Resources and Quality of ...cs778/ralf/08b-qos.pdf · KOM - Industrial Process and System...

u-darmstadt.de Fax. +49 6151 16-3052

, Dept. of Computer Science51 166151,M.tu-darmstadt.de Fax. +49 6151 166152

ogy

08B-QoS.fm 1 20.June.01

Scope

Contents

htt

p:/

/ww

w.k

om

.e-t

ech

nik

.tu

-da

rmst

adt

.de

htt

p:/

/ww

w.t

k.in

form

atik

.tu

-da

rmst

adt

.de

©R

.S

tein

me

tz,

M.

Mü

hlh

äu

ser Multimedia-Systems:

Resources andQuality of Service (QoS)

Prof. Dr.-Ing. Ralf SteinmetzProf. Dr. Max MühlhäuserMM: TU Darmstadt - Darmstadt University of Technology,

Dept. of of Computer ScienceTK - Telecooperation, Tel.+49 6151 16-3709,Alexanderstr. 6, D-64283 Darmstadt, Germany, [email protected]

RS: TU Darmstadt - Darmstadt University of Technology,Dept. of Electrical Engineering and Information Technology

KOM - Industrial Process and System Communications, Tel.+49 61Merckstr. 25, D-64283 Darmstadt, Germany, Ralf.Steinmetz@KOGMD -German National Research Center for Information Technolhttc - Hessian Telemedia Technology Competence-Center e.V

User Interfaces

.Synchro-nization

GroupCommuni-

cations

Programming

ms Communications

ice Networks

ession

Video Audio


Scope

Contents

htt

p:/

/ww

w.k

om

.e-t

ech

nik

.tu

-da

rmst

adt

.de

htt

p:/

/ww

w.t

k.in

form

atik

.tu

-da

rmst

adt

.de

©R

.S

tein

me

tz,

M.

Mü

hlh

äu

ser

Scope

Usa

ge Applications

Learning & Teaching Design

Ser

vice

s ContentProcess-

ing

Docu-ments

Security ..S

yste

ms Databases

Media-Server Operating Syste

Opt. Memories Quality of Serv

Bas

ics Computer

Archi-tectures

Compr

Image &Graphics

Animation

stems

se


Scope

Contents

htt

p:/

/ww

w.k

om

.e-t

ech

nik

.tu

-da

rmst

adt

.de

htt

p:/

/ww

w.t

k.in

form

atik

.tu

-da

rmst

adt

.de

©R

.S

tein

me

tz,

M.

Mü

hlh

äu

ser

Contents

1. Motivation

2. Characteristics of Real-time / Multimedia Sy

3. QoS - Definition

4. Resources

5. Providing QoS

Resource Management Phases

5.1 QoS Provisioning - Setup Phase

5.2 QoS Provisioning - Data Processing Pha

6. QoS Architectures

7. Conclusion

local:•harddisk

recording•interactive DVD•computer basedtraining

distributed•conferencing•video on demand•IP-Telephony

how to describe that?

emory

ing

tion

m

re


Scope

Contents

htt

p:/

/ww

w.k

om

.e-t

ech

nik

.tu

-da

rmst

adt

.de

htt

p:/

/ww

w.t

k.in

form

atik

.tu

-da

rmst

adt

.de

©R

.S

tein

me

tz,

M.

Mü

hlh

äu

ser

1. Motivation

basically, we deal with two types of systems:

Basic terminology• Resources• Realtime• Quality of Service

What and how much of it do we need and

Network

Network

MCPU

Receiv

Applica

Syste

SoftwaMemoryCPU

Sending

Application

System

Software

MemoryCPU

System

Software

em:

:


Scope

Contents

htt

p:/

/ww

w.k

om

.e-t

ech

nik

.tu

-da

rmst

adt

.de

htt

p:/

/ww

w.t

k.in

form

atik

.tu

-da

rmst

adt

.de

©R

.S

tein

me

tz,

M.

Mü

hlh

äu

ser

Motivation (cont.)

When we know about the needs, how to fulfill th• A QoS model and its implications

• QoS specification• QoS calculation• QoS enforcement

QoS has different implications in different fields• Operating system / Resource scheduling• File system organization• Compression• Communication system support• Media synchronization• ...• User Interface

timedia Systems

mputation depends notupon providing the

e processing in a given

ictable intervals

ion requests from the OS

ically or spontaneousnstraints !


