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68 With this as a basis, some modifications as well as new aspects have been proposed. Within this paper, the QoS parameters have been classified as QoS requirement parameters (Q-parameters) and traffic flow parameters (F-parameters). The proposed solution is based on an application-oriented QoS-service formally defined by layered traffic contracts, consisting of a negotiated set of Qand F-parameters. Time-regions are made visible as a dimension in the characterisation of Q-parameters, F-parameters and traffic handling functionality. A telecommunication service providing system shall satisfy the requirements of the applications. A QoS architecture based on an application-oriented flow classification of the total layered functionality seems therefore to be the appropriate choice. This will conserve knowledge about the application Q- and F-parameters. By avoiding multiplexing above the link layer, QoS-related cooperation between the layers is made possible. Such a solution gives a flexible and flow-harmonised architecture. References 1 Aagesen, F A, Helvik, B E. On excess process policing in B-ISDN networks. I: 13th International teletraffic congress (ITC 13). North-Holland, Elsevier Science Publishers, 1991. 2 Aagesen, F A. On source spacing in B-ISDN. Trondheim, SINTEF, 1992. (Report STF 40 A92140.) 3 Aagesen, F A. A flow management architecture for B-ISDN. IBCN&N, Copenhagen. North Holland, Elsevier, 1993. 4 Aagesen, F A. ATM system service primitives and flow management functionality : a design proposal. Trondheim, SINTEF, 1993. (Report STF40 A93157.) 5 Aagesen, F A. QoS in layered architecture. Trondheim, SINTEF, 1994. (Report STF40 F94088.) 6 Aagesen, F A. On a quality of service operational architecture. IFIP SEA- COMM’94, Kuala Lumpur, October 1994. 7 Anastasi, G et al. TPR : a transport protocol for real-time services in an FDDI environment. I: International workshop on protocols for high speed networks, IFIP WG 6.1/6.4, 1990. 8 The ATM Forum. ATM user-network interface specification version 3.0, September 10, 1993. 9 Biersack, E W et al. Gigabit networking research at Bellcore. IEEE network, 6(2), 1992. 10 Cheriton, D R. VMTP as the transport layer for high-performance distributed systems. IEEE communication magazine, June 1989. 11 Chesson, G. XTP/PE design considerations. International workshop on protocols for high speed networks, IFIP WG 6.1/6.4. Zurich, May 1989. 12 Clarc, D D, Lambert, M L, Zhang, L. NETBLT : a bulk data transfer protocol. Network Working Group RFC 998. 13 Clarc, D D. Architectural issues for a new generation of protocols. I: Proceedings of Sigcomm 90, September 1990. 14 Danthine, A et al. The OSI 95 connection-mode transport service : the enhanced QoS. I: 4th IFIP conference on high performance networking, Liege, December 1992. 15 Dabbous, W S. RTTP : real-time transport protocol. I: International workshop on protocols for high speed networks, IFIP WG 6.1/6.4. Zurich, May 89. 16 Doeringer, W A et al. A survey of light-weight transport protocols for high-speed networks. IEEE transactions on communication, 38(11), 1990. 17 ITU-T. E.800: terms and definitions related to the quality of telecommunication services, quality of service and dependability vocabulary. Geneva, 1993. (ITU-T Blue Book, fascicle II.3.) 18 Feldmeier, D C. Multiplexing issues in communication system design. I: Proceedings of the Sigcomm 90, September 1990. 19 Hehman, D B et al. High-speed transport systems for multi-media applications. I: International workshop on protocols for high speed networks, IFIP WG 6.1/6.4. Zurich, May 1989. 20 CCITT. Recommendations, general structure. Geneva, 1988. (CCITT Blue Book, vol III – fascicle III.7, Part I – I.100-series.) 21 CCITT. Recommendations, service capabilities. Geneva, 1988. (CCITT Blue Book, vol III – fascicle III.7, part II – I.200-series.) 22 CCITT. Recommendations, overall network aspects and functions. Geneva, 1988. (Blue Book, vol III – fascicle III.8, part III - I.300-series.) 23 Nordmark, E, Cheriton, D R. Experiences from VMTP : how to achieve low response time. I: IFIP WG 6.1/6.4, International workshop on protocols for high speed networks, Zürich, May 1989. 