Chapter 2 - Networking Background - TCP/IP

What is Networking?

connecting computers to share resources and communicate

What is TCP/IP?

Transmission Control Protocol/Internet Protocol.

• fundamental set of communication protocols used for the internet and most modern networks.

• TCP ensures reliable data transmission

• IP handles addressing and routing

What is the purpose of using a layered (stacked) model in networking?

To control complexity by separating responsibilities across layers, making systems easier to build and maintain.

How many layers does the TCP/IP model have typically?

1. application

2. Transport (TCP)

3. Network (IP)

4. Link

What is the OSI model and why is it not widely used?

A 7-layer networking model developed for flexibility and problem-solving; it's not widely used because no full implementation was adopted.

What does the Application layer in TCP/IP handle?

User interaction.

User-level protocols like HTTP, SSH, SFTP, etc.,

What does the Transport layer in TCP/IP handle?

Reliable communication.

Manages how data is sent and received between devices.

Responsible for error checking, requesting retransmissions and packet ordering.

What does the Network layer in TCP/IP do?

addressing and routing

What is the responsibility of the Link layer in TCP/IP do?

physical transmission

What is network addressing?

used to identify devices on a network so they can send and receive data.

What are the three levels of addressing in TCP/IP?

1. Physical (MAC) addresses (Link layer)

2. IP addresses (network layer)

3. Port addresses (transport layer)

What is a physical (MAC) address?

• 48-bit

• hardware address

• embedded in a network interface card (NIC),

• used at the Link layer for identifying devices before its assigned an IP address

• letters and numbers

device provides network with its MAC address

What is an IP address?

• A numerical address

• used to identify a network interface in the Internet layer, often mapped to a hostname using DNS.

• helps devices talk to each other across networks

• ‘phone number’

• 4 numbers separated by :

the IP address can change depending on what network you’re connected to. if you go to a new Wi-Fi network, you’ll get a new IP address

network provides device with its IP address

Why can a single device have multiple IP addresses?

Because it can have multiple active network interfaces (e.g., WiFi, Ethernet, Bluetooth), each needing its own IP.

What is a port number?

• 16-bit number

• identifies a specific application or service running on a host,

• allows communication to be directed correctly.

• ‘person you want to call’

the device provides the application with the port address

What is a socket in networking?

A combination of an IP address and a port number that identifies a specific endpoint for communication.

What are well-known ports and what range do they cover?

Ports 0–1023,

reserved for standard services like HTTP (80), HTTPS (443)

What is port 7 used for?

Echo – allows a device to send messages to itself, mainly for testing.

What is port 80 used for?

HTTP (Hypertext Transfer Protocol) – used for standard web traffic.

What port does HTTPS use?

Port 443.

What are registered and dynamic ports?

• Registered ports: 1024–49151, commonly used by non-standard but popular services.

• Dynamic/unreserved ports: 49152–65535, used freely for temporary or custom connections.

What is DHCP?

Dynamic Host Configuration Protocol – assigns IP addresses to devices automatically when they join a network.

What is DNS?

Domain Name System – translates human-readable hostnames into IP addresses using a distributed hierarchy of name servers.

What is an authoritative DNS server?

A server that provides official IP address mappings for a domain, e.g., Swansea University's DNS servers for “.swan.ac.uk”.

What is a DNS cache?

A temporary store of recently looked-up hostnames and IP addresses to improve speed, though it may become outdated.

What is a root DNS server?

One of 13 global servers at the top of the DNS hierarchy, used as a last resort when lower-level DNS servers can't resolve a hostname.

What two things do you usually need to connect to a service?

• IP address or hostname (to locate the host)

• port number (to locate the service).