Jul 13, 2016 02:17 PM
Open this spoiler for a prologue
Spoiler (Click to View)
Fundamentals are key. Fundamentals are the building blocks of what we come to know. Many people use a computer without understanding the magic that goes on in the background; but why would they need to know it? The truth is they don't. Unless you have a career in IT or are a hacker the chances of you arriving at a situation where you'd need to know anything regarded as anything more than 'basic' is as rare as hobby horse shit. We are in a time where everything is based on aesthetics and all of the things "under the hood" are tucked away from the eye of the consumer.
But the chances are that you clicked on this thread not because you're not an every day consumer but instead you may be aspiring to have a career in IT, you may want to get a greater understanding of networking so you can become a better, more knowledgeable ethical hacker. I don't know, and I won't make any more guesses, all I ask is that you act responsibly and use this thread as an educational source.
I've had the pleasure of being placed on a two week long Cisco Networking course. The course has been rather dull and boring. I was given a book called Cisco CCENT / CCNA ICND1 100-101. This book is around three inches thick and covers Networking to an absolute Tee. I recommend you pick it up if you're very interested in networking. It sells 40USD and 50CAD respectively, so yeah, you might want to purchase that, but without further adieu lets get into it.
Spoiler (Click to View)
Fundamentals are key. Fundamentals are the building blocks of what we come to know. Many people use a computer without understanding the magic that goes on in the background; but why would they need to know it? The truth is they don't. Unless you have a career in IT or are a hacker the chances of you arriving at a situation where you'd need to know anything regarded as anything more than 'basic' is as rare as hobby horse shit. We are in a time where everything is based on aesthetics and all of the things "under the hood" are tucked away from the eye of the consumer.
But the chances are that you clicked on this thread not because you're not an every day consumer but instead you may be aspiring to have a career in IT, you may want to get a greater understanding of networking so you can become a better, more knowledgeable ethical hacker. I don't know, and I won't make any more guesses, all I ask is that you act responsibly and use this thread as an educational source.
I've had the pleasure of being placed on a two week long Cisco Networking course. The course has been rather dull and boring. I was given a book called Cisco CCENT / CCNA ICND1 100-101. This book is around three inches thick and covers Networking to an absolute Tee. I recommend you pick it up if you're very interested in networking. It sells 40USD and 50CAD respectively, so yeah, you might want to purchase that, but without further adieu lets get into it.
Networking Fundamentals
Spoiler (Click to View)
In this thread we will be covering the TCP/IP Networking Model.
Some Acronyms to keep in mind...
TCP: Transmission Control Protocol
IP: Internet Protocol
UDP: User Datagram Protocol
HTTP: Hyper Text Transfer Protocol
PPP: Point-to-Point Protocol
POP3: Post Office Protocol 3
SMTP: Simple Mail Transfer Protocol____________________________________________________________
The TCP/IP Model defines a collection of protocols that ultimately allows computers to communicate.
____________________________________
TCP/IP Architecture Layer | Example Protocols____________________________________
Application | HTTP, POP3, SMTP____________________________________
Transport | TCP, UDP ____________________________________
Internet | IP____________________________________
Link | Ethernet , PPP, T1____________________________________
The TCP/IP Application layer protocols provide services to the application software running on a computer.
The application layer does not define the app itself, instead it defines the specific services the apps need.
For example, the app protocol HTTP defines how web browsers can interact and pull contents of a web page from a web server. In short the application layer acts as a medium between the software running on a computer and the network itself.
Although lots of TCP/IP application layer protocols exist, this isn't quite the case for the transport layer. The transport layer includes a lot fewer number of protocols, the two most common being TCP & UDP.
Transport layer protocols provide services to the application layer protocols that reside a layer higher in the TCP/IP model.
An example would be;
Bob and Larry used HTTP to transfer the home page web server Larry to Bobs web browser. BUT what would have happened had Bob's HTTP GET request had been lost in transit within the TCP/IP network? OR what would have happened if Larry's response, which included all the contents of the home page, had been lost? We're dun goof'd right? No, not quite, and here's how.
TCP/IP needs a mechanism to guarantee delivery of data across a network and because many application layer protocols probably want a way to ensure delivery of data across a network, the creators of TCP included an error-recovery feature. To recover from errors TCP uses the concept of acknowledgements, the follows diagram displays this and outlines the basic idea of how TCP notices when data has been lost and asks the sender to try again.
SEQ = Sequence Number
i.imgur.com/CgH4YsR(DOT)png
Okay so we're stepping through layers, the application layer has many protocols, the transport layer includes fewer but this network layer only really includes one major protocol (it does contain other protocols but this is only a basic thread). The main major protocol in question is the IP.
The IP provides several features, most importantly addressing and routing.
Imagine you have written two letters; one to a friend on the other side of the country, and one to a friend on the other side of town.
You addressed the envelopes and put on the stamps. So both are ready to give to the postal service, right? There's not much of a difference how YOU treat the letter, right? Right, however, the postal service needs to think about the letters separately and where to send them so that they are both delivered.
So for the letter for your friend across town, that's probably went straight into a local post office truck. BUT for the friend across the country that letter has probably been sent to another post office, then another one, and so on processing the letter and deciding where to send it next.
