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Protocol, is a set of rules or conventions to perform a task
Protocol Architecture, is a strategy where the tasks of communication are broken up into modules where eac modules can have its own protocol. In very general terms, communications can be said to involve three components : applicants, computers and networks.
Need for Protocol Architecture
To do the transfer data mechanism, several tasks must be performed
:
1)
The source must activate communications path or
inform network of destination
2)
The source must make sure that the destination is
ready to receive data
3)
The file transfer application on source must
confirm file management program and the destination is prepared to accept and
store the data
4)
A certain format file translation may be needed
to perform (if the formats on systems are different)
Functions of Protocol Architecture
a.
Breaks logic into subtasks modules to be
implemented separately
b.
Subtasks are arranged in a vertical stack layer,
in which :
(i)
Every layer performs a sub-set of functions
(ii)
Relies on the next lower layer to hold a
primitive function
(iii) Changes in a layer don’t require changes in other layers
SIMPLIFIED FILE TRANSFER
Key Elements of a Protocol
Ø Syntax
Syntax refers to the structure or the
format of data and signal levels. It is responsible to indicate how to read the
data and how the data is presented to the receiver.
Ø
Semantics
Semantics refers to defining each section
to decide what action needs to be taken. Semantics is consisted of control
information for coordination and error handling.
Ø
Timing
Timing refers to:
-
When will the data be sent?
-
What will be the speed of sending and receiving
the data?
Timing performs speed matching,
sequencing, and flow control of the data items
Protocol Architecture
This refers to layered structure to support the exchange of
data between application systems. In protocol architecture tasks of communication
are broken up into modules where each module or layer could have its own protocol.
In general terms, communications can be said to involve three components, those
are applications, computers, and networks.
A Three Layer Model
A.
Network Access Layer
This functiuns to solve the problem of exchanging
data between two or more directly connected devices. This layer is responsible
to destination address provision and invoking services like priority. This
layer supports point-to-point communications and multiple access communication.
Example of link layer protocol : Point-to-pont
protocol and Wireless LAN.
B.
Transport Layer
Transport layer transports messages between
the client application and the server application. The transport layer provodes
reliable, transparent transfer odf data between computers. The use of transport
layer is determined by the network being used and the application
C.
Application Layer
Application Later contains communication sevices
that include file transfer and message handling like Telnet and email.
Addressing Requirements
Address is used to identify the sender and the destinations.
In communication systems, two-level addressing is required. The first address is
used to identify the end system such as computer while another address is used
to each application on a (multi-tasking)
computer needs a unique address
within the computer.
Protocol Data Units (PDU)
A PDU refers to a specific block of information transferred
over a network.
On each layer, protocol us used for communication. The control
information is given to user data at each layer. Each layer has its own function.
For example, transport data is capable to separate the user data. Each
fragments could be added to the transport’s header. This gives the transport a
protocol data unit.
Standarized Protocol Architecture
Standarized Protocol Architecure consists of things that are
required to perfom communication. There are two standards :
i.
OSI REFERENCE MODEL
ii.
TCP/IP Protocol suite
This
is the most ised protocol architecture
OSI (Open System Interconnection)
OSI was developed by the International Organization for
Standadrization (ISO). OSI consisted of seven layers protocols. Since OSI never
lived up to fulfil its early promises, it is considered a theoretical system
delivered too late.
The OSI is a conceptual model that parts the flow of data
communication systems into seven abstraction layers. Each layer has its own
functions to perform communication. Each
intermediate layer serves a class of functionality to the layer above it and is
served by the layer below it.
In this system, the change
in a layer doesn’t require the change in other layers.
OSI LAYERS
We’ll describe OSI layers “top down” from the application layer that directly serves the end-user, down to the physical layer.
7. Application Layer
The application layer is used by end-user to access all information services such as web browsers and email clients. It provides protocols that allow applications to send and receive information and present them.
