advanced traffic management qos concepts 319
TRANSCRIPT
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Advanced TrafficAdvanced TrafficManagement and QoSManagement and QoS
ConceptsConceptsSession 319Session 319
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IntroductionIntroduction
Traffic Management
Applications and Transports
So what Are the Issues forTCP
Voice on IP
Video (Broadcast and Teleconferencing)
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Let's Talk about TrafficLet's Talk about TrafficManagementManagement
Why it is a concern
What the guiding principles are
What tools are available
What can be accomplished usingthose tools
What cannot be accomplished
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Why Traffic ManagementWhy Traffic ManagementIs a ConcernIs a Concern
Needs of certain applicationsMail? Web? Transaction processing?
Opportunities with certain transports
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Guiding Principles forGuiding Principles forTraffic ManagementTraffic Management
We want to achievePredictability
Reliability
Availability
In a network thatKeeps intelligenceat the edges
Scales to necessarysizes andbandwidths
Minimizescomplexity
Uses cost-effectivetechnologies
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What Tools Are Available forWhat Tools Are Available forTraffic ManagementTraffic Management
Traffic path control
Queue depth management
Queue rate management
Permission to use a link
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How Well Will TrafficHow Well Will TrafficManagement Do?Management Do?
We know we can do this:Management of latency
Management of bandwidth
What cannot be accomplishedCreation of bandwidth that otherwisewould not be there
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Source: Gartner Group Study, March 1997
WAN ProtocolBreakdown
WAN ProtocolBreakdown
1994 1996 1998E 2000E 2002E
80%70%60%50%40%30%20%10%0%
IP SNA IPXOthers RFC 1490
IP
Primarily a WAN IP TalkPrimarily a WAN IP Talk
IP is the dominantinternet protocol
TCP is the dominantdata transport
95% of Internet trafficuses TCP
Voice is a growingmarket
But beware of hype
Heterogeneouslink layers
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Making NetworksMaking NetworksPredictablePredictable
The GrailThe Grail
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This Is what You NeedThis Is what You Needto Understand:to Understand:
TCP-based applications, voice,and video can be managed wellwith a little planning
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Parekh and Gallaghers PaperParekh and Gallaghers Paper
INFOCOMM 93
One must have at most a predictablepredictableamount of traffic in the network
One must have predictablepredictable trafficdelay in each network element
Given these, end-to-end delayend-to-end delay of ahost to host message is predictableis predictable
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Definition of PredictableDefinition of Predictable
Does not meanFixed, Invariant, or Zero
Means that it has aMean value
Statistical distribution
Upper bound
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Predictable Amount of TrafficPredictable Amount of Trafficin the Networkin the Network
The source must pace trafficinitiation so that standing queuesare bounded
Queues form when arrival rate exceedsdeparture rate
When congestion (too manymessages in one queue) sets in:
Sources must not increase their rateIdeally, sources decrease their rate
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Examples of Source PredictabilityExamples of Source Predictability
TCP will keep at most a certainamount of traffic in flight
We say it is elasticrate isproportional to latency
Voice will send only and exactly asfast as the coding algorithm permits
We say it is inelastic
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Predictable Packet Treatment inPredictable Packet Treatment inRouters and SwitchesRouters and Switches
Transit latency must be within limitsacceptable to the application
Variation in transit latency must bewithin limits acceptable to theapplication
No stream may be locked out apartfrom administrative policy
Applicable policy must be observed
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Examples of UnpredictabilityExamples of Unpredictability
Queues change rapidly enough thatthe distribution cannot be described
Discards happen frequently enoughthat there is effectively no upperbound on delivery time
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Examples of PredictabilityExamples of Predictability
Classes of queues get sufficientservice that ultimate arrival is timelyand normal
Timely is an application concept
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Quality of Service Issues inQuality of Service Issues inTraffic ManagementTraffic Management
Predominantly TCP traffic
Some specific applications
Voice/video traffic
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Managing TCP TrafficManaging TCP Traffic
Moving Mountains of DataMoving Mountains of DataWithout Incurring the WorldWithout Incurring the World
Wide WaitWide Wait
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Transport Breakout TCP Applications
Backbone Traffic MixBackbone Traffic Mix
Source: MCI/NSF OC-3MON via http://www.nlanr.net, 1998
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TCP Technology IssuesTCP Technology Issues
Single drops communicate fromnetwork to sending host
You need to slow down
Multiple drops in round trip triggertime-outs
Something bad happened out here
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N+1
N
N+2N+3
Behavior of a TCP SenderBehavior of a TCP Sender
Sends as much ascredit allows
Starts credit smallAvoid overloadingnetwork queues
Increases creditexponentially
To gauge network capability
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Ack N+
1
N+1
N
N+2N+3
Ack N+
1
Ack N+
1
Behavior of a TCP ReceiverBehavior of a TCP Receiver
When in receipt of nextmessage, schedulesan ACK
When in receipt ofsomething else,acknowledges all itcan immediately
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Ack N+
1
N+1
N
N+2N+3
Ack N+
1
Ack N+
1
Ack N+
4
N+1
Sender Response to ACKSender Response to ACK
If ACK acknowledgessomething
Update credit and send If not, presume it indicates
a lost packetSend first unacknowledgedmessage right awayHalve current creditIncrease linearly to gaugenetwork throughput
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Ack N+
5
N+4
Ack N+
1
N+1
N
N+2N+3
Ack N+
1
Ack N+
1
Ack N+
4
N+1
N+4
WorldWorldWideWideWait!Wait!
