Computer Networks 3
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IP addressing and MAC addressing uniquely identify devices on a network. IP addresses can be public for internet use or private for local networks, while MAC addresses uniquely identify devices locally. Network packets break data into smaller units with headers containing control information like source and destination addresses for routing. Common network protocols like TCP and IP define rules for formatting and exchanging data between devices.
Computer Networks 3
- 1. © GCSE Computing Candidates should be able to: explain the terms: IP addressing MAC addressing Network packets Network protocols Slide 1 GCSE Computing - 1.6 Computer communications and networking (3)
- 2. © GCSE Computing 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). Slide 2 What is IP addressing?
- 3. © GCSE Computing 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 Slide 3 What do IP address look like?
- 4. © GCSE Computing 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. On a LAN, data packets that use a protocol such as TCP/IP will be packaged inside data packets that use the MAC address to deliver them correctly. Another use for the MAC address is as a security feature on cabled and wireless systems, only allowing computers with authorised MAC addresses to have access to the network. This works by inspecting the data packet that is sent from a computer to see if its MAC address matches one of the approved ones in a a pre- defined table. Slide 4 What is MAC addressing?
- 5. © GCSE Computing 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. Control information 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 and the number of the packet so they can be reassembled in the correct order. The control information is found in the packet headers Slide 5 What is a Data Packet?
- 6. © GCSE Computing In complex networks such as the Internet, a series of packets sent from one computer to another may follow different routes to reach the same destination. This technology is called packet switching and makes the network more efficient because the network can balance the load across various pieces of equipment and if there is a problem with one piece of equipment in the network then packets can be routed around it. Data packets can be nested inside each other, for example on a LAN, IP packets are held inside Ethernet packets (that use the MAC address) to route the packet to the correct destination computer. If a packet is destined for the Internet then the Ethernet packet is discarded when it leaves the LAN. When the IP packet returns to the LAN from the Internet then it is placed inside another Ethernet packet for final delivery to the computer with the MAC address that requested the information. Slide 6 What is a Data Packet?
- 7. © GCSE Computing A protocol is a formal description of the format that data has to be in and the rules for exchanging this data. There may also be rules for error checking and error correction. As long as different computers on a network are using the same protocol then they will be able to exchange data correctly. The Internet Protocol Suite is the set of communications protocols used for the Internet and other similar networks. It is commonly also known as TCP/IP, named from two of the most important protocols in it: the Transmission Control Protocol (TCP) the Internet Protocol (IP). The TCP provides the service of exchanging data directly between two networked computers while the IP is used to route data packets between networks and over the Internet. Some other common Internet Protocols: HTTP (HyperText transfer Protocol): used on the World Wide Web for transferring web pages and files contained in web pages such as images. FTP (File Transfer protocol): employed for transferring files between computers. SMTP (Simple Mail Transport Protocol): used for email. Slide 7 What is a Protocol?