1. TCP/IP Model
TCP/IP is an abbreviation used for transmission control
protocol/Internet Protocol.
It was developed by Defence Advance Research Projects
Agency (ARPA, later DARPA) in late 1970's.
The layers in the TCP/IP protocol suite
do not exactly match those in the OSI
model.

2. TCP/IP and OSI Model

3. TCP/IP Protocol Suite
• Host-to-network : Physical and data link layer
– No specific protocol
• Network layer
– IP(Internet Protocl), ARP(Address Resolution Protocol),
RARP(Reverse ARP), ICMP(Internet Control Message Protocol),
IGMO(Internet Group Message Protocol)
• Transport layer
– TCP(Transmission Control Protocol), UDP(User Datagram Protocl),
SCTP(Stream Control Transmission Protocol),
• Application Layer
– Combined session, presentation, and application layers

4. (a) FTP (File Transfer Protocol)
FTP is used for file transfer between inter network nodes.
b) SMTP (Simple Mail transfer Protocol)
It is used for exchanging e-mail.
c)Telnet
Telnet provides connectivity between dissimilar operating systems. Telnet is a
general purpose client-server application program.
d) DNS (Domain Name Systems)
The DNS is used to convert the domain name into the IP addresses. People
prefer to use name instead of addresses. Therefore DNS maps a name to an
address and conversely.
(e) HTTP (Hypertext Transfer Protocol)
HTTP is an internet protocol designed for a specific application, the World Wide
Web (WWW).

5. Addressing
• Four levels of addresses in TCP/IP protocols
• Physical (link), logical (IP, network), port, and specific addresses

6. Relationship of Layers and
Addresses

7. Physical Address : (Link Address)
•Address of node as defined by the network.
•Size and format of these addresses vary depending
on the network. E.g Ethernet (48 bits)
•Each system having a NIC(Network Interface Card)
through which two systems physically connected with
each other with cables.
• The address of the NIC is called Physical address or
mac address.
• This is specified by the manficture company of the
card.

8. Logical Address : necessary for universal communications,
independent of underlying physical network.
(IP address of the system)
Combination of Net ID and Host ID.
This address can be changed by changing the host position on
the network.

9. Port Address:
There are many application running on the computer. Each
application run with a port no.(logically) on the computer.
The physical addresses will change from hop to hop, but
the logical addresses and port addresses usually remain the
same
In computer networking, a port is an application- specific
or process-specific software construct serving as
a communications endpoint.
The well-known ports are defined by convention
overseen by the Internet Assigned Numbers
Authority (IANA)

10. Examples of well known ports include:
21: File Transfer Protocol (FTP)
22: Secure Shell (SSH)
23: Telnet remote login service
25: Simple Mail Transfer Protocol (SMTP)
53: Domain Name System service
80: Hypertext Transfer Protocol (HTTP) used in the World
Wide Web
119: Network News Transfer Protocol (NNTP)
161: Simple Network Management Protocol (SNMP)

11. Specific Address
• Some application have user-friendly addresses that are designed for
that specific address
• Example 1: e-mail address: kchung@kw.ac.kr
– Defines the recipient of an e-mail
• Example 2: URL (Universal Resource Locator) : www.kbs.co.kr
– Used to find a document on the WWW

12. Summary
1.The OSI model originally distinguishes between service,interface and
protocols.
1.The TCP/IP model doesnt clearly distinguish between service,interface and
protocol.
2.The OSI model is a reference model.
2.The TCP/IP model is an implementation of the OSI model.
3.In OSI model,the protocols came after the model was described.
3.In TCP/TP model, the protocols came first and the model was really just a
description of the
existing protocols.
4.In OSI model,the protocols are better hidden.
4.In TCP/IP model ,the protocols are not hidden.
5.The OSI model has 7 layers.
5.The TCP/IP model has only 4 layers.
6.The OSI model supports both connectionless and connection-oriented
communication in the
network layer,but only connection -oriented communication in transport layer.
6.The TCP/IP model supports both connectionless and connection-oriented
communication in the transport layer,giving users the choice.