Download Internet QoS

Internet QoS:
Pieces of the puzzle
2010. Március 22.
Topics:
• Introduction
• Definitions and Terminology
• Internet Service Regulation
• QoS Architectural Issues
• Conclusions: Joining the Pieces Together
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Sources:
• Internet QoS: Pieces of the Puzzle:
IEEE Comm. Magazine, 2010. 01. p. 86-94
• QoS: http://en.wikipedia.org/wiki/Quality_of_service
• What is QoS?
http://www.tomahawkcomputers.com/qos.html
• QoS Components:
http://www.ciscopress.com/articles/article.asp?p=35299
1&seqNum=4
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Introduction
What is QoS?
• Quality of Service
• resource reservation control mechanisms
• ability to provide different priority to different
applications
• guarantees a certain level of performance to a data
flow, eg: real-time streaming
• important if the network capacity is insufficient
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Problem:
The Internet is
• unregulated
• connectionless
• designed without QoS!
• Routers and switches cannot provide QoS
cheap, fast
• Best effort: default QoS level
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Why QoS is not widely used? (1):
• IP QoS is not Internet QoS
• needed:
– more architectures
– scalability
• IP was designed without QoS
– Big growth rate
– Driven by market demands
– Many autonomous systems
• needed:
– simple
– pragmatic
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Why QoS is not widely used? (2):
• No consensus on the exact meaning of Internet service
• needed:
– Understand the benefits of QoS
– Good business models including QoS
• Free mentality and internet neutrality
– Investment in QoS cost for the end-users
• needed:
– flexible
– rigid
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Definitions and Terminology
QoS parameters:
• Packet loss
• Latency: end-to-end delay
• Jitter: delay variation
• Uptime: availability
• Throughput: data trasfer rate
parameter
voice service
average Internet
maximum Internet
Packet loss
1%
2%
27%
Latency
200 ms
65 ms
85 ms
Jitter
30 ms
-
-
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QoS categories, mechanisms:
IntServ:
• Reserving network resources
• RSVP protocol
• Not scalable, not supported
DiffServ:
• Marked packets by type
• Queuing strategies in routers and switches
• Not widely used: „the costs of premium are too high relative to the
perceived benefits”
BE (= Best Effort):
• Not really QoS, just FIFO queuing strategy
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CoS (= Class of Service):
• Applying a set of priority levels
• Implementation:
– IntServ
– DiffServ:
PHB (= Per Hop Behavior):
a service class
• EF (= Expedicted Forwarding)
• AF (= Assured Forwarding)
• BE (= Best Effort)
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SLA (= Service Level Agreement):
• Business oriented
• Technical specifications:
– SLS (= Service Level Specification): guideline
for impelentation
– SLO (= Service Level Objetive): subset of SLS,
describes the goals
• Main drivers: voice and video applications
• Eg:
– MOS = Mean Opinion Score
– ASR = Answer Seizure Ratio, percentage of calls that
are successfully completed
– Guaranteed uptime
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Problems with SLA:
• Only local agreement
• Not rigorous
• Presented as terms of service
– without CoS
– Limits the responsibility of ISPs
– Little assurance of service quality
14
Problems with SLA – example:
• 98% of
– E-mail response time does not exceed 20 s
– Connenction to hosted server does not exceed 1,5 s
– Website download does not exceed 8 s
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Types of QoS(1):
• Subsription-based QoS:
– Fixed bandwidth allocated
– Pay for the service
– Unused
• On-demand QoS:
– According to actual needs allocated
– Pay-per-use
– No guarentee
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Types of QoS(2):
• Soft QoS:
– No service quality assured during abnormal network conditions
– Not good for applications that need predictable service quality
– Not attractive enough to pay
– Not much better as Best Effort
• Hard QoS:
– Provides predictable service quality
– Attractive enough to pay extra fee
– Difficult for ISPs to provide QoS under abnormal network
conditions
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Types of QoS(3):
• Explicit QoS:
– The customer explicitly requires a specific service level
– selling QoS as an option
• Implicit QoS:
– The customer does not specifically
asks for QoS
– Embedded into services, eg: premium service
– No special fee
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Other issues:
• TE (= Traffic Engineering):
– Performance evaluation
– Optimization of networks
• TM (= Traffic Management):
– Network operation
• TC (= Traffic Control):
– Means and actions
• Usage:
– By vendors to implement CoS
– By ISPs to offer differenciated services
– By Internet backbone providers to achieve specific
network performance
– By IT departments to prioritize traffic
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QoS planning:
To be considered together:
•
Topology
•
Capacity
•
Traffic
•
Routing methods
•
Control schemes
Aim:
•
To optimize network performance
•
To be QoS not a constraint, but an objective
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Reliability:
•
For customers:
•
•
Availability of end-to-end functionality
For the network provider:
•
Ability to experience failures
•
No impact into the service
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Internet Service Regulation
Regulation(1):
•
•
Internet service:
–
Regulate the Internet as a whole service
–
Regulate specific services
Eg: Internet telephony
–
ILECs (= Incumbent Local Exchange Carriers):
basic service
–
ISPs: embedded service
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Regulation(2):
•
•
•
Common standard:
–
Difficult
–
Sophisticated
–
Costly OAM (= Operation, Administration and Maintenance)
Regulators:
–
Rather penalties, than incentives
–
Minimum targets
Responsibility:
–
Service is sold by ISPs and delivered over the ILEC infrastructure
–
Difficult to specify responsibility
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Internet neutrality vs Two-tier Internet
•
•
•
Internet neutrality:
–
Users control the content they view
–
good for data applications
–
New definition: equal treatment among similar applications
Two-tier Internet:
–
ISPs discriminate content according to payment
–
Good for delay-sensitive applications, eg: voice, video
–
Sophisticated
Hot debate!
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Service monitoring and accounting
•
Monitoring:
–
Initiated by the operator
–
Obtains a general view of
the network performance
•
•
Accounting:
–
Requested by the customer
–
Sophisticated
Can use the same collection tools
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Internet Service Monitoring:
•
ISPs use self-reporting systems
•
Regulators can audit the ISP logs
•
RAQMON (= Real-time Applications QoS Monitoring
Framework): to improve service quality
•
Internet traffic reports:
–
Internettrafficreport.com
–
www-iepm.slac.stanford.edu
–
Uses ping
–
Measures packet loss and delay
–
USA and developed / developing countries
–
37% of the world has poor packet loss ratio
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Internet Traffic report:
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Internet Service Accounting:
•
No standard model
•
1991: accounting framework (made by OSI)
•
Motivations, pros:
•
–
Provides feedback for the user
–
Verifies performance
–
Penalizes inefficient / reward efficient usage
Cons:
–
overhead
–
Detailed information about the user protection
–
Complex OAM, high costs
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Internet Service Pricing:
•
Key role for success
•
Flat pricing:
–
Simple
–
No overhead
–
Low management costs
but:
•
–
Over consuming
–
Inefficient in congestion situations
Trade-off:
–
ISPs want predictable incomes
–
Users want flexible pricing and not
paying for unused services
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Internet Service Marketing:

