Introduction • The Internet is a giant network consisting of interconnected PCs, servers, routers, and switches. • This presentation focuses on a widely accepted definition of a network to mean any series of interconnected information systems and devices.
Background • Network has different meanings. • This presentation focuses on an accepted definition of a network to mean any series of interconnected information systems and devices.
Background • Networks enable computers to interact – exchanging information on everything, from credit card transactions to the latest news and weather.
Background • The Internet is a giant network consisting of interconnected PCs, servers, routers, and switches. • Though data networks vary widely in size and scope, they are generally defined in terms of their architecture, topology, and protocol.
Objectives • Upon completion of this lesson, the learner will be able to: • Describe the basic network architectures. • List and describe basic network protocols. • Explain routing and address translation.
Network Architecture • LANs • WANs
Network Architecture • LANs – Local Area Networks • Are smaller in terms of size and geographic coverage. • Consist of two or more connected devices.
Network Architecture • WANs – Wide Area Networks • Are larger, covering more geographic area. • Consist of two or more systems in geographically separated areas connected by: • Leased lines • Radio waves • Satellite relays • Microwaves • Dial-up connections
WAN and LAN Interconnection Example of a corporate network with interconnected LANs and WANs
Other Terms for Networks • Other terms classify networks based on size and use. • CAN • Intranet • Internet • MAN • SAN • VLAN • Client-Server • Peer-to-Peer
Network Topology • Topology describes how the network is physically or logically arranged. The network’s topology is one of the major components of every network architecture. • The various network topologies are: • Star • Ring • Bus • Mixed
Star • Star – Network components are connected to a central point. Star topology
Bus • Bus – Network components are connected to the same cable, often called “the bus” or “the backbone.” Bus topology
Ring • Ring – Network components are connected to each other in a closed loop with each device directly connected to two other devices. Ring topology
Mixed Topology • Larger networks, such as those inside an office complex, may use more than one topology at the same time. Mixed topology
Topology Definitions • With recent advances in technology, these topology definitions often break down. • Notes Area: • To avoid confusion, many people use topology definitions to apply only to the physical layout of the network, focusing on how the devices are connected to the network.
Network Protocol • A protocol is a format for exchanging or transmitting data between systems. • It defines parameters such as: • Data compression method • Error checking • Mechanisms for systems to signal when they have finished receiving or transmitting data
Common Protocols • AppleTalk – • The communications protocol developed by Apple to connect Macintosh computers and printers.
Common Protocols • Asynchronous Transfer Mode (ATM) – • A protocol based on transferring data in fixed size packets, which helps to ensure that no single data type monopolizes the available bandwidth.
Common Protocols • DECnet – • The protocol developed by Digital Equipment Corporation and used to connect PDP and VAX systems.
Common Protocols • Ethernet – • The LAN protocol developed jointly by Xerox, DEC, and Intel – the most widely-implemented LAN standard.
Common Protocols • Fiber Distributed Data Interface (FDDI) – • The protocol for sending digital data over fiber optic cabling.
Common Protocols • Internet Protocols (IP) – • The protocols for managing and transmitting data between packet-switched computer networks.
Common Protocols • Internetwork Packet Exchange (IPX) – • The networking protocol used by Novell NetWare operating systems.
Common Protocols • Netware – • The LAN protocol developed by Novell Corporation.
Common Protocols • Signaling System 7 (SS7) • The telecommunications protocol used between PBXes to handle tasks such as call setup, routing, and teardown.
Common Protocols • Systems Network Architecture (SNA) – • A set of network protocols developed by IBM, originally used to connect IBM’s mainframe systems.
Common Protocols • Token Ring – • The LAN protocol developed by IBM where systems must possess the network “token” before transmitting data.
Common Protocols • Transmission Control Protocol/Internet Protocol (TCP/IP) • The collection of communications protocols used to connect hosts on the Internet.
Common Protocols • X.25 – • A protocol developed by the Comité Consultatif International Téléphonique et Télégraphique (CCITT) for use in packet-switched networks.
ISO/OSI Reference Model • Communications protocols were developed using the Open System Interconnection (OSI) model. • The OSI Reference Model is an ISO standard for worldwide communications. • It defines a framework for implementing protocols in seven distinct layers.
The Seven Layers The OSI Model
Packets • When data is broken into smaller pieces for transmission, the smaller pieces are called packets.
Standard Packets • A standard packet is crucial in protocol definition. • Without a standard packet structure, systems would not be able to interpret the information coming to them from other systems.
IP Packets • IP packets (datagrams) have two sections: • Header • Data section payload
The Header • The header section contains all the information needed to describe the packet. • What kind of packet it is • (Protocol version number) • How large the header of the packet is • (Packet header length) • How to process this packet • (Type of service – Whether or not to use options (minimize delay, maximize throughput, maximize reliability, and minimize cost) • How large the entire packet is. • A unique identifier so that the packet can be distinguished.
The Header • The header section contains all the information needed to describe the packet. • Whether or not the packet is part of a longer data stream and should be handled relative to other packets. • A description of where the packet fits into the data stream as compared to other packets. • A checksum of the packet header: • To minimize data corruption during transmission.
The Header • The header section contains all the information needed to describe the packet. • Where the packet is from. • Source IP address such as 10.10.10.5 • Where the packet is going. • Destination IP address such as 10.10.10.10
The Header • The header section contains all the information needed to describe the packet. • Option flags that govern security and handling restrictions: • Record the route this packet has taken. • Record timestamps. • The data in the packet.
Packet Illustrated Logical layout of an IP packet
TCP versus UDP • Transmission Control Protocol User Datagram Protocol
TCP versus UDP • As separate protocols, TCP and UDP have their own packet definitions, capabilities, and advantages, but the most important difference between TCP and UDP is the concept of “guaranteed” reliability and delivery.
Connectionless UDP • UDP is a “connectionless” protocol. • Very few error recovery services. • No guarantee of packet delivery.
UDP – Unreliable • UDP is an unreliable protocol. • Used for network services not affected by the occasional lost or dropped packet.
UDP – Efficient • More time and space of a UDP session is dedicated to content or data delivery.
TCP – Connection-Oriented • TCP was designed to allow a reliable connection between two hosts exchanging data. • TCP was designed to ensure that packets are processed in the order they were sent.
TCP Packet Sequence • Each packet has a sequence number to show where the packet fits into the conversation. • Using sequence numbers, packets can arrive in any order and at different times. • The receiving system will still know the correct order for processing the packets.
TCP Packet Sequence • The sequence numbers let the receiving system know if packets are missing. • The receiving system can then request re-transmission of packets from the sender to fill any gaps.
TCP Three-Way Handshake TCP’s three way handshake • The TCP protocol requires that systems follow a specific pattern to establish communications. • The “three-way handshake” consists of a sequence of steps.