assignment acn

8/4/2019 Assignment ACN

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Internal Assignments BCIIT/Assignment/ACN/01

Advanced Computer

Networks

(5th Semester)

Issue Date: 26/09/2011

Submission Date:03/10/2011

Total Marks: 35

5 marks deduction on late submission

Assignment Details:

Group A: Q1-Q12 (3,5,7,10,14,19,20,21.22.)

Group B: Q13-Q24 (23,24,26,38, 42,43,50,51,57)

The assignment had to be submitted handwritten on A-4 Lined sheets. The Assignment topics

along with their marks weight age are as under:

1. Draw and explain UNI and NNI cell format of the cells transmitted in ATM network and

differentiate among them. [3]2. Differentiate between repeaters, hubs, bridges, routers, and switches. Clearly state their

position in OSI layer.

Hub is typically the least expensive, least intelligent, and least complicated of the three. Its job is verysimple: anything that comes in one port is sent out to the others. That's it. Every computer connected to

the hub "sees" everything that every other computer on the hub sees. The hub itself is blissfully ignorant

of the data being transmitted. For years, simple hubs have been quick and easy ways to connect

computers in small networks.

Switch does essentially what a hub does but more efficiently. By paying attention to the traffic that comes

across it, it can "learn" where particular addresses are. For example, if it sees traffic from machine A

coming in on port 2, it now knows that machine A is connected to that port and that traffic to machine A

needs to only be sent to that port and not any of the others. The net result of using a switch over a hub is

that most of the network traffic only goes where it needs to rather than to every port. On busy networks

this can make the network significantly faster.

Router is the smartest and most complicated of the bunch. Routers come in all shapes and sizes from the

small four-port broadband routers that are very popular right now to the large industrial strength devicesthat drive the internet itself. A simple way to think of a router is as a computer that can be programmed to

understand, possibly manipulate, and route the data its being asked to handle. For example, broadband

routers include the ability to "hide" computers behind a type of firewall which involves slightly

modifying the packets of network traffic as they traverse the device. All routers include some kind of user interface for configuring how the router will treat traffic. The really large routers include the equivalent of

a full-blown programming language to describe how they should operate as well as the ability to

communicate with other routers to describe or determine the best way to get network traffic from point A

to point B.

Repeaters remove the unwanted noise in an incoming signal. Unlike an analog signal, the original digital

signal, even if weak or distorted, can be clearly perceived and restored. With analog transmission, signals

are restrengthened with amplifiers which unfortunately also amplify noise as well as information.



Bridge: Two partnerships of two players each are needed to play bridge. The four players sit around a

table with partners opposite one another. The compass directions are often used to refer to the four

players, aligned with their seating pattern.

Gateway: A gateway is a network point that acts as an entrance to another network. On the Internet, anode or stopping point can be either a gateway node or a host (end-point) node. Both the computers of

Internet users and the computers that serve pages to users are host nodes, while the nodes that connect thenetworks in between are gateways. For example, the computers that control traffic between company

networks or the computers used by internet service providers (ISPs) to connect users to the internet are

gateway nodes.

3. What are the various LAN technologies? Give their standards.

The 802 family of standards from the Institute of Electrical and Electronics Engineers (IEEE) defines

various types of LANs. Of these, 802.3 (which is commonly known as the Ethernet) is the most popular

LAN technology and is deployed widely throughout the world. Other LAN standards from IEEE include

802.4 (token bus), 802.5 (token ring), and 802.6 (FDDI)

The IEEE 802.1 standard provides an introduction to the set of 802 series of standards and defines

interface primitives. The IEEE 802 series of standards operate in the layer 1 and layer 2 (i.e., the physical

and data link layers), of the seven-layer OSI or the TCP/IP protocol models.

The logical link control (LLC) is the upper part of the data link layer and helps establish peer-to-peer

logical links between two 802 LAN protocol entities. The LLC layer is common to all 802 LAN

protocols, creating a layer of transparency between data link and network layer protocols. This allows

several 802 LAN protocols to be defined beneath the LLC layer that differ in their physical layer and

media access control (MAC) layer characteristics.

