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ATT DEFINITY Communications System Generic 3 Instructions Manual

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    							Generalized Route Selection (GRS)
    Issue  3   March 1996
    3-747
    The GRS capability will recognize one or more of the following five BCCs for each 
    trunk group preference in the routing pattern (DCP/DMI mode is explained later).
    :
    Table 3-58. BCC Assignment
    EndpointVoice/ 
    Data Mode BCC Comments
    Voice Terminal Voice 0
    Data Line Circuit Pack 2 2
    Voice Data Set 2 2
    Modular Processor 
    Data Module0,1,2 1,2,4 See Note
    Modular Processor
    Data Mo dule-M11 1 For ACCUNET Switched 
    56 kbps Service
    Modular Trunk 
    Data Module22
    Digital Terminal
    Data Module22
    510D Personal Terminal 2 2
    Digital Communications
    Protocol Interface 0,2,3 2,3,4 See Note
    7400A Data Mo dule  2 2
    3270T Data Module 3 3
    3270C Data Module 3 3
    3270A Data Mo dule 2,3 2,3 See Note
    Legend
    BCC Type DCP/DMI Mode
    0 Voice-Grade Data and Voice None
    1 56 kbps Data (Mode 1) 1
    2 64 kbps Data (Mode 2) 2
    3 64 kbps Data (Mode 3) 3
    4 64 kbps Data (Mode 0) 0 
    						
    							Feature Descriptions
    3-748Issue  3   March 1996 
    NOTE:
    For all endpoints, the switch automatically determines its current operating 
    mode when the data mo dule originates.  Before any call is originated, the 
    default is Mode 2.
    Since call origination from a data mo dule d etermines the mo de to be used 
    on the call, it is recommended that the data module user press the 
    Originate/Disconnect button once after changing data options. This way, 
    the right mo de is sure to be assigned to the next call.
    ISDN-PRI BCC Parameters
    The ISDN-PRI BCC Parameters are:
    nInformation Transfer Capability
    nLow-Layer Compatibility
    nDCP/DMI Mod e
    Information Transfer Capability
    The information to be transferred (or type of call) requires different transmission 
    facilities. For example, transmission needs for voice calls and data calls are 
    generally different. Voice and voice-grade data calls can be sent over analog 
    trunks, while high speed data calls require digital trunks.
    The Information Transfer Capability parameter in the Bearer Capability 
    Information Element (BC IE) and Low-Layer Information Element (LLC IE) have 
    the following four values:
    nVoice (speech)
    nVoice-grade data (3.1 kHz transmission)
    nUnrestricted digital transmission
    nRestricted digital transmission.
    With data calls, the switch distinguishes the information transfer capability 
    (restricted or unrestricted) of the originating data end p oint (trunk or terminal), 
    and then uses the  information transfer capability of the data endpoint to route the 
    call onto the  appropriate facility. For BRI and PRI originating  data endpoints,  the 
    information transfer c a pability is c ontained in the ISDN SETUP m e s sa g e.  Fo r 
    non-ISDN data endpoints, the switch uses the information transfer capability 
    specified by the system administrator. The default for the information transfer 
    capability of an endpoint is 
    restricted. The  system  administrator  may  change the 
    information transfer c a pability to restricted or unrestricted for each non-ISDN 
    originating endpoint. 
    						
    							Generalized Route Selection (GRS)
    Issue  3   March 1996
    3-749
    More than one Information Transfer Capability can be supported by one BCC. 
    Low-Layer Compatibility
    The low-layer comp atibility information element provides remote compatibility 
    checking. This element is used with the bearer capability element and 
    determines the mode of the originating caller. The low-layer compatibility 
    information element is optional and sent only in case of data calls.
    NOTE:
    DCP Mode 0 does not send  an LLC IE.
    DCP/DMI Mode
    The Digital Communications Protocol (DCP) and the Digital Mulitplexed Interface 
    (DMI) mo des are d ata parameters of the originating data facility. These modes 
    are not a pplicable to voice.
    The mode values (0, 1, 2, and 3) are administered for d ata and Alternate 
    Voice/Date (AVD) non-ISDN-PRI trunk groups. These mode values determine the 
    BCC of the trunk groups.
    1. Use BCC 4 for an unknown data mode that re quires a 64 kbps channel.
    Table 3-59. Assignment of BCC Based on Information Transfer 
    Capability
    DCP/DMI 
    MODEInformation Transfer 
    Capability BCC Comments
     —  Speech 3.1 kHz 0 Used for Voice/ Voice 
    Grade Data.
    M1 Unrestricted/ 
    Restricted Digital1 Used for Mode 1 Data (56 
    kbps).
    M2 Unrestricted/ 
    Restricted Digital2 Used for Mode 2 Data 
    (async data speed up to 
    19.2 k b ps).
    M3 Unrestricted/ 
    Restricted Digital3 Used for Mode 3 Data (64 
    kbps).
    M0 Unrestricted/ 
    Restricted Digital4 Used for Mode 0 Data
    1 (64 
    k bps clear channel). 
    						
