TCP and IP
Today’s world largely happens online. Of course, there are many things happening in the physical world, but we’ve never depended on the internet as much as now.
In that environment, knowing the ins and outs of certain crucial systems is becoming not only handy, but sometimes, necessary. This is the case with TCP/IP. If you want to know what’s going on with your internet connection, understanding these protocols will go a long way.
- TCP/IP is a suite of communication protocols essential to the Internet, with TCP (Transmission Control Protocol) responsible for establishing reliable, ordered data delivery, and handling congestion control, while IP (Internet Protocol) focuses on routing packets of data to their destination.
- The primary difference lies in their roles; IP operates at a lower level and doesn’t provide any guarantees about delivery, treating each packet independently. TCP, on the other hand, builds upon IP’s foundation to provide robust, error-checked and sequenced transport of data, ensuring complete data integrity.
- Essentially, IP ensures the data’s journey across networks, while TCP verifies the data’s successful arrival in its intended order and form. Together, they enable reliable, organized data transfer in a decentralized, heterogeneous network like the Internet.
What are TCP and IP?
When people refer to TCP/IP, they usually mean the entire set of internet procedures and rules. This is true, to a point – TCP/IP make a large part of the entire internet protocol suite, although they aren’t the only protocols in it.
The TCP/IP model exists in every computer and is used for communication with other devices through a network. The protocol suite is automated by default. If you understand how the suite works, you’ll have an easier time setting up network connections.
What does TCP/IP do?
TCP/IP regulates how computers transfer data packets through a network. The protocol suite establishes an end-to-end connection and tells devices how to break the data into packets. Then, protocols instruct the machines on how to address, transmit, route, and receive the data packets to ensure data arrives where it needs to be.
The protocols are crucial because they handle communication between computers that may be on different continents and controlled by people who don’t speak the same language. The TCP/IP model overcomes those barriers by providing a universal way of machine communication.
When two computers exchange information, they need to follow certain rules.
Firstly, it should be established how the communication will start. Then, it must be clear whose turn it is to send data packets. Once the packets are sent, both computers need to verify that the message was sent and received correctly. And finally, there needs to be a protocol for ending the conversation.
Why is TCP/IP so Important?
Since TCP/IP are suites of communications protocols, every computer network will depend on them to function without issues.
Of course, different machines could use different protocols, and a local network might be based on a specific protocol suite. However, when it comes to the internet, this approach wouldn’t work well.
Separate computer network protocols would result in nothing more than chaos. Without a common set of rules, the data packets would be exchanged incorrectly and it would be impossible to rely on what’s transferred – and that’s in the best case.
In the worst case, communication would fail instantly.
This is precisely why the TCP/IP model was established as the standard. With a single model, devices worldwide can communicate without issues. It’s also independent of the operating system, so devices can refer to the same set of rules regardless of what OS they run.
The reason TCP/IP works so well is due to the high efficiency of its two main components – TCP and IP. To understand how the protocol suite functions, we’ll need to take a closer look at both protocols.
What is TCP?
You’ve probably figured out what the “P” stands for in TCP: Protocol. The full name of this suite is the Transmission Control Protocol, which should already give you some idea of what the protocol does.
However, saying that the TCP controls transmission doesn’t tell the entire story. Here’s what that actually means.
TCP ensures the data is transmitted continuously and without any hiccups. In particular, this protocol provides reliable data delivery in a stream of bytes. Furthermore, the data is both sent and received in this format.
TCP isn’t active all the time. Instead, the protocol kicks only when programs on either end of the connection need to exchange information. But data flow control isn’t the only function of TCP. The protocol also determines how the data will be broken up.
Example of TCP in Action
Here’s how the Transmission Control Protocol works when exchanging information over a network.
Let’s say you’ve typed a website address into your browser. Once you got to the site, its server sent an HTML file to your computer.
This initial step happens through HTTP, a specialized protocol that communicates with TCP directly. More precisely, HTTP sends out instructions to TCP to activate the connection and send the requested file.
Once TCP gets the instruction, the protocol breaks the file into data packets, marks each packet with a numbers, and starts sending them out. However, TCP doesn’t send the data directly to the recipient. Instead, it forwards the data to another crucial protocol – IP.
The packets then travel through different routes although their source and destination address are the same. Once the data reaches the recipient, TCP on that end takes over the process.
When receiving data, the Transmission Control Protocol will wait until all the packets arrive. Then, the protocol will confirm the transfer and may ask for retransmission.
This example is a good lead-in to the other component of the TCP/IP model – IP.
What Is IP?
IP is the protocol in the background of every network or internet connection. All devices connected to a network have their IP addresses. And because the internet is the most widespread and commonly used network, this protocol has been named the Internet Protocol.
