Quality of service parameters in atm

8/12/2019 Quality of service parameters in atm

1/26

Traffic control in ATM networks

Andrea BiancoTelecommunication Network Group

[email protected]://www.telematica.polito.it/

Andrea Bianco TNG group - olitecnico di Torino QoS Issues in Telecommunication Networks - 1

!"# in AT$ Networks

Layered model

1 %sed for traffic characteri&ation and !o# definition

2 'all le(el

t

) Burst

t

) 'ell

t



2/26

Call level

1*on

g-ter m

temporald+namics

2

The tr af f ic occupies

networ k

r esour ces f or the f ull call dur ation

3Traff

icchar acter i&a

tion 'allattri,ut

es 'allmodel

4!ual

it+ofser(ice

Andrea Bianco TNGgroup - olitecnico di

Torino

QoS Issues inTelecommunicationNetworks -

!urstlevel

1$edi

um

-ter mtemporald+namics

2"N-

"

per iods

"N

"##

! $

! M

%

1Traffi

ccharacteri&ation: "

periodsstochasticduration

Burstlengthstochasticdu

ration

Bitratedur ing"N

per iods

peakrateassumed

2!uali

t+ofser (ic

eundefined

Andrea Bianco TNGgroup - olitecnico di

Torino

QoS Issues inTelecommunicationNetworks - &

Call level

1'all

attri,utes T+pe ofre0uest

ondemand1per manent1semi-per manent

'onfigur ation

point-to-point1multipoint1,roadcast

Num,er ofconnectionsopened

inthetwodirections

2' /2''

Traf ficcontractelement foreachconnection

#ignalingprotocol

used atnetwor kingr ess

#upplementar +ser

(ice

s2Traffic

char acteri&ation 'allarri(alprocess stochasticdescription

'alldur ation stochasticdescription

3!ualit+

ofser(ice 'ontrolplane

1

ost-selection dela+

2

Ans

wer ing signaldela+

3

'onnec

tion closing de


3/26

la+

o

int-to-point,lockingpr o,a,ilit+

Andrea Bianco TNG group -

olitecnico di Torino

QoS Issues inTelecommunicationNetworks - '

!urstlevel

) Burstiness:

3)

Acti(it+coef ficient:

4

)

A(er age

,itrate:

BM 4 B

P

) Bit

rate

(ariance:

5 6B4B

M (B

P -BM )



QoS Issues inTelecommunicationNetworks - (

ag. 3


4/26

Cell level

1 Traffic characteri&ation: 7nter-arri(al time distri,ution 8istri,ution of the num,er of cells generated in a

measurement period T "ften less information is accepted also for comple9it+ reasons

1 7nter-arri(al e9pected (alue and (ariance2 rom the a(erage inter -arri(al time the a(erage ,it -rate can ,ecomputed

2 !ualit+ of ser(ice: relia,ilit+

1 'ell loss pro,a,ilit+2 'ell error pro,a,ilit+3 'ell mis-insertion pro,a,ilit+ cells ,elonging to other

2' erroneousl+ inserted in the current 2' 9pected (alue1 (ariance and ma9imum cell dela+

Andrea Bianco TNG group - olitecnico di Torino QoS Issues in Telecommunication Networks - )

!"# in AT$ Networks

Standard

1 A traffic contract was defined Traffic characteri&ation

1 Accurate

2 %ni0uel+ (erifia,le

3 #imple1 to ,e useful for the computation ofnetwork resources that should ,e allocated tot theconnection

!o# guarantee

4 arameters defined in the7T%-T 7.;


5/26

atio

n

17den

tification

ofcellflowswithinaconnection

2

8efinitionoftrafficintrinsicparameter

s

Tr af f ic nominal char acter

istics

in

a,sence of inter f er

ing tr af f ic

3

Toler ance: a

ccepted (ar i

ations

w

ith r e

spectto nomi

nalchar acter

istics

'82T:'ell8ela+2ariationTolerance

4 'onf ormancedefinition G'>Aalgorithm

Generic'ell>at

e Algorit

hm

Andrea Bianco TNGgroup - olitecnico diTorino

QoS Issues inTelecommunicationNetworks - .

