Lucent Technologies Ds1/Cept1/Isdn Pri Reference Manual

							DEFINITY Communications System Generic 2.2 and Generic 3 V2 
DS1/CEPT1/ISDN PRI Reference  
555-025-107  Issue 1
July 1993
Layers 2 and 3 
Page 5-5 ISDN PRI Layer 2 
5
G2.2 Layer 2 Termination
G2.2 trad itional mod ules use a sp ec ial DS1 b oard , the ANN35, to terminate ISDN 
PRI layer 2 sig naling . Firmware on this b oard  d oes all the layer 2 p roc essing . 
Bec ause this b oard  is d esig ned  sp ec ific ally to p roc ess ISDN PRI layer 2 
sig naling , however, it c annot b e used  for DS1 b it oriented  sig naling  p rotoc ols. 
Thus, the ANN35 is c alled  an ISDN PRI board . When a DS1 fac ility c onnec ted  to 
the ANN35 c ontains an ISDN D c hannel (a fac ility assoc iated  sig naling  
arrang ement), the 24th c hannel is p roc essed  sep arately b y the b oard . The other 
23 c hannels are p ut on the PCM b us (the G2.2 trad itional mod ule name for a 
TDM b us) to b e switc hed  to their d estinations. The ANN35 terminates the LAPD 
p rotoc ol on the 24th c hannel and p uts the remaining data on the I/O b us for 
p roc essing by the mod ule p roc essor and  c ommon c ontrol p roc essor.
Universal mod ules, on the other hand , use the TN767, whic h d oes not p erform 
any layer 2 p roc essing . If the DS1 fac ility c onnec ted  to the TN767 c ontains an 
ISDN PRI D c hannel, a TN555 pac ket ad junc t b oard  must b e p resent in the 
ad jac ent slot. In this c ase, the entire 24 c hannels inc oming  to the DS1 b oard  are 
routed  to the TN555 via a short c ab le from the TN767 to the TN555. The TN555 
then plac es the 23 B c hannels on the TDM b us to be switc hed  to their 
d estinations. The TN555 relays the LAPD frames of the D c hannel d irec tly to the 
LAN b us and  ultimately to the d ownload ab le mod ule p roc essor, whic h terminates 
the LAPD p rotoc ol and  send s the remaining  d ata to the c ommon c ontrol 
p rocessor.
No spec ial ad ministration is required  in G2.2 to terminate the layer 2 ISDN PRI 
p rotoc ol.
G3iV2 Layer 2 Termination
In G3iV2, ad ministration must b e p erformed  to set up  c ommunic ation b etween 
t h e  SPE a n d  t h e  PI  b o a rd .  Th i s  a l lo w s t h e  l a y e r  2 - t e r m in a t i n g  b o a rd ,  t h e  
p ro c e s s o r  in t e r f a c e ,  t o  d e li ve r t h e  d a t a  o n  t h e  D  c h a n n e l  t o  t h e  SPE,  w h ic h  t h e n  
interp rets the d ata using  the level 3 ISDN PRI p rotoc ol. This op erates as follows:
nThe DS1/CEPT1 b it stream enters the DS1/CEPT1 c irc uit p ac k.
nThe DS1/CEPT1 c irc uit pac k terminates the layer 1 p rotoc ol and  relays 
these b its to the TDM b us. The ad ministration for this is all d one on the 
DS1 circuit pack form.
nThe b it stream on all timeslots exc ep t for timeslot 24 (DS1) or 16 (CEPT1), 
whic h is the ISDN PRI D c hannel, remain on the TDM b us and  are 
switc hed  to their destinations (p orts). The D c hannel b its, however, are 
routed  to the p roc essor interfac e board . This routing  is d one by setting  up  
a c onnec tion b etween the D c hannel on the DS1/CEPT1 c irc uit p ac k and  a 
p ort on the p roc essor interfac e b oard . To set up  this c onnec tion, you d o 
the following :
— Ad minister the signaling  g roup  form for the d esired D c hannel. 
						

							DEFINITY Communications System Generic 2.2 and Generic 3 V2 
DS1/CEPT1/ISDN PRI Reference  
555-025-107  Issue 1
July 1993
Layers 2 and 3 
Page 5-6 ISDN PRI Layer 2 
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— Add a data module of the type procr-intf
, and  its extension and 
assig n it to the p ort (p hysic al c hannel) on the PI b oard (s) (p orts 1- 
8) to whic h you want the D c hannel to c ommunic ate.
