1、INTERNATIONAL TELECOMMUNICATION UNION ITU-T TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU INTEGRATED SERVICES DIGITAL NETWORK (ISDN) OVERALL NETWORK ASPECTS AND FUNCTIONS 1.354 (03/93) NETWORK PERFORMANCE OBJECTIVES FOR PACKET MODE COMMUNICATION IN AN ISDN ITU-T Recommendation 1.354 (Previously “C
2、CITT Recommendation”) CCITT RECMN*I.354 93 W 4862531 0577137 IT9 FOREWORD The ITU Telecommunication Standardization Sector (ITU-T) is a permanent organ of the International Telecom- munication Union. The ITU-T is responsible for studying technical, operating and tariff questions and issuing Recommen
3、dations on them with a view to standardizing telecommunications on a worldwide basis. The World Telecommunication Standardization Conference (WTSC), which meets every four years, established thc topics for study by the ITU-T Study Groups which, in their turn, produce Recommendations on these topics.
4、 ITU-T Recommendation 1.354 was prepared by the ITU-T Study Group XVIII (1988-1993) and was approved by the WTSC (Helsinki, March 1-12, 1993). NOTES 1 As a consequence of a reform process within the International Telecommunication Union (ITU), the CCITT ceased to exist as of 28 February 1993. In its
5、 place, the ITU Telecommunication Standardization Sector (ITU-T) was created as of 1 March 1993. Similarly, in this reform process, the CCW and the IFRB have been replaced by the Radiocommunication Sector. In order not to delay publication of this Recommendation, no change has been made in the text
6、to references containing the acronyms “CCITT, CCiR or FRB” or their associated entities such as Plenary Assembly, Secretariat, etc. Future editions of this Recommendation will contain the proper terminology related to the new ITU structure. 2 telecommunication administration and a recognized operati
7、ng agency. In this Recommendation, the expression “Administration” is used for conciseness to indicate both a O ITU 1993 All rights reserved. No part of this publication may be reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying and microfilm, without
8、 permission in writing from the ITU. CCITT RECMNxI.354 73 4862591 0577138 035 3 i Recommendation 1.354 NETWORK PERFORMANCE OBJECTIVES FOR PACKET MODE COMMUNICATION IN AN ISDN (Helsinki, 1993) 1 Introduction This Recommendation specifies speed, accuracy, and dependability performance parameters and w
9、orst-case objectives for packet switched connection types in an ISDN. The defined parameters and objectives apply to connection establishment, user information transfer, and clearing in switched packet mode calls and to user data transfer in PVCs. Worst case mean and 95% probability values are speci
10、fied for each virtual connection portion type defined in Table i. The term “worst case” means that these values should be met during the normal busy hour in the worst performing virtual connection portion used. The busy hour for connection establishment and release and the busy hour for the user inf
11、ormation transfer might not be coincident. NOTE -Cases where the network is in overload condition are not covered by this Recommendation. This Recommendation does not address the use of circuit mode bearer services to provide access to a PSPDN (case A of Recommendation X.31). It is recognized that i
12、ncreased integration in the future may allow for a tightening of these specifications. 2 The performance model and reference events (RES) defined in RecommendationsX.134 to X.136 apply in this Recommendation with the following interpretations and amendments. The correspondence between Recommendation
13、s X.135 and X.136) portion boundaries and the measurement points (MPs) used in this Recommendation is shown in Table 1. This association places the MPIs on the international side of the ISCs. The X.134 incoming cali RE, i(X.25), is replaced with the 1.353 Setup entry RE, Plb(Q.931), in cases where t
14、he called CEQ; either a) subscribes to conditional notification and does not have a B- or D-channel capable of accepting the call connected to the PH, or b) subscribes to unconditional notification. Performance model and reference events i) 2) 3 With the above MPhoundary identifications, the referen
15、ce events specified in Recommendation X.135 apply to the connection processing parameters defined below, with one exception. That exception occurs only in the case of call Set-up delay and is detailed in 3.1.1. The variables X, Y and Z used below are defined in 2.3K.135, 3.2K.135 and 5.2K.135 respec
