Halina Tarasiuk, Robert Janowski and Wojciech Burakowski

1
Admissible Traffic Load of Real Time Class of
Service for Inter-domain Peers

• Halina Tarasiuk, Robert Janowski and Wojciech
  Burakowski
• Warsaw University of Technology, Poland

2
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

3

• 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)

4
QoS at different levels
Subjective assesment
Classes of Service
To guarantee packet losses, packet delays
5
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

6
Discussed Classes of services (IETF proposal)

• End-to-end related to applications (visible
  by users)
• Aggregated in some network parts (maintained
  by the network)

7
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..)
8
Experiences in implementing CoSs -AQUILA network
(2000-2003)
9
AQUILA Architecture
Resource Control Layer
10
QoS in core networks IP prototype solutions
AQUILA
11
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 ? (?lt1) 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.
12
Overall Topology for Trial in AQUILA
13
Implementing CoSs in EuQoS system (2004-2006)
End-to-end Quality of Service support over
heterogeneous networks
14
Some of the problems to be solved

• Scalable architecture
• Signalling system
• Providing QoS at the packet level
• To cope with network heterogeneity
• Etc.

15
EuQoS Architecture Physical View
USER 1
USER 2
EQ-SDP in End-to-end QoS EQ-SIP signaling
EQ-SIP proxy
EQ-SIP proxy
Application
Application
EQ-SIP Signaling
EQ-SIP Signaling
Virtual Network Layer
EQ-SDP
Network technology Independent sub-layer
EQ-SDP
EQ-NSIS
EQ-NSIS
EQ-NSIS
EQ-NSIS
RM1
RMi
RM2 n
RMj
RMk
EQ- ETP Protocols
EQ- ETP Protocols
Network technology dependent sub-layer
RAn
RA1
RAk
RAi
RAj
QoS Domain i
QoS Domain k
Access Network 2
QoS Domain j
Access Network 1
EQ-path
16
EuQoS system
17
Borders for Classes of service
AC
AC
AC
AC
Intra- and inter-domain Classes of service
AC admission control
18
Classes of Service in EuQoS
19
Plan for developping CoSs in EuQoS
Access networks LAN/Ethernet, xDSL, WiFi,
UMTS IP core Geant
20
EuQoS Test Network
21
Applications vs. Classes of Service
22

• RT service at an inter-domain peer
• CAC for RT service
• Algorithm
• Numerical results

23
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)

24
Approach 1 not distinguishing between e2e CoSs

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

25
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).

26
Analysis (1)
Figure 8. Time evolution of the system state

• 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)

27
Analysis (2)
After some algebra
the load (?) and the arrival intensities (?1, ?2)
are related by  
Eq.9
28
Analysis (3)
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
Eq.12
29
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.
Eq.14
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 r 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. r1w1r , r2w2r
30
Numerical results (1)
Figure 9. Total admissible load vs. packet size
ratio of two end-to-end CoSs target Ploss10-3
Figure 10. Packet loss ratio vs. packet size
ratio of two end-to-end CoSs target Ploss10-3
31
Numerical results (2)
Figure 11. Packet loss ratio vs. packet size
ratio of two end-to-end CoSs target Ploss10-2
Figure 12. Packet loss ratio vs. packet size
ratio of two end-to-end CoSs target Ploss10-4
32
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/mem
  bers/Artikuly/Admissible.pdf