ETSI ETS 300 008 ed.1 (1991-12)

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.DIntegrated Services Digital Network (ISDN); Signalling System No.7; Message Transfer Part (MTP) to support international interconnection33.080Digitalno omrežje z integriranimi storitvami (ISDN)Integrated Services Digital Network (ISDN)ICS:Ta slovenski standard je istoveten z:ETS 300 008 E1PSIST ETS 300 008:1996en01-november-1996PSIST ETS 300 008:1996SLOVENSKI

EUROPEANETS 300 008TELECOMMUNICATIONDecember 1991STANDARDSource: ETSI TC-SPSReference: T/S 43-01ICS:33.080Key words:ISDN, SS7Integrated Services Digital Network (ISDN);CCITT Signalling System No. 7Message Transfer Part (MTP) to support internationalinterconnectionETSIEuropean 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: secretariat@etsi.frTel.: +33 92 94 42 00 - Fax: +33 93 65 47 16Copyright 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 1991. All rights reserved.PSIST ETS 300 008:1996New presentation - see History box

Page 2ETS 300 008: December 1991Whilst 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.PSIST ETS 300 008:1996

Page 3ETS 300 008: December 1991ContentsForeword.......................................................................................................................................................51Scope..................................................................................................................................................72Normative references..........................................................................................................................73Symbols and abbreviations.................................................................................................................74Exceptions to CCITT Recommendations Q.701 to Q.708..................................................................84.1National options...................................................................................................................84.2Signalling data links.............................................................................................................84.3Timer values........................................................................................................................84.3.1CCITT Recommendation Q.703......................................................................84.3.2CCITT Recommendation Q.704......................................................................84.4Signalling link management.................................................................................................94.5Procedures to prevent unauthorised use of a signalling transfer point................................94.6Network Indicator.................................................................................................................94.7Signalling Point (SP) restart.................................................................................................94.8User flow control................................................................................................................145Modifications to texts taken from the CCITT Blue Book (1988)........................................................155.1Interworking between SPs to the CEPT Recommendation T/S 43-01 and this ETS.........155.2Changes to CCITT Recommendation Q.701, § 7.2.4........................................................155.3Changes to CCITT Recommendation Q.701, § 7.2.7........................................................155.4Changes to CCITT Recommendation Q.701, § 8.5...........................................................165.5Changes to CCITT Recommendation Q.703, § 8..............................................................165.6Change to CCITT Recommendation Q.704, § 3.6.2.2......................................................175.7Change to CCITT Recommendation Q.704, § 5.6.2.........................................................175.8Change to CCITT Recommendation Q.704, § 6.3............................................................185.9Change to CCITT Recommendation Q.704, § 11.2.3.1....................................................186Specific requirements........................................................................................................................186.1Signalling link loading........................................................................................................186.1.1Basic definition..............................................................................................186.1.2Maximum signalling link load during normal operation.................................196.1.3Minimum signalling link load handling capability...........................................196.1.4Message length influence..............................................................................196.1.5Graphic representation..................................................................................19History..........................................................................................................................................................21PSIST ETS 300 008:1996

Page 5ETS 300 008: December 1991ForewordThis European Telecommunication Standard (ETS) has been produced by the Signalling Protocols andSwitching (SPS) Technical Committee of the European Telecommunications Standards Institute (ETSI),as working document T/S 43-01), and was adopted having passed through the ETSI standards approvalprocedure.This ETS is based on CCITT Recommendations Q.701 to Q.708 as given in the CCITT Blue Book, 1988.The requirements of these CCITT Recommendations shall apply unless modified by the statementsprovided in Clauses 4 and 5 of this ETS and, in addition, shall include the specific requirements containedin Clause 6.The CEPT Recommendation for the Message Transfer Part (MTP), see CEPT T/S 43-01, April 1987, maycontinue to be used for the early introduction of services e.g. GSM, GAP Phase 2 and the ISDN MOU.Where CEPT Recommendation T/S 43-01 does not already conform with the CCITT Blue Book MTP, theappropriate sections of CCITT Recommendation Q.701 together with the additions contained in this ETSshall resolve any interworking problems between this ETS and CEPT Recommendation T/S 43-01.CCITT Recommendations Q.709 [9] and Q.791 apply as appropriate, unmodified, since they have noimpact on interworking and are considered for guidance only.PSIST ETS 300 008:1996

