Protocols & Layers
The rules that govern data transfer and addressing on a network.
Standards & Protocols
Standard
An agreed set of rules for areas of computing. Standards allow hardware and software from different manufacturers to interact and be compatible (interoperability).
Protocol
A specific set of rules governing the transfer of data between devices over a network.
The foundational protocol model for all data packets transmitted over the Internet.
Hypertext Transfer Protocol. Used for requesting and delivering non-secure web pages.
Secure HTTP. Requesting and delivering secure, encrypted web pages (standard today).
File Transfer Protocol. Specifically designed for transferring files between a client and a server.
Simple Mail Transfer Protocol. For sending or forwarding emails from a client to a mail server.
For retrieving emails. POP downloads & deletes from server; IMAP syncs across devices.
Examiner's Eye
Vast numbers of students confuse the mail protocols! Remember the trick "Send Mail To People" for SMTP (sending). Also, remember that POP practically pops the email into the trash on the server once downloaded to one device, making it useless for people who read mail on both a phone and a laptop. Use IMAP for syncing across devices.
Check Your Understanding
1. A user wants to upload a large 2GB backup file of their coursework to a secure remote server. Which protocol should be used for this file transfer?
2. A business professional reads emails on their workplace desktop, their personal laptop, and their smartphone. Which protocol should their email client use to retrieve messages?
3. Why are network protocols divided into distinct "layers"?
The Concept of Layers
A layer is a simple division of network functionality. The TCP/IP model divides network communication into abstraction layers.
Why use layers? (The Benefits)
Network Addressing
MAC Address
e.g. 00:1A:2B:3C:4D:5E
48-bit addresses hardcoded into a device's NIC during manufacturing. They are fixed and used to direct data within a Local Area Network (LAN).
IP Address
IPv4 (e.g. 192.168.1.1) | IPv6 (e.g. 2001:0db8::8a2e:0370)
Allocated to a device by the network software. Used for routing data across the internet. IPv6 was created (using hex) because IPv4 completely ran out of available numerical addresses.
The IPv4 Limit Trap
Look out for questions asking you to identify an "invalid" IPv4 address. Because segments are limited to 8 bits, any address with a number higher than 255 (e.g., 258.0.0.3) is mathematically impossible.
Security & Encryption
Requirement 1.3.2: Students must understand the concept of encryption.
What is Encryption?
Encryption is the principle of scrambling data prior to transmission over a network.
Why is it necessary?
When data travels across a public network it can be intercepted by malicious 'packet sniffers'. Because the data was encrypted, the intercepted packet remains completely meaningless and unreadable to unauthorised users.
Stretch & Challenge (AO2 Application)
Written Exam Scenario (AO2/AO3)
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