TCP/IP PROTOCOL SUITE |What is the TCP/IP Model? Layers and Protocols Explained ?
TCP/IP PROTOCOL SUITE :
TCP/IP =Transmission Control Protocol/Internet Protocol.
It is a hierarchical protocol made up of interactive modules .
each of which provides a specific functionality.
What is The term hierarchical : means that each upper level protocol is supported by the services provided by one or more lower level protocols.
The original TCP/IP protocol suite was defined as four software layers built upon the hardware.
Today, however, TCP/IP is thought of as a five-layer model.
What is TCP/IP ?
is a protocol suite (a set of protocols organized in different layers) used in the Internet today.It is a hierarchical protocol made up of interactive modules .
each of which provides a specific functionality.
What is The term hierarchical : means that each upper level protocol is supported by the services provided by one or more lower level protocols.
The original TCP/IP protocol suite was defined as four software layers built upon the hardware.
Today, however, TCP/IP is thought of as a five-layer model.
What is Layered Architecture ?
Layered Architecture :
To show how the layers in the TCP/IP protocol suite are involved in communication between two hosts, we assume that we want to use the suite in a small internet made up of three LANs (links) .
each with a link-layer switch.
We also assume that the links are connected by one router .
Communication through an internet :
Let us assume that computer A communicates with computer B. As the figure shows, we have five communicating devices in this communication: source host (computer A)
the link-layer switch in link 1
the router
the link-layer switch in link 2,
and the destination host (computer B).
Each device is involved with a set of layers depending on the role of the device in the internet. The two hosts are involved in all five layers .
the source host needs to create a message in the application layer and send it down the layers so that it is physically sent to the destination host.
The destination host needs to receive the communication at the physical layer and then deliver it through the other layers to the application layer . The router is involved in only three layers ,
there is no transport or application layer .
in a router as long as the router is used only for routing.
Although a router is always involved in one network layer, it is involved in n combinations of link and physical layers in which n is the number of links the router is connected to.
The reason is that each link may use its own data-link or physical protocol.
For example, in the above figure :
the router is involved in three links, but the message sent from source A to destination B is involved in two links.
Each link may be using different link-layer and physical-layer protocols .
the router needs to receive a packet from link 1 based on one pair of protocols and deliver it to link 2 based on another pair of protocols.
A link-layer switch in a link, however, is involved only in two layers, data-link and physical.
Although each switch in the above figure has two different connections, the connections are in the same link, which uses only one set of protocols.
This means that, unlike a router, a link-layer switch is involved only in one data-link and one physical layer.
Layers in the TCP/IP Protocol Suite :
Read also :
Principles of Protocol Layering
What is Direct Connection to the Internet ?
? What is the TCP/IP Model? Layers and Protocols Explained
? What is the TCP/IP Model?
is a protocol suite (a set of protocols organized in different layers) used in the Internet today.
It is a hierarchical protocol made up of interactive modules .
each of which provides a specific functionality.
: application, transport, and network layers
is end-to-end.
However, the duty of the data-link and physical layers is hop-to-hop, in which a hop is a host or router.
In the top three layers, the data unit (packets) should not be changed by any router or link-layer switch.
In the bottom two layers, the packet created
by the host is changed only by the routers, not by the link-layer switches.
What are the functions of the five layers of the TCP/IP model?five Layers Explained
We show the identical objects below each layer related to each device
Description of Each Layer
? What are the 5 layers of TCP IP
? What is the main function of physical layer
1__Physical Layer
? What is the physical layer
We can say that the physical layer is responsible for carrying individual bits in a frame across the link. physical layer is the lowest level in the TCP/IP protocol suite .
? What is a physical layer protocol?
TCP/IP does not define any specific protocol for the physical layer.
It supports all of the standard and proprietary protocols.
At this level, the communication is between two hops or nodes, either a computer or router.
The unit of communication is a single bit.
When the connection is established between the two nodes :
a stream of bits is flowing between them.
The physical layer, however, treats each bit individually.
?What is the physical layer function
?What is the function of physical layer
the major functions of the physical layer is to move data in the form of electromagnetic signals across a transmission medium.
The responsibility of the physical layer, in addition to delivery of bits, matches with what mentioned for the physical layer of the OSI model,
but it mostly depends on the underlying technologies that provide links.
physical layer is responsible for carrying individual bits in a frame across the link.
the communication is between two hops or nodes .