24 XTP protocol definition, rev. 3.5. Protocol Engine Inc., September 1990. 25 ISO. Revised text for ISO/IEC DIS 8073 – information technology – telecommunication and information exchange between systems – connection oriented transport protocol specification, Geneva, 1991. (ISO/IEC JTC1/SC6 N6776.) 26 ISO. Information technology – transport service definition for open systems interconnection. Geneva, 1993. (ISO/IEC DIS 8072.) 27 ISO. Quality of service framework, Working Draft no. 2. SC21/WG1 meeting, Yokohama, 1993. (ISO/IEC JTC1/SC21.) 28 Tennenhouse, D L. Layered multiplexing considered harmful? I: International workshop on protocols for high speed networks, IFIP WG 6.1/6.4. Zurich, May 1989.
Observed traffic variations and their influence in choice of intensity measurement routine BY ASKO PARVIALA Abstract In this paper the traditional understanding of stabilities and predictability of the traffic profiles and models have been weighted against the observations. In Helsinki Telephone Company, several wide scale traffic measurement studies were made in the 1980s, in order to expose how regular the traffic variations are. These measurements indicated that the conventional understanding about the stability of the repeating profiles, together with the popular traffic models during the busy hour, is dubious. This has, even in the international standardisation, caused a need to rethink the traffic intensity measurement routines, as a basis for the dimensioning of networks. 1 Measurements of traffic characteristics and dimensioning The quality of telecommunications services depends on the network bottlenecks, whereas the overdimensioning of other parts in the network does not improve the service. Existing or expected bottlenecks are revealed by measuring the real traffic. Directly measurable are the quality characteristics observable by the subscriber; like congestion, waiting time, or failure rate. This information is used to control the offered service quality, but it is also necessary for immediate measures, such as fault hunting and repair. The quality characteristics are non-linear: they deteriorate fast as the load increases, approaching the network’s capacity limits. So, these are not usable in forecasting. But the load, measured in erlangs, bits per second, etc., is linearily related to the use of the service, and thus forecastable, e.g. by time series. Therefore, the network is dimensioned for a dimensioning hour intensity, calculated according to certain rules from the measured peak intensities. In determining the required number of circuits or other capacities, a mathematical model is used, which combines the intensity, the nominal quality norm and assumptions of statistical properties of traffic (distribution of call intervals and holding times), concerning the network structure in question (single circuitgroups, alternative routing, waiting opportunities). It has been popular to assume a statistical equilibrium and the Poisson-distribution for the offered traffic during the dimensioning hour. Many academical theories have been created and presented on this or a slightly modified basis. How to constitute the dimensioning hour has met with less interest. The total service quality over a year is a result of the representativity of the dimensioning hour among all hours of the year, together with accuracy of the model, and the nominal congestion during that hour. It could be presented in number of minutes in the year without service, caused by the network’s bottlenecks. 2 Measurements of intensity The measurement costs concern the reserved equipment, the work of preparing and starting the measurements, and the logical handling, pruning and reporting of the measurement data. A balance will be searched between the costs of the carried measurements and the disadvantages caused by the intensities which are not measured. Among the disadvantages are unknown or unexpected breakdowns of the service quality, and unoptimal augmentations in the network. There are two different approaches with the following measurement routines: - Scheduled routines which minimise the measurement periods and the data to be handled by concentrating on the