6. Presentation Layer
The presentation layer prepares data for the application
layer. It provides independence to the application processes from differences in data representation or syntax. This includes, how two devices should encode, encrypt, and
compress data so it is received properly on the other end.
5. Session Layer
The session layer creates communication channels, called sessions, between devices. It is responsible for establishing, managing and terminating connection (session between applications. The session layer can also set checkpoints during a data transfer—if the session is interrupted, devices can resume data transfer from the last checkpoint.
4. Transport Layer
The transport layer takes data transferred in the session layer and breaks it into “segments” on the transmitting end. It is responsible for reliable and transparent transfer of data between points. The transport layer carries out flow control, sending data at a rate that matches the connection speed of the receiving device, and error control, checking if data was received, and if not has the ability to request it again.
3. Network Layer
The network layer has two main function, provides upper layer with indepence from the data transmission and switching technology ised to connect system. The network layer uses network addresses (typically Internet Protocol addresses) to route packets to a destination node.
2. Data Link Layer
The data link layer establishes and terminates a connection between two physically-connected link. It performs error checking and synchronizes frames, and and define permissions to transmit and receive data.
1. Physical Layer
The physical layer is responsible for the physical cable or
wireless connection between network nodes. It defines the connector, the
electrical cable or wireless technology connecting the devices, and is
responsible for transmission of the raw data.
TCP/IP Protocol Architecture
This protocol architecture is developed by the US Defense
ADdvanced Research Project Agency (DARPA) for its packets switched network. TCP/IP
is used by the global internet and consists
a large collection of protocols. The TCP/IP protocol architecture manage
the communiactions task into five relatively independent layers:
a.
Physical Layer
The physical layer covers the physical
interface between a data transmission device and a transmission medium or
network. Physical layers send individual bits fromo ne node to a directly connected
node.
b.
Network Access Layer
Responsible in the data exchange between devices.
The services provided by network access layer depent on the specific link-layer
protocol.
c.
Internet Layer (IP)
The internet layer routes a data through a
series of packet with the help of the routers between source and destination. The
system in this layer may be attached to different networks.
d.
Transport Layer
Transport layer send out massages between
the cuser application and the server application. In this case, Transport Layer
should be realible in terms delivering the data.
e.
Application Layer
Application layer provides the communication
protocols and interface method needed such as user login, formatting messages, etc.
TCP
TCP provides reliable communication with no data loss, no
erorrs, no out-of-order data sent with recovery feature. TCP is a
connection-orriented stream service, means that a connection setuo needs to be
done to run TCP. Unfortunately, TCP only supports point-to-point communication
between two hosts and cannot support multicast or broadcast. With those
features, TCP has larger overhead.
A TCP application generates data as a byte steram
UDP
UDP is an alternative of TCP. UDP itself doesn’t guarantee
the safety of the data during the delivery, doesn’t orovides in-order data, and
no protection against duplication. The plus point of UDP is the minimum
overhead to support real-time communication.
TCP/IP Concepts
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TCP IP Stack explained with real world example
A gentleman packed his luggage neatly. He wants to move to a new residence or new apartment which is a few kilometers away from his current residence. He hired a courier company to help him to move.
Elements Mapping :
a. The gentleman: an application
b. His luggage : an application data
c. Luggage Packing Activity : Session and Presentation Layer
d. Courrier Company : transport layer
e. The road to the destination: a network layer
f. Traffic Signals in Road : Data Link Layer
g. New Destination: IP Address Destination
So, the elaboration based on the mapping would be, to reach the destination, the application data needs to be packed and goes through the session and presentation layer. This layer is responsible for the encryption and decryption of data so that the data stay safe during the journey.
To deliver the data, we use the courier company which has mapped as the transport layer. The transport layer has two famous protocols, TCP and UDP. If the courier company is responsible for the safety of your data until the destination then you need to pick TCP while if the transport company do not take responsibility for the safety of your luggage then this courier company acts like UDP Protocol.