    							Feature Descriptions
    3-750Issue  3   March 1996 
    Determination of BCC at Tandeming or 
    Terminating System
    Determination of the BCC for an incoming call from a ISDN-PRI trunk to a tandem 
    or terminating switch is based on the BCC parameters received on the signaling 
    channel (D-channel) of the trunk. This includes the ITC (restricted or unrestricted) 
    if the call is a data call.
    Determination of the BCC for an incoming call from a non-PRI trunk will be as 
    follows:
    nIf the incoming trunk is a voice trunk, then the BCC is defaulted to 0.
    nIf the incoming trunk is a data, AVD, or RBAVD (robbed-b it AVD) trunk, 
    then the BCC and ITC are administrable.
    GRS Operation
    The AAR/ARS routing pattern will contain an indication  for each trunk group 
    preference showing which BCC or BCCs can use that trunk group.   A trunk 
    group preference may have more than one BCC.
    GRS uses a 
    look-ahead algorithm when determining which preference in a 
    routing  pattern to choose. GRS first attempts to find an exact match between the 
    originator’s BCC and the corresponding allowed BCC for any of the  preferences 
    in the routing pattern. Therefore, if preference 1 does not have an exact match 
    (even though there are available compatible members in preference 1), it will be 
    skip p ed over if a subsequent preference in the same pattern has an allowed 
    BCC that exactly matches the originator’s BCC.
    After matching the BCCs, G3i will then match the ITCs. The originator’s ITC is 
    matched to the route preference ITC. Unrestricted (unre) matches on ‘‘unr’’ or 
    ‘‘both.’’ Restricted  (rest)  matches on ‘‘rest’’ or ‘‘both.’’
    NOTE:
    ITC matching only ap p lies to data calls (BCC 1 through 4).
    As an example of how GRS chooses a trunk group preference, assume 
    preference 1 in a pattern has BCC 0 and BCC 2 set to yes, while preference 2 
    has BCC 1, BCC 3, and BCC 4 set to yes. A voice or Mode 2 d ata c all accessing 
    this pattern will use the first preference, while a Mode 1, Mo de 3, or Mode 0 data 
    call will use the second, independent of the availability of trunks in the first 
    preference.
    When an exact match is not found in any of the routing p attern preferences, calls 
    are treated as follows:
    nCalls With an Originating BCC of 0 
    						
    							Generalized Route Selection (GRS)
    Issue  3   March 1996
    3-751
    A BCC 0 originated call (such as voice or analog modem) will not b e 
    denied routing by GRS, even if the routing pattern lacks a preference with 
    BCC 0 set to yes. This allows the user to use voice transfer to data when 
    making a data call, without the need for data preindication.
    If a BCC 0 originated  call accesses a routing pattern for which no 
    preference has BCC 0 set to yes, then GRS will choose a preference with 
    BCC 2 set to yes, if one exists.  If none exists, the next preferred ord er 
    would be a preference with BCC 1 set to yes, followed by BCC 3, and 
    finally, BCC 4.  Since each preference must allow at least one BCC to be 
    passed, a BCC 0 (voice) originated call will never b e blocked by GRS.  
    The call is of course still subject to other restrictions, such as FRL 
    restrictions. The ITC d oes not help select a preference.
    Since BCC 0 (voice) has no ITC, the switch selects an ITC from the routing 
    pattern when a BCC 0 call is being routed as a data call. Table 3-60 
    shows how the ITC codepoint in the Bearer Capability IE is determined.
    nCalls With an Originating BCC of 2
    If a BCC 2 originated  call accesses a routing pattern for which no 
    preference has BCC 2 set to yes, then GRS will choose a preference with 
    BCC 0 set to yes, if one exists.  If none exists, the call will be blocked with 
    intercept treatment.
    nCalls With an Originating BCC of 1, 3, or 4
    A DCP/DMI Mode 0 (BCC 4), Mo de 1 (BCC 1), or Mo de 3 (BCC 3) 
    originated call requires an exact match on at least one preference in a 
    routing pattern in order for GRS to allow the c all to c omplete. For examp le, 
    a Mode 1 originated call will complete only if the accessed routing  pattern 
    has a preference with BCC 1 set to yes. The ITCs must also match.
    When an ISDN-PRI trunk group preference is accessed, the BCC information is 
    encoded and sent in the outg oing ISDN SETUP m e ss a g e to  the d istant-end as 
    shown below. The BCC information sent to the far end is imp ortant, because the 
    Table 3-60. Determination of ITC Codepoint
    Originating
    Endpoint’s 
    ITC Routing Preference’s ITCITC 
    codepoint 
    in BC IE
    restricted unrestrictedboth 
    endpointboth 
    unrestricted
    voice x restricted
    voice x unrestricted
    voice x unrestricted
    voice x unrestricted 
    						