Multiple Drops in TCPMultiple Drops in TCP
In the event of multiple dropswithin the same session:
Current TCPs wait for time-out
Selective acknowledge maywork around (but seeINFOCOM 98)
New Reno fast retransmitphase takes several RTTsto recover
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Remember Parekh and GallagherRemember Parekh and Gallagher
One must have at most a predictablepredictableamount of traffic in the network
One must have predictablepredictable trafficdelay in each network element
Given these, end-to-end delayend-to-end delay of ahost to host message is predictableis predictable
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How Can We Make TCP in aHow Can We Make TCP in aNetwork Act Predictably?Network Act Predictably?
Predictable amount of trafficin the network:
Well-written TCP implementationsmanage their rates to the availablebandwidth
Router needs toProvide predictable treatment of packets
Queue delay and drop characteristics
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Fundamental FIFO QueueFundamental FIFO QueueManagement TechnologiesManagement Technologies
Tail dropNetwork standard behavior
Causes session synchronization whenwaves of traffic experiencecorrelated drops
Random Early Detection (RED)Random drops used to desynchronizeTCP sessions and control rates
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Session SynchronizationSession Synchronization
Sessionsynchronizationresults fromsynchronizedlosses
Tail drop fromwaves of trafficsynchronizeslosses
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RED EnabledRED EnabledCourtesy of Sean Doran, Ebone
Effect ofEffect ofRandom Early DetectionRandom Early Detection
One day, below 100% throughputSimple FIFO with tail drop
Starting 10:00 second day, 100%throughput
Random Early Detection enabled
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RED EnabledRED EnabledCourtesy of Sean Doran, Ebone
Was that a Fluke?Was that a Fluke?
No, heres what happened that week
Session synchronization reducedthroughput until RED enabled
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0
50
100
150
200
250
300
350
400
Elapsed Time
Ns
RT
T
Mean RTT Min RTT Max RTT STD DEV
MeanMeanLatencyLatencyCorrelatesCorrelateswithwithMaximumMaximumQueueQueueDepthDepth
FIFO Traffic TimingsFIFO Traffic Timings
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0
50
100
150
200
250
300
350
400
Elapsed Time
Ms
RTT
Mean RTT Min RTT Max RTT STD DEV
MeanMeanLatencyLatencyCorrelatesCorrelateswithwithMinimumMinimumDropDropThresholdThreshold
AdditionalAdditionalCapacityCapacityto Absorbto AbsorbBurstsBursts
RED Traffic TimingsRED Traffic Timings
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ThereforeTCP QoS Definition:ThereforeTCP QoS Definition:
Normally at most one drop perround trip
Mean variation in latency boundedby predictable network
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TCP Flow StatisticsTCP Flow Statistics
>90% of sessions have ten packetseach way or less
Transaction mode (mail, small web page)
>80% of all TCP traffic results from
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An Interesting CommonAn Interesting CommonFallacy about RED:Fallacy about RED:
RED means you will have more dropsStatement derives from observed statistics
RED means that you will haveCloser to 100% utilization of your line
Less average delay per packet
But queuing theory?As a line approaches 100% utilization, drops willincrease, even though served load increaseseven though served load increases
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TCP Traffic Management IssuesTCP Traffic Management Issues
ApplicationsOften have site-specific policyassociated with them
Traffic often identifiable by port numbers
SitesGenerally identifiable by address prefixor interface traffic is received on
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TCP Bandwidth PolicyTCP Bandwidth PolicyQuestions to AnswerQuestions to Answer
Particular site or application wants atleastleast a certain bandwidth
Particular site or application wants atmostmost a certain bandwidth
Particular site or application wants toaverageaverage about a certain bandwidth
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ClassifierClassifier
Queues
InterfaceInterface
This Is Where ClassesThis Is Where ClassesCome inCome in
Classes can be for:Voice
Importantapplication/site
Unimportantapplication/site
Assuring at least a rate
Limiting to a rate
