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8/14/2019 Quality of service in heterogeneous networks: current status, examples, and open issues
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QUALITY OF SERVICE IN HETEROGENEOUS NETWORKS:CURRENT STATUS, EXAMPLES, AND OPEN ISSUES
Kostas Pentikousis and Milla Immonen
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QOS DEFINED: RESEARCH
QoS is a mature, well-researched topic
Packet Classification
Shaping and Policing
Buffer acceptance and queue management
Scheduling algorithms
However, QoS seems to fade as a research topic
The research community is more interested in
Network measurements and analysis
TCP and TCP-friendly protocol performance
over multi-gigabit pipes, multi-hop wireless P2P, Routing, Overlays
Security, Gaming
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QOS DEFINED: DEPLOYMENT
Several deployment attempts did not succeed inmaking QoS ubiquitous
Integrated Services (early 90s)
Differentiated Services (mid 90s), QBone
ATM, MPLS, wireless ATM vs. IEEE 802.11, In addition, overprovisioning seems to be more wide-
spread, more attractive than deploying QoS
Is that a bad thing?
Is overprovisioning the solution?
Is it enough? Why not?
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QOS ACCORDING TO NETWORK OPERATORS
The ability of the network to deliver traffic within acertain range of values of
Throughput (b/s)
Delay (s) and Jitter (s)
Packet Loss (%) due to congestion andcorruption
Out-of-order delivery
Typically, network operators agree to meet suchpredetermined ranges X% of the time
5 "9s" = 99.999% = fail to meet QoS 5 min/year
3 "9s" = 99.9% = ~9 hours/year
2 "9s" = 99% = ~3.65 days/year
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REASONS TO DEPLOY QOS
Huston (2000) notes three main reasons forintroducing QoS in the Internet architecture
1. High-quality support for IP voice and video
2. Service response management
3. A differentiated Internet access service,providing a network client with a range ofservice-quality levels at a range of prices
All three seem to be centered around networkoperator interests
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QOS: CAVEATS
QoS does not create any(new) capacity, but
is the means to deal with lack of resources
if capacity is scarce, resource sharingrequires frugality
"proper" resource allocation QoS introduces a certain degree of complexity in the
network
Ordinary end users expect something else than "9s"
Ulseth (2004) A network QoS class definition is notsufficient for the user
Networks not belonging to the operator domainsuch as WLAN are not included,
Media processing (voice coding) and otherterminal related characteristics are not included
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OVERPROVISIONING: IT AIN'T BAD
Overprovisioning is not a new idea
Factor of safety (a.k.a. factor of ignorance)
Eighteenth century iron bridges had a factor of safety
of 3-7x the calculated load
The Harilaos Trikoupisbridge connecting Rio-Antirio in SW Greece
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OVERPROVISIONING (2)
Redundancy
RAID: increase fault tolerance/reliability and/orperformance
Availability
A. S. Tanenbaum asks: when was the last time you
picked up the phone and got a busy tone?
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OVERPROVISIONING (3)
Ease of use
Memory garbage collection
Peak performance
Do you really need a dual core 64-bit CPU at 3 GHz?
Infinitesimal extra cost
Ride the Ethernet upgrade wave: 10102103 Mb/s
Deploy 802.11a/b/g although either of the 3 would bemore than enough
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OVERPROVISIONING vs. QoS
Overprovisioning
"throwing money at a problem"
"inefficient"
"ineffective"
"wasteful"
it simply sounds wrong
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OVERPROVISIONING vs. QoS (2)
But, then, which of the two figures below do youconsider more efficient, effective, or wasteful?
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OVERPROVISIONING vs. QoS (3)
Do you consider this overprovisioned?
Interstate 105/Interstate 110 Interchange, Los Angeles, California,USA
Source: http://www.fhwa.dot.gov/eihd/i105i110.htm
http://www.fhwa.dot.gov/eihd/i105i110.htmhttp://www.fhwa.dot.gov/eihd/i105i110.htm8/14/2019 Quality of service in heterogeneous networks: current status, examples, and open issues
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OVERPROVISIONING vs. QoS (4)
Well, the I-105/I-110 interchange (completed in 1993)received an Award of Meritin 1996 by the US DOT -Federal Highway Administration, for Excellence inHighway Design
This is an intermodal interchange: "It has three levelsof transfer facilities, including direct HOV connectorsbetween the two freeways"
HOV? That's a form of QoS, isn't it?
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OVERPROVISIONING vs. QoS (5)
So, perhaps, excess capacity may not be a "badthing" and can coincide with QoS
More seriously, considering total cost of ownership(TCO), can it be that overprovisioning alone is the
right thing and no QoS is needed? Networkers need to determine whether QoS is
deployable?
reliable?
cost-effective?
the only viable solution?
