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oth the traditional ack-based and the “new” rate-based protocols, the transport system flow classes can be defined as: - Constant bit-rate flow class (CBR) - Variable bit-rate flow class (VBR) - Transaction flow class (AAMt ) - Block-transfer stream flow class (AAMs ) - General connection flow class (AAMc ). Figure 5.2 illustrates the application and transport system flow classes defined and also the relationship between these classes and the specified ATM system flow classes defined within the present B-ISDN QoS framework. The unspecified QoS class is not included in Figure 5.2. 5.2 Application-oriented QoS service The OSI QoS parameters are QoS requirement and QoS data parameters. The ISDN performance parameters are QoS parameters, traffic parameters and NP parameters. These definitions are not consistent. A slightly changed definition is therefore used, where QoS parameters comprise QoS requirement and traffic flow parameters abbreviated to Q- and Fparameters respectively. We then have: Q-parameters: For the definition of QoS requirements for individual information units F-parameters: For the definition of the overall structure of the traffic flow pattern. Q (N),S ,F (N),S The index “S” indicates service, the index “P” indicates protocol. An additional index (N) indicates (N)-layer. See Figure 5.3. For a general (N)-layer, (N)-layer protocol entity Q (N),P ,F (N),P (N)-layer protocol entity the following questions must be answered: Q (N-1),S ,F (N-1),S - Is there an externally defined (N)-service? What is the (N)-layer Figure 5.3 The F- and Q-parameters related to a layer internal structure of flow classes, and what is the external visibility of Average these classes? Cell Frame - Are the (N+1)-layer 10-6 10-5 10-4 10-3 10-2 10-1 1 10 102103 F (N+1),P-parameters presented to the (N)-layer? If so, are the (N+1)- Time resolution (sec) layer parameters related Figure 5.4 Time regions to an (N+1)-layer or an (N)-layer flow class? 66 CBR VBR AAMt AAMs AMM CBR VBR ACMt ACMs ACMg A B X C D 1 1 2 Figure 5.2 Layered flow class functionality 2 3/4 5 3 4 Application flow classes Transport system flow classes ATM system service classes AAL protocol types ATM layer QoS classes - Similarly, are the Q (N+1),P -parameters related to an (N+1)-layer or an (N)layer flow class? For the transmission-oriented ATM QoSservice the (N+1)-layer states the functionality it wants, based on knowledge about the (N)-layer internal flow class structure. The (N+1)-layer declares its Fand Q-parameters with reference to an (N)-layer flow pattern model. The alternative application-oriented QoS-service is to let layer (N+1) declare which flow class it represents and also its F-parameters based on the pattern of its own declared class. The external (N)-layer functionality can optionally be specified. For B-ISDN, a simpler ATM system flow class structure than the one illustrated in Figure 5.1 is then made possible. Knowledge of the nature of the (N+1)layer traffic pattern can be useful within the (N)-layer, both for traffic handling functionality and traffic load estimations. Using the (N+1)-layer flow pattern as the reference for the service will conserve knowledge about the application traffic pattern. This can also give the (N)-layer the possibility to utilise the freedom caused from lack of one-to-one mapping between the two flow classes. For ATM, traffic shaping based on cell spacing can be applied, utilising the freedom defined in the application and transport system Fand Q-parameters ([3], [4]). 5.3 Time regions In a 160 Mbit/sec ATM network, the duration of a cell is 2–3 msec. The time resolution region related to the duration of single cells and sequences of cells is defined as the cell time region. Neither the applications nor the transport system will in the general case be able to operate in the cell time region. This fact is one of the reasons for defining various time regions to be used as a dimension for characterising the Q- and F-parameters and also the traffic handling functionality. In addition to the cell time region, the frame and the average time regions are introduced. The corresponding cell, frame and average processes describe the activities in the related time regions (Figure 5.4). The average process is the flow pattern related to a pre-defined average interval in the order of seconds or higher. The concept frame is a generalisation of the concept video-frame, which is typically between 25 and 40 msec. A frame is a significant application-related quantity
