1、JTU-T RECMN+Q=70L 93 D 4862593 0584943 98b 9 INTERNATIONAL TELECOMMUNICATION UNION ITU-T TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU Q.701 (03/93) SPECIFICATIONS OF SIGNALLING SYSTEM No. 7 FUNCTIONAL DESCRIPTION OF THE MESSAGE TRANSFER PART (MTP) OF SIGNALLING SYSTEM No. 7 ITU-T Recommendation Q
2、.701 (Previously “CCITT Recommendation”) COPYRIGHT International Telecommunications Union/ITU TelecommunicationsLicensed by Information Handling ServicesITU-T RECMN*Q.701 93 4862591 O584944 812 FOREWORD The ITU Telecommunication Standardization Sector (ITU-T) is a permanent organ of the Internationa
3、l Telecom- munication Union. The ITU-T is responsible for studying technical, operating and tariff questions and issuing Recommendations on them with a view to standardizing telecommunications on a worldwide basis. The World Telecommunication Standardization Conference (WTSC), which meets every four
4、 years, established the topics for study by the ITU-T Study Groups which, in their turn, produce Recommendations on these topics. ITU-T Recommendation 4.701 was revised by the ITU-T Study Group XI (1988-1993) and was approved by the WTSC (Helsinki, March 1-12, 1993). NOTES 1 As a consequence of a re
5、form process within the International Telecommunication Union (ITU), the CCITT ceased to exist as of 28 February 1993. In its place, the ITU Telecommunication Standardization Sector (ITU-T) was created as of 1 March 1993. Similarly, in this reform process, the CCIR and the IFRB have been replaced by
6、 the Radiocommunication Sector. In order not to delay publication of this Recommendation, no change has been made in the text to references containing the acronyms “CCITT, CCIR or IFRB” or their associated entities such as Plenary Assembly, Secretariat, etc. Future editions of this Recommendation wi
7、ll contain the proper terminology related to the new ITU structure. 2 telecommunication administration and a recognized operating agency. In this Recommendation, the expression “Administration” is used for conciseness to indicate both a O ITU 1994 All rights reserved. No part of this publication may
8、 be reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from the ITU. COPYRIGHT International Telecommunications Union/ITU TelecommunicationsLicensed by Information Handling ServicesCONTENTS 1 Introduction
9、1.1 General 1.2 Objectives . 1.3 General characteristics 2 3 Signalling system structure 2.1 Basic functional division 2.2 Functional levels . 2.3 Signalling message . 2.4 Functional interface Message Transfer Part and the signalling network 3.1 General 3.3 3.4 Testing and maintenance functions . 3.
10、5 Use of the signalling network . Signalling network management functions . 4 Message transfer capability 4.1 General 4.2 User location in system structure 4.3 Message content 4.4 User accessibility 4.5 Transport service performance . Differences from the Blue Book 5.1 Processor outage . 5.2 Availab
11、ility of adjacent signalling point . 5.3 Handling of level 3 messages . 5.5 Load balancing during changeback 5.7 Changeback 5.8 MTP restart . 5.9 Signalling traffic flow control . 5.10 User part availability control 5.1 1 Signalling route management . Compatibility in the Message Transfer Part . 6.1
12、 Unreasonable information 6.2 Treatment of spare fields 6.3 Lack of acknowledgement Interworking of yellow. red and blue MTP implementations 7.1 Yellow Book to Red Book interworking 7.2 Red Book to Blue Book interworking 7.3 Yellow Book to Blue Book interworking . 7.4 Blue Book to the present versio
13、n interworking 7.5 Red Book to the present version interworking . 5 5.4 Transferred controlled messages 5.6 Time-controlled changeover procedure 6 7 Recommendation 4.701 (03/93) Page 1 1 1 1 3 3 4 6 6 7 7 9 10 11 12 12 12 12 13 13 13 14 14 14 14 14 14 14 14 14 15 15 15 15 15 15 16 16 16 18 19 19 1 C
14、OPYRIGHT International Telecommunications Union/ITU TelecommunicationsLicensed by Information Handling ServicesITU-T RECMN*Q.701 93 = q8b2591 05849Lib b95 Page Primitives and parameters of the Message Transfer Part . 19 8.1 Transfer . 19 8.2 Pause . 19 8.3 Resume . 19 8.4 Status 20 8.5 Res tart . 20
15、 8 ii Recommendation Q.701 (0393) COPYRIGHT International Telecommunications Union/ITU TelecommunicationsLicensed by Information Handling ServicesITU-T RECNN*Q=703 93 4862593 0584947 523 Recommendation Q.701 FUNCTIONAL DESCRIPTION OF THE MESSAGE TRANSFER PART (MTP) OF SIGNALLING SYSTEM No. 7 (Geneva
16、, 1980; modified at Helsinki, 1993) 1 Introduction 1.1 General The Message Transfer Part (MTP) provides the functions that enable User Part significant information passed to the MTP to be transferred across the Signalling System No. 7 network to the required destination. In addition, functions are i
17、ncluded in the MTP to enable network and system failures that would affect the transfer of signalling information to be overcome. This constitutes a sequenced connectionless service for the MTP user. The Message Transfer Part together with one of its “users”, the Signalling Connection Control Part (
