1、INTERNATIONAL TELECOMMUNICATION UNION)45G134 1 TELECOMMUNICATIONSTANDARDIZATION SECTOROF ITU$)4!,G0G0%8#(!.%3$)4!,G0G0%8#(!.%G0G0#/%#4)/.3 3).!,).G0G0!.$G0G0!.#),!29G0G0s1, s2, s4, s5: signalling information different from the signalling associated with customer terminals; packet switching interwork
2、ing functions may be provided at other exchanges in an ISDN or at the pointof access to a separate packet switched network.2.2.3 Type 1 exchange connection (Figure 1/Q.522)This connection is sued to transport telephony and associated voice services.This connection is characterized by (see Table 2/I.
3、340, A 4, A 5, A 7 and A 8): Information transfer attributesmode: circuitrate: 64 kbit/scapability: speech 3.1 kHz audioestablishment: switched semi-permanentsymmetry: bidirectional symmetricconfiguration: point-to-point uniformstructure: 8 kHz integrity Access attributes (Table 1/Q.522)Access attri
4、butes User access Network accessAccess channel and rateInformation B/64 Digital circuit with access to analogue/digitalswitched networkSignalling D/1664 Digital circuit (s1)Access protocola)Layer 1 For further study Q.702, othersLayer 2 I.441 Q.703, othersLayer 3 I.451 Q.704, Q.714, Q.764, othersa)O
5、nly for switched services.TABLE 1/Q.522Fascicle IV.5 - Rec. Q.522 3 Other attributesFor further study.FIGURE 1/Q.522Type I exchange connection2.2.4 Type II exchange connection (Figure 2/Q.522)This connection is used to transport circuit switched services such as data, telephony, multiple subrateinfo
6、rmation streams multiplexed into 64 kbit/s by the user, transparent access to a PSPDN (see 5.2.2).This connection is characterized by: Information transfer attributes (see Table 2/I.340, A 1 and A 2)mode: circuitrate: 64 kbit/scapability: unrestricted digital informationestablishment: switched semi-
7、permanentsymmetry: bidirectional symmetricconfiguration: point-to-point uniformstructure: 8 kHz integrity Access attributes (Table 2/Q.522)TABLE 2/Q.522Access attributes User access Network accessAccess channel and rateInformation B/64 Digital circuit with access to analogue/digitalswitched networkS
8、ignalling D/16-64 Digital circuit (s1)Access protocol See type I (For signalling only)a)See type I (For signalling access to digitalswitched network)a)a)Further study is required for information transfer protocol or access to PSPDN.4 Fascicle IV.5 - Rec. Q.522 Other attributesFor further study.FIGUR
9、E 2/Q.522Type II exchange connection2.2.5 Type III exchange connection (Figure 3/Q.522)This is a connection used to transport packetized data information between an information channel on a digitalsubscriber access and a 64 kbit/s digital circuit which has an access to:a) a remote ISDN Packet Handli
10、ng Functional Grouping;b) a remote ISDN Packet Switching Interworking Functional Grouping;c) a public packet network (see 5.2.3).This connection is characterized by: Information transfer attributes (see Table 3/Q.522)(see Table 2/I.340, A 10 and A 11)TABLE 3/Q.522Access attributes Option a) Options
11、b) and c)Mode Circuit PacketRate 64 kbit/s (further study) 64 kbit/s (further study)Capability Unrestricted digital information Unrestricted digital informationEstablishment Switched semi-permanent Switched semi-permanentSymmetry Bidirectional symmetric Bidirectional symmetricConfiguration Point-to-
12、point Point-to-pointStructure 8 kHz Service data unit integrityFascicle IV.5 - Rec. Q.522 5 Access attributes (Table 4/Q.522) Other attributesFor further study.FGURE 3a/Q.522Type III exchange connection option a)TABLE 4/Q.522Access attributes User access Network accessAccess channel and rateInformat
13、ionOptions a), b), c) B/Further study 64 kbit/s digital circuita)Signalling a), b), c) D/16-64 64 kbit/s digital circuita)Access protocolOptions a), b) For further study For further studyOption c) For further study X.75- X.25a)Information and signalling may be carried by the same circuit (in-band si
14、gnalling).6 Fascicle IV.5 - Rec. Q.522FIGURE 3b/Q.522Type III exchange conenction option b)Note 1 These links may pass through the 64 kbit/s circuit switch. This requires further study.Note 2 s2, optional.FIGURE 3c/Q.522Type III exchange connection option c)Fascicle IV.5 - Rec. Q.522 72.2.6 Type IV
15、exchange connection (Figure 4/Q.522)This connection is used to transport message type data, for example packetized data messages or teleactioninformation messages (see 5.2.4).It consists of a message/packet type connection via a D channel on a digital subscriber access to an access portto either:a)
16、a remote ISDN Interworking Functional Grouping; orb) a public packet network.This connection is characterized by: Information transfer attributes(see Table 2/I.340).See type III, options b) and c). Access attributes (Table 5/Q.522). Other attributesFor further study.TABLE 5/Q.522Access attributes Us
17、er access Network accessAccess channel and rateInformation and signallingOptions a) and b) D/For further studya)64 kbit/s digital circuitb)Access protocolOption a) For further study For further studyOption a) For further study X.75 - X.25a)Signalling in-band or out-band.b)Signalling in-band or out-b
