ETSI ETS 300 301 ed.1 (1995-03)

Broadband Integrated Services Digital Network (B-ISDN); Traffic control and congestion control in B-ISDN

DE/NA-052801

Širokopasovno digitalno omrežje z integriranimi storitvami (B-ISDN) – Krmiljenje prometa in zamašitev v B-ISDN

General Information

• Status: Published
• Publication Date: 15-Mar-1995
• Technical Committee: NA 5 - Broadband Networks
• Current Stage: 12 - Completion
• Due Date: 14-Mar-1995
• Completion Date: 16-Mar-1995
• Ref Project: SIST ETS 300 301 E1:2003 - Broadband Integrated Services Digital Network (B-ISDN); Traffic control and congestion control in B-ISDN

Standards Content (Sample)

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.Širokopasovno digitalno omrežje z integriranimi storitvami (B-ISDN) – Krmiljenje prometa in zamašitev v B-ISDNBroadband Integrated Services Digital Network (B-ISDN); Traffic control and congestion control in B-ISDN33.080Digitalno omrežje z integriranimi storitvami (ISDN)Integrated Services Digital Network (ISDN)ICS:Ta slovenski standard je istoveten z:ETS 300 301 Edition 1SIST ETS 300 301 E1:2003en01-december-2003SIST ETS 300 301 E1:2003SLOVENSKI
STANDARD



SIST ETS 300 301 E1:2003



EUROPEANETS 300 301TELECOMMUNICATIONMarch 1995STANDARDSource: ETSI TC-NAReference: DE/NA-052801ICS:33.080Key words:Broadband, ISDN, traffic, congestionBroadband Integrated Services Digital Network (B-ISDN);Traffic control and congestion control in B-ISDNETSIEuropean Telecommunications Standards InstituteETSI SecretariatPostal address: F-06921 Sophia Antipolis CEDEX - FRANCEOffice address: 650 Route des Lucioles - Sophia Antipolis - Valbonne - FRANCEX.400: c=fr, a=atlas, p=etsi, s=secretariat - Internet: [e-mail].: [phone] - Fax: [phone]Copyright Notification: No part may be reproduced except as authorized by written permission. The copyright and theforegoing restriction extend to reproduction in all media.© European Telecommunications Standards Institute 1995. All rights reserved.SIST ETS 300 301 E1:2003



Page 2ETS 300 301: March 1995Whilst every care has been taken in the preparation and publication of this document, errors in content,typographical or otherwise, may occur. If you have comments concerning its accuracy, please write to"ETSI Editing and Committee Support Dept." at the address shown on the title page.SIST ETS 300 301 E1:2003



Page 3ETS 300 301: March 1995ContentsForeword.51Scope.72Normative references.73Abbreviations.84General framework.84.1General objectives.84.2Generic functions.94.3A reference configuration for traffic control and congestion control.104.4Events, actions, time scales and response times.104.5QoS, NP and CLP.115Traffic descriptors and parameters.125.1Definitions.125.1.1Traffic parameters.125.1.2Traffic descriptors.125.2Requirements.125.3User-network traffic contract.135.3.1Traffic contract definition.135.3.2Source traffic descriptors, QoS and CLP.135.3.3Impact of CDV on UPC/NPC and resource allocation.135.4Traffic parameter specifications.155.4.1PCR.155.4.1.1PCR for a VPC/VCC.155.4.1.2PCR granularity specification.155.4.2Other traffic parameters.166Functions and procedures for traffic control and congestion control.166.1Introduction.166.1.1Traffic control and congestion control functions.166.2Traffic control functions.176.2.1NRM.176.2.1.1Use of VPs.186.2.1.2Other networking techniques.196.2.2CAC.206.2.2.1General.206.2.2.2Parameters for CAC.206.2.2.2.1Required QoS class.206.2.2.2.2Negotiation of traffic characteristics.216.2.2.3Resource allocation.216.2.3Usage parameter control and NPC.216.2.3.1UPC/NPC functions.216.2.3.2UPC/NPC requirements.226.2.3.2.1Performance of PCR UPC/NPC.236.2.3.3UPC location.246.2.3.4NPC location.256.2.3.5Traffic parameters subject to control at the UPC/NPC.256.2.3.6UPC/NPC actions.266.2.3.7Relationship between UPC/NPC and CLP.266.2.3.8Relationship between UPC/NPC, OAM and networkmanagement.276.2.4PC and selective cell discard.276.2.5Traffic shaping.286.2.6FRM.28SIST ETS 300 301 E1:2003