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QoS vs. CHARGING
QoS has been typically associated with tiered, e.g.bronze, silver, gold and platinum services, andpolicing/charging schemes
Charging, the argument goes, is an effective meansfor enforcing QoS
Flat pricing: allpackets are marked as platinum
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QoS vs. CHARGING (2)
QoS is by no means identical to tiered charging; itdoes not have to be amalgamated with tiered billing,and may have nothing to do with charging per packet
Instead, QoS can provide the framework to deliver aservice in the first place
Case in point? Maxinetti, a triple play service (IPTV +VoIP + Broadband Internet access) offered in themetropolitan Helsinki area in Finland
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QoS AS A BUSINESS ENABLER: maxinetti
End users pay X euros for a given IPTV channelpackage, Y euros for VoIP, Z euros for Internetaccess, or buy the bundle at a discount
The operator, Maxisat, must differentiate flows fromdifferent services
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PRAGMATIC QoS
Differentiating between classes of traffic is easier,more scalable
More like traffic prioritization
Given 8 Mb/s of downlink capacity, must provide
sufficient & sustained bandwidth (IPTV: 3-5 Mb/s) low end-to-end delay for VoIP
low jitter for VoIP and IPTV
operational reliability and low packet loss rate
Maxisat could have employed DiffServ, IntServ, or
any other more elegant or sophisticated QoS scheme.They didn't.
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"QoS THAT WORKS"
Gigabit Song ring &residential cabling
infrastructure
Use IEEE 802.1P CoSand IP TOS fields to
deliver bundled digitalIPTV, VoIP andbroadband Internetaccess
DSLAM handlesdownstream classification
Cope with standardequipment (keepcosts low, increase
reliability)
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Maxinetti
It works :) and shows that CoS may be enough and itshould be the first step to a tier-service system.
Maxisat opted for rudimentary downlink flowclassification using CoS at Layer 2 and ToS at Layer
3 to provide end-to-end QoS
Why? Reliability and cost effectiveness
Yet this is a closed, homogeneous networkinfrastructure, under single administrative control
What about end-to-end cross AD QoS? First, let's seewhat kinds of QoS frameworks exist
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ATM
ATM allows point to point and point to multipoint virtual circuit to berequested with pre-specified QOS.
Rich set of QoS mechanisms with a wide variety of service categoriesor QoS descriptors.
Class A (AAL1) - Constant Bit Rate (CBR) service bit rate is constant
Class B (AAL2) - Variable Bit Rate (VBR) servicet
the bit rate is variable but requires a bounded delay fordelivery.
Class C (AAL3/4 or AAL5) - Connection-oriented data service connection is set up before data is transferred, variable bit rate does not require bounded delay for delivery
Class D (AAL3/4 or AAL5) - Connectionless data service datagram traffic and in general
data network applications where no connection is set upbefore data is transferred
AAL= ATM Adaptation Layer
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QoS IN CELLULAR NETWORKS
AvailableUp to 384 kbits/sWCDMA20003
AvailableTheoretically up to
10,8 Mbits/sCurrent situation 1Mbits/s
HSDPA (extension
to WCDMA)
same3.5
NO9.6 kbits/sCDMA & TDMAvoice
900/1800/19002
Available
(not used)
Up to 76 kbits/sGPRS, EDGE, andHSCSD (in additionto digital voice)
same2.5
NO1.2 kbits/sAnalogue voice450/9001
QoSData rate (kb/s)TechnologyFrequency
(MHz)
G
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QoS MECHANISMS IN UMTS
Versatile needs of applications lead to trafficprioritising
Traffic can be divided into 4 QoS classes
1. Conversational class
2. Streaming class3. Interactive class
4. Background class
Biggest difference between these classes is thedelay sensitivity
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UMTS QoS CLASSES
Conversational
Streaming
Interactive
Background
Video telephony
DB & serveraccess
Real-timevideo
Radio
VoIP
Web browsing
Podcasts
Telephonyspeech
GamesIM
File downloads
Messaging
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3G - Universal Mobile TelecommunicationsService (UMTS) Architecture
UTRAN = UMTS Terrestrial Radio Access Network
Node B = Base station
RNC = Radio Network Controller
GGSN= Gateway GPRS Node
SGSN= Serving GPRS Support Node
Core
Network
RNC
RNC
NODE B
NODE B
NODE B
NODE B
Iub
Iub
Iub
Iub
Iur
RNS
RNS
UTRAN
Iu
Iu