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Managed Link
Left RightICU
UC Me
U Betcha
Some Class of Traffic Wants atSome Class of Traffic Wants atLeastLeast a Certain Bandwidth a Certain Bandwidth
Example:Several organizations share cost of link
Distribute bandwidth proportional tofiscal responsibility
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Class of Traffic Wants at Class of Traffic Wants at MostMosta Certain Bandwidtha Certain Bandwidth
Traffic shaping
Similar queuing technology to class-based weighted fair queuing
Rate assigned toInterface or sub-interface
Frame Relay circuit
ATM virtual channel (in hardware)
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T-1
64KBPS
Examples of Rate ControlExamples of Rate Control
Intranet exposureLimit rate of web surfingoutside the company
Frame Relay networkAccess rate exceedsPVC ratelimit rate torate of PVC
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Some Class of Traffic Wants toSome Class of Traffic Wants toAverageAverage a Certain Bandwidth a Certain Bandwidth
Service provider or largeenterprise model
Designed forCost containment
Managed response toconflicting demands
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Marking TCP Traffic at EdgeMarking TCP Traffic at Edge
A useful technique:
Mark traffic at a network edge withsimple classifier
This allows network toDo the right thing without having to fullyclassify everywhere
Use more effective markings
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Serving TCP Traffic with theServing TCP Traffic with theAssured ServiceAssured Service
Presumes service level agreementFlat rate for traffic meeting a rate/burst profile
Usage charging for traffic out of profile
Drop management (weighted RED)All traffic subject to loss
Traffic out of profile much more subject to loss
Enhances ISP traffic engineering
(Good for service provider and consumer)
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Assured Service
0%
10%
20%
30%
40%
50%
60%
70%
0 10 20 30 40 50 60 70 80 90
TimeU
sage
Structure of Presumed ServiceStructure of Presumed ServiceLevel AgreementLevel Agreement
Up to raterate over intervalintervalis in profile
Traffic within profilegets some guarantees
Traffic out of profilehas no guaranteesPotentially dropped byWRED at bottleneckUsage pricingUsage pricing of overage
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Line Congested?Drop at Some Rate!
Best Effort Service in SimpleBest Effort Service in SimpleIP NetworksIP Networks
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Line Congestedand Packet Out ofand Packet Out ofProfileProfile? Drop at
Some Rate!
Assured Service in SimpleAssured Service in SimpleIP NetworksIP Networks
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Best effort Service in anBest effort Service in anATM-Based NetworkATM-Based Network
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Assured Service in anAssured Service in anATM-Based NetworkATM-Based Network
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So, for TCPSo, for TCP
Traffic can be contained to a rate in amanner consistent with good qualityof service
Traffic can be managed well with alittle foresight and planning
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Convergence with VoiceConvergence with VoiceNetworksNetworks
Its about Internet Telephony!Its about Internet Telephony!
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Again, the Premise:Again, the Premise:
TCP-based applications,voicevoice, and video can bemanaged well with a littleplanning
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0
20
40
60
80
100
1996 1998 2000
MultimediaDynamic WWWStatic WWWFTP and TelnetEmail and NewsOther
Changing Corporate NetworkChanging Corporate NetworkApplication PredominanceApplication Predominance
2%2%7%7%
27%27%
17%17%
39%39%
8%8%
2%2%
7%7%
27%27%
17%17%
39%39%
8%8%
13%13%
28%28%
15%15%
17%17%
12%12%
14%14%
Numbersin Percent
Source: The Yankee Group, 1996
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Email
Informationsearch/access
Subscriptionservices/Push
Conferencing/multimedia
Video/imaging
250
200
150
100
50
1997 1998 1999 2000 2001
Traffic Projectionsfor Voice and Data
Rel. BitVolume
Circuit Switched Voice
Data(IP)
From 2000 on, 80% of ServiceFrom 2000 on, 80% of ServiceProvider Profits Will Be DerivedProvider Profits Will Be Derivedfrom IP-Based Services.from IP-Based Services.Source: CIMI Corp.Source: CIMI Corp.