— Use the c ommand change communication-interface links
 to 
d isp lay the interfac e links form. Ad minister the link c orresp ond ing 
to the p hysic al c hannel of the p roc essor interfac e data mod ule. By 
entering  the extension of the p roc essor interfac e d ata mod ule and  
the b oard  ad d ress of the DS1/CEPT1 b oard  c ontaining  the D 
c hannel, a p ath is set up  over whic h the PI b oard  and  the D c hannel 
c an c ommunic ate. When enab led , the two b oard s will 
c ommunic ate.
— Before enab ling the c onnec tion, you must ad minister the link in the 
p roc essor c hannel assignment form. This tells the system that the 
link is being used for ISDN applications.
nThe D c hannel from the DS1/CEPT1 b oard  is now c ommunic ating  with a 
p ort on the PI b oard . The PI b oard  then terminates the LAPD p rotoc ol of 
the D c hannel and  send s the information, via an internal protoc ol, to the 
p rocessor for layer 3 termination.
nThe ad ministration p erformed  in the p roc essor c hannel assig nments form 
and  the sig naling  g roup  form p rovid e the nec essary information to the SPE 
for the layer 3 p rotoc ol to be p roc essed.
G3rV2 Layer 2 Termination
In G3rV2, it is not nec essary to set up  a c onnec tion b etween the DS1/CEPT1 
board and the layer 2-terminating board because the D channel is put directly 
onto the LAN b us b y the TN464C. The ad d ress field  of the LAPD frames of the D 
c hannel are c hang ed  to an internal ad d ress and  relayed to the p ac ket interfac e 
b oard , whic h then terminates the layer 2 p rotoc ol. The p ac ket interfac e uses the 
LAPD ad dress to know for whic h DS1/CEPT1 b oard  the D c hannel is sig naling . 
Unlike the proc essor interfac e board  in the G3iV2, whic h was orig inally d esig ned 
for BX.25 ap p lic ations and  retrofitted  (so to sp eak) for ISDN PRI op eration, the 
p ac ket interfac e was d esig ned  to und erstand ISDN PRI c ap ab ilities. Thus, it is 
not nec essary to assig n a p roc essor c hannel to tell it that it is an ISDN PRI 
ap plic ation. The p ac ket interfac e only need s the information sup p lied  b y the 
sig naling  g roup  form to c orrec tly supp ly the D c hannel information to the ISDN 
PRI layer 3 software in the SPE.
Layer 2 User-Network and Master-Slave Protocol
The LAPD p rotoc ol used  in DEFINITY G2.2 and  G3V2 ISDN PRI req uires one sid e 
to b e id entified as a master and  the other sid e as a slave. A c ommand /resp onse 
b it (CR b it) is set to 0 or 1 d epend ing  on whether the c ommand /resp onse is 
sent/rec eived b y the master sid e or the slave sid e. If both sid es ac t as master or 
b oth sid es ac t as slave, a layer 2 c onnec tion b etween the two end s c annot b e 
mad e. In G2.2 and in the G3V2 user-network p rotoc ol, the master sid e is c alled   
						

							DEFINITY Communications System Generic 2.2 and Generic 3 V2 
DS1/CEPT1/ISDN PRI Reference  
555-025-107  Issue 1
July 1993
Layers 2 and 3 
Page 5-7 ISDN PRI Layer 2 
5
the network sid e and  the slave sid e is c alled  the user sid e. If the ECMA layer 3 
p eer p rotoc ol is used , the layer 2 terms are master and  slave in G3V2. In all 
DEFINITY systems ad ministration exists to c ontrol the master-slave/user-network 
status of the interfac e. In G2.2, you ad minister the layer 2 user-network protoc ol 
in p roc ed ure 262, word  1, field  6.
In G3V2 systems, when you ad minister the user-network p rotoc ol, b oth the layer 
2 and  layer 3 user/network id entific ation is administered . For examp le, in a G3V2 
system, if you ad minister the system as user, it is user at b oth layer 2 and  layer 3. 
