CS610 - Computer Network
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Short Question & Answers
Q40: Write a note on thick Ethernet, thin Ethernet and twisted pair Ethernet.
Thick Ethernet: Thick Ethernet, officially known as 10 Base-5, is the oldest form of Ethernet. One form of cabling supported by Ethernet is low-loss 50 Ohm coaxial cable as shown in the figure below. This type of cable is 0.5" diameter (usually supplied with a yellow outer PVC coating) and rather inflexible. It has become known in the communications industry as "Thick Ethernet". The official name for this cable is 10 Baseband5 (10B5), indicating that it is specified for baseband communications at 10 Mbps over distances up to 500m.

Thin Ethernet: Thin Ethernet, officially called 10 Base-2, is a less expensive version of 10 Base-5 (Thick Ethernet) technologies. It uses a lighter and thinner coaxial cable and dispenses with the external transceivers used with 10 Base-5. 10 Base-2 uses an RG-58A/U coaxial cable and is wired in a bus topology. Each device on the network is connected to the bus through a BNC "T" adapter, and each end of the bus must have a 50 Ohm terminator attached. Each node on the bus must be a minimum of 0.5 meters (1.5 feet) apart, and the overall length of the bus must be less than 185 meters (606 feet).

Twisted Pair Ethernet: Twisted Pair Ethernet (10baseT), sometime also called "UTP" from "Unshielded Twisted Pair", is based on using a cable similar to phone-wiring. The cable is connected via RJ-45 connectors to the network card installed in the PC.
Q41: Why 10-base T wiring scheme is called star shaped bus wiring scheme.
The main feature of twisted pair Ethernet is that it forms a classic star topology however functions like a bus. 10Base-T Ethernet is often called a star shaped bus.
Q42: What are default routes draw the table.
Routing table entries can collapse with a default route. If destination doesn’t have in explicit routing table entry and then it use a default route. It is shown in the below table.
Q43: What is stored in routing table and what are the Routing Table Entries and Sizes?
A routing table is used by TCP/IP network routers to calculate the destinations of messages it is responsible for forwarding. The table is a small in-memory database managed by the router's built-in hardware and software. Routing tables contain a list of IP addresses. Each IP address identifies a remote router (or other network gateway) that the local router is configured to recognize. For each IP address, the routing table additionally stores a network mask and other data that specifies the destination IP address ranges that remote device will accept.
Q44: How can Switched Virtual Network be established?
SWITCHED VIRTUAL CIRCUITS: Most networks offer dynamic connections, which last for a relatively short time. To handle this, ATM can dynamically establish a switched virtual circuit (SVC), allow it last as long as necessary and then terminate it. The terminology comes from the Telco’s where switching system normally refers to all switching.

ESTABLISHING AN SVC: The computer sends a connection request to the switch to which it is attached. Software in the switch finds a network path to the destination and sends along the connection request. Each pair of switches in the path communicates to choose a VPI/VCI for their tables. Once the connection is established by the destination, a message is sent back to the originating computer to indicate the SVC is ready. If any switch or the destination computer does not agree to setting up the VC, an error message is sent back and the SVC is not established.
Q45: What is the concept of store and forward technology?
STORE AND FORWARD: Data delivery from one computer to another is accomplished through store and forward technology. In this technology packet switch stores incoming packet and also forwards that packet to another switch or computer. For this purpose packet switch has internal memory into which it can hold packet if outgoing connection is busy. Packets for each connection held on queue.
Q46: What are implementations of NAT?
The figure below shows the implementation of NAT. We can see that the old and new values of IP source field and destination field are shown with their directions.
Q47: What are the advantages of a multipoint connection over a point-to-point connection?
Point-to-point connection is limited to two devices, where else more than two devices share a single link in multipoint connection. Multipoint connection can be used for fail-over and reliability.
Q48: What's the name of the telephone service in which there is no need of dialing?
DSS (digital data service) is the telephone service in which there is no need of dialing
Q49: Which type of frames is present in BSC frames?
There are two types of frames that are present in BSC:
1. Control Frames and 2. Data Frames
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