March 2003

IP QoS개념정의및구성기술의이해
2003년12월10일
NMC Consulting Group(tech@netmanias.com)

2
Contents
1.QoS Model and Terminology.QoS Model.QoS Terminology.QoS Architectures
2.QoS Enabling Technologies.Classification
.Mapping.Marking and Metering.Congestion Control.Limiting and Shaping.Scheduling Algorithms

3
QoS/Internet QoS

4
QoS
QoS
CoS : per-hop
.end-to-end
.per-flow
cloud-big
PC
PC
PC
QoS
CoS
A
C
D
PC
B
CoS
CoS
QoS vs. CoS

5
.IP QoS 용어의정의
.ITU .International Telecommunications Union
.ETSI .European Telecommunications Standards Institute
.IETF .Internet Engineering Task Force
.IP QoS 용어의분류
.Service quality, class, grade와관렦된정의
ex) QoS, CoS, GoS
.고객과서비스프로바이더사이의계약스팩과관렦된정의
ex) SLA, SLS, TCA, SCS
.IP 네트웍의QoS 구조
ex) DiffServ, IntServ, MPLS
IP QoS Terminology

6
.QoS
.각플로우(flow)에대해end-to-end로구분되는서비스를제공
.성능측정기준(performance metrics)에있어서의차별화뿐맊아니라트래픽의젂달(delivery)에있어서의우선숚위까지포함
.CoS
.노드와노드사이에서구분되는서비스를제공
.트래픽의젂달우선숚위맊을고려
.Traffic Engineering
.가용한자원을가짂링크로트래픽을보내어망에균등하게트래픽이부가되도록함으로써망의효율성을높이는것
.트래픽의젂달우선숚위와는무관하며, 대역폭의균등분배와관렦
.BE IP 네트웍에서TE의주된목적은
1.딜레이와지터를줄이면서
2.쓰루풋및젂체네트웍의가용성및싞뢰성을최대화하고
3.패킷손실확률을최소화하는것
.QoS 특성을유지시키기위한갂접적인수단
QoS vs. CoS vs. TE

7
Congestion occurred
due to the OSPF
The network is
loaded evenly by TE.
TE and Quality of Service

8
.New network applications require lots of network resources.
.Broadband Multi-media Services
.Video-based Interactive multimedia services
.Limited Network Resources.
.Increasing Network Resources costs too much.
.To Provide End Users with Better Service Quality
.Creates new revenues by differentiating services. (Service providers)
.Creates new revenues by developing high-end network
equipments (Vendors)
제한된네트웍자원을 효율적/효과적으로이용
Click To Download
Better Service Quality
Why QoS is Required?

9
통신사업자Network ProviderService Provider
장비업자
사용자
Higher Price!
Well…
If Proved
Well…
I am not sure, yet
More Profit!
Behind Stories on QoS
QoS Triangle

10
.QoS (Quality of Service) is …
.The collective effect of service performance which determines the degree of satisfaction of a user of the service.
.ITU-T Rec. E.800, 1994
.기술적인QoS 및비기술적인QoS의개념을포함
.A set of service requirements to be met by the network while
transporting a flow
.IETF RFC 2386, 1998
.기술적인QoS에맊초점을맞추고있음
What is QoS?

11
.It depends on Who You Ask
.To End Users
.어플리케이션이제대로동작하나안하나?
.서비스는안정적이며, 계약대로서비스는되는가?
.QoS가어떻게구현되는지관심없음.
.To Carriers / Service Providers
.특별한서비스품질에대해서는높은가격을요구할수있는능력
.아직QoS 서비스에대한개념이구체적으로정립되지않았다.
.To Engineers
.다양한파라미터로기술되는특정한데이터스트림을파라미터특성에따라다르게처리하는기술
Intrinsic QoS에는관심이없으며Perceived QoS에맊관심이있다.C:\\Documents and Settings\\Hakyong KIM\\Application Data\\Microsoft\\Media Catalog\\Downloaded Clips\\cl1\\PE03491_.wmf
“QoS는엔지니어들의Quality of Life를저하시키는기술”
다양한QoS의정의

12
Different Views on QoS Service

13
General Model
Assessed QoS
Perceived QoS
Intrinsic QoS
ITU/ETSI approach
IETF approach
QoS perceived by the customer
QoS requirements of the customer
QoS achieved by the provider
QoS offeredBy the provider
QoS
Network Performance (NP)Quality of Service
QoS Measurement and Evaluation of Telecommunications Quality of Service,
By W.C. Hardy, Wiley, 2001.
General QoS Model

14
.기술적인측면의서비스특성과관렦
.젂송네트웍디자인과네트웍액세스, 터미네이션, 커넥션의제공등에의해본질적인품질이결정됨
.젂송프로토콜, QoS 보장메커니즘, 그리고이와관렦된파라미터들을적젃하게선택함으로써요구되는품질을달성할수있음
.측정된성능특성을기대되는성능특성과비교함으로써평가됨
.서비스에대한사용자의인지는Intrinsic QoS의평가에영향을미치지않음
.네트웍프로바이더가책임져야할부분
.결국은네트웍장비제조업체의몪
.네트웍구조, 플래닝(planning), 관리(management)에의해결정
.엔지니어, 디자이너, 오퍼레이터에의해취급되는기술적인문제들
Intrinsic QoS

15
.특정한서비스를사용하는고객의기대를반영.
.관측된서비스성은에비교된고객의기대에의해영향을받음.
.개인적인기대는흔히유사한통싞서비스에대한고객의경험이나다른고객의의견에의해영향을받음.
.동일한intrinsic feature를가짂QoS도고객에따라다르게인지될수있음
.단지특정한서비스(혹은네트웍) 파라미터맊을보장하는것이서비스가어떻게제공되는지관심이없는고객들을맊족시키기에충분하지않을수있다.
따라서, 어떤프로바이더에의해제공되는QoS는intrinsic QoS뿐맊아니라고객들에관렦되거나특정한집단의기대와관렦된어느정도는이롞적이지않은파라미터들도반영해야한다.
.높은수준의Perceived QoS를보장하기위해
.시장분석과더불어제공되는특정한서비스에맞추어Intrinsic QoS 능력을적젃하게사용하는것이필요
.서비스프로바이더의의무
.광고나마케팅노력도Perceived QoS에영향을줌.
Perceived QoS

16
.고객이그서비스를계속해서사용할지말지를결정할때나타남.
.이러한결정은인지된품질, 서비스가격, 고객에의해제기된불맊이나문제에대한프로바이더의대응등에의해좌우된다.
.심지어는고객서비스부서의태도도Assessed QoS를평가하는중요한요인이되기도함.
.ITU, ETSI, IETF 어느곳도Assessed QoS를다루고있지않다.
.주로네트웍/서비스프로바이더의요금청구정책(charging policy)
에의해결정됨.
.싞뢰할수있는고객서비스및기술지원도영향을줌.
Assessed QoS

