Communication & Internet Technologies Flashcards

Protocols

  • Protocols are essential for communication between computers, acting as agreed-upon rules for data transmission.
  • Protocol implementation can be viewed as a stack, with each layer having its functionality.
  • The TCP/IP protocol suite is a key example.
  • Protocols include HTTP, FTP, POP3, IMAP, SMTP, and BitTorrent, each serving specific purposes.

Protocol Stack

  • Protocols are layered within a protocol stack.
  • Each layer interacts only with adjacent layers through defined interfaces.
  • Layers are serviced by lower layers, with the lowest layer handling hardware.
  • User interaction occurs at the highest level layer.

Internet Protocol Layers (5-Layer Model)

  • Physical: Basic bit-by-bit communication.
  • Data Link: Acts as a correspondent between network and physical layers (e.g., Ethernet/WiFi).
  • Network/Internet: Responsible for data transmission and routing (Internet Protocol).
  • Transport: Divides data into packets, adds source/destination addresses and sequence numbers (TCP, UDP).
  • Application: Provides services to the network layer via the transport layer (e.g., FTP, TELNET, HTTP, SSH).

TCP/IP

  • TCP/IP organizes data packet communication over the internet.
  • Ensures packets contain source, destination, packet sequence, data, and error check information.
  • Breaks down the process into manageable modules, facilitating development and compatibility via decomposition.
  • Uses a four-layer structure.

Key Internet Protocols

  • TCP (Transmission Control Protocol): Ensures safe delivery of messages by creating packets with headers and user data.
  • IP (Internet Protocol): Ensures correct routing over the Internet by adding sender and receiver IP addresses to packets (datagrams).

IP Addresses

  • Every device on the internet has a unique IP address included in data packets.
  • IP addresses can be 32-bit or 128-bit numbers, often represented as four 8-bit numbers (octets) separated by full stops (e.g., 192.168.0.12).
  • DHCP servers often assign IP addresses on local networks.

Application-Layer Protocols

  • FTP (File Transfer Protocol): Used for transferring large files; often employs TCP/IP. Uses client-server relationship, may feature anonymous access.
  • HTTP (Hyper Text Transfer Protocol): Transfers web pages; HTTPS provides secure, encrypted communication.
  • SMTP (Simple Mail Transfer Protocol): Used to send email (push protocol); often requires MIME for attachments.
  • POP3 & IMAP: Used to receive email (pull protocols).
  • VOIP (Voice over Internet Protocol): Enables voice conversations over the internet using digital data packets.
  • UDP (User Datagram Protocol): Connectionless service without handshaking or congestion control, suitable for real-time applications.

Peer-to-Peer (P2P) File Sharing

  • P2P architecture has no central structure; peers act as both clients and servers.
  • BitTorrent: A protocol for fast file sharing using torrent files and trackers.
  • Peers download and upload chunks simultaneously, prioritizing rare chunks.
  • Peers are encouraged to upload by rewarding those who provide regular downloads; leechers may be 'choked'.
  • Tracker servers maintain lists of connected computers, sharing IP addresses.
  • "Leechers" download, while "seeders" upload complete files.

Router

  • Connects two or more networks (LAN to WAN).
  • Routers use routing tables to choose the next target host.
  • Routing tables include details to find the shortest path available.

Packet Switching and Circuit Switching

  • Circuit Switching: Establishes a dedicated channel before communication. The channel is reserved, Quality of Service is guaranteed (QoS).
  • Packet Switching: Does not require an initial connection; channel is available to multiple users but can experience congestion. Packets include header containing addresses of source and destination.
  • Datagram: Each packet is treated independently and can take any route, possibly arriving out of order or missing.
  • Virtual Circuit: A preplanned route is established before transmission; each packet contains a virtual circuit identifier (VCI).