For information on the layer 3 user-network p rotoc ol, see the sec tion 
‘‘User-Network and Peer Protoc ols’’
 later in this c hap ter.
The following  list exp lains the administration for the layer 2 user-network and  
master-slave p rotocols for G3V2 systems:
nIf ad ministered as host
 in the Connect
 field of the DS1 c irc uit p ac k form, 
the G3V2 is the network sid e at layers 2 and  3. The c onnec t field  ind ic ates 
what the far end  system is.
nIf ad ministered  as network
 in the Connect
 field , the G3V2 system is the 
user sid e at layers 2 and 3. Connec ted  to network usually means trunks on 
this interfac e are c onnec ted  to the p ub lic  network, whic h b y c onvention is 
always the network sid e.
nIf the system is ad ministered  as pbx
 in the Connect
 field , the other end is 
another PBX. This req uires one sid e to b e d efined  as user and  the other 
side d efined  as network. Thus, in this c ase, another field , Interfac e 
ap pears. This field  id entifies whether the near end  system (the one b eing  
ad ministered ) is network or user. The system must b e administered  as 
either network
 or user
 in this field .
Beg inning  with G3V2, the Europ ean Comp uter Manufac turers (ECMA) stand ard 
for PBX-PBX interfac es, whic h is a p eer p rotoc ol as op p osed  to a user-network 
protoc ol, has been added as an option. Thus, you can administer a G3V2 to use 
a user-network p rotoc ol or a p eer protoc ol. The following  list explains this 
administration:
nIf ad ministered as host
 in the Connect
 field of the DS1 c irc uit p ac k form, 
the G3V2 is the network sid e at layers 2 and  3. The c onnec t field  ind ic ates 
what the far end  system is.
nIf ad ministered  as network
 in the Connect
 field , the G3V2 system is the 
user sid e at layers 2 and 3. Connec ted  to network usually means trunks on 
this interfac e are c onnec ted  to the p ub lic  network, whic h b y c onvention is 
always the network sid e.
nIf the system is ad ministered  as pbx
 in the Connect
 field , the other end  is 
another PBX. In this c ase, you have a c hoic e of whether you want to 
ad minister a user-network p rotoc ol or a peer protoc ol. If you c hoose either 
peer-master
 or peer-slave
, the system will op erate with the ECMA 
p eer p rotoc ol. If you c hoose peer-master
, the layer 2 op eration is the 
same as if you ad minister network
. Similarly, if you administer  
						

							DEFINITY Communications System Generic 2.2 and Generic 3 V2 
DS1/CEPT1/ISDN PRI Reference  
555-025-107  Issue 1
July 1993
Layers 2 and 3 
Page 5-8 ISDN PRI Layer 3 
5
peer-slave
, the layer 2 p rotoc ol op erates the same as user
. See the 
sec tion ‘‘User-Network and  Peer Protoc ols’’
 for further exp lanation on the 
layer 3 p rotoc ol.
NOTE:
When a G3V2 DS1/CEPT1 interfac e ad ministered  with a user-network 
p rotoc ol is c onnec ted  to a G2.2 interfac e, the G3V2 interfac e must b e 
administered as network and the G2.2 interfac e as user. This is because 
the user-network administration on the G2.2 is only imp lemented for layer 2. 
The layer 3 user-network relationship  in G2.2 is user b y d efault, whic h 
means the layer 3 user/network identific ation must be network in the G3V2, 
whic h in turn means the layer 2 user/network is also network, whic h in turn 
means the layer 2 user/network on the G2.2 must b e user. Ta b l e  5 - 1
 shows 
the recommended ways to administer the user-network and peer protocols 
when a G2.2 is c onnec ted  to a G3V2:
NOTE:
When c onnec ting  two DEFINITY systems via ISDN PRI, you should  use the 
user-network p rotoc ol and  c ountry op tion 1(G3V2) if you want the extra 
features sup p orted  b y op tion 1.
Layer 2 Timers and Counters
LAPD d efines several timers and  c ounters that are ad ministrab le in G2.2 b ut not 
in G3V2 systems. The G2.2 ad ministration for these timers and  c ounters is in 
p roc ed ure 262, word  1, field s 9 throug h 12. In g eneral, the d efault setting s will 
work.
