Introduction
It may be useful to have a conceptual grasp of how protocols come together in order to comprehend how networks operate. In the field of communications protocols, there is a single conceptual model.
An alternative term for these services is “model,” however the term refers more to an actual architectural design. Both the OSI model and the TCP/IP architecture will be discussed in this blog.
You’ll be required to know how networks function. Systems may be rationally organized using topologies to show how they are interconnected.
With this, we can begin discussing the physical components of networks and the methods by which they are addressed. We want our networking systems to be able to talk to each other at the end of the day.
This can only be accomplished if each system is designed to allow others to address it. There are several IP addresses for each machine, as you can see. Using distinct addresses is a means to communicate with different functions at different tiers, which is a reference to the older concepts.
We’ll start talking about the protocols you’re probably most acquainted with as we work our way up the network stack from the physical components: Internet Protocol (IP), Transmission Control Protocol (TCP), and User Datagram Protocol (UDP). These are the protocols you’ll need to know in order to test systems and advise firms on how to fix vulnerabilities.
The employment of service providers is a typical strategy to delivering IT services in firms, particularly if the services are being provided to external clients or users.
It is possible to execute this form of outsourcing using cloud computing. People who do security assessments or penetration testing have unique hurdles when dealing with enterprises that have put systems and services with these service providers.
So knowing how these third-party service providers operate might be crucial.
Communications Models
Through their IP addresses, computers may be accessed. Because each machine will have different IP addresses, this is a major drawback.
It is important to categorize these addresses into buckets based on the protocols they belong to. First and foremost, the first communications model is conceptual rather than absolutely practical.
Communication models are divided into tiers and then piled on top of one another to get this effect.
Often referred to as network stacks or protocol stacks, this is because of the way it appears as a series of layers One thing to keep in mind about these network stacks is that each of the levels and functions is unique from the others.
Two systems can only communicate with one another via these hypothetical levels C on the first system can only speak to C on the second system, not layers B, A, or D. This is due to the fact that both systems’ layer C protocols are identical. As with the other procedures, this is also the case
Protocols
In the context of communication, a protocol is a collection of rules or standards. Nodding or saying hello is common when you see a friend or acquaintance on the street.
There is a good chance they will reciprocate. This is a set of rules. Both you and the other party to the conversation are aware of the appropriate course of action.
Computers, like humans, have a set of rules and anticipated behaviors that they follow. You could welcome your acquaintance by poking your little finger into your ear and the other person may remove a shoe and chuck it at you if you didn’t follow these rules.
None of you would know what the right reaction would be if there was a protocol mismatch, since neither of us would know what the first communication attempt meant.
While going through the two communication models and you’ll be able to see how protocols interact between systems and how messages are put together across systems/applications in two distinct methods.
Layer-by-layer decomposition of network communication functions results in a modularization of such functions. As a result, adding a new protocol to an existing chain is simple.
For example, SONET and Frame Relay programs perform just as well over Ethernet as they do over SONET or Frame Relay. Every one of these protocols may be found at the same level of the OSI model.
One layer’s functionalities are abstracted, which means that layers may interact with each other without having to know the specifics.
It doesn’t really matter what the specific procedures are. No matter the model we’re discussing, there are a plethora of distinct protocols for each of the levels.
Open Systems Interconnection (OSI)
In the context of communication, a protocol is a collection of rules or standards. Nodding or saying hello is common when you see a friend or acquaintance on the street.
There is a good chance they will reciprocate. This is a set of rules. Both you and the other party to the conversation are aware of the appropriate course of action.
Computers, like humans, have a set of rules and anticipated behaviors that they follow. You could welcome your acquaintance by poking your little finger into your ear and the other person may remove a shoe and chuck it at you if you didn’t follow these rules.
None of you would know what the right reaction would be if there was a protocol mismatch, since neither of us would know what the first communication attempt meant.
While going through the two communication models, I’ll discuss both the functions and protocols that are present at each level.
