Introduction to switching
Switching is a common issue in computer networking. If we try to define this than we can simply say that based on some criteria if we change the route of the data then we can call it switching. This is one of the very basic things in computer communication. Suppose we need to send some data from one computer to another or from one server to another then we may need to use this technology to do it properly.
Let’s begin with some basic studies in computer switching. Usually switching is three kinds.
- Circuit switching
- Packet switching
- Message switching
Circuit switching is one of the oldest switching techniques in computer networking. Here each and every switch has memory to store the end users physical address and it checks the destination address then the switch will create a physical communication channel for those two devices and transfer data within those two devices. For some reason this was considered as the most secure data transfer system in computer networking. This communication terminates on basis of end of transmission signal and the connection goes off physically. Mostly it was used in telephony systems even till today the most confidential data is transferred using this switching system.
Next we will talk about packet switching; packet switching is a modern logical base switching technology. Here the data is divided into variable length packets and usually govern by the protocols. Packet switching is the first kind of dynamic logical switching. It does have a very small amount of space for buffering. But it does not allocate the packets on its own. The space allocation depends on requirement of the data transfer. This usually follows two methods to route the data. Those are:
- Datagram packet switching
- Virtual circuit packet switching
Before we start talking about datagram packet switching, I believe we should know a little about network layer, because datagram packet switching works on network layer. So let’s start by understanding some simple issues about network layer.
The basic work of network layer is to transfer data from one node to another. So the other works usually done in network layer is determining the switching technologies, error detection, logical path determination etc.
Now datagram packet switching usually works on network layer. So here all the packets works independently using the header of the packet. This header determines the route of the packet. The datagram packet switching usually works like this.
Now the virtual circuit packet switching usually works on data link layer. So we need to know some important issues about data link layer first. Data link layer consists of two sub systems, media access control layer and logical link control layer. Now these two sub systems do different things during data transmission. But the basic work done on this layer is encoding and decoding.
Now virtual circuit packet switching works on this data link layer, here before transferring any single packet a virtual link needs to be established between source and destination. This connection requires completing three phases,
- Setup phase
- Data transfer phase
- Connection release phase.
These three steps usually make this technology work. It establishes a connection then transfers the data and after the whole data is transferred and completes the signals then it releases the connection.
Last we have message switching, which works independently with a header file with each packet. But it is not recommended because of its working procedure. We also know this switching system as store and forward switching. So we need a little buffer to store the data and when the next node is ready to take data only then source can send a data. Another disadvantage of this technology is that it is a very slow.
So these are the basic computer network switching procedures.