Halina Tarasiuk, Robert Janowski and Wojciech Burakowski

Warsaw University of Technology, Poland

Admissible Admissible TTraffic raffic LLoad of oad of RReal eal TTime ime CClass of lass of SService for ervice for

IInter-domain nter-domain PPeerseers

Contents

• Classes of service concept as an approach for providing strict QoS guarantees at the network level– Experiences from AQUILA project (5FR)

– EuQoS project (6FR – in progress)

• RT service at an inter-domain peer

• CAC for RT service– Algorithm

– Numerical results

• Summary

Classes of service concept as an approach for providing strict QoS guarantees at the network level– Experiences from AQUILA project (5FR)– EuQoS project (6FR – in progress)

QoS at different levels

user user

codec codec

Additional mechanisms

Additional mechanisms (e.g. playback buffer)

Network interface

Network interface

Application level

Application level

ITU G.1010

ITU Y.1541

Subjective assessment

Network level

Network level

User level User level

To guarantee packet losses, packet delays

Subjective assesment

Classes of Service

Class of service concept

• A „service class” represents a set of traffic that requires specific delay, loss and jitter characteristics from the network for which a consistent and defined per hop-behaviour applies

• A service class pertains to applications with similar characteristics and performance requirements

Discussed Classes of services (IETF proposal)

Tolerance To Tolerance To Inter-Provider

Service Class (Aggregate)

Loss Delay Jitter PHB

End-To-End Service Class Loss Delay Jitter

DSCP Name

DSCP Value

Ctrl Low Low Yes CS Network Control

Low Low Yes CS7 111000

Telephony VLow Vlow VLow EF 101110 Signalling Low Low Yes CS5 101000

MM Conferencing

L-M Vlow Low AF4x 100xx0*

RT Interactive

Low Vlow Low CS4 100000 Real Time VLow VLow VLow EF

Broadcast Video

VLow Med Low CS3 011000

MM Streaming

L-M Med Yes AF3x 011xx0*

Low Latency Data

Low L-M Yes AF2x 010xx0*

OAM Low Med Yes CS2 010000

None Real Time

Low LIM Yes AF

High ThruPut Data

Low M-H Yes AF1x 001xx0*

Best Effort NS NS NS DF Standard NS NS NS DF 000000

• End-to-end – related to applications (visible by users)

• Aggregated in some network parts (maintained by the network)

Definition of a service class

1. QoS objectives: values of packet losses, delays...

2. Types of connections: p2p

3 Traffic descriptors: single-, double token bucket, more advanced

A. Provisioning of resources: static, dynamic

B. CAC: based on declarations, based on measurements

C. Tuning mechanisms at the packet level (PHB: classifiers, scheduling, marking, active quieueing..)

Experiences in implementing CoSs -

AQUILA network (2000-2003)

(IST-1999-10077)

Adaptive Resource Control for QoSAdaptive Resource Control for QoSUsing an IP-based Layered ArchitectureUsing an IP-based Layered Architecture

AQUILA

Admission ControlAdmission

Control AgentAdmission

Control AgentEnd-userApplication

Toolkit

Resource Control Layer

Core Router

Core Router

Core Router

Access Network

Access Network

Edge Router

Edge Router

Set

tin

g

Resource Control

Resource Control Agent

Set

tin

g

Consideration of Network LoadMonitoring

ProbingResults

AQUILA Architecture

resources resources

QoS Request

QoS Request

QoS Request

QoS in core networks – IP prototype solutions: AQUILA

Network service Traffic type

Characteristic examples

Application example

Premium CBR Constant

Small packets low loss, low dela

SIP VoIP

Premium VBR Variable Large packets low loss, low delay

SIP Video

Premium MM Adaptive required throughput

File transfer (FTP)

Premium MC Very short bursts

very low delay & loss

online games

Standard Best effort classical the rest

Goal: only a few few network services to allow clear service differentiation

Tested CAC algorithm for PCBR service - RT service

New flow is admitted if:

(1)

Where N1 denotes the number of connections in progress and parameter (<1) specifies the admissible load of capacity allocated to the PCBR. The value of can be calculated from the analysis of M/D/1/B system taking into account the target packet loss ratio and the buffer size [2].

(2)

 

Where Buffer denotes buffer size in packets and Ploss target packet

loss ratio.

1

1

1

CPBRPBRN

iinew

)ln(2

2

lossPBuffer

Buffer

Overall Topology for Trial in AQUILA

Implementing CoSs in EuQoS system (2004-2006)

End-to-end Quality of Service support over heterogeneous

networks

Some of the problems to be solved

• Scalable architecture

• Signalling system

• Providing QoS at the packet level

• To cope with network heterogeneity

• Etc.