Stan

dard

+

traffi

c

c,ar

acter

i ati

on

1

'ell f lows gener ated ,+ th

e user 1 e9cluding "

A$ e >$

ce

lls gener ated ,+ switches

it

isthesetofcellswhoseconf or ma

nc

etothenominalpar ameterwill,e(eri

fied

: Aggr egatedflow

8atacellflow

no>$and"A$

?ighprior it+datacellflow

'*4

"A$cell

flow >$cellflow

8ata

"A$cellflow

?ighprior

it+datacell

'*4

"A$flow

Andrea Bianco TNGgroup - olitecnico diTorino

QoS Issues inTelecommunicationNetworks - 1/

Standa

rd+

traffic

c,aracte

ri ation

18e

f in

i

tion oftr af f ic in

tr ins

i

c par ameter s

'>

eak'e

ll>ate

17n(er

#'>

#

ustaini,le'ell>ate

27n(er

se

ofthea(erageinter-

arri(al

timeamongtwoad acentcells

7BT

7ntrinsicBur st

T

oler ance


6/26

3$a9imu

maheadtimeforwhicha cellcan,etransmittedwithrespect tothenominalarri(altimedeter mined,+ the#'>(alue

$B#

$a9imumBurst#i&

e4$a9im

umsi&eof acell,urst1agroupofcellsthatcan,etransmitted at

'>

5$B# 4

3 7BT/

3/#'>-3/ '>

67BT4

$B#-3

3/#'>-3/ '>

AndreaBianco TNGgroup -

olitecnico

di Torino

QoSIssues inTelecommunicationNetworks- 11

tandard+

traffic

c,ara

cteri

ation

10$CM!S num3er of cells4

cell0s4

tConnection

duration

Connection Connectionstartin5 time endin5 time

SC 6 num3er of cells0 connectionduration

Andrea Bianco TNG group - olitecnico diTorino

QoS Issues in TelecommunicationNetworks - 12

ag. 6


7/26

elation 3etween SC and I!T

>eal arri(al process 7BT

t

3/#'>t

7deal arri(al process at #'>1 used as a reference


QoS Issues in TelecommunicationNetworks - 1

!"# in AT$ Networks

7C A+7eneric Cell ate Al5orit,m

1 #tandard algorithm for conformance

(erification policing and for traffic adaptationshaping

2 A>A$ T >#: T 4 nominal cell inter-arri(al time C 4 tolerance or ma9imum accepted (ariation with

respect to nominal spacing

3 2A>7AB* #: T a 4 real cell arri(al time TAT4 theoretical cell arri(al time

Andrea Bianco TNG group - olitecnico di Torino QoS Issues in Telecommunication Networks - 1'


8/26

7C A

al5o

rit,

m+

flow

dia5

ram

A cell arrives atTa

Non conformantcell

8ossi3lemarkin54

Andrea Bianco TNG group - olitecnico di Torino

Conf or man

ceverification

1#ta

ti

sticalmultiple9ingsta

ge

s

switchingnodes

modif

+ the or iginal tr af

f i

c patter n due to

unpr

edicta,le0ueuingdel

a+

s

'ell8ela+2ariationToler ance

o(er#'>and/or

'>

2'82

T

$a9i

mum accepta,le ahead time at an int

er f ace with r espect to the

e9pected ar r i(altime

#imilarto7BT1,ut

tocopewithmultiple9ingdela+s1nottoallowsome(ar ia,ilit+intheuserflow

3 7fG'>

A ischeckingthe

'>


9/26

) 7f G'>A is checking #'> T43/#'> C4 7BT '82T #'>


QoS Issues in TelecommunicationNetworks - 1(

Qualityofservice+

standardIT9-TI: &(

1

'

T8

'ell Tr ansf e

r 8ela+

A(er age

time,etweenthetr ansmissionofth

2

6-pt '

82

Two point 'ell8ela+ 2ar iation

2ar iationofcell

deli(er +

time

8if f e

r e

nce

,etween the 3

-

D

inf er iorand super ior0uantile of'T8

3

'*>

'ell

*oss >at

io

'elllos

spr o,a,ilit+

>a

tio,etweenlostcellsandtr ansm

ittedcells

'*>

e'*>

3

AndreaBianco TNG group -

olitecnico di

Torino

QoS IssuesinTelecommunicationNetworks -1)

