Practical TCP/IP and Ethernet Networking- P15: One of the great protocols that has been inherited from the Internet is TCP/IP and this is being used as the open standard today for all network and communications systems. The reasons for this popularity are not hard to find. | 7 Host-to-host transport layer protocols Objectives When you have completed this chapter you should be able to Explain the basic functions of the host-to-host layer Explain the basic operation of TCP and UDP Explain the fundamental differences between TCP and UDP Decide which protocol TCP or UDP to use for a particular application Explain the meaning of each field in the TCP and UDP headers The host-to-host communications layer also referred to as the service layer or as the transport layer in terms of the OSI model is primarily responsible for ensuring end-to-end delivery of packets transmitted by the Internet protocol IP . This additional reliability is needed to compensate for the lack of reliability in IP. There are only two relevant protocols residing in the host-to-host communications layer namely TCP transmission control protocol and UDP user datagram protocol . In addition to this the host-to-host layer includes the APIs application programming interfaces used by programmers to gain access to these protocols from the process application layer. Host-to-host transport layer protocols 123 OSI LAYER I PROTOCOL IMPLEMENTATION PROCESS APPLICATION File Transfer File Transfer Protocol FTP ML-STD1780 RFC 859 Electronic Mail Srrple Mail Transfer Rotocol SMTP ML-STD 1781 RFC 821 Ta min al Emulation TELIET Protocol ML-STD 1782 RFC854 Fie Transfer Trivial File Transfer Protocol RFC 783 diert Saier Sun Mciosystems. I fet Aork file Systems Rotocol RFCs 1014. 1057 1094 Netwoik Management Smple 1 fetiaork Nfenagement Protocol 9 f-Pi RFC 1157 HOST TO HOST TCP LDP INTERNET Address Resolution ARPRFC826 RARPRFC903 Internet Rotocol IP ML STD 1777 RFC 791 Internet Cbnbd Message R otocol ICM RFC 792 NE TWORK INTERFACE ITetwjik Interface Cads Ethanet. Token-Rng. ARQ-ET. RAI land WAI. RFC894. 1042 . 1201 aid others Figure TCP and UDP within the ARPA model TCP transmission control protocol Basic functions TCP is a connection-oriented protocol and is therefore reliable .
