Chapter 4 Internet Architecture

Awad –Electronic Commerce 1/e © 2002 Prentice Hall 2 OVERVIEW What is a Network? IP Addresses Networks Information Transfer Cable Types Key Components of a Network Factors in Designing a Network Network Management System Internet Architecture

Awad –Electronic Commerce 1/e © 2002 Prentice Hall 3 WHAT IS A NETWORK? A connection between at least two computers for the purpose of sharing resources Types: –Local Area Networks (LANs) –Wide Area Networks (WANs) –Metropolitan Area Networks (MANs) Internet Architecture: What is a Network?

Awad –Electronic Commerce 1/e © 2002 Prentice Hall 4 PEER-TO-PEER NETWORK Computers linked together as equals No centralized control Share resources on the same network in any way & at any time Promotes institutionalized chaos < 10 computers Internet Architecture: What is a Network?

Awad –Electronic Commerce 1/e © 2002 Prentice Hall 5 PEER-TO-PEER NETWORK (CONT.) Benefits –Easy to install/configure –Inexpensive –Users able to control their own resources –Independent from a dedicated server –No need for a network administrator Drawbacks –Security problems –Performance suffers when a computer is accessed –Difficult to have backup –Decentralized logon passwords –No centralized data management Internet Architecture: What is a Network?

Awad –Electronic Commerce 1/e © 2002 Prentice Hall 6 CLIENT/SERVER NETWORK Server – designed to address a clients request Client – any computer connected to the server within a network Allow authorized user to access any programs/application residing on the server Internet Architecture: What is a Network?

Awad –Electronic Commerce 1/e © 2002 Prentice Hall 7 CLIENT/SERVER NETWORK (Contd) Benefits –Centralized security control –Simpler network administration than peer-to- peer network –Centralized password –More scalable –Ideal for computers that are apart Drawbacks –Network failure = clients are helpless –Specialized staff are needed –Higher costs Internet Architecture: What is a Network?

Awad –Electronic Commerce 1/e © 2002 Prentice Hall 8 IP ADDRESSES A host number to identify itself to other hosts Consists of strings of 32 bits E.g = Host Name –Human-friendly Internet addresses –E.g. ema3z.mcintire.virginia.edu Internet Architecture: IP Addresses

Awad –Electronic Commerce 1/e © 2002 Prentice Hall 9 NETWORKS Network vs. Local Networks are classified by three sizes: Internet Architecture: Networks ClassBeginning Bit Bits in remainder of network part # of bits in local part Max. # of networks Max. # of hosts in network A million B ,00065,000 C million254

Awad –Electronic Commerce 1/e © 2002 Prentice Hall 10 NETWORKS (Contd) Zones –Three-letter kind (com, gov, edu) –Two-letter kind (ca, uk, jp) –New general-purpose zones (firm, store) Internet Architecture: Networks

Awad –Electronic Commerce 1/e © 2002 Prentice Hall 11 INFORMATION TRANSFER Packet –Grouping of data for transmission on a network –Large messages are split into a series of packets for transmission Protocol –A rule governing how communication should be conducted –Internet Protocol Set of rules used to pass packets Internet Architecture: Information Transfer

Awad –Electronic Commerce 1/e © 2002 Prentice Hall 12 INFORMATION TRANSFER (Contd) Open Systems Interconnection (OSI) –A layered approach to networking –Each layer handles a different portion of the communication process Internet Architecture: Information Transfer

Awad –Electronic Commerce 1/e © 2002 Prentice Hall 13 OSI REFERENCE MODEL Internet Architecture: Information Transfer LayerInfo TransactedTCP/IP Protocols ApplicationApplication messagesHTTP, FTP, SNMP PresentationCompressed data SessionSession messages TransportMultiple packetsTCP NetworkPacketsIP Data LinkFramesEthernet, PPP PhysicalBitsWiring, cables

Awad –Electronic Commerce 1/e © 2002 Prentice Hall 14 OSI REFERENCE MODEL (Contd) Application Layer –Defines requests & response formats –Standard: HTTP Governs requests & response between browser & web server application program Other standards: SMTP, POP HTML-compatible –File Transfer Protocol (FTP), Simple Network Management Protocol (SNMP), Domain Name Service (DNS) Internet Architecture: Information Transfer

Awad –Electronic Commerce 1/e © 2002 Prentice Hall 15 OSI REFERENCE MODEL (Contd) Presentation Layer –Converts data into a format the receiving application can understand Session Layer –Exchanges data for the duration of session –Keeps track of the status of exchange –Ensures only designated parties are allowed to participate in the session –Enforces security protocols for controlling access Internet Architecture: Information Transfer

Awad –Electronic Commerce 1/e © 2002 Prentice Hall 16 OSI REFERENCE MODEL (Contd) Transport Layer –Manages the transmission of data across a network –Transmission Control Protocol (TCP) Specifies how two host computers will work together Flow control Sequence assurance Reliability & integrity Internet Architecture: Information Transfer

Awad –Electronic Commerce 1/e © 2002 Prentice Hall 17 OSI REFERENCE MODEL (Contd) Internet Layer –Routes messages across multiple nodes for delivery –Handles network congestion to minimize performance problems –Internet Protocol (IP) Standard for routing packets Internet Architecture: Information Transfer

