VTU Module-3 | Network Layer Protocols

18EC71 | COMPUTER NETWORKS | Module-3 VTU Notes

Network Layer Protocols: Internet Protocol (IP)

The Internet Protocol (IP) serves as a crucial component in the network layer, facilitating communication across interconnected networks. It operates using a Datagram format, where data is packaged into discrete units known as datagrams. These datagrams contain essential information, such as source and destination addresses, allowing for the proper routing of data through the network.

Datagram Format:

IP datagrams consist of a header and payload. The header includes vital details like version, header length, type of service, total length, identification, flags, fragment offset, time to live, protocol, header checksum, source and destination IP addresses. The payload carries the actual data.

Fragmentation:

To accommodate varying network technologies with different maximum transmission unit (MTU) sizes, IP supports fragmentation. When a datagram is too large for a network segment, it is divided into smaller fragments. At the receiving end, these fragments are reassembled to reconstruct the original datagram.

Options:

IP provides options in the header to support additional functionalities beyond the basic requirements. These options allow for features like timestamping, security, and route recording, enhancing the versatility of IP.

Security of IPv4 Datagrams:

While IPv4 does not inherently include robust security features, additional protocols like IPsec can be employed for securing communications. IPsec provides mechanisms for authentication, integrity, and confidentiality, ensuring the secure transmission of data across networks.

Unicast Routing: Introduction

Unicast routing involves the process of determining the optimal path for transmitting data from a single source to a specific destination in a network. This is essential for efficient and reliable communication.

Routing Algorithms:

1. Distance Vector Routing: This algorithm relies on routers sharing information about their routing tables with their neighbors. Each router maintains a vector indicating the distance to all reachable destinations. Periodically, routers exchange this information to update their routing tables. The classic example is the Routing Information Protocol (RIP).
2. Link State Routing: Link state routing algorithms, like OSPF (Open Shortest Path First), focus on routers sharing information about the state of their links with all routers in the network. Routers use this collective information to construct a complete map of the network. With this map, routers can calculate the shortest path to a destination, enhancing efficiency.
3. Path Vector Routing: Commonly used in Border Gateway Protocol (BGP), path vector routing involves routers sharing information about the paths to various destinations. Unlike distance vector routing, path vector algorithms consider the entire path taken to reach a destination. This is particularly crucial in large-scale networks and the global Internet.