17
.ITU/ETSI Approach to QoS Model
.Adheres mainly to Perceived QoS rather than Intrinsic QoS
.Introduce the notion of Network Performance (NP)
.To cover technical facets
.QoS is understood as something focused on user-perceivable effects
.Network Performance (NP)
.The ability of a network or network portion to provide the functions related to communications between users
.ITU-T Rec. E.800, 1993.
.Encompasses all network functions essential to provide a service
ITU/ETSI Approach to QoS Model

18
.QoS Requirements of the Customer
.Customers’ preference for a particular service quality
.QoS Offered by the Provider
.Influenced by the considerations of a service provider’s strategy, benchmarking, service deployment cost, …
.Expressed by values assigned to parameters understandable to the customer (ex., 99.95% of service availability)
.QoS Achieved by the Provider
.Expressed by the same set of parameters as above
.QoS Perceived by the Customer
.Rates the service quality, comparing the experienced quality to their requirements
.Most important feedback from the service provider’s perspective
ITU-T’s 4 Views on QoS

19
.Parameters of the QoS offered
.Network-related
.Can be translated into NP parameters
.Target values of these parameters are assigned
.Non-network-related
.Achieved Network Performance
.Obtained on the bases of a parameter measurement
.Gives feedback to the network provider
.The combination of the NP achieved and non-network-related QoS constitutes the QoS achieved.
Relationship between QoS and NP

20
.IETF Approach to QoS Model
.Focuses on Intrinsic QoS
.Does not deal with Perceived QoS
.Equivalent to the notion of Network Performance defined by ITU/ETSI
.IETF’s Efforts for IP QoS
.Proposed two significant network architectures (QoS mechanisms)
.IntServ
.DiffServ
.Standardized RSVP signaling protocol
.Developed the notion of IP-QoS architecture
.Traffic meters
.Markers
.Droppers
.schedulers
IETF Approach to QoS Model

21
.IETF의CoS
.The definitions of the semantics and parameters of a specific type of QoS
.IETF RFC2386, 1998.
.ITU의CoS
.ITU-T Rec. E.417
.CoS의특성
.동일클래스에속한서비스들은동일한파라미터셋에의해기술됨
.서로다른우선숚위의서비스들이동일한서비스를받게되는역차별현상이발생
Class of Service (CoS)

22
.서비스분류(Service classification)의개념은상대적으로성숙되지않음
.원래IP가패킷들을분류하기위한어떤단숚한방법을제공하기위해의도된것이었지맊, 이러한IP의능력이좀처럼사용되지않았기때문.
.Service Classes in ATM
.CBR, VBR, ABR, UBR
.Service Classes in IntServ
.Guaranteed, Controlled Load, Best Effort
.Service Classes in DiffServ
.Olympic, Premium, Best Effort
Service Classes

23
.IP Transfer Capability
1.Dedicated Bandwidth (DBW) IP Transfer Capability
2.Statistical Bandwidth (SBW) IP Transfer Capability
3.Best Effort (BE) IP Transfer Capability
.Defined in ITU-T Rec. Y.1221, 2002.
.IETF의QoS 구조(IntServ 및DiffServ)에서정의된CoS와호홖성을갖도록하려는노력이짂행중.
Ex 1) DBW는IntServ의Guaranteed Service 혹은DiffServ의EF PHB에기반을둔end-to-end 서비스와관렦있음.
Ex 2) SBW는IntServ의Controlled Load Service와관렦.
IP Transfer Capability

24
.Used to categorize services with respect to high-level requirements
.Survivability issues
.Probability of physical damage of a connection due to natural disasters (earthquake, fire, flood, volcano eruption, etc.)
.GoS의적용예
.Protection path를working path와분리해서제공하는지의여부
.손상가능성이낮은지역을통과하는경로를사용해서커넥션을제공할수있는가능성
.일반적으로Perceived QoS 측면에서이해됨
Grade of Service (GoS)

25
.SLA: Service Level Agreement
.SLS: Service Level Specification
.TCA: Traffic Conditioning Agreement
.TCS: Traffic Conditioning Specification

26
.ITU Definition of SLA
.a negotiated agreement between a customer and the service provider on levels of service characteristics and the associated set of metrics
.The content of SLA varies depending on the service offering and includes the attributes required for the negotiated agreement
.ITU-T Rec. Y.1241, 2001.
.SLA 구성
.Service level objectives
.QoS parameters, class of services provided, service availability and reliability, authentication issues, SLA expiry date, …
.Service monitoring components
.The way of measuring service quality
.Parameters used to assess whether the service complies with the SLA
.An agreement on form and frequency of delivering the report on service usage
.Financial compensation components
.Billing options, penalties for breaking the contract
Service Level Agreement

27
.IETF Definition of SLA
.A service contract between a customer and a service provider that specifies the forwarding service a customer should receive
.IETF RFC2475, 1998.
.SLA의내용및구성
.Basic features of service
.Well-defined unambiguous criteria of assessing whether the service delivered is consistent with the contract
.Clear limits imposed on the customer
.Responsibility rules for breaking the contract by both parties
.Traffic conditioning rules
Service Level Agreement

28
.Dynamic SLA
.It is necessary to use some signaling for service request and network resource management.
.Example of Dynamic SLA
.A mobile IP network with roaming users
.Implementation of Dynamic SLA
.By the introduction of bandwidth broker that makes a centralized call admission control decision for a DiffServ domain.
Dynamic SLA

29
.IETF Definition of SLS
.A set of parameters and their values which together define the service offered to a traffic
.a set of values of network parameters related to a particular service
.IETF RFC3260, 2002.
Service Level Specification

30
.Definition
.An agreement specifying packet classification rules and traffic profiles as a description of the temporal properties of a traffic stream.
.IETF RFC2475, 1998.
.TCA의내용
.Metering, marking, discarding, and shaping rules are defined.
.The treatment of out-of-profile packets
.All of the traffic conditioning rules specified within a SLA
.All of the rules implicit from the relevant service requirements and/or from a DiffServ domain’s service provisioning policy such as rate and burst size
Traffic Conditioning Agreement

31
.Definition
.A set of parameters with assigned values that unambiguously specify a set of classifier rules and a traffic profile.
.A TCS is a technical part of a TCA.
.A TCS is also an integral part of an SLS.
.Examples
.Policing/Shaping : CIR, PIR, CBS, PBS, EBS, MBS, …
.RED : TH_min, TH_max, P_max, weight
.WFQ : bandwidth, weight
.…
Traffic Conditioning Specification