Page 7ETS 300 008: December 19911ScopeThe scope of this ETS is the further development of the CCITT Signalling System No. 7 protocols for boththe Integrated Services Digital Network (ISDN) and Public Switched Telephone Network (PSTN) followingthe publication of CCITT Recommendations Q.701 to Q.708 [1] to [8].This ETS is applicable to the international network and is not meant to restrict national networks.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 Q.701 (1988): "Functional description of the messagetransfer part (MTP) of Signalling System No.7".[2]CCITT Recommendation Q.702 (1988): "Signalling data link".[3]CCITT Recommendation Q.703 (1988): "Signalling link".[4]CCITT Recommendation Q.704 (1988): "Signalling network functions andmessages".[5]CCITT Recommendation Q.705 (1988): "Signalling network structure".[6]CCITT Recommendation Q.706 (1988): "Message transfer part signallingperformance".[7]CCITT Recommendation Q.707 (1988): "Testing and maintenance".[8]CCITT Recommendation Q.708 (1988): "Numbering of international signallingpoint codes".[9]CCITT Recommendation Q.709 (1988): "Hypothetical signalling referenceconnection".[10]CCITT Recommendation Q.791 (1988): "Monitoring and measurements forSignalling System No.7 networks".[11]CEPT Recommendation T/S 43-01 (April 1987): "CCITT No.7 Message TransferPart (MTP)".3Symbols and abbreviationsFor the purposes of this ETS, the following abbreviations apply.DPCDestination Point CodeISDNIntegrated Services Digital NetworkLSSULink Status Signal UnitMSUMessage Signal UnitMTPMessage Transfer PartPSTNPublic Switched Telecommunications NetworkPSIST ETS 300 008:1996

Page 8ETS 300 008: December 1991SIFSignalling Information FieldSIOService Information FieldSTPSignalling Transfer PointSPSignalling PointTFPtransfer-prohibited signalTRAtransfer-restart-allowed signalUPUUser Part Unavailable4Exceptions to CCITT Recommendations Q.701 to Q.708The following exceptions to CCITT Recommendations Q.701 to Q.708 [1] to [8], as specified in the BlueBook, 1988, shall apply.4.1National optionsNo national options, or remarks, with regard to national options shall apply to this ETS.4.2Signalling data linksA standard bit rate of 64 kbit/s on signalling data links shall apply.If signalling data links are to be provided over an analogue transmission path, any necessary digital toanalogue or analogue to digital conversion shall be on the multiplexed transmission link after interfacepoint C, as defined in figure 2 of CCITT Recommendation Q.702 [2].4.3Timer valuesThe timer values included in CCITT Recommendations Q.703 [3], Q.704 [4] and Q.707 [7] shall apply,with the following exceptions.4.3.1CCITT Recommendation Q.703These timers shall not apply: T1 (4,8 kbit/s), T2 low, T2 high, T4n (4,8 kbit/s), T4e (4,8 kbit/s), T6 (4,8kbit/s) and T7 (4,8 kbit/s).4.3.2CCITT Recommendation Q.704These timers shall not apply: T7, T11, T15, T16 and T24.Timer values to be modified in CCITT Recommendation Q.704 [4], § 16.8:-T18 Timer within a signalling point whose MTP restarts, for supervising link and linkset activation aswell as the receipt of routing information. The value is implementation and network dependent.Criteria to choose T18 are given in CCITT Recommendation Q.704 [4], § 9.2.-T19 Supervision timer during MTP restart to avoid possible ping-pong of transfer-prohibited signal(TFP) and traffic-restart-allowed signal (TRA) messages: 67 to 69 seconds.-T20 Overall MTP restart timer at the signalling point whose MTP restarts: 59 to 61 seconds.-T21 Overall MTP restart timer at a signalling point adjacent to one whose MTP restarts: 63 to 65seconds.PSIST ETS 300 008:1996