Growth of IP TrafficGrowth of IP Traffic
Source: Multiple IXC Projections
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IP orIP orVoiceVoice
ATMATM
OpticalOptical
B-ISDNB-ISDN IP or VoiceIP or Voiceover ATMover ATMIP overIP over
SONET/SDHSONET/SDHIP overIP overOpticalOptical
IPIP
SONET/SDHSONET/SDH
OpticalOptical
ATMATM
SONET/SDHSONET/SDH
IP orIP orVoiceVoice
OpticalOptical
VoiceVoice
IPIP
OpticalOptical
High End IP Transport AlternativesHigh End IP Transport Alternatives
Lower Cost, Complexity and OverheadLower Cost, Complexity and Overhead
Multiplexing, Protection and Management at Every LayerMultiplexing, Protection and Management at Every Layer
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H.323 Voice/VideoH.323 Voice/Video
VoiceConstant bit rate when sending
Relatively small messages (44-170 bytes)
VideoGenerally high variable bit rate
Controlled by codec efficiency on picture
Message size is generally the MTU
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Delta Frames
KeyFrame
KeyFrame
Video: Traffic PatternVideo: Traffic Pattern
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Video: Effect of DelayVideo: Effect of Delay
Delta Frames
KeyFrame
KeyFrame
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Distribution of Deliveries in Time
Tran
smis
sion
Tim
ePlaybackPoint
Unless itsToo Late
TypicalDelivery
Application Buffers Datato Ensure Consistency
Preferred DeliveryPreferred DeliveryIntervalInterval
Video: Playback PointVideo: Playback Point
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Synchronization ofSynchronization ofVoice and VideoVoice and Video
McGurk effect: voice can soundgarbled to human ear when notsynchronized with video
Therefore, we have tosynchronize these
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QoS Definition for Voice:QoS Definition for Voice:
Low loss rate
Low absolute delay in two-waysituations
Broadcast voice doesnt havethis problem
Low variation in delay
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Key Issue for Voice QoS:Key Issue for Voice QoS:
Silent periods must not be randomlyinserted or removed so as to makeother sounds unintelligible
End to end delay must becomprehended by human listener
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QoS Definition for Video:QoS Definition for Video:
Low loss rate
Low absolute delay in two-waysituations
Low variation in delay
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Key Issues for Video:Key Issues for Video:
All packets that comprise a videoframe must arrive during the sameframe interval
OK if its the last millisecond of thatinterval
Audio and video must besynchronized when shown to user
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How Can We Make Internet VoiceHow Can We Make Internet VoiceAct Predictably?Act Predictably?
Predictable amount of traffic inthe network
Predictable treatment of packets inrouters and switches
Planning to support these aspectsresults in a predictable network
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Voice/Video TrafficVoice/Video TrafficManagement IssuesManagement Issues
The fundamental problems withVoice/video traffic are
It doesnt slow down in response todelay or loss
It requires minimal variation in delay
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Predictable Amount ofPredictable Amount ofTraffic in the NetworkTraffic in the Network
The implication is that we have tocontrol used capacity
Capacity that individual calls consumeIf you experience poor quality, use amore compact encoding or a lowerframe rate
Capacity that total call volume canconsume
If there isnt capacity, refusenew calls
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Predictable Treatment of PacketsPredictable Treatment of Packetsin Routers and Switchesin Routers and Switches
We have to place voice in queuesthat give it high priority
Maintain tight delay budgets
Application of class-based WFQ
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Planning for a Predictable NetworkPlanning for a Predictable Network
Enable CBWFQ on all relevant linksConfigure voice queue with more bandwidththan traffic will need, or
For low bandwidth, priority queue [12.0(6)T]
Low speed links should useLink Fragmentation or FRF.12
RTP compression for voice
Enable RSVP call negotiationRefuse excess calls
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FRF.12, and Link FragmentationFRF.12, and Link Fragmentationand Interleavingand Interleaving
Premise:Reducing voice packet size reducessession requirements on network
So compress out IP, UDP, and RTPheaders as much as possible
Limits jitter on lower bandwidth links
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Resource ReservationResource Reservation
