1、INTERNATIONAL TELECOMMUNICATION UNION)45G134 1 TELECOMMUNICATIONSTANDARDIZATION SECTOROF ITU30%#)&)#!4)/.3G0G0/&G0G03).!,).G0G03934%-G0G0.O G0 3)-0,)&)%$G0G0-40G0G06%23)/.G0G0&/2G0G03-!,3934%-3)45G134G0G0RecommendationG0G01 (Extract from the “LUEG0“OOK)NOTES1 ITU-T Recommendation Q.710 was published
2、 in Fascicle VI.7 of the Blue Book. This file is an extract fromthe Blue Book. While the presentation and layout of the text might be slightly different from the Blue Book version, thecontents of the file are identical to the Blue Book version and copyright conditions remain unchanged (see below).2
3、In this Recommendation, the expression “Administration” is used for conciseness to indicate both atelecommunication administration and a recognized operating agency. ITU 1988, 1993All rights reserved. No part of this publication may be reproduced or utilized in any form or by any means, electronic o
4、rmechanical, including photocopying and microfilm, without permission in writing from the ITU.Fascicle VI.7 - Rec. Q.710 1Recommendation Q.710Fascicle VI.7 - Rec. Q.710SIMPLIFIED MTP VERSION FOR SMALL SYSTEMS1 Field of application1.1 This Recommendation is applicable for systems using a simplified M
5、TP version to interface to the publicnetwork(s).1.2 The MTP functions specified in 3 of this Recommendation may be applied in general for small systems, e.g.,PABXs, remote concentrators, etc., interfacing with the message transfer part described in Recommendations Q.702,Q.703, Q.704 and Q.707.1.3 Th
6、e Recommendation applies only for digital access arrangements.1.3.1 In case one channel carries signalling information for more than one multiplex system, at least one additionalchannel should be pre-assigned as a stand-by signalling link in a multiplex system other than that which contains theactiv
7、e channel. This allows the changeover and changeback procedures specified in 3.4.4 and 3.4.5 to be performed.1.3.2 The stand-by channel(s) should not be used as B-channel(s).1.4 Only the associated mode of signalling is applicable.1.5 A variety of information types may be supported by the signalling
8、 system, e.g., relating to circuit switched callcontrol and packet communication.2 Functional contentThe functional requirements are as follows:2.1 The network call control functions are as specified in Recommendation Q.930 (I.451).Note - Different network layer protocols (circuit switching and pack
9、et switching) may be supported by usingthe protocol discriminator included in Recommendation Q.930. As an alternative, different network layer entities mayaccess the interface functions directly. In that case, the interface functions will use separate service indicator codes todiscriminate the appli
10、cable network layer entity. This will be similar to the use of SAPI specified in RecommendationQ.920. Which principle to be applied is determined by the Administration/RPOA.2.2 The minimum set of Message Transfer Part functions are specified in Recommendations Q.702, Q.703, Q.704and Q.707, with the
11、qualifications specified in 3 of this Recommendation.2.3 The additional interface functions required for the proper operation of the D-channel call control functions incombination with the message transfer part functions, are specified in 4 of this Recommendation (see Figure 1/Q.710).2 Fascicle VI.7
12、 - Rec. Q.7103 Message Transfer Part (MTP) functions3.1 GeneralThe MTP functions as specified in Recommendations Q.702, Q.703, Q.704 and Q.707 are applicable. However,the following exceptions and modifications to those Recommendations may be applied for the PABX system, see 3.2-3.4.In order to preve
