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Today we will see switching technics we will start position with the outcomes upon the completion of the session the learner will be able to understand switching and we will also understand various switching techniques. such as circuit switching message switching and packet switching .
We will start with the definition of a switching . switching in computer network helps in designing the best route for data transmission if there are multiple paths in a large network. for example if you take Internet there are multiple paths exist between the source and the destination and switching helps in designing.
The best route for data transmission since big networks like Internet there are multiple paths and it should also provide a feel like one-to-one connection. we have seen what is switching .
Now we will see what are the various techniques in switching basically. Switching techniques are classified into three types
1.) Circuit Switching
2.) Message Switching
3.) Packet Switching .
Packet switching is categorized into Datagram approach or virtual circuit approach. We will see one by one in detail firstly we will start with circuit switching in circuit switching there is always a dedicated path that is established between the sender and the receiver it means between the sender and the receiver there will be a dedicated path before data transfer connection will be established.
first it means before data is transferred we have to establish the connection once the connection is made then only data transfer begins for example telephone network telephone network is a well-known example for circuit switching sender first dies.
the number once the connection is established then they can talk to each other so dialing the number and establishing the circuit is started in the first phase and then the data transfer happens basically circuit switching has three phases
Number one connection establishment number two data transfer and number three connection disconnection so if you observe here before data transfer connection is established that is what is mentioned here before data transfer connection will be established.
we will see an example and it will be very helpful for you to understand this in a better way in this example let’s say there is a big network base number one is dealing with connection establishment suppose if he is the sender and he is the receiver so phase number one is establishing the connection this green line represents that this is the connection that is established between the sender and the receiver suppose if sender has a message to transmit before the message gets transferred
we see here that the connection is already established and after the connection is established the data transfer happens so this is what a circuit switching is so before data transfer can happen the circuit or the connection is established and all the communication uses this channel or this connection and this connection is reserved between the sender and the receiver after phase number two now comes phase number three phase number three means connection disconnection now if you observe the green lines are removed it means the connection gets terminated this is what circuits were chinnis so far.
we have seen motor circuit switching and this is the first technique in switching techniques. now we will see the second technique the message switching in message switching. it uses store-and-forward mechanism. it means the message is transferred as a complete unit a single unit and forwarded using store-and-forward mechanism at the intermediary node.
if you don’t understand this just wait for my example suppose if sender wants to send a big data and this big data cannot be transferred in a single stretch so it is broken into individual entities or pieces and each of these pieces are transmitted to the intermediary node this intermediary node receives all the small pieces and constructs the full message after getting that full message or the complete unit then only it forwards the data this is what message switching is.
we will see an example now it will be clear for you suppose if the the sender and this is the receiver if the sender wants to send a message this big message is broken into individual pieces and finally all the individual pieces are collected and stored here after getting the complete message then comes the forward phase so first it stores all the pieces and then it forwards so the complete message is stored and then it is forwarded.
This is an example for message switching and if you observe the message as reach the receiver now coming to this point message switching is not suited for streaming media and real-time applications for example if sender is sending a real-time communication two people are talking over voice over IP phone so we can’t expect the intermediary node to collect or alter data.
That is sent by the person and forward it because it is a real-time communication for real-time applications message switching technique cannot be used so for streaming media like real-time communications or live data transfer or for real-time applications message switching technique will not be suitable and so far we have seen circuit switching and message switching.
Now we will move on to the third switching technique that is the packet switching packet. Switching the Internet is a packet switched Network here the message is broken into individual chunks and each of these chunks are called as packets.
This is like our message switching where message is broken into individual chunks called packets.
Here is the difference between this packet switching and the message switching in packet switching each packet is sent individually suppose if a big message is broken into five pieces and each of these five pieces can be sent individually so if each of these five pieces can be sent individually each of the pieces should have some information that uniquely identifies
The source and the destination each packet will have source and destination IP addresses in addition to source and destination IP address we will also have sequence number because we know very well that each packet is sent individually so any packet may be received at the destination in any order so we need to reorder the packet and sequence number will help the receiver to reorder the packets also if any packet is missing this sequence number will help to detect the missing packets at the same time.
these sequence number will help the receiver to send acknowledgement say for example if packet number file is received it will send packet number five is received as an acknowledgement to the sender in case if packet number six is not received by the destination.
It will not send any acknowledgment to the sender so sender will wait for the set nourishment for a certain period of time if no acknowledgement is received for packet number six it understands that the packet may be lost so it retransmits that packet sequence numbers will help the receiver to reorder the package to detect missing package and send acknowledgments basically packet switching has two approaches.
we will see what are these two approaches in packet switching there are two approaches to packet switching Datagram approach and virtual circuit approach we will see Datagram approach now Datagram packet switching it is also known as connectionless switching it means each independent entity is called as Datagram.
If the message is broken into five pieces then each of these pieces each of these five pieces are called as datagrams and each datagrams contain distillation information and the intermediary devices uses this information which information this destination information to forward the data grams to the right destination suppose if the original message is broken into five datagrams each Datagram loved destination information and these destination information will help the intermediary device to forward the datagrams to the right destination so in this case each Datagram will take different routes it means the part is not fix-it here.
unlike circuit switching the path is not fixed in Datagram approach who takes this routing decision or forwarding decision. It is the responsibility of the intermediary nodes to take the routing decision or forwarding decision to forward the packets to the right destination.
we will see an example it will be very easy for you to understand now so this is an example where this is the sender and this is the receiver now let us assume that the original message is broken into four datagrams Datagram 1 2 3 & 4 now if you observe Datagram 1 is going this way and Datagram 2 takes this path now Datagram 1 is going this way whereas Datagram 2 is taking a different route and if you observe Datagram 1 is using a different way which is not used by Datagram 2 and this is not used by Datagram 3 and if you observe Datagram 4 is moved faster than Datagram 3 1 2 4 & 3 is the order of the data grants.
That are received but receiver knows how to reorder this because each datagrams has sequence numbers so these sequence numbers will help the reordering process easily now the reordering is done by the receiver and it constructs the original message as light it was sent by the sender so this is an example for packet switching and the Datagram approach we have one more approach in packet switching that is virtual circuit approach virtual circuit switching is also known as connection oriented switching so in the previous case that is the Datagram approach it is connectionless where every individual Datagram takes a different route but here in the case of a virtual circuit switching a pre-planned route is established before the messages are sent it means before sending the messages some route is decided using some virtual circuit identifier.
So there will be a virtual circuit identifier followed in the scheme and this route is decided before the data are sent called request and call except our special packets that are used in the scheme to establish the connection between the sender and the receiver so in this approach the path is fixed for the duration of a logical connection in the previous technique.
That is the diagram approach the path is not fixed but still it is a packet switching technique only but here this virtual circuit approach the path is fixed for the duration of a logical connection. we will see an example then it will be clear for you in case if this is the sender and this is the receiver you can see that there is a logical path that is established and data transfer is happening only through this way.
So packet number one two three four five and six all these packets are travelling in this route only and after the data transfer process is over this connection gets terminated if the same two computers are same two nodes wants to exchange data we can’t guarantee that the same route will be taken for the next data transfer also and the route will be decided based on the availability.
We will have a simple recapture now so basically switching means finding the best route for transferring the data from the sender to the receiver and particularly in a large network.
Technics of switching basically has three techniques circuit switching message switching and packet switching and packet switching has two approaches Datagram approach virtual circuit approach and that’s it guys we are at the verge of completion.
I hope now if you understood what is switching I hope now you understood what are the various switching techniques like so cuteee switching message switching and packet switching
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