Layer-by-layer decomposition of network communication functions results in a modularization of such functions. As a result, adding a new protocol to an existing chain is simple.
For example, SONET and Frame Relay programs perform just as well over Ethernet as they do over SONET or Frame Relay.
Every one of these protocols may be found at the same level of the OSI model. One layer’s functionalities are abstracted, which means that layers may interact with each other without having to know the specifics.
It doesn’t really matter what the specific procedures are. No matter the model we’re discussing, there are a plethora of distinct protocols for each of the levels.
Application Layer (Layer 7)
In terms of proximity to the end user, the Application layer takes the cake. This does not imply, however, that it is the app itself.
Protocols are what we’re discussing. The application layer protocols are responsible for handling the application’s communication requirements.
They may be able to locate resources and regulate their interactions with them. For instance, the HyperText Transfer Protocol (HTTP) falls within this category.
It handles all of the back-and-forth between the client and the server when it comes to negotiating for resources.
Presentation Layer (Layer 6)
Data is prepared for the Application layer by the Presentation layer. You may be certain that anything you provide to the app will be processed correctly because of this.
There may be formatting discrepancies when systems communicate, and the Presentation layer ensures that data is presented appropriately on both ends.
As a result, character encoding systems like ASCII, Unicode, and EBCDIC all belong under the Presentation layer.
ASCII stands for the American Standard Code for Information Interchange. In addition, the JPEG format is regarded to be at the presentation layer, as well.
Session Layer (Layer 5)
Maintaining application communication is the responsibility of the Session layer, which handles the communication between the endpoints (the client or server).
An example of a function at the Session layer is the RPC (remote procedure call). Because of the necessity to negotiate communication between the endpoints, file sharing has components that also exist at the Session layer.
It’s the job of the Application layer to keep track of resources, while the Session layer is in charge of things like ensuring sure files are sent correctly.
Transport Layer (Layer 4)
The Transport Layer is responsible for providing a reliable and efficient service to the upper layers of the OSI model.
It does this by segmenting the data into manageable packets, ensuring that packets are delivered in the correct order, and error-checking the data.
Communications are additionally multiplexed by the Transport layer, which is responsible for this. There are two types of transport protocols: TCP and UDP. Rather of using IP addresses, these protocols make extensive use of ports.
Network Layer (Layer 3)
The network layer is responsible for routing packets between hosts on the network. It determines the best path for a packet to travel to its destination and forwards it along that path.
The network layer also performs congestion control and manages network resources.
Data Link Layer (Layer 2)
The media access control (MAC) address is an additional consideration. Layer 2 addresses are used to identify network interfaces so that communications may flow from one system to another on the local network.
ARP, VLANs, Ethernet, and Frame Relay are all Data Link layer technologies. They are in charge of preparing the data for transmission by formatting it.
Physical Layer (Layer 1)
The physical layer of the OSI model is responsible for the physical transmission of data across a network.
This includes the encoding and decoding of data, as well as the transmission of signals across a network. The physical layer also includes the management of network media and devices and the configuration of network parameters.
The protocols used in the physical layer of the OSI model are Ethernet, Token Ring, and FDDI.
Issues with OSI model
One of the flaws of the OSI model is that mapping protocols to the seven levels is not always straightforward. Between the Session and Application levels, several issues arise.
How does the Secure Shell (SSH) protocol fit into this? Is it the Presentation layer because it incorporates encryption techniques and negotiates them, or is it the Session layer because it controls sessions?
Between the levels, more protocols seem to exist. Because it serves as a link between the addressing schemes used at the Data Link and Network levels, ARP, for example, may be considered to function at the Data Link layer.
However, there are certain situations when having a model makes it lot simpler to understand what you’re looking at.
Your house undoubtedly has an appliance that’s a little difficult to understand. Depending on who you ask, you may refer to it as a router, or you may know someone who does.
Unfortunately, as previously said, routing is a layer 3 function, although the device also has layer 2 features, such as switch ports, that are only responsible for transmitting data on your local network.
