What Does 'Datagram' Mean?

What is a Datagram?
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A “datagram” is a self-contained, independent entity of data carrying sufficient information to be routed from the source to the destination computer without reliance on earlier exchanges between the source and destination computers and the transporting network.

In the context of computer networking, a “datagram” is a packet of data that is transmitted over a network. It is a unit of data that is transmitted as a whole and is not divided into smaller units during transmission. Datagrams are typically used in connectionless networking protocols, such as the User Datagram Protocol (UDP) in the Internet Protocol Suite.

In a connectionless protocol, each datagram is treated as an independent entity and is transmitted without the need for a dedicated end-to-end connection between the source and destination.

This means that each datagram is transmitted on a “best-effort” basis, and there is no guarantee that it will reach its intended destination. However, this also means that datagrams can be transmitted more quickly than in a connection-oriented protocol, as there is no need to establish a connection before transmitting data.

One of the main advantages of using datagrams is their simplicity. Because they do not require a dedicated end-to-end connection, they are easier to implement and manage than connection-oriented protocols. This makes them well-suited for applications that do not require a high level of reliability, such as real-time audio or video streaming.

In short, a datagram is a unit of data that is transmitted as a whole over a network using a connectionless protocol. It is simple to implement and is well-suited for real-time applications that do not require a high level of reliability.

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A key aspect of datagrams is their size. In most networking protocols, there is a limit on the size of a datagram that can be transmitted. This limit is defined as the Maximum Transmission Unit, or MTU for short.

The MTU determines the maximum size of a datagram that can be transmitted without the need to fragment it into smaller units. If a datagram is larger than the MTU, it must be divided into smaller units, known as fragments, which are then transmitted separately and reassembled at the destination.

Fragmentation can have an impact on the performance of a network. It requires additional processing at both the source and destination and can also result in additional overhead in the form of fragmentation and reassembly headers.

As a result, it is important to select an appropriate MTU size to minimize the need for fragmentation.

Another crucial aspect of datagrams is their addressing scheme. In order to route a datagram to its destination, each datagram must include a destination address. This can be in the form of a MAC address for a local network or an IP address for a wider network, such as the Internet.

Most of the time, datagrams are used with a transport layer protocol, such as the User Datagram Protocol (UDP) or the Transmission Control Protocol (TCP).

The transport layer is responsible for providing end-to-end communication between the source and destination and ensuring that datagrams are delivered reliably. In the case of UDP, the transport layer does not provide any reliability mechanisms and relies on the application layer to handle any necessary retransmissions.

In contrast, TCP provides a reliable transport mechanism by implementing error checking, flow control, and retransmission of lost or corrupted data.

Datagrams are a fundamental building block of many networking protocols. They provide a simple and efficient way to transmit data over a network, but they also have limitations in terms of size and reliability.

By understanding the characteristics and trade-offs of datagrams, network designers and administrators can choose the most appropriate networking protocol for their specific needs.