datatag wp2 ip quality of service architectures issues and proposals

20/06/2002 Valentina Capaccio

DataTAG WP2DataTAG WP2IP Quality of Service IP Quality of Service

ArchitecturesArchitecturesIssues and ProposalsIssues and Proposals

Valentina CapaccioValentina Capaccio

DataTAG MeetingDataTAG Meeting

Amsterdam - June 20, 2002Amsterdam - June 20, 2002


AgendaAgenda Towards QoSTowards QoS

IP QoS frameworksIP QoS frameworks IntservIntserv

DiffservDiffserv

Intserv/DiffservIntserv/Diffserv

Admission ControlAdmission Control Centralized ApproachCentralized Approach

Distributed ApproachDistributed Approach

Policy – Based Network ManagementPolicy – Based Network Management

Possible architecture and its interaction Possible architecture and its interaction with GARAwith GARA

Conclusions Conclusions


Internet QoSInternet QoS

Best - Effort ServiceBest - Effort Service

It can be suitable for traditional It can be suitable for traditional Internet applicationsInternet applications

e.g.,file transfers, web browsing, e-e.g.,file transfers, web browsing, e-mailmail

Certainly unsuitable for emerging Certainly unsuitable for emerging applications !applications !

e.g., IP telephony, audio and video e.g., IP telephony, audio and video streaming, multimedia conferencingstreaming, multimedia conferencing


IETF SolutionsIETF Solutions

Integrated Services Architecture Integrated Services Architecture [RFC1633][RFC1633]

a revolutionary approacha revolutionary approach attempts to transform IP network in a attempts to transform IP network in a reservation-based network reservation-based network

per-flow philosophyper-flow philosophy

Differentiated Services Architecture Differentiated Services Architecture [RFC2475][RFC2475]

an evolutionary approachan evolutionary approach pushes all the complexity to the edge of pushes all the complexity to the edge of the networkthe network

per-aggregate philosophyper-aggregate philosophy


Intserv ArchitectureIntserv Architecture

IS (Integrated Services) Model IS (Integrated Services) Model to extend the current Internet to extend the current Internet service modelservice model

Reference Implementation Reference Implementation FrameworkFramework

to realize the IS modelto realize the IS model

Architectural model comprised of Architectural model comprised of twotwo elements: elements:


IS ModelIS Model(three service classes specified)(three service classes specified)

Tspec = Traffic specification Tspec = Traffic specification Rspec = Reserve specification Rspec = Reserve specification

Tspec, Rspec

-Assured level of bandwidth-Mathematically bounded end-to-end delay-No queuing losses for conforming packets

Guaranteed delayservice

Tspec

- QoS achieved: similar to that achievable by best-effort

traffic in an unloaded

network

Controlled Load service

Best Effortservice

RSVP’s definitionsRSVP’s definitions


IS Reference IS Reference Implementation Implementation

FrameworkFramework FourFour components: components:

Packet schedulerPacket scheduler ClassifierClassifier Admission control routineAdmission control routine

Traffic Traffic Control Control

MechanisMechanismsms

Reservation setup protocolReservation setup protocol


RSVP/Intserv RSVP/Intserv Reservation Model Reservation Model

• A reservation request is identified by A reservation request is identified by the couplethe couple

FlowspecFlowspec FilterspecFilterspec

““Flowdescriptor”Flowdescriptor”

Identifies the set of data packets

Specifies the desired QoS


Intserv FlowspecIntserv Flowspec

Flowspec is made up of :Flowspec is made up of : Tspec ( Controlled Load Service)Tspec ( Controlled Load Service) Tspec, Rspec ( Guaranteed Service )Tspec, Rspec ( Guaranteed Service )

Tspec takes the form of a token bucketspecification plus other parameters:

Rspec is identified by: - a rate R

- a slack term SThe Rspec terms (R,S)are selected to obtain:

- the desired bandwidth- delay guarantees

b

rr - token bucket rater - token bucket rateb - token bucket sizeb - token bucket sizep - peak ratep - peak rateM - maximum datagram sizeM - maximum datagram sizem - minimum policed unitm - minimum policed unit


RSVP approachRSVP approachSoft States , Receiver - Soft States , Receiver -

OrientedOriented

PATH provides information about Sender_Tspec creates PATH states in routers carries routers info (Adspec) to Receiver

PATH

RESV

RESV in each router, if request can be accepted, creates a RESV stateupdates Packet Classifierupdates Packet Scheduler

Sender

Receiver

PATH & RESV statesstated in routers

need a periodical refreshotherwise expire!


