1、CCITT RECMN*I.325 (REV*L) 93 W 4862573 0580577 T7b m INTERNATIONAL TELECOMMUN CATION UN ION ITU-T TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU 1.325 (03/93) INTEGRATED SERVICES DIGITAL NETWORK (ISDN) OVERALL NETWORK ASPECTS AND FUNCTIONS REFERENCE CONFIGURATIONS FOR ISDN CONNECTION TYPES ITU-T Re
2、commendation 1.325 (Previously “CCIlT Recommendation”) CCITT RECMN+I.325 (REV+L) 93 W 48b259L 0580578 902 M FOREWORD The ITU Telecommunication Standardization Sector (ITU-T) is a permanent organ of the Intemational Telecom- munication Union. The IT-T is responsible for studying technical, operating
3、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 years, established the topics for study by the ITU-T Study Groups which, in their turn,
4、 produce Recommendations on these topics. ITU-T Recommendation 1.325 was revised by the IT-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
5、to exist as of 28 February 1993. In its place, the IT Telecommunication Standardization Sector (IT-T) was created as of 1 March 1993. Similarly, in this reform process, the CCIR and the IFRB have been replaced by the Radiocommunication Sector. In order not to delay publication of this Recommendation
6、, 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 will contain the proper terminology related to the new ITU sructure. 2 telecommunication a
7、dministration and a recognized operating agency. In this Recommendation, the expression ?Administration? is used for conciseness to indicate both a O IT 1993 All rights reserved. No part of this publication may be reproduced or utilized in any form or by any means, electronic or mechanical, includin
8、g photocopying and microfilm, without permission in writing from the ITU. CCITT RECMN*I=325 (REV*l) 93 48b259L 0580579 849 TABLE OF CONTENTS Page 1 summary . 1 2 1nb.oduc . 1 2.1 Objective . 1 2.2 Relationship to other I-Series Recommendations . 1 3 Development of the concept of reference configurat
9、ions . 3 3.1 Definitions 3 3.2 Generic reference configuration 3 3.3 Principles for developing specific reference configurations for ISDN connection types 6 3.4 Connection elements . 6 3.5 Functional groupings 7 3.6 Reference points 7 4 Specific reference configurations 8 4.1 64 kbids class 8 4.2 Pa
10、cket class . 9 4.3 Broadband class 10 . Recommendation 1.325 (03-93) i CCITT RECMN*I.325 (REV+L) 93 4862593 0580580 5b0 Recommendation 1.325 REFERENCE CONFIGURATIONS FOR ISDN CONNECTION TYPES (Melbourne, 1988; amended at Helsinki, 1993) 1 Summary In order to apply the network performance parameters
11、to the ISDN, some form of hypothetical reference connections (HRXs) are necessary. These HRXs should be based on appropriate reference configurations for the connection types to which the network performance parameters refer. This Recommendation shows how reference configurations can be developed fo
12、r the ISDN connection types and what form such reference configurations should take. 2 Introduction 2.1 Objective The general architectural model of the ISDN (see Figure 1) is given in Recommendation 1.324. The detailed network capabilities of the ISDN, as described by connection types in Recommenda
13、tion 1.340, are described topologically by this Recommendation giving reference configurations as appropriate for (an) ISDN connection type(s). These reference configurations do not give details on the number of switching nodes, length of connection, transmission facilities used, etc. However, they
14、do give the details on the reference configuration (or topological configuration) of all matters described by the connection type to which they refer. Therefore they should include derails on the signalling, existence of switching functions, channels, etc. Based on these reference configurations, ap
15、propriate HRXs should be developed which will be particular to network performance parameters or groups of network performance (NP) parameters. The details on these HRXs will be appropriate for the NP parameters in question. In order to keep the task of developing reference configurations and the su
16、bsequent HRxs, and the allocation of performance values to these HRXs, to manageable proportions, it is necessary to have as limited a set as possible of specific reference configurations. Consequently the ISDN connection types in Recommendation 1.340 need to be arranged in different classes which d
17、iffer significantly from each other such that they require a separate reference configuration model. S orT SorT FIGURE lA.325 Simple cloud model of the ISDN 2.2 Relationship to other I-Series Recommendations The concept of reference configurations has already been used in a number of areas of standa
18、rdization of the ISDN. It is therefore necessary to consider the concept of connection type reference configurations in the context of these developments. 2.2.1 ISDN architectural model It should be noted that defining a set of reference configurations presupposes a particular architectural model of
19、 an ISDN (see Figure 2). The architectural model for the ISDN is contained in Recommendation 1.324. In addition, Recommendation 1.3 10 on the ISDN network functional principles, when considered together with Recommen- dation 1.324, gives the general basis of the architecture of the ISDN from which i
20、t is possible to develop reference configurations for ISDN connection types. Recommendation 1.325 (03/93) 1 CCITT RECMN*I-325 (REV*3) 93 I 4862593 0580583 4T7 I i i i i i i i i ! Low layer capabilities (BLLF and ALLF) i #.-.-.-.-.-.-.-.- .-._ .- - -.-_._-.- 4-4.- *_.-.-.-.-.-.-.-U.-_ I o.o.-. -.-.-.
