Tema 4 Con Comentarios

7/27/2019 Tema 4 Con Comentarios

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QS (Q S)

IP


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QS IP

P S

T S

I

D S


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P S


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T A G QS

O

B

T S

R R

P S

A C


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F, (FCFS)

P /

FIFO (F I F O)

111

22

333

K C L: = C


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P

T

,

, .. IP /, , ..

R ?


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G (GPS)

= (,M) 1

=

+ 1

C: C ( )

: A : R , : R

GPS FCFS

GPS .


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H GPS PGPS COMPARE


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B (BR)

=

+

= (

, (

))

: BR

:

:

,

: R

:


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P GPS (PGPS) BR GPS: (

). PGPS ( WFQ)

BR

W ,

= (

)


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Q . PGPS

F: FTP

T: T FQ(=0):

FQ(=P):

L: =1

P: T (=4P)

F


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T S


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P M

T :

( ) ( ) : : 100

6000 !

.., 6000 . () .;1500

(.) . ( )


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A R

N QS (Q S)

Network Service Application

Constant bit rate Telephony

Real-time variable bit rate Videoconferencing

Non-real-time variable bit rate Streaming a movieAvailable bit rate File transfer

Example of QoS categories from ATM networks


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T

()

. ()

.


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T

() . () .


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L

()

. ()

.

() ,

() , ()

. ()

/


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A C A

S QS

Example flow specification


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F


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ATM

Celda no

conforme

Celda

conforme

Celda

conforme

ta(k) < TAT - TAT no cambia

TAT - < ta(k) TATTATTAT + T

TAT < ta(k)TAT ta(k) + T

TAT - TAT


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ATM (I)

Llegada de la celda

k en el instante ta(k)

TAT < ta(k) ?

TAT > ta(k)+ ?

TATTAT + T

Celda conforme

Celda no

conforme

TAT ta(k)No

No

Si

Si

ta(k) = Tiempo de llegada de una celdaT = I = Incremento

= L = Lmite

TAT: Tiempo de llegada terico


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ATM (II)

E (1) .

S TAT: .

S TAT, TAT

() T.

S TAT (TAT ), TAT T.

S (TAT ), . E TAT


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ATM (III)

Timeta(i)

ta(1) ta(2) ta(3) ta(4) ta(5)

T

TX+LCT

(TAT) Llegada de celdas ideal ( = 0.5 )

E

4.5 . P ,

4.5.


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ATM (IV)

Time

ta(i)

T

TX+LCT(TAT)

Llegada de celdas posible ( = 1.5 )

S ()

, TAT.


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ATM (V)

Time

ta(i)

T

TX+LCT

(TAT) Llegada de celdas posible ( = 3.5 )

C ,

. E T . E, >

T , N

N = 1+ (/ (T -)) , donde x es la parte entera de xN = 1+ (/ (T -)) = 1+ (3.5/ (4.5 - )) = 1+ (3.5/ 3.5)

= 1+ 1 = 2


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I (RSVP)


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RSVP E I

QS IP . I

I

S .

C

.


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RSVP A


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RSVP H R QS

QS

.

:

QS.


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A RSVP RSVP . I

.

RSVP . T

. RSVP

.

RSVP . I / .

RSVP , ,

.

RSVP .


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RSVP

(DA, PID , DP)DA IP

.

PID ID

T DP .

RSVP S D


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RSVP P R


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P M

S .

T .

P .S .

A ( )

IP .S T.

T

.

A: . U

.


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R M

A

T QS.

T , , QS .

A

A

A R (R ) QS.

A T (T ) .


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T T S E

Flow 1

Flow 2

Data Queue

Data Queue


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R M

R

.

A

M , .

S .

R S


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R S

WF (WF) S WF(*Q)

C () .

T ALL .

FF (FF) S FF(SQ), FF(S1(Q1), S2(Q2), )

C ,

.

SE (SE) S SS((S1, S2, ) Q)

C .

A .


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RSVP R SReservations

Distinct Shared

Fixed Filter Shared Explicit

None WildcardFilter

Wildcard

Explicit

Sender

Selection

S (WF SE)

( ).

FF ,

.


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R S E


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R S E

(C)


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Differentiated Services


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Providing Multiple Classes of Service

thus far: making the best of best effort service

one-size fits all service model

alternative: multiple classes of service

partition traffic into classes

network treats different classes of traffic differently(analogy: VIP service vs regular service)

No sepuedemostrar la imagen en estemomento.

0111 granularity: differential

service among multiple

classes, not among

individual connections

history: ToS bits


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D S N :

.

:

DS .

P


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P

R N A P (RSVP )

S N P (T C)

COPSSLS (IETF)

D S N P (TT)

QSNSIS3 S L P (IETF NSIS)

QS G S L P (IETF NSIS)


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P H B

6

() , TS

(T S) IP .


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Packet headers for IPv4 and IPv6


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P H B ()

, , , , .

. U EF PHB,

AF PHB , .


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Per Hop Behaviors (more)

Design with classes of QoS; customers buy what they want

Expedited class is sent in preference to regular class

Less expedited traffic but better quality for applications


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Implementation of DiffServ Customers mark desired class on packet

ISP shapes traffic to ensure markings are paid for

Routers use WFQ to give different service levels

Multiple classes of service: scenario


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Multiple classes of service: scenario

R1 R2H1

H2

H3

H41.5 Mbps linkR1 outputinterfacequeue

Scenario 1: mixed FTP and audio


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Scenario 1: mixed FTP and audio

Example: 1Mbps IP phone, FTP share 1.5 Mbps link.

bursts of FTP can congest router, cause audio loss

want to give priority to audio over FTP

packet marking needed for router to distinguishbetween different classes; and new router policyto treat packets accordingly

Principle 1

R1 R2

Principles for QOS Guarantees (more)


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what if applications misbehave (audio sends higher thandeclared rate)

policing: force source adherence to bandwidth allocations

marking and policing at network edge:

similar to ATM UNI (User Network Interface)

provide protection (isolation) for one class from othersPrinciple 2

R1 R2

1.5 Mbps link

1 Mbpsphone

packet marking and policing



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Allocating fixed (non-sharable) bandwidth to flow:inefficientuse of bandwidth if flows doesnt use its

allocation

While providing isolation, it is desirable to useresources as efficiently as possible

Principle 3

R1R2

1.5 Mbps link

1 Mbpsphone

1 Mbps logical link

0.5 Mbps logical link

Policing Mechanisms


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Policing Mechanisms

token bucket, WFQ combine to provide guaranteed upper

bound on delay, i.e., QoS guarantee!

WFQ

token rate, r

bucket size, bper-flowrate, R

D = b/Rmax

arrivingtraffic


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Policing Mechanisms (more)

Si(,)

Sj(,

)

i

j

, = 1, 2, , N

Si(, ) ( )i

j

F = i :

Si(, ) N

i: ; = 1, 2, , N

Si(, ): ,

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Tema 4 Con Comentarios