1. Networks

2. ProtocolMeaningApplication DNSDomain Name System (Server)Translates domain names such as ocr.org.uk into IP Addresses TLS/SSLTransport Layer Security / Secure Sockets Layer Cryptographic protocols designed for secure communications FTPFile transfer ProtocolFor copy files from one host to another HTTPHypertext Transfer ProtocolFor distributing hypermedia files – essentially web pages IMAPInternet Message Access Protocol One method for accessing emails. POP3Post Office Protocol (V3)Another method for accessing emails – used by webmail services TelnetAllows bi-directional text communications on a network

3. IP Addresses An Internet Protocol (IP) address is a unique reference number that is allocated to devices on a computer network that uses the Internet Protocol. It is used to identify the device that sends data over the network AND the device that is to receive the data. An IP address can be private, (for use on a LAN) or public (for use on the Internet or another WAN). The IP address allocated to a device on a network can be static (assigned by a system administrator) or dynamic, (assigned by another device on the network and different each time the connection is made).

4. IP Addresses Using IPv4, IP addresses are stored as 32-bit numbers, although for our convenience they are usually displayed as a series of 4 decimal numbers, each one representing 8 bits of the original binary address. –Binary version (32-bit): 11001001 0100000 010110100 11111111 –Decimal version: 201.64.182.255 The new IPv6 IP address system uses 128-bit numbers but for our convenience they are usually displayed as a series of 8 hexadecimal numbers, each one representing 16 bits of the original binary address. –Binary version (128-bit): 001000011101101000000000110100110000000000000000 001011110011101100000010101010100000000011111111 11111110001010001001110001011010 –Hexadecimal version: 21DA:00D3:0000:2F3B:02AA:00FF:FE28:9C5A

5. MAC Addresses In computer networking, a Media Access Control address (MAC address) is a unique 48-bit number assigned to a network interface card (NIC) to identify it on a LAN. Because they are so long, MAC addresses are usually displayed in hexadecimal, for example 00-0C-E7-5D-A8-AD. MAC addresses are limited to being used on a LAN but IP addresses can be used on multiple types of networks including the Internet.

6. Packets Modern computer networks, including the Internet, carry data by breaking it down into a series of distinct units called packets, rather than sending it as a continuous stream of data. A typical packet might contain 1,000 to 1,500 bytes and has two parts: Payload –This is the user data that is to be delivered and is located between the packet headers and footers. Header –This provides the data that the network needs to deliver the payload, for example the source and destination addresses. –It will also have error checking data such as checksums. –It will also contain the packet sequence number so the packet can be reassembled in the correct order.

7. Packets Source Address Destination Address Packet Sequence Number DataChecksum

8. The data is split into a number of smaller packets that may take different routes to reach the destination.