Building Differentiated Building Differentiated Services Using the AssuredServices Using the AssuredForwarding PHB GroupForwarding PHB Group

Juha HeinänenTelia Finland Inc.jh@telia.fi

© Juha Heinanen 2

AF PHB Group (RFC 2597)AF PHB Group (RFC 2597)

Provides forwarding of IP packets in four independent service classes at each hop, each class has its own,

configurable forwarding resources within each class, an IP packet is assigned

one of three levels of drop precedencelower drop precedence means higher

probability of forwarding

© Juha Heinanen 3

AF PHB Group ImplementationAF PHB Group Implementation

forwarding resources (buffer space and bandwidth) can be allocated using FBA, CBQ, WFQ, priorities, etc.

dropping of packets is based on the Random Early Drop (RED) algorithmeach level of drop precedence (green,

yellow, red) has its own RED threshold

© Juha Heinanen 4

Example of Output BehaviorExample of Output Behavior

RR

RR

RR

RR

RR

RR

Each AF class hasits own queue and

forwarding resources

Each AF class hasits own queue and

forwarding resources

RED thresholdfor “Red” packets

RED thresholdfor “Red” packets

RED thresholdfor “Yellow” packets

RED thresholdfor “Yellow” packets

© Juha Heinanen 5

RED with Multiple ThresholdsRED with Multiple ThresholdsDiscard

Probability

AverageQueue Length0

1

“Red”Threshold

0 “Yellow”Threshold

“Green”Threshold

“Red”Packets

“Red”Packets

“Green”Packets

“Green”Packets

“Yellow”Packets

“Yellow”Packets

Full

© Juha Heinanen 6

AF Based ServicesAF Based Services

service characteristics of an AF class depend ontraffic conditioning actions at the edgerelative traffic load and scheduling policy of

the class in the core different combinations result in relative

or quantitative bandwidth and/or delay assurances

© Juha Heinanen 7

Metering, Marking and PolicingMetering, Marking and Policing

Host

EnterpriseNetwork

EnterpriseNetwork ISPISP

May police hostbehavior and

classify packets onbehalf of host

May police hostbehavior and

classify packets onbehalf of host

Polices aggregatebehavior and remarks

or drops excess

Polices aggregatebehavior and remarks

or drops excess

May meter aggregatebehavior, classify,(re)mark, drop, and

shape packets

May meter aggregatebehavior, classify,(re)mark, drop, and

shape packets

May meter hostbehavior and

shape packets

May meter hostbehavior and

shape packets

R

R R

May classifypackets to

service classes

May classifypackets to

service classesMay select outgoing packets

and drop excess

May select outgoing packetsand drop excess

© Juha Heinanen 8

Examples of Markers Examples of Markers

Two Rate Three Color Marker (trTCM)marks packets green, yellow, or red based on

Peak and Committed Information Ratesuseful when peak rate needs to be enforced

Single Rate Three Color Marker (srTCM)marks packets green, yellow, or red based on a

rate and two burst sizesuseful when only burst size matters

© Juha Heinanen 9

New tokenPIR times/sec

New tokenCIR times/sec

?

Not enoughyellow tokens

Enough yellow tokens,but not enough green tokens

Enough yellow andgreen tokens

PBS

CBS

A Two Rate MarkerA Two Rate Marker

© Juha Heinanen 10

New tokenCIR times/sec

Overflow tokensfrom C

Tc

Te

?

Not enough green noryellow tokens

Enough yellow tokens, butnot enough green tokens

Enough greentokens

CBS

EBS

A Single Rate MarkerA Single Rate Marker

© Juha Heinanen 11

Selection of Outgoing TrafficSelection of Outgoing Traffic

...

Link

ServiceClasses

Outgoing“streams”

Guaranteed MinimumAllowed Maximum

Weight

Guaranteed MinimumAllowed Maximum

Weight

Guaranteed MinimumAllowed Maximum

Weight

Guaranteed MinimumAllowed Maximum

Weight

© Juha Heinanen 12

Assured Bandwidth (AB) ServiceAssured Bandwidth (AB) Service

traffic is policed at the ingress using one of the two three color markers

green packets are delivered with high probability, yellows as best effort, and reds are discarded

resources are allocated so that the AF class is only moderately loaded with greens

© Juha Heinanen 13

Assured Delay (AD) ServiceAssured Delay (AD) Service

traffic is policed so that only green packets are allowed into the network

green packets are delivered with high probability and low delay variation

resources are allocated so that the AF class is very lightly loaded with greens

© Juha Heinanen 14

VoIP/Web ExampleVoIP/Web Example

IP PBX PSTN

VoIP GW

ISPISP

512 Kb AD

PRI ISDN128 Kb AD

WebServer

10 Mb AB

EnterpriseNetwork

EnterpriseNetwork

20 Mb AB128 Kb AD

No Profiles

© Juha Heinanen 15

Service ImplementationService Implementation

RRRR

Assured Delay WFQ Weight: 80 %

Assured Delay WFQ Weight: 80 %

Assured BandwidthWFQ Weight: 20 %

Assured BandwidthWFQ Weight: 20 %

R

Policer keeps links only lightly loaded with green

packets

Policer keeps links only lightly loaded with green

packets

Best Effort service can implemented as an

AB Service with CIR = 0

Best Effort service can implemented as an

AB Service with CIR = 0

© Juha Heinanen 16

Mapping AF PHBs to ATMMapping AF PHBs to ATM

each service class is allocated a set of forwarding resources on every link

signaling of UBR VCs is extended by a service class indicator

hierarchical scheduling first per service class and then per VC within the class

AF drop precedence is mapped to the CLP bit

© Juha Heinanen 17

ATM BackboneATM Backbone

Example of Diff-Serv MappingExample of Diff-Serv Mapping

RR

UBR VC for Assured Delay ServiceUBR VC for Assured Bandwidth Service

DropPrec

ATMCLP

00

11

RR

RR

© Juha Heinanen 18

SummarySummary

AF PHB group provides a flexible means to implement services for both delay sensitive and delay insensitive applications

AF support is already available at least in a limited form in popular routers

AF based services will become available from ISPs during 1999