2. TCP/IP Layered protocol
• The TCP/IP protocol suite predates the OSI Reference Model by
about a decade.
• Despite this, the TCP/IP protocol suite can (very generally) be
mapped to the model.
• TCP/IP has fewer layers than the seven layers used in the OSI
RM.
• Most descriptions of TCP/IP define four functional levels in the
protocol architecture.
3. • In the OSI RM, data is passed down the stack when it is
being sent to the net, and up the stack when it is being
received from the network.
• Each layer in the stack adds control information (header)
to ensure proper delivery.
• Each layer treats all of the information it receives from
the layer above as data and encapsulated with its own
header.
• When data is received, the opposite happens. Each layer
strips off its header before passing the data on to the layer
above.
4.
5.
6. TCP/IP’s application layer
The TCP/IP model does not have session or presentation layers. No
need for them was perceived. Instead, applications simply include any
session and presentation functions that they require. Experience with
the OSI model has proven this view correct: these layers are of little
use to most applications.
On top of the transport layer is the application layer. It contains all the
high-er-level protocols. The early ones included virtual terminal
(TELNET), file transfer (FTP), and electronic mail (SMTP). Many
other protocols have been added to these over the years.
7.
8. Transport layer
• The TCP/IP Transport layer protocols ensure that packets
arrive in sequence and without error, by exchanging
acknowledgments of data reception, and re-transmitting lost
packets.
This type of communication is known as "end-to-end" or "host-
to-host".
Two types of transport protocols at this level:
• TCP ( Transport Control Protocol )
• UDP ( User Datagram Protocol )
9. TCP protocol
• TCP enables applications to communicate with each other
although connected by a physical circuit.
• TCP sends data in a form that appears to be transmitted in a
character-by-character fashion, rather than as discreet packets.
• This transmission consists of starting point, which opens the
connection.
• It consists of an ending point, which closes the connection.
• TCP attaches a header onto the transmitted data.
10. • This header contains a large number of parameters that help
processes on the sending machine connect to peer processes
on the receiving machine.
• TCP confirms that a packet has reached its destination by
establishing an end-to-end connection between sending and
receiving hosts.
• TCP is therefore considered a "reliable, connection-oriented"
protocol
11. UDP protocol
• UDP, the other Transport layer protocol, provides datagram
delivery service.
• UDP is an unreliable, (no ACK), connectionless datagram
protocol.
• It does not provide any means of verifying that connection was
ever achieved between receiving and sending hosts.
• As UDP eliminates the processes of establishing and verifying
connections, applications that send small amounts of data use it
rather than TCP.
• Applications that fit a "query-response" model are also excellent
candidates for using UDP.
• Simplex broadcast messages uses UDP.
12. Network Layer
• Also known as the Internet Layer.
• Accepts and delivers packets for the network.
• It includes the powerful
Internet protocol (IP),
the ARP protocol, and
the ICMP protocol.
13. The internet layer is the linchpin that holds the whole
architecture together. Its job is to permit hosts to inject
packets into any network and have them travel in-
dependently to the destination (potentially on a different
network).
The internet layer defines an official packet format and
protocol called IP (Internet Protocol), plus a companion
protocol called ICMP (Internet Control Message Protocol)
that helps it function. The job of the internet layer is to
deliver IP packets where they are supposed to go. Packet
routing is clearly a major issue here, as is congestion
(though IP has not proven effective at avoiding
congestion).
Internet Layer
14. IP protocol
IP protocol and its associated routing protocols are possibly the
most significant of the entire TCP/IP suite.
IP is responsible for:
• IP addressing: The IP addressing conventions are part of
the IP protocol.
• Host-to-host communication: IP determines the path a
packet must take, based on the receiving host's IP address.
• Packet formatting: IP assembles packets into units known
as IP datagrams.
• Fragmentation: If a packet is too large for transmission
over the network media, IP on the sending hosts breaks the
packet into smaller fragments. IP on the receiving host
reconstructs the fragments into the original packet.
15. ARP Protocol
The Address Resolution Protocol (ARP) assists IP in
directing datagrams to the appropriate receiving host by
mapping the IP address (32 bits long) to unique physical
Ethernet address (48 bits long).
The sending computer will of course know its source
MAC address but how does it know the destination
MAC address? That’s where ARP comes into play
16. Example:
In the picture above we have two computers, H1 and H2 and you can see
their IP addresses and their MAC addresses. Our IP packet will have a
source IP address of 192.168.1.1 and a destination IP address of 192.168.1.2.
Next step will be to put our IP packet in an Ethernet frame where we set
our source MAC address AAA and destination MAC address BBB.
how does H1 know about the MAC address of H2?
We know the IP address because we typed it but there is no way for H1 to
know the MAC address of H2. There is another protocol we have that will
solve this problem for us, it’s called ARP (Address Resolution Protocol). Let
me show you how it works:
17.
18. ICMP Protocol
• Internet Control Message Protocol (ICMP) is the protocol
responsible for detecting network error conditions and
reporting on them.
• ICMP reports on:
Flow control: When datagrams arrive too fast for
processing, the receiver sends message to the sender to
stop sending.
Connectivity failure: When a destination host can't be
reached.
Redirection: Which tells a sending host to use another
router.
Checking remote hosts: ping server ===> server is
alive.
19. Network Access Layer ( Data Link Layer)
• All these requirements led to the choice of a packet-switching
network based on a connectionless layer that runs across different
networks. The lowest layer in the model, the link layer describes
what links such as serial lines and classic Ethernet must do to meet
the needs of this connectionless internet layer.
• It provides error control and framing of the datagram.
• It ensures the reliable delivery of data across the underlying
physical network.
• It encompasses the function of the physical layer by specifying the
characteristics of the hardware to be used for the network.
• In this layer TCP/IP describes hardware standards such as
IEEE802.3, the specification for Ethernet network media, and RS-
232, the specification for standard pin connector for PPP
communication link.
