Networking & the Internet Study Guide

The Client-Server Model

• A network is a series of interconnected devices that can communicate with one another.

• In the client-server model:

  • The client is you.

  • The server accepts the request and gives the info back.

Packet Analysis

• An IPv4 is a unique identifier for a network made up of four numbers separated by periods.

• A MAC address is a unique identifier for a physical device.

• The protocol (or set of instructions) that establishes a connection between two devices and breaks up large pieces of data for transport is known as TCP/IP.

• A packet is a chunk of information sent from one computer to another.

• The correct order of the TCP three-way handshake is as follows:

  • synchronize

  • Synchonize-acknowledge 

  • acknowledge

• Why are there three messages in the handshake? Because it’s making sure that both computers can hear each other.

• The OSI model provides a universal framework of 7 layers for how information should be broken up to be sent over the Internet.

• Working from the top down:

  • Application, Session, & Presentation Layers - coordinates the start/end of a session, the version and syntax of data, and the type of application being used

  • Transport Layer - what ensures packets are recombined in the right order, where TCP comes in

  • Network Layer - where routing across the Internet occurs, which connects one IP address to another

  • Data Link Layer - establishes what machine in a network actually gets the data through the MAC address

  • Physical Layer - communication medium and what signals are transmitted

• The protocol that governs how web pages and web data are sent over the Internet is known as HTTP.

• What’s the difference between GET and POST requests? GET transfers data in the URL, POST transfers it in the packet

• Transport Layer Security (TLS) is a cryptographic protocol that encrypts information sent over the Internet.

• HTTPS is HTTP wrapped in TLS.

• A web server will send a SSL certificate to verify their identity.

• The Domain Name System (DNS) Translates a URL into an IP address.

• How are IPv4 and IPv6 addresses related? How are they different? They both point to the same resources, but IPv6 is written differently so we don’t run out of them like IPv4.

Intrusion Detection Evasion

• Network enumeration is the process of mapping out a network and all the services running on it.

• A firewall uses rules to filter out traffic based on where it’s coming from, what port it’s trying to access, and protocol types..

• How did we evade a firewall? By changing our transmission unit size. We made the packets smalll enough to get through the holes of the net

• Disguising an unknown IP address as a known and trusted address is known as spoofing.

• What were the limitations of our IP spoofing attempt? We couldn’t get any traffic back.