2.7 - Protocols
Exam Board:
OCR
Specification:
2016 - Unit 1
What is a protocol?
A protocol is a set of rules that allow devices on a network to communicate with each other.
IP (Internet Protocol) is in charge of routing and addressing data packets to ensure data is transferred across networks to the correct destination.
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It is also an addressing system - every device on a network is given a unique IP address.
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TCP and IP are often used together to transfer data across the internet.
UDP (User Data Protocol) is a faster alternative to TCP for transferring data. It is used where low latency ('low lag') is important, such as online gaming and video chat.
However, UDP does not automatically check for errors so packets are more likely to be lost or received out of order.
HTTP is a protocol that can be used to transfer web pages on the world wide web so that users can view them in a web browser.
All URLs start with either HTTP or HTTPS (e.g. https://www.csnewbs.com).
HTTPS is a more secure version of HTTP that works with another protocol called SSL (Secure Sockets Layer) to transfer encrypted data.
You should see a padlock symbol in the URL bar if your connection to that website is secure.
HTTP/HTTPS
(Hyper Text Transfer Protocol)
FTP
(File Transfer
Protocol)
FTP (File Transfer Protocol) is used to transfer files across a network. It is used most often to upload or download files to/from a file server.
ICMP (Internet Control Message Protocol) collects network status information (such as router errors) and is used for troubleshooting.
SNMP (Simple Network Management Protocol) is a protocol that records network statistics, such as router usage.
Network Management Protocols
Protocols
SMTP (Simple Mail Transfer Protocol) is a protocol used to send emails to a mail server and between mail servers.
POP (Post Office Protocol) is for downloading and storing emails from a mail server.
TCP/IP Protocol Stack
The TCP/IP protocol stack is a model split into 4 layers. The model is used to visualise the different parts of a network as each of the four layers has a specific role.
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Splitting a network design into layers is beneficial to programmers as it simplifies design, making it easier to modify and use.
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Each layer has a certain purpose and is associated with different protocols.
4
Allows humans and software applications to use the network e.g. browsers (HTTP/HTTPS), email (SMTP/POP), file transfer (FTP) and network management (SNMP) applications.
3
TCP breaks the data down into data packets. This layer makes sure the data is sent and received in the correct order and reordered at the destination without errors. UDP can also be used for faster, but less reliable, data transfer.
2
The network layer is also known as the 'Internet Layer'. IP is responsible for addressing and routing data packets. The optimal route for the data to take is calculated in this layer. ICMP may be used here for network monitoring.
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1
This layer handles transmission errors and passes data to the physical hardware such as routers. It also sets out the final format of data packets.
Questo's Questions
2.7 - Protocols:
1. Describe each of the following protocols.
Also, state the protocol's full name and draw an icon or diagram for each:
a. TCP
b. IP
c. UDP
d. HTTP & HTTPS
e. FTP
f. ICMP
g. SNMP
h. SMTP
i. POP [1 each]
2. State which protocol would be used in the following scenarios:
a. Transferring a music file to a friend over the internet.
b. Sending an email to a friend in Japan.
c. Checking for errors on a network.
d. Having a video call with a colleague in London.
e. Receiving an email from the bank.
f. Watching a video on YouTube.
g. Checking the statistics of usage on a network [1 each]
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3. Summarise each layer of the TCP/IP stack and identify the protocols used in each layer. [8]