mscc tns assignment ii student number 2823134 abid afsar

Abid Afsar TNS Assignment II Student Number: 2823134

Assignment Cover Sheet

Student name: Abid Afsar

Student number: 2823134

Faculty: Computing Science

Course: TNS Stage/year: 1

Subject:

Study Mode: Full time Yes Part-time

Lecturer Name: Faheem Bukhatwa

Assignment Title: TNS

No. of pages: 20

Disk included? Yes No No

Additional Information:

(ie. number of pieces submitted, size of assignment, A2, A3 etc)

1


Date due: 23/12/2011

Date submitted: 23/12/2011

Plagiarism disclaimer:

I understand that plagiarism is a serious offence and have read and understood the college policy on plagiarism. I also understand that I may receive a mark of zero if I have not identified and properly attributed sources which have been used, referred to, or have in any way influenced the preparation of this assignment, or if I have knowingly allowed others to plagiarise my work in this way.

I hereby certify that this assignment is my own work, based on my personal study and/or research, and that I have acknowledged all material and sources used in its preparation. I also certify that the assignment has not previously been submitted for assessment and that I have not copied in part or whole or otherwise plagiarised the work of anyone else, including other students.

Signed: _______ ______________ Date:

___23/12/2011___________________

2

Please note: Students MUST retain a hard / soft copy of ALL assignments as well as a receipt issued and signed by a member of Faculty as proof of submission.


(1) Compare the ATM protocol’s architecture and associated

layers, to those of the ISO-OSI reference model. Your answer or

diagram should show the layers in each protocol stack.

Answer:

International organization for standardization (ISO) also referred

as Open system interconnection (OSI) reference model has the

following seven layers,

i. Application layer

ii. Presentation layer

iii. Session layer

iv. Transport layer

v. Network layer

vi. Data link layer

vii. Physical layer

In comparison to OSI reference model, asynchronous transfer mode

(ATM) has the following three layers

i. ATM Adaptation layer

ii. ATM layer

iii. Physical layer

The OSI model is used for the transmission over unreliable

medium, while ATM model works with reliable transmission

3


medium, and it also accommodate a mechanism for error

detection and correction.

In term of reliability ATM is currently the most reliable mode

of transmission in comparison to OSI model.

ATM model corresponds to functionality physical and portion

data layer of OSI model.

Diagrammatically the concept is represented as

Figure 1: Comparison Diagram of ATM and OSI Architecture

4


OSI lowest layers are related to ATM, and diagrammatically it is

represented as,

Figure 2: Relation of OSI and ATM

(2) Show with the help of a diagram the flow of cells in a real

Communication from end to end, up and down the layers in the

ATM Model. Show two intermediate switches in the diagram.

Answer:

5


In term of sending user information, ATM protocol architecture

is similar to TCP/IP protocol suit. ATM works same like

TCP/IP to forward user information form one machine to

another in the form of packets.

In regards to routing or switching and control is completely

different because it fully connection- oriented which it establish

in form of virtual connection

First a unique virtual connection is established which have their

VCI number

Next communication begin and signalling standard agreement

take place and then data transmission start from one user

machine to another and exactly an original data order

Finally, on completion of transmission connection is terminated

ATM network mange data in specific order to manage the

quality of services in a most sophisticated manner

On higher level it uses user plan and control plan for data

Diagrammatically the concept is visualised as,

6


Figure 3: End- to-End Communication an ATM network

(3) Describe in details the ATM Cell structure.

Answer:

An ATM use a fixed cell also called packet which is

composed of 5 bytes of header and 48 bytes of payload. All

data in ATM network is switched and multiplexed in the form

of ATM cell.

In diagrammatic form it is represented as

ATM Cell 7


Figure 4: ATM Cell

ATM cell header can have the following two header format

that is UNI (User to Network Interface) and NNI (Network-

to-Network Interface). The UNI is interface is between

network device and end user while NNI is between network

to network device or between the two back bone networks

Diagrammatically the concept of UNI and NNI is illustrated

as,

8


Figure 5: UNI and NNI interface format

The above diagram can be explained as, in ATM cell header

fields the first one is GFC( generic flow control) it provides

local function, the second one is VPI(virtual path identifier)

it is a unique identification number for every virtual path,

third one is VCI (virtual channel number) it is a unique

identification number of every virtual circuit, fourth one is

Payload type identify that weather it contain user data or

control data, fifth one is CLP(congestion lost priority) it

identify that if a cell shows congestion it should be

discarded or it show the status of congestion in the network

and sixth one is HEC(header error control) it provided

information in relation to any error encountered

Multiplexing is also in important feature of ATM cell, it

multiplex different forms of data such voice, video and text.

