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Thursday, December 13, 2012

::: vuaskari.com ::: CS610-MID TERM SUBJECTIVE With REFERENCE SOLVED BY UMAIR SAULAT

CS610 - COPMPUTER NETWORK

MID TERM SUBJECTIVE SOLVED

QUESTION ONLY 2012

Qno.1 in LAN of 8 pcs, at low cost which wire scheme you will use. Give reasons

Answer:-

Reasons:-

· Twisted pair Ethernet is the cheapest wiring that makes it so popular.

· To allow changing the wiring without changing the interface hardware, NICs support

· Multiple wiring schemes are not limited to Ethernet technology.

· hubs (physically a star topology) to simulate a logical ring network.

· The distance between devices

· The amount of em-noise

REF:: Handouts Page No. 45,47

Qno.2 how many bits contains in VCI & VPI

Answer:-

· Virtual Channel Indicator (16-bits)

· Virtual Path Indicator (8- bit),

REF:: Handouts Page No. 67

Qno.3 we have a bridge network that has two segments. is that possible to transfer data simultaneously through segments ?

Unlike a repeater, a bridge uses two NICs to connect two segments. It listens to all traffic and recognizes frame format. It also forwards only correct complete frames and discards the collided and error frames. A typical bridge has two NICs, a CPU a memory and a ROM. It only runs the code stored in its ROM. A network bridge can be used to segment one network into two, thereby reducing the number of devices competing for transmission privileges.

For example,

if network A has 20 devices, there is the likelihood that two or more of them will attempt to transmit data at the same time and cause a collision. If a network bridge is added, it can split network A into networks A and B of 10 devices each.

REF:: Handouts Page No. 50

Qno.3 is there any technology that use LAN and WAN both topologies. if yes then write its

Name

Star Topology, all computers are attached to a central point, which is sometimes called the Hub

Ring Topology network the computers are connected to each other in closed loop. In this network first computer passes data to the second and then second passes data to third and so on,

REF:: Handouts Page No. 25

Qno.4 why packet switch check the header frame before forwarding the packet

Answer:-

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.

REF:: Handouts Page No. 56

Qno.5 Why the designer of ATM technology select cells not packets? Give five reasons

Answer:-

Reason:

ATM multiplexed these 53-byte cells instead of packets which reduced worst-case cell contention jitter by a factor of almost 30, reducing the need for echo cancellers.
Reduction of jitter (and also end-to-end round-trip delays)
Full-length 1500 byte (12000-bit) data packet would take 77.42 to transmit.
The design of ATM aimed for a low-jitter network interface
ATM broke up all packets, data, and voice streams into 48-byte chunks, adding a 5-byte routing header to each one so that they could be reassembled later

REF:: Handouts Page No. 66

http://en.wikipedia.org/wiki/Asynchronous_Transfer_Mode

Qno.6 If two far away situated offices are to connect with will be appropriate LAN extension or WAN. Give four reasons to support you answer

If two buildings are located far from each other, a bridge, a pair of fiber modems and an optical fiber can be used to connect two LANs
LAN segments that need to be interconnected but are slightly far away, point to point wireless solutions are available
They are generally kept over a tower so that line of sight is realized between the locations, for best performance.
These outdoor access points are configured to operate in the point-to-point or point-to-multipoint modes and one such access point along with antenna/tower is required in each department/building which needs to be interconnected.
In certain areas, metro Ethernet might be available where the service provider has the infrastructure to connect two locations of a same branch located in different places at speeds of 10/100 Mbps using his public network infrastructure

REF:: Handouts Page No. 51

http://www.excitingip.com/653/what-are-the-various-ways-to-extend-a-local-area-network-lan/

Qno.7 writes three benefits of routing if source address is not included in the header

Answer:-

Benefit

It allows fast and efficient routing.

Packet switch need not hove complete information about all destinations in spite it just has next The network can continue to function even if topology changes without notifying entire network
REF:: Handouts Page No. 58

Qno.8 How many methods are available to span a network over longer distances? Just write their names. (2 Marks)

Answer:-

LEASED SERIAL LINE CONNECTION:
LEASED SATELLITE CHANNEL:

REF:: Handouts Page No. 52

Qno.9 which two identifier in ATM are used to make Virtual Circuit? (2 Marks)

Answer:-

VCI (Virtual Channel Indicator)

VPI (Virtual Path Indicator)

REF:: Handouts Page No. 67

Qno.10 conceptual question about Virtual private Network.(marks 3)

Answer:-

Virtual Private Network (VPN) combines the features of both private and public networks. It is limited to single organization and uses public network for connectivity. These connections are sometimes called tunnels and connect sites. Each site sees tunnel as point-to-point link. There is no access for other users of public networks.