Management process

Identifies customers
requirements

Last step: advertising

Trade-off: „how to meet
customer requirements and
satisfy in a profitable
manner”
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A feasible business model:

Presenting value added services with the Internet
service

Embedded services, eg: video conference, IPTV

Pricing relies on usage growth

„service providers should price QoS into their
services and not sell QoS explicitly”
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QoS Architectural Issues
Issues:

QoS supported at application,
transport, network, data link
layer

Some of them

Where, when ,how to perform
QoS routing and signaling?
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DiffServ (= Differentiated Services):
• Scalable
• Efficient for streaming, file transfer
• Inefficient for delay-sensitive applications
• Factors:
– Cost of deployment
– Impact on performance
– Complexity of provisioning
– Impact on network planning and monitoring
• Best performance: premium traffic is a minor proportion of
overall traffic
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Application level QoS:

Applications adjust service level

Requires a signaling protocol, eg: RSVP

Requires IntServ or DiffServ

Problems:

–
Scalability (IntServ)
–
No means for negotiating the service level (DffServ)
Solution: hybrid model, but not yet demonstrated
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Transport Layer QoS:

Compatible with DiffServe

No need to involve the application

Problem: a QoS level provided which is not needed or not enough

TCP:
– Flow and congestion control: slow start, windowing
– Error control: retransmission, ACK mechanism
– Not adequate for delay-sensitive applications

UDP:
– No delivery guarantees
– Requires higher level protocol, eg: RTP
– Adequate for delay-sensitive applications
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QoS Routing(1):

Assumption: BE (= Best Effort) path is used for BE
and distinguished traffic

No path discovery feature routing protocol needed

Already existing:
– QOSPF (= Quality Of Service Path First)
– Q-BGP (= QoS-Enhanced Border Gateway Protocol)

Problem: critical issues not addressed, eg: processing
delay, convergence time, instability, inaccuracy
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QoS Routing(2):

Solution:
– scalability: SLA based on the local QoS capabilities
– Single-domain QoS
– Multidomain QoS
– The whole Internet
– Q-BGP (= QoS-Enhanced Border Gateway Protocol)
– Application-layer QoS routing
– Performance-based routing: best routes selected by monitoring the
network performance
– Multiple connections to other ISPs
– AQR (= Assured Quality Routing): dynamically reroutes traffic
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IP over QoS-driven lower layer technologies

Transport technologies, eg:
– Ethernet
– OBS (= Optical Burst Switching)

Traffic classification
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A viable QoS Architecture

Layer 7 switching: processing of layer 2 up to layer7
header



Load balancing
Web caching


Web switch: can interpret HTML tags and make decisions
at layer 2 or 3
Move content close to the end user
Popular, good results
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Conclusion:
Joining the Pieces Together
Conclusion:
• Customer’s willingness to pay depend on the effectiveness of the model
• ISP: sell QoS implicitly without special fees
• Adequate trade-off between penalties and incentives
• Goal of QoS: improve overall Internet performance
• QoS should rely on usage growth
• Selling service bundles: Best Effort should be only one bundle
• Not necessarily CoS
• Only effective when a small fraction of the traffic has to be prioritized
• Planning, TE, OAM, accounting, reliability play key roles
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The puzzle:
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Internet QoS: Pieces of the Puzzle
• Introduction
• Definitions and Terminology
• Internet Service Regulation
• QoS Architectural Issues
• Conclusions: Joining the Pieces Together
Köszönöm a figyelmet!
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