Datagram Packet Switching

Datagram Packet Switching

Datagram services treat each packet as an independent message. Each packet is routed through the internetwork independently, and each switch node determines which network segment should be used for the next step in the packet’s route. This capability enables switches to bypass busy segments and take other steps to speed packets through the internetwork (refer to Figure 2.6).

Datagrams are frequently used on LANs. Network layer protocols are responsible for delivering the frame to the appropriate network. Then, because each datagram includes destination address information, devices on the local network can recognize and receive appropriate datagrams.

Packet switching meets the need to transmit large messages with the fairly small frame size that can be accommodated by the Physical layer. The Network layer is responsible for fragmenting messages from upper layers into smaller datagrams that are appropriate for the Physical layer. The Network layer also is responsible for reconstructing messages from datagrams as they are received.