Connectionless Services

A Connectionless service is a data communication between two nodes where the sender sends data without ensuring whether the receiver is available to receive the data. Here, each data packet has the destination address and is routed independently irrespective of the other packets. Thus the data packets may follow different paths to reach the destination. There’s no need to setup connection before sending a message and relinquish it after the message has been sent. The data packets in a connectionless service are usually called datagrams.

Protocols for connectionless services are −

• Internet Protocol (IP)
• User Datagram Protocol (UDP)
• Internet Control Message Protocol (ICMP)

Connectionless services may be of the following types −

• A datagram with Acknowledgement: e.g. text messages with delivery report
• Request-Reply: e.g. queries from remote databases

Advantages of Connectionless Services

• It has low overhead.
• It enables to broadcast and multicast messages, where the sender sends messages to multiple recipients.
• It is simpler and has low overhead.
• It does not require any time for circuit setup.
• In case of router failures or network congestions, the data packets are routed through alternate paths. Hence, communication is not disrupted.

Disadvantages of Connectionless Services

• It is not a reliable connection. It does not guarantee that there will not be a loss of packets, wrong delivery, out – of – sequence delivery or duplication of packets.
• Each data packet requires longer data fields since it should hold all the destination address and the routing information.
• They are prone to network congestions.