internet qos : pieces of the puzzle
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2010. Március 22.
Internet QoS: Pieces of the puzzle
• Introduction
• Definitions and Terminology
• Internet Service Regulation
• QoS Architectural Issues
• Conclusions: Joining the Pieces Together
Topics:
2
• 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/qo
s.html
• QoS Components:
http://www.ciscopress.com/articles/articl
e.asp?p=352991&seqNum=4
Sources:
3
Introduction
• 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
What is QoS?
5
The Internet is
• unregulated
• connectionless
• designed without QoS!
• Routers and switches cannot provide QoS
cheap, fast
• Best effort: default QoS level
Problem:
6
• 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
Why QoS is not widely used? (1):
7
• 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
Why QoS is not widely used? (2):
8
Definitions and Terminology
• Packet loss
• Latency: end-to-end delay
• Jitter: delay variation
• Uptime: availability
• Throughput: data trasfer rate
QoS parameters:
10
parameter voice service average Internet maximum
Internet
Packet loss 1% 2% 27%
Latency 200 ms 65 ms 85 ms
Jitter 30 ms - -
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
QoS categories, mechanisms:
11
CoS (= Class of Service):
12
• 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)
• 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
SLA (= Service Level Agreement):
13
• Only local agreement
• Not rigorous
• Presented as terms of service
– without CoS
– Limits the responsibility of ISPs
– Little assurance of service quality
Problems with SLA:
14
• 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
Problems with SLA – example:
15
• Subsription-based QoS:
– Fixed bandwidth allocated
– Pay for the service
– Unused
• On-demand QoS:
– According to actual needs allocated
– Pay-per-use
– No guarentee
Types of QoS(1):
16
• 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
Types of QoS(2):
17
• 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
Types of QoS(3):
18
• 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
Other issues:
19
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 objective20
Reliability:
• For customers:
• Availability of end-to-end functionality
• For the network provider:
• Ability to experience failures
• No impact into the service
21
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 service23
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 24
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! 25
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 26
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
27
Internet Traffic report:
28
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 29
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 services30
Internet Service Marketing:
Management process
Identifies customers
requirements
Last step: advertising
Trade-off: „how to meet
customer requirements
and satisfy in a
profitable manner”31
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”32
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?34
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 traffic35
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
36
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 applications37
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 38
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
QoS Routing(2):
39
IP over QoS-driven lower layer technologies Transport technologies, eg:
– Ethernet
– OBS (= Optical Burst Switching)
Traffic classification
40
A viable QoS Architecture Layer 7 switching: processing of layer 2 up
to layer7 header Web switch: can interpret HTML tags and make
decisions at layer 2 or 3 Load balancing
Web caching Move content close to the end user
Popular, good results
41
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 roles43
The puzzle:
44
• Introduction
• Definitions and Terminology
• Internet Service Regulation
• QoS Architectural Issues
• Conclusions: Joining the Pieces Together
Internet QoS: Pieces of the Puzzle
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