1、 ETSI ES 283 039-3 V1.1.2 (2007-06)ETSI Standard Telecommunications and Internet converged Services andProtocols for Advanced Networking (TISPAN);Specification of protocols requiredto support the NGN Overload Control Architecture;Part 3: Overload and Congestion Control for H.248 MG/MGCETSI ETSI ES 2
2、83 039-3 V1.1.2 (2007-06) 2 Reference RES/TISPAN-03102-3-NGN-R1 Keywords control, protocol ETSI 650 Route des Lucioles F-06921 Sophia Antipolis Cedex - FRANCE Tel.: +33 4 92 94 42 00 Fax: +33 4 93 65 47 16 Siret N 348 623 562 00017 - NAF 742 C Association but non lucratif enregistre la Sous-Prfectur
3、e de Grasse (06) N 7803/88 Important notice Individual copies of the present document can be downloaded from: http:/www.etsi.org The present document may be made available in more than one electronic version or in print. In any case of existing or perceived difference in contents between such versio
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8、1.1.2 (2007-06) 3 Contents Intellectual Property Rights4 Foreword.4 1 Scope 5 1.1 Applicability.5 2 References 5 3 Definitions and abbreviations.6 3.1 Definitions6 3.2 Abbreviations .6 4 AGW - MGC OverLoad Control Mechanism6 4.1 AGW-MGC Overload Scenarios7 4.2 AGW-MGC Overload Control Mechanism .7 5
9、 H.248 Details7 5.1 ETSI Notification Behaviour Package .8 5.1.1 Properties 8 5.1.2 Events .9 5.1.3 Signals 9 5.1.4 Statistics9 5.1.5 Error Codes.9 5.1.6 Procedures.9 5.1.6.1 Actions At An Overloaded MGC10 5.1.6.2 Actions At An AGW.11 5.1.6.2.1 Activation of AGW Regulating Mechanism .11 5.1.6.2.2 AG
10、W Behaviour During Regulating Mechanism12 5.1.6.2.3 Reduction of Regulating Level at AGW .12 5.1.6.2.4 Termination of Regulating Mechanism on the AGW12 5.1.6.2.5 Receipt of H.248 Signalling on a termination during Regulating Mechanism 12 5.1.6.3 MGC Failure .13 5.1.6.4 AGW Failure.13 6 Management Re
11、quirements13 6.1 Configuration of parameters relating to reduction of restriction rate .13 6.2 AGW Statistics.13 Annex A (informative): Message Flows15 Annex B (informative): AGW Load State Behaviour .26 Annex C (informative): AGW Regulating Behaviour.27 Annex D (informative): Bibliography.28 Histor
12、y 29 ETSI ETSI ES 283 039-3 V1.1.2 (2007-06) 4 Intellectual Property Rights IPRs essential or potentially essential to the present document may have been declared to ETSI. The information pertaining to these essential IPRs, if any, is publicly available for ETSI members and non-members, and can be f
13、ound in ETSI SR 000 314: “Intellectual Property Rights (IPRs); Essential, or potentially Essential, IPRs notified to ETSI in respect of ETSI standards“, which is available from the ETSI Secretariat. Latest updates are available on the ETSI Web server (http:/webapp.etsi.org/IPR/home.asp). Pursuant to
14、 the ETSI IPR Policy, no investigation, including IPR searches, has been carried out by ETSI. No guarantee can be given as to the existence of other IPRs not referenced in ETSI SR 000 314 (or the updates on the ETSI Web server) which are, or may be, or may become, essential to the present document.
