Networking Basics

• A network is a collection of connected devices providing a service to users.
• Examples of devices in a network include computers and printers.

Network Benefits

• Networks facilitate data sharing.
• Networks enable resource sharing, such as printers.
• Modern technology, like video conferencing, is a benefit of networks.

Network Components

• End devices like PCs and printers are network components.
• Network devices, also known as intermediate devices such as hubs, switches and routers are also networks components.
• Lastly, media components using wires or wireless are also networks components.

Network Devices

• Network Interface Card (NIC)
• Hub
• Switch
• Router

Hubs

• A hub is a network device that repeats received information from one host to all connected hosts, enabling communication between them.
• Hubs relay information to all connected hosts
• All hosts connected can communicate with each other

Types of Communication

• Unicast is communication from one host to another.
• Broadcast is communication from one host to all hosts on the network.
• Multicast is communication from one host to a select few hosts.

Hub Problems

• A hub repeats information from one host to all others.
• A hub has a single collision domain.

Switches

• Switches replace hubs to prevent any network degradation.
• Switches connect hosts in a network and break up the collision domain by giving each port its own collision domain.
• If Host A sends a packet to Host C, Host B will not receive it because each host is in its own collision domain.

Switch Issues

• Hubs flood all packets, including unicast ones.
• Switches don't flood unicast packets, however they do flood broadcast packets.
• Hosts in a switched network are within the same broadcast domain.
• All connected hosts will receive any broadcast sent within that domain.
• While broadcasts have useful and essential network operations, having too many can slow down the network.

Routers

• Routers prevent the transmission of broadcasts across different networks that it interconnects, therefore breaking up the broadcast domain.
• Broadcasts from hosts connected to Switch1 will not reach hosts connected to Switch2 or Switch3 because the router will drop the broadcast on its receiving interface.

Router Functions

• Routers break up broadcasts.
• Routers switch packets among networks
• Routers select the best path for the destination network.
• Routers can drop or forward packets based on certain criteria such as their source and destination.

Collision domain & broadcast domain

• Hubs have one collision domain and one broadcast domain.
• Switches have n collision domains and one broadcast domain.
• Routers have n collision domains and n broadcast domains.
• n = number of ports or interfaces.

Networking Types

• Local Area Network (LAN): Is a network covering a limited geographical area, such as a floor, building, or campus.
• LANs usually have a high data transfer rate.
• The Ethernet standard is the most commonly used technology in LANs
• Wide Area Network (WAN): Describes a network covering a large geographical area, such as multiple cities, a country, or across the world.
• WANs connect LANs across a wide area.
• A typical example is the connection of LANs in various company offices.