Page 4ETS 300 301: March 19956.3Congestion control functions.286.3.1Selective cell discard.286.3.2EFCI.296.3.3Reaction to UPC/NPC failures.29Annex A (informative):PCR monitor algorithms.30A.1Accounting for CDV tolerance.30History.31SIST ETS 300 301 E1:2003



Page 5ETS 300 301: March 1995ForewordThis European Telecommunication Standard (ETS) has been produced by the Network Aspects (NA)Technical Committee of the European Telecommunications Standards Institute (ETSI).The Broadband Integrated Services Digital Network (B-ISDN), which is based on the AsynchronousTransfer Mode (ATM) technique, is designed to transport a wide variety of traffic classes satisfying arange of transfer capacity needs and Network Performance (NP) objectives.The primary role of traffic control and congestion control parameters and procedures is to protect thenetwork and the user in order to achieve NP objectives. An additional role is to optimize the use ofnetwork resources.The uncertainties of broadband traffic patterns, traffic control and congestion control complexity suggest astep-wise approach for defining traffic parameters and network traffic control and congestion controlmechanisms. This ETS defines a restricted initial set of traffic control and congestion control capabilities,aiming at simple mechanisms and realistic network efficiency.It may subsequently be appropriate to consider additional sets of such capabilities, for which additionaltraffic control mechanisms will be used to achieve increased network efficiency.Transposition datesDate of latest announcement of this ETS (doa):30 June 1995Date of latest publication of new National Standardor endorsement of this ETS (dop/e):31 December 1995Date of withdrawal of any conflicting National Standard (dow):31 December 1995SIST ETS 300 301 E1:2003



Page 6ETS 300 301: March 1995Blank pageSIST ETS 300 301 E1:2003



Page 7ETS 300 301: March 19951ScopeThis European Telecommunication Standard (ETS) describes traffic control and congestion controlprocedures for the Broadband Integrated Services Digital Network (B-ISDN):-the main body describes the objectives and mechanisms of traffic control and congestion control(see CCITT Recommendation I.371 [1]);-examples of application of monitoring functions are given in annex A.In B-ISDN, congestion is defined as a state of network elements (e.g. switches, concentrators, cross-connects and transmission links) in which the network is not able to meet the negotiated NP objectives forthe already established connections and/or for the new connection requests.In general congestion can be caused by:-unpredictable statistical fluctuations of traffic flows;-fault conditions within the network.Congestion should be distinguished from the state where buffer overflow is causing cell losses, but stillmeets the negotiated Quality of Service (QoS).Asynchronous Transfer Mode (ATM) layer traffic control refers to the set of actions taken by the networkto avoid congested conditions.ATM layer congestion control refers to the set of actions taken by the network to minimize the intensity,spread and duration of congestion. These actions are triggered by congestion in one or more networkelements.2Normative referencesThis ETS incorporates by dated or undated reference, provisions from other publications. Thesenormative references are cited at the appropriate places in the text and the publications are listedhereafter. For dated references, subsequent amendments to or revisions of any of these publicationsapply to this ETS only when incorporated in it by amendment or revision. For undated references the latestedition of the publication referred to applies.[1]CCITT Recommendation I.371: "Traffic control and congestion control inB-ISDN".[2]CCITT Recommendation I.150: "B-ISDN Asynchronous Transfer Modefunctional characteristics".[3]CCITT Recommendation I.311: "B-ISDN General Networks Aspects".SIST ETS 300 301 E1:2003