A network layer or the road to the destination is a path that takes your data from the source to the destination. While on the road, the courier will encounter the data link layer or pictured as the traffic signals. The vehicle will pass through these traffic signals hop by hop. Finally, the data arrives at the new destination that is mapped as an IP address destination.
Source :
CSE Practicals. 2018. TCP IP Stack explained with real world example.
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Learn How the Internet Works by Getting to Understand
the Details of Data's Journey
Data is stored in the SSD (Solid State Device) in the data center. To arrive at your device, we can use a technology called satellite. From the data center, a signal is sent to the satellite and then the satellite sends the signal to your mobile phone or other devices. However, this technology is not always effective since the satellite is parked far away from our place. The data needs to travel such a long distance and may cause a significant delay in receiving the signal or specifically a huge latency.
There is better technology, a complicated network of optical fiber network which connects between the data center and your device. Before explaining how the data travels from the data center to your devices, we need to comprehend the concept of IP Address. IP Address is a string of numbers used to identify every device that is connected to the internet. On the internet, IP address acts as a shipping address through which all information reaches its destination. And then we have 'The Server'. The server is responsible to provide you the data when you browse it or when you request it.
The server also has an IP address. The server stored a website that can be accessed by the server's IP address. The domain name of a website to correspond with the server's IP address such as youtube.com or instagram.com is made to make it easier to access certain information.
To access the internet, we use the domain name, not the IP address. For this purpose internet uses DNS. DNS works like a phone book where we can search phone numbers based on people's names. The internet service provider can manage the DNS server.
How the information can get into your screen?
1. Enter the Domain Name of a website
2. A request is sent to the DNS server to respond to a certain IP address
3. After getting the IP address, the browser forwards the request to the data center (respective server)
4. The server receives the request
5. The data is transferred in the form of light pulses via OPC (Optical Fiber Cables)
6. The light pulses go to a long journey and pass through some terrains
7. The light gets into your closest tower or certain cell towers
If the light gets into your closest router, the next step would be
8.1 The router converts the light signals to electrical signals
9.1 The ethernet cable transmits the electrical signals to your connected devices
If the light is sent to a cell tower, the next step would be
8.1 From the cell tower, a signal will reach your devices in the form of electromagnetic waves.
The efficiency of transmitting data by the internet is how the ability to transfer the data that consisted from zeros or ones (the binary numbers). These zeros and ones are divided into packets consisted of 6 bits. The bits also consists of the sequence number and the IP address of the source and the destinations. After that, the packets are routed through a certain path to reach your phone. To be accessible, the packets are reassembled according to their sequence number to identify the IP address' destination. Finally, the information can arrive at your device with the help of certain protocols to manage the complex data flow.
Source :
Learn Engineering. 2019. How Does the Internet Work?|ICT #2
_________________________________________________________________________________
Dawn of the Net - How the Internet Works
Technology that supports communication help to bring people together. The information can be easily accessed just by typing and clicking letters on your devices. The data then goes to a long journey before reaching our devices.
(i) When you browse certain information, a flow of data in the form of zeros and ones goes down into a personal mailroom
(ii) Each packet is then labeled. The label contains important information such as senders and receivers IP address, and the type of packet. It also gets stamped of the address for the proxy server.
(iii) The packet goes to LAN (Local Area Network) for information exchange.
(iv) To control the complex data flow, the local router reads the address and put the packet onto the right network. A router helps to organize the data traffic.
(v) The packets leave the router and go into the corporate intranet then heads to the router switch. The router switch is responsible to efficiently route the data quickly and loose.
(vi) The packets then picked up by the network interface to be sent to the proxy. The proxy is used for security reasons. The proxy is responsible to open the packet and search for the web address or URL. If the address is acceptable, the packet will continue its journey on to the internet. However some addresses are not proper, the proxy will destroy the URL so it doesn't reach the internet.
(vii) Next, the packets will face the firewall. The firewall serves two purposes, it prevents improper information from the internet from coming into the internet into intranet and it could also prevent sensitive corporate information from being sent put on to the internet.