expected high value periods only. The nominal congestion is kept low in order to compensate the presumably lost peak intensities left outside the measurement periods. This also results in a high dependency on the mathematical model, and a high investment level due to the loose dimensioning. These routines are the traditional way of dimensioning, trying to minimise the use of separate measuring equipment, which is expensive in use due to lots of manual handling of data. - Continuous routines which activate the measurements all the time. The abundance of data is pruned in the earliest phase by searching the relevant peak intensities. The nominal congestion can be higher while no compensation for lost peak intensities outside the measurement periods is needed. This results in smaller dependency on the mathematical model, and in a lower investment level due to the possibility of focusing augmentation of the network equipment correctly. These routines are in use today, the measurements using just the basic data produced all the time by the exchange control processor(s). The worst choice is to create complex but inaccurate measurements, needing a low nominal congestion. Even this choice has been made by some operators. Every circuit-group between two points has its traffic capacity, which depends on the number of its circuits. If it is a potential bottleneck, it must be measured distinctly. But if, instead of one, several circuit-groups in parallel, or an overflow cluster, or a network between two subscriber groups, is considered, then the traffic capacity of the studied circuitgroup is no more constant, but lower, depending on the traffic caused by other circuit-groups. This complicates the dimensioning and the traffic management, calling for special measures by measurements. Complications of this kind are less common in a radial network structure, there including the cases where circuit-groups for reliability reasons are divided into two similar groups with symmetrically offered traffic. In comprehensive telecommunications courses is commonly taught that the offered teletraffic consists of rather regular variations, obeying annual, weekly and daily rhythms, and random Poissonian distribution during the dimensioning hour, the busy hour. If these assumptions are valid, it is sufficient to measure the busy hour intensities during a few days annually only – the rest of the year can be ignored – and to dimension by the Erlang formulae and their derivatives. The elementary conceptions in question concern the existence of the year’s high season, its annual consistency, the peak-hour’s consistency between seasons, representativity of the average day, the absence of peak loads outside the day’s peak-hour, the statistical balance and Poissonian distribution during the peak-hour. Both the rule to select the dimensioning hour and the mathematical model originated early in this century, from manual exchanges, and communication needs of the past society. They have sometimes been called into question, but they have been persistently favoured by some influential organisations. The new telecommunication networks, the new services and the nearly total renewal of users, have only to a limited extent influenced the common views. While the word “busy hour” has been used ambiguously, it is avoided here by talking about the peak-hour as a postselected hour having the highest inten- 69
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Contents Feature Guest editorial, A
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2 costs will be such that decisions
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4 N sources 1 The delay along the p
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6 Sunday Monday Tuesday Wednesday T
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BPS 800.000 8 700.000 600.000 500.0
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10 where the contributions from dif
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12 1.75 1.50 1.25 1.00 0.75 0.50 0.
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14 Table 2 Survey of some distribut
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16 0 Local calls mean: 27 sec. Std.