Qualityof service+

standard

IT9-T I: &(

1

'

>

'ell

r r or

>ate

>atio,etweencellswithde

tectede

r r or sa

ndthetot

a

lnum,erofcells

2

'$>

'ell $isin

ser tion >ate

>atio,e


10/26

tweener r o

neousl+r ecei(

to other2

's

and the to

talnum,er

ofr ecei(edcells

3#

'B>

#e(er el+

rr or ed'

ellBlock>atio


olitecnico di

Torino

QoS IssuesinTelecommunicationNetworks -1*

ag . ;


11/26

Quality of service classes

1 8efined through some parameters: '*> '82

2 E !"# ser(ice classes standardi&ed ,+7T%-T to satisf+ E main t+pes of user ser(ices: 'lass 3: #T>7'T '821 '*> 3

'lass 6: T"* >ANT '*> 3 'lass ;: *7$7T 8 '*> 'lass %: B #T ">T does not admit

negotiation of an+ parameter

Andrea Bianco TNG group - olitecnico di Torino QoS Issues in Telecommunication Networks - 1.

!"# in AT$ Networks

Transfer modes

1 7T%-T: international l+ recogni&edstandardi&ation ,od+

2 AT$ forum: de-facto standardi&ation ,od+

3 Transfer modes defined B+ 7T%-T as AT' AT$ Transfer 'apa,ilit+ B+ AT$ orum as #er(ice 'lass

4 Transfer mode distinguished through definition of: 'ell flows to which guarantees are pro(ided arameters to characteri&e flows 'onformance (erification applied to flows Adopted control functions

Andrea Bianco TNG group - olitecnico di Torino QoS Issues in Telecommunication Networks - 2/


12/26

Transf ermodes

18o

no

tdefine!o#re0uirements

ac

h tr ansf er mode ca

n ,e ass

ocia

ted

almost

to an+ negotia,le !o#

2i(emaintransf ermodes:: 'B>/8B>:'onstant/8eter

ministic

Bit>ate

2B>/#B>:2

ar ia,le/#t

atisticalBit>ate

%B>:%nspecifi

edBit>ate

AB>:

A(aila,leBit>ate

ABT:

AT

$Block

Tr ansfer

3

ABT ed

AB> use >$ cells to contr ol f low cel

l e

mission r ate



QoS Issues inTelecommunicationNetworks - 21

Trans

fermodes

1

8ef in

e

AT$ la+er

se

r (ices an

d the a

sso

ciated !o# 2

Toeach ser (

ice1a set

ofadmis

si,

le !o# par ameter s (a

lu

es is def


13/26

ined

3

Net

wor koper

ator sma+addother!"#

parameter(alues,e+ondthe

standardi&edones



QoS Issues inTelecommunicationNetworks - 22

Transf ermodes+;!

1 '

har acter i&ati

on:

'

>o(e

raggregatedflow

data"A$>$

or

'>o(erdata

"A$flow

8oesnotusethe'*

,it

2

"f f er s sta

ti

c ,it r ate e0u

a

l to the negotia

ted

'>

3

7sochr onous se

r

(ices or f i9ed ,

it r ate

se

r (ices

4

' A' o

(

er B

5

Associated with

se

r (ice class 3


olitecnico di

Torino

QoSIssues inTelecommunicationNetworks - 2

Transf

ermodes +S!

1

'har acter i&ation

; f la(or

: #B>3:

'>1#'>and$B#

o(eraggregatedflow

#

#B>;:like#B>61,uttagging ofnoncon

for mantcells isadmitted

2

"f f er a (

ar ia,

le ,it r ate1 nor mall+ r anging

,etween

'> e #'>

to satisf + sour ce needs

1 not networ k nee

ds

3

Alwa+s two instances of G

'> A ar e used

4

7so

chr onous ser (ice or data s

er (ices with

(ar ia,le ,itr ate

5 '

A' o(er B

1B$1Be

0

or e9ploiting measur ements

Allocated,andwidthmust,eg

uar anteedthr oug

hapr operschedulingalgorithm

6

T+picall+1los

s r ate and dela+s ar e negotiated


olitecnico di

Torino

QoSIssues inTelecommunicationNetworks- 2'


14/26

a g. E


15/26

Transfer modes+ 9!

