week 6: NETWORK TOPOLOGY

network t0p0l0gy is an arrangement, mapping 0f the element like a links and n0des. netw0rk t0p0l0gy asl0 kn0wn as lay0ut 0r design. netw0rk t0p0l0gy may be physical 0r l0gical.

• physical t0p0l0gy refers t0 the physical design 0f a netw0rk including the devices, l0cati0n and cable installati0n.
• linear bus, star, star wired ring, tree

• l0gical t0p0l0gy refers t0 h0w data is actually transferred in a betw0rk as 0pp0sed t0 its phusical design.
• like a s0ftware

= > physical t0p0l0gy relates t0 a c0re netw0rk whereas l0g0cal t0p0l0gy relates t0 basic netw0rk.

• n0des is a c0mputer that relate the devices.

LINEAR BUS

• c0nsists 0f a c0ntinu0us length 0f cable that c0nnects tw0 0r m0re device t0gether.
• a bus called a backb0ne netw0rk.

• 0n the bus netw0rk, 0nly 0ne c0mputer can transfer inf0rmati0ns at a time.
• the inf0rmati0ns m0ves thr0ugh the entire length 0f the cable.
• each end 0f the cable 0n the bus netw0rk must have a TERMINAT0R.
• terminat0r are a device that abs0rb the signals transmitted 0n a netw0rk cable.

THE ADVANTAGES 0F LINEAR BUS

• easy t0 c0nnect
• require less cable
• setup  0f a bus netw0rk is simple.
• 0ften used t0 c0nnect a few c0mputers l0cated in a small area, such as an 0ffice.

THE DISADVANTAGE 0F LINEAR BUS

• when adding a c0mputers t0 a bus netw0rk, the cable must be br0ken t0 extend the cable and attach the c0mputer.
• the 0ther c0mputer 0n the netw0rk cann0t exchange inf0rmati0n whike the cable is br0ken.
• if 0ne 0f the device is br0ken, the wh0le device will be br0ken.
• large bulding d0es n0t used linear bus.

STAR NETW0RK 

• c0nsists 0f individual c0mputer c0nnected t0 a centre p0int 0n the netw0rk

• each c0mputer is c0nnected t0 a central netw0rk c0nnect0r, called a hub.
• the inf0rmati0n that transfer fr0m 0ne c0mputer t0 an0ther 0n the netw0rk passed thr0ugh the hub.
• each c0mputer must be relatively cl0se t0 the netw0rk hub.
• cable length between a c0mputers and the hub sh0uld be less than 100 meters.
• hubs c0mm0nly c0nnect 4, 8, 0r 16 c0mputers t0gether.
• it is g0od t0 used at large bulding.

THE ADVANTAGES 0F STAR NETW0RK

• easy detect fault
• easy t0 add new w0rkstati0n
• easy t0 install & wire
• the netw0rk d0es n0t need t0 be shut d0wn when new c0mputers are c0nnected

THE DISADVANTAGES 0F STAR NETW0RK

• if 0ne hub is br0ken, the wh0le n0des are br0ken t0o.
• large am0unts 0f cable are used.
• each c0mputer must be c0nnecting t0 a netw0rk hub, an expensive c0mp0nent

TREE NETW0RK

• c0mbinati0n 0f linear bus and star netw0rk

NIC (NETW0RK INTERFACE C0NTR0LLER)

• c0mputer hardware c0mp0nent that c0nnects a c0mputer t0 a c0mputer netw0rk.
• c0mm0nly implemeted 0n expensive cards that plug int0 a c0mputer bus

NOS (NETWORK OPERATING SYSTEM)

• reffered t0 as th Dial0guer; is the s0ftware that runs 0n a server and enables the server t0 manage data, users, gr0ups, security, applicati0ns and 0ther netw0rking functi0ns.
• design t0 all0w shared file and printer access among multiple c0mputers in a netw0rk, typically a l0cal area netw0rk (LAN), a private netw0rk 0r t0 0ther netw0rk.
• the m0st p0pular NOS are Microsoft Windows Server 2003.

REPEATER

• an electr0nic devices that receive a signal and transmits it at a higher level 0r higher p0wer, 0r 0nt0 the 0ther side 0f an 0bstructi0n, s0 that the signal can c0ver l0nger distances.
• the functi0n is:
• t0 receive a netw0rk signal f0rm 0ne LAN terminal cable segment and t0 regenerate and retransmit the signal as it is in its 0riginal strength 0ver a  0ne 0r m0re 0ther cable segment.
• regenerates the strength 0f the signal bef0re transmitting

NETW0RK SWITCHES

• c0mputer netw0rking device that c0nnects netw0rk segments 0r netw0rk devices.
• the term c0mm0nly refer t0 a multiple-p0rt netw0rk bridge that pr0cesses and r0utes data at the data link layer.

C0NCENTRAT0R

• pr0vide c0mmunicati0n capability between many l0w-speed, usually asynchr0n0us channels and 0ne 0r m0re high-speed, usually synchr0n0us channels.
• a device that c0nnects a number 0f links with 0nly 0ne destinati0n
• the main functi0n is t0 make a kink 0f l0ad balancing between tw0 0r m0re servers c0nnected t0gether, data distributi0n is d0ne acc0rding t0 the server pr0cessing rate.

ETHERNET

• has largely replaced c0mpeting wired LAN techn0l0gies.
• devude a stream 0f data int0 individual packets called FRAMES
• each frame c0ntains s0urce and destinati0n addresses and err0r-checking data; damaged data can be detected and re-transmitted.
• used c0axial cable as a shared medium.
• later the c0axial cables were replaced by twisted pair and fibre optic links in c0njuncti0n with hubs 0r switches.

L0CAL TALK

• a system 0f shielded twisted pair cabling, plugged int0 self-terminating transceivers, running at a rate 0f 230.4 kbit/s.
• its sl0s. at 230.4 kbit/s, its faster than a m0dem, but at 1 MB/min, it takes f0rever t0 m0ve large files 0r d0 backup 0ver the netw0rk.
• it gets c0ngested. all inf0rmati0n is br0adcast t0 the entire netw0rk, s0 a few heavy userd can bring it t0 its knees. the m0re users, the w0rse it gets.
• its a daisy chain f0rm 0ne device t0 the next t0 the next. if the wiring g0es bad, y0u end up with tw0 netw0rks that can't talk with each 0ther.

T0KEN RING

• l0cal area netw0rk pr0t0c0l which resides at the data link layer (DLL) 0f the OSI m0del.
• it uses a special three-byte frame called a t0ken that travels ar0und the ring.
• t0ken-p0ssessi0n grants the p0ssess0r permiti0n t0 trasmit 0n the m0dem.
• t0ken ring frames travel c0mpletely ar0und the l0op.