Download Port Address

Lecture # 07
Computer Communication and
Networks
Muhammad Waseem Iqbal
McGraw-Hill
©The McGraw-Hill Companies, Inc., 2000
TCP/IP PROTOCOL SUITE
The layers in the TCP/IP protocol suite do not exactly
match those in the OSI model. The original TCP/IP
protocol suite was defined as having four layers: host-tonetwork, internet, transport, and application. However,
when TCP/IP is compared to OSI, we can say that the
TCP/IP protocol suite is made of five layers: physical,
data link, network, transport, and application.
Topics discussed in this section:
Physical and Data Link Layers
Network Layer
Transport Layer
Application Layer
Figure-1 TCP/IP and OSI model
ADDRESSING
Four levels of addresses are used in an internet employing
the TCP/IP protocols: physical, logical, port, and specific.
Topics discussed in this section:
Physical Addresses
Logical Addresses
Port Addresses
Specific Addresses
Figure -2 Addresses in TCP/IP
Physical address:
•
When referring to computers in general or computer
memory, the physical address is the computer memory
address of a physical hardware device.
•
When referring to a network address, physical
address is sometimes used to describe the MAC address.
•
This is specified by the manufacture company of the
card.
•
This address is used by data link layer.
MAC address:
•
A hardware address that uniquely identifies each
node of a network.
•
In IEEE 802 networks, the Data Link Control (DLC)
Layer of the OSI.
Model is divided into two sub-layers
1. Logical Link Control (LLC) layer
2. Media Access Control (MAC) layer
• The MAC layer interfaces directly with the network
medium. Consequently, each different type of network
medium requires a different MAC layer.
• The chance to see the MAC address is very difficult for
any of your equipment.
• Software
that helps your computer communicate with a
network takes care of matching the MAC address to a
logical address.
• If you'd like to see the MAC address and logical address
used by the Internet Protocol (IP) for your Windows
computer, you can run a small program that Microsoft
provides.
• Go to the "Start" menu, click on "Run," and in the
window that appears, type WINIPCFG (IPCONFIG/ALL
for Windows 2000/XP).
• When the gray window appears, click on "More Info"
and you'll get information.
Logical address:
•An IP address of the system is called logical address.
• This address is the combination of Net ID and Host ID.
• This address is used by network layer to identify a
particular network (source to destination) among the
networks.
•This address can be changed by changing the host position
on the network. So it is called logical address.
•The IP address is the logical address assigned to your
connection by your ISP or network administrator.
•The logical address is what the network uses to pass
information along to your computer.
Port Address:
There are many application running on the computer.
Each application run with a port no.(logically) on the
computer.
This port no. for application is decided by the Karnal of the
OS.
This port no. is called port address.
Figure-3 Relationship of layers and addresses in TCP/IP
Example-1
In Figure-4 a node with physical address 10 sends a
frame to a node with physical address 87. The two nodes
are connected by a link (bus topology LAN). As the
figure shows, the computer with physical address 10 is
the sender, and the computer with physical address 87 is
the receiver.
Figure -4 Physical addresses
Example-2
Most local-area networks use a 48-bit (6-byte) physical
address written as 12 hexadecimal digits; every byte (2
hexadecimal digits) is separated by a colon, as shown
below:
07:01:02:01:2C:4B
A 6-byte (12 hexadecimal digits) physical address.
Example-3
Figure-5 shows a part of an internet with two routers
connecting three LANs. Each device (computer or
router) has a pair of addresses (logical and physical) for
each connection. In this case, each computer is
connected to only one link and therefore has only one
pair of addresses. Each router, however, is connected to
three networks (only two are shown in the figure). So
each router has three pairs of addresses, one for each
connection.
Figure-5 IP addresses
Example-4
Figure-6 shows two computers communicating via the
Internet. The sending computer is running three
processes at this time with port addresses a, b, and c. The
receiving computer is running two processes at this time
with port addresses j and k. Process a in the sending
computer needs to communicate with process j in the
receiving computer. Note that although physical
addresses change from hop to hop, logical and port
addresses remain the same from the source to
destination.
Figure-6 Port addresses
The physical addresses will change from hop to hop,
but the logical addresses usually remain the same.
Example-5
As we will see in Chapter 23, a port address is a 16-bit
address represented by one decimal number as shown.
753
A 16-bit port address represented
as one single number.