18、and for option a), or in-band for option b).8 Fascicle IV.5 - Rec. Q.522a)s, s4and s5are only applicable when all signalling required is not contained in the p information.b)Signalling in-band or out-band for option a), or in-band for option b).FIGURE 4/Q.522Type IV exchange connection2.3 Functions
19、associated with attributes shown in 2.2The following information is to clarify which functions may be associated with the attributes shown on thetypes I-IV exchange connection diagrams described in 2.2.2.3.1 Layer 1 functions (see Note in 2.3.4)This functional grouping includes: digital line/exchang
20、e termination interface functions.2.3.2 Layer 2 functions (see Note in 2.3.4)This functional grouping includes: layer 2 D-channel protocol handling (LAP D)2.3.3 64 kbit/s circuit switching functionsThis functional grouping includes: 64 kbit/s switching stage(s).2.3.4 Signalling handling and exchange
21、 control functionsThis functional grouping may include: layer 3 D-channel protocol for signalling (see Note); functions related to circuit switched connection control;Fascicle IV.5 - Rec. Q.522 9 signalling functions for common channel signalling; signalling interfaces with “packet handling function
22、”; functions related to packet switched connections; signalling interface with “packet switching interworking function”.Note - The term “layer” refers to Open Systems Interconnection as applied to CCITT signalling systems asdefined by Recommendations X.200 and I.112.2.3.5 Packet switching interworki
23、ng functionsThis functional grouping may include: signalling interface with “packet handling function” and “signalling handling and exchange controlfunction” allowing call packets to be routed to/from the appropriate subscriber terminals; routing functions; functions such as compatibility checking;
24、protocol conversion; numbering interworking; control function (see Note in 2.3.6).2.3.6 Packets handling functionThis functional grouping may include: layer 3 D-channel protocol for packet calls; packet level multiplexing for outgoing calls; packet level demultiplexing for incoming calls; signalling
25、 interface with the “signalling handling function” and subscriber terminals via layer 1 and 2functional block; control functions for packet switched connections (see Note); some or all the functions associated with packet switching (e.g., internal packet calls).Note - Clarification of control functi
26、on would need further study.In the case where the packet switching interworking function is not present in the local exchange, the localexchange contains the minimum functions necessary to enable it to communicate with the packet switching interworkingfunction. The protocols to carry out this minimu
27、m function require further study.2.4 Bit rate of a connection through an exchange2.4.1 Basic bit rate for circuit switched connectionsThe exchange should be able to make circuit switched connections between channel timeslots with the basicbit rate of 64 kbit/s. The channel timeslots to be connected
28、are contained in primary or higher order frame structuresappearing at the digital interfaces of the exchange or derived from analogue channels appearing at the analogueinterfaces, or from individual digital interfaces for subscriber access.Switching at rates other than 64 kbit/s is for further study
29、.2.4.2 Basic bit rate for message/packet switched connections Type IVThe bit rate of a message/packet connection Type IV will depend on a number of factors including the bit rateof the subscriber terminal equipment, the bit rate of the D channel and the bit rate capacity of the connection to theappr
30、opriate network.2.5 Services offered at bit rates less than 64 kbit/sServices requiring less than 64 kbit/s for a connection should be switched as 64 kbit/s connections.10 Fascicle IV.5 - Rec. Q.5222.6 Services offered at bit rates greater than 64 kbit/s2.6.1 GeneralServices requiring more than 64 k
31、bit/s for a connection are through-connected as a multiple of 64 kbit/sconnections. They are called multi-slot connections.The exchange may be required to establish the following types of multi-slot connections (see RecommendationI.340): 2 64 kbit/s connections; 6 64 kbit/s connections to provide a
32、H0channel; 24 64 kbit/s connections to provide a H11channel; 30 64 kbit/s connections to provide a H12 channel.It should be noted that an n 64 kbit/s connection can seriously affect the blocking probability of an exchangeand the network, particularly if all n timeslots are routed in a defined order
33、in the same multiplex. The ability to handlemulti-slot traffic will be influenced by the traffic loading of the exchange at any instant and the number of circuitsavailable on the required route.2.6.2 2 64 kbit/s connectionsThis connection type is characterized by the following attributes (see Recomm
