ATT DEFINITY Communications System Generic 3 Instructions Manual

							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