To make it all work, the postal service must have regular routes for small trucks, boats and planes etc. to move the letters between postal sites. These sites must be able to receive and forward letters, and also make good decisions on where to send each letter next.
i.imgur.com/StBEIkw(DOT)png
So what does this matter in networking?
Well the network layer of TCP/IP works much like the postal service. The IP defines that each host computer should have a different IP Address, just as the postal service defines addressing that allows unique addresses for each house, apartment and business. Similarly, IP defines the process of routing so that routers can work like the post office; forwarding packets of data so that they are delivered to correct destinations.
Just like every other layer, the TCP/IP link layer provides a service to the layer above in the model. When a host's or router's IP process chooses to send an IP packet to another router or host, that host or router then uses link-layer details to send that packet to the next host/router
When it gets to this level we start to get into data encapsulation. I can create more threads if this one gets a good response.
________________________
I hope this thread has been of some use to beginners looking into how networks actually work.
Spoiler (Click to View)
In this thread we will be covering the TCP/IP Networking Model.
Some Acronyms to keep in mind...
TCP: Transmission Control Protocol
IP: Internet Protocol
UDP: User Datagram Protocol
HTTP: Hyper Text Transfer Protocol
PPP: Point-to-Point Protocol
POP3: Post Office Protocol 3
SMTP: Simple Mail Transfer Protocol____________________________________________________________
Here is the original version of the TCP/IP Model
________
TCP / IP
Original ________
Application ________
Transport ________
Internet ________
Link ________
________
TCP / IP
Original ________
Application ________
Transport ________
Internet ________
Link ________
Here is the updated version of the TCP/IP Model
________
TCP / IP
Original ________
Application ________
Transport ________
Network ________
Data Link ________
Physical________
________
TCP / IP
Original ________
Application ________
Transport ________
Network ________
Data Link ________
Physical________
The TCP/IP Model defines a collection of protocols that ultimately allows computers to communicate.
____________________________________
TCP/IP Architecture Layer | Example Protocols____________________________________
Application | HTTP, POP3, SMTP____________________________________
Transport | TCP, UDP ____________________________________
Internet | IP____________________________________
Link | Ethernet , PPP, T1____________________________________
TCP/IP Application Layer
The TCP/IP Application layer protocols provide services to the application software running on a computer.
The application layer does not define the app itself, instead it defines the specific services the apps need.
For example, the app protocol HTTP defines how web browsers can interact and pull contents of a web page from a web server. In short the application layer acts as a medium between the software running on a computer and the network itself.
TCP/IP Transport Layer
Although lots of TCP/IP application layer protocols exist, this isn't quite the case for the transport layer. The transport layer includes a lot fewer number of protocols, the two most common being TCP & UDP.
Transport layer protocols provide services to the application layer protocols that reside a layer higher in the TCP/IP model.
An example would be;
Bob and Larry used HTTP to transfer the home page web server Larry to Bobs web browser. BUT what would have happened had Bob's HTTP GET request had been lost in transit within the TCP/IP network? OR what would have happened if Larry's response, which included all the contents of the home page, had been lost? We're dun goof'd right? No, not quite, and here's how.
TCP/IP needs a mechanism to guarantee delivery of data across a network and because many application layer protocols probably want a way to ensure delivery of data across a network, the creators of TCP included an error-recovery feature. To recover from errors TCP uses the concept of acknowledgements, the follows diagram displays this and outlines the basic idea of how TCP notices when data has been lost and asks the sender to try again.
SEQ = Sequence Number
i.imgur.com/CgH4YsR(DOT)png
TCP/IP Network Layer
Okay so we're stepping through layers, the application layer has many protocols, the transport layer includes fewer but this network layer only really includes one major protocol (it does contain other protocols but this is only a basic thread). The main major protocol in question is the IP.
The IP provides several features, most importantly addressing and routing.
Imagine you have written two letters; one to a friend on the other side of the country, and one to a friend on the other side of town.
You addressed the envelopes and put on the stamps. So both are ready to give to the postal service, right? There's not much of a difference how YOU treat the letter, right? Right, however, the postal service needs to think about the letters separately and where to send them so that they are both delivered.
So for the letter for your friend across town, that's probably went straight into a local post office truck. BUT for the friend across the country that letter has probably been sent to another post office, then another one, and so on processing the letter and deciding where to send it next.
To make it all work, the postal service must have regular routes for small trucks, boats and planes etc. to move the letters between postal sites. These sites must be able to receive and forward letters, and also make good decisions on where to send each letter next.
i.imgur.com/StBEIkw(DOT)png
So what does this matter in networking?
Well the network layer of TCP/IP works much like the postal service. The IP defines that each host computer should have a different IP Address, just as the postal service defines addressing that allows unique addresses for each house, apartment and business. Similarly, IP defines the process of routing so that routers can work like the post office; forwarding packets of data so that they are delivered to correct destinations.
TCP/IP Data Link + Physical Layer
Just like every other layer, the TCP/IP link layer provides a service to the layer above in the model. When a host's or router's IP process chooses to send an IP packet to another router or host, that host or router then uses link-layer details to send that packet to the next host/router
When it gets to this level we start to get into data encapsulation. I can create more threads if this one gets a good response.
________________________
I hope this thread has been of some use to beginners looking into how networks actually work.