Multiplexing improve overall efficiency and also improve

the performance of overall resources, diagrammatically it is

illustrated as

9


Figure 6: ATM Cell Multiplexing

(4) Describe the address fields used for ATM addressing. Use a

diagram to show the fields.

Answer:

ATM address use virtual circuit and it is 20 bytes in length

and the ATM has three distinct formats, in general term it is

represented as

Figure 7: ATM address Format

The parts of an ATM address can be defined as, the first part

is the ATM switch identifier it composed of 13 bytes, and

10


identifies the switch position in network. The main three

addressing scheme viewing location of switch differently.

The second one is adapter MAC address hold 6 bytes. It

shows the particular adapter type in the ATM network and the

MAC address operation is similar like in Ethernet or token

ring. The third one is selector (SE) hold a space of 1 byte, and

it chooses a logical connection end point on physical ATM

adapter.

The three addressing schemes use in ATM networks are

i. Data Country/region Code (DCC)

ii. International Code Designator (ICD)

iii. E.164

The three different format of ATM address is

diagrammatically illustrated as

11


Figure 9: ATM Distinct Address Format

(5) Describe the structure of the ATM Adaptation layer AAL5 and

the services provided by each.

Answer:

The AAL layer provide interface to the upper layer of the

ATM reference model

It further sub divide into two sub layers that is segmentation

and reassembling, and convergence

The basic duty of ALL layer is the format conversion

The ALL received 48 bytes payload from higher level layer

and a header of 5 bytes from ATM layer

ALL have four different types that are AAL 1, ALL 2/3, ALL

4 and AAL 5.

12


These different types of ALL’s can also be distinguished by

connection oriented or connectionless mechanism. The ALL

1, 2,5 are pulley connection oriented while ALL ¾ is partly

connection oriented and AAL ¾ is partly connectionless as

well.

Diagrammatically it is represented as

(6) What are Partial Packet Discard (PPD) and Early Packet

Discard (EPD)?

Answer: these are the ATM cell discard techniques and segments

large size packets into a series of bursts at ATM and ALL 5 cells.

This phenomenon is very useful at ATM over IP (AIP) and ATM

over LAN emulation (LANE) networks. These techniques closely

work with traffic policy and also look on to QoS as well. When the

13


cells of a large packet are dropped due to some reason and some of

the fragmented packets are also discard and will be send for

transmission. The discarding or dropping of fragmented packets are

call partial packet discard (PED). And when cells are fragmented

portion of a large packet, and are known in advance that the buffer

space is not sufficient to accommodate the entire packet, and then

there is no need to send some of its cells. It is better to discard the

entire packet and will be retransmitted this whole phenomena is

called early packet discard (EPD)

(7) Discuss in details four traffic control mechanisms used in the

ATM Model.

Answer: the ATM network should always be capable to recover

from any sort of potential errors, weather a human or machine error

such as intermittent or accidental and so on. The following control

mechanism are widely used in ATM traffic management arena

1. Network Recourse Management: This is always a priority of

network management to achieve good quality and efficiency,

and meet the user quality of service requirements. There is no

perfect standard for network resource is available until today.

The core problem is the statistical behaviour of the ATM

networks because several cells were entered into the buffer from

different sources and also due multiplexing as well.

14


2. Connection Admission Control: it is the initial call setup

procedure, and to establish a virtual channel or path that is

acceptable to the network. It will make sure that the new

connection will not devalue the other connection already in

place and the quality of other channel is not affected.

3. Usage Parameter Control and Network parameter Control

(UPC/NPC): These two techniques doing different function at

network interface. The UPC is functioning on user network

interface while NPC functioning on network node interface. the

main purpose of UPC and NPC is to secure the network

resources from intentional and malicious attack. It will also

check the validity of VPI/VCI entries, monitor traffic volume for

the agreed traffic parameter and standards and guarantee that all

traffic obeying the specified criteria, and check the accepted

traffic volume on each access link.

4. Priority Control: An ATM cell have the priority cell loss bit in

the header. And the information is classed according to their

priority and at least an ATM cell has two distinguished classes.

5. Traffic Shaping: It is a form of alerts given at the time when

there is a speedy traffic on an access link, these alerts are given

to slow their peak cell rate, limit the cell delay by appropriately

organising the cells in time.

15


6. Congestion Control: is a state of a network in which the traffic

overload or overflow on the network, everything jammed , and

no new network connection can be established, the

unguaranteed quality of service network is not able to add or

remove network connection. These problem can be solved by

using the above mechanism such as connection admission, and

UPC and NPC.

(8) Explain in detail how IP over ATM takes place. Your

explanation must discuss: connecting IP to an ATM, addresses and

the transfer of IP data grams.