    							Feature Descriptions
    3-752Issue  3   March 1996 
    BCC information that the far-end receives in the SETUP message will become the 
    originating BCC for the far-end’s incoming trunk call.
    nIf an exact match of the originator’s BCC and ITC has been found,  then 
    that Bearer Cap a bility is encoded and sent in the ISDN SETUP  message 
    to the far-end. If the call is a data call, the system uses the ITC of the 
    routing p attern to encode the SETUP message as shown in Table 3-61.
    nIf an exact match is not found, but the call is allowed to proceed, then the 
    BCC encoded in the SETUP message sent to the far-end is that of the 
    routing p attern. For example, if a BCC 2 (for example, DTDM) end p oint 
    originates a call that accesses a pattern that has one preference with only 
    BCC 0 set to yes, then the switch automatically inserts a modem pool for 
    this call. In effect, the modem pool is converting BCC 2 to BCC 0.   The 
    far-end cannot distinguish this call from a BCC 0 originated call that has 
    no modem pool inserted. Therefore, BCC 0 is sent in the SETUP message. 
    This may in turn determine routing decisions by the far-end. Ad ditional 
    routing d ecisions are ma de as shown in the following tables.
    1. A voice originated call without d ata preindication that is routed to a routing
    pattern with data preferences only.
    Table 3-61. Encoding of Setup message
    Originating
    Endpoint’s 
    ITCRouting Preference’s ITC
    ITC 
    codepoint in 
    BC IE restricted unrestrictedboth 
    endpointboth 
    unrestricted
    restricted x restricted
    restricted x restricted
    restricted x unrestricted
    unrestricted x unrestricted
    unrestricted x unrestricted
    unrestricted x unrestricted
    voice
    1x restricted
    voice x unrestricted
    voice x unrestricted
    voice x unrestricted 
    						
    							Generalized Route Selection (GRS)
    Issue  3   March 1996
    3-753
    BCC and ITC Determination on Calls from 
    Endpoints to ISDN-PRI Trunks
    Table 3-62. Calls from Endpoint to ISDN-PRI Trunks
    Originating Chosen BCC from the Routing Pattern
    BCC BCC 0 BCC 1 BCC 2 BCC 3 BCC 4
    BC C 0 P PT PT PT PT
    BCC 1 BPBBB
    BCC 2 PMBPBB
    BCC 3 BBBPB
    BCC 4 BBBBP
    Legend
    B Block the call with intercept treatment
    P Allow the call and send the originating en d point’s BCC in the 
    SETUP m essage.  Use the ITC as shown in the following 
    table
    PT Allow the call and send the BCC and ITC chosen from the 
    routing pattern in the SETUP message
    PM Insert a pooled modem for the call and send the BCC and 
    ITC chosen from the routing pattern in the SETUP message 
    						
    							Feature Descriptions
    3-754Issue  3   March 1996 
    If BCC 1, 2, 3, or 4 is chosen from the preceding table, the following table is used 
    to d etermine the a p propriate ITC.
    Table 3-63. Calls from Endpoints to ISDN-PRI Trunks
    Originating Chosen ITC from the Routing Pattern
    ITC unr rest both endpt both unr
    unrPBPPU
    restBPPPU
    Legend
    B Block the call with interc ept treatment
    P Allow the call and send the originating endpoint’s ITC in the 
    SETUP message
    PU Allow the call and send ‘‘unrestricted’’ in the SETUP 
    message 
    						
    							Generalized Route Selection (GRS)
    Issue  3   March 1996
    3-755
    BCC and ITC Determination on Calls from 
    Trunks to ISDN-PRI
    Table 3-64. Calls from Trunks to ISDN-PRI Trunks
    Originating Chosen BCC from the Routing Pattern
    BCC BCC 0 BCC 1 BCC 2 BCC 3 BCC 4
    B C C  0 P PT PT PT P T
    BCC 1 BPBBB
    BCC 2 PTBPBB
    BCC 3 BBBPB
    BCC 4 BBBBP
    Legend
    B Block the call with interc ept treatment
    P Allow the call and send the incoming trunk’s BCC in the 
    SETUP message. Use the ITC as shown in the following 
    table
    PT Allow the call and send the BCC and ITC chosen from the 
    routing pattern in the SETUP me ss a ge 
    						
    							Feature Descriptions
    3-756Issue  3   March 1996 
    If BCC 1, 2, 3, or 4 is chosen from the preceding table, the following table is used 
    to d etermine the a p propriate ITC.
    The system does not insert pooled modem for any interworking 
    trunk-to-ISDN-PRI trunk calls. The BCC and ITC of an incoming trunk is 
    determined as follows:
    nISDN-PRI Trunk BCC and ITC are in the received SETUP m e s sa g e
    nAVD Trunk BCC and ITC are the BCC and ITC values administered on the  
    trunk group form
    nRBAVD Trunk BCC and ITC are the BCC and ITC values ad ministered on 
    the  trunk group form
    nData Trunk BCC and ITC are the BCC and ITC values a dministered on the  
    trunk group form
    nVoi ce T ru nk BCC is 0.
    Table 3-65. Calls from Trunks to ISDN-PRI Trunks
    Originating Chosen ITC from the Routing Pattern
    ITC unr rest both endpt both unr
    unr P B P PU
    rest B P P PU
    Legend
    B Block the call with interc ept treatment
    P Allow the call and send the incoming trunk’s ITC in the 
    SETUP message
    PU Allow the call and send ‘‘unrestricted’’ in the SETUP 
    message 
    						
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