1、CCITT RECNNaE.713 72 a 4862573 0578b33 T55 M INTERNATIONAL TELECOMMUNICATION UNION CCITT THE INTERNATIONAL TELEGRAPH AND TELEPHONE CONSULTATIVE COMMITTEE TELEPHONE NETWORK AND ISDN QUALITY OF SERVICE, NETWORK MANAGEMENT AND TRAFFIC ENGINEERING E.713 (1 0/92) CONTROL PLANE TRAFFIC MODELLING Recommend
2、ation E.713 CCITT RECMN*E.713 92 W 486259L 0578634 991 I FOREWORD The CCITT (the International Telegraph and Telephone Consultative Committee) is a permanent organ of the International Telecommunication Union (ITU). CCITT is responsible for studying technical, operating and tariff questions and issu
3、ing Recommendations on them with a view to standardizing telecommunications on a worldwide basis. The Plenary Assembly of CCITT which meets every four years, establishes the topics for study and approves Recommendations prepared by its Study Groups. The approval of Recommendations by the members of
4、CCITT between Plenary Assemblies is covered by the procedure laid down in CCITT Resolution No. 2 (Melbourne, 1988). Recommendation E.713 was revised by Study Group II and was approved under the Resolution No. 2 procedure on the 30th of October 1992. CCITT NOTES 1) telecommunication administration an
5、d a recognized private operating agency. In this Recommendation, the expression “Administration” is used for conciseness to indicate both a I 2) A list of abbreviations used in this Recommendation can be found in Annex B. O ITU 1993 All rights reserved. No part of this publication may be reproduced
6、or utilized in any form or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from the ITU. CCITT RECMN*E.733 92 4862533 0578635 828 m Recommendation E.713 CONTROL PLANE TRAFFIC MODELLING (revised 1992) 1 Control plane traffic For the purposes
7、 of teletraffic engineering, the control plane traffic load is assumed to be generated by call attempts on the network. These call attempts are part of the call pattern described in Recommendation E.7 1 1. This Recommendation considers traffic loads at the lower three layers of the CCITT 7-layer ref
8、erence models (see Recommendations 1.310 and 1.320) described for ISDN in Recommendation Q.931 and in Signalling System No. 7. The control plane traffic of an ISDN network includes all the control signais sent through the ISDN network. The types of control signals are: I) signals for user call attem
9、pts a) b) c) d) to set up the connection paths in the user plane (reservation of time slots for circuit switched connections or control for the virtual calls of packet-switched connections); to release the connection paths in the user plane; if required, to order additional communication facilities
10、or change of service by the users during the time of user information transfer; possibly to send charging information during the time of user information transfer. 2) User-to-user information messages). Because control plane traffic due to user-tu-user messages is left for further study, this Recomm
11、endation will The control plane traffic uses two types of channels in the network a) the 16 kbit/s or 64 kbit/s D-channels in the user access, and b) the 64 kbit/s Signalling System No. 7 channels connecting two different signalling points. consider only signals for user call attempts. 2 Signalling
12、traffic The end-to-end ISDN signalling traffic depends on the call pattern arrival process defined in Recommen- dation E.7 1 1 and on the signalling protocol. The basis for the estimation of the signalling traffic is the information given in the Recommendations of the I- and Q-Series dealing with th
13、e number and structure of the signals in the D- and Signalling System No. 7 channels for any type of attempt. The total signalling traffic is composed of these signals. The number of signals may be different for each different type of attempt. The analysis of user-to-user messages in the control pla
14、ne is left for further study. Recommendation E.713 (10/92) I CCITT RECNN*E.713 92 4862591 0578636 764 = 3 Estimation of the signalling traffic for a single call attempt In Figure 1E.7 i 3 the network components supporting the control plane of the ISDN reference connection of Figure 1 E70 i are consi
15、dered. In each section, a significant point is defined: DA (D-channel, A user side): S/T interface at an A user side DB (D-channel, B user side): S/T interface at a B user side CA (S.S. No. 7 channels, A user side): Outgoing side of the local exchange LE(A). CB (S.S. No. 7 channels, B user side): In
16、coming side of the local exchange LE(B). Significant : points: DA CA CB : T0203630-93 DB TE(A) Originati terminal equipment LE(A) Originating local exchange LE(B) Terminating local exchange TE(B) Terminating terminal equipment FIGURE 1B.713 Signifikant points in the control plane The signal flow whi
17、ch is necessary to perform the control functions of a particular call attempt may be represented by a signal flow diagram. It contains all the signals passing the significant points in the control plane for the considered attempt. Figure 2E.713 shows the basic scheme of this signai flow diagram. The
18、 arrows represent the layer 2 signals in the three connection phases: call establishment, user information uansfer and call release. An example of a signal flow diagram for a successful circuit switched cail attempt is given in Annex A. The signal flow diagram is the basis for the estimation of the
19、amount of signalling traffic caused by the considered attempt using the reference connection. The signalling traffic of a single attempt in a given section of the control plane associated with a significant point can be described by two sets of parameters: 1) the total number of signals passing the
20、significant point in the three call-connection phases in the A-to-B direction ,and in the E-to-A direction, as in Figure 2E.713; 2) the length of each signai type passing the significant point in the A-to-E and the B-to-A direction. 2 Recommendation E.713 (10/92) L Signals in phase 1 (call establish