USER 1 USER 2

EQ-SDP

EQ-SIPSignaling

EQ-SIPSignaling

Network technology Independent sub-layer

Network technology dependent sub-layer

EQ-SDP in

End-to-end QoS EQ-SIP signaling

AccessNetwork

1

QoSDomain

i

AccessNetwork

2

QoSDomain

k

QoSDomain

j

RA1 RAkRAjRAiRAn

RM1 RMi RMj RMk RM2n

Virtual Network Layer

Application Application

EuQoS Architecture: Physical View

EQ-pathEQ-path

EQ-SDP

EQ-ETP

Protocols

EQ-ETP

Protocols

EQ-NSIS EQ-NSISEQ-NSIS EQ-NSIS

EQ-SIPproxy

EQ-SIPproxy

EuQoS system

End-to-end CoS path

QoS domain path QoS domain path QoS domain path QoS inter-domain path

QoS inter-domain path

QoS signalling – EQ-SSN

QoS routing – EQ-BGP (path)

RM

QoS Request

QoS Request QoS Request

QoS Request QoS Request

RA

QoS Request RM

RM

CoS CoS CoS CoS CoS

Borders for Classes of service

Intra- and inter-domain Classes of service

Inter-domain service AS1-AS2

AS1

output port

Egress BR

AS2

Intra-domain service in AS2

input ports Router input port

Ingress BR

Ingress BR

Ingress BR

Intra-domain service in AS1

output port

AC AC

AC

AC

AC: admission control

Classes of Service in EuQoS

QoS Objectives End-to-end Class of

Service IPLR Mean IPTD

IPDV Type of

connections Traffic descriptors

DSCP code

Telephony 10-3 100 ms 50 ms

P2P Peak bit rate, single token bucket

101110

RT Interactive 10-3 100 ms 50 ms

P2P Peak bit rate, single token bucket

100000

MM Streaming 10-3 1 s U P2P Peak bit rate, single token

bucket4

011xx0*

High Throughput Data

10-3 1 s U P2P Peak bit rate, single token

bucket4

001xx0*

Standard U U U 000000

4 We assume that for NRT traffic we will use single token bucket descriptor with given both bit rate and bit rate tolerance, depending on the application and network technology.

EuQoS Applications (Phase 1) Medigraf End-To-End

Classes of Service

VoIP VTC VoD VTC

Collaboration

data transfer

Chat

Telephony X RT

Interactive X X

MM Streaming

X

High ThruPut

Data

X

Standard X

Plan for developping CoSs in EuQoS

Access 1 (LAN)

Access 2 (UMTS)

Core

Telephony

RT Interact.

MM Stream.

High Thr. D.

Standard

RT

NRT

BE

Over-provisioned

RT

NRT

BE

User request for basic end-to-end

CoS

Aggregated CoSs

implemented on inter-

domain link

Aggregated CoSs

implemented on inter-

domain link

Aggregated CoSs

implemented in core domain

Aggregated CoSs implemented inside domain

mapping mapping mapping mapping mapping

RT

NRT

BE

RT

NRT

BE

Aggregated CoSs implemented inside domain

Access networks: LAN/Ethernet, xDSL, WiFi, UMTS

IP core: Geant

EuQoS Test Network

Applications vs. Classes of Service End-to-end

CoSs

Telephony

High throughput data

MM

streaming

RT interactive

EUQOS Applications

VoIP

Data Transfer

VoD

VTC

EUQOS Applications

VoIP

Data Transfer

VoD

VTC

End-to-end CoSs

Telephony

High throughput data

MM

streaming

RT interactive

Real Time Real Time RT

CoS on Access Network

CoS on Acess Network

CoS in Inter-domain Link

RT

NRT1

NRT3

NRT2

NRT1

NRT3

RT

NRT1

NRT3

NRT2

EQ-PATH

Network Control

CTRL CTRL CTRL Network Control

• RT service at an inter-domain peer• CAC for RT service

– Algorithm

– Numerical results

RT Class of Service

• End-to-end Classes of Service– Telephony for VoIP – short packets (60 bytes)

– RT Ineractive for VTC – long packets (1500 bytes)

• QoS metrics– IPLR – 10^-3

– Mean IPTD – 100 ms

– IPDV – 50 ms

• Traffic description: single token bucket (PBR, PBRT)

• Policing strategy– Policing in access network only (entry point); to police (PBR, PBRT)

– We have to define in each access network policy point (node)

Approach 1: not distinguishing between e2e CoSs

• CAC algorithm

• It does not take into account an impact of packet sizes on IPLR

RTRT

N

iinew CPBRPBR

1

1

)ln(22

IPLRBuffBuff

RT

RTRT

Approach 2:

Studied system for RT service for inter-domain pear

Assumptions:

- the input traffic of both end-to-end CoSs is Poisson process.

