Networking | Inter Networking Concept

📌Highlights: Hi friends ! In this post we will discuss about the concept of inter-networking. This post include the concept of following things such as about Repeater, about Bridges, about Routers, about Gateways, about Protocol converter.

To connect two or more network together is called inter networking. If two network are inter connected than they must use same protocol.

For inter networking following devices are used:

1. Repeater.

2. Bridge.

3. Router.

4. Gateway.

5. Protocol Converter.

REPEATERS:

A repeaters is an electronic device that operate on only the physical layer of OSI model. A repeater allow us to expand only the physical length of a network.Repeaters recognise the shape of signal that mean whether signal is 0 or 1. 

Suppose we sand a signal if the distance is long than after some time or after certain distance the signal will be destroyed / weak.

But repeater regenerate the original bit pattern before the signal become weak or corrupted and put the refreshed copy back onto the link.

Let we understand with the help of diagram. If we have two different network and we use repeater what happen.

In the above diagram repeater has two physical layer. Suppose LAN-1 recognise +5 volt as 1 and -5 volt as 0. But LAN-2 recognise +10 volt as 1 and -10 volt as 0.

If the +5 volt come from the LAN-1 than it goes to physical layer-1 (PL-1). Now PL-1 send this signal in PL-2 that mean both physical layer communicate to each other and PL-2 send message in LAN-2.

But in LAN-2 +10 volt is consider as 1 so here repeater can convert +5 volt signal to +10 volt signal for recognising 1 by LAN-2.

BRIDGES:

Bridges operate in both physical and data link layer of the OSI model. Bridges can divide a large network into smaller segments. They can also send / transmit frame between two different LAN's. Unlike repeaters bridges contain logic that allow them to keep traffic for each segment separate. In this way bridges filter the traffic and control congestion.

Let we understand by the help of diagram. Suppose if we have two LAN. One is token LAN and another is CSMA/CD. Both have different physical and MAC layers.

MAC- Media Access Control. In LAN it decide who can send data and How much?

Note: Each LAN card contain 6-bit address which is also called MAC address or unique address.

Now in above diagram if A want to send packet to X than it will send data packet. This data packet is first come in physical layer-2 → MAC layer-2 → LLC  (Logical Layer Control) → MAC Layer-1 → physical layer-1 and after wait for taken in token ring.

But if X send data packet to a than A does not wait for token.

So we can say that bridge can handle different between two different network. To connect two different LAN's bridge is used.

PURPOSE OF USING BRIDGE:

Suppose, If we take two LAN in college

Here if we take repeater than it does not recognise the address it only sand data for one LAN to another.

In this case if A want to send data to X than data is spread over whole channel. If suppose A send data to B than even the data is spread over LAN-1 & LAN-2 which is useless.

But in this case if R recognise the address than efficiency of channel will increased. So here using bridges are beneficial for us because it have ability to recognise address , which is not in R. Bridges are used to connect same type of two network of same LAN.

The purpose of using bridges are following:

1. Match two different protocol.

2. Selective repeat  (most popular).

Selective Repeat protocol are classified into following:

1. Transparent Bridges

2. source Bridges.

Suppose we consider more than one LAN through bridges such as:

In the above diagram if A & B communicate to each other which are in the  same LAN and we are using bridge for connected other LAN's than the message / data is not spread over the other LAN.

Here bridge's are intelligent because concept of backward learning is implemented in bridge's Actually bridge's are call as ready to plug device.

👉 In transparent bridge's A need not be bother about the existence of bridge. Design of bridge is complex and costly.

👉 Source Routing Bridge. In this scheme complexity is increase in LAN (i.e computer / Host / Terminal) side. But bridge are simple  (i.e No complexity in bridge's)

Here packet explain the sequence of transmission such as B1 → L3 → B3 → L4 → P. 

In this scheme each computer contain table of source that is why it is called source routing bridges. Bn only matches the address according to address given in the packet.

In this scheme their is no need to create table for bridge's it is already created in source.

There are three implementation takes place in source routing bridges:

1. Software.

2. Hardware.

3. Firmware.

SOFTWARE

In this type of implementation one program is written in bridge which match the address.