REF:: Handouts Page No. 75

Qno.11 Describe the procedures in steps of Telephone calling, A connection oriented service (Marks5)

Answer:

The connection-oriented service paradigm for networking is similar to the manner in which telephones are used. This is given as follows:

A caller dials a number of the destination. The telephone at the destination signals the arrival of a connection request. If the called person does not answer; the caller gives up after waiting for a timeout. If the called person does answer, then the connection is established as binary connection identifier is given to each of the two parties to enable identification of the connection.

REF:: Handouts Page No. 67

Qno.12 Describe two major components of thick Ethernet (2)

Answer:-

Network interface card (NIC)
Analog electronic device

REF:: Handouts Page No. 42

Qno.13 Suppose in a computer network of a chemical company, each packet is transferred with equal amount of time between systems. Consider this scenario what will be the jitter?(2)

Answer:-

The amount of delay that a network introduces is called jitter. A network with zero jitter takes exactly the same amount of time to transfer each packet. A network with high jitter takes much longer to deliver some packets than others

REF:: Handouts Page No. 80

Qno.14 Suppose in university campus, bridges are used in its local are network. Explain all steps, how bridge build up address list table of all attached computers. (3)

Answer:-

University campus implement bridges to attached the computers, bridges as a frame arrives to it, extracts a source address from its header and automatically adds it in the list for that segment. In this way a bridge builds up address lists.

REF:: Handouts Page No. 50

Qno.15 Suppose an organization wants voice communication in a network by using ATM technology. Explain how ATM eliminates the varying delays associated with variable size data packets.

Answer:-

Organization wants voice communication introduced ATM to meet several goals. It provides universal service for all subscribers and support for all users for voice, video and data. It has a single unified infrastructure (no separate LANs and WANs). It gives guaranteed service when it is appropriate and support for low cost devices.

JITTER:

Jitter is the term used for variance in transmission delays. Jitter is significance for voice, video and data. In LANs, jitter can occur when a packet is delayed because the network is busy.

PACKET SIZES:

Large packets result in fewer overheads because a smaller fraction of the packet is used for header information. Optimum networks use 4kB packets or larger. Large packets can't easily be used for voice for example 8-bit samples (at 125usec per sample) would require half a second to fill a 4kB packet. Echo cancellation can only be used with low transmission delays.

REF:: Handouts Page No. 66

Qno.16 While designing the ATM technology why designer of ATM chosen cells over packets which being used widely? Give five reasons to support your answers.(5)

Reason:

ATM multiplexed these 53-byte cells instead of packets which reduced worst-case cell contention jitter by a factor of almost 30, reducing the need for echo cancellers.
Reduction of jitter (and also end-to-end round-trip delays)
Full-length 1500 byte (12000-bit) data packet would take 77.42 to transmit.
The design of ATM aimed for a low-jitter network interface
ATM broke up all packets, data, and voice streams into 48-byte chunks, adding a 5-byte routing header to each one so that they could be reassembled later

REF:: Handouts Page No. 66

http://en.wikipedia.org/wiki/Asynchronous_Transfer_Mode

Qno.17 Suppose star organization using repeater in its network. If frames comes from another network then will the repeater be capable of distinguish between frames from two different networks? Support your answer with a reason also writes down three drawbacks, this organization may face due to use of repeater.

Answer:-

Drawbacks

1. Repeaters provide no method for isolating traffic generated on one cable segment from traffic generated by the other cable segment

2. When network uses a repeater to connect cable segment A to segment B whether or not there is a station in segment B that is the destination of the signal

3. Ethernet standard specifies that any two stations cannot be separated by more than four repeaters.

4. Repeaters do not recognize frame formats; 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.

REF:: Handouts Page No. 50

http://oderog.hubpages.com/hub/Function-of-repeaters-in-a-network

Zindagi mein 2 Logo ka buhat khayal rahkoooo
Ist woh jiss ney tumhari jeet ke Liye buhat kuch hara hoo

(Father)

2nd woh jiss ko tum ney har dukh me pukaara hoo (Mother)

Regards,

Umair Saulat Mc100403250