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228 The rules for preparation and approval of a TBR are the same as for ETSI Standards. For new TBRs the Normal Approval Procedure shall be used. For corrections or amendments the UAP might be used. In parallel to the ETSI PE the TBR shall be submitted on a GATT notification procedure. ETSI Technical Report ETSI Technical Reports (ETR) are prepared to provide - guidance and supporting information on a Standard or group of Standards and their application - ETSI recommendations on a subject or subject area which are not of such a nature that they are suitable for an (I-)ETS - an ETSI common position on an issue which is also being discussed in other bodies - various types of status reports. An ETR shall contain a scope statement clearly indicating the nature and status of its contents. As for standards, ETRs are prepared by an STC or a PT. In cases where there is consensus within a TC the final approval of an ETR takes place at the TC level. However, there is a period of two weeks after the TC approval where objections can be made by any ETSI member. If a consensus cannot be reached, the ETR is passed to ETSI Technical Assembly for further action, e.g. vote at a TA meeting. ETRs are available to the public. Technical Committee Reference Technical Report A Technical Committee Reference Technical Report (TCR-TR) is a document for use within ETSI. It is not available outside ETSI. Requirements contained in a TCR-TR are binding on all ETSI TCs and STCs concerned. TCR-TR may define reference models, terminology, structure of Standards, programme for ETSI projects, etc. Technical Committee Technical Report A Technical Committee Technical Report (TC-TR) is a document for use within ETSI TC. It is not available outside ETSI. It documents work within the TC which is of internal interest, but not, in general, of interest to other ETSI TCs. A TC-TR may contain requirements that are binding on the originating TC and its STCs.
ATM traffic activities in some RACE projects BY HARALD PETTERSEN Services in an ATM network may be based on different ATM Layer Bearer Capabilities. An ATM layer bearer capability specifies a combination of Quality of Service (QoS) commitments and ATM traffic parameters that are suitable for some applications and that allow for a specific multiplexing scheme at the ATM layer [1]. Several ATM layer bearer capabilities are currently under study by ITU and the ATM Forum: - Deterministic Bit Rate (DBR) - Statistical Bit Rate (SBR) (or Variable Bit Rate (VBR)) with possible distinction between ⋅ SBR Real Time (SBR-RT) ⋅ SBR Non Real Time (SBR-NRT) - ATM Block Transfer (ABT) - Available Bit Rate (ABR) - Unspecified Bit Rate (UBR). Deterministic Bit Rate (DBR) is used by connections requiring a Peak Cell Rate (PCR) continuously available during the whole connection, typically to support Constant Bit Rate (CBR) applications. However, cells may be emitted either at or below the PCR. Statistical Bit Rate (SBR) connections are characterised by traffic parameters in addition to the PCR, namely Sustainable Cell Rate (SCR) with a Maximum Burst Size Tolerance limiting the maximum number of consecutive cells that may be sent at the PCR. The distinction between Real-Time SBR and Non- Real-Time is based on whether there are end-to-end cell delay variation commitments or not. An ATM Block is a group of cells delineated by Resource Management (RM) cells. Using the ATM Block Transfer (ABT) bearer capability ATM Blocks are transmitted at a peak cell rate dynamically negotiated based on user requests by RM cells. There are two variants of this scheme, ABT with Delayed Transmission where the user is waiting on response from the network before cells are transmitted, and ABT with Immediate Transmission where the information is sent immediately after the request resource management cell. Available Bit Rate (ABR) can support applications that may adapt the information transfer rate to the currently available resources in the network based on feedback control messages from the network. The sources may increase the rate up to a specified maximum rate (PCR) and decrease down to a minimum usable cell rate (MCR). The Unspecified Bit Rate (UBR) is a best effort support for applications without any commitments from the network on QoS or transfer rate. The most suitable choice of bearer capability depends on the specific service or application to support, however, there is not a one-to-one correspondence between services and bearer capabilities. Depending on the bearer capabilities to be supported different requirements will be posed on the ATM switches and the traffic control functionality. The first ATM switches were developed with small buffers, typically in the order of 100 cell places per link, in order to obtain simple, common treatment of all service types in an integrated network. With small buffers in the switches the ATM cells will experience limited cell delay variation through the network, a favourable property for applications with strong real time requirements. Statistical multiplexing gain is possible with this kind of switches, i.e. additional traffic parameters (like SCR) are utilised to allow admission of more connections than when only using the peak cell rate, giving a statistical gain while still satisfying the QoS objectives. However, it is difficult to obtain high multiplexing gain for connections having high burstiness and high ratio between the peak cell rate and the link rate. For this type of connections it may be beneficial to have larger buffers in the switches, allowing bursts of cells to be stored, in order to achieve high network utilisation. This buffering causes higher variations in the cell transfer delays. Development of switches with large buffers typically started in the data communication industry making products for the LAN environment. ABT is another way to achieve statistical multiplexing gain for such sources by allocating the resources only when needed for transmitting the block of cells. In order to satisfy both the wish for high network utilisation and the requirement on limited variation in cell transfer delays for some applications, there is a trend in the direction of developing switches with separate logical buffers for different types of bearer capabilities combined with service disciplines depending both on the