Department of Electrical Engineering Computer Networking Lab

Department of Electrical Engineering Computer Networking LabNational Sun Yat-Sen University Prof. Tsang-Ling Sheu

Integrated-Service versus Differentiated-Service Networks

許蒼嶺教授

國立中山大學

電機工程學系

Department of Electrical Engineering Computer Networking LabNational Sun Yat-Sen University Prof. Tsang-Ling Sheu 2

Outline

• Integrated Services– Traffic Model

– RSVP

• Differentiated Services– Architectures

– Traffic Classes and DSCP

– Queuing Disciplines

– Survey of Papers

Quality of Services

• Over-Provisioning

• Priority Queuing

• Per-Flow : Integrated Service, Intserv [RFC1633]

• Per-Class : Differentiated Services, Diffserv [RFC2475]

Integrated Services

• Resource ReSerVation Protocol

• Controlled-Load Service - RFC 2212

• Guaranteed Service - RFC 2211

Integrated Services

• Modules in Integrated-Service Traffic Model

– Admission Control• Determine if QoS Request Should be Granted

– Traffic Classifier• Map Packets/Flows to Service Classes

– Packet Scheduler• Forward Packets Based on Service Classes

IntServ Traffic Model

RSVPReservation

ClassifierPacket

Scheduler

RSVPReservation

Routing Protocols

AdmissionControl

ClassifierPacket

Scheduler

Router

IP Data Flow

Integrated Services

• Guaranteed Services

– For Delivering Real-Time Applications

– Provides an Assured Level Services

• Bandwidth

• End-to-End Delay Bound

• No Queuing Loss

• Controlled-Load Services

– Service Equivalent to Best-Effort Flows

RSVP Issues

• RSVP only Suits for Long-Duration Applications

– Too Expensive for WWW Transfers

• RSVP only Suits for Small-Size Networks

– Leads to too many Link States and Signaling Traffic

• RSVP Requires Application Supports

– Knowledge of Application QoS

– QoS API

R S V P c lo u dS en d er

R o u ter R o u terR ece iv er

(1 ) P A T H(2 ) P A T H

(3 ) P A T H

(4 ) R E S V

(5 ) R E S V(6 ) R E S V

Diffserv Architecture

D S C o re R o u te r

S o u rc e

D e s tin a tio n

D S D o m a in

D SD o m a in

E d g eR o u te r

D S In g re ssB o u n d a ry

R o u te r

D S E g re ssB o u n d a ry

R o u te r

Differentiated Services Domain

D ifferen tia ted S erv ices R eg io n

DiffServ Issues

• Scaling– Pushes Complex Forwarding Operations to Boundary Routers

• Control and management– Rely on New Configuration or Management Protocols

• Bandwidth Broker (BB)– Suits for a Small-Size Network

– Distributed BB

• Billing and Accounting– Based on Negotiated Traffic Profiles

Management and Billing Priority Levels

IP AddressesTCP Ports

Time of Day

Telnet

VideoConf.

Bandwidth Broker

Boundary Router

InteriorRouters

Packets In

Packets Out

Bandwidth Broker

Diffserv Field in IPV6 Header

V ers io n 8 -b it T O S 1 6 -b it T o ta l L en g th (in b y tes)L en g th

1 6 -b it Id en tifica tio n F la g s 1 3 -b it F ra g m en t O ffse t

8 -b it T T L 8 -b it P ro to co l 1 6 -b it H ea d er C h eck su m

3 2 -b it S o u rce IP A d d ress

3 2 -b it D estin a tio n IP A d d ress

6 -b it D S C P C U

8 -b it T O SV ers io n 8 -b it T ra ffic C la ss 2 0 -b it F lo w L a b e l

1 6 -b it P a y lo a d L en g th N ex t H ea d er H o p L im it

1 2 8 -b it S o u rce IP A d d ress

1 2 8 -b it D estin a tio n IP A d d ress

8 -b it T ra ffic C la ss

6 -b it D S C P C U

Diffserv – PHB Group

• DF (Default Forwarding, Best-Effort)– DSCP : 000000

• EF (Expedited Forwarding)– DSCP : 101110

• AF (Assured Forwarding)– DSCP : 4 Class, 3 Drop Precedence

Classifier & Traffic Conditioner

M e te r

T ra fficC o n d itio n e r

C la ss if ie r M a rk e r S h a p e r/D ro p p e rP a c k e ts

C la ss if ie r M a rk e r S h a p e r/D ro p p e r C la ss if ie d

P a c k e ts

First-Come-First-Serve (FCFS)