Scope

Contents

htt

p:/

/ww

w.k

om

.e-t

ech

nik

.tu

-da

rmst

adt

.de

htt

p:/

/ww

w.t

k.in

form

atik

.tu

-da

rmst

adt

.de

©R

.S

tein

me

tz,

M.

Mü

hlh

äu

ser

2. Characteristics of Real-time / Mul

Real-time System:

“A system in which the correctness of a coonly on obtaining the right result, but alsoresult on time.”

Real-time Process:

“A process which delivers the results of thtime-span.”

Real-time Application - examples• Control of temperature in a chemical plant

• driven by interrupts from external devices• these interrupts occur at irregular and unpred

• Example: Control of a flight simulator• execution at periodic intervals• scheduled by timer-service which the applicat

Common characteristics:• internal and external events that occur period• correctness also depends on meeting time co

to finish an operation, e.g.

value for the useric) system failure

ut not too many deadlines are

ser

Time

ess


Scope

Contents

htt

p:/

/ww

w.k

om

.e-t

ech

nik

.tu

-da

rmst

adt

.de

htt

p:/

/ww

w.t

k.in

form

atik

.tu

-da

rmst

adt

.de

©R

.S

tein

me

tz,

M.

Mü

hlh

äu

ser

Deadlines in Realtime Systems

A deadline represents the latest acceptable timefor the presentation of a processing result

• Hard deadlines:• should never be violated• result presented too late after deadline has no• violation means severe (potentially catastroph• Example: Nuclear power plant

• Soft deadlines:• deadlines are not missed by much• in some cases the deadline may be missed, b

missed• presented result has still some value for the u• Example: train/plain arrival-departure

Start process Deadline to finish proc

hard

soft?

ation

nts

ynchronisation


Scope

Contents

htt

p:/

/ww

w.k

om

.e-t

ech

nik

.tu

-da

rmst

adt

.de

htt

p:/

/ww

w.t

k.in

form

atik

.tu

-da

rmst

adt

.de

©R

.S

tein

me

tz,

M.

Mü

hlh

äu

ser

Realtime System - Requirements

Primary goal:• deterministic behaviour according to specific

(results in a variety of requirements)

mandatory requirements:• Predictable (fast) handling of time-critical eve• Adequate schedulability• Stability under overload conditions

desirable requirements:• Multi-tasking capabilities• Short interrupt latency• Fast context switching• Control of memory management• Proper scheduling• Fine-granularity of timer services• Rich set of interprocess communication and s

mechanisms

special characteristics:

proper handlingssion / Video)

s are often not evident

eadline not met, ...)it? just "know" ...?)

ction, VRML etc.)


Scope

Contents

htt

p:/

/ww

w.k

om

.e-t

ech

nik

.tu

-da

rmst

adt

.de

htt

p:/

/ww

w.t

k.in

form

atik

.tu

-da

rmst

adt

.de

©R

.S

tein

me

tz,

M.

Mü

hlh

äu

ser

Multimedia Systems

New application area for Realtime systems with• Typically soft real-time and not (that) critical• Requirements may often be adapted to ensure

• e.g. Scalability (remember lecture on Compre

Note: when reading literature, some distinction• level of enforcement

(guarantee, best-effort, "proper" handling if d• "exception" handling (skip on to next data un

Characteristics:• Periodic processing

(increasing importance of non-periodic: intera• Large bandwidth• End-to-End Guarantees• Fault-tolerance• Fairness• Standardization

ice

("Measure"?)

ional audio):

)

r, it does so as a "service"


Scope

Contents

htt

p:/

/ww

w.k

om

.e-t

ech

nik

.tu

-da

rmst

adt

.de

htt

p:/

/ww

w.t

k.in

form

atik

.tu

-da

rmst

adt

.de

©R

.S

tein

me

tz,

M.

Mü

hlh

äu

ser

Quality of Media vs. Quality of Serv

Quality.... with respect to a Quality "Parameter"

Example Audio QoM (huge set exists in profess• Frequency Spectrum (linear amplification? ...)• Signal2Noise Ratio SNR (noise, click, ...)

Example Video QoM• spatial / temporal resolution• SNR

intuitively spoken:• QoM: something like "HiFi Audio" (16..20k Hz• QoS: something like "Hi bandwidth" (1Gbps)

but: if application delivers HiFi Audio to the use

therefore in the remainder: QoS

system according to

Transport System..

...