15、Foreword This ETSI Standard (ES) has been produced by ETSI Technical Committee Telecommunications and Internet converged Services and Protocols for Advanced Networking (TISPAN). The present document is part 3 of a multi-part deliverable covering the Telecommunications and Internet converged Services
16、 and Protocols for Advanced Networking (TISPAN); Specification of protocols required to support the NGN Overload Control Architecture, as identified below: Part 1: “Overview“; Part 2: “Overload and Congestion control; GOCAP“; Part 3: “Overload and Congestion Control for H.248 MG/MGC“; Part 4: “Adapt
17、ative Control for the MGC“. ETSI ETSI ES 283 039-3 V1.1.2 (2007-06) 5 1 Scope The present document describes an extension to H.248.1 gateway protocol to enable a robust overload control mechanism to be implemented between Access media GateWays (AGWs) and their associated Media Gateway Controllers (M
18、GCs). This proposal is intended to provide a resolution to a specific known NGN architectural issue that needs to be resolved within the NGN release 1 time frame. The proposal is targeted at reference 1 and is independent of the H.248 core protocol version. 1.1 Applicability The Access media GateWay
19、/MGC Overload Control Protocol is applicable for: analog line interfaces with Analog Line Signalling (ALS), corresponding AMG H.248 Terminations are of type analog line (ALN); interfaces with Channel Associated Signalling (CAS). The Access media GateWay/MGC Overload Control Protocol is not applicabl
20、e for: all interface types with Common Channel Signalling (CCS) for controlling the corresponding bearer connections at the AMG, e.g.: a) ISDN B-channels of ISDN BRIs; b) ISDN B-channels of ISDN PRIs; c) V5.1 B-channels of V5.1 interfaces; d) V5.2 B-channels of V5.2 interfaces; or e) any narrowband
21、Access Node interface with CCS. NOTE 1: CCS traffic is relayed in this kind of AGW by embedded SIGTRAN Signalling Gateways (SG). Such a SG type terminates layer 2 of the control plane protocol stack (e.g. Q.921 3) and passes the layer 3 signalling (e.g. Q.931 4) transparently to the associated MGC.
22、The AGW therefore has no capability to detect start of call events nor provide address digit analysis. NOTE 2: Extending the AGW type (of note 1) by an additional capability of “monitoring layer 3 call control signalling“ may allow the application of the MGC Overload Control Protocol for CCS interfa
23、ces. However, such a concept is for further study. 2 References The following documents contain provisions which, through reference in this text, constitute provisions of the present document. References are either specific (identified by date of publication and/or edition number or version number)
24、or non-specific. For a specific reference, subsequent revisions do not apply. For a non-specific reference, the latest version applies. Referenced documents which are not found to be publicly available in the expected location might be found at http:/docbox.etsi.org/Reference. NOTE: While any hyperl
25、inks included in this clause were valid at the time of publication ETSI cannot guarantee their long term validity. 1 ITU-T Recommendation H.248.1: “Gateway control protocol: Version 3“. ETSI ETSI ES 283 039-3 V1.1.2 (2007-06) 6 2 ITU-T Recommendation Q.543: “Digital exchange performance design objec
26、tives“. 3 ITU-T Recommendation Q.921: “ISDN user-network interface - Data link layer specification“. 4 ITU-T Recommendation Q.931: “ISDN user-network interface layer 3 specification for basic call control“. 3 Definitions and abbreviations 3.1 Definitions For the purposes of the present document, the
27、 following terms and definitions apply: call attempt: attempt to setup a path to carry user data between end users callRejectRatio: percentage of call attempts that should be rejected by an AGW load: total number of call attempts in a given interval of time load state: percentage of call attempts th
28、at are currently being rejected by a MGC Media Gateway Controller overload: point at which the number of call attempts presented to an MGC exceeds its engineered processing capacity for a significant period of time, excluding momentary peaks 3.2 Abbreviations For the purposes of the present document
29、, the following abbreviations apply: AGW Access media GateWay ALS Analog Line Signalling BRI Basic Rate Interface CAS Channel Associated Signalling CCS Common Channel Signalling IP Internet ProtocolMGC Media Gateway Controller NGN New Generation Networks OL OverLoad PRI Primary Rate Interface RTP Re
30、al-Time Transport Protocol RTP/AVP Real-Time Protocol Audio-Video Profile SG Signalling Gateways SNMP Simple Network Management Protocol 4 AGW - MGC OverLoad Control Mechanism The purpose of the present specification is to define an overload control mechanism between Access media GateWays (AGWs) and
31、 their associated Media Gateway Controllers (MGCs) in an NGN. This mechanism is concerned solely with MGC overload due to excessive originating call attempts from dependent AGWs. Additional mechanisms (which are out of scope of the present document) must also be employed to provide an overall overlo
32、ad control solution/strategy in a NGN. ETSI ETSI ES 283 039-3 V1.1.2 (2007-06) 7 4.1 AGW-MGC Overload Scenarios In an NGN there exists the possibility that there will be many thousands of AGWs connected to a single MGC. With such an architecture it is envisaged that it may only require a moderate in