HARDWARE

Hardware implementation mean a address is store permanently in bridge's. It is faster scheme than software implementation but not reliable because address are permanent and we can not change it.

FIRMWARE

It is a combination of software and hardware implementation. Suppose A & B are in same LAN than B can only recognise one bit i.e first bit such as

If first bit is 0 → That mean no need to action and no need to store any address because data are in same LAN.

If first bit is 1 → That mean some action will perform.

In this way flexibility will increase.

ROUTERS AND GATEWAYS

ROUTERS

Router access to network layer address and contain software that enable them to determine which of several possible paths between those address is the best for a particular transmission. Router operate in physical , DLL (Data Link Layer) and Network Layer of OSI model. Router relay packets among multiple interconnected network.

Here in the above diagram routers are used to connect two in entirely different network. Mostly routers are used in WAN.

Router act like station on a network.Their simplest function is to receive  packet from one connected network and pass them to a second connected network. However if a received packet is addressed to a node on a network of which the router is not a member.The router is capable of determining which of its connected network is the best next relay point for the packet.

Router are also use to decide the route and connect more than one LAN's such as 

Note: Network layer is not available in LAN because their is no need to take routing decision in LAN. In LAN we are using single channel.

Routing mainly work in network layer.In LAN each computer have some MAC address which is exclusively for LAN. Outside the LAN no body know about MAC address.So we convert MAC address into IP address and IP address is known for every one in network.

Here ARP (Address Resolution Protocol) is used to convert MCA address into IP address and IP address into MCA address. 

IP address are of 32-bit in size.Router can identify only IP address.

GATEWAYS

Gateways potentially operate in all seven layer of OSI model. A gateway is a protocol converter.A router by itself transfer, accept and relays packet only across network using similar protocols.A gateway on the other hand can accept a packet formatted for one protocol and convert it into a packet format for another protocol.

A Gateway is generally a software installed with in router. The gateway understand the protocols used by each network linked into the router and is therefore able to translate from one to another.

In some cases modification is necessary in the header and trailer of the packet.

Both Net 1 and Net 2 have different protocols. Suppose the packet size of Net-1 is 4096 byte and the packet size of Net-2 is 512 byte and here if we use   Router than it can not change the size of packet according to network and send as it is packet to destination. But the size of packet at destination end is different than it can not recognise or the packet is rejected.

So here we use gateways which convert 4096 byte of packet to 512 byte or 512 byte to 4096 byte. So that both network can communicate each other.

Suppose Net-1 use optical fibre cable and Net-2 use copper wire than the frame size of Net-1 is small than Net-2 because Net-2 use copper wire due to which more error will occur , so an error detection code is also added in frame but in Net-1 no error detection is needed because it use optical fibre cable which has very less possibility of error. Then in that case gateway add error detection code in frame of Net-1 and store it and than send it to Net-2. This addition is done for matching their frame size.

Gateway are of two type:

1. Half Gateway.

2. Full Gateway.

FULL GATEWAY

In full gateway both side four layers are implemented. It is same as simple gateway.

HALF GATEWAY

Suppose we have two network Net-1 and Net-2. Both Net-1 and Net-2 have different protocols suppose Net-1 can understand +5 volt for 1 and -5 volt for 0 and Net-2 can understand +10 volt for 1 and -10 volt for 0.But they don't want to share their rules to each other than we connect half gateway in Net-1 side and half gateway in Net-2 side and than they make an common agreement for both that +7 volt for 1 and -7 volt for 0. Now they can communicate to each other by follow this rule. This is for security purpose.

PROTOCOL CONVERTER

This is device which is use to connect those type of network which are supported by different layers.

Suppose Net-1 use four layers and Net-2 use seven layers or Net-2 use four layers and Net-1 use seven layers.

It is used to connect two internally different network.

📌Friends ! this is end of this post here we cover following topics about Inter networking such as about Repeater, about Bridges, about Routers, about Gateways, about Protocol converter etc. I hope it is useful for you. We will meet in next new post till continue reading...