ISDN PRI Layer 3
This sec tion d esc rib es those asp ec ts of layer 3 of ISDN PRI sig naling  having  
relevanc e to c ustomers or AT&T field  p ersonnel involved  in imp lementing  or 
sup p orting ISDN PRI on DEFINITY systems. For examp le, several ISDN PRI 
information elements used  in DEFINITY ISDN PRI systems are p op ulated  d irec tly 
from op tions set in system ad ministration and  are thus relevant to c ustomers or 
Table 5-1. Administering the User-Network and Peer Protocols
G2.2 G3V2
Administered as Layer 2 Layer 3 Administered as Layer 2 Layer 3
user user user network network network
user user user peer-master/side A (G3V2 only) master side A
network network network p eer-slave/sid e B (G3V2 only) slave sid e B 
						

							DEFINITY Communications System Generic 2.2 and Generic 3 V2 
DS1/CEPT1/ISDN PRI Reference  
555-025-107  Issue 1
July 1993
Layers 2 and 3 
Page 5-9 ISDN PRI Layer 3 
5
AT&T personnel attemp ting  to imp lement ISDN PRI c apab ilities. The sub jec ts 
c overed  in the CCITT, AT&T network, and other glob al ISDN PRI sp ec ific ations 
serve as the temp late for the subjec ts in this c hap ter.
ISDN PRI layer 3 is the p rotoc ol d efining  the p roc ed ures for using  a set of 
messag es to estab lish, maintain, and terminate c irc uit switc hed  c onnec tions 
between ISDN PRI endpoints and to exchange user-to-user information between 
end p oints. The ISDN PRI sp ec ific ations also d esc ribe p roc ed ures for p ac ket 
switc hed  c onnec tions and  for the exc hang e of maintenanc e messag es, b ut this 
d oc ument d oes not c over these sub jec ts. The p rotoc ol for estab lishing , 
maintaining , and  terminating  c onnec tions is c alled  c all c ontrol. The p rotoc ols for 
exc hanging  user-to-user information c an b e d ivid ed  into two typ es:
nCall control message associated user-to-user information
nTemp orary signaling  c onnec tions
Both call control signaling and user-to-user information signaling c an be 
ac c omp lished  b y the D c hannel c ontrolling  only the B c hannels on its p hysic al 
interfac e (fac ility assoc iated sig naling ) or b y the D c hannel c ontrolling  B 
c hannels on up  to 20 interfac es (non-fac ility-assoc iated  sig naling ). In all c ases, a 
set of messages are used  to c onvey c all c ontrol and  user-to-user information 
b etween the end p oints. The messag es are c omp osed  of information elements 
(IEs), whic h are the c onveyors of the information exc hang ed  b etween the 
end p oints of the ISDN PRI link. The DEFINITY systems implement this p rotoc ol 
ac c ord ing to the CCITT Q.931 sp ec ific ation with variations d ep end ing  on the 
system. G2.2 and  G3V2 with c ountry op tion 1, for examp le, use the layer 3 
procedures specified by the AT&T standard 
Technic al Reference 41449, 
whereas G3V2 c ountry p rotoc ol op tions other than 1 imp lement this layer 
ac c ord ing to the CCITT Q.931 sp ec ific ation with variations d ep end ing  on whic h 
c ountry p rotoc ol is in effec t for the interfac e b oard  (c ountry p rotoc ol is 
ad ministered  in the DS1 c irc uit p ac k form).
NOTE:
Country p rotoc ol c an b e ad ministered  in two forms in G3V2, the DS1 c irc uit 
p ac k form and  the system p arameters - c ountry op tions form. The 
ad ministration in the c ountry op tions form is for line p orts in the system and  
thus d oes not have relevanc e to d ig ital trunks in this d oc ument.
Sinc e this d oc ument only disc usses those elements of the layer 3 p rotoc ol having  
relevanc e to field  p ersonnel, the d etails of the p rotoc ol are not c overed . For those 
d etails, refer to the CCITT Q.931 stand ard or the stand ard ap p lic ab le to the 
c ountry b eing  ad ministered .