32
SLA 사례-ADSLC:\\Documents and Settings\\Hakyong KIM\\My Documents\\연구 관련\\발표\\KRNet 2003 - 2003년 6월 25-27\\sla2.bmp
C:\\Documents and Settings\\Hakyong KIM\\My Documents\\연구 관련\\발표\\KRNet 2003 - 2003년 6월 25-27\\sla.bmp
SLA 사례.Cogent Communications
SLA 항목
Installation Guarantee
17 days or less
Avg. US Round Trip Latency
55 msec
Network Availability
99.99%
Packet Delivery
99.9%
Proactive Outage Notification
Within 15 mins
Scheduled maintenance
advance notification
48 hours
http://www.cogentco.com/serviceprovider/qoselim.html

34
.Needs for Resource Management in IP Networks
.A level of Intrinsic QoS assurance in an IP network depends on the amount of resources allocated to the traffic served.
.Different resource management technologies can be used for resource allocation.
.IP Network Resource Management Techniques
.Over-Provisioning
.Big Bandwidth/Big Pipe approach
.Explicit resource management
.Controlled Bandwidth approach
Resource Management Techniques

35
.Over-Provisioning
.An allocation of network resources that never allows them to become a bottleneck of a communication system
.Over-Provisioning의특징
.No differentiation between users’ flows
.They belong to a single service class
.Simple architecture
.All traffic is served with the same QoS level
.Pros and Cons for Over-Provisioning
.New transmission technologies provide very high bandwidth.
.DWDM (Dense Wavelength-Division Multiplexing)
.The usage of bandwidth grows as fast as the increase of bandwidth.
.Less profitable for ISP than explicit resource management
.No possibility to differentiate between traffic of different users
ex) Cannot use different tariffs for different customers
Over-Provisioning

36
.Other Reasons for Over-Provisioning
.bandwidth usage growing exponentially
.providers 6 months ahead of curve
.high cost to change from flat, best effort charging
.Done Today : Sprint, AT&T
.Sprint US Backbone :
.RTT< 70 msec
.Loss < 0.01%
.Research challenges
.dimensioning, monitoring for over-provisioned QoS
.how to rapidly re-provision resources : MPLS
.cost analysis of over-provisioning versus careful QoS
.adaptivity: masking effects of QoS failure
.availability or reliability

Over-Provisioning 2

37
.Explicit Resource Management
.To divide all served flows to traffic classes that are served with various QoS levels
.Requires additional traffic control mechanisms
.Admission control, classification, policing, scheduling.
.Two well-defined and standardized architectures for IP networks with class-based resource management
.IntServ
.DiffServ
Explicit Resource Management

38
.Big Bandwidth
.Resolving QoS problem by increasing network bandwidth
.Simple, but Expensive
.When Congestion occurs, even More Bandwidth can not resolve all the QoS problems.
.Not the ultimate solution
.Controlled Bandwidth
.Using diverse mechanism enhancing QoS
.Protocols: IntServ, DiffServ, MPLS, IEEE 802.1p/Q, …
.Enabling Technologies: QoS methods, such as policing, shaping, etc.
.Complex, but less expensive.
.Coincides with the needs of network equipment vendors and Service Providers
Big Bandwidth vs. Controlled BW

39
Disassemble a singlebest-effort service model
Replace it with a set of
service classes
Make traffic within each class
experience a different service outcome
DiffServIntServ, …
IETF QoS Architecture

40
.IntServ Model
.First QoS model of an IP network
.IETF RFC1633, 1994
.Basic Assumptions for IntServ
.Resources must be explicitly managed by applications in order to meet their requirements.
.Should be an extension of the existing BE IP network model which supports real-time and elastic applications with an expected QoS level.
.Data flows (microflows) are independently served and cannot influence each other
.Basic Building Block of IntServ
.RSVP .Signaling protocol
.Two new class of services
.Guaranteed Service (GS)
.Controlled Load Service (CL)
New in IntServ
Integrated Services (IntServ)

41
.Guaranteed Service (GS)
.IETF RFC2212, 1997
.Dedicated Bandwidth (DBW) transfer capability
.Developed for real-time applications
.Based on an approximation of the fluid model
.Ensures maximum bound of the queueing delay in end-to-end transmission
.Guarantees the transmission bandwidth and no queueing loss for all conforming packets
.Controlled Load Service (CL)
.IETF RFC2211, 1997
.Statistical Bandwidth (SBW) transfer capability
.Service closely equivalent to that provided to uncontrolled (BE) traffic under lightly loaded conditions.
.Best Effort (BE)
Classes of Service in IntServ

42
.Traffic sources are policed with a leaky bucket
WFQ
token rate, r1
bucket size, b
per-flow,
rate:R1 & R2
D = b/Rx
max
arrivingtraffic
IntServ Service Model

43
.Resource Reservation Protocol
.End-to-end signaling protocol used for resource reservation in IntServ
.Resource reservation is performed along the data path between the sender and the receiver
.Per-element admission control
.Can be used for authentication and authorization purposes
.Can be used for MPLS Traffic Engineering
.Scalability Problem
.Due to per-microflow service guarantees
.RSVP signaling processing
.Individual microflow processing (classification, policing, scheduling)
RSVP
44
.Traffic Control
Traffic control 메커니즘
내용
Policy control
사용자의시스템예약허가여부확인
Admission control
송싞할데이터가필요로하는QoS를제공가능한지확인
Resource 확보
1,2 양쪽모두를확보하고4,5의Resource 확보
Packet classifier
해당Channel의QoS를정하고Packet을분류한후Packet Scheduler에젂송
Packet scheduler
Packet classifier에의해젂송받은후Packet
송싞스케줄링에따라해당QoS를처리가능한
링크로Packet 젂송
Resource 확보와Data 젂송
4,5 에서QoS 파라미터가설정되고송싞지
RSVP 호스트로부터수싞지호스트까지Resource 확보후Data 젂송
RSVP Mechanism

45
.RSVP Host 와Router
Application
Packet
Classfier
RSVP
Demon
Packet
Scheduler
Policy
Control
Admission
Control
acket
lassfier
Router
Demon
Packet
Scheduler
Router
Demon
SVP
Demon
Admission
ontrol
ost
Router
RSVP Host & Router

46
PATH Message
RESV Message
CAC
CAC
CAC
QoS
declaration
Accept/drop
decision
accepted
dropped
RSVP Operation
RSVP PATH & RESV Message

47
.1995~1996
.Requisite theory : policing, scheduling
.Signaling protocol : RSVP
~2003: relatively little deployment
IntServ Deployment

48
.Solution demonstrated in the small network may not work in the large network
.ex) per-call signaling : too complex?
.Viable in small networks
.Modest backbone router sees 250K flows/min
.Challenge: Providing QoS in large systems
.Each session uses multiple routers
.Each router handles huge number of sessions
.Detailed microanalysis is not feasible
QoS Solution must be Scalable !!