Page 8ETS 300 301: March 19953AbbreviationsFor the purposes of this ETS, the following abbreviations apply:AALATM Adaptation LayerATMAsynchronous Transfer ModeCACConnection Admission ControlCBRConstant Bit RateCDVCell Delay VariationCEQCustomer EquipmentCLPCell Loss PriorityCLRCell Loss RatioCRFConnection Related FunctionsCRF(VC)Virtual Channel Connection Related FunctionsCRF(VP)Virtual Path Connection Related FunctionsEFCIExplicit Forward Congestion IndicationFIFOFirst In First OutFRMFast Resource ManagementGFCGeneric Flow ControlNNINetwork-Network InterfaceNPNetwork PerformanceNPCNetwork Parameter ControlNRMNetwork Resource ManagementOAMOperation And MaintenancePCPriority ControlPCRPeak Cell RatePDUProtocol Data UnitQoSQuality of ServiceSAPService Access PointSDUService Data UnitUNIUser-Network InterfaceVBRVariable Bit RateVCVirtual ChannelVCCVirtual Channel ConnectionVCIVirtual Channel IdentifierVPCVirtual Path ConnectionVPVirtual PathVPIVirtual Path Identifier4General framework4.1General objectivesThe objectives of ATM layer traffic control and congestion control for B-ISDN are as follows:-ATM layer traffic control and congestion control should support a set of ATM layer QoS classessufficient for all foreseeable B-ISDN services; the specification of these QoS classes should beconsistent with NP recommendations;-ATM layer traffic control and congestion control should not rely on ATM Adaptation Layer (AAL)protocols, which are B-ISDN service specific, nor on higher layer protocols, which are applicationspecific. Protocol layers above the ATM layer may make use of information which may be providedby the ATM layer, in order to improve the utility that those protocols can derive from the network;-the design of an optimum set of ATM layer traffic controls and congestion controls should minimizenetwork and end-system complexity while maximising network utilization.SIST ETS 300 301 E1:2003



Page 9ETS 300 301: March 19954.2Generic functionsTo meet these objectives, the following functions form a framework for managing and controlling trafficand congestion in ATM networks and may be used in appropriate combinations:-Network Resource Management (NRM): provisioning may be used to allocate network resources inorder to separate traffic flows according to service characteristics;-Connection Admission Control (CAC): is defined as the set of actions taken by the network duringthe call set up phase (or during call re-negotiation phase) in order to establish whether a VirtualChannel (VC)/Virtual Path Connection (VPC) request can be accepted or rejected (or whether arequest for re-allocation can be accommodated). Routeing is part of CAC actions;-feedback controls are defined as the set of actions taken by the network and by the users toregulate the traffic submitted on ATM connections according to the state of network elements;-Usage Parameter Control/Network Parameter Control (UPC/NPC) is defined as the set of actionstaken by the network to monitor and control traffic, in terms of traffic offered and validity of the ATMconnection, at the user access and the network access respectively. Their main purpose is toprotect network resources from malicious, as well as unintentional, misbehaviour which can affectthe QoS of other already established connections by detecting violations of negotiated parametersand taking appropriate actions;-Priority Control (PC): the user may generate different priority traffic flows by using the Cell LossPriority (CLP) bit, see CCITT Recommendation I.150 [2]. A congested network element mayselectively discard cells with low priority if necessary to protect, as far as possible, the NP for cellswith high priority;-other control functions are for further study.As a general requirement, it is desirable that a high level of consistency be achieved between the abovetraffic control capabilities.SIST ETS 300 301 E1:2003



Page 10ETS 300 301: March 19954.3A reference configuration for traffic control and congestion controlThe reference configuration used for traffic control and congestion control is given figure 1.B-NT1 B-TES B B-NT2 T B B-TEB-NT2 B-NT1 NPC Inter-network NNI S B T B Network A UPC - CAC - NRM
- PC- feedback control
- others- CAC - NRM
- PC- feedback control
- othersNetwork B UPC:Usage Parameter ControlNPC:Network Parameter ControlCACConnection Admission ControlNRM:Network Resource ManagementPC:Priority ControlOthers for further studyNOTE 1:NPC may also apply at some intra-network Network-Network Interfaces (NNIs).NOTE 2:The arrows indicate the direction of the cell flow.Figure 1: Reference configuration for traffic control and congestion control4.4Events, actions, time scales and response timesFigure 2 illustrates the time-scales over which various traffic control and congestion control functionsoperate. The response time defines how quickly the controls react. For example, cell discarding can reacton the order of the insertion time of a cell. Similarly, feedback controls can react on the time scale ofround-trip propagation times. Since traffic control and resource management functions are needed atdifferent time-scales, no single function is likely to be sufficient.SIST ETS 300 301 E1:2003