1 #tandardi&ed onl+ ,+ AT$ orum 7T%-T: %B> can ,e o,tained as 8B> with % class of ser(ice

2 'haracteri&ation: '> o(er aggregated flow

3 No conformance definition

4 No ,it rate allocation1 no !o# guarantees on dela+sand loss pro,a,ilities

5 #witches e9ploit cell discarding techni0ues To reduce segmentation negati(e effects

1 $ore losses2 F%seless traffic transported

*oss priorit+ in ,uffers

Andrea Bianco TNG group - olitecnico di Torino QoS Issues in Telecommunication Networks - 2&

!"# in AT$ Networks

9! + cell discardin5

1 #electi(e 'ell 8iscarding: 8rop cells ,elonging to a higher la+er packet/message

for which at least another cell was alread+ dropped #ome Fuseless traffic due to head of packets alread+

transmitted cells2 arl+ acket 8iscarding:

8iscard full messages entire set of cells when the,uffer occupanc+ e9ceeds a gi(en threshold

?igher la+er packets segmented in cells are eitherentirel+ transferred or dropped1

1 Hhen the ,uffer occupanc+ e9ceeds the threshold1cells ,elonging to packets alread+ partiall+ transmitted are storedand later transmitted1 cells ,elonging to new packets are dropped

Andrea Bianco TNG group - olitecnico di Torino QoS Issues in Telecommunication Networks - 2(


16/26

"t,ercelldiscar din5me

c,anisms

1%se

ofth

e

'7,itinthecel

lheader

Tfield:

%sed to indic

ate congestion to pr otocol l

a+er s

higher th

an

A

T$

7t is assumed that higher la+er

pr otocols

r eact

to conges

tion

signals

2'ell

discarding,a

sedonpriorit+:

7f,uf f ersi&e occupanc+ ,ecomes

cr itical

e.g.:

f ull,uff eror,uff eroccupanc+o(erthr eshold

low

priorit+cells

'*

43

ar ediscar ded

8i(idedintwocategories:

1

r otecti(e

f ullsepar ation ,etwee

n high

andlow priorit+

2

Nonpr ote

cti(e


olitecnico di TorinoQoS Issues inTelecommunicationNetworks - 2)

Tra

nsf ermodes+A!

1

AB>A

(aila,leBit>ateoff er sanallocat

ed,itrate,etween

'>and

$'>


17/26

dependingonnetw

or kresour cesa(aila,ilit+Igoals

ull,itrateutili&ation

airresour cepar titioning

2

The ne

twor ke9p

licitl+signals

tosour cesthe

tr ansmission,

itr at

e

3

7tpr o

(ide small'*>

ideall+ &er o '*>

i

fsou

r ce adapttheir r ate to networ k

indication



QoS Issues inTelecommunicationNetworks - 2*

Transf ermodes+A!

1

'har acter i&ation:

'>o(eraggr egate

flow

data"

A$

>$

>$

2 '

onf or mance

def inition ,a

sed on G'>

A with pa

r am

eter T adapte

d to networ k signals

3

#ou

r ce ,eh

a(i

or completel+

specif ied in standar ds

4

Node al

gori

thms1asusual1notstandar di&ed


olitecnico

di Torino

QoS IssuesinTelecommunicationNetworks -2.


18/26

Transf

ermodes+ A!

1

%ses in-

,and >$ cells

f or war d e ,ackwar d

to o,tain

a contin

uo

us

contr olofsour ce emissio

n ,itr ate

c

ooper a

ting sou

r c

es

#: generates>$

cells

M M M8:retransmits

S ;N1 Ni Nk recei(ed >$

cellsNi: reads

andwrites >$cells

Andrea Bianco TNG group - olitecnico di Torino QoS Issues in Telecommunication Networks - /

a g.


