1、-. - ._I_- INTERNATIONAL TELECOMMUNICATION UN ION ITU-T TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU INTEGRATED SERVICES DIGITAL NETWORK (ISDN) INTERNETWORK INTERFACES 1.51 5 (03/93) PARAMETER EXCHANGE FOR ISDN INTERWORKING ITU-T Recommendation 1.51 5 (Previously “CCIT Recommendation“) ITU-T RECM
2、N*I.SL5 (REV*L) 93 4862593 058278Z T8T W FOREWORD The ITIT Telecommunication Standardization Sector (ITU-T) is a permanent organ of the International Telecom- munication Union. The -T is responsible for studying technical, operating and tariff questions and issuing Recommendations on them with a vie
3、w 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, produce Recommendations on these topics. ITU-T Recommendation 1.51
4、5 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 (ITCJ), the CC1” ceased to exist as of 28 February 1993. In its place, the ITU Telecommunic
5、ation 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 Similarly, in this reform process, the CCIR and the IFRB have been replaced by the Radiocommunication Sector. In order not to delay publication of this Recommendation, no change has been made in the text to references containing th
6、e 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 structure. 2 telecommunication administration and a recognized operating agency. In this Recomme
7、ndation, 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 aiy form or by aiy means, electronic or mechanical, including photocopying and microfilm, without permission in writing fro
8、m the ITU. CONTENTS General 1.1 scope 1.2 Definitions Principles . 2.1 2.2 Relationship of parameter exchange to call establishment . Parameter exchange procedures . 3.1 Out-band parameter exchange . Parameter exchange functions 4.1 Numbering parameters 4.2 Protocol control parameters . 4.3 DTFYDCE
9、configuration parameters . 4.4 Operations and maintenance parameters . 4.5 Network parameters Parameter exchange for selection of IWF . 5.1 Single stage 5.2 Two stages Types of parameter exchanges . 3.2 In-band parameter exchange . Appendix I -Protocol for identification of terminal adaption protoco
10、ls . 1.2 Identification procedure 1.4 1.5 TA decision II . 1 II.2 1.3 End-to-end synchronization Passing the protocol identifier (PI) Appendix II - TA protocol self identification MTAs intended to interwork with uni-protocol TAS MTAs intended to interwork with other MTAs . Recommendation 1.515 (0319
11、3) Page 1 1 1 3 3 4 6 6 6 7 7 7 7 8 8 8 8 8 9 9 9 12 12 14 14 15 i PARARIETER EXCHANGE FOR ISDN INTERWORKING I (Melbourne, 1988; amended at Helsinki, 1993) 1 General 1.1 Scope The objective of this Recommendation is to provide overall parameter exchange principles and functional descriptions for ISD
12、N interworking. This Recommendation describes the principles for parameter exchange mechanisms. It is recognized that depending on the available (end-to-end) signalling capability, the exchange of parameters may use either out- or in-band procedures. Parameter exchange may be necessary to establish
13、compatible interworking functions for a variety of applications. Typical examples where parameter exchange takes place include, terminal adaption compatibility establishment, modem type selection and voice encoding compatibility establishment. This does not imply, however, any requirement for an ISD
14、N to support network based modem interworking. Figure 1 illustrates several voice and data applications, supported by different networks and mechanisms. Parameter exchange may be necessary where interworking between different terminals or networks (as per other Recommenda- tions) is required. NOTE -
15、 Where interworking procedures exist, the appropriate references are made herein. 1.2 Definitions Use is made of the following terms within this Recommendation. These terms do not necessarily refer to any existing protocol structure, rather they define information requirements in the context of this
