1、CEPT T/S*q3-OL*E 7 232bllL4 0008003 L E I 43-01 Page 1 E Recommendation TIS 43-01 (by correspondence, April 1987) CCITT No. 7 MESSAGE TRANSFER PART mP) Recommendation proposed by Working Group T/WG 11 “Signalling. Protocols and Switching” (SPS) Text of the Recornmendation adopted by the “Telecommimi
2、cntions” Commission: “The European Conference of Postal and Telecommunications Administrations, considering - that CCITT Recommendations 4.701-4.709 l to 9 define the Message Transfer Part, - that there are a number of options and points requiring further specification in these CCITT Recommendations
3、, recommends that European Administrations who wish to interconnect PSTNs and ISDNs, apply the following Recom- mendation.” Edition of August 15, 1987 / I- l CEPT T/S*43-O3*E 87 I 2326434 0008004 3 I T/S43-01 E Page 2 1. 2. 2.1. 2.2. 2.3. 2.4. 2.5. 2.6. 2.7. 2.8. INTRODUCTION This Recommendation is
4、based on Recommendations 4.701-704 i to 4 and 4.706-708 6 to 8 as specified in the Red Book, Volume VI, Fascicle VI.7. The requirements of those Recommendations shall apply unless modified by the exception statements contained in section 2. of this document and in addition shall include the specific
5、 requirements contained in section 3. of this document. Recommendations 4.705 5, Q.709 9 and 4.791 IO will apply as appropriate, unmodified, since they will have no impact on interworking in Phase 1 of GAP and are considered as for guidance only. EXCEPTIONS TO EXISTING CCITT RECOMMENDATIONS The foll
6、owing exceptions to Recommendations 4.701-704 I to 4 and Q.706-708 6 to 8 as specified in the Red Book, shall apply. National Options No national options or remarks with regard to national networks shall apply to this Recommendation. Signalling Data Links A standard bit rate of 64 kbit/s on signalli
7、ng data links applies. If signalling data links are to be provided over an analogue transmission path any necessary digital to analogue or analogue to digital conversion shall be on the multiplexed transmission link after interface point c as defined in Figure 214.702. Time-out Values The time-out v
8、alues included in Recommendations 4.703 3, 704 4 and 707 7 shall not apply, and are replaced by the values specified in paragraph 3.2. of this Recommendation. Maximum Message Length of SIF The maximum length of SIF field shall be 272 octets. Note. It is recognised that during an initial phase not al
9、l implementations will have this capability. Signalling Link Management The requirements of Recommendation Q.704 4, paragraphs 11.4 and 11.6 relating to the automatic allocation of signalling data links shall not apply. Management Blocking/Unblocking of Signalling Links The blocking/unblocking of si
10、gnalling links initiated by management action both automatic and manual as specified in Recommendation Q.704 4, paragraphs 3.2.6 (b) and 3.2.7 (b) shall not apply. Transfer Controlled Procedure The procedure for sending a Transfer Controlled Message as specified in Recommendation 4.704 4, paragraph
11、10.2.3.1 (ii) b shall be amended as follows: “A TFC is sent to the originating point for the initial message and for every n messages (n = 8 provisional value) received for the congested route set or for every link of the congested route set or for every linkset of the congested route set.” Signalli
12、ng Link Test The application of the signalling link test as specified in Recommendation Q.707 7, paragraph 2.2 shall apply to the initialization or reinitialization of a signalling link. The ability to answer an SLT message must always be provided. Edition of August 15, 1987 CEPT T/S*43-01*E 7 m 232
13、6414 OOO005 5 O 3. 3.1. 3.1.1. 3.1.2. 3.1.3. 3.1.4. TfS43-01 E Page 3 SPECIFIC REQUIREMENTS signalling Link Loading The requirements for signalling link loading that shall apply are as detailed in this part of the Recom- mendation. Basic definition Definition of signalling link load: The signalling
14、link load is defined as the ratio of the number of MSU bits transferred per second on one link at level 2, measured in one direction, including the necessary level 2 fields but excluding retransmitted MSU as well as FISU and LSSU, to the bit rate at level 2. The signalling link load is a value for t
15、he occupancy of a signalling link, at any moment of observation. Maximum signalling link load dirring normal opera fion The maximum signalling link load is a value of the signalling link load during normal operation of the signalling link, which is specified for the purpose of signalling network dim
16、ensioning and planning. Normal operation of the signalling link means that there is no changeover or rerouting in the signalling network which has any impact on the signalling link under consideration. The maximum signalling link load is the maximum value of the signalling link load which is transfe
17、rred via a signalling link at normal operation as an average value over a long period of time during the period of maximum signalling trafic and which the signalling link should be able to transfer complying with the transfer time requirements. The maximum signalling link load should not exceed O. 1
18、 erlang in the European signalling network for the first interconnections. (This value is agreed provisionally until further experience is gained.) The value of 0.2 erlang is agreed as a long term objective. Since the maximum signalling link load is a long-term average, the actual signalling link lo
19、ad can be much higher or much lower during short periods of time and will in general be lower outside the period of maximum signalling trafic. Minimum signalling link load handling capability The minimum signalling link load handling capability is specified as a minimum requirement in order to suppo