Country-Specific Layer 3 in G3V2
Dep end ing  on the system c onnec ted  to the G3V2 or on the c ountry in whic h the 
G3V2 is b eing  used , some asp ec ts of c all c ontrol vary from the CCITT 
sp ec ific ation b y ad hering  to a d ifferent sp ec ific ation. Following  is a list of the 
various ISDN PRI sp ec ific ations sup p orted  b y G3V2: 
						

							DEFINITY Communications System Generic 2.2 and Generic 3 V2 
DS1/CEPT1/ISDN PRI Reference  
555-025-107  Issue 1
July 1993
Layers 2 and 3 
Page 5-10 ISDN PRI Layer 3 
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nAUSTEL (the Australian Stand ard s Institute) TS 014.1/1990; PRI 
Connec tion Volume I: Interfac e Sp ec ific ation for Layers 1,2, and  3.LI
nECMA 143 Basic  Circ uit Switc hed  Call Control
nETSI (the Europ ean Telec om Stand ards Institute) ETS 300102-1; ISDN 
User-Network Interfac e Layer 3 Sp ec ific ation for Basic  Call Control 
Ap p lic ations of CCITT Rec ommend ations Q.930/I.450 and  Q.931/I.451
nAT&T ISDN Primary Rate Interfac e (TR41449)
nANSI T1.607 (ISDN Circ uit-Switc hed  Call Proc ed ures)
nDig ital Ac c ess Sig nalling  Stand ard  II/Dig ital Private Network Signalling  
St a n d a rd  ( D ASSI I / D PN SS) { vi a  t h e  3 N ET c o n ve r t e r }  Te le p h o n i c a  I SD N  PRI  
sp ec ific ation for Sp ain
nNTT INFS 1500 (ISDN PRI sp ec ific ation for Jap an)
These variations from the CCITT sp ec ific ation are ad ministered  in the Country 
Protocol
 field  in the DS1 c irc uit p ac k form. If, for examp le, you enter 2
 in that 
field , the AUSTEL sp ec ific ation will b e used  for ISDN PRI layer 3 sig naling.
Facility-Associated and Non-Facility Associated
Signaling
Sig naling on ISDN PRI trunks c onsists of messag es transp orted  over the D 
c hannel, whic h is c hannel 24 on a DS1 interfac e or c hannel 16 on a CEPT1 
interfac e. Two method s exist for p rovid ing  this sig naling :
nThe D c hannel c an p rovid e sig naling for the other B c hannels on the same 
interfac e. This is c alled  fac ility assoc iated  sig naling  (FAS).
nThe D c hannel c an p rovid e sig naling  for B c hannels on more than one 
interfac e. This is c alled  non-fac ility assoc iated  sig naling .
In ad d ition, in NFAS sig naling  arrang ements, the c ap ab ility exists to d esig nate a 
D c hannel on one interfac e to b e a b ac kup  to a D c hannel on another interfac e in 
c ase of failure. This is c alled  D c hannel b ac kup .
G2.2 FAS/NFAS Implementation
In G2.2, fac ility assoc iated sig naling is imp lemented  throug h ad ministration in 
p roc ed ure 260, word  1, field  14 and  p roc ed ure 100, word  3, field  2. Proc edure 
260, word  1, field  14 sets the ap p lic ation typ e for the DS1 interfac e as ISDN PRI 
and  p roc ed ure 100, word  3, field  2 sets the sig naling  typ e for the trunk g roup  as 
ISDN PRI signaling . Implementing  NFAS on G2.2 requires ad d itional p roc ed ures. 
Following  are g uid elines for imp lementing  NFAS on G2.2 systems: 
						

							DEFINITY Communications System Generic 2.2 and Generic 3 V2 
DS1/CEPT1/ISDN PRI Reference  
555-025-107  Issue 1
July 1993
Layers 2 and 3 
Page 5-11 ISDN PRI Layer 3 
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nIf NFAS is ad ministered , a sing le D c hannel c an c ontrol up to 479 B 
c hannels on any c omb ination of interfac es anywhere in the rest of the 
system. For examp le, a D c hannel c an b e ad ministered to c ontrol only the 
other 23 B c hannels on the same interfac e, yield ing  the same results as if 
NFAS is not ad ministered , or it c an c ontrol B c hannels on c omb inations of 
b oth ANN35s and  TN767s in other universal and  trad itional mod ules.
nA D c hannel on an ANN35 interfac e c an c ontrol B c hannels on TN767s 
and  a D c hannel on a TN767 interfac e c an c ontrol B c hannels on ANN35s.