16、tively. Connection processing delays in ISDN packet switched connections ) The same performance model applies to both Recommendations X.135 and X.136 though it is only specified in detail in Recommendation X.135. Recommendation 1.354 (03/93) 1 CCITT RECMN*I-354 93 4862593 0577339 T7L MPT1 MPT2 Two t
17、ypes of national and international portions (A and B defined in Table 1K.135) are used in this Recommendation. End-to-end connections are built up from combinations of these national and international portions. The concatenation method of the means and 95th percentiles of these national and internat
18、ional portions is given in Annex Cm.135. Annex A contains illustrations of events sequences during call Set-up and clearing. 2G.25) 3m.25) 1 (X.25) 4W.25) TABLE lA.354 MPhoundary correspondence MPII MPI2 Rec. 1.354 Rec. X.135 I 1 (X.75) 2G.75) 1 (X.75) 2m.75) MPI2 Bn-2 3.1 Call Set-up delay Cd Set-u
19、p delay is defined first at a single MP, then between a pair of MPs (based on the former definition). Finally end-to-end ca Set-up delay is defined. Tables 1B.134 and 2Bc.134 define the performance-significant reference events and the resulting states for X.25 and X.75 packets respectively. Table 2
20、identrfies the performance-significant reference events and the resulting states for Q.93 1 messages. TABLE 2A.354 Performance-significant reference event I Performance-significant reference event I Measurement point Starting event code Ending event code 3.1.1 Call set-up delay definition call Set-u
21、p delay at a single MP: Call set-up delay at a single MP (MP?) is defined as the period of time that starts when a starting reference event creates an event at MPi and ends when the corresponding ending reference event returns and creates an event at MPi. 2, MP; or MP, is one of MPTl, MPT2, MPI1 or
22、MPI2. 2 Recommendation 1.354 (03/93) CCITT RECMN*Im354 93 m +Ab2593 0577340 793 m Measurement point MPT2 Call Set-up delay at a single MP = (t2 - ti) where tl is the time of occurrence of the starting RE; t2 is the time of occurrence of the ending RE. call set-up delay between two MPs: Call set-up d
23、elay between two measurement points MP, and MP. (with MP. Wing further from the ding party than MPj), is defined as the difference di - di of the connection set-up delays at dPi and MPj respectively. Call Set-up delay between two MPs = (di - di) where di is the connection Set-up delay at MPj; di is
24、the connection Set-up delay at MPi. end-to-end call set-up delay: End-to-end call Set-up delay is the connection setup delay, dl - d2, between the two The exceptional case (in terms of reference events) occurs when the called user; either MPTs, MPT1 and MPTF a) b) subscribes to unconditional notific
25、ation. subscribes to conditional notification and does not have a B- or D-channel capable of accepting the cail connected to the PH; or Performance-significant reference event Starting event code Eodiog event code P1 b(Q.93 1) 4e.25) In this case the starting RE for call set-up delay at the MPT2 is
26、based on the receipt of a Q.931 Set-up message announcing the packet caii. Ail other starting and ending RES at the other MPs are those in Table 2. Table 3 provides the starting and ending RES for the MPT2) in this case. TABLE 3L.354 3.1.2 Call set-up delay values Worst-case values for cail Set-up d
27、elay for the various virtual connection portions are given in Table 4, 3.2 Clear indication delay Clear indication delay is defined as in Recommendation X.135. Worst-case values for clear indication delay for the various virtual connection portions are given in Table 5. 4 Packet information transfer
28、 delay parameters 4.1 Data packet transfer delay Data packet transfer delay is defined as in Recommendation X. 135. Worst-case values for data packet transfer delay for the various virtual connection portions are given in Table 6. Recommendation 1.354 (03/93) 3 TABLE 4n.354 Worst-case call Set-up de
29、lay values for virtual connection portions (ISDN) Mean (ms) 95% (ms) Virtual connection portion type (ISDN) I 1132 + X 1732 + X 250 1 600 1885 + X 2431 +X 250 1800 Statistic I National I International Mean (ms) 95% (ms) A A B A B 677 + Z 927 + Z 110 800 1128 + Z 1380 + Z 110 900 B A B A A B B Mean (
30、ms) 95% (ms) 492 + Y 792 + Y 215 950 925 +Y 1164+Y 21 5 1125 TABLE 511.354 Worst-case clear indication delay values for virtual connection portions (ISDN) I Virtual connection portion type (ISDN) I Statistic I National international I NOTES 1 performance is expected to improve. 2 Ali values are prov