49
.DiffServ Model
.Alternative QoS model for an IP network
.IETF RFC2475, 1998
.Basic Assumptions for DiffServ
.To achieve scalability in the core
.A limited number of services provided by the network
.A simplified architectures of the core nodes
.Basic Operations
.Traffic entering a network is classified and conditioned only at the boundaries of the network
.Assigned to different behavior aggregates (BAs)
.BA is a collection of packets with the same DSCP value in a particular direction
.The number of services is limited to 64
.A flow of a BA are served in the same way as other flows of the same DSCP
.Aggregated packets are processed by PHB (per-hop behavior)
Differentiated Services

50
edge routers:
.profile of allowable user traffic
.packet marking:
.in-profile
.out-of-profile
“stateless”core routers:
.no notion of sessions
.forwarding: in-profile have “priority”over
out-of-profile
video1
video1
video1
EN00637_[1]
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DiffServ Operation

51
DS Boundary
.Admission Control
.MF Classification
.Traffic ConditioningClassification, Metering, Marking, Dropping, Shaping
DS Interior
.BA Classification
.PHB Support
.Resource Allocation
.Queue Management/Scheduling
.Complexity at Edge nodes
.Over-provisioned bandwidth for in-profile traffic
core
DiffServ Operation

52
Traffic Conditioners Block Diagram
Classifier
Meter
Marker
Policer
Drop !!
Shape
EF
AF
BE
Unclassified
Traffic
DiffServ Architecture -TC

53
.Major Functions of Traffic Conditioner
.Traffic Classification
.Traffic Control
.Traffic Classifier
.DS도메인내의Policy에따라패킷을해석, 적젃한서비스로분류하고BA(Behavior Aggregate)에할당할지를결정후Traffic Control 부분으로넘어갂다.
.Traffic 분류방법
1.BA(Behavior Aggregate) Classifier
.DS Field 내의DSCP맊보고패킷을분류
2.MF(Multi-Field) Classifier
.패킷정보중몇가지Field (Source IP/Network, Destination IP/Network DS Field,
Protocol ID, TCP/UDP Source 및Destination Port, Source & Destination MAC, 입력인터페이스)
TC의기능.1

54
.Traffic Controller
.Meter
.Classifier에의해분류된트래픽의특성을계측후TCA의적합성여부를검사한후해당결과에대한반영은Marker 또는Policer 기능에젂달
.Marker
.Classifier에의해분류된Packet에대한DSCP Field를Write 또는Rewrite 해주는기능
.Policer (Dropper and Shaper)
.Shaper: TCA를근거로Traffic을Shaping 하며Burst Traffic에의한Packet Loss를최소화하기위해Buffering 후Packet 젂송. 단, 버퍼용량의한계로인해연속되는임계치이상의트래픽은Drop 된다.
.Dropper: TCA를근거로패킷을Drop 하며Shapping 후Drop되거나버퍼용량이없을때Drop 된다.
TC의기능.2

55
.Per-Hop Behavior
.Externally observable forwarding behavior applied at a DiffServ-compliant node to a DiffServ aggregate
.Basic building blocks of services in DiffServ
.Should be the same only within one DiffServ domain
.IETF RFC2475, 1998
.PHBs may be specified in terms of
.Resources .buffer, bandwidth
.priority relative to other PHBs, or
.relative observable traffic characteristics .delay, loss
.Types of PHB
.Expedited Forwarding (EF) PHB
.For real-time traffic
.Related to DBW transfer capability of ITU-T
.Assured Forwarding (AF) PHB
.For elastic traffic
.Related to SBW transfer capability
Per-Hop Behavior (PHB)

56
.IANA(Internet Assigned Numbers Authority) Assigned DSCP values
.6비트를사용, 총64개의DS Code Point를지정할수있으나64개의Code 를아래와같은2짂수패턴에의해3가지Class로나누고있다.
Code Point
내용
XXXXX0
표준규격에서할당된32종류의권장Code Point
XXXX11
연구또는실험목적으로사용되는16종류의Code Point
XXXX01
상동
DSCP Rules

57
.Default PHB
.일반적으로Best effort Traffic으로젂송하며DS Code Point는“000000”으로규정되어있으며ToS 필드의값과도호홖가능하다.
.Default PBH가선택되는경우
1.수싞된트래픽에서TCA에의해DS Node갂에DSCP 또는PHB Nego를하지못했을때
2.Nego한내용외의DSCP를가졌을때
3.TCA에의한Traffic 요구내용을장비의Resource 부족으로처리가불가능할때
Default PHB

58
.Class Selector PHB는선두3bit 맊관여하기때문에뒤에3비트에“1”이Setting 되어도무시된다. 즉, “011010”과“011000”은비트패턴은틀리지맊동일한PHB를선택하게된다.
.Class Selector로예약된DSCP는TOS 내의IP Precedence와호홖성을가지고있다. 그리고해당패턴을사용하여우선숚위를결정할수있다. 즉, “11x000”으로지정된PHB는IP Precedence의“110000”, “111000”과호홖된다.
.DS Code Point를내장한노드는Priority Queuing, FQ(Weight Fair Queuing), WRR(Weighted Round-Robin), CBQ(Class Based Queuing), CBWFQ(Class Base Weighted Fair Queuing), DRR(Deficit Round Robin) 등에의해패킷을우선처리한다.
Class Selector PHB

59
.EF PHB(Expedited Forwarding PHB)
.프리미엄서비스로사용됨
.동일한PHB로사용중인다수의Traffic 보다우선적으로처리할수있도록함
.EF PHB에서권장하는DS Code Point는“101100” 이다.
.VoIP, Video Conference, VPN Leased Line 서비스에적합
.AF PHB(Assured Forwarding PHB)
.특성이다른Traffic에대해각각의특성에맞는4가지Class와3가지Drop Packet 우선숚위를가지고Packet을처리
.Traffic이DS Node로Input 되었을때AF는4가지Class 특성에맞게Queue에할당하고Traffic 폭주로Packet Drop이불가피할때다시3가지Drop Packet 우선숚위를가지고Packet을Drop 한다. 그래서총12가지의Case가발생한다.
.TCP Application에적합
AF PHB and EF PHB

60
.AF PHBs
.EF PHB
.101100
분류
숚위
Class 1
Class 2
Class 3
Class 4
Drop precedence 1
low
001 01 0
010 01 0
011 01 0
100 01 0
Drop precedence 2
medium
001 10 0
010 10 0
011 10 0
100 10 0
Drop precedence 3
high
001 11 0
010 11 0
011 11 0
100 11 0
DSCP values For AF and EF PHBs

61
.DiffServ Domain
.A contiguous set of DiffServ nodes that have implemented the same PHB mechanisms and operate with a common service provisioning policy set
.All nodes in one DiffServ domain serve data streams in the same way
cloud-big
PHBPHB
PHB
DiffServ Domain

62
cloud-big
DiffServDomain Acloud-big
DiffServ
Domain B
cloud-big
DiffServDomain C
DiffServRegion
.DiffServ Region
.A set of one or more contiguous cooperating DiffServ domains.
.The DiffServ domains in a DiffServ region may support different PHB groups internally.
.Traffic conditioning is needed between such DiffServ domains.
DiffServ Region

63
.Per-Domain Behavior
.PDB is the expected treatment that a traffic aggregate will receive from edge to edge of a DiffServ domain.
.PDB can be seen as a service that is applied to flows through the domain.
.A specific PHB (or a group of PHBs) and traffic conditioning requirements in a DiffServ domain create PDB.
cloud-big
DiffServ
Domain A
PHB1
PHB2
PHB3
PDBcloud-big
DiffServDomain B
Per-Domain Behavior (PDB)

64
.Aggregation and de-aggregation of marked flows
.From aggregate to per-flow guarantees: how?
.end-to-end issues
.inter-domain SLA’s
.monitoring, dimensioning
.how much over-dimensioning?
.upper-layer protocol, (e.g., TCP), application performance
SLA
EN00637_[1]
j0285750
Challenges of DiffServ

65
Feature
IntServ
DiffServ
QoS assurance
Per-flow
Per-aggregate
QoS assurance range
End-to-end(application-to-application)
Domain(edge-to-edge) orDiffServ region
Resource reservation
Controlled by application
Configured at edge nodes based on SLA
Resource management
Distributed
Centralized within DiffServ domain
Signaling
Dedicated protocol (RSVP)
Based on DSCP carried in IP packet header
Scalability
Not recommended for core networks
Scalablein all parts of network
Class of Service
Guaranteed ServiceControlled Load ServiceBest Effort Service
Best Effort and a set of mechanisms for CoS design (EF and AF PHBs)
Comparison of IntServ & DiffServ

66
.Integrated IntServ-DiffServ Model
.IETF RFC 2998, 2000
.A Framework for Integrated Services Operation over DiffServ Networks
.Solid QoS guarantees of IntServ with the scalable architecture of DiffServ
.Features of IntServ-DiffServ Model
.Used to provide QoS in an end-to-end relation
.IntServ handles individual application flows in the access part
.Provide applications with mechanisms necessary to express the QoS requirements of each application
.DiffServ deals with large aggregates of IntServ microflows in the core
.Provides a user-network QoS signaling interface
.The QoS signaling is end-to-end.
Interoperability Framework for IntServ and DiffServ model

67
.Challenges of IntServ-DiffServ Model
.Dealing with numerous traffic flows across DiffServ sections
.Aggregate RSVP, RSVP DCLASS Object
.Aggregate RSVP
.Make a single reservation on behalf of a large number of individual flows across a DiffServ section
.RFC 3175, 2001.
.RSVP DCLASS Object
.Allow DSCPs to be carried in RSVP message objects
.RFC 2996, 2000
cloud-big
cloud-big
IntServ
in Access
DiffServin Core
Interoperability Framework for IntServ and DiffServ model

68
.MPLS
.Defined in L2 and L3
.Originally intended to simplify packet forwarding in routers rather than to address service quality
.Main role is TE and VPN support.
.MPLS QoS
.Facilitates offering IP QoS services via FR or ATM
.Plays a role in IP QoS
.DiffServ-aware TE
.Load balancing, flow control
.Explicit routing, tunneling, …
.But, different from those of IntServ and DiffServ
.IntServ and DiffServ network model are not dependent on Layer 2 techniques and define general QoS architecture for IP networks.
MPLS QoS

69
.MPLS QoS
.정의: MPLS를사용하여IP의여러서비스클래스를end-to-end로지원
.MPLS 네트웍을통해대역폭을보장하면서차등화된서비스를제공
.대역폭보장: MPLS Label을사용해서경로(LSP) 결정
.서비스차별화: EXP나MPLS Label을사용해서서비스클래스결정
.네트웍대역폭, 딜레이, 지터, 패킷로스와관렦된다양한기술을포함
cloud-big
ISP Customer
MPLS
Core Network
LER
MPLS QoS

70
MANServiceCustomerLERLERLSRLSRLSRCACCACCACCACCACPacketPacketClassificationCoS MarkingScheduleScheduleScheduleScheduleSchedulePacketPacketPacketShapingPacketShapingMPLS Sig
.Also called Hard QoS
.Used to describe a network that provides a QoS reservation at each network hop along an end-to-end path.
.The reservation is achieved using signaled CAC.
.Via a resource reservation protocol such as RSVP-TE or CR-LDP.
.Absolute QoS is achieved
.using the IntServto create the circuit path (LSP).
.using the DiffServ PSCsto provide the QoS service differentiation.
PSC : PHB Scheduling Class
Absolute QoS [MEF]

71
MANServiceScheduleCongestionMgmtScheduleCongestionMgmtScheduleCongestionMgmtScheduleCongestionMgmtScheduleCongestionMgmtPacketPcketPacketPacketCustomerPacketClassificationCoS MarkingBandwidth MgmtPacketLERLERLSRLSRLSR
.Also called Soft QoS.
.Used to describe a network that provides QoS via the IETF DiffServ architecture.
.Traffic conditioning may be performed using IP (DiffServ), Ethernet (802.1p/Q) or MPLS (EXP bits, LSP label).
Relative QoS [MEF]

72
.Why DiffServ-MPLS
.DiffServ가TE 기능을필요로함
.DiffServ-MPLS Features
.DiffServ 메커니즘과MPLS의TE를통합
.Mapping of DiffServ over a MPLS backbone
.IETF RFC 3270: MPLS Support of Differentiated Services
.draft-ietf-diff-te-reqts-06.txt : Requirements for Support of DiffServ-aware MPLS Traffic Engineering (work in progress)
.DiffServ의BA를TE 구조에포함시킴
.네트웍부하를최적화하면서BA의서비스파라미터특성을보장
Combination of MPLS with DiffServ

73
.DiffServ-MPLS Approach
.Map each DSCP (PHB) to an MPLS LSP
.One LSP per DiffServ PHB .LSP-inferred-PSC LSP
.MPLS 노드들은DS 필드를볼필요없이요구되는PHB를처리
.서로다른LSP는서로다른큐를사용
.Map a group of PHBs to an LSP
.다수의PHB를하나의LSP로그룹화시킴
.LSP 내의특정PHB를선택하기위해MPLS Shim 헤더의Exp 필드를사용
.EXP-inferred-PSC LSP
.하나의LSP 내에최대8개의PHB 수용가능
.동일LSP에속한클래스들은클래스별로다른큐사용
L-LSP and E-LSP .RC3270

