CHAPTER 2: COMMUNICATION AND INTERNET TECHNOLOGIES

2.1 PROTOCOLS 

 2.1.1 Introduction to Protocols 

 Definition: A protocol is a set of rules governing communication between computers. It ensures the computers that communicate understand each other. 

 Key Terms: 

 

 MAC Address:  Unique number assigned to each device's networking hardware worldwide 

 IP Address:  Unique number assigned to each node/networking device in a network 

 Port Number:  Software-generated number specifying an application or process communication endpoint 

 

 2.1.2 TCP/IP Protocol Suite 

 Four Layers: 

 

 

 

 

 Layer 

 Purpose 

 

 

 

 

 Application 

 Encodes the data being sent 

 

 

 Transport 

 Breaks data into packets, adds port numbers 

 

 

 Network/Internet 

 Adds IP addresses for routing 

 

 

 Link 

 Adds MAC addresses, handles transmission 

 

 

 Physical 

 Converts to signals for transmission 

 

 

 

 

 

 Data Flow - Sender Side: 

 

 Application Layer:  Encodes data in appropriate format 

 Transport Layer:  Creates packets with port numbers 

 Network Layer:  Adds sender and receiver IP addresses 

 Link Layer:  Formats into frames, adds error checking 

 Physical Layer:  Converts to signals for transmission 

 

 Data Flow - Receiver Side: Reverse of sender side, stripping headers at each layer 

 2.1.3 Key Protocols 

 

 

 

 

 Protocol 

 Full Name 

 Purpose 

 

 

 

 

 HTTP 

 Hyper Text Transfer Protocol 

 Handles transmission of data to/from websites 

 

 

 HTTPS 

 Hyper Text Transfer Protocol Secure 

 Secure HTTP with encryption 

 

 

 FTP 

 File Transfer Protocol 

 Handles file transmission across networks 

 

 

 SMTP 

 Simple Mail Transfer Protocol 

 Sending emails (push protocol) 

 

 

 POP3 

 Post Office Protocol 3 

 Receiving emails (pull protocol) 

 

 

 IMAP 

 Internet Message Access Protocol 

 Advanced email retrieval 

 

 

 BitTorrent 

 - 

 Peer-to-peer file sharing 

 

 

 

 

 

 2.1.4 BitTorrent Protocol 

 Components: 

 

 Torrent File:  Contains details regarding the tracker 

 Tracker:  Server that keeps track of peers 

 Peers:  Users downloading and uploading simultaneously 

 Swarm:  Network of peers sharing the torrent 

 Seeding:  Uploading file after/complete download 

 Leeching:  Downloading without uploading 

 

 How It Works: 

 

 Peers obtain torrent file (small) 

 Torrent file points to tracker 

 Tracker lists all peers in swarm 

 Peers download chunks from each other 

 Peers upload chunks to other peers 

 

 

 2.2 CIRCUIT SWITCHING AND PACKET SWITCHING 

 2.2.1 Circuit Switching 

 Definition: A method of data transfer where a dedicated communication channel is established before transmission begins. 

 Characteristics: 

 

 Dedicated path between sender and receiver 

 Path remains open for entire duration 

 Like traditional telephone system 

 

 Advantages: 

 

 Guaranteed bandwidth 

 Consistent quality 

 No delay from routing decisions 

 

 Disadvantages: 

 

 Inefficient if data is sporadic 

 Connection setup takes time 

 Line unavailable if circuit busy 

 

 Example Use: 

 

 Traditional landline phones 

 

 2.2.2 Packet Switching 

 Definition: A method of data transfer where the message is broken into parts and sent over optimum routes to reach its destination. 

 Characteristics: 

 

 Data divided into packets 

 Each packet can take different route 

 Packets reassembled at destination 

 Used in the Internet 

 

 Advantages: 

 

 Efficient use of network capacity 

 If one route fails, packets can reroute 

 Better for bursty data 

 

 Disadvantages: 

 

 Packets may arrive out of order 

 Variable delays 

 More complex infrastructure 

 

 2.2.3 Router Function 

 Definition: A device that connects two or more computer networks and directs incoming packets to their receiver according to network traffic. 

 Functions: 

 

 Examines packet destination IP address 

 Determines best route for each packet 

 Manages network traffic congestion 

 Connects LAN to WAN 

 

 

 2.3 SSL/TLS 

 2.3.1 SSL and TLS 

 SSL (Secure Socket Layer): 

 

 Provides secure communication 

 Functions between TCP and application layer 

 Creates "socket" for secure connection 

 

 TLS (Transport Layer Security): 

 

 Improved version of SSL 

 Provides encryption, compression, integrity checking 

 

 When to Use: 

 

 Online shopping websites 

 Online banking 

 Any site requiring secure data transmission 

 

 Handshake Process: 

 

 Client sends request to server 

 Server sends digital certificate (includes public key) 

 Client validates certificate 

 Client generates session key, encrypts with server's public key 

 Server decrypts session key 

 Secure session established