Computer networks :
A computer network is a group of computers that use a set of common communication protocols over digital interconnections for the purpose of sharing resources located on or provided by the network nodes.
- The interconnections between nodes are formed from a broad spectrum of telecommunication network technologies, based on physically wired, optical, and wireless radio-frequency methods that may be arranged in a variety of network topologies.
- The nodes of a computer network may be classified by many means as personal computers, servers, networking hardware, or general purpose hosts.
- They are identified by hostnames and network addresses.
- Computer networks may be classified by many criteria, for example, the transmission medium used to carry signals.
Uses:
A computer network extends interpersonal communications by electronic means with various technologies, such as email, instant messaging, online chat, voice and video telephone calls, and video conferencing.
Comman layouts are:
Bus network : . This was the layout used in the original Ethernet, called 10BASE5 and 10BASE2. This is still a common topology on the data link layer, although modern physical layer variants use point-to-point links instead.
Star network : all nodes are connected to a special central node. This is the typical layout found in a Wireless LAN, where each wireless client connects to the central Wireless access point.
Ring network : each node is connected to its left and right neighbour node, such that all nodes are connected and that each node can reach each other node by traversing nodes left- or rightwards.
Mesh network : each node is connected to an arbitrary number of neighbours in such a way that there is at least one traversal from any node to any other.
Fully connected network :each node is connected to every other node in the network.
Tree network : nodes are arranged hierarchically.
There are 11 types of networks
1. Personal area network (PAN):The smallest and most basic type of network, a PAN is made up of a wireless modem, a computer or two, phones, printers, tablets, etc., and revolves around one person in one building and are managed by one person or organization from a single device.
2. Local area network (LAN):LANs are the most frequently discussed networks, one of the most common, one of the most original and one of the simplest types of networks. LANs connect groups of computers and low-voltage devices together across short distances.
3. Wireless local area network (WLAN):Functioning like a LAN, WLANs make use of wireless network technology, such as Wi-Fi. Typically seen in the same types of applications as LANs, these types of networks don’t require that devices rely on physical cables to connect to the network.
4. Campus area network (CAN):Larger than LANs, but smaller than metropolitan area networks (MANs, explained below), these types of networks are typically seen in universities, large K-12 school districts or small
5.Metropolitan area network (MAN):These types of networks are larger than LANs but smaller than WANs – and incorporate elements from both types of networks. MANs span an entire geographic area (typically a town or city, but sometimes a campus).
6 Wide area network (WAN):Slightly more complex than a LAN, a WAN connects computers together across longer physical distances. This allows computers and low-voltage devices to be remotely connected to each other over one large network to communicate even when they’re miles apart.
7. Storage area network (SAN):As a dedicated high-speed network that connects shared pools of storage devices to several servers, these types of networks don’t rely on a LAN or WAN.
8. System area network (also known as SAN):It is used to explain a relatively local network that is designed to provide high-speed connection in server-to-server applications (cluster environments), storage area networks (called “SANs” as well) and processor-to-processor applications. The computers connected on a SAN operate as a single system at very high speeds.
9. Passive optical local area network (POLAN):As an alternative to traditional switch-based Ethernet LANs, POLAN technology can be integrated into structured cabling to overcome concerns about supporting traditional Ethernet protocols and network applications such as PoE (Power over Ethernet).
10. Enterprise private network (EPN):These types of networks are built and owned by businesses that want to securely connect its various locations to share computer resources.
11.Virtual private network (VPN) :a VPN lets its users send and receive data as if their devices were connected to the private network – even if they’re not.
Purpose :
Networking computers together allows users to distribute copies of important information across multiple locations, ensuring essential information isn't lost with the failure of any one computer in the network
Ip address :
- An IP address is a 32-bits number that uniquely identifies a host (computer or other device, such as a printer or router) on a TCP/IP network.
- IP addresses are normally expressed in dotted-decimal format, with four numbers separated by periods, such as 192.168..