SGSN
GGSN
IP
Firewall
Ethernet
Applicationservers
WWW,E-mail
WapGateway
Internet /Intranet /ISP
Applications Content
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3G TEST PLATFORM
Provides access for realWCDMA terminals toCore network andInternet
Enables easily the end-
to-end service testing in3G environment
Makes optimisation andenhancements of QoS-mechanism in UTRANand Core network
possible without intrudingupon public network
Iub = UMTS interface between radio network controller and base stationGi = Interface between gateway GPRS support node and external network
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3G AND BEYOND TEST NETWORK
Sensornetwork
WLAN
3G
Internet
Session mobility
Terminal mobility
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WiMAX Enhancements for VTT's Laboratory Network
Research and implementation work Video and Voice over IP services
Fast rate control supporting cross-layer information Mobility and multi-access enhancements VHOs between different access networks
Subscriber station (SS) and base station (BS) sidesolutions to gather and process channel andnetwork state information
Testbed environment
Open development and testingenvironment
Connectet to VTT laboratory network andto Internet through FUNET and GEANT
VHO = vertical handoverMIP = mobile IPHIP = host identity protocol
DiffServ = differentiated services
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IEEE 802.11 WLAN: FAMILY OF STANDARDS
IEEE Subgroups has standardised
physical layer of OSI
802.11b: 11 Mbits/s in 2.4 GHz band
802.11a: 54 Mbits/s in 5 GHz band
802.11g: 54 Mbits/s in 2.4 GHz band MAC sub layer
Provide transparent interface for the higher layerusers
existing network protocols run over IEEE 802.11WLAN
WLAN can be thought as a wireless version of theEthernet, which provides best-effort service
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WLAN 802.11 NEW STANDARDS
IEEE 802.11e, 802.11f and 802.11i understandardisation process
IEEE 802.11e will provide enhanced QoSmechanisms
IEEE 802.11f Inter-Access Point Protocol (IAPP) IEEE 802.11i will provide security mechanisms
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IEEE 802.11 MAC SUBLAYER
Distributed coordination function(DCF)
listen before talk
works based on a Carrier SenseMultiple Access (CSMA)
DIFS = DCF Interframe Space
SENSE THECHANNEL
BACKOFF
SENSE THECHANNEL
SENSE THECHANNEL FOR
ADDITIONALRANDOM TIME
SEND AFTERDIFS SECONDS
FREE
FREE
BUSY
BUSYFREE
BUSY
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WLAN IEEE 802.11e
QoS Standard
Work is Final
Goal:
enhance the access mechanisms of IEEE802.11
provide service differentiation
Enhanced DCF (EDCF)
extension of DCF
allows traffic to be classified into 8 different traffic
classes, by modifying the backoff times
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MONITORING QoS
Close to network traffic measurements
Main difference: result analysis
in QoS analysis network traffic is used as a tool toreveal the performance characteristics
delay maximum throughput
jitter, etc.
passive measurement methods
monitoring existing traffic
active methods traffic is generated for the measurements
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Mobility Management Mechanisms
During the last years Mobile IP (MIP) has
become "de facto" mobility management protocolfor Internet
Although MIP is workable, it has several defects
handovers may not be fast and smooth
message overhead can be significat ifHome Agent is distant
QoS implementations are problematic dueto tunneling
It does not support micromobility
rely on IP addresses hard to identify host
which are beyond NATs etc.
Several new protocols and enhancements have
been proposed Hierarchial MIPv6, Cellular IP, HAWAII for
micromobility
Host identity protocol (HIP) for security,multihoming, end-host mobility
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SUBJECTIVE QoS vs. OBJECTIVE QoS
User experience is the one that counts!
Subjective QoS is the service quality from the userperspective
measuring subjective QoS is done by user tests
only reliable way Mean Opinion Score (MOS) tests are often used
expensive and time consuming
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SUBJECTIVE QoS vs. OBJECTIVE QoS
User experience is the one that counts!
Subjective QoS is the service quality from the userperspective
measuring subjective QoS is done by user tests
only reliable way
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SUBJECTIVE QoS vs. OBJECTIVE QoS
User experience is the one that counts!
