Topic 5: Communication and the Internet Protocols

Communication and the Internet: Protocols When communicating between different devices, a set standard of messages/data needs to be set up These standards are called protocols They let devices know when to send data, when to listen for data, and what to do when it receives data The are all kinds of protocols out there Each for different uses Communication and the Internet: Protocols

Communication and the Internet: Protocols Here’s a list of the ones we need to know There are lots more out there, each for a different thing Let’s run through these and see what they do Connectivity IP Ethernet WiFi Applications HTTP HTTPS FTP Email POP3 SMTP IMAP TCP/IP Communication and the Internet: Protocols

Communication and the Internet: Protocols Protocols: IP Stands for Internet Protocol Made use of in other protocols (like TCP/IP) to enable Internet connectivity between devices Commonly found in IP Addresses, which are 4- byte numbers representing the ‘location’ of a device For example: 192.168.1.40 Communication and the Internet: Protocols

For example: 2001:0DB8:AC10:FE01 Protocols: IP We assign a unique IP address to every LAN controller (like a router) on the Internet Known as a public IP address We are ending up with fewer IP addresses to use every day The current system is known as IPv4 (for 4-bytes) We’re slowly moving over to IPv6 (which has 16-bytes) For example: 2001:0DB8:AC10:FE01 Communication and the Internet: Protocols

Communication and the Internet: Protocols Protocols: Ethernet A technology created for getting devices communicating on a LAN Over a wired medium This involves ‘sensing’ the cable the device uses for transmission and sees if it is free If it is, the device sends the data down the cable If not, it waits for a bit Similar to CSMA/CA Often uses ‘ethernet’ cables (Cat5, Cat5e, Cat6), which contain twisted pairs of cables inside them Communication and the Internet: Protocols

Communication and the Internet: Protocols Protocols: WiFi A technology created for getting devices connected to a LAN wirelessly Involves using a transmitter to send radio waves at specific frequencies 2.4 GHz, or 5 GHz A receiver (i.e. on the router) will detect these waves and read the transmission Used in lots of devices (laptops, phones, consoles, and more) Communication and the Internet: Protocols

Communication and the Internet: Protocols Protocols: TCP/IP The protocol that we don’t see everyday, but is used every day, is TCP/IP Transfer Control Protocol/Internet Protocol Allows for the communication between devices over a network (i.e. the Internet) Provides end-to-end communication, which includes: Breaking data into packets Addressing, transmitting, and routing packets Receiving and recombining packets Communication and the Internet: Protocols

Communication and the Internet: Protocols Protocols: TCP/IP TCP/IP works via four layers Called the TCP/IP Stack These layers affect the data to be sent in different ways One adds the payload (data we want to sent) One adds the addressing information We need to know all of them Communication and the Internet: Protocols

Communication and the Internet: Protocols Protocols: TCP/IP This layer handles the communication between applications and other layers on this stack This is where the protocols mentioned earlier kick in They communicate with each application (using the correct protocol) Building the payload that needs to be sent This data is then passed on to the next layer in the stack Application Application Transport Network Link Communication and the Internet: Protocols

Communication and the Internet: Protocols Protocols: TCP/IP Supports the Application Layer by giving it certain communication services Allows the payload to be attached to a packet Makes use of two protocols TCP: one-to-one reliable communications, large data UDP: User Datagram Protocol, handles small data, unreliable Application Transport Network Link Transport Communication and the Internet: Protocols

Communication and the Internet: Protocols Protocols: TCP/IP It’s this layer that is the key layer in the end- to-end communication It starts and ends the two end- system communication When it receives the data from Application layer It can, if needed, split this data into segments For sending over the end-to-end connection Recombines these segments on the receiving end Application Transport Network Link Transport Communication and the Internet: Protocols

Communication and the Internet: Protocols Protocols: TCP/IP This layer also monitors the connection For any problems Will retransmit a segment if a problem is found This layer adds a header (a TCP header) to each segment Contains source and destination ports The sequence number of the segment An acknowledgment value A checksum Application Transport Network Link Transport Communication and the Internet: Protocols

