Saad Haj Bakry, PhD, CEng, FIEE 1 Performance Evaluations Saad Haj Bakry, PhD, CEng, FIEE P...

Saad Haj Bakry, PhD, CEng, FIEE

1

Performance EvaluationsSaad Haj Bakry, PhD, CEng, FIEE

PRESENTATIONS IN NETWORK MANAGEMENTPRESENTATIONS IN NETWORK MANAGEMENT

Saad Haj Bakry, PhD, CEng, FIEE 2

Objectives / Contents

Service Measures

Delay: Store & Forward

Congestion: Circuit Switching

Performance Evaluations


Service Measures

Faults

Information: Loss Security Compression

Quantitative / Qualitative

Congestion

Delay

Processing



Measures: Q & QMeasures Description

Performance Technology Capabilities. User Satisfaction Natural Feel

Quantitative

Parameters

Clearly Defined (Mathematically) Evaluated Numerically

Qualitative Parameters

Like and Dislike. Ease of Use. Social and Behavioural Factors.



Measures: Faults (1/3)

Measure DescriptionMTBF Mean Time Between Failures

MTTR Mean Time to Repair

Availability

(should be 99%)

The proportion of time when the system is available for use

MTTRMTBF

MTBFtyAvailabili




15

25

40

20

0 10 20 30 40 50

Fault Type 1

Fault Type 2

Fault Type 3

Fault Type 4

Frequency distribution of 100 mixed faults associated with 4 types (Measure of “ Strengths & Weaknesses” of Components)




Weakness DescriptionLogical Deficiency Lack of resources to performing the

operations correctly.

e.g. Message Reassembly Space in Virtual Circuit Operations

Protocol

Un-Robustness

Lack of “built-in” “fault-tolerant” capability to deal with components

failures and stress conditions

e.g. Routing Problem : Circulation of Packets.



Measures: Congestion

Measure DescriptionNOS Number of Successful Attempts

NOF Number of Failed Attempts

Congestion

Service Levels

NOFNOS

NOFCongestion

NOFNOS

NOSService



Measures: DelayMeasure Description

Elements(Point-to-Point)

Processing /Queuing /

Transmission / Propagation.

End-to-End Source to Destination Delay

(from Sending to Receiving)

Jitter Deviation from Average

Synchronization Audio-Video “Lip Synchronization”

Delay Sensitivity Audio & Video (Online) Streams



Measures: Processing

Measure Description[i] Instruction type index

T[i] Processing time of instruction [i]

F[i] Relative frequency of instruction [i] in the application considered

T Average processing time per instruction

F[i].T[i]T



Measure Description

Loss of Information

Signal-to- Noise Ratio. Signal-to-Interference Ratio. BER: Bit Error Rate. Cell-Loss Rate Jamming: Loss of Communications

Loss Sensitivity

Data (Text) Streams.

Measures: Information (Loss)



Measure Description

Integrity Information: Loss Destruction Modification

Confidentiality Unauthorized “Disclosure” of Information: “Encryption / Attack”

Blocking “Denial” of Service

Measures: Information (Security)



Measures: Information (Compression)

Measure Description

Video PCM (BW: 4.2 MHz).(Sampling: 2). (Sample:16 bits)

= 135 Mbps [Compressed to 45 Mbps]

Digital Video (Pixel: 24 bits).(SVGA: 800 x 600 pixels).

(Frames: 25 per sec) = 288 Mbps

Compression TV Quality = 4 - 9 Mbps Cable TV Quality = 2 - 4 Mbps Low Rate Videoconferencing = 384 kbps – 1.5 Mbps

“Ratio” Ratio = Encoded Size / Compressed Size



PRINCIPLES

ERLANG-B FORMULA

OPERATION TRAFFIC

Congestion: Circuit Switching



OBJECTIVE: Enabling

Sub channels to be Assigned to Users

“Dynamically” on Demand (Not on Fixed Basis)