Awad –Electronic Commerce 1/e © 2002 Prentice Hall 18 OSI REFERENCE MODEL (Contd) Data Link Layer –Packages data into frames for delivery –Point-to-point (PPP) Framing – mark boundary between packets Error detection –Ethernet Physical Layer –Converts bits into signals for outgoing messages & signals into bits for incoming messages Internet Architecture: Information Transfer

Awad –Electronic Commerce 1/e © 2002 Prentice Hall 19 CABLE TYPES Twisted-Pair Cable Unshielded Twisted Pair (UTP) Shielded Twisted Pair (STP) Optical Fiber Coaxial Cable Wireless Technology Internet Architecture: Cable Types

Awad –Electronic Commerce 1/e © 2002 Prentice Hall 20 TWISTED-PAIR CABLE Consists of two pairs of insulated copper wires twisted around each other Advantages –Protect against cross talk & interference –Easy to add computers to network –Well understood technology –Less expensive Disadvantages –Susceptibility to noise –Least secure –Distance limitations –Requires more expensive hubs Internet Architecture: Cable Types

Awad –Electronic Commerce 1/e © 2002 Prentice Hall 21 UNSHIELDED TWISTED PAIR (UTP) Pair of wires do not have the shielding against electrical interference Advantages –Less expensive –Easy to install Disadvantages –Vulnerable to electromagnetic interference & crosswalk –Subject to attenuation Internet Architecture: Cable Types

Awad –Electronic Commerce 1/e © 2002 Prentice Hall 22 SHIELDED TWISTED PAIR (STP) An electrically grounded woven copper mesh wrapped around each twisted pair Advantage –Reduces electromagnetic interference (EMI) Disadvantage –Makes the wiring thick and is difficult to maintain Internet Architecture: Cable Types

Awad –Electronic Commerce 1/e © 2002 Prentice Hall 23 OPTICAL FIBER Uses light rather than voltage to indicate ones and zeros Advantages –High speed transmission –High security –Smallest in size –Supports voice & video data Disadvantages –Expensive –Difficult to install –Require two cables to transmit & receive data –Require special connections Internet Architecture: Cable Types

Awad –Electronic Commerce 1/e © 2002 Prentice Hall 24 COAXIAL CABLE Copper center shielded by a plastic insulating material Advantages –Transmits up to 10Mbps over 500m –Easy to install –Low maintenance –Good resistance to noise over long distances Disadvantages –Inflexible –Low security –Limited distance Internet Architecture: Cable Types

Awad –Electronic Commerce 1/e © 2002 Prentice Hall 25 WIRELESS TECHNOLOGY Microwave –Connect LANs in separate buildings Radio waves –No distance limitations –Susceptible to atmospheric and electronic interference –Subject to government regulations Infrared transmissions –Interference from bright light Internet Architecture: Cable Types

Awad –Electronic Commerce 1/e © 2002 Prentice Hall 26 KEY COMPONENTS OF A NETWORK Network Interface Card (NIC) Hubs & Switches Routers Gateways Internet Architecture: Key Components of a Network

Awad –Electronic Commerce 1/e © 2002 Prentice Hall 27 NETWORK INTERFACE CARD Installed in a slot with a cable plugged into the back Plugged into a wall jack connection or into the hub/switch directly Modem –Converts digital signals into analog form for transmission and incoming analog signals into digital signal across the telephone line Internet Architecture: Key Components of a Network

Awad –Electronic Commerce 1/e © 2002 Prentice Hall 28 HUBS & SWITCHES Hub –Operates at Physical Layer –Acts as a connecting point –Passive, active, and intelligent hubs Switch –Offers direct connection to a particular PC –Available for almost every OSI level Internet Architecture: Key Components of a Network

Awad –Electronic Commerce 1/e © 2002 Prentice Hall 29 ROUTERS Operate at Internet Layer Evaluate network traffic and stop local traffic from causing congestion Filter out packets that need not be received Expensive & difficult to operate Internet Architecture: Key Components of a Network

Awad –Electronic Commerce 1/e © 2002 Prentice Hall 30 GATEWAYS Special-purpose computer allowing communications between dissimilar systems on the network Operate at Application Layer primarily Difficult to install & configure Expensive Internet Architecture: Key Components of a Network

Awad –Electronic Commerce 1/e © 2002 Prentice Hall 31 FACTORS IN DESIGNING A NETWORK Location Capacity Distance limitations Cost Potential growth Security Internet Architecture: Factors in Designing a Network

Awad –Electronic Commerce 1/e © 2002 Prentice Hall 32 FACTORS IN SELECTING NETWORK ARCHITECTURE Hardware requirements Software requirements Disaster recovery & fault-tolerance requirements Corporate culture and organizational factors Internet Architecture: Factors in Designing a Network

Awad –Electronic Commerce 1/e © 2002 Prentice Hall 33 NETWORK MANAGEMENT SYSTEM Manager Managed Nodes Objects Management Information Base (MIB) Requests & responses Internet Architecture: Network Management System

Chapter 4 Internet Architecture