Datagram packet-switching is an approach in packet switching where each packet, referred to as a datagram, is processed individually. In this method, packets navigate through the network autonomously, with each one containing a header detailing the destination’s full information. Nodes within the network assess the packet’s header to determine the optimal link for forwarding closer to the destination. Unlike other systems, datagram packet-switching doesn’t rely on pre-defined routes, and nodes don’t need prior knowledge of the paths to be used.
A notable characteristic of this system is that packets forming a data stream might traverse various routes from the source to the destination. This could lead to packets arriving out of sequence, necessitating reordering to reconstruct the original message.
One advantage of this independent packet switching is the elimination of the need for connection setup and the avoidance of allocating fixed bandwidth as a circuit.
Datagram packet switches employ diverse methods for traffic management, distinguished by the time taken for packet transmission through the switch and their efficiency in filtering corrupt packets.
Three main types of datagram packet switches are:
- Store and Forward: This type holds the data until the whole packet is received, checking for errors. It prevents the spread of corrupted packets in the network but introduces a delay in switching.
- Fragment Free: It filters out many error-laden packets but doesn’t entirely stop the error spread. This mode provides quicker switching and reduced delays compared to store-and-forward.
- Cut Through: This method prioritizes speed, switching packets rapidly without filtering errors, resulting in minimal forwarding delay.
Datagram networks are designed to provide ‘best effort’ services without guaranteed delivery. Reliable delivery is the responsibility of end systems (like user’s computers) and is achieved using additional protocols.
The Internet is the most prevalent example of a datagram network, utilizing the IP network protocol. Applications that require only basic service levels employ datagram networks directly, using protocols like the User Datagram Protocol (UDP). This includes applications for voice and video communication and instant notifications for events like new email arrivals. In contrast, applications demanding reliable communication, such as email, web browsing, and file transfers, rely on protocols that offer robust services like guaranteed delivery and error control. Protocols such as the Transmission Control Protocol (TCP) and the File Transfer Protocol (FTP) provide these reliability features, ensuring data integrity and correct sequencing.