Computer Science - Networking Notes

This is genuinely just human bio please kill me now.

DOD TCP/IP model - purposes

• Standardisation of Network Communication

• Reliable Data Transmission

• Routing and Adressing

• Support for a wide range of Services

• Scalability and Flexability

• Foundation for modern internet

DOP TCP/IP model - Standardisation of Network Communication

Provides a standardised set of protocols for transmitting data over networks. Ensures that different computer systems, regardless of their hardware and software configurations can communicate effectively.

DOP TCP/IP model - Reliable Data Transmission

Splits data into packets, transmitting them and then reassembling them at the destination, while also handling error checking and correction.

DOP TCP/IP model - Routing and Addressing

The IP component is responsible for addressing and routing packets to their destination across multiple networks. This is crucial for large-scale networks where the data must traverse various types of networks and devices.

DOP TCP/IP model - Support for a wide range of services

Many types of services and applications from file transfers and email to complex systems for command and control.

DOP TCP/IP model - Scalability and flexibility

Designed to scalable and adaptable to a range to network architectures, from small local networks to global communities.

DOP TCP/IP model - Foundation for the modern internet

Laid the groundwork for the modern Internet, using these protocols universally for all forms of digital communications.

Different types of layers in the DOD TCP/IP model

• Application

• Transport

• Internet

• Network

DOD TCP/IP model - Application Layer

Role and Functions

• Interfaces with user applications, enabling functionalities such as email, file transfers and web browsing.

Key protocols

• SMTP, FTP, HTTP, HTTPS, DCHP, DNS

Devices Required

• Servers and PC’s

DOD TCP/IP model - Transport Layer

Role and Functions

• Manages end-to-end communication, ensuring reliable data transfer for TCP (transition control protocol) and connectionless communication for UDP. Segments and manages data flow.

Key protocols

• TCP, UDP

DOD TCP/IP model - Internet Layer

Role and Functions:

• Handles logical addressing, routing, packet fragmentation and reassembly. Determines optimal packet routing paths.

Key Protocols:

• IPv4, IPv6, ARP, ICMP

Devices:

• Routers

DOD TCP/IP model - Network Layer

Role and Functions:

• Deals with physical and data link issues. Includes bit transmission, frame synchronisation, error handling and MAC addressing.

OSI Model - Physical Layer

Function:

• Handles the physical connection between devices, including bit synchronisation, transmission rate, physical topologies and transmission rates.

Protocols:

• Ethernet cables and fiber optics

Devices:

• Hubs, Repeaters, Modems, Cables, Network adapters

OSI Model - Data Link Layer

Functions:

• Defines the format of data on the network. Provides error detection and correction to ensure packets are free from errors.

Protocols:

• Ethernet (802.3), Wi-fi (802.11)PPP, Frame Relay

Devices:

• Bridges, Network Interface Cards (NICs), Switches, Wireless access points

OSI Model - Network Layer

Function:

• Determines how data is sent to the receiving devices and which route to take. Handles logical addressing, routing and traffic control.

Protocols:

• IP, ARP, RARP, ICMP

Devices:

• Routers, Layer 3 switches, Firewalls

OSI Model - Transport Layer

Functions:

• Manages end-to-end communication, ensuring reliable data transfer for TCP and connectionless communication for UDP. Segments and manages data flow.

Protocols:

• TCP, UDP

Devices:

• Firewalls and Load balancers

OSI Model - Session Layer

Functions:

• Manages sessions between applications. Handles setup, coordination (updating data between different systems/platforms) and termination of conversations between applications.

Protocols:

• netBIOS and RPC

Devices:

• Gateways/Firewalls

OSI Model - Presentation Layer

Function:

• Transforms data to provide a standard interface for the application layer. Handles encryption, compression and translation between data formats.

Protocols:

• SSL, TLS, MIME

Devices:

• Gateways

OSI Model - Application Layer

Function:

• Interacts with end-user software applications (Users interacting with intended software)

Protocols:

• HTTP, FTP, SMTP, Telnet

Devices:

• Gateways, Proxy Servers

Mnemonic for remembering OSI layers

1 → 7: Please Do Not Throw Sausage Pizza Away

Mnemonic for remembering DoD TCP/IP models

1 → 4: Missing In The Action

What is this?

A wired router

What is this?

A wireless router

What is this?

A switch

What is this?

