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Internet2 QoS: Is Less More?

Ben Teitelbaum <ben@internet2.edu> January 16th, 2002

NYSERTech Conference New York University

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Why QoS?

Best effort internet vulnerable to Best effort internet vulnerable to Best effort internet vulnerable to Best effort internet vulnerable to Best effort internet vulnerable to Best effort internet vulnerable to Best effort internet vulnerable to Best effort internet vulnerable to

Best effort internet vulnerable to

"tragedy of the commons" and DDOS "tragedy of the commons" and DDOS "tragedy of the commons" and DDOS "tragedy of the commons" and DDOS "tragedy of the commons" and DDOS "tragedy of the commons" and DDOS "tragedy of the commons" and DDOS "tragedy of the commons" and DDOS

"tragedy of the commons" and DDOS

Internet2 doing everything it can to Internet2 doing everything it can to Internet2 doing everything it can to Internet2 doing everything it can to Internet2 doing everything it can to Internet2 doing everything it can to Internet2 doing everything it can to Internet2 doing everything it can to

Internet2 doing everything it can to

promote new, radically more promote new, radically more promote new, radically more promote new, radically more promote new, radically more promote new, radically more promote new, radically more promote new, radically more

promote new, radically more

demanding apps demanding apps demanding apps demanding apps demanding apps demanding apps demanding apps demanding apps demanding apps

QoS needed as safety belt to avert a QoS needed as safety belt to avert a QoS needed as safety belt to avert a QoS needed as safety belt to avert a QoS needed as safety belt to avert a QoS needed as safety belt to avert a QoS needed as safety belt to avert a QoS needed as safety belt to avert a

QoS needed as safety belt to avert a

success catastrophe success catastrophe success catastrophe success catastrophe success catastrophe success catastrophe success catastrophe success catastrophe success catastrophe

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Why bother?

Despite more than 20 years of effort, Despite more than 20 years of effort, Despite more than 20 years of effort, Despite more than 20 years of effort, Despite more than 20 years of effort, Despite more than 20 years of effort, Despite more than 20 years of effort, Despite more than 20 years of effort,

Despite more than 20 years of effort,

internet QoS continues to be a mirage internet QoS continues to be a mirageinternet QoS continues to be a mirage internet QoS continues to be a mirageinternet QoS continues to be a mirage internet QoS continues to be a mirage internet QoS continues to be a mirageinternet QoS continues to be a mirage

internet QoS continues to be a mirage

Internet is arguably so successful Internet is arguably so successful Internet is arguably so successful Internet is arguably so successful Internet is arguably so successful Internet is arguably so successful Internet is arguably so successful Internet is arguably so successful

Internet is arguably so successful

because becausebecause becausebecause because becausebecause

because of the utter simplicity of the of the utter simplicity of the of the utter simplicity of the of the utter simplicity of the of the utter simplicity of the of the utter simplicity of the of the utter simplicity of the of the utter simplicity of the of the utter simplicity of the BE model BE modelBE model BE modelBE model BE model BE modelBE model BE model

Wonders can be achieved through Wonders can be achieved through Wonders can be achieved through Wonders can be achieved through Wonders can be achieved through Wonders can be achieved through Wonders can be achieved through Wonders can be achieved through

Wonders can be achieved through

clever application adaptation clever application adaptationclever application adaptation clever application adaptationclever application adaptation clever application adaptation clever application adaptationclever application adaptation

clever application adaptation

QoS is expensive, bandwidth cheap QoS is expensive, bandwidth cheapQoS is expensive, bandwidth cheap QoS is expensive, bandwidth cheapQoS is expensive, bandwidth cheap QoS is expensive, bandwidth cheap QoS is expensive, bandwidth cheapQoS is expensive, bandwidth cheap

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Apology for Continued Work in QoS

Will cost/benefit ratio for QoS always be >1?

• What if economics of bandwidth changes?

• What about very lightweight forms of QoS?

• Safety belt justification still valid

Mirage is just too appealing

• "The efficacy with which one uses the available bandwidth in the transmission fabric directly drives the fundamental

’manufacturing efficiency’ of the business and its cost structure" − M. O’Dell

• "The Holy Grail of computer networking is to design a

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Outline for the Rest of This Talk

Short history of Internet2 QoS

Why Premium has failed and may never come to be

Non−elevated services

Taking another (closer) look at application QoS needs

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QBone Architecture

(circa 1999)

A Service: QBone Premium Service

• IP circuit−emulation (a.k.a. "virtual leased line")

• Built on Expedited Forwarding (EF) (RFC 2598)

Reservation Setup Protocol

• Initially: long−lived, manual setup

• Later: SIBBS protocol between QBone domains; RSVP end−to−end between hosts

QBone Measurement Architecture

• Uniform collection of QoS metrics

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QBone Architecture (30 kilofoot view)

• Architecture focuses on interdomain interfaces... –Edge−to−edge services –Signaling –Measurement GigaPoP A Campus A Campus C Campus D Backbone Campus B GigaPoP B

• ...and how edge−to−edge services concatenate to form an e2e service

• Each domain needs to think in

terms of provisioning edge−to−edge “virtual trunks” (policed on ingress / shaped on egress)

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Obstacles to Premium Deployment

Low demand

Current router support for DiffServ is spotty Fundamental practical deployment difficulties Fundamental theoretical problems

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Obstacles to Premium Deployment

Low demand

• Classical "chicken−and−egg" problem

• Artificially constrained BE load (more...)