Page 9ETS 300 008: December 1991NOTE:The values of the MTP restart timers (T18 to T21) defined above are for use duringnormal operation. It might be advantageous for the network operator(s) to define analternative value for each timer for use in potential network failures. Such anemergency might be recognised by an abnormally large number of outages, and itwould be at the discretion of the operator(s) to use the emergency set of timer valueswithin the network. Thus, the selection of the appropriate timer set is within theresponsibility of the network administration.4.4Signalling link managementOf the requirements in CCITT Recommendation Q.704 [4], only the basic signalling link managementfunctions of § 12.2 shall apply and § 12.3, § 12.4, § 12.5 and § 12.6 shall not apply.4.5Procedures to prevent unauthorised use of a signalling transfer pointWhile CCITT Recommendation Q.705 [5] is intended as a guidance document only, it should be notedthat the optional procedure for the prevention of unauthorised use of a Signalling Transfer Point (STP) asspecified in CCITT Recommendation Q.705 [5], § 8, shall not be essential.4.6Network IndicatorOnly the value 00 shall be used for the Network Indicator.4.7Signalling Point (SP) restartCCITT Recommendation Q.704 [4], § 9, shall be replaced by the following.9MTP restart9.1GeneralWhen a signalling point is isolated from the network for some time, it cannot be sure that its routingdata are still valid (note that circumstances might cause the management entity to isolate the node,i.e. make all links unavailable, in order to facilitate recovery from a partial isolation). Thus, problemscould be present when the sending of User traffic is resumed, due to wrong routing data as well asdue to many parallel activities (e.g. link activation, changebacks, etc.) which have to be performedwithin the node whose MTP is restarting.The objective of the MTP restart procedure is to protect both the node whose MTP is restarting, andthe network. This is done by giving the restarting MTP time to activate sufficient links, and toexchange enough routing data with the network, before User traffic is restarted. Note that in thiscontext "sufficient" and "enough" mean that potential remaining problems should not cause thenode to fail again.A central part of the restart procedure is the exchange of network status information between therestarting MTP and the adjacent nodes. In order for the procedure to make sense, the networkstatus should not change significantly during this information exchange. As a consequence there isan overall restart time defined for the node whose MTP is restarting as well as for the adjacentnodes. During this time, all activities within the node whose MTP is restarting as well as theadjacent nodes should be completed. This requires that the time available is used in an efficientway.As a basis of the restart procedure it is assumed that most of the signalling points within thenetwork are accessible. Thus, at the beginning of the restart procedure, all concerned routes areconsidered to be allowed, and the update of the network status is performed by the exchange oftransfer-prohibited signal (TFP) messages.PSIST ETS 300 008:1996