20、rt the design of equipment and the planning of the signalling routing during periods of abnormal conditions in the signalling network. The minimurn signalling link load handling capability is that value of the signalling link load which the equipment must be able to handle as a minimum during abnorm
21、al conditions in the signalling network, and which is to be seen during network dimensioning as the maximum value of the signalling link load to be carried by one signalling link during periods of abnormal conditions, with the guarantee of not being in conflict with the transfer time requirements, a
22、nd no triggering any congestion control measures in this section of the signalling network. For the first interconnections the value of 0.2 erlang is agreed in the European signalling network for the minimum signalling link load handling capacity. As a long term objective the value of 0.6 erlang for
23、 the minimum signalling link load handling capacity is anticipated. One administration is of the opinion that 0.4 erlang is a more appropriate value. This value of the minimum signalling load handling capability is specified with respect to changeover and rerouting in the signalling network and ther
24、efore to be seen as a medium-term average. For short periods of time (in the order of one second) when large queues of signal units are contained in the buffers (e.g. immediately after a signal unit error or a changeover), the signalling link load handling capability should be as high as possible to
25、 minimize the time for relieving the queues. Message length influence In a signalling network the message length is limited between a minimum and a maximum value. In the international signalling network the minimum value is 6 octets, without the level 2 fields, and the maximum value is now of 273 oc
26、tets, level 2 octets also excluded (SIF+SIO). The definition of the signalling link load does not refer intentionally to any particular value of the mean message length. In fact the network planning and the specification of equipment have to be based on stable concepts, whereas it is likely that wit
27、h the introduction of new or modified MTP Users the mean message length in a signalling network will change. So the definitions of the maximum load and of the minimum handling capability are considered as valid for any value of the mean message length between the minimum and the maximum values. . Ed
28、ition of August 15, 1987 r ,CEQT T/S*43-01*E 87 2326414 0008006 7 S T/S43-01 E Page 4 3.1,5. Graphic representation On Figure 1 (T/S 43-01) is 3.2. lly the number of messages per second transferred in one direction at the interface betkeen level 2 and levei 3 for one signalling link. And vertically
29、is represented the number of kbits transferred per second in the same direction at the same interface. On this diagram the two limits of the message length are two straight lines starting from point O. The line OGACE is the minimum value of 6 octets per message. The line OHBDF is the maximum value o
30、f 273 octets per message. The different values of the signalling link load, as defined in 3.1.1., are represented by parallel lines: line GH for 0.1 erlang, line AB for 0.2 erlang, line CD for 0.4 erlang, line EF for 0.6 erlang . Concerning the maximum signalling link load, a load less than O. 1 erl
31、ang or 0.2 erlang is any combination of messages/s and kbit/s represented by a point inside the triangle OGH or the triangle OAB of the diagram. For the minimum signalling link load handling capability, depending on the value 0.2, 0.4 or 0.6 erlang, the representation is any coordinate composed of a
32、ny number of messages/s and kbit/s located on the lines AB, CD or EF respectively. A signalling terminal must be able to handle any number of message and kbit/s represented by a point situated inside triangle OAB or triangle OCD or triangle OEF. kbi t/s 1s :Presented horizont I I I I U 100 200 300 T
33、ime-out Values The time-out values that shall apply are contained in the following tables. / 400 Edition of August 15, 1987 CEPT T/S*43-OL*E 87 E 232b4L4 0008007 9 m, Range 500 (800) to 1200 ms 0.7 (1.4) to 2 s 500 (800) to 1200 ms 500 (800) to 1200 ms 500 (800) to 1200 ms T/S43-01 E Page 5 Nominal
34、3.2.1. Recommendation Q.703 3 Time-out values and tolerances Recommen- dation 4.707 A Times T1 T3 Recommen- dation Q.703 3 Timer Range Nominal 4-12 s (equal or greater than T6 of Q.703) (Note) 30-90 s (see 4.707, paragraph 2.2, 3rd section) T1 T2 T2 low T2 high T3 T4 normal T4 emergency T5 T6 64 kbi
35、t/s T7 64 kbit/s Range 64 kbitls 40-50 s 5-150 s 5-50 s 70-150 s 1-1.5 s 64 kbit/s 7.5-9.5 s 64 kbit/s 400-600 ms 80-120 ms 3-6 s 0.5-2 s 0.8-2 s O 3.2.2. Recommendation Q.704 4 Time-out values and tolerances Recommen- dation 4.704 4 Timer T1 T2 T3 T4 T5 .T6 T8 T9 T10 T12 T13 T14 T17 Nominal Only fo
36、r automatic allocation of signai- ling terminals 8.2 s 500 ms For satellite working 500 (800) to 1200 ms 800 to 1200 ms not used 30 to 60 s 800 to 1500 ms 800 to 1500 ms 2to3s 800 to 1500 ms Note. The values in brackets should be used for long signalling delay routes (e.g. routes including satellite
37、 sections) as the lowest value of the range. Edition of August 15, 1987 t -i TfS43-01 E Page 6 REFERENCES CCITT Recommendation Q.701. Functional description of the signalling system (Message Transfer Part). CCITT Recommendation 4.702. Signalling data link. CCITT Recommendation 4.703. Signalling link
38、. CCITT Recommendation Q.704. Signalling network ftmctions and messages. CCITT Recommendation Q. 705. Signalling net work structure. CCITT Recommendation 4.706. Message Transfer Part signalling performance. CCITT Recommendation Q.707. Testing and maintenance. CCITT Recommendation Q.708. Numbering of International Signalling Point Codes. CCITT Recommendation 4.709. Hypothetical signalling reference connection. CCITT Recommendation Q.791. Monitoring and measurements for the MTP. Edition of August 15, 1987