Current router support for DiffServ is spotty Fundamental practical deployment difficulties Fundamental theoretical problems

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Utilization Paradox

Order ~104 hosts with nothing slower than switched 100Mbps Ethernet between them

Theoretically, ~25 of these could congest the 2.4 Gbps backbone

Yet... the backbone is lightly loaded!

Paradox: Abilene is both under−provisioned

and under−utilized Why is this?!

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“Typical” E2E Internet2 Performance

1

1. Draft paper at: http://www.internet2.edu/abilene/tcp/ • 50,000 bulk TCPs observed on 6/19/01 • Sampled NetFlow at core router • Observed throughputs: • Median: 880 Kbps • 10% ≥ 3.9 Mbps • 1% ≥ 23 Mbps

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Performance Faults Obviate QoS

Evidence suggests that most problems are in hosts and LANs

Common performance faults

• Broken TCP stacks (e.g. inadequate socket buffering, no window scaling)

• Ethernet duplex mismatch

• Crummy cabling (e.g. CAT3, shared, or damaged)

Internet2 End−to−End Performance Initiative

• Major initiative to work on this problem •

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Obstacles to Premium Deployment

Low demand

Current router support for DiffServ is spotty

• No PQ

• DiffServ comes with a performance cost

• Limitations on token bucket depths

• Inflexible classification rules (hooks to routing missing)

Fundamental practical deployment difficulties Fundamental theoretical problems

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Obstacles to Premium Deployment

Low demand

Current router support for DiffServ is spotty

Fundamental practical deployment difficulties

• Requires all−or−nothing network upgrades (e.g. all access interfaces must police)

• Service verification (by users or providers) difficult • Dramatic changes to network operations, peering

arrangements, and business models

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Obstacles to Premium Deployment

Low demand

Current router support for DiffServ is spotty Fundamental practical deployment difficulties

Fundamental theoretical problems

• Original IETF EF RFC broken (draft−ietf−diffserv−

rfc2598bis−02.txt fixes RFC2598, but not yet adopted by IETF working group)

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Coupling of Shapers and Policers

GigaPoP B Backbone

?

What is exact coupling at cloud boundaries?

• Firehose policing results in absurdly low efficiency • Microflow policing results in no aggregation

• A "virtual trunk" model seems right, but...

Careful analysis seems to unravel aggregation

• Policers must be matched by upstream shapers

• If offered load within aggregate exceeds

downstream sub−aggregate

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“Non−Elevated Services

"Worse"

• QBone Scavenger Service (QBSS)

• Bulk Handling PDB (B. Carpenter, K. Nichols)

"Different−but−equal"

• Alternative Best Effort (ABE)

• Best−effort Differentiated Services (BEDS)

Why do we like these wacky services?!

• Require no policing, admissions, settlement, etc. • Deploy incrementally at the granularity of single

interfaces •

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QBone Scavenger Service

Basic idea

• Voluntary marking hints to network that degraded service is OK (like Un*x nice for the network)

• Scavenger traffic may be degraded at congestion points • Think: thin, bottom−feeding best−effort network that can

expand to full capacity in absence of congestion • Formal service definition:

http://qbone.internet2.edu/qbss/qbss−definition.txt

Goals

• A tool to preserve/extend uncongested BE experience for interactive applications

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Motivations

1/2

All traffic is not equal w.r.t. loss and delay

• Mix of tolerant/intolerant traffic

• Since you may be competing with yourself for

downstream resources, it’s in your interest to identify tolerant traffic

Most routers support multiple queues

• Let’s get some value and experience out of them!

Internet2 utilization very low

• Pro: interactive apps work fine; Con: what a waste! • What new applications could be built if we weren’t shy

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Motivations

2/2

Fine−grained Netiquette

• Self−policing users exist

–HEP community runs bulk−transfers “at night”

–Network backups

–CDN pre−fetching

• QBSS allows these apps to run continuously

Pricing

• Additional control over upstream commodity usage • Potential point of negotiation for metered connectors

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Current State of QBSS

Testing underway to support bulk transfer needs of HEP and astrophysics users

• SLAC, TransPAC (GRAPE), CERN, UKERNA

Gear tested and configs available for:

• Cisco 7200, 7500, GSR • Juniper

Some operational traction >1% QBSS on Abilene

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QBSS Usage at Abilene CLEV

Biggest QBSS emitting ASes:

• RIT

• MORENET

• UMD

• MSUNET

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Alternative Best Effort (ABS)

Monolithic best−effort service class split into:

• Blue −lower loss / higher delay • Green −higher loss / lower delay

Fairness relationship between classes

Each app knows its utility function and trades off loss for delay accordingly

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Application QoS Needs

Too much mythology and confusion about what apps really need

Goals:

• Build bridges between networkers and developers

• Promote best practices for developing and deploying adaptive multimedia applications

Activities in this area

• Detailed survey of application QoS needs and

relationship between application utility and network performance

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For more information...

Internet2 QoS WG Home:

• http://www.internet2.edu/qos/wg/

• Links to all WG design teams may be found here

QBone Scavenger Service • http://qbone.internet2.edu/qbss/

Application QoS Needs

• http://www.internet2.edu/qos/wg/apps/

QBone Home:

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References

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