Communication and the Internet: Protocols Protocols: TCP/IP Assembles the complete packet to be sent Adds IP address information (both source and destination) To the original payload Handles the ‘Internet’ connectivity part of the stack Application Transport Network Link Application Transport Network Link Transport Network Communication and the Internet: Protocols

Communication and the Internet: Protocols Protocols: TCP/IP Puts the packet to be sent into a frame Maps IP addresses to hardware MAC addresses Assembles the final piece of data to be sent out over the network medium Application Transport Network Link Link Communication and the Internet: Protocols

Application Application Transport Transport Network Network Link Link Protocols: TCP/IP Application Application Transport Network Link User Data Application Protocol Header Transport Application Data TCP Header Network Application Data TCP Header IP Header Link Application Data TCP Header IP Header Ethernet Header Communication and the Internet: Protocols

Protocols: HTTP & HTTPS Stands for Hypertext Transfer Protocol And Hypertext Transfer Protocol Secure HTTP determines how hypertext is transferred from one device to another Hypertext: any text that links to more text/files One of the most common protocols used (as it’s used for showing websites) HTTPS is an encrypted, secure form of HTTP (used on websites that need security, like merchants or banks) Communication and the Internet: Protocols

Protocols: HTTP & HTTPS For viewing webpages, we need to use HTTP or HTTPS HTTP is the standard HTTPS was created (with the help of SSL) to make a more secure version This also requires two pieces of hardware Server: will host the files (e.g. HTML files) and send them to clients when requested Client (a browser): will send GET requests to servers to retrieve the files they show (and then show them on the browser window) Communication and the Internet: Protocols

Protocols: HTTP & HTTPS When clients (browsers) retrieve data from web servers, they render them Usually parse through a scripting language (like Hypertext Markup Language, HTML) Will then add text/images/video/animations to the browser window as needed HTTPS was created to make more secure connections to keep any sensitive data (like passwords) secret Communication and the Internet: Protocols

Communication and the Internet: Protocols Protocols: FTP Stands for File Transfer Protocol The main protocol used for sending data (files) from one device to another Usually sends files, or receives files from, a FTP server All FTP communications happen between a client and a server For example, FileZilla offers a client and a server The server hosts the files (data), and accepts control instructions As well as data to save, when needed The client simply manages access to the server Communication and the Internet: Protocols

Communication and the Internet: Protocols Protocols: FTP FTP allows for both anonymous and logged-in connections Anonymous: no login associated with connection Logged-in: connected to a specific account Restrictions can be applied to both types Logged-in users could only access their user folders Anonymous users might only be able to download files (not upload) Communication and the Internet: Protocols

Communication and the Internet: Protocols Protocols: POP3 Stands for Post-Office Protocol 3 The most recent version of the main protocol used for receiving email Hosts emails on a server, which are downloaded periodically onto a client machine via an Email Client (e.g. Outlook) These downloaded emails are typically deleted from the server Communication and the Internet: Protocols

Communication and the Internet: Protocols Protocols: SMTP Stands for Simple Mail Transfer Protocol Used for sending email from one client to a server/another client Users use this in conjunction with POP3 to handle all email needs Communication and the Internet: Protocols

Using POP3 and SMTP Together For sending and receiving emails, we need two pieces of hardware and two protocols Hardware: Email server and client program Protocols: POP3 (for receiving emails) and SMTP (for sending emails) The email server will store all the emails sent to it, and any emails sent from it It’s where all emails are actually sent A client program (e.g. Outlook) will then periodically request emails from the server Using POP3 Communication and the Internet: Protocols

Communication and the Internet: Protocols Protocols: IMAP Stands for Internet Message Access Protocol Functions similarly to POP3 Where it lets us access our emails And a server is still required However, IMAP syncs the emails between the mail server and the client Keeping the emails on the server Lets multiple clients stay synced with the server Communication and the Internet: Protocols