Network Topologies, Protocols and Layers

Network Topologies, Protocols and Layers

1. Network Protocols

   • Rules
     • 1) a protocol is a set of rules for how devices communicate and how data is transmitted across a network
     • 2) protocols cover how communication between two devices should start and end, how the data should be organised, and what the devices should do if data goes missing.
   • MAC Addresses
     • 1) every device needs a unique identifier so it can be found on a network
     • 2) MAC addresses are assigned to all network-enabled devices by the manufacturer.
     • 3) MAC addresses are 48 or 64 bit binary numbers (i.e. a long string of 48 or 64 Os and 1s). to make them easier to use they're converted into hexadecimals.
     • 4) MAC addresses are mainly used by the Ethernet protocol on LANs. LAN switches read the MAC addresses and use them to direct data to the right device.
   • IP Addresses
     • 1) IP addresses are used when sending data between TCP/IP networks e.g.over the internet
   • Packets
     • 1) data sent between networks (e.g. on the internet using TCP/IP) is split into equal-sized packets.
     • 2) every data packet has a header-this contains the control information. the control information is like the envelope of a letter-it includes the packet's destination address (where it's going), the source address (where it come's from) and the packet number.
     • 3) the data packet's payload is like the letter inside the envelope-it's the thing a person is likely to read, and the whole reason the data packets has been sent in the first place. the payload might be part of an email, document, web page or streamed video.
     • 4) packets are also likely to include a checksum number-a form of validation used to check that the payload data hasn't been corrupted during transit. the sending and receiving devices both calculate a checksum value by performing a function on the payload data. if the values match then the data has been received correctly.
     • Packet Switching
       • 1) the sending device splits the data into packets to be sent across the network. each packet is given a packet number to show the order of the data.
       • packet switching is used by routers to direct data packets on the internet and other IP networks.
       • 2) each router reads the packet header and decides which way to send the packet next, according to the IP rule.
       • 3) the way the data is sent changes depending on network traffic so the packets can take different routes. if a router receives too many packets at once it may prioritise some over others.