nIf a TN767 has a D c hannel, a TN555 must b e loc ated in the virtual slot 
next to the TN767. If the TN767 c ontains only B c hannels, no TN555 is 
req uired .
nAn interfac e c an b e ad ministered  for 24 B c hannels in an NFAS 
arrang ement. In fac t, this is always the c ase exc ep t for the interfac es 
c ontaining  a D c hannel.
nAn interfac e c an have no more than one D c hannel.
nA D c hannel c an b e d esig nated  as either a p rimary or a b ac kup  if NFAS 
with D c hannel b ac kup  is used .
nThe b ac kup  D c hannel c ontrols only those B c hannels c ontrolled  b y the 
p rimary D c hannel.
nThe b ac kup D c hannel d oes nothing  at layer 3 until the p rimary D c hannel 
fails.
nIf the p rimary D c hannel fails, the b ac kup  D c hannel b ec omes ac tive and  
the p rimary b ec omes inac tive.
nAll B c hannels c ontrolled b y a sing le D c hannel (a D c hannel g roup ) must 
terminate at the same system at whic h the D c hannel terminates. This is 
true on a p oint-to-p oint b asis only. For examp le, if a G2.2 is c onnec ted  to 
another G2.2 throug h the 4ESS with ISDN PRI ac c ess on b oth systems, 
the B c hannels of eac h systems D c hannel g roup s must terminate at the 
4ESS, b ut not nec essarily at the far-end system (some may go to 
MEGACOM, others to SDN for examp le).
nThe terminating ISDN fac ility interfac e IDs must matc h the orig inating  
interfac e IDs.
nWithout ad ministering  NFAS for a trunk (B c hannel), the interfac e ID in the 
c hannel ID information element will not b e p opulated  for any c alls mad e 
on that trunk. For example, if an ANN35 is not administered for NFAS, it is 
a 23B +  D interfac e b ut no interfac e ID will be sent on the D c hannel 
messag es for those trunks. If, however, this same interfac e is 
ad ministered  for NFAS and  the D c hannel c ontrols the B c hannels on the 
same b oard , it is still a 23B +  D b oard  b ut now the interfac e ID will be sent.
The following  list d esc rib es ad ministration p roc ed ures for initially imp lementing  
NFAS: 
						

							DEFINITY Communications System Generic 2.2 and Generic 3 V2 
DS1/CEPT1/ISDN PRI Reference  
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July 1993
Layers 2 and 3 
Page 5-12 ISDN PRI Layer 3 
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1. Ad minister the ISDN interfac e (c irc uit p ac k) loc ations in p roc ed ure 260, 
word 1.
— If you want this interfac e to c ontain 24 B c hannels, assig n a 1
 in 
field  7.
— If you want this interfac e to c ontain a D c hannel, assig n a 0
 in field  
7.
2. Assig n the D c hannel g roup  numb ers in p roc ed ure 262, word  2. There will 
b e one g roup  numb er p er interfac e c ontaining  a p rimary D c hannel. If a D 
c hannel has a b ac kup , assign the b ac kup  to the same g roup  numb er in 
this p roc ed ure. For reliability p urp oses, you c an assign b ac kup  D 
c hannels from d ifferent c arriers or mod ules than the p rimary D c hannels.
3. For eac h ANN35 and  TN767 c ontaining  a D c hannel in an NFAS 
arrang ement, assign an interfac e id entifier in p roc ed ure 262, word  1, field  
13. This field  is used  to p op ulate the ISDN interfac e ID in the c hannel ID 
information element. The following  list sug g ests a c onvention for d oing  
this:
— Assig n interfac e id entifier 0 to eac h b oard c ontaining a D c hannel.
— Assig n interfac e id entifier 1 to eac h b oard c ontaining a b ac kup D 
c hannel.
4. For eac h ANN35 and  TN767 c ontaining  24 B c hannels, assig n an 
interfac e identifier in proc edure 262, word  1, field 13. Assig n id entifiers 
seq uentially starting  with 2 if the D c hannel g roup  has a b ac kup D 
c hannel, or 1 if it d oes not. In other word s, all b oard s in a D c hannel group  
should  b e numb ered sequentially starting  with 0 and  not skipp ing  any 
numbers.