A W.A.P (Wireless access point)

What is this?

A firewall

What is this?

The internet

What is this?

A server

What is a UTP (Unshielded Twisted Pair)?

TCP/IP Layer:

• Network Layer

Function:

• Used for connection network devices and transmitting data with less interference. It is a type of copper cable used in many ethernet networks. It consists of wires twisted together to reduce electromagnetic interference.

Technical Details:

• Categories: Cat 5e, Cat 6, Cat 6a, Cat 7 (each supporting increasing data rates and bandwidth). Typical use in LAN environment

What is a Fiber Optics?

TCP/IP Layer:

• Network Layer

Function:

• Transmits data as light pulses, ideal for long distances and high data rates. It is immune to electromagnetic interference.

Technical Details:

• Types: Single-mode (long distances and high bandwidth) and multimode (short distances and less bandwidth).

• Standards: OS1, OS2 (single mode); OM1, OM2, OM3, OM4, OM5 (multiple modes)

What is the meaning of Wireless as a network component?

TCP/IP Layer:

• Network Layer

Function:

• Uses electromagnetic waves to transmit data, allowing for mobile connections and infrastructure flexibility. It includes radio signals/infrared signals to transmit data across air and no physical wires.

Technical Details:

• Frequencies: 2.4 GHz (wider coverage, slower speed), 5 GHz (faster speed, shorter range).

• Standards: IEEE 802.11a/b/g/n/ac/ax

What is a Router?

TCP/IP Layer:

• Internet Layer

Function:

• Directs data packets between networks based on IP addresses, managic traffic within interconnected networks. It examines the destination IP address of a pocket and determines the best route for it and forwards it accordingly.

Technical Details:

• Routing Protocols: OSPF, BGP, EIGRP. Capable of layer 3 switching, QOS, IPv4 and IPv6 support.

What is a Switch?

TCP/IP Layer:

• Network Layer

Function:

• Connects devices on the same network segment, using MAC addresses to send data packets directly to devices, reducing unnecessary traffic. It is used to connect devices within the same network segment. A switch can identify which device the data needs to be sent to using MAC addresses.

Technical Details:

• Types: Managed (configurable options), unmanaged (plug and play), PoE (Power over Ethernet).

• Standards: IEEE 802.3 (Ethernet), IEEE 802.1D (STP), IEEE 802.1Q (VLAN)

What is a Wireless Access Point (WAP)?

TCP/IP Layer:

• Network Layer

Function:

• Connects wireless clients to a wired network, extending user mobility and network availability. It bridges the gap between a wired network and wireless clients.

Technical Details:

• Modes: Bridge, Repeater, Client mode. Supports security standards like WEP, WPA, WPA2.

What is a Firewall?

TCP/IP Layer:

• Internet Layer

Function:

• Monitors and controls incoming and outgoing network traffic based on security rules, blocking unauthorised access. It can operate at multiple layers and essentially provides a barrier between a secure internal network and the internet.

Technical Details:

• Types: Hardware (stand-alone unit), software (program on computer), UTM (Unified Threat Management).

• Features: Packet filtering, stateful inspection, proxy services and VPN supports.

What is a Gateway?

TCP/IP Layer:

• Internet Layer

Function:

• Provides a point of access between different networks, often using different protocols and allows networked devices to communicate. Gateways are crucial for protocol conversation, data format transformation and routing between different network architectures like between a corporate network and the internet.

Technical Details:

• N/A

Packet Architecture - Data

Refers to the application-level content that needs to be transmitted across a network, such as files, emails or web pages and is process at the Application Layer of the OSI model and is the actual user-generated content.

Packet Architecture - Segments

Units used at the Transport Layer and includes essential control information and manages the data into manageable chunks that facilitate efficient and secure data transmission.

Packet Architecture - Packets

Operate at the Network Layer and are essential for delivering segments across different networks and subnetworks and routing decisions are made based on the information in the packet headers.

Packet Architecture - Frames

Used at Data Link and ensures packets are delivered over a single link node to another.

Packet Architecture - Bits

Smallest units of data represented by binary digits (0 or 1). Grouped together to form all higher-level structures.

Role of IP Addresses

• Identification

• Location Addressing

Role of Subnet Masks

• Network Partitioning (Separates the network or street for example, to the host or house)

• Traffic Routing to help routers to determine whether the destination IP is in a local network or outside of it.