Scope

Contents

htt

p:/

/ww

w.k

om

.e-t

ech

nik

.tu

-da

rmst

adt

.de

htt

p:/

/ww

w.t

k.in

form

atik

.tu

-da

rmst

adt

.de

©R

.S

tein

me

tz,

M.

Mü

hlh

äu

ser

3. QoS - Definition

Quality of Service =

„well-defined and controllable behavior of aquantitatively measurable parameters“

Layer model:

Different Service Objects:• Media, Media Streams --> Packet Streams• Tasks• Memory areas

User

Application

MM System

File System Local Processing ....

......

ption


Scope

Contents

htt

p:/

/ww

w.k

om

.e-t

ech

nik

.tu

-da

rmst

adt

.de

htt

p:/

/ww

w.t

k.in

form

atik

.tu

-da

rmst

adt

.de

©R

.S

tein

me

tz,

M.

Mü

hlh

äu

ser

QoS - Layer Model

Examples: both qualitative / quantitative descri

Perception QoS• Tolerable Synchronisation Drift• Visual Perceptability

Application QoS• Media Parameters• Media (Transmission) Characteristics

System QoS• CPU Rate / Usage• Available Memory

Communication QoS• Packet Size / Rate• Bandwidth• End-to-End-Delay

Device QoS• Seek / Data Transfer Rate• Sample Rate / Resolution

rt System

System are:

ss / Reliability


Scope

Contents

htt

p:/

/ww

w.k

om

.e-t

ech

nik

.tu

-da

rmst

adt

.de

htt

p:/

/ww

w.t

k.in

form

atik

.tu

-da

rmst

adt

.de

©R

.S

tein

me

tz,

M.

Mü

hlh

äu

ser

QoS Parameters - Example Transpo

Common parameters concerning the Transport• Throughput• Delay / Jitter• Loss / Reliability

but also:• Security• Costs• Stability (Resilience)

Lo

Delay

Throughput

f one packetion (-->arrival!) timesl time,

per time interval

sesme intervally lost packets


Scope

Contents

htt

p:/

/ww

w.k

om

.e-t

ech

nik

.tu

-da

rmst

adt

.de

htt

p:/

/ww

w.t

k.in

form

atik

.tu

-da

rmst

adt

.de

©R

.S

tein

me

tz,

M.

Mü

hlh

äu

ser

Example QoS Parameters (cont.)

Delay:• Maximum end-to-end delay for transmission o• Delay jitter = maximum variance of transmiss

(math. definition: relative to "expected" arrivaNOT to arrival time of other packets)

Throughput:• Maximum long-term rate

= maximum amount of data units transmitted(e.g. packets or bytes per second)

• Maximum burst size• Maximum packet size

Loss:• Sensitivity class: ignore / indicate / correct los• Loss rate = maximum number of losses per ti• Loss size = maximum number of consecutive

l process

rst-length, ....

ropability)

n ...”


Scope

Contents

htt

p:/

/ww

w.k

om

.e-t

ech

nik

.tu

-da

rmst

adt

.de

htt

p:/

/ww

w.t

k.in

form

atik

.tu

-da

rmst

adt

.de

©R

.S

tein

me

tz,

M.

Mü

hlh

äu

ser

Service Classes

note: QoS parameters often subject to statistica

---> mean, min, max, distribution, variance, bu

Guaranteed Service• values or intervals of QoS parameters

• deterministic (at any time)• statistical (consider a time interval or certain p

QoSmin <= P <= QoSmax

Predictable Service• consider history

• from the very beginning of calculation• in a shifting time window

• “if it was like that in the last ..., you can rely o

Best Effort Service• no or just partial guarantees

icerce consumption / costs

increasingQoS qualityoo good


Scope

Contents

htt

p:/

/ww

w.k

om

.e-t

ech

nik

.tu

-da

rmst

adt

.de

htt

p:/

/ww

w.t

k.in

form

atik

.tu

-da

rmst

adt

.de

©R

.S

tein

me

tz,

M.

Mü

hlh

äu

ser

QoS Intervals

Parameter values result in• acceptable regions• inacceptable regions

of QoS

(here:) in one-dimensional intervals

note:• below required QoS level - no reasonable serv• above required QoS level - unnecessary resou

desired QoSrequired QoS

application’s needs:

QoS too bad QoS tacceptable QoS

min. QoS-Frame-Rate.

max. QoS-Frame-Rate.

oStion

640x480

Resolution (Pixel)


Scope

Contents

htt

p:/

/ww

w.k

om

.e-t

ech

nik

.tu

-da

rmst

adt

.de

htt

p:/

/ww

w.t

k.in

form

atik

.tu

-da

rmst

adt

.de

©R

.S

tein

me

tz,

M.