(viii) After that, a router takes the packages and puts them on a narrower path or bandwidth.
(ix) Finally, the packets are able to enter the world of the internet, interconnected networks.
(x) The packet then needs to face another firewall to filter out whether the packets meet the criteria. The packets get into certain ports based on their function (port 25 is used for mail packets, port 80 is the entrance to the web server, etc). In some cases, the packets need to be destroyed inside the firewall.
(xi) The packet is now ready to be taken to the webserver. The packets are received and opened. The information is unpacked and sent to the webserver, available on your screen.
The empty packet itself is then recycled, ready to be used again.
Source : TNG Medialab. 2011. Dawn of the Net - How the Internet Works
https://www.youtube.com/watch?v=hymzoUpM0K0&t=692s
Why UDP and TCP exist?
Transport Protocol
There are two major transport protocols
A. UDP (User Datagram Protocol)
· Advantages
a) The sizes are smaller than TCP
b) UDP need no connection to create and maintain before sending out data
c) The users have more control over when the data is being sent
· Disadvantages
a) When UDP detect data corruption, it doesn’t try to recover. Usually, the corrupted segments will be discarded. In some cases, it will keep the corrupted segment but turn on a warning flag for the application.
b) To add another point, UDP doesn’t compensate for the lost packets. UDP doesn’t guarantee in-order packets delivery. That’s why packets can arrive out of order
c) There’s no congestion control in UDP. This is a bad strategy, because in congested network packets get dropped more often. In conclusion, UDP might be lightweight but it is not reliable.
· UDP is message-oriented, which means the application sends data in distinct chunks
B. TCP (Transmission Control Protocol)
· TCP is a connection based, that’s why we need to negotiate a connection first with a procedure called the three-way handshake.
· Three-way handshake :
1. The initiator asks the acceptor if it wants to set up a connection
2. The acceptor respond to the request
3. If the acceptor accepts the request, the connection is established
· ADVANTAGES
a. Delivery Acknowledgements :
When data is sent from one host to another, the receiver will acknowledge that it got the data.
b. TCP offers retransmission :
When the sender doesn’t get a delivery acknowledgement, the packet is considered lost on its way, so it will send it again.
c. In-order delivery :
In TCP, the segments are numbered based on the order delivery. Although packets may still arrive out of order. TCP will rearrange them before sending them to the application.
d. Congestion Control :
TCP will delays the transmission of data when the network is congested. This will help the strain of the network and minimize packet lost.
e. Error Detection :
The checksum has been made mandatory for ipv4 as well as ipv6
· DISADVANTAGES :
a. Need bigger headers than UDP segments
The side effect of the TCP’s congestion control mechanism is that data doesn’t always get sent out immediately. When the network is congested, it will introduce latency so it will not be suitable for “real-time communication app”
b. Has a bigger overhead,
TCP has to do retransmission of packets and acknowledgement of packets. Example: need more bandwidth to stream HD video. In this case, it makes more sense to use UDP.
TCP is stream-oriented. It is used as a continuous flow of data. In TCP, the data is split up in chunks by TCP. Whenever anything needs to be sent, TCP will slice that into packets and recompose everything.
CONCLUSION :
The usage of TCP and UDP depends on the type of application that you’re building. For example, a text communication. Under TCP everything will work fine, with UDP you could get the text in the wrong order or your text might get lost along the way with no guarantee. When it comes to text communication, TCP is the right protocol to use.
With multimedia streaming, you can use both UDP and TCP
With UDP, it has less overhead, it doesn’t do the congestion control that introduces latency and data loss could be masked. UDP could be used for small questions-and-answer transaction since UDP doesn’t need to create the connection first, such as DNS lookups.
With good connection, we can use TCP and enjoy the benefits that it brings. Most people use TCP because some firewalls block UDP for security reasons.
Source : PieterExplainsTech. 2013. UDP and TCP: Comparison of Transport Protocols
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