Critics to RSVPCritics to RSVP ScalabilityScalability

Each reservation requires a non-trivial amount of Each reservation requires a non-trivial amount of message exchange, computation and memory message exchange, computation and memory resources in each router resources in each router

many soft states must be periodically refreshedmany soft states must be periodically refreshed many individual queues must be managed by a schedulermany individual queues must be managed by a scheduler

Back CompatibilityBack Compatibility requires intra – routers communication requires intra – routers communication agreementagreement

different vendors must intercommunicate with different vendors must intercommunicate with

fixed standardfixed standard

requires a router – centric approachrequires a router – centric approach

intelligenceintelligence gets concentrated in intermediate gets concentrated in intermediate systemssystems


Diffserv ArchitectureDiffserv Architecture

Which QoS need ?Which QoS need ? ISPs want finer control of “relative” allocated ISPs want finer control of “relative” allocated

traffic, expecially under heavy loadtraffic, expecially under heavy load to provide a “better” service to some trafficto provide a “better” service to some traffic

Which QoS solution ?Which QoS solution ? to push the complexity to the network edgesto push the complexity to the network edges to force all per-flow work to the edgesto force all per-flow work to the edges

Very simple semantic !Very simple semantic ! packet label differentiationpacket label differentiation


Differentiated Services Differentiated Services Code PointCode Point

DSCP CU

VERSION IHL TOS TOTAL LENGTH

IDENTIFICATION FRAGMENTOFFSET

TIME TO LIVE PROTOCOL HEADER CHECKSUM

SOURCE ADDRESS

DESTINATION ADDRESS

6 bit 2 bit

FLAGS

IPv4 HeaderIPv4 Header


Basic Diffserv ModelBasic Diffserv Model

Scalability Scalability : : intelligenceintelligence at the at the edgeedge of the network !of the network !

ReceiveReceiversrs

Edge Edge RouterRouter

ISP ISPSendersSenders

-Classification- Traffic Conditioning

Core Core NetworkNetwork


Diffserv Building Diffserv Building BlocksBlocks

PHBPHB the externally observable forwarding behavior the externally observable forwarding behavior

applied at each DS node to a traffic aggregateapplied at each DS node to a traffic aggregate

ServiceService composition of PHBscomposition of PHBs

DSCPDSCP mapped into a PHB in a given domainmapped into a PHB in a given domain

SLASLA service contract agreement between service contract agreement between

customer and domain or intra - domain. It customer and domain or intra - domain. It specifies the forwarding service a customer specifies the forwarding service a customer should receive.should receive.


TCA TCA (Traffic Conditioning (Traffic Conditioning

Agreement)Agreement) Specifies classifying rules and metering, Specifies classifying rules and metering, marking, discarding and/or shaping rulesmarking, discarding and/or shaping rules

to be applied to the traffic streamto be applied to the traffic stream

Classifier MarkerShaper/Dropper

Meter

packetpacketss


Critics to DiffservCritics to Diffserv

Lack of a Lack of a signallingsignalling mechanism mechanism to convey the status of core routers to the to convey the status of core routers to the

end points end points to take to take learned learned admission control admission control decisionsdecisions

Static forms of admission control applying Static forms of admission control applying provisioning policies at network elementsprovisioning policies at network elements if they do protect the network to some if they do protect the network to some

degreedegree they can be quite they can be quite ineffectiveineffective ! !


Complementary Complementary Approaches !Approaches !