Current deployment
Current extensions
Extensions being developed
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Current DeploymentCurrent Deployment
RSVP version 1Call control for individual sessions
Deployed
Cisco 11.2
Microsoft Windows 98 (service pack)
Microsoft Windows NT 2000
Appropriate to edge networks
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Current ExtensionsCurrent Extensions
Policy management via COPS
LAN management via subnetbandwidth manager
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Policy Management Via COPSPolicy Management Via COPS
Local or centralpolicy server canauthorize decisions
Local policy:Simple policies
Central policyserver:
Certificates,
Complex policies
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LAN Management Via SubnetLAN Management Via SubnetBandwidth ManagerBandwidth Manager
Subnet bandwidthmanager is RSVPin a switch
Controls aggregatereservations ona LAN
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Extensions Being DevelopedExtensions Being Developed
Rapid deployment of calls
Aggregate classification inedge networks
Aggregate classification andadmission in service providernetworks
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Rapid Deployment of CallsRapid Deployment of Calls
Problem: need acknowledgedreservation installation
Solution: acknowledge it
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PSTN
PSTN
Aggregate Classification inAggregate Classification inEdge NetworksEdge Networks
Use differentiatedservices codepoints to identifytraffic
Rather thanspecific flows
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Aggregate Classification inAggregate Classification inEdge NetworksEdge Networks
Reservation requestedby host in the usualway (RFC 2205)
Flow classificationand policing at firsthop router
Flow admission alongend to end path
Aggregate classificationand policing atsubsequent routers
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Voice/video callsPlaced across aggregationdomain boundary
Aggregate Classification Aggregate Classification and Admissionand AdmissionAcross Service Provider NetworksAcross Service Provider Networks
Why?Otherwise, you dontknow that bandwidthexists on a path
Aggregate reservationsPlaced from ingressto egress for DSCP used
Use expeditedforwarding service
Limited rate of change
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Solving Voice/Video Issues UsingSolving Voice/Video Issues Usingthe Expedited Forwarding Servicethe Expedited Forwarding Service
Rate controlApplication at source
Reservation in network
Jitter controlWFQs priority queue (low speed)
Statistically empty queue (CB-WFQ)
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The Implications forThe Implications forVoice and VideoVoice and Video
We can control call volumeAnd therefore traffic volume
We can scalably prioritize traffic inthe system
And therefore deliver on latency issues
So, voice and video can be managedwell with a little planning
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Traffic Path ControlTraffic Path Control
What if IP Routing Isnt QuiteWhat if IP Routing Isnt QuiteGood Enough for Your Traffic?Good Enough for Your Traffic?
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863191056_05F9_c2 1999, Cisco Systems, Inc.
Traffic EngineeringTraffic Engineering
Historical approachesLoad sharing
Routing metrics
A new oneLabel switching
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873191056_05F9_c2 1999, Cisco Systems, Inc.
Load SharingLoad Sharing
Multipath routingEqual and unequal cost
Multilink PPP
883191056_05F9_c2 1999, Cisco Systems, Inc.
RoutingRouting
Administrative metricsDesigned to move traffic to statisticallylow volume links
Load sensitive metricsDesigned to move data away fromcongested links
Tendency towards oscillation
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893191056_05F9_c2 1999, Cisco Systems, Inc.
Utility of These:Utility of These:
While they basically work, they areNot deterministic, and
Tend to be hard to predict
903191056_05F9_c2 1999, Cisco Systems, Inc.
MMulti-ulti-PProtocol rotocol LLabel abel SSwitchingwitching
MPLS traffic engineeringVPNs and general engineering
MPLS routing for resourcereservation
In the direction of QoS routing
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913191056_05F9_c2 1999, Cisco Systems, Inc.
Principles of Label SwitchingPrinciples of Label Switching
Labeled paths:Multiple enumerated point to pointrelationships between pairs of routersSets of pair-wise relationships create alabeled tunnel
Conceptually similar to ATM VCs orFrame Relay DLCs, but
Interface independentUsed to model network layer constructsVariable length packets
923191056_05F9_c2 1999, Cisco Systems, Inc.
