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OSI - Protocols Transcription

Welcome to our OSI Model Encapsulation and Protocols Module. The purpose of the seven layer OSI or open systems interconnection model was to increase interoperability between vendor products. In order to accomplish this, industry standard interfaces, and APIs, or application program interfaces, are used. The model was designed to clarify network services, functionality, and communications processes, by defining a series of layers without looking at very specific detail.

Since it uses a modular approach, components can be modified without affecting other components. Here, we have the OSI seven layer model. Data begins at the application layer, or the seventh layer, and moves down to the first layer, or the physical layer, where it can be moved to other computers either over a wire or through some wireless communication method.

As the data moves down the layers, each layer adds additional data as necessary to get the data where it needs to go and in the format that it needs to get there. You can remember the seven layers of the OSI model with the mnemonic, please do not throw sausage pizza away from layer one all the way up through layer seven, or the reverse, all people seem to need data processing.

These are both helpful ways to help you remember the different layers of the OSI model. Protocols are communication rules that allow two more more computers to send and receive data between each other. Protocols are a set of formatting and rules that allow standardization of the exchange of information so that different systems can communicate with each other.

They also allow different operating systems and applications to communicate. Before we had standard protocols, Apple computers could not talk to Microsoft computers for example. Different protocols have different functions and goals, and different network models can allow different services to be carried out by various protocols at different layers of the OSI model.

TCP and IP, transmission control protocol and Internet protocol, are both examples of commonly used protocols. Here we can see some protocols that occur at the different layers of the OSI model. You can see that there are some highlighted protocols, which are more popular and may be worth remembering for the CISSP examination.

At the application layer, or layer seven of the OSI model, we have APIs, or application performance interfaces, which allow applications to communicate with other applications in a recognizable format. At the transport layer we have TCP, transmission control protocol, and UDP, user datagram protocol. At the network layer, we have IP or Internet protocol version 4 and version 6.

OSPF, open shortest path first. And BGP, border gateway protocol. Routers operate at the third layer, or network layer, of the OSI model. And you should also remember that for the CISSP examination. The data link layer has the Ethernet protocol, and this is also where switches operate. Switches are generally layer two devices, although there are some advanced switches that can operate at layer two and layer three of OSI model.

But for the CISSP examination, you should remember that switches operate typically at the data link layer, or layer two. Layer one, or the physical layer, is where we typically have our media, whether that is a piece of cabling or wireless or some other type of communication technology. This is also where we have patch panels, where our cabling in our building comes together in a single interface.

Hubs, and repeaters, also operate at the physical layer, or layer one of the OSI model. And at the bottom, we can see our mnemonic again, please do not throw sausage pizza away. Here we can see how all of the layers work together to allow communications between different systems.

Here we start off with a message that we wanna send to another system, and this occurs at the application layer. The message moves down to the presentation layer where it is formatted and encoded, and then moves down to the session layer where session maintenance occurs, establishing a session between the two sessions.

We then move to the transport layer where we have a virtual connection established and flow control to make sure that the packets get there correctly in the correct order and that there are no errors. And we use TCP to accomplish this goal. At the network layer, we use an IP address, or Internet protocol address, to actually deliver this packet to the intended recipient.

We then move down to the data link layer where we use a MAC address, or media access control address, which is an address that is coded into our network interface cards when they are created. The data then moves down the the physical layer, where it moves from computer to computer using switches, routers and repeaters.

Once the data arrives at the recipients computer, we start off at the physical layer and then move up through the layers until we get back to the application layer where the message is delivered to the recipient. It is important for all of the layers to work together in order for our applications to work correctly, in this case to deliver the message to the intended recipient.

This concludes our OSI model module. Thank you for watching.