5. Assig n the ind ivid ual trunks (c hannels) to eac h D c hannel g roup in 
p roc ed ure 116, word  1.
NOTE:
A DS1 b oard  is d efined  as b eing  a memb er of a signaling  g roup  if 
any of the B c hannels on the b oard  are in the sig naling  g roup . For 
examp le, if c hannels 1-10 on a b oard  are assig ned  to signaling  
g roup  1 and  11-24 are assigned  to sig naling  g roup  2, then the b oard  
is a member of both signaling groups 1 and 2. This is important 
b ec ause an interfac e id entifier c annot b e d up lic ated  within a 
sig naling  g roup . Thus, if another b oard  in the ab ove examp le 
c ontained  all its B c hannels from sig naling  group  2, it c ould  not have 
an interfac e id entifier of 1 b ec ause that id entifier has alread y b een 
used . For this reason, and  in g eneral for ease of ad ministration and  
maintenanc e, you should  not mix B c hannels from d ifferent sig naling  
g roup s on a b oard . 
						

							DEFINITY Communications System Generic 2.2 and Generic 3 V2 
DS1/CEPT1/ISDN PRI Reference  
555-025-107  Issue 1
July 1993
Layers 2 and 3 
Page 5-13 ISDN PRI Layer 3 
5
G3V2 FAS/NFAS Implementation
FAS and  NFAS in G3V2 is imp lemented in the DS1 c irc uit p ac k form, the 
sig naling  g roup  form, and  the ISDN PRI trunk g roup  form. If you ad minister 
isdn-pri
 in the Signaling Mode
 field  on the DS1 c irc uit p ac k form, then the 
c hannels on that interfac e will c onsist of 23 DS1 or 30 CEPT1 b earer c hannels 
and  a D c hannel. If isdn-ext
 is ad ministered , all c hannels on the b oard  will b e B 
c hannels, with their assoc iated D c hannels loc ated  on d ifferent b oard s 
d etermined  b y ad ministration in the sig naling  g roup  form and  the ISDN PRI trunk 
group form.
The signaling  g roup  form further d efines the ISDN PRI sig naling  b y assig ning  D 
c hannels as sig naling c hannels for B c hannels. The D c hannel c an b e assigned  
to B c hannels on its own b oard  (fac ility assoc iated  sig naling , or FAS), or it c an be 
assig ned  to B c hannels on its own b oard  and /or other b oard s (non-fac ility 
assoc iated signaling, or NFAS). In addition, a D channel can be assigned to 
b ac k up  another D c hannel in the c ase of failure of that D c hannel. A signaling  
g roup  c omp rises all the B c hannels c ontrolled  b y a uniq ue D c hannel (and  its 
backup, if applicable). Eight signaling groups are allowed in G3iV2 and 166 in 
G3rV2. Thus, in G3iV2 for examp le, if all sig naling  g roup s are FAS g roup s on DS1 
interfac es, a total of 23X8= 184 (1.544 rate) B c hannels c an b e used  as trunks. A 
D c hannel, however, c an p rovid e signaling  for up  to 20 interfac es. A DS1 
interfac e c ontains 24 NFAS B c hannels. Thus, a sing le D c hannel c an sig nal for 
(20X24) -1 =  479 B c hannels (the 1 is sub trac ted  bec ause one of the c hannels is 
the D c hannel). In G3iV2, however, a maximum of 400 trunks of any kind  c an 
exist on any system, making  this up p er limit ac ad emic .
Not all B c hannels on an NFAS b oard  have to be c ontrolled  b y the same D 
c hannel. For examp le, c hannels 1, 3, and  4 c ould  b e c ontrolled  b y one D 
c hannel and  the rest b y another. This is mad e p ossib le b y the fac t that a DS1 
b oard  c an app ear in more than one sig naling  g roup  and  that ind ivid ual ports of 
the board are assigned to signaling groups in the trunk group form. If an NFAS 
DS1 b oard ap p ears in only one sig naling  g roup , however, all p orts on that b oard  
are automatic ally c ontrolled  b y the assoc iated  D c hannel.
NOTE:
You should  assig n all B c hannels on a g iven interfac e (c irc uit pac k) to the 
same D c hannel g roup . If this ad vic e is not followed , id entifying  the 
p hysic al b oard  assoc iated  with the trunk for maintenanc e p urp oses c ould  
become difficult. 