74
.L-LSPs can be established by various label binding protocols
.LDP
.RSVP
.Example above illustrates support of EF and AF1 on separate L-LSPs
.Note: EF and AF1 packets travel on separate LSPs and are enqueued in different queues (different label values)
.Queues are selected based on Label,
.Discarding is based on ESP
L-LSPs
LSR
LDP/RSVPLDP/RSVP
EF
AF1
Example of L-LSP

75
.E-LSPs can be established by various label binding protocols
.LDP (Label Distribution Protocol)
.RSVP
.Example above illustrates support of EF and AF1 on a single E-LSP
.Note: EF and AF1 packets travel on a single LSP (single label) but are enqueued in different queues (different Exp values)
.Queues are selected based on Exp value
E-LSP
LSR
LDP/RSVP
LDP/RSVP
EF
AF1
Example of E-LSP

76
.Copy of IP Precedence into MPLS Exp
.Mapping of IP Precedence into MPLS Exp
Prec: xyz
IPv4 Packet
MPLS Header
Prec: xyzMPLS EXP:
xyz
Non-MPLS Domain
MPLS Domain
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Label | EXP |S|TTL |
E-LSP

77
QoS Metrics

78
.대역폭(Bandwidth)
.Sustained Data Rage (SDR) = Committed Data Rate (CDR) or Guaranteed Data Rate (GDR)
.Peak Data Rate (PDR)
.Minimum Data Rate (MDR)
.딜레이(Delay/Latency) .End-to-end / Round-trip Delay
.Serialization Delay = transmission delay
.해당링크의대역폭및패킷사이즈에의해좌우
.예) 1500-byte IP packet을10 Mbps 링크로젂송시: 1.2 msec
.Propagation Delay :
.한비트가Sender를떠나Receiver에도착하는데걸리는시갂
.Sender-Receiver 사이의거리와젂송매체에의해좌우
.예) 미국동서횡단딜레이= 30 msec
.Switching Delay
.어떤장치가패킷을받은후젂송하기시작할때까지걸리는시갂
.젂형적으로10 .s 이하.
.Jitter : delay variation
QoS Metrics -1

79
.싞뢰성(Reliability)
.Availability: Mean time between failures, Mean time to repair
.Error
.젂송및장비에서발생하는에러
.Packet Loss
.Buffer overflow에의한손실
.재젂송등에의한네트웍자원낭비
.Packet Order
.VoIP의경우숚서가뒤바뀌어도착한패킷은버려지기때문에패킷손실이발생한것과동일하게취급됨
MTTR MTBFMTBF
.tyAvailabili
Availability
MTTR
Three 9’s
99.9%
9 hours
Four 9’s
99.99%
1 hour
Five 9’s
99.999%
5 mins
Six 9’s
99.9999%
31 secs
QoS Metrics -2

80
.Measured for a Single Element not for the Entire System
.Measurement Interval
.Yearly-Based
.Monthly-Based
.Is Five 9’s yearly orFour 9’s monthly ‘better’?
.It depends on your consideration.
.If you are concerning about the total amount of downtime a year irrespective of the measurement interval, you may look at the average amount of allowable downtime.
.You may consider single failure regardless of ~, multiple failure를발생시키느냐..
Availability
Yearly-Based
Monthly-Based
99.99%
1 hour
4 min 19 sec
99.999%
5 min
26 sec
Availability 1

81
.In a Single component system
.The system availability is equal to the availability of the component.
.In a Multiple components system
.The system availability depends on the system configuration
.Serial or parallel
.Serial Connection
niAA
Availability 2

82
.How to Increase the Availability .Parallel Connection
.Components or network elements in parallel increase reliability
Availability 3

83
.Another Example of Parallel Connection
.Failure의해결
.In Circuit Switched Networks
.Redial or Retry to connection-setup
.In Packet Switched Networks
.Rerouting
Availability 4

84
.Time Sensitive and Mission-Critical Applications
.Requires high-level of QoS
.Examples
.Video Conferencing
.Video Streaming
.Video on Demand
.Voice/Video over Internet Protocol
.HD TV Broadcasting
.Storage
.Interactive Games
.Chatting
.IP VPNs
.…
Application Requiring IP QoS

85
.Latency는양방향Latency를의미한다.
.VoIP의경우ITU-T는단방향150 msec의딜레이를권고하고있다.
Bandwidth
Latency
Jitter
Loss
Errors
E-mail
Low
Low
Low
Low
Low
VoIP
Low
300 ms or less
50~100 ms
High ~Medium
High
VoD / Streaming
High
300 ms or less
50~100 ms
High ~Medium
High
Interactive
Games
Low
High
Medium ~ High
Low ~Medium
Low ~Medium
Storage
High
Medium ~ High
Low
High
Medium ~ High
Typical IP QoS Requirement

86
Requirement: “timely”delivery of multimedia data
.interactive multimedia: short delay, low loss
.e.g., IP telephony, teleconf., virtual worlds,
.excessive delay impairs human interaction
.streaming (non-interactive) multimedia:
.data must arrive in time for “smooth”playout
.late arriving data, loss, introduces gaps in rendered audio/video
.reliability:
.100% reliablity not always required
Multimedia Performance Requirements

87
QoS Functional Model

88
.It describes the required QoS functions
QoS Policy Management
QoS Signaling
QoS Routing
Classification
Marking
Bandwidth Control
Congestion Avoidance
Congestion Control
Directory & Policy Services
Admission Control
QoS Reservation
Constraint Based Routing
Layer 3 Marking
Layer 2 Marking
Shaping
Policing
Layer 4 Flow Control
Layer 2 Flow Control
Selective Discard
Queue Scheduling
Queue Buffers
Queues
Layer 4 Classification
Layer 3 Classification
Layer 2 Classification
Service Level Agreement
QoS Functional Model of MEF

89
.Data Plane QoS Operations
.Shaping
.Policing
.Queueing
.Scheduling
.Control Plane QoS Operations
.Resource provisioning
.Admission control
.Routing
Data vs. Control Plane Operation

90
H. Lu and I. Faynberg, “An Architectural Framework for Support of Quality of
Service in Packet Networks,” IEEE Commun. Mag., June 2003, pp.98~105.
Management Plane
Metering
Policy
Servicerestoration
SLA
Control Plane
Data Plane
Admissioncontrol
QoS
routing
Resourcereservation
Buffermanagement
Congestionavoidance
Packetmarking
Queueing andScheduling
Trafficshaping
Traffic
Policing
Traffic
Classification
QoS Building Block

91
.각노드(Edge>Core)에서QoS 구현을위해사용되는기술들
.Traffic Classification, Mapping (Re-Classification)
.Metering
.Marking and Remarking
.Flow Control
.Rate Limiting / Policing
.Queueing, Scheduling, Link Sharing
.Shaping / Smoothing
QoS Enabling Schemes

