Presentation on theme: "Halina Tarasiuk, Robert Janowski and Wojciech Burakowski Warsaw University of Technology, Poland Admissible Traffic Load of Real Time Class of Service."— Presentation transcript:
Halina Tarasiuk, Robert Janowski and Wojciech Burakowski Warsaw University of Technology, Poland Admissible Traffic Load of Real Time Class of Service for Inter-domain Peers
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 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) 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) Adaptive Resource Control for QoS Using an IP-based Layered Architecture (IST-1999-10077) Adaptive Resource Control for QoS Using an IP-based Layered Architecture
Admission Control Admission Control Agent End-user Application Toolkit Resource Control Layer Core Router Access Network Edge Router Setting Resource Control Resource Control Agent Setting Consideration of Network Load Monitoring Probing Results AQUILA Architecture resources QoS Request
QoS in core networks – IP prototype solutions: AQUILA few Goal: only a 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) Where Buffer denotes buffer size in packets and P loss target packet loss ratio.
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
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) 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 (d 2 /d 1 = d) Figure 8. Time evolution of the system state
Analysis (2) the load ( ) and the arrival intensities ( 1, 2 ) are related by: 1 = 1 d 1 = 1 (since d 1 =1); 2 = 2 d 2 = 2 d; = 1 + 2 1 =w 1 ; 2 = w 2 After some algebra Eq.9
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
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. 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 =w 1, 2 =w 2 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
Numerical results (2) 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
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
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