TCP/IP Stack

Question 1

How many layers does the TCP/IP stack have?
(for our purposes)

Answer 1

4

Question 2

What is the first layer called, what 1 thing happens here and what 5 protocols are found here?

Answer 2

The application layer
- This is where applications such as email and web browsers operate
- HTTP, HTTPS, FTP, SMTP, IMAP

Question 3

What is the second layer called, what 3 things happen here and what 2 protocols are found here?

Answer 3

The transport layer
- Sets up communication between two hosts, agreeing on things like language and packet size
- Protocols use port numbers to track sessions
- Once connection is made, it adds number/sequence, the number of packets and the port number to each packet
- TCP, UDP

Question 4

What is the third layer called, what 3 things happen here and what 1 protocol is found here?

Answer 4

The internet layer
- Gives address to and packets the information, then routes them across a network
- Gives each packet a source and destination IP address
- Creates a socket (IP address + port)
- IP

Question 5

What is the fourth layer called and what 4 things happen here. No protocols are found here

Answer 5

The link layer - this is the physical connection between devices
- Network hardware and connection port standards, operating systems and device drivers are here
- Transmission media include twisted pair, copper, fiber and Wi-Fi
- Responsible for adding the source and destination MAC address
- When transmitting data on a WAN, the MAC addresses change every hop on the route

Question 6

What are the advantages of the TCP/IP stack?

Answer 6

• It reduces a complex problem into smaller sub problems
• Devices can be manufactured to operate at a particular layer
• Products from different vendors will work together

Question 7

Why do we need a MAC and IP address?

Answer 7

Because when data is transmitted over a LAN, only the link layer is needed (however in practice it is treated as a WAN)

Question 8

How are web pages fetched over the internet?

Answer 8

• User requests a URL via the browser
• The browser sends the domain name to a domain name server (DNS)
• The DNS maps the domain name to an IP address and sends it back
• A GET request for the web page can now be sent to the web server using the IP address
• The requested page is returned to the browser

Question 9

How does a DNS request work?

Answer 9

• A human readable URL is sent to the DNS resolver server
• The server queries a DNS root name server, which gives the address of the top level domain server (TLD) (for example there is one for .com domains)
• The resolver makes a request to the TLD server, which gives the IP address of the domain’s name server (e.g. Google.com)
• The IP address of the website is then returned to the resolver
• The DNS resolver returns the IP address of the website to the browser