CS610 - Computer Network
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Short Question & Answers
Q14: Difference between LAN and WAN.
In LAN network occupies the smaller area like a room a floor or a building. In WAN, network occupies larger areas like cities & countries. Internet is a Wide Area Network.
Q15: Why fiber needs fir ATM 3 marks define bridge.
A bridge is a hardware device also used to connect two LAN segments to extend a LAN. A typical bridge has two NICs, a CPU a memory and a ROM. It only runs the code stored in its ROM.
Q16: Defines simplex and full duplex connection?
Some connection-oriented technologies provide full duplex while other allow on simplex connection. To communicate using a simplex design a pair of computers must establish two connections one from computer A to computer B and another from computer B to A.
Q17: How WAN capable to handle many computers?
A Wide Area Network (WAN) is a telecommunication network that covers a broad area.
Q18: Briefly explains the working structure of thick Ethernet.
It uses thick coax cable. AUI cable (or transceiver or drop cable) connects from NIC to transceiver. AUI cable carries digital signal from NIC to transceiver. The transceiver generates analog signal on coax cable. The wires in AUI carry digital signals power and other control signals. Thick Ethernet also requires terminators to avoid signal reflectance.
Q19: Why ATM design chose cells over packet?
• Cells are not variable length and memory management for them is simpler. Handling variable length packets leads to memory fragmentation.

• Variable length packets require hardware to accommodate the largest possible packet, and thus to detect the end of the packet. With cells bits can just be counted as they arrive.

• The length of time required to send a variable length packet is variable and requires complicated interrupt scheme to detect completion of transmission. QoS can’t be guaranteed with variable length packets as easily as it can with fixed length cells.
Q20: What is 10base T?
One of several adaptations of the Ethernet (IEEE 802.3) standard for Local Area Networks (LANs). The 10Base-T standard (also called Twisted Pair Ethernet) uses a twisted-pair cable with maximum lengths of 100 meters.
Q21: What is Multicasting?
It works like broadcasting however it does not forward frames automatically to the CPU. The interface hardware is programmed in advance to accept certain frames that have multicast address as the destination address.
Q22: What is FDDI?
Fiber distributed data interconnect (FDDI) is another ring technology. Its most important features are: It uses fiber optics between stations and transmits data at 100Mbps. It uses pair of fibers to form two concentric rings.
Q23: Define 802.11 Wireless lans and CSMA?
IEEE 802.11 is standard wireless LAN that uses radio signals at 2.4GHz. Its data rate is 11Mbps. The older devices use radio signals at 900MHz and data rate of 2Mbps. Bluetooth specifies a wireless LAN for short distances. It uses shared medium and radio waves instead of coaxial cable.
Q24: Define static and dynamic routing.
Static routing is the simplest form of routing, but it is a manual process. It is one of the forms of Internet routing. In Static routing, the table is initialized. When system boots and there is no further changes.

Dynamic routing protocols are supported by software applications running on the routing device (the router) which dynamically learn network destinations and how to get to them and also advertise those destinations to other routers. In dynamic routing the table is initialized when system boots. It includes routing. Software which learns routes and updates table. In this way continuous changes are possible due to routing software.
Q25: What are the disadvantages of Repeaters?
Repeaters do not recognize frame format, they just amplify and retransmit the electrical signal. If a collision or error occurs in one segment, repeaters amplify and retransmit also the error onto the other segments.
Q26: Different b/w Cells and Packets.
ATM designers chose cells over packets because of the following reasons:
• Cells are not variable length and memory management for them is simpler. Handling variable length packets leads to memory fragmentation.

• Variable length packets require hardware to accommodate the largest possible packet, and thus to detect the end of the packet. With cells bits can just be counted as they arrive.

• The length of time required to send a variable length packet is variable and requires complicated interrupt scheme to detect completion of transmission. QoS can’t be guaranteed with variable length packets as easily as it can with fixed length cells.
Q27: What is the difference between the physical and logical topologies?
Every LAN has a topology, or the way that the devices on a network are arranged and how they communicate with each other.

PHYSICL TOPOLOGY: The way that the workstations are connected to the network through the actual cables that transmit data -- the physical structure of the network -- is called the physical topology. It depends on the wiring scheme.

LOGICAL TOPOLOGY: The logical topology, in contrast, is the way that the signals act on the network media, or the way that the data passes through the network from one device to the next without regard to the physical interconnection of the devices. We can say that it is defined by the specific network technology.
Course Instructor

Mr. Hammad Khalid Khan
M.S Electrical Engineering
(Telecommunication)
Oklahoma State University USA
Books

Computer Networks & Internets with Internet Applications by Douglas E.Comer

Computer Networks by Andrew S. Tanenbaum

Networking: A Top-Down Approach Featuring the Internet by James F. Kurose and Keith W. Ross