Subjective QoS is the service quality from the userperspective
measuring subjective QoS is done by user tests
only reliable way Mean Opinion Score (MOS) tests are often used
expensive and time consuming
Objective QoS
can be measured directly
can be used to estimate subjective QoS
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MONITORING TOOLS
Available to all
Off-the-shelf network analyzers (Ethereal,Tcpdump, WinDump, )
Custom software based on standard packet
capture libraries (libpcap, WinPcap) Operator and enterprise level monitoring tools
OSS
RTCP, RMON2, RTFM,
MRTG
Typically measure round trip, notend-to-end one-wayparameters
Network asymmetries dictate a closer look at one-wayend-to-end measurements
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QoSMET End-to-end QoS Monitoring Tool
Packet
capture
Packet
capture
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VERIFYING QoSMeT
VoIP call between the laptops
Network emulator for adjusting packet loss value
Measurements with QoSMeT
packet loss
offered load and throughput
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VERIFYING QoSMeT EXAMPLE packet loss
0.033 0.0070.03[390, 450]
0.0000.00[360, 390)
0.152 0.0130.15[300, 360)
0.0000.00[270, 300)
0.050 0.0080.05[210, 270)
0.0000.00[180, 210)
0.201 0.0210.20[120, 180)
0.0000.00[90, 120)
0.100 0.0100.10[30, 90)
0.0000.00[0, 30)
Measured avg. Ploss
+
95 % CI
Emulated packet loss
(PlossE
)Time (s)
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VERTICAL HANDOVER PERFORMANCE measurement scenario
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VERTICAL HANDOVER PERFORMANCE measurement scenario
Mobile IP in use
50s 50s50s50s50s
PUBLIC 3GNETWORK
WLANWLAN
LAN LAN
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VERTICAL HANDOVER PERFORMANCE - delay
0
0.02
0.04
0.06
0.08
0.1
0.12
0.14
0.16
0.18
0.2
0.0 50.0 100.0 150.0 200.0 250.0
Time [s]
Delay[s]
Delay
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VERTICAL HANDOVER PERFORMANCE duration of connection loss
0.010
0.100
1.000
10.000
0.0 50.0 100.0 150.0 200.0 250.0
Time [s]
Connectionlosslength[s
]
Loss length
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TIME FOR QoS THROUGHOUT THE STACK
Intra- and, to some extent, inter-system handoversbased on link layer metrics are commonplace inwireless networks
We need to go further: session continuity
VTT demonstrated session continuity forstreaming media between different devices (PCand IPAQ running Linux)
AMBIENT NETWORKS DEMO
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QoS THROUGHOUT THE STACK (2)
Applications will need to incorporate some form ofadaptation too (related work: MAGELLAN, PHOENIX)
Example: QoS-Aware Gaming-on-Demand
Oper
ators
Intern
etbackb
one
conn
ectio
n
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QoS THROUGHOUT THE STACK (3)
Real-time video coding adaptation method for gameservice
Network monitoring tool
Real-time video encoding parameter optimization
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QoS THROUGHOUT THE STACK (4)
Moore's Law is favorable to more efficient, butcomputationally expensive codecs
Pattern of development cycles efficiency gains
at least two cycles to come after MPEG-4 Part 10D. Wood, EBU
Source: European Broadcasting Union
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QoS THROUGHOUT THE STACK (5)
Conjecture: QoS in heterogeneous environmentscannot be delivered with network-based QoS alone
We can provide a certain level of QoS or adaptation atthe two ends of the protocol stack
What about the rest of the stack?
Underlying mechanisms need further study
Transport protocols, such as TCP, might needsome new options. Example: TCP User TimeoutOption(draft-ietf-tcpm-tcp-uto-02, October 2005)
Handovers cannot be solely based on link layermetrics (e.g. SNR). Why?
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3G/UMTS DYNAMIC CAPACITY ALLOCATION
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3G/UMTS: FIRST CONNECTION GOODPUT
4 8 16 32 64 128 256 512 1024
0
50
100
150
200
250
300
350
MOSET Payload (KB)
Goodput(kb/s)
XX X
X
X
X
X
X
X
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LAN: FIRST CONNECTION GOODPUT
4 8 16 32 64 128 256 512 1024
0
20
00
4000
6000
8000
10000
MOSET Payload (KB)
Goodput(kb/s)
X X
X
X X
X
X
X
X
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THE "PROPER" IP QoS
When unconditioned TCP-like traffic (i.e., traffic thatslows down in the face of congestion) is mixed in withreal time traffic (that keeps going despite congestion),both sides lose
Carpenter & Nichols (2002)
Need a QoS framework matching IP principles:
Network services (QoS) should notbe designedfor, or tied to any particular application
IP designers did not attempt to predict what
applications will be using the networkneither should QoS designers
Provide the means to differentiate traffic andallow for network engineering
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DIFFERENTIATED SERVICES ARCHITECTURE
Scalable:
classification & conditioning onlyat boundaries
small set of forwarding behaviors
apply per-hop behaviors to aggregates of traffic
Incrementally deployable Differentiation is asymmetric, decoupled from apps
A refinement of the original Precedencemodel
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IPv4 CLASS-BASED DIFFERENTION
RFC 791 (1981) and RFC 1812 (1995)
RFC 2474 (1998) and RFC 3260 (2002)
RFC 3168 (2001)
Precedence Type of Service
Differentiated Services Field
Differentiated Services Field ECN
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SERVICE SPECIFICATION & PHBs
Service level specification (SLS): set of parametersand their values which together define the serviceoffered to a traffic stream by a DS domain
Traffic conditioning specification (TCS): set ofparameters and their values which together specify a
set of classifier rules and a traffic profile
TCS: integral element of an SLS
Per-hop Behaviors (PHB):
Default; best effort
Class selector
Expedited forwarding (EF); "virtual leased line" Assured forwarding (AF)
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CLASSIFICATION
Bonaventure defines a flow as a sequence of packetswith one common "characteristic", which can bebased on any field of the packets
Flows can be defined at different layers providing finergranularity and control at the cost of more
state/lookups
Classify once at edge, mark and then use markings
Static vs. Dynamic Classification
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STATIC CLASSIFICATION
Layer 2: ATM and Frame Relay circuits, switched e2ecircuits (GbE, soon XGbE and beyond); L2 VPNs
Layer 3: IP host-to-host, but also all IP traffic with thesame next BGP hop; L3 VPNs
Layer 4: All TCP traffic from host-to-host is treateddifferently from all UDP traffic for the same pair.
