Chapter 4: Networking and the 4.1 Network Fundamentals 4.2 The 4.3 The World Wide Web 4.4 Protocols 4.5 Security Network Classifications Scope Local area network (LAN) Metropolitan area (MAN) Wide area network (WAN) Ownership Closed versus open Topology (configuration) Bus (Ethernet) Star (Wireless networks with central Access Point) Connection channels Physical or wireless 4-1 4-2 Network topologies Network topologies (continued) 4-3 4-4 Protocols Connecting Networks Rules used for communication Several to be covered in this chapter TCP/IP HTML URL FTP HTTP Repeater: Extends a network Bridge: Connects two compatible networks Switch: Connect several compatible networks Router: Connects two incompatible networks resulting in a network of networks called an internet 4-5 4-6 1
Building a large bus network from smaller ones Routers connecting two WiFi networks and an Ethernet network to form an internet 4-7 4-8 Inter-process Communication The client/server model compared to the peer-to-peer model Client-server One server, many clients Server must execute continuously Client initiates communication Peer-to-peer (P2P) Two processes communicating as equals Peer processes can be short-lived 4-9 4-10 Distributed Systems The Systems with parts that run on different computers enabled by networks Distributed databases E.g., airline reservation system Cluster computing A way of increasing computing power and speed Grid computing Allowing many computers to collaborate during downtime Cloud computing The : An internet that spans the world Original goal was to develop a means of connecting networks that would not be disrupted by local disasters. Today it has shifted from an academic research project to a commercial undertaking. Decentralized, open, distributed Do you know of any examples of this? 4-11 4-12 2
Architecture Bandwidth Service Provider (ISP) Tier-1 Tier-2 Access ISP: Provides connectivity to the Traditional telephone (dial up connection) Cable connections DSL Fiber optic Wireless (with and without access point) Cellular 4-13 Capacity per second through a channel CNET Bandwidth meter http://reviews.cnet.com/bandwidth_meter/7004-7254_7-0.html?tag=tool 4-14 Composition Addressing IP address: pattern of 32 or 128 bits often represented in dotted decimal notation Mnemonic address: Domain names Top-Level Domains com, net, org, edu, uk, au, etc. Domain name system (DNS) Name servers DNS lookup 4-15 4-16 Corporation for Assigned Names & Numbers (ICANN) Domain Name System Allocates IP addresses to ISPs who then assign those addresses within their regions. Oversees the registration of domains and domain names. Must register a domain name with a registrar to have it recorded in a DNS registry (also called a name server) E.g., register.com, active-domain.com, netsol.com 4-17 4-18 3
Demonstrations Traditional Applications Whois (www.netsol.com) Nslookup (zoneedit.com/lookup.html) Electronic Mail (email) Domain mail server collects incoming mail and transmits outing mail Mail server delivers collected incoming mail to clients via POP3 or IMAP File Transfer Protocol (FTP) Telnet and SSH Search engines Portals Database applications Most sites now data driven 4-19 4-20 More Recent Applications World Wide Web Voice Over IP (VoIP) Skype Radio Streaming audio and video YouTube, Netflix Mobile apps Need for computing to be responsive Hypertext and HTTP Browser gets documents from Web server Recall: client-server model Documents identified by URLs 4-21 4-22 A typical URL Hypertext Document Format Encoded as text file Contains tags to communicate with browser Appearance <h1> to start a level one heading <p> to start a new paragraph Links to other documents and content <a href =... > Insert images <img src =... > 4-23 4-24 4
A simple Web page Extensible Markup Language (XML) XML: A language for constructing markup languages similar to HTML A descendant of SGML Opens door to a World Wide Semantic Web 4-25 4-26 Client Side Versus Server Side Package-shipping example Client-side activities Examples: Java applets, JavaScript, Macromedia Flash Server-side activities Common Gateway Interface (CGI) Java Servlets PHP 4-27 4-28 Software Layers Application: Constructs message with address Transport: Chops message into packets Network: Handles routing through the Link: Handles actual transmission of packets The software layers 4-29 4-30 5
Following a message through the 4-31 Packet Switching Packets Small chunks of data Anything that is sent on the gets broken up into packets Routed independently; assembled at destination Compare to the alternative: circuit switching (e.g. telephone system model) Actually connected 100% of the time Monopolize limited resources 32 TCP/IP Protocol Suite TCP/IP The rules for packet switching Transport Layer TCP UDP Network Layer IP (IPv4 and IPv6) Open standard TCP Transfer Control Protocol Break message into data packets Sequence them Reassemble at receiver Detect missing/error packets Packet 1 Packet 2 Packet 3 4-33 Now is the time for all good men to come to the aid of their county. Packet 4 34 TCP/IP (cont.) Security IP Protocol Addresses packets {SENDER: 246.133.251.12 RECIPIENT: 215.121.13.0 SEQUENCE: 1 of 4 DATA: Now is the time f ERROR: 0xFE7C29} Uses IP numbers as addresses E.g. 156.143.143.130 Replaced by domain names for us Routes them through network Routers democracy in action (Cisco Systems) E.g., www.tracert.com Attacks Malware (viruses, worms, Trojan horses, spyware, phishing software) Hacking Denial of service Spam Protection Firewalls Spam filters Proxy Servers Antivirus software 35 4-36 6
Encryption Public-key encryption FTPS, HTTPS, SSL Public-key Encryption Public key: Used to encrypt messages Private key: Used to decrypt messages Certificates and Digital Signatures 4-37 4-38 7