CS Networking Basics
Protocols and Networking
A thorough understanding of computer communication is crucial for professionals working in the field of cyber security. When utilizing programs, there is significantly less visible activity taking place on computer networks than what is seen behind the scenes.
The OSI Model
The “Open Systems Interconnection” (OSI) paradigm is a simple and natural approach to standardize the various components needed for network communication.
The model divides the requirements into several layers, making it evident what is needed to communicate on a network.
The OSI Model appears like this:
| Layer | What it does |
|---|---|
| 7 – Application | Where humans process data and information |
| 6 – Presentation | Ensures data is in a usable format |
| 5 – Session | Capable of maintaining connections |
| 4 – Transport | Data is forwarded to a service capable of handling requests |
| 3 – Network Layer | Responsible for which path packets should travel on a network |
| 2 – Data Link | Responsible for which physical devices packets should go to |
| 1 – Physical | The physical infrastructure to transport data |
Usually, the operating system’s software implements the first three layers:
| Layer | Where it is implemented |
|---|---|
| 7 – Application | Software |
| 6 – Presentation | Software |
| 5 – Session | Software |
Typically, the bottom three layers are implemented in hardware within network devices, such as firewalls, switches, and routers:
| Layer | Where it is implemented |
|---|---|
| 3 – Network Layer | Hardware |
| 2 – Data Link | Hardware |
| 1 – Physical | Hardware |
The software and hardware layers are connected by Layer 4, often known as the Transport layer.
A technology known as “Software Defined Networking” (SDN) makes it possible to incorporate additional hardware layers through software.
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Layer 7 - Application Layer
This is where the application’s functionality and business logic are found. Users communicate with services via a network using this. The Application Layer is where most developers create applications.
The majority of the programs you utilize operate on the Application Layer, concealing the intricacy of higher layers.
Examples of Layer 7 Applications:
- HTTP (“Hypertext Transfer Protocol”) – permits us to use online applications
- FTP (“File Transfer Protocol”) – enables file transfers between users
- SNMP (“Simple Network Management Protocol”) -Read and change network device configuration protocols
Numerous programs, including Microsoft Skype, FileZilla, and Google Chrome, make use of these protocols.
This class is accessible to you through Layer 7!
Layer 6 - Presentation Layer
usually an invisible layer that is in charge of translating, altering, and adjusting data. This is to guarantee that the layers below the application can communicate with one other.
- Text and data are represented via encoding schemes, such as UTF (Unicode Transformation Format) and ASCII (American Standard Code for Information Interchange).
- Services encryption, such as TLS (“Transport Security Layer”) and SSL (“Secure Sockets Layer”)
compression, such as GZip, which is used in numerous HTTP implementations.
Layer 5 - Session Layer
Managing connections between the application and the tiers below is the duty of this layer. It entails starting, stopping, and maintaining connections, also called sessions.
Typical protocols that effectively depict the Session Layer include:
- SOCKS – a protocol that uses a proxy server to transfer packets.
- NetBIOS -An outdated Windows protocol used for name resolution and session establishment.
- SIP (“Session Initiation Protocol”) -In order to participate in Voice Over IP (VOIP) conversations
Layer 4 - Transport
the layer that permits network representation of applications.
Some well known applications on this layer:
- TCP (“Transmission Control Protocol”) -Used for numerous applications, it guarantees dependability, stability, control over the amount of data that can be transferred at any one time, and more.
- UDP (“User Datagram Protocol”) -lightweight and speedy protocol usage for numerous applications.
- QUIC (“Quick UDP Internet Connections”) – a protocol that works in tandem with HTTP version 2 and is intended for quicker connectivity.
Layer 3 - Network
a layer that uses routers to route data between networks.
The following protocols are present on this layer:
- IP (“Internet Protocol”) – used frequently for Internet connectivity. is available in IP versions 4 and 6.
- ICMP (“Internet Control Message Protocol”) – Used for a variety of purposes by network operators and devices, such as diagnosing network connections or enabling devices to transmit and react to fault conditions.
- IPSec (“Internet Protocol Security”) -permits two network devices to connect securely and encrypted.
Layer 2 - Link
As the name suggests, link networks are made up of protocols intended to transfer data via the real links—that is, the physical connections—that network nodes are a part of. To put it another way, the Link Layer is in charge of transferring data from the physical to the logical (or network) layers.
On this tier, among the protocols are:
- Ethernet – a fundamental protocol that most operating systems employ when physically connecting via a cable to networks.
- Wi-Fi (“Wireless Fidelity”) – for using radio signals to access networks. IEEE 802.11.xx is the family of protocols that it employs.
- NDP (“Neighbor Discovery Protocol”) -This protocol is used on the Link Layer by IP version 6 (IPv6) to collect data needed for IPv6 communication.
Layer 1 - Physical
The signaling that enables the transport of bits and bytes via a physical channel is represented by the physical layer. It can be sent by radio, signals sent across a cable, electrical signals, light, or fiber, among other means.
The following are some instances of Physical Layer protocols:
- CAN Bus (“Controller Area Network”) – used by microcontrollers and other devices—without the use of a computer—to connect with other devices of a similar kind. utilized frequently in Industrial Control Systems, or ICS.
- Ethernet Physical Layer -utilized by Ethernet at the physical layer to transmit signals at up to several gigabits per second.
- Bluetooth Physical Layer – Bluetooth has its own set of guidelines regarding the transmission and reception of radio signals.