Layer 7: HTTP vs. VOIP vs. FTP vs. SMTP
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TRAFFIC CLASSIFICATION & CONDITIONING
Classifier
Meter
Marker Shaper/DropperPackets
Measure the temporal propertiesof the packet stream
Set DSCP
Delay/discard some or all of the
packets in a traffic stream in orderto bring the stream intocompliance with a traffic profile
Multi-fieldclassification
Differentiated Services Field ECN
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DiffServ ARCHITECTURE
Minimalist sophisticated simplicity
Separation of control and forwarding (like in IP)
Supported by all major vendors in mid- and high-endrouters
Inter-domain, bilateral agreements For inter-AD traffic, perhaps the only pragmatic,
standardized framework in actual deployment
Nevertheless, deployment is not widespread
Non-technical obstacles
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SLOW DEPLOYMENT
The Maxinetti case shows that class-baseddifferentiation is deployable, allows for new services,and can be profitable
That is exactly what DiffServ was all about
So why is public deployment of DiffServ soooo slow?
Need inter-provider agreements (cf. VPN)
Need to demonstrate the benefits(?) of QoS
Need to enforce consistent policies
Overprovisioned backbones
QoS is costly and can lead to operational
overhead for providers
No common, well-understood service definitions
Your reason here :)
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OPEN ISSUE: WHO NEEDS QoS?
L3 virtual private networks (VPN)?
Most of the DiffServ deployments
Network games? Henderson & Bhatti (2003):
Many and successful net games using best
effort only Throughput not an issue, delay is
Reported delays deter users from joining a server
Delay increases while playing do not force usersto leave in droves despite the noticeabledegradation in their gaming performance
Would gamers pay for QoS?
Yes, if included in the price of the game
No, if it was offered as a "premium" service
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OPEN ISSUE: WHO NEEDS QoS? (2)
VoIP
Skype is already making VoIP reality without anyQoS and you only need a dialup connection
Why would a user pay more for her VoIPpackets? She wouldn't. But she would go for aMaxinetti kind of service which is cheap and hip :)
And that is our view: QoS frameworks should beseen as enablers, not as cash cows
IPTV
Video gaming servers
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MULTIMEDIA APPLICATIONS AND QOS
Application QoS metrics (Bhargava, 2002)
Timeliness (meetplay-out deadlines)
Accuracy (play the rightdata)
Precision (receive what was sent)
For instance, in a multimedia presentation play all frames in order, without delays and
discards
on time and in sync with the rest of the content
do so at the bit rate of the encoded stream,without any discounts on quality.
The network can provide guaranties in drop rate, butan SVC receiver may discard half the received frames
Can meet throughput requirements (averaged over acertain period) but break timeliness for real-time video
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MULTIMEDIA ADAPTATION LAYER:MOTIVATION
FP6 IST PHOENIX (2004-2006)
Tag line:jointly optimizing multimediatransmissions in IP-based wireless networks
develops solutions that exploit availablebandwidth on wireless links efficiently
source coding
MAC, channel coding
targets multimedia transmission over wireless IPnetworks
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MULTIMEDIA ADAPTATION LAYER:MOTIVATION (2)
Layered video has a hierarchical structure:
not a "flat" byte stream
neither a series of independent datagrams
but a stratified, interdependent "set of streams"
associated with a different end-user "value" andplay out deadlines
Are typical transports and rudimentary traffictreatment sufficient?