13、nt fraudulent use of the signalling network, it has to be ensured that no signalling messagesgenerated by a PABX can be routed further than the public exchange to which the PABX has access. The manner inwhich this is made may be dependent on national circumstances and system implementations. An exam
14、ple of how such afunction could be implemented is given in 3.5.3.2 Level 1 (Recommendation Q.702)Only digital signalling data links are relevant. Recommendation Q.702, 6, is not applicable.3.3 Level 2 (Recommendation Q.703)3.3.1 Initial alignment procedure (Recommendation Q.703, 7)In the initial ali
15、gnment procedure specified in Recommendation Q.703, 7, only the emergency proving isapplicable. Thus, in states “aligned“ and “proving“ of the initial alignment procedure status indication “N“ is not sent.3.3.2 Processor outage (Recommendation Q.703, 8)The processor outage function specified in Reco
16、mmendation Q.703, 8, is not applicable.When the level 2 function receives an indication that a processor outage situation exists at the remote and(through the reception of status signal units indicating processor outage), it transmits status signal units indicating “outof service“.Fascicle VI.7 - Re
17、c. Q.710 33.3.3 Flow control (Recommendation Q.703, 9)The sending of the link status indication “B“ from the PABX is not applicable.When the level 2 function of the PABX receives the link status indication “B“, no action is taken by the PABX.3.4 Level 3 (Recommendation Q.704)3.4.1 Routing label (Rec
18、ommendation Q.704, 2.2)The signalling link selection (SLS) field defined in 2.2.4 is always coded 0000.3.4.2 Message routing function (Recommendation Q.704, 2.3)The load sharing function between link sets and within a link set defined in 2.3.2 is not applicable.3.4.3 Message discrimination (Recommen
19、dation Q.704, 2.4)The discrimination function defined in 2.4.1 is not applicable.3.4.4 Changeover (Recommendation Q.704, 5)Changeover between link sets is not applicable.Initiation of changeover at the reception of a changeover order from the remote end of a link is not applicable(c.f. Recommendatio
20、n Q.704, 3.2.2).The buffer updating procedure defined in 5.4 is not applicable.At reception of a changeover order (or emergency changeover order) an emergency changeoveracknowledgement is sent in response.The message retrieval procedure defined in 5.5 is not applicable.Diversion of traffic is perfor
21、med at expiry of a time-out T1 (c.f. Recommendation Q.704, 16.8) is startedwhen the changeover is initiated.3.4.5 Changeback (Recommendation Q.704, 6)Changeback between link sets is not applicable.The sequence control procedure defined in 6.3 is not applicable. At reception of a changeback declarati
22、on, achangeback acknowledgement is sent in response.For the purpose of ensuring message sequence integrity, the time controlled diversion procedure specified in 6.4 is used.3.4.6 Forced rerouting (Recommendation Q.704, 7)Forced rerouting is not applicable.3.4.7 Controlled rerouting (Recommendation Q
23、.704, 8)Controlled rerouting is not applicable.3.4.8 Signalling point restart (Recommendation Q.704, 9)Signalling point restart is not applicable.4 Fascicle VI.7 - Rec. Q.7103.4.9 Management inhibiting (Recommendation Q.704, 10)Management inhibiting is not applicable.3.4.10 Signalling traffic flow c
24、ontrol (Recommendation Q.704, 11)Signalling route set congestion (Recommendation Q.704, 11.2.3) is not applicable.MTP User flow control (Recommendation Q.704, 11.2.7) is not applicable.3.4.11 Signalling link management (Recommendation Q.704, 12.2)Only basic link management procedures are applicable.
