1. CHAPTER 2 PCs on the Internet Suraya Alias

2. The TCP/IP Suite of Protocols Internet applications – client/server applications The client requested data from the server Example : a home user (client) requesting the facebook web page from facebook application web server (web host) Example of web servers : Apache HHTP Server and Internet Information Services (IIS) The server application is installed as a service in a computer Using IP and Ports addresses to identify services Each services (email, web server) is addressed using unique port number since they access to the same IP Address So each server applications listens to the assigned port Example: web server is assigned port 80, email server is port 25 So the web server will communicate at 136.60.30.5:80 and the email server using 136.60.30.5:25

3. Common TCP/IP port assignment PortProtocolServiceDescription 20FTP File transfer data 21FTP File transfer data 22SSHSecure Shell Remote control to a networked computer 23Telnet Used by UNIX computers to control a computer remotely 25SMTPE-mail Simple Mail Transfer Protocol 80HTTPWeb server World Wide Web Protocol 109POP2E-mail Post Office Protocol,v2, used by client to receive email 110POP3E-mail Post Office Protocol,v3, used by client to receive email 119NNTPNews server New server, used for newsgroup 143IMAPE-mail Internet Message Access Protocol, newer than POP3 443HTTPSWeb server HTTP with security includes authentication and encryption

4. TCP/IP protocol layers Web serverEmailChat roomFTP Applications HTTPSMTP, POP IRCFTP TCP Or UDP IP, ARP,RARP,RIP or ICMP Ethernet, PPP over telephone lines, Token Ring, FDDI or wireless Cabling/telephone lines TCP/IP suite of protocols Applications Operating System Physical Network

5. Application Protocols Four common applications that uses the internet is Web browser, email, chat and FTP Application Programming Interface (API) is used by the OS in order to request or send data to another host For web browser and web servers, the OS generates Hypertext Transfer Protocol (HTTP) in order to communicate A session is established after the response is received from the web server

6. TCP/IP protocols used by OS for network communication When a web browser make a request for a data to the web server, a packet is created and is ready to be delivered Transmission Control Protocol (TCP) is the TCP/IP protocol that guarantees the packet is delivered and will resend if it fails It is also called connection-oriented protocol and used for email and web browsers, s While UDP (User Datagram Protocol) does not guarantee delivery by first connecting and checking whether data is received or not Its called a connectionless protocol or best-effort protocol

7. TCP/IP protocols used by OS for network communication Next, TCP & UDP pass the request to IP (Internet Protocol) to breaks up and reassemble data into packets and routing them to respective destination Other available network protocols; ARP (Address resolution Protocol) Responsible to locate a host on a local network RARP (Reverse Address resolution Protocol) Responsible for discovering the Internet Address of a host on a local network ICMP (Internet Control Message Protocol) Responsible for communicating problem with transmission Example of TCP/IP utilities ARP, Getmac, IPconfig,FTP,NBstat,Netstat, NSLookup Ping, route, telnet, tracert, winipcfg

8. TCP/IP Utilities

9. Connecting to the Internet Computer or Local network can connect to Internet by ISP using following technologies; 1. Regular phone line - requires internal, external modem 2. Cable modem - uses cable lines 3. DSL (Digital Subscriber Line) – uses copper phone lines, same phone line for voice and DSL, Asymmetric SDL,Symmetric DSL 4. ISDN (Integrated Services Digital Network) 5. Satellite access 6. Wireless access

10. Using Router Router is a device that manages traffic between two network 2 major disadvantages of using host pc in sharing internet connection 1. Host comp must always be turned on 2. Security issues Advantages of using router rather than host pc 1. Less bottleneck of the host pc 2. Internet access not dependable to host pc 3. Router can serve as hardware firewall, better protection that software firewall 4. Provide additional features such as DHCP server, switch, wireless access point.

11. Virtual Private Network (VPN) Solution for securing private data travelling over a public network is using VPN VPN works by using encrypted data packets between a private network a computer somewhere in the internet Security methods with VPN User accounts and passwords are required, when the remote users sends data to the authentication server, the data is encrypted using protocols such as EAP (Extensible Authentication Protocol), SPAP (Shiva Password Authentication Protocol) and others After the user is authenticated, a tunnel is created so that all data sent between the user and the company is strongly encrypted There are 4 tunnels protocol that can be used PPTP (Point to Point Tunneling Protocol) - weakest L2TP (Layer Two Tunneling Protocol) – strongest is combined with IPSec SSL (Secure Socket Layer ) IPSec (IPSecurity)

12. Supporting Internet Client Web browser is a s/w application on client PC used to request web pages from the web server on the internet URL (Uniform Resource Locator) http://www.facebook.com/photo/mypic.php Protocol Domain Name Network Name Host Name folderfilename

13. Using Secured Web Connection Using HTTPS (HTTP Secure) For Internet Banking or private business HTTP over SSL (Secure Socket Layer) or TSL (Transport Layer Security) The purpose of these security protocols is to prevent others from the internet to eavesdropping on data or change the data SSL – uses an encryption system that uses a digital certificate. Public Keys are secret codes used to encrypt and decrypt the data. A digital certificate, or digital ID, digital signature is a code assigned to you by a certificate authority such as Verisign that uniquely identifies you on the net and includes a public key TSL – improved version of SSL