16、 Recommendation. bearer capabiiify information: Specific information defining the lower layer characteristics of the network. low layer compatibiiity information: Information defining the lower layer characteristics of a TE or TA. high layer compatibiiity information: Information defining the higher
17、 layer characteristics of a terminal. protocol identifier: Information defining the specific protocols used by a terminal to support data transfer. progress indicator: Information supplied to indicate to the ISDN terminai that interworking has occurred. out-band parameter exchange: Information excha
18、nged via signalling channels which are not within the channel used for user information transfer. in-band parameter exchange: Information exchanged using the same information channel as that used for the user information transfer. Recommendation 1.515 (03/93) 1 ITU-T RECHN*I.SL5 (REV*L) 93 m 4Bb259L
19、 0582785 799 m I Non-wice, 64 kbws V-Serie RKS. I U I Tetmd dapted circut de Packet mode SorT TA E x30. t X25 ! TA 7 x.31 SorT 1 DE - IWF3 - InteWng function (may include: physical requirements, signailing requirements, teminai adaptation modulation, etc.) Modem Terminai adaptor with ccdec Terminai
20、adaptor with ccec, modem and supPoit of V.110 or V.120. This tmind or temind adaptation may use the Multi-Use-Bearer mce and associated procedure specified in Recanmendation (2.931. NOTES 1 IWFsmaybelocated: a) withia the network); b) separate to the network); c) within the customers premises. Ihe r
21、equiremeat for in“rW0rking between teminals may mt be inferred hm this figure. ?his figure is not exhaustive. 2 3 2 FIGURE 1L.515 Recommendation 1.515 (03/93) ITU-T RECMN*I.515 (REV* U) end-to-end, in-band as shown in Figure 3; iii) parameter exchange to select IWFs as shown in Figure 4. The in-band
22、 parameter exchange occm after the establishment of an end-to-end connection and may provide for establishment of compatibility between the endpoints, based on characteristics such as protocol, rate adaption scheme and modem type. FIGURE 2I.515 Out-band parameter exchange via D-channel I In-band I 1
23、- a) Via a transtnit network R V-Serie RECS. In-band b) Dlrect through an extended IDN Ti 3O147O-Wm a) b, 64 kbis connection type is assumed for ISDN. The extended IDN shown has a 64 kbis transmission channel (see Recommendation L23 11, however its signalling system is not compatible with that of th
24、e ISDN. FIGW 3I.515 In-band parameter exchange Recommendation 1.515 (03/93) 3 ITU-T RECMN*I-515 (REV*L) 93 m Y862591 0582787 5bL m S orT - - - 1 TE TA IWF - I - - 1 Modem V-Series Recs. CI- T1301480-93d04 Out-band In-band or ait-band L1 FIGURE 4D.515 Parameter exchange to select IWFs 2.2 Parameter e
25、xchange may occur Relationship of parameter exchange to call establishment i) prior to call establishment (call negotiation). In this case parameter exchange will occur using out-band techniques; ii) afkr call establishment, prior to information transfer. In this case parameter exchange may occur us
26、ing ethex in-band or out-band techniques; iii) during the information transfer phase of the call. In this case parameter exchange will occur using either in-band or out-band techniques. 2.2.1 Parameter exchange prior to call establishment (call negotiation) Call negotiation may be used to satisfy a
27、number of basic call requirements in ISDN. In addition, call negotiation may be necessary for interworking as described in Recommendation 1.510 (between terminals, services and networks) for: a) b) terminal section (see Recommendations 1.333, Q.931, Q.932); selection of interworking requirements whe
28、n interworking between ISDN and other dedicated networks is identified (e.g. modem type); the appropriate selection of network (ISDN or other network) functions to support the service required (e.g. use of call progress indicator); the selection of network functions when interworking between incompa
29、tible terminals is identified or when interworking of different services is required. c) d) Each of the requirements a) through d) above are necessary during the call establishment phase. Therefore, call or service negotiation mechanisms should be included within basic call establishment procedures.