34、endation I.340).The attributes are for further study.A 2 64 kbit/s connection is established in response to signalling information received on the subscriber lineor on an inter-exchange link.The exchange should maintain restricted differential time delay between the two timeslots involved in theconn
35、ection. The precise definition of ”restricted differential time delay” is still to be formulated, but the intention is toensure that the time delay between the individual slots forming a 2 64 kbit/s connection is not excessive, for exampleas could occur if the two channels were routed out of the exc
36、hange on diverse physical routings.The exchange aspects of meeting this requirement require further study, but will include the need for theexchange to be capable of recognizing the signalling information on incoming inter-exchange circuits/subscriberaccesses which indicates that there is an associa
37、tion between two incoming 64 kbit/s channels and to ensure that the twochannels are handled by the exchange in a uniform manner.2.6.3 Switching of 6 64 kbit/s connections (H0channel)The 64 kbit/s timeslots which form an H0channel are transmitted over the same primary multiplex systemwithin the same
38、frame. This is valid for both the subscriber line and the inter-exchange links.The requirement for 6 64 kbit/s connections can be satisfied by establishing 6 separate 64 kbit/ssemi-permanent connections, each of which would be set up to preserve the sequence with the other slots forming the6 64 kbit
39、/s connection.2.6.4 Switching of 24 or 30 64 kbit/s connection (H1channels)This is for further study.2.7 Mode of establishment2.7.1 Circuit switched connections, Type I, Type II and Type III option a)Circuit switched connections are set up at any time on demand in response to signalling information
40、receivedfrom subscribers, other exchanges or other networks.2.7.2 Packet switched connections, Type III options b) and c)For further study.2.7.3 Message/packet switched connections, Type IVThese connections are set up on demand subject to any D channel priority/flow control restrictions that may bea
41、pplicable.Fascicle IV.5 - Rec. Q.522 112.7.4 Semi-permanent connectionsThe exchange should have the capability of establishing semi-permanent connections which pass through theexchange switching network.Other features of semi-permanent connections, e.g. grade of service, the need for an out-slot sig
42、nalling channelassociated with the connection, etc. are for further study.2.8 Bit sequence independenceSee Recommendation Q.554.2.9 Bit integritySee Recommendation Q.554.2.10 Octet sequence integritySee Recommendation Q.9.2.11 8 kHz (structure) integritySee Recommendation I.140.2.12 Bit patterns gen
43、erated by the exchange in idle channel timeslotsAt interfaces A and B, the following patterns are recommended for the idle condition, where the left-most digitis the polarity digit.01111111 for 1544 kbit/s systems01010100 for 2048 and 8448 kbit/s systems.At other interfaces the bit pattern generated
44、 in idle channel timeslots is for further study.The patterns should not be used as an indication of the idle or barred conditions of a channel since thisinformation should be derived from the control or signalling functions.Note - These patterns are slightly different from the quiet code produced by
45、 external test equipment and usedas an auxiliary signal for noise and crosstalk measurements on digital exchanges (see Recommendations Q.551, 1.2.3.1, Q.552, 2, 2.2.3, 3.1.4 and Q.553, 2.1.1.2, 3.1.4).2.13 Error performanceSee Recommendation Q.554.2.14 In-call rearrangementIn-call rearrangement is t
46、he rearrangement by the exchange of the established connections across theswitchblock in a more efficient manner.When it is provided, it is essential that the requirements for error performance, Quality of Service, etc. be met(see Recommendation Q.543).2.15 Transmission performance characteristicsSe
47、e Recommendations Q.551 to Q.554.12 Fascicle IV.5 - Rec. Q.5223 Signalling and D-channel handling3.1 GeneralThe exchange should be capable of interworking with other exchanges using signalling systems indicated inRecommendation Q.7, and for local or combined exchanges with user equipment on digital
48、access lines (e.g., terminalsand PABXs) using the signalling procedures in Recommendations I.430, I.431, and Q.920 (I.440), Q.930 (I.450)-Seriesof Recommendations.For a local or combined exchange interworking with user terminals or analogue subscriber access lines shouldbe accomplished using nationa
49、lly recommended signalling procedures.64 kbit/s signalling channels entering the exchange via a multiplex structure may be connected through theexchange as semi-permanent channels.3.2 Signalling associated with exchange connections Types I-IVThis section applies to local or combined exchanges only.3.2.1 GeneralDetails of the exchange connections Types I-IV are given in 5.For internal and originating connections, the call set up signalling information will be received from thesu