When a sec ond ary D c hannel is assig ned , it is used  as a b ac kup  to the p rimary 
c hannel. It remains in a stand b y state (layer 2 remains ac tive) until the p rimary 
c hannel fails or until a maintenanc e c ommand  is issued  to switc h the c hannels. 
When either of these hap p ens, the sec ond ary c hannel b ec omes ac tive. When 
the failed  p rimary c hannel rec overs its layer 2 c ap ab ility, it enters the stand b y 
state. If the sec ondary sub sequently fails, the p rimary ag ain b ec omes ac tive, 
and  so on. If b oth c hannels fail, the new ac tive one will b e the one to first rec over 
its layer 2 c apab ility. If b oth rec over simultaneously (roug hly), the p rimary will 
b ec ome the ac tive c hannel.  
						

							DEFINITY Communications System Generic 2.2 and Generic 3 V2 
DS1/CEPT1/ISDN PRI Reference  
555-025-107  Issue 1
July 1993
Layers 2 and 3 
Page 5-14 ISDN PRI Layer 3 
5
The following list describes how to implement ISDN PRI signaling in G3V2:
nNFAS and  D c hannel b ac kup  are not sup ported  unless the c ountry 
p rotoc ol is 1
 (U.S.) in the DS1 c irc uit p ac k form for the b oard s c ontaining  
the p rimary and  sec ond ary D c hannels.
nAd minister the sig naling  mode in the DS1 c irc uit p ac k form. Use isdn-pri
 if 
the B c hannels on the b oard are to b e FAS B c hannels. Enter isdn-ext
 if 
the B c hannels are to b e in NFAS sig naling  group s. If the D c hannel on 
this b oard  is g oing  to b e a b ac kup  to a p rimary D c hannel on another 
board, the line coding
, connect
, and  interface
 field s must b e the 
same for the two b oard s.
nUse the c ommand add signaling group
, change signaling group
, or 
remove signaling group
 and  the g roup  numb er that you want to ad d, 
c hange, or remove. If you want to remove a sig naling g roup , you must first 
remove all its trunk memb ers from any trunk g roup s and  remove all trunk 
boards in the signaling group.
nIf the g roup number is to be a FAS sig naling  g roup , the Associated 
Signaling?
 field  is y
. Enter the c irc uit loc ation of the D c hannel in the 
Primary D channel
 field . Rememb er the D c hannel on a DS1 interfac e 
is c irc uit 24 and c irc uit 16 on a CEPT1 interfac e.
nIf the g roup number is to be an NFAS g roup , enter n
 in the Associated 
Signaling
 field .
— Enter the loc ation (d own to the c irc uit) of the primary D c hannel in 
the Primary D channel
 field . The c irc uit numb er is 24 for a DS1 
interfac e or 16 for a CEPT1 interfac e. This D c hannel c annot be 
ad ministered  in any other sig naling  g roup .
— If you want to have a D c hannel to b ac k up the p rimary D c hannel in 
c ase it fails (p ower g oes out in the c arrier, for examp le), enter the 
loc ation of another D c hannel in the Secondary D channel
 field . 
This D c hannel c annot b e on the same b oard as the p rimary D 
c hannel. This D c hannel c annot ap p ear in any other sig naling  
g roup . Thus, it is only used  when the p rimary D c hannel fails. If the 
p rimary D c hannel fails, the sec ond ary b ec omes ac tive. The 
sec ond ary D c hannel should  b e p lac ed  in a different p ort network 
from the primary, if p ossib le. 
— Enter the b oard loc ation (d own to the slot numb er) of eac h DS1 
b oard  c ontaining  the B c hannels for whic h the D c hannel is g oing  to 
signal in the Trunk Brd
 fields. A board location cannot appear 
more than onc e in the same sig naling  g roup . You c annot remove 
this sig naling  g roup  without first removing  these b oard  loc ations 
from the form. The B c hannels on these board s are later assig ned  
as members in ISDN PRI trunk g roups.
— Enter a d ifferent numb er in the rang e 0-31 for eac h trunk b oard  in 
the Interface ID
 field . This field  is used to p opulate the interfac e 
ID field  in the c hannel ID information element. The following  list 
sug g ests a c onvention for d oing  this: