Internetworking in Computer Science (Fully Explained)
In a real-world context, networks that fall under the same administration are typically distributed across various geographical locations. There may be a need to connect two distinct networks, whether they are of the same type or different types. The process of routing between these two networks is referred to as internetworking.
Networks can be classified as different based on several factors, including protocol, topology, Layer-2 network, and addressing scheme.
During internetworking, routers are aware of each other's addresses as well as addresses that extend beyond them. They can either be statically configured to connect to different networks or they can learn through the use of an internetworking routing protocol.
The routing protocols utilized within a single organization or administration are known as Interior Gateway Protocols (IGP). Examples of IGP include RIP and OSPF. When routing occurs between different organizations or administrations, it may involve an Exterior Gateway Protocol, with the only EGP being the Border Gateway Protocol.
Tunneling
If two geographically separated networks wish to communicate, they can either establish a dedicated line between them or transmit their data through intermediate networks.
Tunneling serves as a method that allows two or more identical networks to communicate by navigating through the complexities of intermediate networking. This tunneling process is set up at both ends.
As data enters one end of the tunnel, it is tagged. This tagged data is then routed through the intermediate or transit network to reach the opposite end of the tunnel. Upon exiting the tunnel, the data's tag is removed, and it is delivered to the other segment of the network.
Both ends appear to be directly connected, and the tagging allows the data to traverse the transit network without any alterations.
Packet Fragmentation
Most Ethernet segments have a maximum transmission unit (MTU) set at 1500 bytes. The length of a data packet can vary based on the application. Additionally, devices along the transit path possess specific hardware and software capabilities that determine the amount of data they can manage and the size of packets they can process.
When the size of a data packet is less than or equal to what the transit network can accommodate, it is processed without issues. However, if the packet exceeds this size, it is divided into smaller fragments before being forwarded. This process is known as packet fragmentation. Each fragment retains the same source and destination addresses, allowing for smooth routing through the transit path. Once it reaches the destination, the fragments are reassembled.
If a packet arrives at a router with the DF (don't fragment) bit set to 1 and the router cannot process it due to its size, the packet will be discarded.
Conversely, when a router receives a packet with the MF (more fragments) bit set to 1, it indicates that the packet is fragmented and that additional parts of the original packet are still en route.
Fragmenting a packet into excessively small pieces increases overhead, while creating fragments that are too large may prevent intermediate routers from processing them, leading to potential packet loss.
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