It’s conceivable that your device is just bridging to the network of your service provider and not doing any routing at all. It all relies on how well your equipment is performing and what your service provider expects from it.
Having a better knowledge of the various levels may assist here. Because you can separate functionality, you can better pinpoint where you may be having issues.
TCP/IP Architecture
The ARPAnet was initially conceived and deployed in the late 1960s. There were two and then three nodes linked in 1968–69, but the network developed significantly during the following several years.
The personnel in charge of maintaining the network and establishing the protocols for exchanging information learnt a great deal as additional systems were added to the network.
As a gateway for messages, the Interface Message Processor (IMP) served as a massive computer with specific interfaces known as the 1822 protocol (think of it as a very primitive router).
The Network Control Program (NCP) superseded the 1822 protocol (NCP).
Following years of development, the National Communication Protocol (NCP) was completely superseded by a set of protocols known as TCP/Internet Protocol (TCP) (IP).
The OSI model is defined in a slightly different approach when it comes to TCP/IP. Protocol design was outlined after TCP/IP was put into use.
Rather than describing an idea, the suite is described as a description of an as-built design, hence it is often called a model or an architecture.
As a result, the TCP/IP model has a considerably simpler design than the OSI model, which is immediately noticeable and reflects the actual design as contrasted to the OSI’s conceptual design.
For this reason, the OSI model was divided down into the seven functional categories stated previously in order to handle a broad range of protocols and architectures. TCP/IP, on the other hand, has only four levels in its as-built specification.
Summary
Systems may be rationally organized using topologies to show how they are interconnected.
Layer-by-layer decomposition of network communication functions results in a modularization of such functions. Adding a new protocol to an existing chain is simple.
For example, SONET and Frame Relay programs perform just as well over Ethernet as they do over SONet or framerelay. There are a plethora of distinct protocols for each of the levels.
Mapping protocols to the OSI model is not always straightforward. ARP may be considered to function at the Data Link layer. How does the Secure Shell (SSH) protocol fit into this?
More protocols seem to exist between the Application and Presentation levels.
The ARPAnet was initially conceived and deployed in the late 1960s. The National Communication Protocol (NCP) was completely superseded by TCP/Internet Protocol (TCP) (IP) The OSI model is defined in a slightly different approach when it comes to TCP/IP.
The ARPAnet was initially conceived and deployed in the late 1960s. The National Communication Protocol (NCP) was completely superseded by TCP/Internet Protocol (TCP) (IP) The OSI model is defined in a slightly different approach when it comes to TCP/IP.
Review Questions
- which osi layer checks frames for errors?
- The Data Link layer checks frames for errors.
- which osi layer does dhcp belong to?
- DHCP is a protocol that resides in the network layer of the OSI model.
- at what layer of the osi model does the ipsec encryption protocol operate?
- The IPsec encryption protocol operates at the Network layer of the OSI model.
- at which osi layer does a router operate
- A router operates at the Network layer of the OSI model.
- at what layer of the osi model do the 802.11 standards vary?
- The 802.11 standards vary at the data-link layer.
- what is the purpose of the osi physical layer?
- The Open Systems Interconnection (OSI) physical layer provides the means to transfer bits between devices. The physical layer is responsible for encoding and decoding the data and ensuring that it is transmitted correctly.
- what are two services performed by the data link layer of the osi model?
- The data link layer provides services that enable two devices on the same network to communicate. These services include media access control (MAC) addressing and error detection.
- in the tcp/ip model, what layer is considered so simple that it is ignored entirely?
- The application layer.
- which layer in the tcp/ip model is used for formatting, compressing, and encrypting data?
- The application layer in the TCP/IP model is used for formatting, compressing, and encrypting data.
- which vpn protocol works at layer 3 and can encrypt the entire tcp/ip packet?
- Layer 3 VPNs use IPsec, which can encrypt the entire TCP/IP packet.