USE: Suitable for Burst / Random Use

CONCEPT: Sub channels

Assigned on Demand for Active Use and

Released when Activity is Completed

Principles (1/2)



TDM / FDM

CIRCUIT

SWITCHING

USERS

Users Generating Demands

Dynamic Assignment / Release on Demand

“N” Sub Channels

Channel Sharing

Shared

Channel

Principles (2/2)



1. DIAL-UP

3. CALL PROGRESS

4. CALL TERMINATION

2. SIGNALLING / ROUTING / ASSIGNMENT

5. RELEASE

Operations



TWO RANDOM PROCESSES

CALL ARRIVALS: Random Distribution (Poisson Process)

CALL DURATION: Random

Distribution (Negative Exponential Distribution / Related to Poisson Process)

Traffic (1/3)Performance Evaluations


R [Calls / Time Unit]: Rate of Generated

Calls

D [Time Unit]: Average Call Duration

A [Erlang]: A = R.D

BUSY HOUR PRINCIPLE

ERLANG:

“1” Erlang is Full Channel

Occupancy For “1” Time Unit

Traffic (1/3)



“1” ERLANGR =

1 [Calls / Hour]

D =

60 [Minutes]

A = 1 [Erlang]

R =

4 [Calls / Hour]

D =

15 [Minutes]

A = 1 [Erlang]

R =

12 [Calls / Hour]

D =

5 [Minutes]

A = 1 [Erlang]

Traffic (3/3)



TYPICAL / SIMPLE CASE STUDY

SYSTEM: “N” (Sub)

Channels Fully

Available to All Call

DEMANDS / TRAFFIC

OFFERED BY

ALL USERS: “A”

[Erlang]

PERFORMANCE

/ GRADE OF

SERVICE /

BLOCKING

PROBABILITY “B”

Erlang “B” Formula (1/4)Performance Evaluations


B = (AN / N!) /

i 0

i N

(Ai / i!)

B = 1 /

i 0

i N

(N! / (Ai (N - i)!))

Erlang “B” Formula (2/4)



OTHER IMPORTANT FACTORS

TRAFFIC CARRIED /

SERVICED:

K = A (1 - B)

AVERAGE CHANNEL

UTILIZATION /

OCCUPANCY:

Q = K / N




POSSIBLE USE

SYSTEM

EVALUATION:

Given: N / A Find:

B / K / Q

SYSTEM

CAPACITY:

Given: N / B Find:

A / K / Q

SYSTEM

DESIGN:

Given: A / B / K

Find: N / Q




PRINCIPLES

OPERATION

TRAFFIC

DELAY ANALYSIS

MESSAGES: • Packets• Frames• Cells

(Switching / Relay)

Delay: Store & Forward



1

+I

2

N

I

I

P M MSHARED

CHANNEL

BUFFERPROCESSOR

STORE & FORWARDc

c

c [bps]

c

C [bps]

Dynamic Channel Assignment (Active Users Only) / Efficiency

USERS > N Where N = C/c

Principles (1/2)



BURST USE USE

LOSS SENSITIVE

INFORMATION:

“DATA / TEXT”

NO DELAY

SENSITIVE

INFORMATION:

“VOICE / PICTURE”;

EXCEPT IN HIGH

SPEED

Principles (2/2)



MESSAGE:

•An Information Signal Sent by a Single User

•Physical Block

•(Basic Name: for M / P / F / C)

PROBLEM:

•Fluctuating Size

•Need for Size Control “P / F / C” (Logical Units)

•Providing Better Sharing

Messages (1/4)



PACKET: X.25 / 64 kbps Variable Size

H: 8 bytes

FRAME: T-1 / E-1

Variable Size H: 2 bytes

INFORMATION HEADER

HEADER: SOURCE / DESTINATION / CONTROL

INFORMATION: CONTROLLED SIZE

CELL / ATM: OC-3 / OC-12 Fixed: 48 Bytes

H: 5 bytes

Messages (2/4)Performance Evaluations


DATAGRAM:

Logical Units (Packets) are

Routed Independently Through the

Network from Source to

Destination

VIRTUAL CIRCUIT: Physical Units

(Messages) Sent from Source to Destination Look as if they Passed

Through a Circuit Example: DATAGRAM with the Packets of a

Message Reassembled at Destination

Messages (3/4)



PACKET: Point-to- Point

& End-to-

End

FRAME: End-to-End

Only

ERROR

CONTROLCELL / ATM: End-to-End

(Header Only)

LOW NOISE: Eases Error Control Protocols.