33、crease in call attempt levels across all of the AGWs to cause a MGC to become overloaded. In the case of media-stimulated events (e.g. tele-voting) or in the event of a disaster, there is often a large step change in the level of call attempts. In the NGN architecture, such an event is likely to gro
34、ssly overload the MGCs to a level where service may cease completely. With such large numbers of AGWs connected to a single MGC it will be necessary to efficiently, and quickly, propagate information relating to the MGC overload back to its dependant AGWs, allowing the AGWs to immediately take preve
35、ntative action, and thus quickly reduce the level of load that is being offered to the overloaded MGC. 4.2 AGW-MGC Overload Control Mechanism The high level requirement is to enable the rate of new originating calls that are generated by an AGW to be reduced during conditions of MGC overload, whilst
36、 at the same time permitting priority calls to be admitted (e.g. calls to an emergency operator). The basic premise of the load control mechanism is that the MGC is able to invoke a regulating capability on the AGW when the MGC is in overload. This is achieved by sending a H.248 MODIFY message again
37、st the ROOT termination with a new package (see clause 5.2) that is recognized by the AGW as being indicative of MGC overload, and contains an indication of the amount of load to be regulated by the AGW. Since the AGW is unaware of the concept of a “call“, it is proposed that the AGW shall regulate
38、the level of new Off-Hook notifications it offers to the overloaded MGC to the level that has been signalled by the MGC. A new Off-Hook is identified at the AGW via detection of an Off-Hook event at a termination that is in the NULL context. The proposed mechanism enables the MGC to quickly propagat
39、e information relating to its overload, and the proportion of Off-Hooks that its dependant AGWs should be regulating in order to reduce the offered load to the MGC. The purpose of the control mechanism is to maintain high effective throughput at an overloaded MGC subject to bounding MGC response tim
40、es, i.e. keeping the response times short enough to prevent customer reattempts. The new package would be used by the MGC on the occurrence of either a new originating / terminating a call from/to a dependent AGW to enable regulation of new Off-Hook notifications. Under this proposal, AGWs will, dur
41、ing a MGC overload, regulate any new Off Hook notifications based upon the current level signalled from the MGC. Off Hook notifications that are accepted by the regulation mechanism are passed onto the MGC and handled normally. For those calls that are regulated by the filtering mechanism, then the
42、AGW must first determine if is the line is initiating a priority call. The AGW does this by autonomously responding to the Off Hook notification by applying standard dial tone and then, if necessary, collecting and comparing signalled digits with pre-defined simple digit strings. The signalled digit
43、s will be sufficient to enable the AGW to distinguish between priority digit strings and non-priority digit strings. If the digit string is determined to be a priority string then a notification is sent to the MGC to enable the “priority call“ to be handled. If the digit string is determined to be a
44、 non-priority string then the AGW applies an autonomous line/port control functionality defined by a pre-configured script/data. In essence, this script defines a sequence of signals that are applied to the line so that the expected behaviour of the calling party is to hang up and re-attempt the o/g
45、 call at a later time. The sequence of signals covers the playing of appropriate indications (e.g. network busy tone) together with appropriate line feeds to eventually return the line to an idle state. As the overload abates on the MGC, the regulation level on the AGWs shall be eventually reduced b
46、ack to zero and normal operation shall resume. 5 H.248 Details A new package is introduced to convey the degree of overload at the (overloaded) MGC to the dependent AGWs. This package is based upon the Notification Behaviour (nb) package that has been defined in ITU-T Recommendation H.248.1 1. The m
47、ain difference is that this package may be applied to AGWs that support any version of H.248. ETSI ETSI ES 283 039-3 V1.1.2 (2007-06) 8 5.1 ETSI Notification Behaviour Package Package Name: ETSI Notification Behaviour Package. PackageID: etsi_nb (0x00a4). Version: 1. Description: This package enable
48、s the MGC to convey its degree of overload to the AGW. Extends: None. 5.1.1 Properties Property Name: Notification Regulation. PropertyID: notreg (0x0001). Description: This property duplicates the name of a corresponding property in ITU-T Recommendation H.248.1 1. However, in this package, it conve
49、ys the percentage of Off-Hook notifications from terminations in the NULL context that should be regulated by an AGW. The property applies to the ROOT termination. Type: Integer. Possible Values: 0 through to 100. A value of 0 means that no regulation shall occur on the AGW (i.e. normal behaviour). A value of 100 means that all Off-Hooks shall be regulated on the AGW. Default Value: 0. Defined In: Termination State. Characteristics: read/write. Property Name: Off -Hook Notification. PropertyID: offHookNot (0x0002). Description: This property determin