[RFC2998] and [RFC2990] recognize that:[RFC2998] and [RFC2990] recognize that: both IntServ and DiffServ architectures have both IntServ and DiffServ architectures have some some

critical elements in terms of their current definitioncritical elements in terms of their current definition which appear to be acting as which appear to be acting as deterrents to widespread deterrents to widespread deploymentdeployment,,

there appears to be no single comprehensive service there appears to be no single comprehensive service environment that possesses environment that possesses both service accuracy and both service accuracy and scaling propertiesscaling properties,,

further refinement of the QoS architecture is required further refinement of the QoS architecture is required to to integrate DiffServ network services into an end-to-integrate DiffServ network services into an end-to-end service delivery model with the associated task of end service delivery model with the associated task of resource reservationresource reservation,,

it is then suggested to define it is then suggested to define an admission control an admission control function which can determine whether to admit a function which can determine whether to admit a service differentiated flowservice differentiated flow along a nominated network along a nominated network path.path.


Reference Framework Reference Framework [RFC2998][RFC2998]

RSVP is used as an RSVP is used as an “explicit setup mechanism”“explicit setup mechanism” to improve the service the network provides to to improve the service the network provides to applicationsapplications

If Diffserv Border Routers are RSVP-aware If Diffserv Border Routers are RSVP-aware admission control is admission control is part part of the Diffserv regionof the Diffserv region

changes in the capacity available in the changes in the capacity available in the Diffserv region are Diffserv region are signalled outsidesignalled outside via RSVP via RSVP

SenderSenderReceiverReceiver

Access Access Network Network DomainDomain

Access Access Network Network DomainDomain

DiffServ Domain

ER1 BR1 BR2 ER2

PATHPATH PATHPATHRESVRESV RESVRESV

Admission control Admission control

processingprocessing


Resource Management in Resource Management in DiffservDiffserv

Two possible approaches to Two possible approaches to dinamically provisiondinamically provision resources in resources in Diffserv region and to take Diffserv region and to take admission admission control decisionscontrol decisions Centralized Approach (traditional)Centralized Approach (traditional)

use of a use of a Bandwidth BrokerBandwidth Broker that has that has sufficient knowledge of resource sufficient knowledge of resource availability and network topology availability and network topology

Distributed Approach (evolutionary)Distributed Approach (evolutionary) Endpoint Admission Control (EAC)Endpoint Admission Control (EAC) based based on a pure end-to-end operation involving on a pure end-to-end operation involving only the source and destination host.only the source and destination host.


Bandwidth Broker Bandwidth Broker Functional BlocksFunctional Blocks(QBone approach)(QBone approach)

Inter-DomainInter-Domain

Intra-DomainIntra-Domain

User/AppUser/AppIfaceIface

Diffserv Border Diffserv Border RouterRouter

Diffserv Border Diffserv Border Router Router

Adjacent Adjacent BBBB

Adjacent Adjacent BBBB

ApplicatiApplication Serveron Server

UserUser/ /

hosthost

Network Network OperatorOperator

Data Data StoreStore

RoutingRoutingInfoInfo

““Simple”Simple”PolicyPolicy

ServicesServices

- SLA information- SLA information- Current reservations- Current reservations- Resource allocations- Resource allocations- Configurations for - Configurations for

routersrouters- Service mapping- Service mapping- DSCP mapping- DSCP mapping

- Policy information- Policy information- Authorization and - Authorization and

authenticationauthenticationdatabase database

for users and peersfor users and peers


Endpoint Admission ControlEndpoint Admission Control

Basic Principle: use lack of timely response to Basic Principle: use lack of timely response to estimate congestion status of the networkestimate congestion status of the network

SourceSource

DestinationDestination2

ACKACK

DATADATA 3

PROBINGPROBING1

Destination host monitors Destination host monitors probing packets statistics probing packets statistics for a given period of timefor a given period of time


GGauge&Gate auge&Gate RReservation with eservation with IIndependent ndependent PProbing (GRIP)robing (GRIP)

SourceSource

DestinationDestination

PROBINGPROBING1

DATADATA 3

2ACKACK

GRIP:Measure & DecisionGate open or closed

Implicitly Implicitly convey signalling informationconvey signalling information via via loss of packetsloss of packets

Drive packet losses on the basis of run-time Drive packet losses on the basis of run-time measurements measurements locally takenlocally taken by each network by each network routerrouter

II

DD

EE

AA

(Bianchi-Blefari Melazzi)(Bianchi-Blefari Melazzi)


Towards a Policy-Based Network Towards a Policy-Based Network ArchitectureArchitecture

No explained architecture allows to make No explained architecture allows to make reservation in advance !reservation in advance !

