datatag wp2 ip quality of service architectures issues and proposals
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DataTAG WP2 IP Quality of Service Architectures Issues and Proposals. Valentina Capaccio DataTAG Meeting Amsterdam - June 20, 2002. Agenda. Towards QoS IP QoS frameworks Intserv Diffserv Intserv/Diffserv Admission Control Centralized Approach Distributed Approach - PowerPoint PPT PresentationTRANSCRIPT
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
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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
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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
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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
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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:
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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
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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
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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
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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
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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!
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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
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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
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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
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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
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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.
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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
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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 ! !
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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.
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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
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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.
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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
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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
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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)
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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
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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
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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.)
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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)
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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
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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
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RSVP-aware RSVP-aware networknetwork
Differentiated Differentiated service service
network(s)network(s)
RSVP-aware RSVP-aware networknetwork
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
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A Possible ArchitectureA Possible Architecture(allocation phase)(allocation phase)
RSVP-aware RSVP-aware networknetwork
Differentiated Differentiated service service
network(s)network(s)
RSVP-aware RSVP-aware networknetwork
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
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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
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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
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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
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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
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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