I'd like to welcome you to the next installment of the network security lecture series this lecture
will be devoted to protocol and networking hardware.
We will learn about the risks related to each of the OS and model layers.
To fully appreciate these risks we will now revise the design of VLSI model more than 30 years ago.
Engineers who are creating protocols that are still in use today encountered a serious issue.
They had to find a universal way of communication between any two hosts.
These may be both modern supercomputers and modern mobile devices.
There is a huge gap here when it comes to computational power.
Also the people who designed and created it never met.
There have to be some general standards and principles successful communication between such devices
poses a challenge.
Engineers tackled the issue by dividing it into smaller problems.
One big task finding a universal way of communication between any two hosts in the Internet was split
into some smaller tasks.
Seven to be precise each of these tasks is fulfilled by a different layer of the OS model.
We have to know something more than only what's done in each of the layers.
The model itself is slightly outdated.
It's getting harder and harder to say precisely which function is located and which layer.
Very often the schematic representation of the model shows only three layers for simplicity
for us it's most important to remember that higher layers are dependent upon lower layers.
If there's a problem in the physical error or in the data link player you won't find the solution in
the presentational layer or the network layer individual layers are strongly interconnected.
The second important point is that there is a mutual trust between individual layers of the ISI model
for example Protocols of the fourth layer.
Don't check up on the data provided by the third layer protocols protocols don't verify incoming data.
The next piece of information worth remembering is that each layer communicates only with its immediate
neighbors.
That's all when it comes to the most important points of the US my architecture.
Let's have a closer look at each layer.
We'll start from the bottom.
The physical layer sends a signal through a physical medium.
It may be a copper or optical fiber cable or a radio wave next there is a datalink layer.
It controls access to the medium.
It has to take into account various features of the medium.
For example one copper cable cannot transmit two signals of the same frequency lots of these layers
like any kind of security measures.
Even the simplest ones
layer three is the network layer that's responsible for the IP addressing and routing.
This involves sending packets between networks and transferring them to the destination host.
The transport layer is the fourth one that's responsible for communication channels Layer 4 allows you
to establish a two way connection.
It also enables you to control the session in contrary to layers one and two you can implement some
security measures in layers three and four internet protocols are used for that purpose.
Then there is the session layer this layer may compromise reliable protocols which are connected with
managing assertion.
These are however usually implemented in lower layers a closer look at this layer will show that it
includes protocols such as and TLM or Kerberos which will be discussed in another lecture
the six layer of the model is the presentation layer one of its tasks is data encoding it's responsible
for the delivery and formatting of information to the communication protocols.
So they're prepared to be sent the application layer is the last layer of the model.
In this module We'll see why a successful attack on one of the layers can give the attacker control
over the entire computer system.
This is another reason for implementing layered security.
We will also consider risks and threats connected with each individual or us-I layer.
We will also examine what kind of measures provide real protection against those threats and in which
circumstances such protection is only illusory as a summary of all this information.
We will try to answer the question how can you effectively improve the security of your computer networks.
Let's start module 6.