What Is the Network?

A network is a group of two or more connected computing devices. Usually, all devices in the network are connected to a central hub — for instance, a router. A network can also include subnetworks or smaller subdivisions of the network. Subnetworking is how very large networks, such as those provided by ISPs, are able to manage thousands of IP addresses and connected devices.

What Happens at the Network Layer?

Anything that has to do with inter-network connections takes place at the network layer. This includes setting up the routes for data packets to take, checking to see if a server in another network is up and running, and addressing and receiving IP packets from other networks. This last process is perhaps the most important, as the vast majority of Internet traffic is sent over IP.

What Is a Packet?

All data sent over the Internet is broken down into smaller chunks called "packets." When Bob sends Alice a message, for instance, his message is broken down into smaller pieces and then reassembled on Alice's computer. A packet has two parts: the header, which contains information about the packet itself, and the body, which is the actual data being sent.

At the network layer, networking software attaches a header to each packet when the packet is sent out over the Internet, and on the other end, networking software can use the header to understand how to handle the packet.

A header contains information about the content, source, and destination of each packet (somewhat like stamping an envelope with a destination and return address). For example, an IP header contains the destination IP address of each packet, the total size of the packet, an indication of whether or not the packet has been fragmented (broken up into still smaller pieces) in transit, and a count of how many networks the packet has traveled through.

What Is the (OSI) Model?

(OSI) model is a conceptual framework that divides network communications functions into seven layers

OSI Model

• Application

  • Data generated by and usable by software applications. The main protocol used at this layer is HTTP.

• presentation

  • Data is translated into a form the application can accept. Some authorities consider HTTPS encryption and decryption to take place at this layer.

• session

  • Controls connections between computers (this can also be handled at layer 4 by the TCP protocol).

• Transport

  • Provides the means for transmitting data between the two connected parties, as well as controlling the quality of service. The main protocols used here are TCP and UDP.

• Network

  • Handles the routing and sending of data between different networks. The most important protocols at this layer are IP and ICMP.

• DataLink

  • Handles communications between devices on the same network. If layer 3 is like the address on a piece of mail, then layer 2 is like indicating the office number or apartment number at that address. Ethernet is the protocol most used here.

• Physical
  • Packets are converted into electrical, radio, or optical pulses and transmitted as bits (the smallest possible units of information) over wires, radio waves, or cables.

Layers

• Layer 1 Devices

  • Analog Modem

  • HUB

• Layer 2 Devices

  • Switch

  • Wireless Access Point (Wap)

• Layer 3 Devices
  • Multi-layer switch
  • Router

Security Devices

• Firewall
• intrusion detection system (IDS)
• intrusion presentation system (IPS)
• virtual private network (VPN)

Optimization And Performance Devices

In short, Network Optimization refers to the tools, techniques, and best practices used to monitor and improve network performance. It involves analyzing the network infrastructure, identifying bottlenecks and other performance issues, and implementing solutions to eliminate or mitigate them.

• Load balancer
• Proxy server

Networking Services And Application

Network services are applications at the network application layer that connect users working in offices, branches, or remote locations to applications and data in a network. These services typically run on servers.

• VPN Types
  • site-to-site
  • host-to-site (remote access)
  • host-to-host (SSL)

Protocol Used By Vpn

• Internet Protocol Security (IPsec)
• Generic Routing Encapsulation (GRE)
• Point-to-Point Tunneling Protocol (PPTP)
• Transport Layer Security (TLS) Protocol
• Secure Socket Layer (SSL) Protocol

What Protocols Are Used at the Network Layer?

A protocol is an agreed-upon way of formatting data so that two or more devices are able to communicate with and understand each other. A number of different protocols make connections, testing, routing, and encryption possible at the network layer, including:

• IP (Internet Protocol)
• IPsec (Internet Protocol Security)
• ICMP (Internet Control Message Protocol)
• IGMP (Internet Group Management Protocol)
• GRE (Generic Routing Encapsulation)

Resources: https://www.cloudflare.com/learning/network-layer/what-is-the-network-layer/

Thanks for reading.

Regards, Elliot :)