Since IP represents a common language for every device within a network, it performs a crucial function for connectivity and data exchange. While TCP manages data packets and ensures they go out and arrive in a steady stream, the Internet Protocol handles proper addressing and routing.
This means that IP directs the data as it passes through different routers on its way to the recipient.
How the Internet Protocol Works
The Internet Protocol manages where the data is going by assigning IP addresses to devices on a network. In this case, the devices aren’t only computers but, more importantly, the routers.
Along with the data, routers get the destination IP addresses. This allows the devices to forward the packets instantly. Without an IP address, the network wouldn’t know where the data should go.
What Are IP Addresses?
An IP address doesn’t differ much from a home address. But while our addresses contain the street name and house number, each IP address is a string of numbers.
In particular, there are four three-figure numbers, each separated from the other by a period. For example, an IP address might look like this: 126.96.36.199.
If you noticed, we didn’t use all numbers in order in this example, i.e., the address didn’t go 123.456.789.012 or something similar. This is because each of the four numbers in an IP address must be between 000 and 255. Each number actually represents eight bits in the binary code, and the largest expression of those eight bits in this case is 256. Since the count starts from 000 instead of 001, the highest value won’t be 256 but rather 255.
The interesting thing about IP is that the numbers aren’t assigned randomly, even though they might seem random.
In fact, each address that an IP obtains is produced through a mathematical process. Then, the address is allocated by an international body – the Internet Assigned Numbers Authority (IANA).
IP Address Types
A mathematically produced IP address can have a specific purpose. Different addresses are assigned depending on the intended use.
Firstly, the addresses are categorized based on whether they’re assigned to consumers or websites.
Most network devices we use every day have consumer addresses. If you have a plan with an ISP, this is the type of address your device has.
Consumer addresses are further divided into subcategories depending on whether they function within or outside a network:
A public IP address functions outside your network.
A private IP address will only be relevant to your network.
This classification requires a bit more explanation.
When we mention “your network,” we’re referring to independent networks that don’t include the internet. In other words, you could set up a local network that doesn’t have to be online to function. For example, this can be the case with Wi-Fi-controlled smart home devices.
Once you connect to your ISP, your private network gets a public address and a subnet mask. This means that, regardless of how many devices are in your home network, the internet will see all of your traffic as going through a single address. To put it differently, this is how your traffic is identified publicly. It is similar to how you have a phone number assigned to your house that anyone in the family can use.
On the other hand, a private IP address is assigned by your router. Every device hooked on your network receives an address, which allows the router to differentiate the devices.
The subnet mask also tells the router where the public network ends and the host numbers begin so it can start assigning addresses accordingly.
If you have a smart home setup that functions over a home network, every device will have a private address. And if that system is also connected to the internet, it will receive a public address as a whole. This principle is very widespread – for example, you can find it on public Wi-Fi networks.
However, this isn’t the end of the classification.
A public IP address can be dynamic and static. Dynamic addresses will change automatically and regularly. ISPs use automated systems to cycle various available addresses which means your connection won’t have the same IP numbers every time you go online.
Static addresses are the opposite as they stay the same. As long as a device is on the same network, its address won’t change. This type is less often than dynamic addresses and is primarily used by organizations that wish to have their own servers.
Website owners usually don’t have dedicated servers of their own. Instead, they rely on ISPs for hosting and can get either a shared or dedicated address.
Shared addresses are assigned to multiple websites hosted on a single server. This is a common solution for websites that don’t get overly large amounts of traffic or feature too many pages. If the traffic is manageable, there’ll be no issues with server sharing.
Dedicated addresses are, as the name says, dedicated to a single website. This address type is particularly useful for sites with heavy traffic. Having a dedicated address will also make getting an SSL certificate easier and will come with several other benefits, albeit at a higher price.
Example of IP Address Use
An IP address isn’t assigned to a particular device. Instead, the device gets a new address through the internet protocol suite each time it’s connected to a network.
For instance, when you go online on your computer, you’re not getting direct access to the internet. Rather, your device connects to a network that’s hooked to the internet. This will usually be your internet service provider (ISP) or, if you’re at work, the company’s network which also uses an ISP.
The ISP or another intermediary network assigns the IP address to your computer. Through that address, the service provider can direct data to and from your device. Since all of that traffic passes through a router, restarting that device will change the address.
It’s worth mentioning that your IP address will change when you reset the router only if it’s a dynamic IP. Most modern providers have this type of IP. However, if the IP address is static, it will stay the same even after the reset.
Now that we’ve gone over the individual components, it’s time to look at the TCP/IP model as a whole.
What Is the TCP/IP Model?
If you’ve been following so far, you’ve got the basic idea behind TCP and IP. One breaks down data into packets and manages their transport. At the same time, the other assigns addresses and makes sure the packets go through the correct points and reach their destination.