MAC Address and Layer 2 Switching

• Unique identifier which does not change no matter which network you are connected to

• Switches operate at Layer 2 and use MAC addresses to redirect packets within LAN segments.

IP Address and Layer 3 Routing

• Every device has an IP address to identify the device on the network

• Routers operate at this layer and use IP addresses to determine the best path for forwarding these packets.

TCP vs UDP

• TCP (Transmission Control Protocol): Provides reliable, ordered, and error-checked delivery of a stream of packets on the network. Uses acknowledgments and retransmissions to ensure complete data transfer.

• UDP: Faster, simpler, and does not guarantee message delivery. Best used for video streaming, gaming, and live broadcasts where speed is crucial, and loss is tolerable.

Reliability between TCP and UDP

TCP:

• Reliable (guarantees delivery)

UDP:

• Unreliable (does not guarantee delivery)

Speed between TCP and UDP

TCP:

• Slower due to setup and management.

UDP:

• Faster due to minimal overhead

Use Cases between TCP and UDP

TCP:

• Web browsing, email and file transfers

UDP:

• Streaming, online gaming and VoIP

Use Cases between TCP and UDP

TCP:

• Data → Segment → Packet → Frame → Bits

UDP:

• Data → Datagram → Packet → Frame → Bits

IPv4 vs IPv6 - Address Length

IPv4:

• 32-bit

IPv6:

• 128-bit

IPv4 vs IPv6 - Address Format

IPv4:

• Displayed as a dotted decimal (e.g., 192.168.1.1). Each number can be from 0 to 255.

IPv6:

• Displayed in Hexadecimal

IPv4 vs IPv6 - Security

IPv4:

• Initially did not integrate encryption and authentication

IPv6:

• Has IPsec security built into the protocol, ensuring a higher level of security.

IPv4 vs IPv6 - Configuration

IPv4:

• Requires manual or DHCP

IPv6:

• Stateless address autoconfiguration (SLAAC) or DHCPv6

Public vs Private IP addresses - Definition and IP range

Private IP Addresses:

• IP addresses used within a single private network. Not routable on the global internet.

• 10.0.0.0 to 10.255.255.255 (10/8 prefix) OR 172.16.0.0 to 172.31.255.255 (172.16/12 prefix) OR 192.168.0.0 to 192.168.255.255 (192.168/16 prefix)

Public IP Addresses:

• Unique IP addresses used across the entire internet. Routable globally.

• No specific ranges; each IP is unique on the internet.

Subnetting

Divides a network into smaller networks (subnets) and for values:

• Class A: 0.0.0.0 to 127.255.255.255 - the subnet is 255.0.0.0

• Class B: 128.0.0.0 to 191.255.255.255 - the subnet is 255.255.0.0

• Class C: 192.0.0.0 to 223.255.255.255 - the subnet is 255.255.255.0

CIDR Notation

1. Determine the size of the network

2. Based on the size you need to calculate how many bits are needed. For example if you have 4 subnets, you need at least 2 bits (2² = 4 subnets). To have 254 hosts, you need 8 bits (2^8 - 2 = 254 subnets)

3. Divide the network

Remember, 2 addresses are unusable as one is the network address and the other is the broadcast address.

Network Performance

1. Bandwidth: The maximum rate at which data can be transmitted over a network connection. Higher bandwidth allows more data to be transmitted in a given time, leading to faster transmission speeds.

2. Network Design: Encompasses the overall architecture of a network, including the hardware used and the protocols in place. Efficient network design can optimise data flow.

3. Data Collisions: Occur when two or more devices attempt to send a packet across a network segment at the same time but using a Collision Detection system helps.

4. Excess Broadcast Traffic: Refers to the network traffic that is sent to all the nodes on the network and excessive broadcast traffic can consume a lot of bandwidth leading to network slowdowns.

Network Performance Management and Troubleshooting - Ping

Function:

• Sends ICMP echo requests to a target host to measure the availability and round trip time of messages

Use:

• Primarily used to check if a device is reachable across a network and to measure how long it takes data to travel to and from the device

Network Performance Management and Troubleshooting - Traceroute

Function:

• Traces the path data packets take from the source to the destination. It provides the sequence of hops that the packet travels, identifying where delays or drops occur.

Use:

• Useful for pinpointing where data paths are inefficient or where data is getting lost.