Internet protocol is defined in RFC 791. This protocol works at network layer. The network layer is also called as Internet protocol layer or IP layer. Some one recently asked me why Internet protocol is mentioned as connectionless protocol. We all know that the connection oriented and connection less protocols comes at transport layer, then why IP is called as connection less protocol ? Was it required to be specific about this ?
I did some study and came across this information. Connection less protocols can be anything which does not require prior establishment of channel or links to transfer data. Some of the examples of connection less protocols are HTTP, UDP, IP, ICMP, Ethernet, IPX, NetBEUI etc.
Why HTTP 1.0 is considered as connection less protocol even if it uses TCP ? Well it did not keep track earlier requests and every request is new request for it. HTTPS is connection oriented protocol.
Now IP , why IP is connection less protocol ? It is mentioned in RFC 1122
All Internet transport protocols use the Internet Protocol (IP) to carry data from source host to destination host.IP is a connectionless or datagram internetwork service, providing no end-to-end delivery guarantees. Thus, IP datagrams may arrive at the destination host damaged,duplicated, out of order, or not at all. The layers above IP are responsible for reliable delivery service when it is required. The IP protocol includes provision for addressing, type-of-service specification, fragmentation and reassembly, and security information.The datagram or connectionless nature of the IP protocol is a fundamental and characteristic feature of the Internet architecture. Internet IP was the model for the OSI Connectionless Network Protocol [INTRO:12].
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