Quality of service in heterogeneous networks: current status, examples, and open issues

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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VTT TECHNICAL RESEARCH CENTRE OF FINLAN D

7.7.2006 2

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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7.7.2006 3

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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7.7.2006 4

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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7.7.2006 5

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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7.7.2006 6

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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7.7.2006 7

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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7.7.2006 8

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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7.7.2006 9

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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7.7.2006 10

OVERPROVISIONING vs. QoS

Overprovisioning

"throwing money at a problem"

"inefficient"

"ineffective"

"wasteful"

it simply sounds wrong


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7.7.2006 11

OVERPROVISIONING vs. QoS (2)

But, then, which of the two figures below do youconsider more efficient, effective, or wasteful?


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7.7.2006 12


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.htm


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7.7.2006 13


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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7.7.2006 14


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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7.7.2006 15

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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7.7.2006 16

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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7.7.2006 17

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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7.7.2006 18

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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7.7.2006 19

"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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7.7.2006 20

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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7.7.2006 21

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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7.7.2006 22

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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7.7.2006 23

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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7.7.2006 24

UMTS QoS CLASSES

Conversational

Streaming

Interactive

Background

Video telephony

DB & serveraccess

Real-timevideo

Radio

VoIP

E-mail

Web browsing

Podcasts

Telephonyspeech

GamesIM

File downloads

Messaging


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7.7.2006 25

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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7.7.2006 26

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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7.7.2006 27

3G AND BEYOND TEST NETWORK

Sensornetwork

WLAN

3G

Internet

Session mobility

Terminal mobility


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7.7.2006 28

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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7.7.2006 29

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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7.7.2006 30

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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7.7.2006 31

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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7.7.2006 32

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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7.7.2006 33

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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7.7.2006 34

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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7.7.2006 35

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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7.7.2006 36





only reliable way



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7.7.2006 37





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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7.7.2006 38

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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7.7.2006 39

QoSMET End-to-end QoS Monitoring Tool

Packet

capture

Packet

capture



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7.7.2006 40

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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7.7.2006 41

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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7.7.2006 42

VERTICAL HANDOVER PERFORMANCE measurement scenario



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7.7.2006 43

VERTICAL HANDOVER PERFORMANCE measurement scenario

Mobile IP in use

50s 50s50s50s50s

PUBLIC 3GNETWORK

WLANWLAN

LAN LAN



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7.7.2006 44

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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7.7.2006 45

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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7.7.2006 46

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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7.7.2006 47

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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7.7.2006 48


Real-time video coding adaptation method for gameservice

Network monitoring tool

Real-time video encoding parameter optimization



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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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7.7.2006 50


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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7.7.2006 51

3G/UMTS DYNAMIC CAPACITY ALLOCATION



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7.7.2006 52

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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7.7.2006 53

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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7.7.2006 54

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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7.7.2006 55

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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7.7.2006 56

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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7.7.2006 57

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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7.7.2006 58

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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7.7.2006 59

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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7.7.2006 61

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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7.7.2006 64

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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7.7.2006 65

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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7.7.2006 66

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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7.7.2006 69

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


WLAN 802.11WLAN H/2

GPRS/UMTS


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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7.7.2006 98

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/

Quality of service in heterogeneous networks: current status, examples, and open issues

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Transcript of Quality of service in heterogeneous networks: current status, examples, and open issues