Page 10ETS 300 008: December 1991The MTP restart procedure uses the traffic-restart-allowed signal (TRA) message which contains:-the label, indicating the originating signalling point and the adjacent destination signallingpoint;-the traffic restart allowed signal.The format and coding of this message appear in CCITT Recommendation Q.704, § 15.When an adjacent node has finished sending all relevant TFP messages to the node with therestarting MTP, it finally sends a TRA message which indicates that all relevant routing informationhas been transferred. Thus, at the node with the restarting MTP, the number of received TRAmessages is an indication of the completeness of the routing data.When the restarting MTP has completed all actions or when the overall restart time is over, it sendsTRA messages directly to all of its adjacent nodes accessible via a direct linkset. These messagesindicate that the restart procedure is terminated and User traffic should be started.9.2Actions in a signalling point whose MTP is restarting9.2.1A signalling point starts the MTP restart procedure when its first link is in service at level 2. Therestarting MTP:-if it has the transfer function, starts a timer T18;-starts an overall restart timer T20; and-continues activating or unblocking all of its signalling links by means of the basic signalling linkmanagement procedures (see CCITT Recommendation Q.704, § 12.2).NOTE:In order to use the overall restart time in an efficient way, it is preferable to make alllinksets available at nearly the same time, by activating first one link per linkset, and byapplying emergency alignment for at least the first link in each linkset. Because of thismeasure, the routing data update can be started for all routes at the very beginning ofthe restart procedure.9.2.2If the signalling point's restarting MTP has the transfer function, the MTP restart procedure consistsof two phases. Within the first phase, supervised by timer T18, links are activated and the routingtables within the restarting MTP are updated according to the transfer prohibited and transferallowed messages (see CCITT Recommendation Q.704, § 15) received from the adjacent nodes.In addition, the restarting MTP takes into account any traffic restart allowed messages receivedfrom adjacent nodes. Timer T18 is implementation and network dependent, and is stopped when:(1)sufficient links and linksets are available to carry the expected signalling traffic; and(2)enough TRA messages (and therefore routing data) have been received to give a high level ofconfidence in the MTP routing tables.NOTE:In normal circumstances the restarting MTP should wait for TRA messages from alladjacent nodes. There are, however, other situations where this might not be useful,e.g. for a long-term equipment failure.When T18 is stopped or expires, the second phase begins, which includes as a major part abroadcast of non-preventive transfer prohibited messages (i.e. those TFPs according to CCITTRecommendation Q.704, § 13.2.2, v), taking into account signalling linksets which are not availableand any TFP and TFA messages received during phase 1.PSIST ETS 300 008:1996

Page 11ETS 300 008: December 1991Note that timer T18 is determined such that during phase 2 the broadcast of TFP messages maybe completed in normal situations. TRA messages received during phase 2 should be ignored. Ifduring phase 2 a destination has been declared to be inaccessible by sending of a TFP message,and afterwards, but still within phase 2, this destination becomes accessible to the restarting MTPby reception of a TFA message or the availability of a corresponding link, this new accessibility is alate event and should be treated outside the restart procedure.The handling of the new accessibility of the said destination before the sending of a TFP referring tothat destination is an implementation dependent matter.When all TFP messages have been sent, the overall restart timer T20 is stopped and phase 2 isfinished.Note that preventive TFP messages (i.e. those according to CCITT Recommendation Q.704,§ 13.2.2, i), except possibly those for highest priority routes, must have been sent before normalUser traffic is carried. This might be done during or after phase 2.9.2.3If the restarting MTP has no transfer function, phase 1 (see CCITT Recommendation Q.704,§ 9.2.2) but not phase 2 is present. In this case, the whole restart time is available for phase 1. Theoverall restart timer T20 is stopped when:(1)sufficient links and linksets are available to carry the expected signalling traffic; and(2)enough TRA messages (and therefore routing data) have been received to give a high levelof confidence in the MTP routing tables.9.2.4When T20 is stopped or expires, the restarting MTP of the signalling point or signalling transferpoint sends traffic restart allowed messages to all adjacent signalling points via correspondingavailable direct linksets, and an indication of the end of MTP restart is sent to all local MTP Usersshowing each signalling point's accessibility or inaccessibility. The means of doing the latter isimplementation dependent.In addition, timer T19 is started (see CCITT Recommendation Q.704, § 9.5.2) for all signallingpoints to which a TRA message has just been sent. Normal operation is then resumed.When T20 expires the transmission of TFP messages is stopped. However, preventive TFPmessages (i.e. those according to CCITT Recommendation Q.704, § 13.2.2, i), except possiblythose for highest priority routes, must have been sent before MTP User traffic is restarted.9.3Actions in a signalling point X, adjacent to a signalling point Y whose MTP restarts.9.3.1A signalling point X considers that the MTP of an inaccessible adjacent signalling point Y isrestarting when:-the first link in a direct linkset is in the "in service" state at level 2; or-another route becomes available due either to reception of a corresponding TFA or TRAmessage, or by the corresponding linkset becoming available (see CCITT RecommendationQ.704, § 3.6.2.2).PSIST ETS 300 008:1996