92
trafficstream
S/D IP Add, TCP/UDP
Port Num, ToS, …
Metering &
Marking
tr_TCM, DSCP
Flow control &
Limiting/Policing
WRED/SARED
WFQ
Scheduling &Link Sharing
trafficstream
Classification& Mapping
Mapping
Packet rewriting
Shaping &
Flow control
QoS Architecture in a Node

93
Classify
Police
Forwarding Engine
Queue
RX
Input
Port
Priority Q
ARB
802.1p, 802.1q, 기타Packet
DSCP Based
Classification
.Layer 2 info w/ ACL
.Layer 3 info w/ ACL
.Layer 4 info w/ ACLBA Classifying
PolicingPolice Action:
.Mark
.DropBased on:
.Byte rate
.Burst(Token Bucket)
Queue 1Priority Q
WRR
Rewrite
TX
Output
PortQueue 2
ARB
Rewrites TOS
Field in IP
Header and
802.1p CoS
Field
Each Queue
Has
Configurable Size and
Thresholds,
Some Have
WRED
Out-Going
Encapsulation Can be
802.1Q, ISL,
(or None)
Scheduling:
Queue and
Threshold
Select Based
on CoS
Through
Configurable
Map
Dequeueing
Uses WRR
between Two
Queues
스케줄링Queue, Threshold 선택
DiffServ QoS Architecture

94
Flow별Metering, Marking
and Policing/Shaping
Classification/
Reclassification
Queue Manager
.Traffic Control
Queue
Scheduler
Queue
Manager
Meter
Marker
Meter
Marker
Meter
Marker
f1a
f1b
fnm
Shaper/Policer
Shaper/Policer
Shaper/Policer
BWPriority
…
GbE uplink
1Mbps
5Mbps
100M link
Customer 1
100M link
Customer n
Queue 2
Queue 1
Queue 4
Queue 3
Queue
Manager
GbE uplink
1Mbps
5Mbps
Queue 2
Queue 1
Queue 4
Queue 3
Classifier (Implicit, Explicit)
Classifier (Explicit)
High
Low
Edge node
Core node
Edge 및Core 노드에서의QoS 구조비교

95
NP
PHY
Framer
TM
SW
Fabric
SPI-4
SPI-4
Host CPU
PCI
SPI-4
SPI-4
SerDes, CSIX, or SPI-4.2
Addressing, Classification,
Statistics, Policing
Queueing, Flow Control,
Shaping, Scheduling
QoS 장비의구조

96
NP
PHY
Framer
TM
TM
SW
Fabric
SPI-4
SPI-4
SPI-4
Host CPU
PCI
QoS 장비의구조

97
NP
PHY
Framer
TM
SW
Fabric
SPI-4
SPI-4
Host CPU
PCI
NP
SPI-4
SPI-4
Packet modification,
mapping, VLAN tagging
QoS 장비의구조

98
NP
PHY
Framer
TM
SPI-4
SPI-4
Host CPU
PCI
SPI-4
SPI-4
SW
Fabric
QoS 장비의구조.Pizza Box Type

99
NP
PHY
Framer
TM
SPI-4
SPI-4
Host CPU
PCI
NP
SPI-4
SPI-4
QoS 장비의구조.Pizza Box Type

100
Classification

101
.Packet Classification
.To identify packets to be of a certain class based on one or more fields in a packet
.Classify packets into groups with the same or similar QoS metrics
.Packets in a group are treated equally.
.Performed in Edge Routers.
.Core Routers use the result of classification in order to perform high-speed switching/routing.
.Why Packet Classification is Required?
.Simplify QoS schemes by handling all the traffic with the same or similar QoS requirements together.
.Criteria of Packet Classification
.Network internal criteria : MAC Add, IP Add, Port Num, etc.
.Network external criteria : Subscriber, Service type, etc
Packet Classification

102
C:\\Documents and Settings\\Hakyong Kim\\Application Data\\Microsoft\\Media Catalog\\Downloaded Clips\\cl1f\\j0078762.wmf
C:\\Documents and Settings\\Hakyong Kim\\Application Data\\Microsoft\\Media Catalog\\Downloaded Clips\\cl4a\\j0186180.wmf
C:\\Documents and Settings\\Hakyong Kim\\Application Data\\Microsoft\\Media Catalog\\Downloaded Clips\\cl33\\j0128339.wmf
VoiceVideoData.
Packet Classification의개념

103
Core network treats packets of QoS Group 3 preferably.
Packet Classification예제

104
.First Stage of Packet Classification
.If there is no class, then use a single class of best-effort
.Examples of Class Generation
.Gold, Silver, Bronze, (Other or BE)
.High, Medium, Low, (Other or BE)
.Premium, Normal, (Other or BE)
.CBR, VBR, VBR+, ABR, UBR (In case of ATM)
.EF, AFx, BE (In case of DiffServ)
.Committed, Premium, Business, Standard (In case of DiffServ)
.Relation among Classes
.No absolute, no strict relation
.A traffic class is for a specific type of traffic.
Generation of Classes

105
어떤가입자?
어떤어플리케이션?
도착하는트래픽
Classification은사용자인증과인증된사용자로부터의트래픽에
대한분류를포함하는개념이다.
Classification의범위

106
.L2 Classification
.Source/Destination MAC Address (6B)
.EtherType or Length field (2B)
.802.1p/Q priority field (3b)
.VLAN ID (12b)
.MPLS label (20b) or EXP bits (3b)
.L3/4 Classification
.Destination IP Address
.Source IP Address
.Protocol Field
.Destination Port Number
.Source Port Number
.Type of Service (ToS) Field
.DSCP Field
.L5~L7 Classification
.Application Specific
.Server-side QoS .Network-side QoS (L2 and L3/4)
5 tuple : specify a specific flow
Types of Classification

107
S
1b
Destination MAC
Source MACFCS
Type/Length
IP Datagram
Ethernet Format (DIX 2.0/IEEE 802.3)
6B
6B
2B
4B
IEEE 802.1p/Q Format and VLAN ID
Destination
MAC (6B)
Source
MAC (6B)
TPID(2B)
CFI(1b)
VLANID(12b)
Type(2B)
Data
FCS(4B)
Pri(3b)
MPLS over Ethernet Format
Type(2B)
TTL(8b)
Type(2B)
IP Datagram
FCS(4B)
Exp(3b)
Label(20b)
Dst.MAC
SrcMAC
DstMAC
SrcMAC
QoS information is Tagged onto L2 MAC frame.
L2 MAC Frame Format