Mü

hlh

äu

ser

QoS intervals

also: multidimensional intervals

Unacceptable Region

min. QoS-

Acceptable

Region

max. QResoluResolution

Frame Rate

10

30

20

0

80x40


Scope

Contents

htt

p:/

/ww

w.k

om

.e-t

ech

nik

.tu

-da

rmst

adt

.de

htt

p:/

/ww

w.t

k.in

form

atik

.tu

-da

rmst

adt

.de

©R

.S

tein

me

tz,

M.

Mü

hlh

äu

ser

4. Resources

Classification

by functionality• active resources

• actively fulfill a certain task• e.g. processor, network adapter

• passive resources• provide “space”• e.g. memory, frequency spectrum, filesystem

by availability for concurrent usage• exclusive• shared

by occurence• single• multiple

Common parameter:• Capacity - allows quantitative description

hardware

in year X

danturces

2000

resources

utources

indow of Scarcity”derson et al., 1990]


Scope

Contents

htt

p:/

/ww

w.k

om

.e-t

ech

nik

.tu

-da

rmst

adt

.de

htt

p:/

/ww

w.t

k.in

form

atik

.tu

-da

rmst

adt

.de

©R

.S

tein

me

tz,

M.

Mü

hlh

äu

ser

Resources - Availability

Starting point:• scarce, but sufficient resources

Goal:• provide best service at lowest possible costs

Conclussion• need for resource management

requirements

abunreso

insufficientresources

1980 1990

interactivevideo

high-qualityaudio

networkfile access

sufficient bscarce res

“W[An

QoSafter

processing

Data out


Scope

Contents

htt

p:/

/ww

w.k

om

.e-t

ech

nik

.tu

-da

rmst

adt

.de

htt

p:/

/ww

w.t

k.in

form

atik

.tu

-da

rmst

adt

.de

©R

.S

tein

me

tz,

M.

Mü

hlh

äu

ser

Relationship: QoS - Resources

Model:

Resource with

certain capacity

Processing, using a

QoSbefore

processing

Data in

Resource SpecificInformation

Reservation

Database


Scope

Contents

htt

p:/

/ww

w.k

om

.e-t

ech

nik

.tu

-da

rmst

adt

.de

htt

p:/

/ww

w.t

k.in

form

atik

.tu

-da

rmst

adt

.de

©R

.S

tein

me

tz,

M.

Mü

hlh

äu

ser

Architecture

Resource

Scheduler

Resource

Manager

CONTROL

DATA

Resource

Monitor

resourcereservation

QoS guaranteesto user

y resource schedulinging, adaptation


Scope

Contents

htt

p:/

/ww

w.k

om

.e-t

ech

nik

.tu

-da

rmst

adt

.de

htt

p:/

/ww

w.t

k.in

form

atik

.tu

-da

rmst

adt

.de

©R

.S

tein

me

tz,

M.

Mü

hlh

äu

ser

5. Providing QoS

Resource Management Phases

user’s QoSrequirements

admission control

phase 1 (Setup):

data arrivalon streams

QoS enforcement bshaping, loss handl

phase 2 (Data processing):

rejection

negotiation

calculation

of QoSguarantees

tations

resourcereservation

QoS guaranteesto user


Scope

Contents

htt

p:/

/ww

w.k

om

.e-t

ech

nik

.tu

-da

rmst

adt

.de

htt

p:/

/ww

w.t

k.in

form

atik

.tu

-da

rmst

adt

.de

©R

.S

tein

me

tz,

M.

Mü

hlh

äu

ser

5.1 QoS Provisioning - Setup Phase

Definition of required parameters• implicit or explicit by application or user

Distribution and Negotiation

Translation between different layers• especially if they use different semantics / no

Transformation• QoS parameter => Resource requirements

Allocation and coordination of resources• along path(s) source(s) => sink(s)

user’s QoSrequirements

admission control

phase 1 (Setup):

rejection

negotiation

calculation

of QoSguarantees

User (Callee)

System (Callee)

plication (Callee)

p


Scope

Contents

htt

p:/

/ww

w.k

om

.e-t

ech

nik

.tu

-da

rmst

adt

.de

htt

p:/

/ww

w.t

k.in

form

atik

.tu

-da

rmst

adt

.de

©R

.S

tein

me

tz,

M.

