1.12 Network Facts


• Speeds often measured in bps (bits per second) but we are more interested in the bytes per second. There is approximately an 11:1 ratio.

T1 is 1.544 Mbps

T3 is 44.54 Mbps


• Network transmission,

baseband - single frequency- only one station may transmit at any time (Ethernet, ARCnet, Token ring). These must be in discrete digital packets.

boradband - multiple frequencies allow multiple simultaneous data streams. This network can reach higher speeds by multiplexing and can have continuous and/or analog channels (ISDN, CATV,ATM)


• Networks are some mix of clients and servers.

server - will share reseaources (eg, files) with many remote computers

client - a computer that typically talks to a limited number of servers


• Token based networks rotate talk permissions between machines by passing a “token”


• ARCnet - a token passing network that is relatively immune to noise


• IBM token ring - a star topology token passing network


• FDDI - fiber based token passing rings that rotate in opposite directions


• Ethernet - both bus and star topologies