- the packet sizes are constant equal to ‘d1’ and ‘d2’, respectively for telephony and video conference CoSs and their ratio (d2/d1) is an integer denoted by ‘d’.

- the packets of these CoSs enter the same finite buffer (with buffer size – Buffer counted in packets).

Analysis (1)

Time

Packet Arrivals

Packet Departures

Q(n-1) Q(n)

Q(n+2) Q(n+3)

Q(n+1) Q(n+4) Embedded instants of inspections of system state

empty was_system_ 21

_servedpkt_type2_ 1

21

11)(

_servedpkt_type1_ 211)(

)1(

ifAA

ifd

jA

d

iAnQ

ifAAnQ

nQ

Where:

-Q(n) denotes the system state at the end of n-th embedded time instant

- A1, A2 random variable describing the number of type 1 (respectively type 2) packet arrivals during one slot,

-Ratio of packet sizes is denoted as ‘d’ (d2/d1 = d)

Figure 8. Time evolution of the system state

Analysis (2)

the load () and the arrival intensities (1,

2) are related by: 

1=1d1=1 (since d1=1);

2=2d2=2d; =1+2

1=w1 ; 2= w2

After some algebra

Eq.9

)1)(()1)((

)1)(()1)(()1)((

2221

21

21211

21

1

1211

21

22221

21

11211 )1())(1()(

zddzdd

zddzddzdd

e- ez

zee ezQ

Analysis (3)

x

zCxQob )

1(}{Pr

00

Assuming that the tail probabilities of the queue size distribution function are well approximated by the dominant pole of Q(z), they

can be written as

Further, assuming that the asymptotic constant Co equals 1, the buffer overflow probability can be expressed as

1

002 00 )

1(

1

1)

1(

}1{Pr

Buffer

Buffern

n

zzzC

BufferQobPloss

Eq.12

Analysis (4)

we can determine the value of the required decay rate parameter 1/z0. This decaying rate ensures that the buffer overflow probability will be below target Ploss value.

0

)1)((

1

)1)((

1

10

021

2

2

02

1

2

zwdw

dw

dw

zd

ww

dw

ew

ew

wz

Steps to calculate the admissible load when all the input parameters (Buffer, Ploss, d1, d2, percentage contribution of different types of traffic - w1, w2) are given:

1. Given Ploss and Buffer, determine the parameter z0 (Eq.12)

2. Create the equation (14) taking into account the number of traffic types, their characteristics (intensity, packet sizes) and the assumed input model (Poisson).

3. Solve the equation (14) with respect to which is the total admissible load.

4. Calculate the admissible load of each traffic class based on the information about percentage contribution of different traffic classes - w1, w2 (9), i.e. 1=w1, 2=w2

Eq.14

Numerical results (1)

Figure 9. Total admissible load vs. packet size ratio of two end-to-end CoSs; target Ploss=10-3

Figure 10. Packet loss ratio vs. packet size ratio of two end-to-end CoSs; target Ploss=10-3

0.00001

0.0001

0.001

0.01

0.1

1

1 3 5 7 9 11 13 15d

Plo

ss

Target Ploss

I-10% / II-90%

I-50% / II-50%

I-90% / II-10%

0

0,3

0,6

0,9

1 3 5 7 9 11 13 15d

tota

l ad

mis

sib

le l

oad

I-10%/ II-90%

I-50%/ II-50%

I-90%/ II-10%

7

Numerical results (2)

0.00001

0.0001

0.001

0.01

0.1

1

1 3 5 7 9 11 13 15d

Plo

ss

Target Ploss

I-10% / II-90%

I-50% / II-50%

I-90% / II-10%

Figure 11. Packet loss ratio vs. packet size ratio of two end-to-end CoSs; target Ploss=10-2

Figure 12. Packet loss ratio vs. packet size ratio of two end-to-end CoSs; target Ploss=10-4

0.00001

0.0001

0.001

0.01

0.1

1

1 3 5 7 9 11 13 15d

Plo

ss

Target Ploss

I-10% / II-90%

I-50% / II-50%

I-90% / II-10%

Summary

• QoS guarantees at the network layer we can assure by providing classes of service

• RT service for inter-domain peers requires adequate CAC algorithm

• The proposed algorithm works correctly and takes into account differences in packet sizes

• The algorithm will be implemented in EuQoS system and tested

• „Admissible traffic load of real time class of service for inter-domain peers” in Proc. of ICAS/ICNS 2005, 23-28 October 2005, Papeete, Tahiti, French Polynesia, published by IEEE Computer Society, 2005.

• The full text paper can be found at the homepage of TNT Group http://tnt.tele.pw.edu.pl/include/members/Artikuly/Admissible.pdf