What is the function of physical layer
When a node is connected to n links:
it needs n physical-layer protocols .
one for each link : why??
The reason is that different links may use different physical-layer protocols.
Note :
The unit of communication at the physical layer is a bit.
Data Link Layer :
What is data link layer protocol?
TCP/IP does not define any specific protocol for the data link layer either.
It supports all of the standard and proprietary protocols.
At this level, the communication is also
between two hops or nodes.
The unit of communication however, is a packet called a frame.
What is A frame :
is a packet that encapsulates the data received from the network layer with an added header and sometimes a trailer.
The head, among other communication
information, includes the source and destination of frame.
What is The destination address is
needed to define the right recipient of the frame because many nodes may have been connected to the link.
What is The source address :
is needed for possible response or acknowledgment as may be required bysome protocols.
What is the function of the data link layer?
The routers are responsible for choosing the best links.
However, when the next link to travel is determined by the router, the data-link layer is responsible for taking the datagram and moving it across the link.
In each case, the data-link layer is responsible for moving the packet through the link.
Each link-layer protocol may provide a different service.
What are the duties of data link layer?
Some link-layer protocols provide
complete error detection
and correction,
some provide only error correction.
What is The link :
can be a wired LAN with a link-layer switch, a wireless LAN, a wired WAN, or a wireless WAN.
Network Layer :
What is the main function of the network layer?
What is the function of the Network layer?
The network layer is responsible for creating a connection between the source computer
and the destination computer.
The communication at the network layer is
host-to host.
However, since there can be several routers from the source to the destination, the routers
in the path are responsible for choosing the best route for each packet.
We can say that the network layer is responsible for host-to-host communication
and routing the packet hrough possible routes .
Why do we use Network Layer ?
Again, we may ask ourselves why we need the network layer. We could have added the routing duty to the transport layer and dropped this layer.
One reason, as we said before, is the separation of different tasks between different layers. The second
reason is that the routers do not need the application and transport layers.
Separating the tasks allows us to use fewer protocols on the routers.
What protocols are used in Network Layer?
The network layer in the Internet includes the main protocol
What is IP in Network layer?
1__Internet Protocol (IP) :
that defines the format of the packet, called a datagram at the network layer.
What is the main function of the Internet protocol (IP)?
IP defines the format and the structure of addresses used in this layer.
IP is also responsible for routing a packet from its source to its destination,
which is achieved by each router forwarding the datagram to the next router in its path.
IP is a connectionless protocol that provides no flow control, no error control, and no congestion control services.
This means that if any of theses services is required for an application, the application should rely only on the transport-layer protocol.
The network layer also includes unicast (one-to-one) and multicast (one-to-many) routing protocols.
A routing protocol does not take part in routing (it is the responsibility of IP),
but it creates forwarding tables for routers to help them in the routing process.
The network layer also has some auxiliary protocols that help IP in its delivery and routing tasks.
2__The Internet Control Message Protocol (ICMP) : helps IP to report some problems when routing a packet.
What is The Internet Group Management Protocol (IGMP) ?
is another protocol that helps IP in multitasking.
3__The Dynamic Host Configuration Protocol (DHCP): helps IP to get the network-layer address for a host.
4__The Address Resolution Protocol (ARP):
is a protocol that helps IP to find the link-layer address of a host or a router when its network-layer address is given.
NOTE :
The unit of communication at the network layer is a datagram.
What is difference between the segment and the datagrams ?
what is segment ?
A segment may consist of a few or tens of datagrams.
The segments need to be broken into datagrams and each datagram has to be delivered to the network layer for transmission.
Since the Internet defines a different route for each datagram .
the datagrams may arrive out of order and may be lost.
The transport layer at computer B needs to wait until all of these datagrams to arrive, assemble Again .
we should know that the two transport layers only think that they are communicating with each other using a segment; the communication is done through the physical layer and the exchange of bits
Application Layer
What is the function of the Network layer?
The application layer allows a user to access the services of our private internet or the global Internet. Many protocols are defined at this layer to provide services such as electronic mail
file transfer
accessing the World Wide Web, and so on.
The application layer in TCP/IP is equivalent to the combined session, presentation, and
application layers in the OSI model.
Note :
the communication at the application layer, like the one at the transport layer, is end to end.
A message generated at computer A is sent to
computer B without being changed during the transmission.
The unit of communication at the application layer is a messag .
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