Answer: ATM network is connection oriented network and it

widely support network protocols such as IP, Framerelay, and

IPv6, IPX, Decnet and so on. An ATM use three types of

connection which are permanent virtual circuit (PVC) and Soft

PVC, and short virtual circuit (SVC). The ATM network is divided

into logical networks and each logical network has own separate IP

subnet also called logical subnet (LIS). Every system in the LIS has

share the same IP prefix and net mask. In LIS end system

communicant with each other through ATM end-to-end

connection. And in a different LIS’s the communication is take

place through router.

16


(9) Describe the link state routing algorithm and list its advantages

over distance vector routing algorithm.

Answer:

Link state is a routing protocol such as OSPF and IS-IS used in

packet switch networking in computer communication. The main

concept of the link state routing protocol is that every network node

has to take routing information of the connected neighbours in the

form of a table. Every network node calculates best to the other

concerned destination. The calculated best path is then place in

routing table.

Advantages:

1. Link state algorithm converge fast than distance vector protocol

2. It use multicast to share the network information

3. It support classless routing

4. Link state operate better at large enterprise network

5. It has small routing table

6. It is capable of scalability

7. It has a low network overhead

8. It has no node limits

9. It use cost for shortest path findings

17


(10) Compare memory requirement imposed on the receiver node

by selective reject protocol and the go-back-N protocol. Give

examples to support your answers.

Answer:

Go-Back-N protocol manage the transmission time involved at

receiver end, and the transmission time of acknowledgment to come

back at sender end, and are carefully checked for efficiency purpose

and the technique is called pipelining. The sender is obliged to keep

track of frames and their concerned acknowledgment, and also have

to look timeout interval as well. As a result of tracking of each record

the memory requirement for sender is increased. On the other hand

the receiver only receives the frame or acknowledgment which the

receiver need. In situation where frame lost or duplication occurs in

frames or acknowledgments, the receiver discards whole frame, and

call for resend. In memory perspective the receiver only need

memory, when the frame is in right order with no error, lost and

duplication.

For example: we want to send frames of window size 9, can be shown in the following figure

0 1 2 3 4 5 6 7 8

0 1 2 3

discard

4

discard

5

discard

6

discard

7

discard

8

discard

18

Receiver End

Sender End

Ack 0 Ack 1


Error

2 3 4 5 6 7 8

2 3 4 5 6 7 8

In the above figure error occur in frame 2 and all the subsequent

frames were also discarded. The sender was not aware of the problem,

and again sends the same copies of the frame because of the timeout

interval expiry. The limitation of go-back-n protocol is the sender

unawareness of the problem, and this makes it inefficient. And

negatively affect the channel usage, memory at sender side, and

bandwidth.

In contrast selective reject protocol when the problem occur during

delivery of the frames, only particular frames were send back again by

the sender. On the receiver end all frames are not discarded and only

damage frame is acknowledged. In selective reject protocol receiver

side buffer size is increased because of keeping every correct frame

send by the sender. In this technique both sender and receiver

19

Receiver End

Ack 2 Ack 3

Sender End

Ack 4 Ack 5 Ack 6

Retransmission of the same frames


vigilantly watch their time counter, and the receiver have knowledge

that which frame has a problem and need to be re-acknowledge. It

uses NAK (negative acknowledgment) for lost or damaged bit

retransmission.

For example: we want to send frames of window size 9, using

selective reject protocol is shown in the following figure

0 1 2 3 4 5 6 7 8

0 1 2

Error

3

buffered

4

buffered

5

buffered

6

buffered

7

buffered

8

buffered

Selective reject protocol improves the channel usage time and

bandwidth, and also has a positive effect on the overall efficiency of

transmission between sender and receiver.

20

Receiver End

Sender End

Ack 0 Ack 1 NAk 2 Ack 1 Ack 2 Ack 3 Ack 4


Bibliography

[1]. Tanenbaum, Andrew S. Computer Networks. Upper Saddle

River, NJ: Prentice Hall PTR, 1996. Print.

[2]. Handel, Rainer, Manfred N. Huber, Stefan Schroder, and Rainer

Handel. ATM Networks: Concepts, Protocols, Applications.

Wokingham, England: Addison-Wesley Pub., 1994. Print.v

21


[3]. ATM Addresses." Microsoft TechNet: Resources for IT

Professionals. Web: 23 Dec. 2011

<http://technet.microsoft.com/en-us/library/cc976977.aspx>.

[4]. Clark, Martin P. ATM Networks: Principles and Use. Chichester,

England: Wiley/Teubner, 1996. Print.

22

mscc tns assignment ii student number 2823134 abid afsar

Documents

atm cell atm cell header

form of atm cell

atm network3

atm adaptation

atm cell structure

comparison diagram of

atm network mange data

abid afsarstudent number