Page 11ETS 300 301: March 1995RESPONSE TIME Long term network engineering procedures, etc. Centralized network management controls, etc.Feedback controls, etc.
Cell discarding, priority control,
buffer management and cell service discipline,
traffic shaping, UPC, etc.Routeing, call set-up and admission control,
resource allocation, etc. Call / connection inter-arrival timeRound-trip
propagation timeCell / PDU
insertion timeTRAFFIC CONTROL AND CONGESTION CONTROL FUNCTIONS
ExamplesFigure 2: Control response times4.5QoS, NP and CLPThe ATM layer QoS is defined by a set of parameters such as delay and delay variation sensitivity, CellLoss Ratio (CLR), etc. Other QoS parameters are for further study.NOTE:In this case the Cell Delay Variation (CDV) effect applies to the network ---> userinformation traffic flow.A user requests a specific ATM layer QoS from the QoS classes which a network provides. This is part ofthe traffic contract at connection establishment (see subclause 5.3.1). It is a commitment for the networkto meet the requested QoS as long as the user complies with the traffic contract. If the user violates thetraffic contract, the network need not respect the agreed QoS.The selected QoS class may assign different objective values to the CLR computed on the CLP = 0 cellflow and on the aggregate CLP = 0+1 cell flow.NP objectives at the ATM Service Access Point (SAP) are intended to capture the network ability to meetthe requested ATM layer QoS. It is the role of the upper layers, including the AAL, to translate this ATMlayer QoS to any specific application requested QoS.SIST ETS 300 301 E1:2003



Page 12ETS 300 301: March 19955Traffic descriptors and parametersTraffic parameters describe traffic characteristics of an ATM connection. Traffic parameters are groupedinto source traffic descriptors for exchanging information between the user and the network.CAC procedures shall use source traffic descriptors to allocate resources and derive parameters for theoperation of UPC/NPC.5.1Definitions5.1.1Traffic parametersA traffic parameter is a specification of a particular traffic aspect. It may be qualitative or quantitative.Traffic parameters may, for example, describe Peak Cell Rate (PCR), average cell rate, burstiness, peakduration, and source type (e.g. telephone, videophone).Only PCR is presently defined in this ETS.Some of the above mentioned parameters are mutually dependent (e.g. the burstiness with the averagecell rate and PCR).5.1.2Traffic descriptorsThe ATM traffic descriptor is the generic list of traffic parameters which can be used to capture the trafficcharacteristics of an ATM connection.The introduction of additional parameters to enhance the NRM procedures or to capture trafficcharacteristics of a new type of connection is left open for further study.A description of the characteristics of the traffic that any given requested connection may offer has to beprovided by the user at the connection set-up.A source traffic descriptor is the set of traffic parameters belonging to the ATM traffic descriptor usedduring the connection set-up to capture the traffic characteristics of the connection requested by thesource.5.2RequirementsAny traffic parameter to be involved in a source traffic descriptor should:-be understandable by the user or his terminal;-enable conformance to be monitored by the network;-be appropriate for use by the network in resource allocation schemes (e.g. CAC), to enable NPrequirements to be met;-be enforceable by the UPC and NPC functions, to enable NP requirements to be met, in case ofnon-compliant usage.SIST ETS 300 301 E1:2003



