Chapter 3

• HTTP and HTTPS is for website navigation
• HTTP - Hypertext Transfer Protocol
• HTTPS - Secured Hypertext Transfer Protocol
• HTTP - common/widely use. Not secured. Transfer in clear text, meaning not encrypted and vulnerable to anybody
• HTTPS - secured version of HTTP, with security feature. Transfer in encrypted text, meaning text is converted into unreadable code. Use protocols SSL and TLS
• SSL - Secure Sockets Layer
• TLS - Transport Layer Security. successor of SSL
• SSL and TLS use to authenticate the identity of a website by asking SSL certificate
• FTP - File Transfer Protocol
• FTP is used to transfer files between computers and servers over network. NOT secured
• Ways to transfer file using FTP : internet browser, FTP client
• SFTP - Secure File Transfer Protocol. Secure version of FTP
• FTP and SFPT is connection oriented protocols meaning needs to establish connection. They used TCP for file transfer - reliability
• TFTP - Trivial File Transfer Protocol. transferring over local area network and not over network. Connectionless oriented protocol that used UDP for speed
• DHCP - Dynamic Host Configuration Protocol. Allows a network to assign IP addresses to devices automatically.
• 2 ways computer can be assigned an IP address: Static IP and Dynamic IP
• Static IP - user assigns IP manually on every device. Fixed
• Dynamic IP: computer gets IP automatically, performed by DHCP
• Computer request an IP then the DHCP server assign an IP Address from its pool and assign a lease time
• DNS - Domain Name System - converts human readable domain names into IP addresses
• SMTP - Simple Mail Transfer Protocol. used for sending email. uses TCP protocol
• POP3 and IMAP is used to retrieve email from email server
• POP3 - Post Office Protocol 3 . download email to your device from mail server and delete the copy from the server once downloaded. Doesn't synch devices. Viewable without internet
• IMAP - Internet Message Access Protocol. View email that is on the server from multiple device. Synch all devices
• Type Domain name.

  Web browser will check its cache.

  First to visit is the DNS resolver server or your ISP check its cache.

  Then the root server.

  Then the root server will direct the dns resolver to Top Level Domain (.com)

  Authoritative Name server

  Resolver receive IP to initiate connection and store it to cache memeory and computer browser
• SMTP terms:

  Sender & Receiver - Mail User Agent

  SMTP Server - Mail Transfer Agent

  POP3 - Mail Delivery Agent

  IMAP - Mail Access Agent
• Root server - root of DNS Hierarchy, it has 13 location that is handled by 12 organization 2 of which was by verisign. root server is not the boss, just part of the internet that knows where to direct the resolver
• Top Level Domain - which stores the address information and directs the resolver to Authoritative Name server
• Authoritative Name server that is responsible for knowing all about the domain name including its ip address, retrieve ip address.
• Resolver receive IP to initiate connection and store it to cache memeory and computer browser
• Lossless compression reduces the size of a file without losing any data.
• Lossless compression achieves compression by eliminating redundant information within the data. When the compressed file is decompressed, the original data is entirely recovered, bit for bit.
• Lossy compression reduces the size of a file by removing certain information deemed less essential.
• While lossy compression can achieve higher compression ratios compared to lossless methods, it sacrifices some fidelity in the process.
• symmetric encryption, the same key is used for both encryption and decryption. The key must be kept secret and shared securely between the communicating parties.
• Symmetric encryption algorithms are generally faster and more efficient than asymmetric algorithms.
• Asymmetric encryption uses two keys: a public key for encryption and a private key for decryption. The public key can be freely distributed, while the private key is kept secret. Any data encrypted with the public key can only be decrypted with the corresponding private key.
• Asymmetric encryption is slower compared to symmetric encryption due to the complexity of the algorithms involved
• simplex communication, data flows in only one direction, from the sender to the receiver, with no feedback from the receiver to the sender
• half-duplex communication, data can flow in both directions, but not simultaneously. Instead, communication alternates between sending and receiving.