The TCP/IP model works on the client-server principle. The user end of the connection is called the client (i.e., you) while the server part doesn’t need additional explanation. Upon client request, the server will send particular data packets through the network.
However, data transfer in the TCP/IP model isn’t quite as simple as it sounds. The connection doesn’t function as one entity. Instead, there’s a different network layer for every vital function, and the protocol suite needs to address each layer.
TCP/IP Layers Explained
The TCP/IP model divides information into four layers, each with a specific purpose. These are:
Datalink layer or Network access layer
The four layers are there so that network communication can be standardized. With each layer handling a particular task, every computer network can communicate with others seamlessly. Even better, when one aspect of the TCP/IP model needs to be updated, the upgrade can be handled on the relevant layer without hindering the entire protocol.
The Data Link Layer – Network Access Layer
You can think of this TCP/IP component as the physical layer. It’s also commonly referred to as the link layer or network interface layer.
True to its name, the link layer handles the actual physical links that provide network connection to a device. This also explains why it’s called the physical layer. The links may include network device drivers, the network interface card, the Ethernet cable, and the wireless network.
One important segment of the network access layer is the conversion between physical and virtual addresses. While a device gets an IP address assigned to it, it also has a built-in MAC (Media Access Control) address. Low-layer devices like routers and switches use MAC addressing and keep an up-to-date list of MAC addresses and corresponding IP addresses for devices they’re connected to.
The Internet Layer
The internet layer, also known as the network layer, is crucial for data transfer. It controls how data moves across a network, usually the internet – hence the name “internet layer.” You can find routing protocols in this layer.
The Transport Layer
The description of the transport layer will probably sound familiar. It ensures that there’s a reliable data connection and uses it to send information in packages. The transport layer is also responsible for package reception and acknowledgement.
In other words, the transport layer does pretty much the same as the TCP.
The Application Layer
The application layer, unsurprisingly, contains applications that rely on network communication. This is considered among the upper layers as it shows on the surface of the entire system.
Unlike the rest of the four layers, users will be in frequent interaction with the application layer. Whenever you use a messaging or email app, you’re dealing with the application layer. One of the most well-known application protocol is the Simple Mail Transfer Protocol or SMTP, routinely used for email handling.
Of course, the TCP/IP model handles all four layers. However, its main strength is in the transport layer and how the transported data is handled.
The Difference Between TCP and IP
It should be clear by now that TCP and IP aren’t the same. The two protocols create and maintain a data link between different operating systems on a network. They also create channels for delivering packets and the overall flow of internet traffic.
However, there’s a specific place for each protocol in the TCP/IP model.
IP is considered a low-level protocol. It can deliver smaller packets consisting of a routing header, i.e., the intended destination for data, and the payload. This payload can consist of no more than 24 bytes, which is insufficient for a single message. Thus, IP needs to break larger data into many packets before sending them out.
TCP is a protocol of a higher level than IP. Even though the protocol relies on internet protocols, it can do much more than send or each data packet separately.
Rather than with packets, TCP deals with entire data streams. This protocol can interconnect network devices by interacting with individual computers and applications, as well as with web servers and pages.
Is There an Alternative to the TCP/IP Model?
There is another way of organizing network connections and data transfer. It’s called the OSI model. However, you likely won’t encounter it in practical use.
The OSI model was the first network communication standard. It was used in the 1980s and consisted of not four but seven layers:
Data link layer
The OSI system is more complex than the TCP/IP model, which is one of the reasons why TCP/IP replaced it in general use.
Besides the OSI model, the connectionless protocol would be another alternative to the TCP/IP model. This protocol type doesn’t rely on the classic network setup to transfer data.
Which Other Protocols Are in the TCP/IP model?
As mentioned before, the TCP/IP model represent a suite of protocols, and it goes beyond the titular two.
Protocols included in the TCP/IP model are:
Address resolution protocol
Internet control message protocol
Transmission control protocol
User datagram protocol
File transfer protocol
Domain name system
Hypertext transfer protocol
Naturally, the transmission control and internet protocols play major roles in the entire system. But that doesn’t mean other components of the TCP/IP model are irrelevant. Each protocol defines certain network boundaries as well as network paths for different types of information.
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Frequently Asked Questions
Below are the most frequently asked questions.
What is the difference between TCP and IP?
Although both protocols serve a similar purpose, they have plenty of differences. For instance, IP handles smaller packets while TCP uses data streams. IP is a low-level and TCP a high-level protocol.
What is TCP and IP Port?
Similar to how a device is identified via an IP address, individual services or applications running on that device are identified by a TCP port. Together with an IP address, a TCP/IP port forms a socket – a unique signature of your device.
What does TCP/IP stand for?
TCP is short for transmission control protocol, while IP stands for internet protocol. These protocols handle all data communication on a network.
Author: Tibor Moes
Founder & Chief Editor at SoftwareLab