Practical TCP/IP and Ethernet Networking- P29: The transmitter encodes the information into a suitable form to be transmitted over the communications channel. The communications channel moves this signal as electromagnetic energy from the source to one or more destination receivers. The channel may convert this energy from one form to another, such as electrical to optical signals, whilst maintaining the integrity of the information so the recipient can understand the message sent by the transmitter | 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 .