Page 20 and 21: 18 Frame 5 Equilibrium calculations
Page 22 and 23: 20 j k λ ij µji λ ik µ ki λ ir
Page 24 and 25: 22 14 Disturbed and shaped traffic
Page 26 and 27: 24 200 184 150 100 50 0 25 26 27 28
Page 28 and 29: 26 n * ooo---o A * M, V stream is n
Page 30 and 31: 28 A-subscr. Network B-subscr. λ(
Page 32 and 33: 30 Frame 6 Basic queuing model From
Page 34 and 35: 32 Traffic sources (N) ⇒ III - -
Page 36 and 37: 34 Since Gw (t) is the survivor fun
Page 38 and 39: 36 - Mean response time depends onl
Page 40 and 41: 38 Figure 38 Mixed international da
Page 42 and 43: 40 3 Gaaren, S. LAN interconnection
Page 44 and 45: 42 Solution of some problems in the
Page 46 and 47: 44 Table 3 a. The “Loss” (in
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Page 50 and 51: 48 Telephone Systems” (published
Page 52 and 53: 50 The life and work of Conny Palm
Page 54 and 55: 52 mind that the seventies were bef
Page 56 and 57: 54 of random traffic it is tacitly
Page 58 and 59: 56 Architectures for the modelling
Page 60 and 61: 58 QoS user Service catagories user
Page 62 and 63: 60 (N)-service-user (N)-service-pro
Page 64 and 65: 62 ACSE Presentation layer Session
Page 66 and 67: 64 Traffic source 1 Traffic source
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Page 74 and 75: 72 Erl kErl 50 40 30 20 10 0 8 10 1
Page 76 and 77: 74 Si: extreme high n s n s normal
Page 78 and 79: 76 cost increase which must be cove
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Page 82 and 83: 80 Similarly as for Poisson-traffic
Page 84 and 85: 82 throughput 1 Introduction Commun
Page 86 and 87: 84 processor load Figure 4 its cust
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Page 90 and 91: 88 ers to use the same facility at
Page 92 and 93: 90 CE CE Figure 3 IRIM with cluster
Page 94 and 95: 92 and one mini IRSU and one normal
Page 96 and 97: Table 4 Combined signalling and pac
Page 98 and 99: 96 mission cost of large capacities
Page 100 and 101: 40 30 20 10 98 TE-network TE-region
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Page 104 and 105: 102 According to our plans reroutin
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Page 108 and 109: user access device 106 sound/speech
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1.00E-00 1.00E-01 1.00E-02 case I c
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400 300 200 100 25 25 20 10 120 (a)
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Erlang Erlang Erlang 122 7 6 5 4 3
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124 Table 6 Call holding times (in
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Registered number of calls Register
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Table 9 Number of call attempts, su
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130 LAN Interconnection Traffic Mea
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132 gering table could be employed
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134 OSI name/layer 7) Application 6
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136 kbit/s 4000 3000 2000 1000 0 kb
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138 - The external LAN traffic is e
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Number of type 2 connections 140 Fe
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142 Number of type 2 connections No
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144 Number of type 2 connections Fi
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146 Preliminary studies indicate th
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148 Background Traffic Test Traffic
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150 ATM cell header 2.1.1 Measuring
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152 δ τ Figure 8 Deterministic in
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154 and CMR measurements was set to
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156 Sparc2 (SunOS 4.1.1) or Sparc10
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158 Segment size [byte] 8192 6144 4
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160 Throughput [Mbit/s] Throughput
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162 Segment size [byte] Unacknowled
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164 Throughput [Mbit/s] 30 20 4 kby
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166 Throughput [Mbit/s] Throughput
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168 TEL A TEL B Satellitedish Swiss
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170 Cell Discard Ratio Cell Discard
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172 Number of Type 2 Sources Number
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174 Synthetic load generation for A
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176 The type of the modulated proce
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178 Transp. Network LLC MAC PHY Tra
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180 0.005 0.004 0.003 0.002 0.001 0
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182 Number of active sources of the
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184 that these times are identicall
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186 Level duration The state sojour
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188 are summarised, before potentia
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190 Figure 4.4 Excerpt from the ATM
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192 4.2.6 Load extremes By specifyi
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194 14th international teletraffic
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196 how this change in “event rat
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advantage is that it is generally v
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200 ˜X = X + β(C − E(C)) (5.1)
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202 Table 3 Case 1: N = 4, λ/µ =
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204 A(t) 1 x - A on off Ti Pji Pij
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206 6.1.3 Control variables The num
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208 Some important queuing models f
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210 � � � A(ζ) � ζn �
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212 The main reason for giving (2.5
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214 M 0 0 1 For the sake of simplic
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218 cell-loss 10 0 10 -1 10 -2 10 -
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220 Notes on a theorem of L. Takác
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226 Documents types that are prepar
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228 The rules for preparation and a
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230 Terminals/ Terminal Adapters
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232 plaintext Figure 1 The PNO Ciph
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