21、-.-.- .-._ i -.C High layer capabilities “I i (BHLF and AHLF) /J -.-. -.-_ _.-.-.-.-y- I I j f i i i i i i i i i i i i i i i i i i i i i i I signalling capabilities i . -.-.-.-J I i i i I i i - I I.“. I *- -.-.-. - national transit connection element; - international transit connection element. Inte
22、rnational CRF Local National / National Local -_ .Access- National transit :htemational National transit WAccessl CE CE CE CE CE T1301390-93d05 IRP Internal reference point CRF Connection related functions CE Connectiondement FIGURE 5A.325 Reference Coirfguration of public ISDN cwnectioo type In the
23、 case where the customer network consists of ISPBXs, two additional kinds of connection elements, a private access CE, and a private transit CE are identified as shown in Figure 6. 6 Recommendation 1.325 (03/93) CCITT RECMN*I*325 (REV*:L) 73 Bs +Ab2571 058058b T87 I ntemational CRF Private Private N
24、ational / National Private Private IOCal transit Local transit transit Local transit local I , -1- -1- -P -r- p - -8- -8- -8- Private access Private Access National transit Intemational National transit Access CE Private Private access CE transit CE CE CE CE transit CE CE CE T1301400Wd06 CRF Connect
25、ion related functions NOTE - The internai reference points (IR have been erased in this fgure. FiGURE 6A.325 Reference contiguration of overail ISDN connection types for a mixed ISPBWpublic scenario 3.5 Functional groupings As stated in the definition in 3.1, in order to define reference configurati
26、ons, it is necessary to define certain functional groupings and also reference points which are the conceptual points dividing these functional groupings. In the description of the connection type reference configuration, some of the major functional groupings involved can be considered under the co
27、ncept of connection related functions (0 as described in 4.2.2.14.324. The concept of the CRF includes all the functional groupings involved in establishing and controlling the connections within the particular connection element. In the case of the international transit connection element, two CRFs
28、 are shown in Figure 6 in order to retain the symmetry of the diagram. The specific capabilities of each CRF are not specified in the general reference model. This is done in the reference configuration for each group of connection types. The boundary of the CRF should not be associated with the bou
29、ndary of an exchange as these may not correspond to each other. Other functional groupings which are necessary for the complete description of the connection type reference configuration include line termination (LT), digital link, packet handling (PH) function and various functions associated with
30、the signalling network. 3.6 Reference points The other element involved in the description of a reference configuration is the reference point concept. The I-series already identifies reference points S and T (in Recommendation 1.411) and Kx, M, Nx and P (in Recommen- dation 1.324). As can be seen f
31、rom Figure 6, some further internal reference points need to be identified. Further study is required to see whether these and any further reference points need to be defined. Recommendation 1.325 (03/93) 7 CCITT RECMN*I=325 (REV*L) 93 I 4Bb2591 0580587 915 I In describing the reference configuratio
32、n for the ISDN connection types, an important consideration vis-a-vis the reference points is the following. In Figure 6, and the following diagrams, the end points of the overall connection is shown as being at the T reference point The reason for this is as follows. Reference point S is identical
33、to reference point T when the NT2 function is null (Recommendation 1.411). When the NT2 function is non-zero, then the performance of the overall connection will be made up of the performance of the ISDN network connection 6.e. between the two interfaces at reference point i) and the sum of the perf
34、ormance of the customer network connections (i.e. between the interfaces at reference points S and T at each end). Recommendation G.801 also uses this approach by defining the ends of the digital HRX as being at tbe T reference point. 4 Specific reference configurations This general reference model
35、needs now to be associated with specific connection types in order to develop specific reference configurations. However, Recommendation 1.340 allows for so many variations in its different attributes, leading to a very large number of potential connection types, that is necessary to consider only c