Need
a solution for different access networks
to evaluate the real benefits from H.264/SVCwhile it's being standardized
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A SCALABLE EXTENSION TO H.264/AVC
SVC is a scalable extension to H.264/AVC
jointly developed by MPEG (ISO) and VCEG(ITU) expert groups
aims at offering scalability with comparablecoding efficiency versus current state-of-the-artnon-scalable coding schemes (H.264)
standardization process is still ongoing
scalability is three-dimensional
Temporal (frames/s)
Spatial (image resolution)
SNR (signal-to-noise ratio)
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H.264/SVC MAIN GOAL
Video is encoded only once
The encoded version can be scaled easily to severaluser equipment (from HDTV to mobile phone)
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H.264/SVC CODING EFFICIENCY
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RELATED WORK
Lots of work on MPEG-4 FGS (with and without cross-layer optimizations)
FGS coding efficiency is not so good
Lots of work on MAC-based (802.11e, for example)cross-layer design and optimizations
we are interested in a solution that can workbased on established standards, independent ofMAC if possible
No prior network simulation studies with SVC
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MULTIMEDIA ADAPTATION LAYER:ARCHITECTURE
Source rateadaptation
Traffic differentiation
Packet prioritization
Rate adaptation
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MULTIMEDIA ADAPTATION LAYER:ARCHITECTURE (2)
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SIMULATION METHODOLOGY
Video ServerVideo receiver
D1 Trace
Network
Direction of video packet stream
2. ns-2 simulationns-2trace
1. Virtual video streams
3. Trace post-processing
H.264/SVCEncoder/
PacketizerVideo
Packet arrivaltime, size, layer,
? Video qualitymetrics
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RESULTS (1/3): THROUGPUT
0
100000
200000
300000
400000
500000
600000
10 11 12 13 14 15 16 17 18 19 20
Time (s)
Throughput(b
ytes/s)
TCP H.264/SVC SVC/PriQ SVC/MAL
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RESULTS (2/3): PACKET ARRIVALS
1.8
2.3
2.8
3.3
3.8
4.3
4.8
5.3
10 11 12 13 14 15 16 17 18 19 20
Packet Arrival Time (s)
SVCL
ayer
Packets Received:
H.264/SVC/MAL
Packets Dropped
H.264/SVC/PriQ
H.264/SVC
4/5
3
21
0
0
1
2
3
4/5
4/5
3
2
1
0
4/5
3
2
1
0
0
1
2
3
4/5
0
12
3
4/5
Video-on-demand over TCP New Reno (no layers, no priorities)
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RESULTS (3/3) : PACKET ARRIVALS
1.8
2.3
2.8
3.3
3.8
4.3
4.8
5.3
16 16.1 16.2 16.3 16.4 16.5 16.6 16.7 16.8 16.9 17
Packet Arrival Time (s)
SVCL
ayer
Packets Received:
H.264/SVC/MAL
Packets Dropped
H.264/SVC/PriQ
H.264/SVC
4/5
3
21
0
0
1
2
3
4/5
4/5
3
2
1
0
4/5
3
2
1
0
0
1
2
3
4/5
0
12
3
4/5
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MAL: SUMMARY
The Multimedia Adaptation Layer (MAL)
builds on recent advances in scalable, layeredvideo standards
employs standards-based network and MAC-layer traffic prioritization mechanisms
is necessary for scalable video over wirelessnetworks
Our evaluation methodology
capitalizes on
cutting-edge, prototypical H.264/SVC video
encoding software the most widely-used network simulator
provides important insights for futuredevelopment
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VOIP WITHOUT QOS: SKYPE
Skype bundles
VoIP (the first p2p-based client)
Free PC-PC, with the best quality comparedto Yahoo!, AIM, Google Talk
Very cheap (0.02 EUR/min) to/from most ofthe world supporting both PC-PSTN(SkypeOut) and PSTN-PC (SkypeIn)
Teleconferencing (up to 5 people)
Recently, video calling too
Instant messaging (IM)
File transfer (p2p-based, of course)
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WHY SKYPE THRIVES
Skype works
Seamlessly behind NATs and firewalls
Implements TURN and STUN (or somevariant) at the client
In contrast SIP-based VoIP requires explicitserver configuration in applications
Availability (WinOS, Linux, MacOS, PocketPC)
Easy installation, same interface and functionality
Does not require lots of resources (not evenbandwidth)
Gives a certain feeling of privacy to users byencrypting all of its traffic -- other IMs do not
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SKYPE: NETWORK ARCHITECTURE
Skype is KaZaa-based
Supernode-based hierarchical p2p network
Can detect NATs and firewalls
Skype Uses
TCP for signaling UDP (preferably) and TCP for VoIP traffic (if
firewall/NAT-restricted)
No fixed-ports
Encryption on all but a few initialization packets
256-bit AES for calls and IMs
1024-bit RSA to negotiate symmetric AESkeys
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SKYPE: NETWORK ARCHITECTURE (2)
Supernodes are elected based on
Network availability (open Internet access)
Bandwidth availability
CPU, memory, play a smaller (if any) role
Users cannot prevent their node from becoming asupernode (unlike other p2p)
May be able to influence the process, though
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SKYPE: NETWORK CHARACTERIZATION
Supernodes
Consume less than 205 b/s (!) 50% of the time
Negligible CPU, memory consumption
Relay data only 9.6% of the time
Data sessions are less frequent than VoIPones
File sizes tend to be considerably smallerthan in other p2p networks (photos, docs,slide sets-- not mp3's and videos)
Relay NAT-restricted calls:
Median/mean call duration--2m50s/12m53s (PSTN calls average 3m)
Max call duration--3h26m
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QoS WITH FLAT PRICING???