Page 13ETS 300 301: March 19955.3User-network traffic contract5.3.1Traffic contract definitionCAC and UPC/NPC procedures require the knowledge of certain parameters to operate efficiently: theyshould take into account the source traffic descriptor, the requested QoS and the CDV tolerance (seesubclause 5.4) in order to decide whether the requested connection can be accepted.NOTE 1:In this case the CDV effect applies to the user ---> network information traffic flow.The source traffic descriptor, the requested QoS for any given ATM connection and the maximum CDVtolerance allocated to the Customer Equipment (CEQ) define the traffic contract at the TB reference point.Source traffic descriptors and QoS are declared by the user at connection set-up by means of signalling orsubscription. Whether the maximum allowable CDV tolerance is also negotiated on a subscription or on aper connection basis, is for further study.The CAC and UPC/NPC procedures are operator specific. Once the connection has been accepted, thevalue of the CAC and UPC/NPC parameters shall be set by the network on the basis of the networkoperator's policy.NOTE 2:All ATM connections handled by network Connection Related Functions (CRF) have tobe declared and enforced by the UPC/NPC. ATM layer QoS can only be assured forcompliant ATM connections. As an example, individual Virtual Channel Connections(VCCs) inside a user end-to-end VPC are neither declared nor enforced at the UPCand hence, no ATM layer QoS can be assured to them.5.3.2Source traffic descriptors, QoS and CLPIf a user requests two levels of priority for an ATM connection, as indicated by the CLP bit value, theintrinsic traffic characteristics of both cell flow components have to be characterized in the source trafficdescriptor. This is by means of a set of traffic parameters associated with the CLP = 0 component and aset of traffic parameters associated with the CLP = 0+1 component.As indicated in subclause 4.5, the network provides an ATM layer QoS for each of the components(CLP = 0 and CLP = 0+1) of an ATM connection. The traffic contract specifies the particular QoS choice(from those offered by the network operator) for each of the ATM connection components. There may bea limited offering of QoS specifications for the CLP = 1 component.CLR objectives are for further study.5.3.3Impact of CDV on UPC/NPC and resource allocationATM layer functions (e.g. cell multiplexing) may alter the traffic characteristics of ATM connections byintroducing CDV as illustrated in figure 3. When cells from two or more ATM connections are multiplexed,cells of a given ATM connection may be delayed while cells of another ATM connection are being insertedat the output of the multiplexer. Similarly, some cells may be delayed while physical layer overhead orOperation And Maintenance (OAM) cells are inserted. Therefore, some randomness affects the timeinterval between reception of ATM cell Data_Requests at the end-point of an ATM connection and thetime that an ATM cell Data_Indication is received at the UPC/NPC. Additionally, AAL multiplexing mayoriginate CDV.SIST ETS 300 301 E1:2003



Page 14ETS 300 301: March 1995The UPC/NPC mechanism should not discard or tag cells in an ATM connection if the source conforms tothe source traffic descriptor negotiated at connection establishment. However, if the CDV is not boundedat a point where the UPC/NPC function is performed, it is not possible to design a suitable UPC/NPCmechanism and to allocate resources properly. Therefore, it is required that a maximum allowable value ofCDV be standardized edge-to-edge, e.g. between the ATM connection end-point and TB, between TB andan inter-network NNI and between inter-network NNIs (see figure 1).Standardization of a number of CDV tolerance values, less than the maximum allowable value of CDVtolerance, to apply to certain interfaces (e.g. on a subscription basis or on a per connection basis) is forfurther study.UPC/NPC should accommodate the effect of the maximum CDV allowed on ATM connections within thelimit resulting from the accumulated CDV allocated to upstream subnetworks (including CEQ).Traffic shaping partially compensates for the effects of CDV on the PCR of the ATM connection. Examplesof traffic shaping mechanisms are re-spacing cells of individual ATM connections according to their PCR orsuitable queue service schemes.Values of the CDV are NP issues.AAL
(note 1)ATM
(note 2)PHY DATA INDICATION at the UPC(Connection A, X Mbit/s)(Connection B, Y Mbit/s)t 48 octets, X Mbit/s 48 octets, Y Mbit/s ATM
SAPPHY
SAPH H H H H H H H H H H H H H H H H OAM
F5 OAM
F4 Physical layer overhead DATA_INDICATION DATA_REQUESTH NOTE 1:ATM Service Data Units (SDUs) are accumulated at the upper layer service bit rate.Besides, CDV may also originate in AAL multiplexing.NOTE 2:Generic Flow Control (GFC) delay and delay variation is part of the delay and delayvariation introduced by the ATM layer.NOTE 3:CDV may also be introduced by the network because of random queueing delays whichare experienced by each cell in concentrators, switches and cross-connects.Figure 3: Origins of CDVSIST ETS 300 301 E1:2003