36、ertain dominant attributes in order to produce a shorter list of reference configurations. For an initial analysis, only the fust two of the four dominant attributes listed in Recommendation 1.340 need to be considered. Therefore the “information transfer mode” and “information transfer rate” will l
37、ead to three general classes of ISDN connection types, viz: a) circuit: - 64kbit/s, - greater than 64 kbit/s (broadband); b) packet. The other two dominant attributes (“information transfer” and “establishment of connection”) do not require separate reference configurations but will manifest themsel
38、ves by different performance values. This limited set of connection types is subsequently modelled in the associated reference configurations taking into account a limited number of frequently realized connection topologies. 4.1 64 kbis class This class includes connection types Al to A12 of Table 2
39、A.340, Le. unrestricted digital, speech and 3.1 WIz audio information transfer susceptances and switched semi-permanent and permanent establishments, The variation of the information transfer capability is determined by the network performance parameter values allocated to each portion of the connec
40、tion. For example, use of digital speech interpolation in the international connection element would restrict the connection type to speech or 3.1 kHz audio. Likewise, the differences between permanent connection types and switched connection types would manifest themselves in differences in the val
41、ue of parameters such as connection establishment tune, etc. This approach means that there is a small number of reference configurations, but that all of the different connection types listed in Recommendation 1.340 would need to be tabulated for the allocation of performance values. Figure 7 shows
42、 the reference configuration that is proposed for this class of ISDN connection types. In the case where the customer network consists of ISPBXs, two additional kinds of connection elements, a private access CE and a private transit CE, are involved, as shown in Figure 8. 8 Recommendation 1.325 (03/
43、93) W o u) c .- - 3 - 2 O m z .- c W o u) u) o _- International transit CE _a International International transit transit -T c- TE T130141O-93/d07 TE a) See Figure 1Q.512. S C 64 ks circuit sikh funcm Signalling handing and exchange control fmhs FIGURE 7n.325 Reference configurntion - 64 kbiffs circ
44、uit group 4.2 Packet class Recommendation X.31 illustrates the scenarios involved in providing packet switched capability in the ISDN. These are in fact reference configurations for the access connection element. The possible reference configurations for the B-channel access packet mode connection t
45、ype class are shown in Figures 9 and 10. It should be noted that the Recommendations in the X.130-Senes also use the concepts of national and international portions of the connection for the purposes of the allocation of the division of network performance parameter values. In those cases the bounda
46、ry between the national and the international portions is in the middle of the international data switching exchange (IDSE) or internationai switching centre (ISC). Further study is required to see if this approach should be taken in the ISDN. Recommendation 1.325 (03/93) 9 CCITT RECMN*I.325 (REV*L)
47、 93 E 48b259L 0580589 798 .-. I I T I- I In the case where the customer network consists of ISPBXs, two additional kinds of connection elements, a private access CE and a private transit CE, are involved. In addition, private packet handler functions are involved, as shown in Figure 11. I .-.I.-.- I
48、 I I .-.- J I 4.3 Broadband class I I I Further study is required to determine what the salient features of this class of ISDN connection types are. According to Recommendation 1.340, it would include permanent and semi-permanent connections at 384, 1536 or 1920 kbit/s. I I sw I c. I I I SW C 64 WVs
49、 circuit svAtch tuiccm Signalling handling and exdiaige mtrd ftmctions I I I FIGURE 8D.325 Overall ISDN reference configuration - 64 kbih circuit group I I I I I I I I 10 Recommendation 1.325 (03/93) I I I =I I I %i =I $1 I I I I I I I IC sw I I I I I I I l I I I I I I I I I cl I 1 Y .- - 81 I I .-. I I I I s I ,-J I .-.I.-.- I I I .I., / / Transit link Transit link Transit link P i-i I I a Common channel signalling system TE Eh. Transit * +or+LJ+ link SeeFjgure2JX.31. PH, Level 2 packet harder PH Level 3 pack