The MAC layer is the lower part of the data link layer. The MAC layer defines different addressing

formats and specific protocols used to arbitrate access to the 802 LAN system, for the various 802 LAN

standards. The MAC address is 48 bits in length and is a layer 2 address, used only in the data link layer.Of the 48 bits, the first two bits are for control and administrative purposes. The next field is the vendor

ID, which is generally assigned by the IEEE to any organization that needs it for use on devices such as

personal computers, servers, and printers.



The second part of the MAC address is "locally assigned" by the organization that owns the vendor ID.

When the IEEE assigns these addresses, they are truly global addresses and ensure that no two stations in

the world have the same MAC address.

The physical layer defines signaling mechanisms and transmission characteristics for the different LAN

standards. For example, in the 802.3 protocol, the physical layer defines data over media such as coaxial

cable, copper, and fiber-optic

4. Compare narrowband ISDN and broadband ISDN.

The most important development in the computer communications industry in the 1990s is the evolution

of the integrated services digital network (ISDN) and broadband ISDN (B-ISDN). The ISDN and B-ISDNhave had a dramatic impact on the planning and deployment of intelligent digital networks providing

integrated services for voice, data and video. Further, the work on the ISDN and B-ISDN standards has

led to the development of two major new networking technologies; frame relay and

asynchronous transfer mode (ATM). Frame relay and ATM have become the essential ingredients indeveloping high-speed networks for local, metropolitan and wider area applications.

The ISDN is intended to be a worldwide public telecommunications network to replace existing public

telecommunication networks and deliver a wide variety of services. The ISDN is defined by the

standardization of user interfaces and implemented as a set of digital switches and paths supporting a broad range of traffic types and providing value added processing services. In practice, there are multiple

networks, implemented within national boundaries but from the user's point of view, the eventual

widespread deployment of ISDN will lead to a single, uniformly accessible, worldwide network.

The narrowband ISDN is based on the use of a 64 kbps channel as the basic unit of switching and has acircuit switching orientation. The major technical contribution of the narrowband ISDN effort has been

frame relay. The B-ISDN supports very high data rates (100s of Mbps) and has a packet

switchingorientation. The major technical contribution of the B-ISDN effort has been asynchronous

transfer mode, also known as cell relay.CIRCUIT SWITCHING

The circuit switching is the dominant technology for both voice and data communications.

Communication via circuit switching implies that there is a dedicated communication path between two

stations. That path is a connected sequence of links between network nodes. On each physical link, a



channel is dedicated to the connection. The three phases involved in a communication via circuit

switching are circuit establishment, information transfer and circuit disconnect.

PACKET SWITCHING

In a typical data connection much of the time the line is idle. Thus circuit switched approach is

inefficient. In packet switching data are transmitted in short packets. Each packet contains a portion of the

user's data plus some control information. The control information, at a minimum, includes theinformation that the network requires to be able to route the packet through the network and deliver it to

the intended destination. At each node enroute, the packet is received, stored briefly, and passed on the

next node. The advantages of packet switching are line efficiency is greater, data rate conversion is

possible and priorities can be used.

FRAME RELAY

With modern, high-speed telecommunication systems, the overhead in error control is unnecessary and

counter productive. To take advantages of the high data rates and low error rates of contemporary

networking facilities, frame relay was developed. Whereas the original packet switching networks were

designed with a data rate to the end user of about 64 kbps, Frame relay networks are designed to operate

at user data rates of up to 2 Mbps. The key to achieving these high data rates are to strip out most of the

overhead involved with error control.

5. What are the various open loop and closed loop methods for handling the congestion? [3]

6. What kinds of error are controlled by the Error control mechanisms at the data link layer? [3]7. Explain leaky bucket algorithm. [3]8. Explain ATM. [3]9. Explain Hidden station problem. [3]10. Draw IPV4 header and explain in detail. [3]11. A host with IP address 130.23.43.20 and physical address Ox B23455102210 has a packet to

send to another host with address 130.23.43.25 and physical address Ox A46EF45983AB. Thetwo hosts are on the same Ethernet network. Show ARP request and reply packet encapsulated in

Ethernet frame. [3]12. Explain RIP protocol in detail. [3]

[3]18. Explain the types of BGP messages. Explain the various fields involved.

BGP performs interdomain routing in Transmission-Control Protocol/Internet Protocol (TCP/IP)

networks. BGP is an exterior gateway protocol (EGP), which means that it performs routing

between multiple autonomous systems or domains and exchanges routing and reachabilityinformation with other BGP systems

Four BGP message types are specified:

A Border Gateway Protocol 4 (BGP-4):

Open message, update message, notification message, and keep-alive message.