Mü

hlh

äu

ser

QoS Calculation and Negotiation

Model:

User (Caller)

System (Caller)

Application (Caller) Ap

Service User

Peer-to-Peer-Relationshi

(Caller-to-Callee)

Service Provider

oS parameters(lower) value(s) on confirm

e

QoS-ValueChanged

ResponseConnect

QoSaveconfirm

eq

t3


Scope

Contents

htt

p:/

/ww

w.k

om

.e-t

ech

nik

.tu

-da

rmst

adt

.de

htt

p:/

/ww

w.t

k.in

form

atik

.tu

-da

rmst

adt

.de

©R

.S

tein

me

tz,

M.

Mü

hlh

äu

ser

QoS Negotiation

bilateral peer-to-peer• service provider may not modify requested Q• only service user at receiver side may modify

Service Provider

Caller

Peer-to-Peer

Negotiation

Calle

QoSavereq

QoSaver

ResponseConnect t4 Response

Connect t1 ResponseConnect t2

QoS-ValueRequested

can’t meet it

r-to-layer-negotiation=> heterogenity of receivers

limited target value

ered distrib. services:reduces QoS parametersoS, initator accepts/rejects" battle, see networking)


Scope

Contents

htt

p:/

/ww

w.k

om

.e-t

ech

nik

.tu

-da

rmst

adt

.de

htt

p:/

/ww

w.t

k.in

form

atik

.tu

-da

rmst

adt

.de

©R

.S

tein

me

tz,

M.

Mü

hlh

äu

ser

QoS Negotiation (cont.)

bilateral layer-to-layer• only between adjacent parts

• between local service users and providers• between sender and network

unilateral• no modification of requested QoS parameters• but just accept or reject• receiver may accept QoS parameter though it

• example: color TV broadcast

hybrid• uses unilateral mode at a certain bilateral laye

• example: broadcast/multicast communication

further:• trilateral for information exchange or: ... for a

commonly accepted for connection-oriented lay• initiator requests QoS, each entity accepts OR• final "Connect-Confirm" w/ overall minimum Q• (NOTE: "connection-oriented" vs. "flow-based

ll be available

use and new request(s) is

back” to prevent users


Scope

Contents

htt

p:/

/ww

w.k

om

.e-t

ech

nik

.tu

-da

rmst

adt

.de

htt

p:/

/ww

w.t

k.in

form

atik

.tu

-da

rmst

adt

.de

©R

.S

tein

me

tz,

M.

Mü

hlh

äu

ser

Admission Control

check, whether requested resources are and wi

especially important for shared resources:• CPU• network paths• buffer space: memory

simple rule:

check whether sum of resources already inless or equal available resource capacity

... may be applied to• availability of buffers (spatial)• bandwidth (net)

more complex: check for schedulability

note:• strong relationship with Pricing / Billing• efficient mechanisms will use “economic feed

from requesting whatever they can get

f QoS guarantees

nditions (e.g. CPU load)

reservedforappl. 1

reservedforappl. 2

time

reservedforappl. 1reservedforappl. 2

lict

time


Scope

Contents

htt

p:/

/ww

w.k

om

.e-t

ech

nik

.tu

-da

rmst

adt

.de

htt

p:/

/ww

w.t

k.in

form

atik

.tu

-da

rmst

adt

.de

©R

.S

tein

me

tz,

M.

Mü

hlh

äu

ser

Resource Reservation

Fundamental concept for reliable enforcement o• pessimistic - results in Quaranteed QoS

• optimistic - results in statistical QoS

• may use monitoring and react on overload co

unused

guaranteedQoS:

unused

needs of appl. 1

needs of appl. 2

needs of appl. 1

needs of appl. 2

statisticalQoS:

conf

ample

of aspects


Scope

Contents

htt

p:/

/ww

w.k

om

.e-t

ech

nik

.tu

-da

rmst

adt

.de

htt

p:/

/ww

w.t

k.in

form

atik

.tu

-da

rmst

adt

.de

©R

.S

tein

me

tz,

M.

