Now we turn our attention from the applications and social issues (fun stuff) to technical issues involved in N/w design (the work stuff).
generally CN are designed by 2 important things
1.. Transmission technology.
2. Scale(size).
within a N/w , now we need to specify how data are transmitted from one device to other, which we will discuss later.
1. Transmission Technology:-
Broadly speaking there exists two types of Transmission technology that are widely in use
i. Braodcast links.
ii. Point to Point links.
Broadcast links(or) Networks:-
- These type of N/w’s will have a single communication channel.
- this channel is shared by all the machines on the network.
- short messages called ‘packets’ sent by any machine are received by all the others.
- for intended reception from a machine a address field with in the packet is used.
- A machine the packet, if the packet is intended for it , it will process it otherwise it will simply ignores it.
ex:-i. calling a person who stands in the corridor from one end to other end.
ii. In the airport the announcement asking for the flight 644 passengers to report gate12 for immediate boarding.
- Broadcasting Networks also allow to send a packet to all the users of the Network by using a special code in the address field, that is in this case a packet is received by all the machines and is processed by every machine . This is known as Broadcasting.
Multicasting:-
Broadcast Networks also supports transmission to a subset of machines known as Multicasting.
its address field contains n bits.
onebit—> reserved for indication of multicasting.
(n-1) bits—> can hold a group number.
and each machine in a multicast N/w is able to subscribe any number of groups and a packet send to a group can be delivered to all machines subscribing that group.
Point to Point links:-
- Point to Point N/ws consists of many connections between individual pair of machines.
- to go from source to destination a packet on this type of N/w may go from intermediate machines often multiple roots of different lengths. so finding good one is important.
- smaller geographically localized networks use broadcasting while larger networks uses point to point.
- A point to Point with one sender and one receiver is called Unicasting.
- It provides a dedicated communication link between two devices most of the cases these uses wire (or) cable to connect two ends but Microwave (or) Satellite links may also possible.
ex:- T.V controlling with infrared remote control.
- Entire channel capacity is reserved for Transmission between Source and Destination.
2. Scale(size):-
Another alternative criterion for classifying networks is their scale, that is we classify multiple processor systems by their physical size as follows PAN,LAN,WAN,MAN.
(write about PAN,LAN,WAN,MAN).
