File Name: tcp ip layers and protocols .zip
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This whitepaper explains the underlying infrastructure and technologies that make the Internet work.
This whitepaper explains the underlying infrastructure and technologies that make the Internet work. It does not go into great depth, but covers enough of each area to give a basic understanding of the concepts involved. For any unanswered questions, a list of resources is provided at the end of the paper. Any comments, suggestions, questions, etc. Where to Begin? Internet Addresses Because the Internet is a global network of computers each computer connected to the Internet must have a unique address.
Internet addresses are in the form nnn. This address is known as an IP address. IP stands for Internet Protocol; more on this later. The picture below illustrates two computers connected to the Internet; your computer with IP address 1. The Internet is represented as an abstract object in-between.
As this paper progresses, the Internet portion of Diagram 1 will be explained and redrawn several times as the details of the Internet are exposed.
In any case, if you are connected to the Internet, your computer has a unique IP address. It's called ping , probably after the sound made by older submarine sonar systems. If you're using a flavor of Unix, get to a command prompt. Type ping www. The pinged computer will respond with a reply. The ping program will count the time expired until the reply comes back if it does. Also, if you enter a domain name i. More on domain names and address resolution later.
Protocol Stacks and Packets So your computer is connected to the Internet and has a unique address. How does it 'talk' to other computers connected to the Internet? An example should serve here: Let's say your IP address is 1. The message you want to send is "Hello computer 5. Obviously, the message must be transmitted over whatever kind of wire connects your computer to the Internet.
Let's say you've dialed into your ISP from home and the message must be transmitted over the phone line. Therefore the message must be translated from alphabetic text into electronic signals, transmitted over the Internet, then translated back into alphabetic text.
How is this accomplished? Through the use of a protocol stack. Every computer needs one to communicate on the Internet and it is usually built into the computer's operating system i. Windows, Unix, etc. Hardware Layer Converts binary packet data to network signals and back. If we were to follow the path that the message "Hello computer 5. If the message to be sent is long, each stack layer that the message passes through may break the message up into smaller chunks of data.
This is because data sent over the Internet and most computer networks are sent in manageable chunks. On the Internet, these chunks of data are known as packets. Each packet is assigned a port number. We need to know which program on the destination computer needs to receive the message because it will be listening on a specific port. This is where each packet receives it's destination address, 5. Now that our message packets have a port number and an IP address, they are ready to be sent over the Internet.
The hardware layer takes care of turning our packets containing the alphabetic text of our message into electronic signals and transmitting them over the phone line. On the other end of the phone line your ISP has a direct connection to the Internet.
The ISPs router examines the destination address in each packet and determines where to send it. Often, the packet's next stop is another router. More on routers and Internet infrastructure later. Eventually, the packets reach computer 5. As the packets go upwards through the stack, all routing data that the sending computer's stack added such as IP address and port number is stripped from the packets.
When the data reaches the top of the stack, the packets have been re-assembled into their original form, "Hello computer 5. But what's in-between? What actually makes up the Internet? Let's look at another diagram: Diagram 3 Here we see Diagram 1 redrawn with more detail.
The physical connection through the phone network to the Internet Service Provider might have been easy to guess, but beyond that might bear some explanation. The ISP maintains a pool of modems for their dial-in customers. This is managed by some form of computer usually a dedicated one which controls data flow from the modem pool to a backbone or dedicated line router. This setup may be refered to as a port server, as it 'serves' access to the network. Billing and usage information is usually collected here as well.
From here the packets will usually journey through several routers and over several backbones, dedicated lines, and other networks until they find their destination, the computer with address 5.
But wouldn't it would be nice if we knew the exact route our packets were taking over the Internet? As it turns out, there is a way This one is called traceroute and it shows the path your packets are taking to a given Internet destination. Like ping, you must use traceroute from a command prompt. In Windows, use tracert www. From a Unix prompt, type traceroute www. Like ping, you may also enter IP addresses instead of domain names. Traceroute will print out a list of all the routers, computers, and any other Internet entities that your packets must travel through to get to their destination.
If you use traceroute, you'll notice that your packets must travel through many things to get to their destination. Most have long names such as sjc2-core1-h These are Internet routers that decide where to send your packets. Several routers are shown in Diagram 3, but only a few.
Diagram 3 is meant to show a simple network structure. The Internet is much more complex. Internet Infrastructure The Internet backbone is made up of many large networks which interconnect with each other.
These networks peer with each other to exchange packet traffic. NAPs were the original Internet interconnect points. Below is a picture showing this hierarchical infrastructure.
Diagram 4 This is not a true representation of an actual piece of the Internet. None of the physical network components are shown in Diagram 4 as they are in Diagram 3. This is because a single NSP's backbone infrastructure is a complex drawing by itself.
Most NSPs publish maps of their network infrastructure on their web sites and can be found easily. To draw an actual map of the Internet would be nearly impossible due to it's size, complexity, and ever changing structure. Does every computer connected to the Internet know where the other computers are? Do packets simply get 'broadcast' to every computer on the Internet?
The answer to both the preceeding questions is 'no'. No computer knows where any of the other computers are, and packets do not get sent to every computer. The information used to get packets to their destinations are contained in routing tables kept by each router connected to the Internet. Routers are packet switches. A router is usually connected between networks to route packets between them. Each router knows about it's sub-networks and which IP addresses they use.
The router usually doesn't know what IP addresses are 'above' it. Examine Diagram 5 below. The black boxes connecting the backbones are routers.
Under them are several sub-networks, and under them, more sub-networks. At the bottom are two local area networks with computers attached. Diagram 5 When a packet arrives at a router, the router examines the IP address put there by the IP protocol layer on the originating computer.
The router checks it's routing table. If the network containing the IP address is found, the packet is sent to that network. If the network containing the IP address is not found, then the router sends the packet on a default route, usually up the backbone hierarchy to the next router. Hopefully the next router will know where to send the packet. If it does not, again the packet is routed upwards until it reaches a NSP backbone.
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the TCP/IP protocol suite (see , “The TCP/IP protocol layers” on page 6). BOOTP protocol, is a “second edition,” being a revision of RFC and an.
The Internet protocol suite is the conceptual model and set of communications protocols used in the Internet and similar computer networks. Its implementation is a protocol stack. The Internet protocol suite provides end-to-end data communication specifying how data should be packetized, addressed, transmitted, routed , and received. This functionality is organized into four abstraction layers , which classify all related protocols according to the scope of networking involved.
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The OSI Model is a logical and conceptual model that defines network communication used by systems open to interconnection and communication with other systems. The Open System Interconnection OSI Model also defines a logical network and effectively describes computer packet transfer by using various layers of protocols. In this TCP Model vs.
This article lists protocols , categorized by the nearest layer in the Open Systems Interconnection model. This list is not exclusive to only the OSI protocol family. From Wikipedia, the free encyclopedia. Wikipedia list article. This article is about network protocols organized by OSI model. This article needs additional citations for verification. Please help improve this article by adding citations to reliable sources.
It helps you to create a virtual network when multiple computer networks are connected together. TCP is a connection-oriented protocol. TCP offers reliability and ensures that data which arrives out of sequence should put back into order. TCP allows you to implement flow control, so sender never overpowers a receiver with data. The application layer is the OSI layer, which is closest to the end-user. It means the OSI application layer allows users to interact with other software application.
The main purpose of OSI Model was to guide vendors, manufacturer, and the developers so the digital communication products and software programs can interoperate, and facilitate a clear framework that describes the functions of networking or a telecommunication system. Transport is a direct 1 to 1 mapping. Share it!
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