Notice: TwoLabels on One
Interface,Distinguishing
Routes
Network Layer ConstructsNetwork Layer Constructs
Types of traffic streamsDestination routes
Source-destination routes
AS pairs
BGP community pairs
Tunnels can createAny routing that meetsengineering needs
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933191056_05F9_c2 1999, Cisco Systems, Inc.
Using Labeled Tunnels to CreateUsing Labeled Tunnels to CreateVirtual Private NetworksVirtual Private Networks
Imagine edgenetwork with privateaddress space
Stretch labeledtunnels across thenetwork
Now, do it again Disjoint networks
Same address spaceSeparate routing
943191056_05F9_c2 1999, Cisco Systems, Inc.
MPLS Traffic EngineeringMPLS Traffic Engineering
Same technology can dragspecific routes around
Several less-used paths vs afew denser paths
Initially seen asoff-line engineering
Can use eitherLDP or RSVP to install routes
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953191056_05F9_c2 1999, Cisco Systems, Inc.
CoS in MPLS NetworksCoS in MPLS Networks
CClass oof SServiceRoughly similar to diff-serv code point
Eight values, not sixty-four
Implements similar drop/delaymanagement within labeled tunnels
Therefore, MPLS networks havefundamental TCP QoS support
963191056_05F9_c2 1999, Cisco Systems, Inc.
The Obvious HoleThe Obvious Hole
Wouldnt it be nice if engineeredlabeled tunnels could
Have specific bandwidths guaranteed?
Recover from network events quicklyand automatically using reasonable ifnot optimal routes?
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973191056_05F9_c2 1999, Cisco Systems, Inc.
MPLS Routing for ResourceMPLS Routing for ResourceReservationReservation
Use OSPF/IS-IS to distributebandwidth availability information
Edge router does SPF calculationwhen needed
RSVP used to install labeled tunnelwhile checking for race events
CoS field used to identify traffic forqueued rate support
983191056_05F9_c2 1999, Cisco Systems, Inc.
Automated Reinstallation ofAutomated Reinstallation ofLabeled TunnelsLabeled Tunnels
RSVP tears downaffected tunnels
Edge devicesrecalculate routes
RSVP used tore-install tunnels
Bandwidth checksresult in retry
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993191056_05F9_c2 1999, Cisco Systems, Inc.
Q.E.D. MPLSQ.E.D. MPLS
Traffic engineering for networklayer traffic can be managed wellwith a little planning
100 1999, Cisco Systems, Inc. 3191056_05F9_c2
So, What Are YouSo, What Are Youto Do about It?to Do about It?
Here the Rubber Meets the RoadHere the Rubber Meets the Road
100 1999, Cisco Systems, Inc. 3191056_05F9_c2
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1013191056_05F9_c2 1999, Cisco Systems, Inc.
Plan Your Network forPlan Your Network forPredictabilityPredictability
Network engineering
Assured forwarding serviceTCP
Expedited forwarding serviceVoice, implies some form of admission
1023191056_05F9_c2 1999, Cisco Systems, Inc.
Network EngineeringNetwork Engineering
Capacity engineeringEngineered IP routes?
May involve traffic engineeringLabeled tunnels?
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1033191056_05F9_c2 1999, Cisco Systems, Inc.
Assured Forwarding ServiceAssured Forwarding Service
Designed for TCPClasses control rates for SLAs
Drop controls trace effects backto sources
Implement usingCommitted access rate,
Weighted Random Early Detection,
Class-based weighted fair queuing
1043191056_05F9_c2 1999, Cisco Systems, Inc.
Expedited Forwarding ServiceExpedited Forwarding Service
Appropriate to voice/video
RequiresUnder-subscribed traffic classes
Reservation of bandwidth
Policing
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1053191056_05F9_c2 1999, Cisco Systems, Inc.
Guiding PrinciplesGuiding Principlesfor Predictabilityfor Predictability
One must have at most a predictablepredictableamount of traffic in the network
One must have predictablepredictable trafficdelay in each network element
Given these, end-to-end delayend-to-end delay of ahost to host message is predictableis predictable
1063191056_05F9_c2 1999, Cisco Systems, Inc.
In Your NetworkIn Your Network
TCP-based applications, voice,and videoand yourbandwidthcan be managedwell with a little planning
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1073191056_05F9_c2 1999, Cisco Systems, Inc.
1083191056_05F9_c2 1999, Cisco Systems, Inc.