QoS is about allowing the user to select betweenquantitative performance guarantees
Crowcroft et al. (2003)
Personal opinion
QoS as a service enabler which brings newproducts in the market
Unchain QoS from "cost linked to quality"
Marketing should be about a service not thetechnology
Those familiar with "all-you-can-eat" buffets most
certainly appreciate the simplicity in pricing Yet, when one starts talking to me about QoS I check
that my wallet is in place
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QoS WITH FLAT PRICING!!!
Free nights and weekendshas been quite a commonoffering from US cellular operators for years now
Vonage, Cablevision offer unlimited US & Canadacalls
Do these schemes hurt revenues? Decrease profits?
How much can one "eat" anyway?
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OPEN ISSUE: OPERATIONAL COMPLEXITY
Based on his operational experience Bell (2003)argues that
Network Operation Center personnel have cometo believe that complex protocols destabilize anetwork, mainly due to buggy implementations
Case in point: introducing multicast in the LBNLnetwork led to difficult to trace bugs
Amplification and Coupling principles
IP multicast as a limit-case: Any QoS frameworkshould be less complex than multicast in order to gainwide adoption
As such, IntServ is pretty much done
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OPEN ISSUE: OPERATIONAL COMPLEXITY (2)
Overprovisioning to the rescue: simple andeconomical
The "10% rule"
Deal with network congestion
Throw bandwidth at the problem
or
Throw protocols at the problem
There are cases, though, that bandwidth simply
cannot be thrown at the problem (regulatory andCAPEX issues, spectrum licenses,)
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OPEN ISSUE: TRAFFIC CLASSIFICATION
Traffic classification
End hosts are the natural points, but due to lackof trust and maintaining administrative control,gateways are preferred by NOCs
Dynamic classification of packets into different
classes is not a trivial task
Inhibits QoS deployment
M. Roughan, et al. (2004):
Framework for scalable, dynamic trafficclassification based on statistical application
signature Obtain signatures insensitive to the particular
application protocol
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END to END QoS
Total QoS is composed of several mechanisms ondifferent protocol layers (MAC scheduling,retransmissions, packet sizes, routing decisions,priorization, flow control, congestion control, )
mapping of QoS parameters between protocol
layers and optimisation within single technologyneed to be done but is not enough
User experience depends on the performance ofthe whole chain of technologies between him andthe service -> interoperable QoS mechanismsare needed
Number of users and QoS needs of their applicationsneed to be fitted together with the restricted resourcesavailable
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END-TO-END QoS IN HETEROGENEOUSNETWORKS
Network heterogeneity =>Quality ofService has to be deployed end-to-end
QoS schemes in IP Networks
Best Effort
Integrated Services (IntServ)
Differentiated Services (DiffServ) WLAN QoS
IEEE 802.11e being finalized
Service Level Agreements (SLA)
adjusting QoS classes of differentnetworks
No End-to-End method standardised yet Application used by the User Equipment
should be able to specify its QoS needs
WLAN
2G
LAN3G
PAN
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EUREKA/ITEA EASY WIRELESS PROJECT
IP NETWORK
AdHoc Mobile Net Community
PAN Network
Wide Services & Interactions
WLAN 802.11WLAN H/2
GPRS/UMTS
Local Services & Interactions
Office WLANNetwork
Factory WLAN
Network
IP NETWORK
AdHoc Mobile Net Community
PAN Network
Wide Services & Interactions
WLAN 802.11WLAN H/2
GPRS/UMTS
Local Services & Interactions
WLAN 802.11WLAN H/2
GPRS/UMTS
Local Services & Interactions
Office WLANNetwork
Factory WLAN
Network
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Easy WirelessAllow seamless roaming between wireless
networks while maintaining Quality of Service
EUREKA/ITEA project
ITEA is a project clusteringorganisation
funding from each country
16 partners from 5 countries
Sept. 2004-Sept. 2007
Total budget: 12 Million
Partners
Thales Communications
Telefnica
4 Universities
5 SMEs
4 Research Centres
Belgium
Finland
Netherlands
Norway
Spain
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SYNOPSIS
QoS is a well-researched issue
Mature frameworks developed for LANs, WANs,and inter-AD
No e2e QoS framework
Mappings are not standardized
Deployment is still slow
QoS used as an enabler for new services, not as acash cow.
