Wired and Wireless Networks

Wired and Wireless Networks

1. Protocols

   • There are lots of different types of protocols like HTTP Protocols, wich is used for accessing the internet And receiving web pages, and HTTPS, is a secure protocol that encrypts the information in case it is hacked.
   • FTP is File Transfer Protocol and is used for sending or retrieving files from a remote server.
   • An Email works by sending the simple mail transfer protocol to the mail server which forwards it through the internet to another mail server and then the client either downloads it fully or leaves it on the server till its needed.
   • The TCP/IP protocol stack is divided into four layers: The application layer,transport layer, network layer and link layer. They are passed up the layers.
     • The network applications you are using operate on the newtork application layer.
     • The transport layer creates connections between two hosts. The two computers agree size of packets.
     • Routers operate on the netwrok layer and on the packets are destination addresses ready for transmission
     • The data link layer is things like cables, physical hardware that connects the two hosts.

2. The Internet

   • A collection of interconnected networks
   • Wide area networks (WAN) for big businesses or somewhere spread over a large geographical area
   • Local area networks are used for small businesses or schools
   • Every network has a unique address and there is so many that the IPv4 addresses are running out
   • The connection between you and another in a phone call is called circuit switching
   • If you are sending a file or anything the file is broken up into packets. Any lost files that are not recieved are resent.
   • DNS converts web address in to an IP address
   • A Media Access Control (MAC) address is assigned to each Network Interface Card (NIC). Your computer may have more than one.
   • When you request a web page, each router along the way uses the MAC address of the next router to send the data packet on the next leg of its journey
   • LANs can have different topologies like star and mesh

3. Wireless Networking

   • Every device able to connect to the internet has a network interface card (NIC)
   • A wireless Access Point is a device that allows wireless devices to connect to a wired network using Wi-Fi
   • Data that is transmitted over a network can be intercepted. So data gets encrypted. Encryption is the encoding of data so that it can no longer be easily understood
   • Ciphertext the encrypted message. Encryption the process of converting plaintext into ciphertext. Key a sequence of numbers used to encrypt or decrypt, often data using a mathematical formula. Encryption algorithm the formula for encrypting the plaintext.

4. Client Servers/ P2P Networks

   • Peer to Peer Networks
     • Suitable for a small companies with fewer computers. No central server controls files or security. All computers can easily see files on all other computers. All computers can communicate with each other without going through a server. If a computer is switched off, data cannot be retrieved .
   • Client Servers
     • The server is a powerful computer which provides services or resources required by any of the clients. A client is a computer which requests the services or resources provided by the server
     • A file server holds all the data files and databases and manages backups. A print server may organise printing on different printers. An email server may receive emails, detect and block spam, distribute emails to users. A web server may host an external website.
     • The client sends requests to the server, waits for a reply and receives the reply. The server waits for requests from a client, acknowledges the request. The server may need to pass the request to another server – in which case, it becomes the “client”. The requested data is sent back to the client