25、3.4.12 Link set activation (Recommendation Q.704, 12.2.4)Link set normal activation defined in 12.2.4.1 is not applicable.Link set emergency restart is used in all cases.3.4.13 Transfer prohibited (Recommendation Q.704, 13.2)The transfer prohibited function is not applicable. At the reception of a T
26、FP message, no action should be taken.3.4.14 Transfer allowed (Recommendation Q.704, 13.3)The transfer allowed function is not applicable. At the reception of a TFA-message, no action should be taken.3.4.15 Transfer restricted (Recommendation Q.704, 13.4)The transfer restricted function is not appli
27、cable for the PABX. At the reception of the TFR message no actionis taken by the PABX.3.4.16 Signalling-route-set-test (Recommendation Q.704, 13.5)The signalling-route-set-test procedure is not applicable.3.4.17 Transfer controlled (Recommendation Q.704, 13.7, 13.8)The transfer controlled function i
28、s not applicable for the PABX. At the reception of the TFC message, no actionis taken by PABX.3.4.18 Signalling route-set-congestion-test (Recommendation Q.704, 13.9)The signalling route-set-congestion-test function is not applicable for the PABX.At the reception of signalling-route-set-congestion-t
29、est message no action is taken by the PABX.3.4.19 Signalling link test (Recommendation Q.707, 2.2)The ability to respond to a signalling link test message with a signalling link test acknowledge message mustalways be provided by the PABX.3.5 Example of “Screening Function“Note - This paragraph is pr
30、ovided for illustration purposes only.At an exchange (which has the capability of acting as an STP) each message received on a PABX access link isFascicle VI.7 - Rec. Q.710 5passed through a “screening function“ that checks that the DPC of the message is the same as the SP code of theexchange. If th
31、at is the case, the message is sent to the normal MTP message handling functions. Otherwise, the messageis discarded.4 Interface functions4.1 GeneralThe task of the interface functions is to provide the layer-to-layer interfaces according to what is specified inRecommendations Q.920, Q.930 on the on
32、e hand and in Recommendation Q.704 on the other, see the Figure 2/Q.710.This will include some conversion functions which are specified in 4.4.4.2 Interactions with the network layer entity (Q.930)The layer-to-layer interactions between the network layer and the data link layer of the D-channel prot
33、ocol arespecified in Recommendation Q.920, 4. The interactions are specified in the form of primitives. The primitiveapplicable for the primary rate interface structure are:DL-DATA-REQUEST/INDICATIONThe DL-DATA-REQUEST primitive is used to request that a network layer message unit be sent. TheDL-DAT
34、A-INDICATION indicates the arrival of a message unit.6 Fascicle VI.7 - Rec. Q.7104.3 Interactions with the message transfer partThe layer-to-layer interactions between the MTP and the User Parts of Signalling System No. 7 are specified inRecommendations Q.701 and Q.704, Figures 23/Q.704 and 27/Q.704
35、.The following primitives are used:a) MTP-TRANSFER (see Recommendation Q.701, 8.1),b) MTP-PAUSE (see Recommendation Q.701, 8.2),c) MTP-RESUME (see Recommendation Q.701, 8.3).4.4 Conversion functionsThe Table 1/Q.710 shows the association between the D-channel primitives and the Signalling System No.
36、 7interactions.TABLE 1/Q.710D-channel SS No. 7Information transfer DL-DATA MTP-TRANSFERFlow control-MTP-PAUSE (STOP)MTP-RESUME (START)4.4.1 Information transferWhen receiving a DL-DATA-REQUEST primitive from the network layer entity, the interface entity generatesa MTP-TRANSFER Request primitive whi
37、ch contains:- The message unit associated with the primitive.- A label consisting of DPC, OPC and SLS. The label is generated by the interface entity on the basis ofinformation regarding the destination of the message. The SLS is coded 0000.Note - In some implementations where the label is not used
38、for routing purposes, the entire label may becoded “all zeros“.- A service information octet (SIO) is generated by the interface entity in accordance with a predeterminedrule and, as a national option, on the basis of priority information associated with the primitive. The NI iscoded 10 or 11. The S
39、I code is determined by the Administration or RPOA.Note - In the case when the interface functions provide direct access to more than one network layer entity,the SI code will depend on the network layer entity to which the message is associated.When receiving a MTP-TRANSFER Indication from the MTP,
40、 the interface entity sends a DL-DATA-INDICATION primitive to the network layer entity.4.4.2 Flow controlWhen receiving a MTP-PAUSE indication from the MTP, the interface entity will generate a DL-PAUSE-INDICATION primitive to the network layer entity.When receiving a MTP-RESUME indication from the MTP, the interface entity will generate a DL-RESUME-INDICATION primitive to the network layer entity.