Page 12ETS 300 008: December 19919.3.2When the first link in a direct linkset towards signalling point Y, whose MTP is restarting, is in the "inservice" state at level 2, signalling point X starts a timer T21 and takes account of any TFP and TFAmessages received from signalling point Y. In addition X takes the following action:-if X has the transfer function, when the direct linkset is available at level 3, X sends anynecessary TFP messages to Y; then-X sends a traffic restart allowed message to signalling point Y.If a signalling point, previously declared to be inaccessible, becomes available again before T21 isstopped or expires, a corresponding TFA message is sent to the signalling point Y whose MTP isrestarting.If a signalling point becomes prohibited to signalling point X after a TRA message has been sent byX to Y, X sends a corresponding TFP message to Y.When a traffic restart allowed message has been received by X from signalling point Y, and a TRAmessage has been sent by X to Y, X stops timer T21. Note that preventive TFP messagesaccording to CCITT Recommendation Q.704, § 13.2.2, i) must be sent before MTP User traffic isrestarted.NOTE:This includes the case where the MTP of Y is restarting as well as the case that both Xand Y start the adjacent signalling point MTP restart procedure at the new availabilityof the interconnecting direct linkset. In the latter case, one side will receive a TRAmessage from the other while still sending TFP messages, so that it has not yet sentits TRA message. The transmission of routing information should be completed beforethis TRA message is sent to the adjacent node and timer T21 stopped.When T21 is stopped or expires, signalling point X sends an MTP-RESUME primitive concerning Y,and all signalling points made available via Y, to all local MTP Users. If X has the transfer function,it broadcasts to adjacent available signalling points transfer allowed messages concerning Y and allsignalling points made accessible via Y. Note that preventive TFPs according to CCITTRecommendation Q.704, § 13.2.2, i) must be sent before MTP User traffic is restarted.In the abnormal case where transfer prohibited messages are still being sent to Y when T21 expires(and hence no TRA message has yet been sent to Y), such routing data transmission is stoppedand no TRA message is sent to Y. Note that preventive TFPs according to CCITTRecommendation Q.704, § 13.2.2, i) must still be sent during the changeback procedure.9.3.3When signalling point Y becomes accessible by means other than via a direct linkset between Xand Y, X sends an MTP-RESUME primitive concerning Y to all local MTP Users. In addition, ifsignalling point X has the transfer function, X sends to Y any required transfer prohibited messageson the available route. X then broadcasts TFA messages (see CCITT Recommendation Q.704, §13) concerning Y.NOTE:X should not in this case alter any routing data other than that for Y.9.4Short term isolations9.4.1In the case where a signalling point is isolated due to a short term processor outage (lasting lessthan T1 {see CCITT Recommendation Q.704, § 16.8}) occurring on some or all of its links at nearlythe same time, the restart procedure should not be started. If an isolation lasts longer than T1, therestart procedure must be performed.PSIST ETS 300 008:1996