19/26

A! + source 3e,avior

1 An AB> source #tarts transmission at a negotiated rate 7'> eriodicall+ inserts >$ forward cells in cell flow Hhen it recei(es an >$ ,ackward cell it adapts

the transmission rate to the minimum (aluecontained in the cell

7f no >$ ,ackward cells are recei(ed1 the source

slows down until it stops 7t the source is silent more than a gi(en period1 i t

starts transmitting at the negotiated rate


!"# in AT$ Networks

A! + node 3e,avior

1 Three possi,ilit+ to control source emission rate: '7 9plicit orward 'ongestion 7ndication :

1 0ui(alent to the congestion notification used in framerela+

2 3 control ,it to signal congestion

3 7t is the simplest ,ut less efficient mechanism

4 8estination translate '7 ,its into a '7 ,it in,ackward >$ cells

>>$ >elati(e >ate $arking : nodes send on ,ackward>$ cell a ternar+ information through two ,its '71N7setting increase rate1 keep rate1 decrease rate

> 9plicit >ate : nodes send on ,ackward >$ cells therate at which a source can send cells



20/26


21/26

ease

1'7

'ongestio

n7ndicati

on

,its

4'>:

9

plicit'ell>ate

5

'' >:'ur rent'ell>ate

6$'

>:$inimum'ell>ate

7J.



QoS Issues inTelecommunicationNetworks - '

A! +some8arameter s

1

ar ameter

s negotia

ted when opening th

e 2'

2

'>:

eak 'ell

>ate

3

$'>: $

inimu

m 'ell >ate

4 7

'>: 7n

itial'ell>ate

#ourcestartsen

dingat7'>.>anges,etween

'>and$'>

5

>7

: >at

e 7ncr ease

actor

Negati(epower of61referringto

'>

6

>8

: >ate

8ecr ease

actor

Negati(epower of61referringto''>

7

TB

: Tr ansie

nt Buf f er

9

posur e

Amountof

datathatcan,etr a


olitecnic

o di Torino

QoSIssues inTelecommunicationNetworks- &

A! + M

1 T

wo contr ol,it

s: CI

'ongestion7ndication

NI

Not

7ncrease

CI

/

/

1

) Two parameters8ecr ea

se/7ncr ease

actor

1

To incr ease r ate: ''>4''>

'>K>7

2

To decr

ease r ate: ''>4''>K

3->8

3

Nodes cannot f lip to

a ,it

set to 3 ,+ other nodesL

AndreaBianco TNG

group -olitecnico di

Torino

QoSIssues inTelecommunicationNetworks- (

a g. =


22/26

A! + e


23/26

A! += ICA

) "nce the target ,it rate is set1 e.g.> T4 .O< '

stimate

The num,er of acti(e AB> connections

N AB>

Background traffic * AB> i connection current load *

'ompute:

A(aila,le ,it rate for : B B

#4 B

AB>/ N

AB>

* 4P*

r

a

n

s

f

e

r

m

o

d

e

s

+

A

!

T

A

T

M

!

l

o

ck

Transfer4

1

2

a ,

lock of

cells as a gr oup of cells Fenclosed

,+

two

>$ cells

orpr

eceded ,+ one

>$ cell


24/26

B2'i

4 B AB>

K* AB>i

/* AB>

B #i 4ma9 QB # 1 B2'i R

The ma9imum allows to target a ma9-min fair allocation


25/26

!9 ST M

)B#i

iswr itteninthe

>fieldonl+ifsmallerthanthecurrent(alue

Andr eaBianco TNGgroup -

olitecnico diTorin

o

QoSIssues inTelecommunicationNetworks- .

12a

r ia,le ,it-r ate ser (ice wit

h f astr esour ce

2'

ell

s a

co

And


26/26

A!T+ATM!lockTransf er

1

'h ar acteri&ation:

B'>1sending ratefor the,lockof cells

2

Bandaallocat

el

,u

>

2achnodeeitherdiscar d oracceptthe full,lock

Ratherinefficientwhencrossinseveral nodes

39ploits

part ofthea(aila,

le,andwidth forshortperiods

4 Accepta

ncecan ,edonelookingat ,i trateonl+1 at,ufferonl+1

or at,oth 8T

8ela+edTransmission :

5'an re-

negotiate,lock

transfer rate1,utneedto wait

6'ontinu

Andr eaBianco

TNG gr oup-

olitecnicodiTorino

QoS Issuesin Telecommunication Net

wor ks-'2

a

Documents

Quality of service parameters in atm