[RFC2753] recognizes that:[RFC2753] recognizes that: Network managers and service Network managers and service

providers must be able to providers must be able to monitormonitor, , control control and and enforceenforce use of network use of network resources on the basis of resources on the basis of fixed policiesfixed policies derived from criteria such asderived from criteria such as

• identity of users and applicationsidentity of users and applications• traffic/bandwidth requirementstraffic/bandwidth requirements• time of day/weektime of day/week• security considerationssecurity considerations


Basic Policy-Based Basic Policy-Based ArchitectureArchitecture

Policy Enforcement Points (PEP)

PolicyManagement

Console

PolicyRepository

LDAP

COPS

LDAPDirectory

SNMP

Policy Decision

Point

Policy Decision

Point

Policy Proxy

Path of traffic flow


Architecture Architecture ComponentsComponents

Directory Directory Directory stores a variety of Directory stores a variety of informationinformation User dataUser data

•Authentication and access rightsAuthentication and access rights•User profilesUser profiles

Infrastructure dataInfrastructure data•Static/start-up configuration for devices Static/start-up configuration for devices (e.g., routers, switches)(e.g., routers, switches)

•Server information (e.g., name server)Server information (e.g., name server) PoliciesPolicies

•Conditions, actions, policy rules (time of Conditions, actions, policy rules (time of day/week, identity of users, etc.)day/week, identity of users, etc.)


Architecture ComponentsArchitecture ComponentsPolicy ConsolePolicy Console

Policy consolePolicy console Provides an abstraction of rules to Provides an abstraction of rules to

create policiescreate policies It is used to define and edit policiesIt is used to define and edit policies Validates policiesValidates policies When appropriate, the policy UI is When appropriate, the policy UI is

unified with the UI that manages the unified with the UI that manages the entities that are the subjects of the entities that are the subjects of the policy (e.g., users, computers, policy (e.g., users, computers, devices)devices)


Architecture ComponentsArchitecture ComponentsPolicy Decision PointPolicy Decision Point

PDP PDP that generally takes the form that generally takes the form of a of a policy serverpolicy server Makes policy selection getting Makes policy selection getting

policy from an LDAP-based directorypolicy from an LDAP-based directory Makes policy decisionsMakes policy decisions Returns the final policy decisions Returns the final policy decisions

based on admission control request based on admission control request to policy enforcement pointto policy enforcement point


Architecture ComponentsArchitecture ComponentsPolicy Enforcement PointPolicy Enforcement Point

Policy Enforcement Point Policy Enforcement Point (installed (installed in a router)in a router) Upon receiving a notification that Upon receiving a notification that

requires a policy decision,requires a policy decision, formulates a request and sends it formulates a request and sends it to PDPto PDP

Optionally caches policy decisions for Optionally caches policy decisions for future usefuture use

Processes traffic per policy decisionProcesses traffic per policy decision Relays events to Policy Decision PointRelays events to Policy Decision Point


RSVP-aware RSVP-aware networknetwork

Differentiated Differentiated service service

network(s)network(s)


GARA GARA ResourceResourceManagerManager

A Possible ArchitectureA Possible Architecture(setup phase)(setup phase)

RSLRSLRSVP RSVP

requesrequestt

ReceiveReceiverr

COPCOPSS

LDAPLDAP

COPSCOPS

LDAPLDAPCOPSCOPS

LDAPLDAP

Foreground Reservation Foreground Reservation Guaranteed Guaranteed ServiceService

Backgroung Reservation Backgroung Reservation Controlled Controlled LoadLoad


A Possible ArchitectureA Possible Architecture(allocation phase)(allocation phase)


