1 6 Further System Fundamentals (HL) 6.4 Further Network Fundamentals

6.4.3 Network Protocols

3 How to transmit Data can be transmitted according to a fixed time sequence, like a clock (synchronous), or special bytes can be used to mark the end of a burst (asynchronous transmission).

4 Serial vs. parallel These methods use serial transmission (one bit is sent down the cable at a time). Parallel transmission is faster as many bits can be sent down a multi-cored cable at the same time (only possible over short distances though as the bits in a parallel byte can get out of step).

5 Serial vs. parallel Serial is generally preferred as it is easier to implement, allows full-duplex (parallel can only be half-duplex) and permits longer cables. USB = universal serial bus.

6 Protocols All communications are covered by agreed sets of rules or protocols. They define things such as transmission speed (baud rate), parity checking methods, asynchronous or synchronous transmission, etc.

7 An example Modern ethernet networks use TCP/IP as their protocol, as does the internet. TCP controls how applications communicate and the disassembly/reassembly of packets. IP is the packet switching protocol that directs packets over the network.

8 IP addresses As part of IP, each node is given its own address (4 x 8-bit numbers) e.g This is hierarchical (the first number gives general region, etc.). URLs must be translated into IP addresses by DNS servers (they translate intst.eu into ).