Mü

hlh

äu

ser

Resource Reservation Aspects - Ex

Example: Communication System ===> variety

Reservation Model• Sender-initiated• Receiver-initiated• Explicit vs. Implicit• Out-of-Band vs. In-Band

Reservation Style• Semantics and Notation• Heterogenity and Multicast-Support

Reservation Protocols• IP V.5: ST-II• RSVP (Resource reSerVation Protocol)

sing Phase

istics of processed data)

y resource schedulingling, adaptation


Scope

Contents

htt

p:/

/ww

w.k

om

.e-t

ech

nik

.tu

-da

rmst

adt

.de

htt

p:/

/ww

w.t

k.in

form

atik

.tu

-da

rmst

adt

.de

©R

.S

tein

me

tz,

M.

Mü

hlh

äu

ser

5.2 QoS Provisioning - Data Proces

maintain resource reservations

use:• adequate traffic shaping (to ensure character• scheduling• feedback and adaption

mechanisms

note: concurrent requests !

data arrivalon streams

QoS enforcement bshaping, loss hand

phase 2 (Data processing):

ugh guarantees could be

t

after Shaping


Scope

Contents

htt

p:/

/ww

w.k

om

.e-t

ech

nik

.tu

-da

rmst

adt

.de

htt

p:/

/ww

w.t

k.in

form

atik

.tu

-da

rmst

adt

.de

©R

.S

tein

me

tz,

M.

Mü

hlh

äu

ser

Shaping

Characteristics of Multimedia Traffic• bursty (remember lecture Compression)• concurrent requests may cause problems tho

met (e.g. buffer overflow)

Basic principle

r(t)

average Cell Rate

max Cell Rate

Original Source

(r,T) shaping

rop) and possible delay

gned per connectionan r Bits

next interval (not economic)

ed (supply)

Data Capacity

onstant


Scope

Contents

htt

p:/

/ww

w.k

om

.e-t

ech

nik

.tu

-da

rmst

adt

.de

htt

p:/

/ww

w.t

k.in

form

atik

.tu

-da

rmst

adt

.de

©R

.S

tein

me

tz,

M.

Mü

hlh

äu

ser

Shaping - Leaky Bucket Algorithm,

Leaky Bucket: Bucket Size• determines maximum capacity till overflow (d

(r, T) shaping:• frames of T bits (system-wide), fraction r assi• within interval T, sender may not send more th• if "current packet" would exceed r -> wait for

Data to be transmitt

Regulation RN

c

supply

LeakyBucket

constant

pacity βs (<=β) usedmore than β+R*t tokens)

e Controled into network

cket

acity b

ts


Scope

Contents

htt

p:/

/ww

w.k

om

.e-t

ech

nik

.tu

-da

rmst

adt

.de

htt

p:/

/ww

w.t

k.in

form

atik

.tu

-da

rmst

adt

.de

©R

.S

tein

me

tz,

M.

Mü

hlh

äu

ser

Shaping: Other Algorithms

Token Bucket Algorithm• tokens drop into bucket with rate R, bucket ca• packet (="burst") size determines no. of token• effect: limited-size bursts allowed (within t, no

Token Bucket Algorithm with Leaky Bucket Rat• problem w/ token bucket: burst directly releas• therefore, put "burst" into another (leaky!) bu• --> burst drop out of leaky bucket smoothly

tokens (rate R)

data to be transmitted

token cap

limited burs

LeakyBucket

am stalls during retransmit)RC) for detection of error onlyacknowledged packets resent

erroneous Xmit)r packets until reXmit)sonable" no. of packets)solution" for multimedia)undancy for correction!f FEC and CRC

esentation!i-speed LANsice-....: re-buffer after pause


Scope

Contents

htt

p:/

/ww

w.k

om

.e-t

ech

nik

.tu

-da

rmst

adt

.de

htt

p:/

/ww

w.t

k.in

form

atik

.tu

-da

rmst

adt

.de

©R

.S

tein

me

tz,

M.

Mü

hlh

äu

ser

Loss Handling

Error Detection• by means of redundancy / checks / analysis

Loss Handling

2 basic categories:• (partial) Retransmission (problem: media stre

• in-packet redundancy (cyclic redund. check C• automatic repeat request ARQ: non (or neg.)• three facets:• Go-back-N (error -> "reset" link to state before• Selective Retransmission (error: buffer furthe• Using partially error-free streams (reXmit "rea

• Prevention (formerly considered "only viable• Forward Error Correction (FEC): in-packet red• Priority Coding: --> mix of FEC "degrees" or o

• Multimedia-proof retransmission:• Slack ARQ: buffer received packets before pr• buffer time long enough to support reXmit in h• for, e.g., voice streams of type voice-pause-vo

esources

ctions to reduce generated

nder to slow down

o sender

Monitor/Decode


Scope

Contents

htt

p:/

/ww

w.k

om

.e-t

ech

nik

.tu

-da

rmst

adt

.de

htt

p:/

/ww

w.t

k.in

form

atik

.tu

-da

rmst

adt

.de

©R

.S

tein

me

tz,

M.

