Transcript web server
CHAPTER 2 PCs on the Internet Suraya Alias 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 The TCP/IP Suite of Protocols The TCP/IP Suite of Protocols 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 IP Address Port Common TCP/IP port assignment Port Protocol Service Description 20 FTP FTP File transfer data 21 FTP FTP File transfer data 22 SSH Secure Shell 23 Telnet Telnet Used by UNIX computers to control a computer remotely 25 SMTP E-mail Simple Mail Transfer Protocol 80 HTTP Web server 109 POP2 E-mail Post Office Protocol,v2, used by client to receive email 110 POP3 E-mail Post Office Protocol,v3, used by client to receive email 119 NNTP News server 143 IMAP E-mail Internet Message Access Protocol, newer than POP3 443 HTTPS Web server HTTP with security includes authentication and encryption Remote control to a networked computer World Wide Web Protocol New server, used for newsgroup TCP/IP protocol layers Applications Email HTTP SMTP, POP Chat room FTP IRC FTP TCP Or UDP IP, ARP,RARP,RIP or ICMP Ethernet, PPP over telephone lines, Token Ring, FDDI or wireless Cabling/telephone lines Applications TCP/IP suite of protocols Web server Operating System Physical Network Four common applications that uses the internet are: ◦ 1)Web browser 2) email 3) chat and 4) 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 Application Protocols When a web browser make a request for a data to the web server, a packet is created and is ready to be delivered TCP (Transmission Control Protocol ) ◦ is the TCP/IP protocol that guarantees the packet is delivered and will resend if it fails so the connection is quite slow ◦ It is also called connection-oriented protocol and used for email and web browsers 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 ◦ Usually used for games that require constant fast transmission of data (such as player coordinates in a fast-paced shooter) 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 TCP/IP protocols used by OS for network communication Example of TCP/IP utilities ARP, Getmac, IPconfig,FTP,NBstat,Netstat, NSLookup Ping, route, telnet, tracert, winipcfg TCP/IP Utilities 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) – 1. 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 Connecting to the Internet Router is a device that manages traffic between two network 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. Using Router 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 Domain Name Protocol Host Name Network Name folder filename Supporting Internet Client Using HTTPS (HTTP Secure) https://www.maybank2u.com.my/mbb/m2u/common/M 2ULogin.do?action=Login 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 Using Secured Web Connection Solution for securing private data travelling over a public network or internet is using VPN VPN works by using encrypted data packets between a private network a computer somewhere in the internet Virtual Private Network (VPN) 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 Virtual Private Network (VPN) ◦ There are 4 tunnels protocol that can be used 1. PPTP (Point to Point Tunneling Protocol) ◦ extends the Point to Point Protocol (PPP) standard for traditional dial-up networking. ◦ PPTP is best suited for the remote access applications of VPNs, but it also supports LAN internetworking. 2. SSL (Secure Socket Layer) 3. IPSec (IPSecurity) is a protocol suite for securing Internet Protocol (IP) communications by authenticating and encrypting each IP packet of a data stream. IPsec also includes protocols for establishing mutual authentication between agents at the beginning of the session and negotiation of cryptographic keys to be used during the session 4. L2TP (Layer Two Tunneling Protocol) ◦ strongest if combined with IPSec ◦ It does not provide any encryption or confidentiality by itself; it relies on an encryption protocol that it passes within the tunnel to provide privacy Virtual Private Network (VPN)