31、isional. These values are based on a scenario with minimal integration between ISDN and X.25. As integration increases, TABLE 6h.354 Worst-case data packet transfer delay values for virtual connection portions (ISDN) I Virtual connection portion type (ISDN) Statistic I National International NOTES 1
32、 performance is expected to improve. 2 Ail values are provisional. These values are based on a scenario with minimal integration between ISDN and X.25. As integration increases, 4 Recommendation 1.354 (03/93) CCITT RECMN*I=354 73 = 4862571 0577142 5bb 4.2 Packet mode throughput parameters For furthe
33、r study. 5 For further study. Packet mode accuracy and dependability parameters Annex A (to Recommendation 1.354) Illustration of event sequences during cai1 Set-up and clearing (This annex forms an integral part of this Recommendation) The following two figures illusirate the maximum number of mess
34、age sequences during call set-up in both the usual case, Figure A. 1, and the exceptional case, Figure A.2. Figure A.3 shows the messages observed during call clearing. Not ail message sequences confined to the MPTs wili always occur, but those associated with d, and d, will always occur. Recommenda
35、tion 1.354 (03D3) 5 CCITT RECMN*I.354 93 4Bb2591 0577143 4T2 = SABME(x, s) D link to . UA, s) signalling i(x, s)S, bo = ckt; Connect BI to the PH layer dl National portion H cc / Internationa portion - / National portion - CR IC d2 CA MPT, MPI, MPI, MPT, .-p Q.921, (2.931, LAPB, LAPD signalling -b X
36、.25, X.75 signalling + = dl- d2 T1813650-911d01 FIGURE A.lb.354 End-to-end call Set-up delay/usual case 6 Recommendation 1.354 (03/93) CCITT RECMN*I-354 93 m 48b2593 0577344 339 m SABM E( x,s) D link to signalling JX, s) S, bo = ck. l(x. s) CPI Connect BI to the PH SABME(B)/(x. p) layer dl t Nationa
37、l portion Internationa portion / National portion CR MPT1 MPII MPI2 MPT2 a) May convey calling address or optional facilities information. Q.921, Q.931, LAPB, LAPD signalling + = dl-d2 .-b X.25, X.75 signalling T1813650-91/d02 FIGURE A.Sfl.354 End-to-end call Set-up delay/exceptional case Recommenda
38、tion 1.354 (03/93) 7 CCITT RECMN*I.354 93 48b259L 0577145 275 = d National International National portion A portion =I1 portion 1 4 Clear indication - Clear confirmation MPTI MPIi MP12 MPT2 T1816030-92/dO3 X.25, X.75 signalling FIGURE A.3fl.354 End-to-end clear indication delay Appendix I (to Recomm
39、endation 1.354) Method used to calculate worst-case ISDN performance values (This appendix does not form an integral part of this Recommendation) This Recommendations specification of worst-case values for ISDN packet-mode bearer services is based on differences between a packet connection over an X
40、.25 packet network and over an ISDN (see Figure 1.1). A methodology is utilized which converts the values specified in Recommendation X.135 to the values in this Recommendation. The differences between a packet connection over an ISDN and the packet connections detailed in Recommen- dation X.135 are
41、 the presence of a packet handler (PH) functionality in the ISDN end office (acting like an additional packet switch) and the presence of an X.75 (or Network internal protocol) link from the PH to the local PSPDN as illustrated in Figure I. 1. 8 Recommendation 1.354 (03/93) CCITT RECflN*I.354 93 H 4
42、8h259L 057714b 101 National portion l i i TE/ i I ISDN I circuit networtk j section protocol I EX.135 . 1- MPT, International portion National portion RNIS 16 I x.75 or Access! Internal circuit 1 network section I Protocol Rec. X 135 i i j Rec. X.135 i I I -1 MPT, New elements (dashed line) + X.135
43、scope (solid line) 1.354 scope FIGURE I.lD.354 Performance model comparison of X.135 and L354 3, An ISDN correction factor4) based on the new elements in the performance model is added to the mean delay values in Recommendation X.135. This correction factor is calculated on the basis of one PH and X
44、.75 link at each end of the connection. The 95th percentiles of the national portions in Recommendation 1.354 are calculated as the ratio of the 95th percentiles to the mean in Recommendation X.135 times the new mean of this Recommendation. 3, The model is used only to derive the performance values.
45、 The actual implementation of ISDNs carrying packet mode connection 4, The correction factors used in this Recommendation are not specifications of equipment performance. types (case B of Recommendation X.31) may be different. Recommendation 1.354 (03193) 9 CCITT RECMN*I-354 93 4862573 0577347 048 Printed in Switzerland Geneva, 1993