connection type and the negotiated traffic parameters. While switches with small buffers mainly have to rely on preventive traffic control schemes, the availability of larger buffers opens the possibility of making additional use of reactive congestion control mechanisms. This is of particular interest in LAN networks for applications that may adapt the information transfer rate to the resources in the network currently available. If these mechanisms are beneficial in a public ATM network with its geographical dimensions, widely different reaction times and complex meshed structure are being discussed. Special Interest Group on Traffic Control and ATM Performance ATM traffic control is of major importance to ensure a satisfying QoS to the customers, to secure that the network is robust towards overload and to achieve high network utilisation. A lot of activities are going on world wide to investigate these issues. The issues have been addressed in the RACE Programme through extensive theoretical investigations followed by experiments on ATM networks carried out in a lot of different projects. Within RACE a Special Interest Group (SIG) on Traffic Control and ATM Performance started in 1994 with the objectives of - Identifying and analysing relevant topics in the field of traffic control and ATM performance, having reference to standardisation and specification activities - Collecting information coming from the experimental and theoretical results produced by RACE projects - Defining areas of common interest for new experiments - Elaborating common position on hot topics in Traffic Control and ATM performance - Contributing to Common Functional Specifications within RACE. 229
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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.
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18 Frame 5 Equilibrium calculations
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20 j k λ ij µji λ ik µ ki λ ir
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22 14 Disturbed and shaped traffic
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24 200 184 150 100 50 0 25 26 27 28
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26 n * ooo---o A * M, V stream is n
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28 A-subscr. Network B-subscr. λ(
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30 Frame 6 Basic queuing model From
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32 Traffic sources (N) ⇒ III - -
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34 Since Gw (t) is the survivor fun
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36 - Mean response time depends onl
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38 Figure 38 Mixed international da
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40 3 Gaaren, S. LAN interconnection
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42 Solution of some problems in the
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44 Table 3 a. The “Loss” (in
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46 Table 6. (x = 3). a n 0.0 0.1 0.
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48 Telephone Systems” (published
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50 The life and work of Conny Palm
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52 mind that the seventies were bef
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54 of random traffic it is tacitly
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56 Architectures for the modelling
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58 QoS user Service catagories user
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60 (N)-service-user (N)-service-pro
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62 ACSE Presentation layer Session
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64 Traffic source 1 Traffic source
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oth the traditional ack-based and t
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68 With this as a basis, some modif
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70 300 250 200 150 100 50 0 100 90
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72 Erl kErl 50 40 30 20 10 0 8 10 1
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74 Si: extreme high n s n s normal
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76 cost increase which must be cove
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78 with two to four hours read-out,
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80 Similarly as for Poisson-traffic
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82 throughput 1 Introduction Commun
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84 processor load Figure 4 its cust
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86 load control mechanisms. It is u
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88 ers to use the same facility at
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90 CE CE Figure 3 IRIM with cluster
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92 and one mini IRSU and one normal
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Table 4 Combined signalling and pac
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96 mission cost of large capacities
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40 30 20 10 98 TE-network TE-region
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100 change the routing for the next
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102 According to our plans reroutin
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104 Based on the experiences with t
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user access device 106 sound/speech
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108 overs for mobile stations that
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110 radio interface tion inside a b
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Figure 9 One way of defining space
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114 frequency code here. However, t
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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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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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