18、SCCP), described in Recommendations Q.711-4.716, forms the Network Service Part (NSP). The Network Service Part meets the requirement for Layer 3 services as defined in the OS1 Reference Model (Recommendation X.200). The relationship of the MTP with this model and to other parts of SS No. 7 is descr
19、ibed in Recommendation 4.700. 1.2 Objectives The overall objectives of the Message Transfer Part are to provide the means for a) the reliable transport and delivery of “User Part” signalling information across the SS No. 7 network; b) the ability to react to system and network failures that will aff
20、ect a), and take the necessary action to ensure that a) is achieved. The “Users” of MTP are the SCCP, Telephone User Part (TUP) (Recommendation 4.721-4.725) Data User Part (DUP) (Recommendation 4.741) and ISDN User Part (ISUP) (Recommendation Q.761-Q.766). The MTP Testing User Part is for further st
21、udy. 1.3 General characteristics 1.3.1 Method of description - functions provided by each level within the MTP; - services provided by the MTP; - - interaction with the signalling network; interaction with the MTP “User”; - the message transfer capability of the MTP. The functions of each level of t
22、he MTP are performed by means of the level protocol between two systems which provides a “level service” to the upper levels (Le. level 1 Signalling Data Link, level 2 Signalling Link and level 3 Signalling network) as described in Recommendations Q.702,Q.703 and 4.704 respectively. The service inte
23、rface to the level 4 “Usei of MTP is described by means of primitives and parameters. Recommendation 4.701 (03/93) 1 COPYRIGHT International Telecommunications Union/ITU TelecommunicationsLicensed by Information Handling ServicesITU-T RECMN+Q.701 93 m 4862591 0584948 468 M X 13.2 Primitives Primitiv
24、es consist of commands and their respective responses associated with the services requested of the SCCP and of the MTP (see Figure 1). The general syntax of a primitive is shown below: Generic name Specific name Parameter - - - - “Y designates the functional block providing the service (“MTP” for M
25、TP). “Generic name” describes the action that should be performed by the addressed layer. “Specific name” indicates the direction of the primitive flow. “Parameters” are the elements of information which are to be transmitted between layers. Four specific names exist in general: - request; - indicat
26、ion; - response? - confirmation). Primitives and parameters of the Messsage Transfer Part service are listed and described in 8. Service -77- FIGURE VQ.701 1.3.3 Peer- level 2 control by use of Link Status Signal Units (LSSUs); testing and maintenance of signalling links by means of the signalling l
27、ink test message carried in an MSU. Not all generic names contain all four specific names (see Figure 2). 2 Recommendation Q.701 (03/93) COPYRIGHT International Telecommunications Union/ITU TelecommunicationsLicensed by Information Handling Services ITU-T RECMN*d.701 93 48b2591 0584949 3T4 - Re T113
28、1030-91!d02 COmmOn Link Signalling Link common - 2- transfer - control - data - control - transfer functions functions link functions functions - - FIGURE 2/Q.701 Specific name of primitives and peer-to-peer communications 1.3.4 Contents of Recommendations Q.701 to Q.707-Series relating to the MTP R
29、ecommendation 4.701 contains a functional description and overview of the Message Transfer Part of SS No. 7. Recommendation 4.702 details the requirements of a signalling data link to support SS No. 7. Recommendation 4.703 describes the signalling link functions. Recommendation 4.704 describes signa
30、lling network functions and messages. Recommendation 4.706 defines and specifies values for MTP performance parameters. Recommendation 4.707 describes the testing and maintenance functions applicable to the MTP. 2 Signalling system structure 2.1 Basic functional division The fundamental principle of
31、 the signalling system structure is the division of functions into a common Message Transfer Part (MTP) on one hand and separate User Parts for different users on the other. This is illustrated in Figure 3. “I I User message processing I User Part FIGURE 314.701 Functional diagram for the common cha
32、nnel signalling system message procescing user Parts T1156140%3/403 Recommendation Q.701 (03/93) 3 COPYRIGHT International Telecommunications Union/ITU TelecommunicationsLicensed by Information Handling ServicesITU-T RECHN*Q*701 73 m 4862571 0584750 016 m I The overall function of the Message Transf
33、er Part is to serve as a transport system providing reliable transfer of signalling messages between the locations of communicating user functions. r- A The term user in this context refers to any functional entity that utilizes the transport capability provided by the Message Transfer Part. A User