• Simplest Queue• Packet will be dropped when queue is full• Rear or front dropping

Packet outPacket in

Server23456

Priority Queue (PQ)

• Packets with higher-priority will always be sent first

• Starvation in lower-priority queue

Packet outPacket in

High Priority Queue

Low Priority Queue

ServerClassifier

Round-Robin (RR)

Arrivals departuresLinkClassify

Queues

Weighted Round Robin (WRR)M. Katevenis, IEEE Journal on Selected Areas in Communications, 1991

• General case of Round Robin

• More weight with higher-priority class

Packet outPacket in

ServerClassifier

Weight = 3

Weight = 1

Weight = 2

Weighted Fair Queue (WFQ)A. Demers, SIGCOMM’ 89

• Provide fairness in variable-length IP packets

• Packets sent by the order of estimated completion time

)),,(),,1(max(),( ikaikFikS )(

),(),(),(

ikLikSikF

otherwise

tActiveSetiifw

trtActiveSetjj

WFQ S(4,1)=F(3,1)=17

Weight = 1

Weight = 3

Weight = 2

F(4,1)= 20

S(2,1)=a(2,1)=7

F(2,1)=9

L(1,1)/r1=80/20=4

a(4,1)=13

61720 7913

L(2,1)=40

L(3,1)=100

L(1,1)=80

L(4,1)=60

L(1,2)=40

L(2,2)=60

L(3,2)=60

L(1,3)=90

L(2,3)=150

L(3,3)=90

L(4,3)=90

Deficit Round Robin (DRR)M. Shreedhar, IEEE/ACM Transactions on Networking, 1996

• WFQ is not easy to be implemented, O(log P)

• DRR

– Round Robin fashion, O(1)

– Use Quantum instead of Weight

– Use Deficit Counter to provide fairness

150250

200150

CounterQuantum

150250

200150

CounterQuantum

(a) (b)

RR PointerRR Pointer

Token Bucket (TB)

• Leaky Bucket:Traffic Shaping

• Token Bucket:Shaping with more burst tolerance

LeakyBucket

CapacityC

BurstyTraffic

Constant RateR

TokenBucket

TokenCapacity bBursty

Traffic

Buffer Size

Constant Token Rater

Minimum Threshold (Minth)Maximum Threshold (Maxth)Average Queue Size (avg)Marking Probability (Pmax)

Random Early Detection (RED)

P (D ro p )

M in th M a x th

P m a x

Random Early Detection(RED)S. Floyd, IEEE/ACM Transactions on Networking, 1993

• Random drop or mark packets before buffer overflow

minth maxth0

Qwavgwavg qq )1(

)1/( bba pcountpp

thpb minmax

minavgmaxp

RED with In/Out Bit (RIO)D. D. Clark, IEEE/ACM Transactions on Networking, 1998

• Different marking probability for In/Out packet

min_out max_out0

Pmax_out

avg_totalmin_in max_in0

Pmax_in

avg_in

P(Drop_In) P(Drop_Out)

RED with In/Out bit (RIO)In Packet :

Minimum Threshold (Minth_in)Maximum Threshold (Maxth_in)Average Queue Size (avg_in)Marking Probability (Pmax_in)

Out Packet :Minimum Threshold (Minth_out)Maximum Threshold (Maxth_out)Average Queue Size (avg_total)Marking Probability (Pmax_out)

P (D ro p )