of information. The frame-time is the time for the “presentation” of this information. For image-related sources, the frame is one terminal screen. For sources with a “fixed” period, i.e. CBR, VBR and AAMs , the frame-time is the period of the generated flow pattern. For the application classes with neither periodicity nor real-time demanding human users (ex: distributed system traffic and mail traffic), the frame has no direct intuitive interpretation. The F-and Q-parameters for the (N)-service should be related to a time region applied in the (N+1)-layer operation. This is denoted as the QoS-service’s time region principle. It is meaningless to specify (N+1)-layer F- and Q-parameters that does not match the time resolution used in the (N+1)-layer. A transport system working in the 100 msec time region should not be forced to specify its parameters within the cell time region. 5.4 Layered co-operation and layered traffic contracts Layered co-operation means that the various elements of a communication task is delegated to various protocol layers. This is the basic idea behind layering. However, certain traffic handling functions such as flow control and multiplexing are duplicated rather than delegated. This is discussed by several authors ([28], [13] and [18]). By - avoiding multiplexing above the link layer - using an application-oriented QoS-service, and - using the time region principle, traffic handling functions such as flow control, usage parameter control and traffic shaping can be handled by co-operation ([3], [4]). As an example for B- ISDN, the transport system can do the traffic handling functionality in the average and frame time region. The ATM end-system must do the important mapping between the time regions and also the traffic shaping within the cell time region. The B-ISDN concept traffic contract is hereby generalised. An (N)-layer traffic contract is defined as the negotiated set of F-and Q-parameters {Q (N),S , F (N),S } of the (N)-layer service. The existing B- ISDN traffic contract is the realisation of such a layer traffic contract at the UNI. If a traffic contract between the ATM system service user and the ATM system Application Transport system Transport system traffic contract not based on GCRAs ATM system traffic contract not based on GCRAs ATM system based on frame and average time region concepts is introduced, then the ATM system could define another traffic contract for UNI based on F-and Q-parameters in the cell time region. This contract is directly deduced from the higher layer contract. UPC at the UNI with minimum uncertainty can only be obtained if the ATM system in the unit interfacing the UNI has responsibility for details of the contract. In this case the presented traffic load on the ATM links through the UNI can also be taken into consideration. Such a scheme is illustrated in Figure 5.5. With a layered contract scheme, there must be a well-defined ATM system service also comprising the control relationship illustrated in Figure 5.1. There must also be a well-defined traffic handling functionality in AAL. Physical layer SAP Cell scheduling based on GCRAs Figure 5.5 A layered traffic contract scheme for B-ISDN CBR CBR A 1 VBR VBR 1 2 2 TE functions effecting CDV AAM t AAM s AMM ACM t ACM s ACM c C D 3/4 5 N-2 N-1 N Figure 5.6 A revised B-ISDN flow class structure B A revised flow class structure based on an application-oriented QoS service is illustrated in Figure 5.6. By giving the responsibility for the selection of the internal ATM system flow class functionality to an ATM system QoS entity, a simpler application view of the ATM system is obtained. The internal ATM system flow class structure is also considerably simplified. 6 Summary Private UNI Private UNI traffic contract based on GCRAs Other CPE functions effecting CDV Application flow classes Public UNI The operational part of the OSI and ISDN QoS frameworks comprises: - A static structure of entities performing traffic handling functions - QoS-related parameters, and - QoS-services. UPC based on GCRAs Public UNI traffic contract based on GCRAs Transport system flow classes ATM/system QoS entity ATM System Service Classes AAL protocol types ATM layer QoS classes 67
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Contents Feature Guest editorial, A
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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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14 Table 2 Survey of some distribut
Page 18 and 19: 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
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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
Page 48 and 49: 46 Table 6. (x = 3). a n 0.0 0.1 0.
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
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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
Page 70 and 71: 68 With this as a basis, some modif
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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
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Page 82 and 83: 80 Similarly as for Poisson-traffic
Page 84 and 85: 82 throughput 1 Introduction Commun
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Page 90 and 91: 88 ers to use the same facility at
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116 class 1 class 2 class 3 [1,1,1]
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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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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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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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186 Level duration The state sojour
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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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230 Terminals/ Terminal Adapters
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232 plaintext Figure 1 The PNO Ciph
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