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Lectures4-5 - TCP/IP Network Architecture ECE-CSE 861...

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1 ECE & CSE ECE-CSE 861: Introduction to Computer Communication Networks Ness B. Shroff ECE & CSE Lectures 4-5 ECE & CSE TCP/IP Network Architecture The TCP/IP network architecture is a set of protocols that allow communication across diverse networks These protocols form the basic building blocks of the current Internet The TCP/IP architecture consists of four layers Application layer Transport layer Internet layer Network Interface Layer ECE & CSE Application Layer Provides services that can be used by other applications. For example, services have been provided for rlogin , email , ftp , http , etc. The Application layer incorporates the functions of the top three OSI layers (Application, Presentation, and Session) Application layer programs are meant to run directly over the Transport Layer ECE & CSE Transport Layer Provides two basic types of service TCP for reliable connection-oriented transfer of byte streams UDP (User Datagram Protrocol) which consists of best effort connectionless transfer of individual messages provides no mechanism for flow control or error recovery. Question: What would UDP be useful for?
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2 ECE & CSE Internet Layer Handles the transfer of information across multiple networks through the use of gateways or routers. The internet layer is concerned with the transfer of packets between machines (hosts) that are connected to different networks Deals with routing of packets across these networks as well as the control of congestion A key aspect of the Internet layer is the definition of globally unique addresses of hosts that are attached to the Internet ECE & CSE Internet Layer (Cont’d) The connectionless approach makes the system robust : If failures occur, packets are routed around points of failure rather than establish new connections. During congestion, the gateway or router may intentionally or otherwise discard packets (the function of the Internet layer) It is the responsibility of the transport layer for the recovery of packets from such losses. ECE & CSE Network Interface Layer The Network Interface layer is concerned with the network specific aspects of the transfer of packets. It corresponds to parts of the OSI network and data link layers. It provides interfaces for connecting end computer systems to specific networks such as X.25, ATM, etc. (For details on X.25, see Chapter 3 in Schwartz). The network interface layer is particularly concerned with the protocols that access the intermediate networks. At each gateway, the Network Access Protocol (NAP) encapsulates the IP packet into a packet or frame of the underlying network or link (e.g., Ethernet). The IP packet is then recovered at the exit gateway of the given network.
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