M in th _ o u t M a x th _ o u t

P m a x_ o u t

a v g _ in /a v g _ to ta lM in th _ in M a x th _ in

P m a x_ in

Proportional DiffServC. Dovrolis, IEEE Network, 1999

• Absolute DiffServ (WRR, DRR)– Use static resource reservation instead of dynamic resource reserv

• Proportional DiffServ (WTP, DWFQ, PLQ)– Provide QoS differentiation between traffic classes– Predictable:

• High-priority class must have better or the same QoS as low- priority class

– Controllable• Provide a time tuning knob to adjust the differentiation betwee

n classes

Waiting Time Priority (WTP)C. Dovrolis, IEEE/ACM Transactions on Networking, 2000

• General case of Time-Dependent Priorities

[L. Kleinrock, Queuing Systems, 1976]

– Delay Proportional Parameter δi

– Active(Busy) Set B(t)

– Normalized Head Waiting Time

– Packet with the most waiting time will be sent first

iii twtw /)()(~

)(~maxarg

)(twj i

Dynamic WFQ (DWFQ)Chin-Chang Li, ICCCN, 2000

WFQScheduler

Class 1 buffer

Class 2 buffer

Class 3 buffer

Class n buffer

ClassiferPacket outPacket in

Arrival RateMeasurement

BacklogMeasurement

Weightadjustment

1: UbUbvv k

Probabilistic Longest Queue (PLQ)Jung-Shian Li, GLOBECOMM’01

Logic Queue 1

Classifier Dropper Scheduler

Info-Component

Packet outPacket in Logic Queue 2

Logic Queue 3

Logic Queue 4 N

j jjiii QcQcP

j jjiii sQsQP

PQ with EF Token Bucket

• EF PHB has the highest priority

• Use a Token Bucket to limit EF maximum bit rate

Default

Token RateREF_Reserved

Priority 3

Priority 2

Priority 1

Server

Priority Queue with Quantum (PQWQ)

• Provide fairness between PHBs– Use counters for all PHBs in order to limit bytes sent in one round– Quantum values will be added to counters after one round

• Provide low delay to EF PHB– EF PHB has the highest priority– If counter is enough, higher priority PHB will be sent first in one r

ound– Avoid the delay by Round Robin fashion

PQWQ (cont.)

Default

Counter

Priority 3

Priority 2

Priority 1

Server

Quantum

Diffserv Potential Problems

1. Ineffectual End-to-End QoS guarantee2. Unfair bandwidth sharing3. Packets only dropped at congested links when congest

Various Diffserv Architectures

1. Packet-Marking Engine (PME)[Wu-Chang Feng, 1999]

2. Feedback Controlled Diffserv[Hungkei Chow, 1999]

3. Diffserv in MPLS[Y. Bernt, 2000]

4. RSVP in Diffserv[I. Andrikopoulos, 1999]

Packet-Marking Engine (PME)

•New Packet-Marking Engine•TCP-like algorithm and Modified TCP congestion control•Dynamic Marking probability (mprob)

Adv :•TCP-friendly algorithms•Adative packet marking to improve end-to-end throughput•Traffic fairness

Disadv :•1-bit priority for packet marking•Support TCP traffic only•Update network interface in host/nodes

Feedback Controlled Diffserv•New FC-DS nodes•Probe/Report control packet•Adaptvie QoS

Adv :•Current network status report•Adative traffic conditioning•Fair network resources allocation

Disadv :•Upgrade DS nodes to support FC scheme•More processing complexity in FC-DS ingress nodes•Extra processing of probe control packets

Diffserv in MPLS

P H BM a p p e r

P H B -to -A T M

D iffse rvM o d u le

L D P D a e m o nD S -c o m p a tib le

T C P /U D P IP

R o u tin gD a e m o n

M P L SD a e m o n

G S M PIn te rfa c e

A d m iss io nC o n tro l

F lo w M IBC o n tro lle r

F lo wM IB

A T M D riv e r

S w itch C o n tro ller

A T M S w itchA T MM IB

L D P S e ss io n to L D P p e e r

RSVP in Diffserv

E n d -u ser d om ain(stu b n etw ork )