HIGHER SPEED: Reduces Delay and Helps Information Integration (Data / Voice / Picture)

Messages (4/4)Performance Evaluations


P M M

M [bits]

NEXT

NODE

NEXT

NODE

DELAY ELEMENTS

PROCESSING

DELAY “p”

QUEUING

DELAY “q”

TRANSMISSION

DELAY “s”

PROPAGATION

DELAY “g”

p q s g

MESSAGE DELAY: d = p + q + s + gd = p + q + s + g

C [bps]

l [km]v [km/s] /

Sec.Sec.

Operation (1/3)



PROCESSING DELAY: Dependent on Processing

Independent of Traffic

QUEUING DELAY: Dependent on

Traffic (Drive) / Capacity (System)

Analysis Required

TRANSMISSION DELAY: s = M / C Dependent on Message /

Capacity (System) Independent of Traffic Volume / Fluctuation

PROPAGATION DELAY: g = l / v Dependent on Channel /

Distance (Geography) Independent of

Traffic / Capacity

Operation (2/3)



PROCESSING DELAY: Significant in High Speed

Links

QUEUING DELAY: An Essential Element, as it is Associated with the Capacity

/ “System”, and Traffic Volume / Fluctuation /

“Demands”

TRANSMISSION DELAY: An Essential Element, as it is

Associated with the Capacity / “System” , and the Message

Length / “Demands”

PROPAGATION DELAY: Significant in Satellites

g = 36 / 300 = 0.12 sec

Operation (3/3)



TWO RANDOM PROCESSES

MESSAGE

ARRIVALS:

Poisson Process

MESSAGE LENGTH: Negative Exponential

Distribution / Fixed Size Messages

(Deterministic)

Traffic (1/2)



R [Messages / Sec]:

Rate of Generated Messages

M [Bits]: Average / Fixed Message Length

BUSY HOUR PRINCIPLE

TRAFFIC RATE: A [bps] = R . M

Traffic (2/2)



QUEUING DELAY:

Variable Message Length qv = (RM / C) /

( (C/M) - R)

Fixed Message Length qf = (1/2) . qv

Delay Analysis (1/4)



ESSENTIAL DELAY ELEMENTS:

d = qv + s = 1 / ( (C/M) - R)

LIMITATION: RM < C

UTILIZATION / OCCUPANCY: U = (RM) / C




D: NORMALIZED DELAY:

(MESSAGE TRANSMISSION TIME “s”) IN

TERMS OF UTILIZATION “U”:

D = d / s = 1 / (1 - U) D [Unit-less]: Number of Messages in

the System (queued & transmitted)




POSSIBLE USE

SYSTEM EVALUATION:

Given: C / M / R Find: d / U / D

SYSTEM CAPACITY:

Given: C / U (d/D) / M Find: R

SYSTEM DESIGN: Given: R / M / U Find: C




PERRFORMANCE COMPUTATIONS:

Congestion / Delay

Conclusions

PERRFORMANCE UDERSTANDING:

Q&Q / Faults /

Congestion /

Delay / Processing / Information

PERRFORMANCE MONITORING /

MANAGEMENT



References

Telecommunications Management: Operation & Management of Networks, National Computing Centre (NCC) Training, UK.

David Etheridge and Errol Simon, Information Networks: Planning and Design, Prentice Hall, UK.

Gruber J.J., Transmission Performance Of Evolving Telecommunications Networks, Artech House, Boston-London, 1992.


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