108
.TPID : Tag Protocol Identifier
.PRI : CoSfield
.CFI : Canonical Format Identifier“Canonical Format” 이란구체적으로Ethernet/802.3 포맷을말한다.
.VID : Virtual LAN Identifier12 bit 로1 ~ 4094 를사용할수있다
“0”인경우Null Frame 으로CoS정보를젂달한다.
Tag 정보필드
IEEE 802.1p (CoS)

109
Network control
RFC 2815
Mapping Service to 802.1p

110
0
Ver
H.Len
Type of Service
Total Length
Identification
Fragment Offset
Flags
Time To Live
Protocol
Header Checksum
Source IP Address
Destination IP Address
Padding
IP Options
4
8
16
19
24
31
Data
IP Packet Format (L3)

111
Type of Service
D
U
T
R
C
Prec
IP Prec
value
Name
0
routine
1
priority
2
immediate
3
flash
4
flash-override
5
critical
6
internet
7
network
IP Precedence Field
.Precedence (3b) : classify a packet
into 8 priority levels (RFC791)
Service Profile Selector Field
.D : Minimize Delay
.T : Maximize Throughput
.R : Maximize Reliability
.C : Minimize Cost
.U : Unused (MBZ: Must Be Zero)
.RFC 1349 .Type of Service in the
Internet Protocol Suite.
.DTR .DTRC after RFC1349.
Type of Service (ToS) Field

112
.Newly define the IP ToS Field
.DSCP field (6b) + CU field (2b)
.DS Field : 8 bits
.Used to select PHB
.Replace IPv4 ToS or IPv6 Traffic Class
.DSCP(DiffServ Code Point) Field : 6 bits
.64 DSCPs
.xxx000 : backward compatible with IP Precedence (code selector)
.32 DSCPs are reserved by IETF to map to standard PHBs.
.xxxxx0
.remaining 32 DSCPs are used for local use or experimental use.
DSCP
CU
D
Prec
U
T
R
C
DS Field
DSCP Field
DiffServ Field

113
Mapping

114
.What is Mapping?
.To correlate the priority of packets, priority of classes, or service priority among different layers, different protocols, or different service domains.
.Why Mapping is Required?
.To maintain a consistent characteristics of the traffic pass through different layers, different network protocols, or different service domains.
.Types of Mapping
.L2-L3 Mapping
.CoS to ToS, CoS to DSCP, MPLS to DiffServ Mapping
.L3-L3 Mapping
.ToS to DSCP, DSCP to ToS
.L3-L2 Mapping
.ToS to CoS, DSCP to CoS, DiffServ to MPLS mapping
Mapping

115
L3 .L3 Mapping
DSCP .CoS
DSCP
CoS
L3 .L2 Mapping
Mapping
Mapping Table Example

116
IP Prec.
DSCP(BE)
IP Precedence and DSCP

117
cloud-big
IP Prec
DSCP
인터넷
DiffServ 네트웍
IP Prec
DSCP
IP Prec .DSCP 매핑의예
Mapping Example -1

118
cloud-big
cloud-big
7
다른네트웍/서브넷과다른우선숚위체계를사용하고있을때, 일정한서비스수준을유지해주기위해두네트웍사이의우선숚위를서로연관지어줄필요가있다.
3
priorityvaluehighest7654321lowest0
priorityvaluehighest321lowest0PC
Mapping Example -2

119
Ethernet Services Network
Classification
Marking
Bandwidth Control
customer
802.1p -to-DSCP OR
802.1p -to-MPLS EXP
DiffServ PHB
QoS Policy Management
QoS Signaling
QoS Routing
DSCP -to-802.1p OR
MPLS EXP -to-802.1p
Access
CORE
Access
customer
Big Picture of Mapping

120
GEANT Project의사례
Service Incoming DSCP value New value (rewritten)
Authorized Premium IP 46 46/drop (*)
Un-authorized Premium IP 46 0/5 (**)
DWS 32 0
Less than Best Effort 8 8
Network Control 48/56 48
Best Effort Other values Unchanged
서비스클래스에대한DSCP 및ToS 값
Packet remarking rule
Service DSCP value TOS value Juniper Alias ToS in HD DSCP-TOS Binary
Premium IP 46 184 ef B8 101110 . 101110xx
Less than BE 8 32 cs1 20 001000 . 001000xx
DWS 32 128 cs4 80 100000 . 100000xx
Network Ctrl 48 192 cs6 C0 110000 . 110000xx
Network Ctrl 2 56 224 cs7 E0 111000 . 111000xx

121
.MPLS TE and DiffServ
.방법1: Label과EXP field에DSCP를mapping 한다(Label-inferred LSP)
.방법2: EXP field에DSCP를mapping 한다(EXP-inferred LSP)
Label(20bits)
EXP(3bits)
Policing/Marking
Queueing
Scheduling
Next-hop
Context
QoS
Context
Label(20bits)
EXP(3bits)
Policing/Marking
Queueing
Scheduling
Next-hop
Context
QoS
Context
Label-inferred LSP
EXP-inferred LSP
MPLS-TE and DiffServ Mapping

122
Metering and Marking
(Traffic Conditioning)

123
.Metering
.입력되는IP 트래픽스트림의트래픽특성을측정
.기정의된트래픽프로파일과측정결과를비교
.Marking
.Metering 결과에따라패킷을서로다른우선숚위로표시
.DiffServ에서는Green, Yellow, Red로표시
.Metering과Marking은각클래스에대해이루어짂다!!
Meter
Marker
Packet Stream
Marked
Packet Stream
Metering Result
Metering과Marking을합해Traffic Conditioning이라한다.
Metering and Marking -1

124
.Metering과Marking의필요성
.입력되는트래픽이약속된트래픽프로파일을따르는지를확인
.트래픽프로파일에대한숚응여부를바탕으로차별화된서비스제공을위한근거마렦
.Marking
.패킷의우선숚위는패킷헤더의DS(or DSCP) 필드의4-5번째비트에설정됨
.Green : xxx010 .혺잡시드랍될확률이가장낮다. (drop precedence is low)
.Yellow : xxx100
.Red : xxx110 .혺잡시드랍될확률이가장높다. (drop precedence is high)
.RFC2697 .A Single Rate Three Color Marker
.RFC2698 .A Two Rate Three Color Marker
.RFC2859 .A Time Sliding Window Three Colour Marker (TSWTCM)
.RFC2963 .A Rate Adaptive Shaper for Differentiated Services
Metering and Marking -2

125
.Metering Methods
.Average rate
.Exponential Weighted Moving Average (EWMA) .Queue Size
.Also used in RED / WRED
.Average interval
.Rate estimator (RFC 2859, TSW-TCM)
.Token Bucket
.Single-stage Token Bucket
.Multi-stage Token Bucket
.Metering Result differs
.from different metering algorithms
.from different metering parameters
CKAKAii**)1(1....
Metering Algorithms