The open message opens a BGP communications session between peers and is the first messagesent by each side after a transport-protocol connection is established. Open messages are

confirmed using a keep-alive message sent by the peer device and must be confirmed before

updates, notifications, and keep-alives can be exchanged.



An update message is used to provide routing updates to other BGP systems, allowing routers to

construct a consistent view of the network topology. Updates are sent using the Transmission-Control Protocol (TCP) to ensure reliable delivery. Update messages can withdraw one or more

unfeasible routes from the routing table and simultaneously can advertise a route while

withdrawing others.

The notification message is sent when an error condition is detected. Notifications are used to

close an active session and to inform any connected routers of why the session is being closed.

The keep-alive message notifies BGP peers that a device is active. Keep-alives are sent often

enough to keep the sessions from expiring.

19. Explain the various query messages in ICMP. Also draw and explain the packet formats.

The IP (Internet Protocol) relies on several other protocols to perform necessary control and

routing functions:• Control functions (ICMP)

• Multicast signaling (IGMP)• Setting up routing tables (RIP, OSPF, BGP, PIM, …)

The Internet Control Message Protocol (ICMP) is a helper protocol that supports IP with facility

for – Error reporting

– Simple queries

ICMP messages are encapsulated as IP datagrams:



20. Describe the various links in OSPF.

1.Point-to-point Link:On point-to-point links such as High-Level Data Link Control (HDLC) and Point-to-Point Protocol

(PPP), Open Shortest Path First (OSPF) runs as a point-to-point network type. This network type is

enabled by default. This document shows sample configurations for OSPF over a point-to-point link. The

other network types that OSPF supports are Point to Multipoint, Broadcast, and Non-Broadcast. In order

to check the network type of an interface that runs OSPF, issue the show ip ospf interface command.

2.Transient Link:In OSPF, a transient link is a network with several routers attached to it. The data can enter through any

router and can leave through any router. All LANs and WANs with two or more routers are of this type.

In transient networks, each router has many neighbors.

3.Stub Link:A stub interface could be a loopback interface or any other point-to-point or multipoint interface on which

there are no OSPF neighbors.

4. Virtual Link:

Virtual link is a logical connection to create virtual adjacency between two areas using the least cost

path.Two conditions must be fulfilled to apply a virtual link between different areas.

• One area must be area 0 (backbone area) to create virtual link.

• One area must be common area between two endpoint routers to create virtual links.



21. What are the various components of a CISCO Router? Explain them briefly.

In order to configure and troubleshoot a Cisco internetwork, you need to know the major components of Cisco routers and understand what each one does. Table as below describes the major Cisco router

components.

Component Description

Bootstrap

Stored in the microcode of the ROM, the bootstrap is used to bring

a router up during initialization. It will boot the router and then

load the IOS.

POST (power-onself-test)

Stored in the microcode of the ROM, the POST is used to check the basic functionality of the router hardware and determine which

interfaces

are present.

ROM monitor Stored in the microcode of the ROM, the ROM monitor is used for manufacturing, testing, and troubleshooting.

Mini-IOS

Called the RXBOOT or bootloader by Cisco, the mini-IOS is a small

IOS in ROM that can be used to bring up an interface and load a

CiscoIOS into flash memory. The mini-IOS can also perform a few other

maintenance

operations.

RAM

(randomaccessmemory)

Used to hold packet buffers, ARP cache, routing tables, and also

the software and data structures that allow the router to function.

Running-config is stored in RAM, and the IOS can also be run fromRAM in some routers.

ROM (read-onlymemory) Used to start and maintain the router.

Flash memory

Used on the router to hold the Cisco IOS. Flash memory is not

erased

when the router is reloaded. It is EEPROM (electronically erasable programmable read-only memory) created by Intel.

NVRAM (nonvolatileRAM)

Used to hold the router and switch configuration. NVRAM is not

erased

when the router or switch is reloaded.

Configurationregister

Used to control how the router boots up. This value can be seenwith the show version command and typically is 0×2102, which tells

the router to load the IOS from flash memory as well as telling the

router to load the configuration from NVRAM.

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