Differentiated Differentiated service service

network(s)network(s)


GARA GARA ResourceResourceManagerManager

RSVP RSVP answeanswe

rr

ReservatiReservation is on is OK !OK ! Two possible approaches:Two possible approaches:

(1)(1)A “simplified” BBA “simplified” BB(2)(2)EAC algorithmsEAC algorithms


Architecture for Resource Co-Architecture for Resource Co-Allocation (DataGRID – D1.4)Allocation (DataGRID – D1.4)

Upon receiving the answer from the network, Upon receiving the answer from the network, the Resource Manager notifies the result of the the Resource Manager notifies the result of the reservation request to the Reservation Agentreservation request to the Reservation Agent

ReservationReservation AgentAgent

ResourceResourceBrokerBroker

InformationInformationSystemSystem

ResourceResourceManagerManager

Logging &Logging &BookkeepingBookkeeping

Answer Answer from the from the networknetwork


If reservation “in If reservation “in advance”advance”

GARA network resource managerGARA network resource manager Performs the mapping : RSL string Performs the mapping : RSL string RSVP RSVP

requestrequest Informs the PDPs that an advance reservation Informs the PDPs that an advance reservation

is requested (it behaves like a Policy Console)is requested (it behaves like a Policy Console) If reservation is successful,If reservation is successful,

Informs the PDPs that reservation was Informs the PDPs that reservation was successful and this information will be successful and this information will be communicated to LDAP-directories by PDPscommunicated to LDAP-directories by PDPs

Notifies the Reservation Agent (RA) that Notifies the Reservation Agent (RA) that reservation was successfulreservation was successful

An appropriate DSCP will be An appropriate DSCP will be boundedbounded for for the traffic flow that requires reservation in the traffic flow that requires reservation in advanceadvance


If “immediate” If “immediate” reservationreservation

GARA network resource managerGARA network resource manager Performs the mapping : RSL string Performs the mapping : RSL string RSVP requestRSVP request

Forwards the request to the networkForwards the request to the network If reservation is successful,If reservation is successful,

Notifies the Reservation Agent (RA) Notifies the Reservation Agent (RA) that reservation was successfulthat reservation was successful

A DSCP will be assigned to this A DSCP will be assigned to this reservation only if the total amount of reservation only if the total amount of bandwidth for that class has not been bandwidth for that class has not been reserved by a reservation in advancereserved by a reservation in advance


Admission Control in Admission Control in Diffserv Region Diffserv Region

Resources for Advance Reservations are Resources for Advance Reservations are allocated bounding DSCPs allocated bounding DSCPs

Reservations can be subjected to EAC (e.g., Reservations can be subjected to EAC (e.g., implementing GRIP) to implement a implementing GRIP) to implement a dynamic resource provisioningdynamic resource provisioning

A DSCP will be assigned to an Immediate A DSCP will be assigned to an Immediate Reservation only if the total amount of Reservation only if the total amount of bandwidth for that class was not allocated bandwidth for that class was not allocated for reservations in advancefor reservations in advance

Mapping :Mapping : Foreground Reservation Foreground Reservation EF PHB EF PHB Background Background Reservation Reservation AF PHB AF PHB


Conclusions Conclusions

It is necessary a complex and articulate QoS It is necessary a complex and articulate QoS architecture to satisfy all the needs of architecture to satisfy all the needs of network managers and service providersnetwork managers and service providers

Existing QoS architectures do not support Existing QoS architectures do not support advance reservation and it is necessary to advance reservation and it is necessary to introduce an additional external mechanismintroduce an additional external mechanism

A lot of explained aspects are actually under A lot of explained aspects are actually under investigation investigation

Interaction with GARA architecture to map a Interaction with GARA architecture to map a RSL string into a RSVP request must be RSL string into a RSVP request must be clearer definedclearer defined

datatag wp2 ip quality of service architectures issues and proposals

Documents

better service

ip network

model architectural

reservationbased network

integrated services

network edges

qos need

qos solution