Comp277:Data Communications and Networking

Physical Addressing

1. Suppose, in a network connected in a Bus Topology, Terminal 10 wants to send a message to Terminal 87. At the data link layer, data will be encapsulated in a frame, and a header and trailer will be added. The header will contain the physical address of the receiver and the sender.

1. In a bus topology, signal will be propagated to each terminal. Other terminals will check if the header matches their own physical address, if not, it will be dropped. However, Terminal 87 will see that the header matches its own physical address so that data will be forwarded to the next layer.

Logical Addressing (IP Addressing)

The network layer is responsible for the source to destination delivery of packets, possibly across multiple networks (links). The network layer adds a header that includes the logical address of the sender and receiver to the packing coming from the upper layer. If a packet travels through the Internet, We need this addressing system to help distinguish the source and destination.

A logical address uniquely and universally defines the connection of the device. Currently, IPv4 is used which is a 32-bit long, IP addressing. The IPv6 is expected to be the dominant addressing in the future. There are 232address spaces in IPv4 which is equivalent to 4,294,967,296!

Logical addressing can be in binary notation or in dotted decimal notation.

Rules for IP address notation:

1. There must be no leading zero.
2. There can be no more than four numbers in IPv4.
3. Each number needs to be less than or equal to 255.
4. A mixture of binary notation and dotted decimal is not allowed.

Assignment:

1. Which of the following is not a valid IPv4 notation:

1. 111.56.045.78
2. 221.34.7.8.20
3. 75.45.301.14
4. 11100010.23.14.67

1. Change the following binary notation to dotted notation:

1. 01101111 00111000 00101101 01001110
2. 11011101 00100010 00000111 01010010

Answers:

1. All are not valid IPv4 notation because (a) has 045 – leading zero is not allowed; (b) has more than 4 numbers; (c) 301-is larger than 255; and (d) combination of binary notation and dotted decimal is not allowed.
2. a) 111.56.45.78b) 221.34.7.82

Port Addressing

Incomputer networkingaportis an application-specific or process-specific software construct serving as a communications endpoint in a computer's host operating system. A port is associated with anIP addressof the host, as well as the type of protocol used for communication. The purpose of ports is to uniquely identify different applications or processes running on a single computer and thereby enable them to share a single physical connection to apacket-switched networklike theInternet.

Specific Addressing

Some addresses are more descriptive and specific like domain names. Domain names include the organization's name, type of organization, and the country. Some examples of top-level domain names are:

Type of Organization:

.mil – military

.gov – government

.edu – educational

.com – commercial, unrestricted

.net – network, specific organizations

Countries:

.om – Oman

.ph – Philippines

.qa – Qatar

.my - Malaysia