Mü

hlh

äu

ser

Adaption - Feedback Control

Monitor load of network and local end-system r

If significant changes occur, take appropriate aload

• Explicit communication – receiver informs se• Completely in network on a hop-by-hop basis• By feedback from congested network nodes t

Variety of possible reactions• e.g. Layered transmission• Degredation, ...

Code/ScaleLess/More

Network

ed handling of Flows in

ort heterogenous needs

vel Agreements and ensuredescribed

/ dedicated treatment of flows


Scope

Contents

htt

p:/

/ww

w.k

om

.e-t

ech

nik

.tu

-da

rmst

adt

.de

htt

p:/

/ww

w.t

k.in

form

atik

.tu

-da

rmst

adt

.de

©R

.S

tein

me

tz,

M.

Mü

hlh

äu

ser

6. QoS Architectures

Examples (Communication Layer)

• Heidelberg Transport System (HeiTS)• uses ST-II (IPv5)

• Internet Integrated Services• use existing infrastructure, but deploy dedicat

Transfer System• Resource Reservation Protocol RSVP to supp

• Differentiated Service• Granularity based on TOS IP Header Field• Define Service Classes, Negotiate Service Le

dedicated treatment of Flows that behave as

• IPv6• QoS support as one design criteria• dedicated header fields to allow classification

ovisioning in 2 phases:

aling ...)


Scope

Contents

htt

p:/

/ww

w.k

om

.e-t

ech

nik

.tu

-da

rmst

adt

.de

htt

p:/

/ww

w.t

k.in

form

atik

.tu

-da

rmst

adt

.de

©R

.S

tein

me

tz,

M.

Mü

hlh

äu

ser

7. Conclusion

Realtime- and Multimedia Systems

Quality of Service - Definition and Concepts

Resources and Resource Management / QoS pr• QoS specification, calculation and negotiation

• Requirements of the application• Functions to calculate QoS guarantees• Guarantees returned by the system• Reservation of resource capacities

• QoS enforcement:• Scheduling of resource access• Monitoring and adequate actions (shaping, sc

s, netowork

)) packetsicaste in full resolutions periodically

receiver 1

receiver 2

receiver 1

receiver 2


Scope

Contents

htt

p:/

/ww

w.k

om

.e-t

ech

nik

.tu

-da

rmst

adt

.de

htt

p:/

/ww

w.t

k.in

form

atik

.tu

-da

rmst

adt

.de

©R

.S

tein

me

tz,

M.

Mü

hlh

äu

ser

Outlook: Communication Protocols

Reservation / QoS initiated by: sender, receiver

example RSVP: receiver-initiated• sender sets up paths (requested by receivers?• receivers periodically send reservation (RSVP• paths (~flows) may, e.g., represent video mult• receivers might not be able to present / receiv• receivers may just drop video -> RSVP packet•

Internet(Multicast)

sender 1

data (session)PATH

RESV

RSVP

RSVP

RSVPInternet

(Multicast)

sender 1

data (session)PATH

RESV

RSVPRSVP

RSVPRSVP

RSVPRSVP

es (cf. chapter MM sync.)

ion


Scope

Contents

htt

p:/

/ww

w.k

om

.e-t

ech

nik

.tu

-da

rmst

adt

.de

htt

p:/

/ww

w.t

k.in

form

atik

.tu

-da

rmst

adt

.de

©R

.S

tein

me

tz,

M.

Mü

hlh

äu

ser

QoS vs. Human Perception

Rule-of-Thumb: Eye integrates, Ear differenciat

--> tolerant visual perception 1: overlay separat

--> tolerant visual perception 2: completion

Resources and Quality of ...cs778/ralf/08b-qos.pdf · KOM - Industrial Process and System...

Documents

Transcript of Resources and Quality of ...cs778/ralf/08b-qos.pdf · KOM - Industrial Process and System...