Networking

Protocols

Protocols provide an agreed set of rules to allow networked devices to communicate.

Network protocols are important as programs where a programmer invents their own protocol would be unable to communicate with other programs.

Networking Standards

It is important to have networking standards. The reasons are outlined below:-

Ensures that hardware and software produced by different vendors can work together
Without networking standards, it would be difficult / impossible to develop networks that easily share information
Standards mean that customers are not locked into one vendor
Standards help to promote more competition and hold down prices
The use of standards makes it much easier to develop software and hardware that link different networks because software and hardware can be developed one layer at a time.

TCP

The protocol that allows packets to be sent and received between computer systems

TCP/IP

This is the basic communication protocol used on the Internet.

It allows any networked computers to communicate with each other.

This is important as TCP/IP specifies how signals are routed and transported around a network (and reduces the need for gateways to convert signals into different protocols).

IMAP (Internet Message Access Protocol)

A protocol that stores email messages on a mail server

Allows a user to download an email from a mail server
This is important as the IMAP provides a standard way of transferring emails between two different servers/messages are stored on the server instead of mobile devices, which saves storage space.

HTTP (Hyper Text Transfer Protocol)

Transfers webpages over a network
Transferring multimedia web pages over the Internet.
This is important as the HTTP protocol allows multiple different web browsers to display and format web pages as the original author intended.

Dynamic Host Configuration Protocol (DHCP).

Assigning (dynamic) IP addresses to devices on a network.
Obtaining an IP address from a server
This is important as the DHCP protocol ensures that unique/dynamic IP addresses are allocated / allows addresses no longer in use to be automatically returned to the pool of available IP addresses for reallocation.

File Transfer Protocol (FTP)

For the exchange of large files over the Internet/network
e.g. uploading/downloading files to a website
This is important as the FTP protocol has in built error checking and re-transmission request as necessary

SMTP (Simple Mail Transfer Protocol).

Sending an email across a network / internet
Used to send email to an email server.
The protocol used to deliver email from the sender to an email server/It is the Internet standard for electronic mail (email) transmission
This is important as the SMTP protocol provides a standard way of transferring emails between two servers.

Universal Datagram Protocol (UDP).

• Sending datagrams across a network with very few error recovery services.

• Streaming multimedia

This is important as, for example, video and audio streaming protocols are designed to handle occasional lost packets and need to receive new packets rather than the transmission of previous ones.

SIP (Session Initiation Protocol)

SIP – session initiation protocol – stateless signalling used for setting up VoIP and media streaming.

APPLICATION - FTP

The FTP protocol is unsuitable for streaming a live video feed. The file transfer protocol, breaks data into packets and can re-send lost or damaged packets, it allows packets that have arrived in a random order to be reassembled. This is convenient for downloading files if network traffic is slows or some of your packets are dropped / arrive out of order.

However, the FTP protocol won't work as well for streaming media as it is more important to continue to receive new packets rather than retransmitting lost or dropped packets.

Voice and video traffic is can be transmitted using UDP. Real-time video and audio streaming protocols are designed to handle occasional lost packets, so only slight degradation in quality occurs, rather than large delays if lost packets were retransmitted.

KEY TERMS

HANDSHAKING
When a computer system establishes a devices readiness to communicate. It is the exchange of signals between devices to establish their readiness to communicate. Example: Establishing a printers readiness to print

COLLISION

Two sets of data are sometimes detected simultaneously on a bus network. This is known as a collision.
The collision detection process involves monitoring the network to identify when a collision occurs
The way in which the network deals with it is the transmitting nodes waits a random amount of time before trying to resend the packet

INTERNET
The internet is a world-wide communications infrastructure. A network of networks.

MULTIPLEXING
Multiplexing is where several independent data sources are combined to be sent along a single route to a specific destination e.g. Cable tv receives all the channels using a single cable only because of multiplexing only.

PROTOCOL
Protocols provide an agreed set of rules to allow networked devices to communicate. Network protocols are important as programs where a programmer invents their own protocol would be unable to communicate with other programs.

PACKED SWITCHED NETWORK

The way is which traffic is routed on a packed switched network is shown below:-

Data is split into packets
Each packet has a destination address
Packets are analysed by each node
Packets are sent down the most appropriate path (lowest cost / traffic) to reach its destination
Each node maintains a routing table
Packets may take different routes.
Packets are reassembled at their destination

How is data transmitted over a network using TCP/IP?

Data transmitted over a network are carried in messages called data packets. The contents of a typical datagram are:

Header – sender’s IP address, receiver’s ID address, protocol, packet number.
Payload – data.
Trailer – data to show the end of the packet and error correction.

What is routing?

Routing is the process of sending datagrams using IP addresses. Routing tables exist in devices such as switches and routers. This will forward the datagram to the best path towards its destination on the network.

What is the difference between IPv4 and IPv6?

The IP protocol is in charge of delivering datagrams from the source host to the destination using an IP address.

There have been a number of different versions of IP. A lot of modern technology will use IPv4. This uses a 32-bit address space that allows 4,294,967,296 different addresses.

With the development of the Internet, there has been a growing need for more IP addresses to be made available. Therefore, the latest version of the IP is IPv6. This uses a 128-bit address format, thus making a larger range of IP addresses available (2128).

Contents of a Packet

Items contained within a TCP/IP packet - Purpose of Item

Source Address - Allows tracing of sender
Destination address - allows packet to be routed to destination
Re-Assembly information/packet number - allows packets to be assembled in the correct order
Tracking information (Sequence & acknowledgement numbers) - allows route taken to be traced
The data itself - required as packet can contain meaningful data
Checksum (error handling)- allows checking of data for errors
Protocol type e.g. A protocol type in a data packet is a field that specifies which higher-level protocol is being used for the packet's payload.
Header Length
Flags
Payload size

TCP/IP 5 layer model Data Transmission

TCP/IP stands for Transmission Control Protocol/Internet Protocol. The majority of network communications rely on sets of protocols that are organised in layers to interconnect network devices.

There are two TCP/IP models, the four-layer model and five-layer model. The four-layer model combines the data and physical layers.

The layers of TCP/IP are:

Network Layer

• Responsible for the addressing and routing of data.

• Routers belong to the network layer as they use logical addresses to direct the data from the sender to the receiver.

• A router determines the path the data should take based on network conditions.

• Routers manage traffic problems on the network such as the routing of packets to minimise congestion of data.

Physical Layer

• The physical layer transmits the raw data. NOT packets.

• It consists of hardware such as switches and routers.

• The layer deals with all aspects of setting up and maintaining a link between the communicating computers

Application Layer

This layer uses the SMTP / IMAP protocols

Transport Layer

The Transport Layer uses the TCP protocol.

PROTOCOL REVISION QUIZZES

Protocol Revision Quiz 1

Protocol Revision Quiz 2 - TIP: If the quiz glitches after question 3, click on the NEXT button at the bottom of the quiz and it should allow you to progress to the next question.

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