QoS-awareness needs to be diffused throughout thestack
Overprovisioning not a bad thing, not antithetic to QoS
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ACKNOWLEDGMENTS
Sari Jrvinen, Jukka Mkel, Jyrki Huusko (VTT)
Stephen Sykes (Maxisat)
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FURTHER READING
G. Armitage, Quality of service in IP networks: Foundations for amulti-service Internet, Indianapolis, IN: Macmillan TechnicalPublishing, 2000.
G. Bell, "Failure to thrive: QoS and the culture of operationalnetworking", Proc. ACM SIGCOMM 2003 Workshops, Karlsruhe,Germany, August 2003, pp. 115-119.
B. K. Bhargava, "Guest Editorial: Quality of Service in MultimediaNetworks", Multimedia Tools and Applications, 17(2-3), 151-156.
S. Blake, D. Black, M. Carlson, et al., An Architecture forDifferentiated Service, Internet RFC 2475, December 1998.
B. Carpenter, & K. Nichols, "Differentiated Services in the Internet",IEEE Proceedings, vol. 90, no. 9, 2002, pp. 1479-1494.
K.G. Coffman & A.M. Odlyzko. "Internet growth: Is there a "Moore'sLaw" for data traffic?," In: J. Abello, et al. (eds.), Handbook of
Massive Data Sets, Boston, MA: Kluwer, 2001. J. Crowcroft, S. Hand, R. Mortieret, et al., "QoS's downfall: at the
bottom, or not at all!", Proc. ACM SIGCOMM 2003 Workshops,Karlsruhe, Germany, August 2003, pp. 109-114.
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FURTHER READING (2)
S. A. Baset and H. Schulzrinne, "An Analysis of the Skype Peer-to-Peer Internet Telephony Protocol" Proc. INFOCOM 2006, Barcelona,Spain, April 2006.
B. Davie, A. Charny, J.C.R. Bennett, et al., An Expedited ForwardingPHB (Per-Hop Behavior), Internet RFC 3246, March 2002.
B. Davie, "Deployment Experience with Differentiated Services," Proc.ACM SIGCOMM 2003 Workshops, Karlsruhe, Germany, August2003, pp. 131-136.
D. Grossman, New Terminology and Clarifications for Diffserv,Internet RFC 3260, April 2002.
S. Guha, N. Daswani, and R. Jain. "An Experimental Study of theSkype Peer-to-Peer VoIP System," Proc. 5th International Workshopon Peer-to-Peer Systems (IPTPS '06), Santa Barbara, CA, February2006.
J. Heinanen, F. Baker, W. Weiss, J. Wroclawski, Assured ForwardingPHB Group, Internet RFC 2597, June 1999.
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FURTHER READING (3)
W. Hardy, QoS measurement and evaluation of telecommunicationsquality of service, West Sussex, England: John Wiley & Sons, 2001
T. Henderson & S. Bhatti, "Networked games: a QoS-sensitiveapplication for QoS-insensitive users?", Proc. ACM SIGCOMM 2003Workshops, Karlsruhe, Germany, August 2003, pp. 141-147.
G. Huston, "Quality of Service--Fact or Fiction?", The InternetProtocol Journal, 3(1), 27-34.
R. Lloyd-Evans, QoS in Integrated 3G Networks, Norwood, MA:Artech House, 2002.
K. Nichols, et al., Definition of the Differentiated Services Field (DSField) in the IPv4 and IPv6 Headers, Internet RFC 2474, December1998.
K. Pentikousis, et al., Active goodput measurements from a public3G/UMTS network, IEEE Communications Letters, 9(9), 802-804.
H. Petroski, To engineer is humanthe role of failure in successfuldesign, New York: Vintage Books,1992.
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RELATED WEB SITES
Easy Wireless
http://ew.thales.no
Ambient Networks
www.ambient-networks.org
MAGELLANMultimedia Application Gateway forEnterprise Level LANs
www.magellan-itea.org
PHOENIXJointly optimizing multimediatransmissions in IP based wireless networks
i t h i
http://ew.thales.no/http://www.ambient-networks.org/http://www.magellan-itea.org/http://www.ist-phoenix.org/http://www.ist-phoenix.org/http://www.magellan-itea.org/http://www.ambient-networks.org/http://ew.thales.no/