D S d om ain(tran sit n etw ork )

E d g eR o u te r

E d g eR o u te rB o u n d a ry

R o u te rsR S V P sig n a lin gIn tserv p a ra m etersT ra ffic S h a p in gP a ck et M a rk in g

A g g reg a te P o lic in g (B A )D iffserv P H BC a rr ies R S V P m essa g e

" T ra n sp a ren tly "

Self-Adaptive Diffserv Router

E g re ss In te rfa c e(c la ss ify , m e te r ,

a c tio n , q u e u e in g )P H B

R o u tin gC o re

In g re ss In te rfa c e(c la ss ify , m e te r ,

a c tio n , q u e u e in g )T ra ffic

C o n d itio n in g

S e lf-A d a p tiv eC o n tro lle r

D iffse rvc o n fig u ra tio n &

m a n a g e m e n tin te rfa c e

D a ta in

M a n a g e m e n t

S N M P ,C O P S

e tc .

D a ta o u t

Q o S &S e lf-A d a p tiv e

C o n tro l M e ssa g e s

Q o S &S e lf-A d a p tiv e

C o n tro l M e ssa g e s

D S E g re ssB o u n d a ry R o u te r

D S In g re ssB o u n d a ry R o u te r

D S C o reR o u te r

S o u rc e

D e s tin a tio n

E d g eR o u te r

D SD o m a in

Self-Adaptive Diffserv Architecture

(1 ) M eter in g an d P erform in gS e lf-A d ap tive A lgor ith m

(2 ) S en d in g S e lf-A d ap tive C on tro lM essages to In gress R ou ter if n eed ed

(3 ) R ece iv in gS e lf-A d ap tive

con tro l m essagesan d R e-m ark in gor R e-a lloca tin g

resou rces

(4 ) S en d in g R em ark ed F low M essages

Self-Adaptive Control Message Format

IP H ead e r T C P H ead e r O th e r S e lf-A d a p tiv e In fo rm a tio n (o p tio n a l)

S e lf-A d a p tiv e C o n tro l M e ssa g e

4 -b itv e rs io n

4 -b ith ead erlen g th

6 -b it O ldD S C P

C U 1 6 -b it to ta l len g th (in b yte s)

1 6 -b it id en tifica tio n 3 -b itf la g s 1 3 -b it frag m en t o ffse t

8 -b it tim e toliv e (T T L )

8 -b it p ro to co l 1 6 -b it h ead e r ch eck su m

3 2 -b it so u rce IP ad d re ss

3 2 -b it d es tin a tio n IP ad d ress

IP H ea d er

3 2 -b it seq u en ce n u m b er

3 2 -b it ack n o w led g em en t n u m b er

1 6 -b it T C P ch eck su m

1 6 -b it so u rce p o rt n u m b er 1 6 -b it d es tin a tio n p o rt n u m b er

4 -b ith ead erlen g th

6 -b it S A I(N ew D S C P )

1 6 -b it w in d o w s iz e

1 6 -b it u rg en t p o in te r

T C P H ea d er

6-Bit SAI Field

PHBDSCP Field

SAI Field

Description

EF 101110 0xxxxxxIncrease weight for

EF 101110 1xxxxxxDecrease weight for

DSCPNew

DSCPChange to new DSCP

BE 000000 0xxxxxxIncrease weight for

BE 000000 1xxxxxxDecrease weight for

2-Bit CU Field

CU value Packet Type

00 Normal Data Packet

10 Normal Control Packet

01 Congested Data Packet

11 Congested Control Packet

Conclusions• Integrated Services

– Per flow QoS

– RSVP

• DiffServ Architectures– Per Class QoS

– Traffic Classification

• Queuing and Scheduling– WRR, WFQ, DRR, Token Bucket, Proportional Delay, etc.

• MPLS and DiffServ

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