34、Part comprises those functions of, or related to, a particular type of user that are part of the common channel signalling system, typically because those functions need to be specified in a signalling context. D -. a: TUP 62 octets. iii) If the message originator is a local MTP User, an MTP-PAUSE p
35、rimitive will be returned by the MTP in response to an overlength message (see 8). Should the originator be at a remote SP, a TFA coded to indicate that only 62 octet SIF messages can be transferred will be returned by the MTP in response to an overlength message (see WQ.704). iv) On receipt of WA (
36、62 octets only), an SP should attempt to use an alternative 272 octet route to the affected destination. If this is not possible, then MTP-PAUSE should be sent from the MTP to the local users. v) When a 272 octet route capability is re-established at a STP, it should inform any local users by means
37、of MTP-RESUME and remote SPs by means of a TFA (272 octets allowed). The remote SP should inform its local users with an MTP-RESUME primitive. In national networks using a SiF compatibility mechanism, the two spare bits in the TFA (see 15.8.2/Q.704) and in the RST (see WQ.704) may be coded as a SIF
38、compatibility indicator as follows: bit BA O0 Allow 62 octet SIFs/Prohibit 272, X and Y octet SIFs o1 Allow 62 and 272 octet SIFs/Prohibit X and Y octet SIFs 10 Allow 62,272 and X octet SIFs Prohibit Y octet SIFs 11 Allow 62,272, X and Y octet SIFs NOTE - 272 X Y octets, the values of X and Y are fo
39、r further study. 7.2.7 Processor outage Note that an interworking problem exists in the cases where a Red Book node is performing management inhibiting or management blocking and, according to the Blue Book specification, the remote side performs time-controlled changeover in order to divert traffic
40、 from the link. This is because the received changeover order is not acknowledged, resulting in the link being taken out of service. Thus, a changeover acknowledgement must be returned to the Red Book side. If the changeover order is received during time T1 (see 16.WQ.704) it is advantageous to swit
41、ch to the normal changeover procedure including retrieval, so that unnecessary message loss or sending of old messages can be avoided in a simple way. The ability to perform this switch is considered to be implementation dependent. If a changeover order is received after timer T1 has expired time-co
42、ntrolled changeover is completed (if not yet done) and an emergency changeover acknowledgement is sent to the remote end. 7.3 Yellow Book to Blue Book interworking The changes between Yellow Book and Blue Book have taken place in two stages: Yellow to Red and Red to Blue. Therefore, to achieve inter
43、working between Yellow and Blue Books implementations, the actions specified in 7.1 and 7.2 should be applied. In 7.1, Red Book SP/STP should be read as Blue Book SP/STP and in 7.2, Red Book SP/STP should be read as Yellow Book SP/STP. There is one change from the Red Book in the Blue Book that will
44、 have an additional impact on interworking with the Yellow Book, and that is the deletion of the blocking procedure. This means that while a Yellow Book implementation can block a signalling link, a Blue Book node can neither inhibit nor block the link in the opposite direction. 18 Recommendation Q.
45、701 (03/93) COPYRIGHT International Telecommunications Union/ITU TelecommunicationsLicensed by Information Handling ServicesITU-T RECMN*Qm70L 93 m 48b2591 0584765 547 m 7.4 7.4.1 MTP restart Due to the improvements concerning the MTP restart procedure, as described in clause 5. interworking problems
46、 between the Blue Book and the present version MTPs may arise in the form of message loss and loss of bi-directionality during the restart procedure. If these problems cannot be ignored, the present version restart procedure should be introduced within the Blue Book MTP. Blue Book to the present ver
47、sion interworking 7.4.2 Processor outage In the case where a Blue Book level 3 has to interwork with the present version level 2, a problem exists because no message is sent by level 3 to flush the buffers and synchronize the sequence numbers. The solution of this problem is implementation dependent
48、, but the problem might be solved, for example, if the level 3 were changed to take the link out of service when processor outage occurs. 7.5 The changes between the Red Book and the present version have taken place in two stages: Red Book to Blue Book and Blue Book to the present version. Therefore
49、, to achieve interworking between Red Book and the present version implementations, the actions specified in 7.2 and 7.4 should be applied. In addition, the following information might be useful to achieve interworking. 7.5.1 MTPrestart As a consequence of the interworking between the Red Book and the present version MTPs, problems arise in the form of message loss and loss of bi-directionality during the restart procedure. If these problems cannot be ignored, the present version MTP restart procedure should be introduced within the Red Book node. In the case of Red Book SEPS, as