21、ment) Signals in phase 2 (Merinfomiauon transfer) Signals in phase 3 (call reiease) FIGURE 2E.713 Basic scheme of a signai tlow diagram of a call attempt for the reference conneciion 4 Estimation of the total signalling trafic The total number of signais in the control plane over a reference period2
22、) is determined by summing the number of signals caused by call attempts handled in the associated user plane during the reference period. Therefore the estimation of the number of signais is based on the estimation of the amount and types of attempts in the user plane. In order to estimate the amou
23、nt of signals, it is necessary to accept a traffic model for the traffic in the user plane assuming the total number of attempts over the reference period and the breakdown of these attempts into the different types of attempts, such as successful call attempts, unsuccessful call attempts and caiis
24、to busy tone. The total traffic load of a section caused by the signals is expressed by the total amount of bits crossing its significant point, In order to estimate the amount of this traffic load it is necessary to multiply the length of each particular type of signals by the number of signals of
25、each type occuring during the reference period and summing over all types of signals occuring during the reference period. Since the number and length of the signals do not vary widely for most types of attempts, initially this traffic model will be adequate by taking into consideration only the mos
26、t frequently experienced types of attempts. 2, The proper reference period to use for dimensioning is for further study. Recommendation E.713 (10/92) 3 CCITT RECMN*E.713 92 4862571 0578638 537 W The characteristic of the signalling traffic in a particular section of the control plane will depend on
27、such factors as: a) the total traffic load caused by layer 2 and 3 signais for the attempts; b) the distribution of call attempts and release arrivals. The impact on teleuaffic engineering caused by a full characterization of the arrival process is left for further study. Using Figure uE.7 13, the s
28、ignalling traffic load at a significant point can be estimated. If, over the reference period: i is the call phase, j is the signai type, no (u) is the average number of signais of type j in call phase i in the A-to-B direction, n (6) is the average number of signals of type j in call phase i in the
29、 B-to-A direction, 4 is the length of signal of type j, T is the total number of signals types, L(u) L(d) is the toial load in the A-to-B direction, is the total load in the B-to-A direction, then: Each nij (u) and nu (d) must be estimated from the number of call attempts and the call attributes in
30、the user plane over the reference period. An example of this procedure is given in Annex A. 4 Recommendation E.713 (1 0/92) CCITT RECMN*E-713 72 4862571 0578637 473 ANNEX A (to Recommendation E.713) Example of procedure for estimating the total signalling traffic in a D-channel A. 1 Signulling truff
31、ic for one cull utlempt A call attempt of the following type is considered: - effective call attempt, - circuit switched connection, - - - - - incanual answering terminal. en-bloc sending of dialled information, call to a11 appointed terminal, no additional control signais during the information tra
32、nsfer phase, installation of data link in the D-channels required for establishment and release of the connection, The signal flow diagram for this type of call attempt is given in Figure A-1E.713 and Figure A-2E.713. Three kinds of signals are indicated in Figure A-lE.713: - layer 3 signals, - - la
33、yer 2 signais for the activation and deactivatioii of the data links, end-to-end signais via the S.S. No. 7 network. Figure A-2E.713 presents the breakdown of the D-channel signals into layer 2 for the case of multiple tenniiials on the terminating side. The breakdown of the S.S. No. 7 messages and
34、the total length of signal in the considered call attempt is for further study. A.2 Signulling trufic for udditionul types of cull utternpts For further study. Recommendation E.713 (10192) 5 CCITT RECNNUE.713 92 4862593 0578640 195 SABME -.-I -.-._ * *_p! _-.- -.-. SETUP I I I I i I Layer3rnessage b
35、 Layer2frame _-_-_ L End-toend message * I IAM(CR) + CALL PRIC 4 I I SCCP-cc I I I ACM S.S. No. 7 messages: I I t 1 .- -_._ -, UA t b SETUP I IAM(CR) I c _._-.- SABME -. ACM 1 ALERT I IAM cc CR ACM ANS REL RLSD RLC I I 4 CONN 4 - b b ANS CONN ACK 1 ALERT I I I I i I I I I CONN ACK Inlial address mes
36、sage Connection confirmation Connection request Address complete message Answer Release Released Release complete Note - See Recommendations 1.441 and 1.451 for the abbreviations of layer 2 frames and layer 3 messages. In this Recommendation, these are referred to as signals. FIGURE A-1fi.713 Signal
37、 flow diagram for a circuit switched connection with en-bloc sending of dialled information (to appointed terminal) 6 Recommendation E.713 (1 0/92) CCITT RECllNlE.713 92 m 4862593 0578641 O21 m I TE,RMINATING TE: ORIGINATING TE NETWORK TERMINATING TE1 - c 4 c - & I SETUP _7 DISC - REL RLC Y (DL-REL)
38、 , L2 SABME Y UA I RR I- - - I 7 -8 RR .-_._ I _L RR 4 _._ *-.-*- DISC _e & Il DISC REL 7 R LC 7 (DL-REL) L2 L3 L2 L3 L2 Layer2 L3 Layer3 Note - See Recommendations 1.441 and 1.45 1 for the abbreviations of layer 2 Games and layer 3 messages. In this Recommendation, these are referred to as signals.
39、 FIGURE A-2fi.713 Signal flow diagram Example of Figure A-llEI713 with layer 2 signais on the D-channels and with multiple terminals on the terminating side for an effective call attempt Recommendation E.713 (10/92) 7 ACM ANS cc CR IAM ISDN LE REL RLC RLSD S.S. No. 7 TE CCITT RECRN*E*713 92 W Y86259
40、1 0578642 TbB ANNEX B (to Recommendation E.7 13) Alphabetical List of abbreviations used in this Recommendation Address complete message Answer Connection confirmation Connection request Initiai address message Integrated services digital network Local exchange Release Release complete Released Signalling System No. 7 Terminai equipment 8 Recommendation E.713 (10192) CCITT RECMNrE.713 92 4Ab2591 0578643 9T4 Printed in Switzerland Geneva, 1993