Page 15ETS 300 301: March 1995The definition of a source traffic descriptor and the standardization of a maximum allowable CDV may notbe sufficient for a network to allocate resources properly. When allocating resources, the network shouldtake into account the worst case traffic passing through UPC/NPC in order to avoid impairments to otherATM connections. This worst case traffic depends on the specific implementation of the UPC/NPC. Thetrade-offs between UPC/NPC complexity, worst case traffic and optimization of network resources aremade at the discretion of network operators. The quantity of available network resources and the NP to beprovided for meeting QoS requirements can influence these trade-offs.5.4Traffic parameter specificationsPCR is a mandatory traffic parameter to be explicitly or implicitly declared in any source traffic descriptor.In addition to the PCR of an ATM connection, it is mandatory for the user to declare either explicitly orimplicitly the CDV tolerance tt within the relevant traffic contract.Additional standardized parameters beyond PCR which may be specified in the future should provide for asignificant improvement of network utilization.5.4.1PCRThe following definition applies to ATM connections supporting both Constant Bit Rate (CBR) and VariableBit Rate (VBR) services.The PCR in the source traffic descriptor specifies an upper bound on the traffic that can be submitted onan ATM connection. Enforcement of this bound by the UPC/NPC allows the network operator to allocatesufficient resources to ensure that the performance objectives (e.g. for CLR) can be achieved.5.4.1.1PCR for a VPC/VCCLocation:at the Physical layer SAP for an equivalent terminal representing the VPC/VCC(this is only a reference configuration, see figure 4).Basic event:request to send an ATM Protocol Data Unit (ATM_PDU) in the equivalentterminal.Definition:the PCR of the ATM connection is the inverse of the minimum inter-arrival timeT between two basic events defined above. T is the peak emission interval ofthe ATM connection.The source traffic descriptor of the ATM connection currently reduces to the PCR defined above.It is noted that conformance control of the PCR by UPC/NPC requires that the CDV tolerance tt, allocatedto the upstream portion of the ATM connection, be specified (see subclause 5.3.1). Whether additionalparameters may be useful is for further study.On a terminal with a single AAL and without ATM layer OAM flows, location and basic event areequivalent to the following.Location:at the ATM layer SAP.Basic event:request to send an ATM_SDU.In order to properly allocate resources to a VPC/VCC, a PCR, as defined above, has to be defined foreach component of the ATM connection, i.e. the CLP = 0 substream (not including the OAM), theaggregate (CLP = 0+1) substream (where appropriate) and the OAM substream. The CDV toleranceaccounts for delay variation that will be present in respective cell substreams of the ATM connection.Their values and interpretation are defined by algorithms described in annex A.5.4.1.2PCR granularity specificationNetwork functions such as UPC/NPC cannot be requested to handle every specific PCR value but only arestricted, discrete and finite set of values. The ordered list of these values is referred to as the ATM PCRgranularity.SIST ETS 300 301 E1:2003



Page 16ETS 300 301: March 1995As for the PCR definition, the PCR granularity specification should also be based on the peak emissioninterval.The ATM PCR granularity and its coding are for further study.ATM PDU DATA_REQUESTUPC T B Peak cell rate
1/T CDV tolerance
MUX Shaper
T ATM layer Physical layerEquivalent terminal Equivalent
S B Trafficsource
1 Connection
endpoints Traffic
source
N Physical
layer functions PHY SAP Other CEQfunctionalities generating
CDV 1/TATM connection peak cell rateCell delay variation tolerance Figure 4: Reference configuration and equivalent terminal for the definition of the PCRof an
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