Chapter 3 Protocols and the TCP/IP Suite

3.1 The Need for a Protocol Architecture need for a standard communication tasks by layers architecture peer protocol: a set of rules or conventions to exchange data syntax semantics timing 2

3.2 TCP/IP Protocol Architecture architecture for ARPANET packet switching network funded by DARPA Internet standards by Internet Activities Board (IAB) 3

TCP/IP Layers three agents of communication applications: distributed applications, e.g., e- mail and file transfer computers: supports multiple applications at a time networks 4

communication tasks organized into five layers physical layer network access layer internet layer host-to-host (or transport) layer application layer physical layer physical interface between computer and network 5

network access layer data exchange between a computer (end system) and the network from source to destination computer within a network requires destination address and possibly priority internet layer transfer of data over multiple interconnected networks routing across multiple networks internet protocol (IP) 6

host-to-host or transport layer independent of the network type and the application type collection of functions for reliable data exchange assurance of delivery, correctness, and correct order transmission control protocol (TCP) application layer to support the various user applications a separate module needed for each different type of application 7

Operations of TCP and IP network comprised of subnetworks network access protocol: sending data within a subnetwork or to routers IP: moving data to a destination via routers TCP: reliable data transfer from source to destination two levels of addressing 8

TCP segment segmented user data + control information (TCP header: port, sequence number, checksum) IP datagram TCP segment + control information (IP header: host address) packet or frame IP datagram + control information (network header: subnetwork address, priority) 10

router stripping network header checking destination host address sending it as another datagram 11

TCP/IP Applications simple mail transfer protocol (SMTP) file transfer protocol (FTP) two connections: control and data transfer control connection for user access TELNET remote logon 12

3.3 The OSI Model International Standardization Organization (ISO) Open Systems Interconnection (OSI) reference model open denotes the ability of connecting two systems conforming to the standards Overall Architecture layering issues of layering 13

OSI model as a framework for standardization TCP/IP as a de facto standard 17

Physical Layer: physical interface between devices and the rules for passing bits from one to another RS-232-C Data Link Layer: make the physical link reliable provide means to activate, maintain, and deactivate the link error detection and control HDLC (High-level Data Link Control) 18

Network Layer: transfer of information between end systems across some type of network relieving higher layers of the need to know what types of switching and data transmission are used specification of destination address and request for network facilities such as priority 19

a direct point-to-point link between stations stations connected across a single network such as a circuit-switching or packet-switching network X.25 covering the lower three layers 20

Transport Layer: reliable information exchange between end systems error-free, in sequence, no loss, no duplication duplication of layer 2 size and complexity depends on the type of the layer 3 22

Session Layer: controlling dialogue between two end systems little or no need for session layer service in many cases dialogue discipline 23

Presentation Layer: define the format of the data to be exchanged data compression data encryption Application Layer: provide means for applications to access the OSI environment management functions support for distributed applications general-purpose applications 24

internet 3.4 Internetworking interconnected set of different subnetworks the Internet intranet end system (ES) intermediate system (IS) bridge: interconnection at OSI layer 2 router: interconnection at OSI layer 3 25