30、 Further study is required. 2.2.1.1 Call negotiation types Three types of call negotiation are currently envisaged: - user to network; - network to user; - user to user. The relationship between user-to-user call negotiation and network-to-user call negotiation required further study. Call negotiati
31、on in each of the above cases may involve the forwarding of parameters to the destination, may involve forwarding of parameters on request, or may involve forward and backward negotiation to establish compatible terminal and network parameters. 4 Recommendation 1.515 (03/93) ITU-T RECMN*I-515 (REV*
32、- low layer CompatibiJity - high layer compatibility (HLC). The relationship of these information elements to parameter exchange functions is for further study. NOTE - BC, LLC, HLC are information elements defined in Recommendation Q.931. 2.2.1.3 Transfer of information The transfer of information a
33、ssociated with call negotiation is illustrated in Figure 5. U +N User-to-nehNork LLC Lower !ayer cmpatiblity N +U Network-to-user HLC High iayercompatitiliy U HU User-to-user BC Bearercapability a) The examination of LLC by the network when the IWF is not an addressed entity, is for further study. b
34、, The IWF can be distributed (see Recommendation 1510 fop defmiton of WF), When the IWFis on the customer premises, examination of aditional mformation elements to satisfy basic call requirements may be appropriate (e.g. su-FadreSs ca originating terminal changes from idle condition to busy conditio
35、n; connection enters parameters exchange phase; connection enters information transfer phase. 3.2.1.1 Voice services Refer to Recommendation G.725. 3.2.1.2 Parameter exchange mechanism for terminal adaption protocol identification Some in-band parameter exchange OPE) procedures are in existence, e.g
36、. Appendix W.110. Two circuit mo for my given instances of communication, different parameters may be required. 4.1 Numbering parameters - subscriber numbeG - sub-address; - terminal selection (see Recommendation 1.333). 4.2 Protocol control parameters Protocol control parameters can be used to iden
37、tify the protocol supported. An example is the terminal adaption protocol supported, defined in Recommendations V.110 and V.120. 4.3 DTE/DCE configuration parameters DTEDCE configuration parameters are used to identify specific transmission or communication capabilities of the called DE. The folowin
38、g is a list of such configuration parameters: - - - modem type (e.g. V-Series number): data rate (e.g. 9.6 kbids, 56 kbids); synchronization (e.g. synchronous or asynchronous): I I I - parity (odd, even or no parity); - - - - - sub-channel information. transmission mode (e.g. half or full duplex): n
39、umber of start/stop bits (e.g. 1 or 2); terminal clock source (e.g. network provided, network independent); terminal interface signals (e.g. 106, 108): Recommendation 1.515 (03/93) 7 ITU-T RECflN*I-SLS (REVs1) 93 m 4Bb259L 0582791 T92 m 4.4 Operations and maintenance parameters Operations and mainte
40、nance parameters are used to convey/monitor the status of the DTEDCE at the terminating points. Status monitored may include - - - - - terminal power (ON or OFT); terminai presence (connected or disconnected); terminai interface signals status (e.g. 106, 108); terminai clock source (e.g. network pro
41、vided, network independent); loopback status (e.g. ON or OFF). 4.5 Network parameters - bearer service; - A - echocontrol. 5 Parameter exchange for selection of IWF When an IWF is involved in a connection, parameters can be exchanged to establish compatibility. There are a variety of techniques that
42、 can be used to provide compatibility of functions in an interworking environment. These can be categorized into two types. A single stage approach in which the network automatically inserts the IWF, and a two-stage approach in which the user must provide additional information to complete the inter
43、working connection. NOTE - For examples of interworking configurations, refer to the appropriate 1.50-Series Recommendations. 5.1 Single stage In a single stage approach, the interworking function is handled automatically by the network. In order to ensure compatibility of the parameters, the follow
44、ing techniques may be used: i) ii) Parameter registration (service profile) - The DTEDCE parameters are registered with the ISDN. Parameter negotiation - Parameter negotiation may be possible between networks and end-users or between networks or between users to determine parameter compatibility whe
45、re suitable signalling exists. The signding capabilities and parameters required may vary and are for further study. For example, see Appendix W.110. iii) Default parameter identcation - The network provides an interworking function with common parameters. Any DCE must conform to the IWF common para
46、meters. iv) Parameter adaption - The interworking function recognizes and adapts to the end-users parameters. For example, for ISDN-PSTN the interworking function may adapt to the modulation standard of the modem. 5.2 Twostages In the two-stage approach, during the fust stage, the user accesses the
47、IWF and establishes the required parameters. In the second stage of the call, the IWF uses the parameters to complete the end-to-end connection. 6 Reference See Recommendation 1.500. 8 Recommendation 1.515 (03/93) ITU-T RECMN*I-515 (REV*1) 93 = Y862591 0582792 929 The protocol identification is perf
48、ormed during the following three steps after the call is placed by using the normal call establishment procedures: 1) end-to-end synchronization; 2) passing the protocol identifier (PI); 3) making a decision regarding the type of TA to use for the call. For the case of a device with a PID and one wi
49、thout a PD which interwork, a timer value (Npid) should be set in the PID for defaulting to the preferred terminal adaption protocol. Npg must be long enough to allow for initial line settling and short enough to prevent the PID from causing the terminal adaption protocol to time out and clear its call. The value of timer Npid should be set to alow for long delay connections (e.g. satellites). Refer to Figure 1.2 for the timer sequence diagram of a successful protocol identification procedure. The sequence and I acronyms in Figure 1.2 are described i
