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Week 4
Common Web Technology Protocols

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PROTOCOLS
 A set of rules governing the exchange or transmission of data
between devices.
 Protocols are usually assigned to specific PORTs on a
computer.
 A port is like an extension on a phone system.

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IP, TCP and UDP
 IP – Internet Protocol
 TCP - Transmission Control Protocol
 UDP – User Datagram Protocol

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TCP and UDP
 These two protocols enable communication between all
computers on the internet.
 TCP is the main protocol of the internet. It needs to establish a
connection between the two computers before it will send
information
 UDP does not require the other computer to acknowledge that
it is connected before sending. It just sends. DNS usually uses
UDP

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Common Protocols
 HTTP – Hyper Text Transfer Protocol
 This is the main protocol used well surfing the web to view HTML
(Hyper Text Markup Language) documents.
 Data is sent in the open (not encrypted)
 FTP – File Transfer Protocol
 FTP was the initial protocol for transferring files from computer to
computer.
 User credentials and data are sent in the open (not encrypted)
 Telnet – Teletype Network
 Text base commands / communication between computers.
 User credentials and data are sent in the open (not encrypted)

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Common Protocols
 HTTPs – Hyper Text Transfer Protocol Secure
 This is the main protocol used well surfing the web to view HTML (Hyper Text Markup Language) documents.
 Info is encrypted!
 FTPs – File Transfer Protocol Secure
 Info is encrypted!
 SFTP – Secure File Transfer Protocol
 Uses SSH
 Info is encrypted!
 SSH – Secure Shell
 A secure version of Telnet
 Info is encrypted!
 SCP – Secure Copy Protocol
 Info is encrypted!
 Subset of SSH

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Mail Protocols
 POP3 – Post Office Protocol v3
 Used for coping/retreiving messages from server to computer
 SMTP– Simple Mail Transfer Protocol
 Used for sending messages to a server(s)
 IMAP– Internet Message Access Protocol
 Used to view/manipulate messages on server

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Other Protocols
 DHCP– Dynamic Host Configuration Protocol
 Used for dynamically assigning IP addresses to computers in a
private network.
 DNS– Domain Name System
 Converts or stores IP to Domain Name references

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Protocols - PORTS
Protocol PORT
ftp 21
SSH/scp/FTPs 22
telnet 23
pop3 110
smtp 25
imap 143
http 80
https 443
dns 53

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Other
 URL– Uniform Resource Locator
 Used to specify the address of almost all network resources.
 SSL – Secure Socket Layer
 Additional layer to provide common cryptographic protocol to other
protocols.
 TLS – Transport Layer Security– is basically v3 of SSL

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Common bash commands
 telnet (telnet dca.durhamcollege.ca 80)
 ls : list the content s of the directory (ls –l, ls –la)
 cd : change directory (cd web_design , cd ../)
 pwd : print working directory (pwd)
 ssh : secure shell (ssh –l gubalaray dca.durhamcollege.ca)
 mkdir : make directory (mkdir web_design)
 quota –s : list your disk usage on the server
 man : display manual pages (man ls)
 vi : (vi hello.txt)