bandwidth through switches. (iii) Cables are cheap, small to mid-sized switches are cheap. Large switches are expensive. Requires careful planning of placement of switches.
(c) 100Mb Ethernet transmits at 125MBaud, that is 1/125000000 sec per symbol. So n characters, or 8n ASCII bits, which become (8n)*5/4 = 10n symbols taking 10n/125000000 sec, i.e., 80n nanosec.
Alternatively, 100Mb Ethernet transmits at 100Mb/sec, which is 12.5MB/sec, or 80 nanosec/byte.
A paper on 8B/10B.
8B/10B is used in the serial ATA (SATA) disk interface; Digital Audio Tape (DAT); PCI Express and others.
CDs use 8B/14B, more commonly called eight to fourteen modulation or EFM, while DVDs use an eight to sixteen modulation.
The principal advantages are:
Other advantages include no limits on the size of network, packet sizes can be very large, and so on.
Token Ring performed very well relative to early Ethernet. However, when switched Ethernet networks came along it was soon eclipsed in performance. As Ethernet took off it soon became very cheap, so nobody had any real reason to buy Token Ring: this feedback soon pushed Token Ring out of the picture.
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