Page 13ETS 300 008: December 19919.4.2When a destination Y becomes inaccessible, and routing control finds an inhibited link within therouteset to Y, a signalling routing control initiated uninhibiting action is performed (see CCITTRecommendation Q.704, § 10.3). If at least one inhibited link is in the level 2 "in service" state, anduninhibiting is successful, the isolation will be of short-term and no restart procedure should beperformed on either side of the link.9.5TRA messages and timer T199.5.1If a signalling point X receives an unexpected TRA message from an adjacent node Y and noassociated T19 timer is running, X sends to Y any necessary TFP messages if X has the transferfunction, and a TRA message to Y. In addition, X starts a timer T19 associated with Y.9.5.2If a signalling point receives a TRA message from an adjacent node and an associated timer T19 isrunning, this TRA is discarded and no further action is necessary.9.6General rules9.6.1When the MTP of a signalling point restarts, it considers at the beginning of the MTP restartprocedure all signalling routes to be allowed.9.6.2After the MTP of an adjacent node X has restarted, and if T21 has been started (see CCITTRecommendation Q.704, § 9.3.2) all routes using X are considered to be available unlesscorresponding TFP messages have been received whilst T21 was running.9.6.3A signalling route set test message received in a restarting MTP is ignored during the MTP restartprocedure. Signalling route set test messages received in a signalling point adjacent to signallingpoint Y whose MTP is restarting before T21 expires are handled, but the replies assume that allsignalling routes using Y are prohibited.9.6.4Late events, i.e. link restorations or reception of TFA messages, occurring in phase 2 at a nodewhose MTP is restarting after the node has sent out TFPs referring to the concerned signallingpoints, are treated outside the restart procedure as normal events.Handling of late events in phase 2 before sending out TFPs referring to the concerned signallingpoints is an implementation dependent matter. In addition, it is an implementation dependent matterwhether the reception of TFPs or linkset failures during phase 2 are handled within or after thetermination of the restart procedure.9.6.5When an adjacent signalling point Y becomes accessible on receipt of a TFA or TRA message (seeCCITT Recommendation Q.704, § 3.6.2) the concerned signalling point performs controlledrerouting towards Y.9.6.6All messages to another destination received at a signalling point whose MTP is restarting arediscarded.All messages received during the restart procedure concerning a local MTP User (service indicatornot equal to 0000 and not equal to 0001) are discarded. All messages received with serviceindicator equal to 0000 in a restarting MTP for the signalling point itself are treated as described inthe MTP restart procedure. Those messages not described elsewhere in the procedure arediscarded and no further action is taken on them (message groups CHM, ECM, FCM, RSM, UFC,MIM and DLM).9.6.7In adjacent signalling points during the restart procedure, messages not part of the restartprocedure but which are destined to or through the signalling point whose MTP is restarting, arediscarded.Messages received with service indicator equal to 0001 are handled normally during the restartprocedure.PSIST ETS 300 008:1996

Page 14ETS 300 008: December 19919.6.8If a gateway node's MTPs are restarting in multiple networks, it may be of advantage to co-ordinatetheir restarting procedures (implementation dependent).4.8User flow controlCCITT Recommendation Q.704 [4], § 11.2.7 shall be replaced by the following:11.2.7User Part availability control11.2.7.1If the MTP is unable to distribute a received message to a local user because that user isunavailable (User Part unavailability is an implementation dependent notion - it can includeunavailability for management reasons, the user might even be unequipped), the MTP sends aUser Part Unavailable (UPU) message to the MTP at the originating signalling point.11.2.7.2When the originating signalling point's MTP receives a UPU message, it:a)informs the management process;b)sends an indication (MTP-STATUS with parameters identity of the signalling pointcontaining the unavailable User Part, and cause "Remote User Unavailable"), to thelocal user designated in the message, if it is available.NOTEThe MTP does not maintain status information regarding the availability of the remoteUser Part.11.2.7.3The user should then take appropriate action in order to stop generation of normal signallinginformation for the unavailable User Part.11.2.7.4It is the responsibility of the User Part to determine when the remote User Part is again available(User Part availability is an implementation dependent notion). This might be done, for example,by the user testing periodically, or by using the reception of a message from the remote user asan implicit indication of availability, or both.11.2.7.5The UPU message contains:-the label, indicating the destination and originating points;-the UPU signal;-the identity of the unavailable User Part.The format and coding of this message appear in § 15.11.2.7.6When the MTP is again able to distribute received messages to a previously unavailable localUser Part (local User Part availability is an implementation dependent notion), the MTP deliversthe received messages to that user.11.2.7.7If a UPU message is received by the MTP referring to a remote User Part whose local peer isunequipped, the MTP informs the management process(1) and discards the UPU message.11.2.8User Part congestionThere are no specific User Part congestion control procedures defined in the MTP.

(1)Whether or not the management process is informed is implementation dependent.PSIST ETS 300 008:1996

Page 15ETS 300 008: December 19915Modifications to texts taken from the CCITT Blue Book (1988)5.1Interworking between SPs to the CEPT Recommendation T/S 43-01 and this ETSThe text in § 7.2.1 of CCITT