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Summary

We've used a lot of acronyms during this session. Here they are explained once more, in case you missed some of them:

  • ACK: Acknowledgment
  • (D)DoS: (Distributed) Denial of Service
  • DHCP: Dynamic Host Configuration Protocol
  • DNS: Domain Name System
  • HTML: HyperText Markup Language
  • HTTP(S): HyperText Transfer Protocol (Secured)
  • ICMP: Internet Control Message Protocol
  • IMAP: Internet Access Message Protocol
  • IP: Internet Protocol
  • ISP: Internet Service Provider
  • LAN: Local Area Network
  • MAC: Media Access Control
  • NACK: Not Acknowledged
  • NIC: Network Interface Card
  • OSI: Open Systems Interconnection
  • POP3: Post Office Protocol version 3
  • RTT: Round-Trip Time
  • SMTP: Simple Mail Transfer Protocol
  • SSH: Secure Shell
  • TCP: Transmission Control Protocol
  • TLD: Top-Level Domain
  • UDP: User Datagram Protocol
  • URI: Uniform Resource Identifier
  • URL: Uniform Resource Locator

Here's a short summary of the layers of the TCP/IP stack:

  • Link: Provides us with direct connections to other hosts. Also adds identifiers to NICs in the form of MAC addresses.
  • Internet: Provides routing and identifiers for hosts in the internet, in the form of IP addresses.
  • Transport: Provides connections between processes on different hosts by using ports.
  • Application: Composes the actual message to be delivered to the receiver.

Finally, let's map some of the layers of the TCP/IP stack to the command-line tools we use for each of them:

  • Internet:
    • ping
    • dig
  • Transport:
    • ssh
    • netcat
  • Application: