Lis chaque section en anglais. Le resume en francais ("En bref") est juste un filet de securite : essaie de comprendre en anglais d'abord.
📄 Voir cette section dans le PDF (page 549)
A network (as it relates to computers) is two or more devices that can communicate with each other. A network lets users share files, send email, browse the internet, share a printer/modem/scanner, and access shared applications and files.
Networks are divided into categories based on their size and type. A personal area network (PAN) connects personal devices (keyboard, mouse, TV, phone, laptop, desktop, mobile device, game console) in close proximity, wired or wireless - a Bluetooth keyboard connected to a PC is a PAN example.
A local area network (LAN) is a group of devices sharing resources in a single area (a room, home, or building). The most common LAN technology is Ethernet - a wired classroom of networked computers is a LAN example. A wireless LAN (WLAN) is a LAN that uses wireless devices (laptops, tablets, smartphones, smart home devices) that send data through the air instead of over cable.
A metropolitan area network (MAN) connects sites within the same city and can connect multiple LANs, wired (fiber) or wireless - for example, multiple college campuses in one city connected together. A wide area network (WAN) connects sites over a large geographic scale - two remote company locations connected together form a WAN.
A wireless WAN (WWAN) gives wireless connectivity over a large geographic area, using technologies like cellular or long-range fixed wireless. A wireless mesh network (WMN) is especially useful in emergencies because it passes data between peer radio devices and can cover large distances.
A storage area network (SAN) is a collection of storage devices used by multiple servers/network devices and managed centrally.
| Network type | Description |
|---|---|
| Personal area network (PAN) | Personal devices (keyboard, mouse, TV, cell phone, laptop, desktop, mobile device, game console) that communicate in close proximity, wired or wireless. Example: a Bluetooth keyboard connected to a PC. |
| Local area network (LAN) | A group of devices sharing resources in one area (room, home, building). Most common LAN technology is Ethernet. |
| Wireless LAN (WLAN) | Used in home/business networks; devices like laptops, tablets, smartphones, and smart home devices transmit data through the air. |
| Metropolitan area network (MAN) | Connectivity between sites within the same city and multiple LANs; can be wireless or use fiber cabling. |
| Wide area network (WAN) | Connectivity between sites on a large geographic scale, e.g., two remote company locations connected together. |
| Wireless WAN (WWAN) | Wireless connectivity for a larger geographic area, using technologies such as cellular or long-range fixed wireless. |
| Wireless mesh network (WMN) | Good for emergency situations; passes data between peer radio devices and can be used over large distances. |
| Storage area network (SAN) | A collection of storage devices used by multiple servers/network devices and centrally managed. |
Two or more devices that can communicate with each other.
A LAN uses wired connections (usually Ethernet); a WLAN is a LAN where devices connect wirelessly.
A WMN (wireless mesh network) - because it passes data between peer radio devices and can work over large distances without needing a single central link.
Centrally managed storage devices shared by multiple servers/network devices.
📄 Voir cette section dans le PDF (page 550)
Bluetooth is the most common PAN technology. Bluetooth devices include audio/visual products, automotive accessories, keyboards, mice, phones, game controllers, cameras, wireless headsets, and other small wireless devices. Bluetooth works in the 2.4 GHz range.
Traditional Bluetooth has three device classes (1, 2, 3) with ranges of less than 30 feet (10 m), 33 feet (10 m), and 328 feet (100 m) respectively, and a maximum transfer rate of 24 Mb/s. Bluetooth version 5 introduced Bluetooth Low Energy (BLE): longer range (vendors claim up to 800 feet/243 m, though not standard-defined) but slower speeds up to 2 Mb/s. BLE is good for Internet of Things (IoT) devices like sensors and household controls. BLE is NOT compatible with classic Bluetooth, though a device can support both.
Bluetooth supports both data and voice. Up to eight Bluetooth devices can connect in a piconet (a small Bluetooth PAN). Bluetooth has always had built-in security, including 128-bit encryption. Each computer/device must support a PAN to join a Bluetooth network.
LANs can be wired or wireless (a wireless LAN is a WLAN). A wired LAN is two or more devices connected via cable. Most LANs today are Ethernet LANs, using a central device called a hub or a switch. An Ethernet cable connects an RJ45 port on a network device to the hub or switch, which typically has 2 to 48 ports.
A hub is less intelligent than a switch: when a workstation sends data to a hub, the hub broadcasts that data out every port EXCEPT the one it came in on. A switch instead keeps a table of MAC addresses; when it receives data, it looks up the destination MAC address (burned into a NIC) and forwards the data only out the correct port. Hubs and switches can look similar, so check the model number to be sure which one you have.
Because a hub broadcasts to every port, collisions can occur when two devices send data at the same time - both devices must then wait and retry, wasting bandwidth. A switch eliminates collisions because it sends data only to the correct destination port, making it the better device to use.
Switches can be managed or unmanaged. A managed switch has its own IP address and can be configured, modified, and monitored across a corporate network. An unmanaged switch just connects devices to form a network with no configuration - typical for a home or small business.
Ethernet networks are physically wired in a star topology: each device has its own cable running to the hub/switch. If one device or cable fails, every other device keeps working; but if the hub/switch itself fails, the whole network goes down. Star topologies are easy to troubleshoot: if one device goes down, the problem is in that device, its cable, or its port; if a whole group of devices goes down together, the problem is most likely the hub/switch connecting them.
A switch looks up the destination MAC address and sends data only out the correct port, avoiding the broadcast-to-everyone behavior and collisions that a hub causes.
Only that one device loses connectivity if its cable fails; if the switch itself fails, the entire network goes down.
Bluetooth Low Energy, a longer-range but slower version of Bluetooth (introduced in Bluetooth 5); commonly used for IoT devices like sensors and household controls.
📄 Voir cette section dans le PDF (page 552)
In an Ethernet standard name like 100BaseT: the number (100) is the speed in Mb/s, the T means twisted pair cable is used, and Base means baseband technology - data is sent over a single channel on a single wire. This contrasts with broadband (used in cable TV), which carries multiple channels at different frequencies over one wire.
LANs typically use one of two models: a workgroup or a domain. A workgroup is used in a wired home or small business network. A domain is used in a corporate environment and usually contains multiple networks, with servers, databases, and shared resources that are centrally managed.
When connecting to a wired LAN with a Microsoft OS, you are typically offered a choice: workgroup, guest, public, private network, or domain. A private network (home or work) lets your computer be discovered by other devices there. A public network (a library, a hotel) is more restrictive - each user gets a network profile that helps Windows pick the right security/sharing settings for that connection.