ATT DEFINITY Communications System Generic 3 Instructions Manual

							Look Ahead Interflow
Issue  3   March 1996
3-847
Look Ahead Interflow Basics
When one switch has an overload of incoming calls, it may b ecome necessary to 
route some of the incoming calls to another switch so they can be handled more 
efficiently and will not be lost. Look Ahead Interflow is simp ly the means used to 
determine whether the other switch is able to handle the calls. When preset 
thresholds at one switch are reached (for example, the numb er of calls in queue), 
and another call comes in, that switch c hecks to see if another switch can handle 
the call. The other switch then checks to make sure it can handle the call.  If it 
can, the call is sent to that switch.  If it cannot, the sending switch must try to 
process the call in another way, such as intraflowing to a backup split or placing 
a second Look Ahead Interflow call attempt to an alternate b ackup switch.
Look Ahead Interflow is accomplished through the use of call vectors and their 
associated c ommands.  These call vectors are a dministered for both the sending 
and receiving switches:
nSending Switc h
Vectors at the sending switch use conditional goto vector commands to 
test outflow threshold conditions, and route-to commands to send the 
call to another switch. The sending switch may provide alternate treatment 
if the call is denied at the receiving switch.
nReceiving Switch
Vectors at the receiving switch use conditional goto vector commands to 
do inflow checking and decide whether the call should be accepted or 
denied. Call acceptance is accomplished when commands such as 
queue-to main, check-backup, announcement, collect, and 
wait-time are reached in the call vector at the receiving switch. (See 
Table 3-67 for more information on acceptance conditions.) Call denial is 
accomplished when commands such as busy and disconnect after 
announcement none are reached in the call vector at the receiving 
switch.
Two-Switch Look Ahead Interflow Configuration
An examp le of a Two-Switch Look Ahead Interflow configuration is shown in  
Figure 3-24. The operation of the sending switch and the receiving switch are 
described in the following paragraphs. 
						

							Feature Descriptions
3-848Issue  3   March 1996 
Figure 3-24. Two-Switch Look Ahead Interflow Connections
Sending Switch Operation
As with standard vectoring interflow, outflow checking and outflow is 
accomplished by means of conditional goto
 and route-to vector commands. 
There are no unique vector commands for this feature. If the Look Ahead 
Interflow option is enabled, and the call is being routed over an ISDN-PRI facility, 
interflow will automatically be carried out on a look ahead basis. (There is one 
exception to this rule. A route-to with cov y vector command will never 
result in a Look Ahead Interflow call.)
For Look Ahead Interflow calls, vector processing does not immediately 
terminate when ISDN-PRI facilities are successfully seized for a route-to 
operation. Instead, the call remains in any hunt group or split queues at the 
sending switch until it is accepted at the receiving switch. Any audible feedback 
initiate d by the vector continues. If an a gent  becomes available at the sending 
switch during a Look Ahead Interflow call attempt, the caller is immediately 
connected to the available agent, and the Look Ahead Interflow call attempt is 
dropped.
The sending switch attempts to interflow the call to the receiving switch.  We will 
assume a successful ISDN-PRI connection. One of the following then occurs.
nCall Acceptance
If a call acceptance message is returned by the receiving switch before 
any call denial message, the sending switch will terminate vector 
processing, disconnect any tones a p plied by the sending switch vector 
and remove the call from all queues at the sending switch. Control of the 
call is now passed to the receiving switch.
INCOMING
CALLSSENDING
SWITCH
SWITCHISDN - PRI
RECEIVING
MAIN
SPLITBACKUP
SPLIT
PRIVATE NETWORK 
						

							Look Ahead Interflow
Issue  3   March 1996
3-849
nCall Denial
If a call d enial message is returned by the receiving  switch b efore any call 
acceptance message, the sending switch will drop the Look Ahead 
Interflow call attempt and continue vector processing at the next vector 
step.
nTimeout
If a call acceptance or call denial message is not returned from the 
receiving switch within 10 seconds after the receiving switch receives the 
Look Ahead Interflow call request, the Look Ahead Interflow attempt is 
dropped and the sending switch continues vector processing at the next 
vector step.
An examp le of an outflow vector used by a sending switch is as follows:
1. queue-to main split 3 pri m
2. announcement 1001
3. goto step 5 if oldest-call-wait in split 3 pri l > 30
4. wait-time 20 secs hearing music
5. route-to  with cov n if unconditionally
6. announcement 1002
7. wait-time 120 secs hearing music
8. goto step 6 if unconditionally
If split 3 has no available agents, Step 1 will place the caller in split 3’s queue at 
medium priority. In Step 2, an announcement is played apologizing for the delay. 
Step 3 does the outflow checking. If calls have b een queued up for longer than 
30 seconds, the vector goes to Step 5 and does Look Ahead Interflow. 
Otherwise, the vector proceeds to Step 4 and music is played for 20 seconds. If 
the c all is still not answered after 20 seconds, then the vector goes to Ste p 5 and 
attempts Look Ahead Interflow. In Step 5, a Look Ahead Interflow call is placed to 
a remote switch. If the call is a c cepted, the incoming call is removed from split 
3’s queue and control of the call is passed to the receiving switch. If the call is 
denied, the caller remains in q ueue and hears announcement 1002 followed by 
music.
Receiving Switch Operation
When the receiving switch receives the Look Ahead Interflow request, the call 
routes to a VDN, the VDN maps the call to the receiving switch’s inflow vector 
and vector processing begins, starting with inflow checking. Inflow checking is 
accomplished with conditional goto commands in the inflow vector. The 
decision to accept or reject a call can be based on checks of the following:
nNumber of staffed agents
nNumber of available agents 
						

							Feature Descriptions
3-850Issue  3   March 1996 
nTime of day/week
nNumber of calls in split’s queue
nNumber of seconds that the oldest call has been waiting in the split’s 
queue
nRolling Average Speed of Answer (G3V4 and later releases)
nActive VDN calls (G3V4 a n d later releases)
nExpected Wait Time (G3V4 and later releases)
nANI (G3V4 and  later releases)
nII-digits (G3V4 and later releases)
Once inflow checking is complete, acceptance of the look ahead call can b e 
accomplished by executing any of the vector commands shown in Table 3-67.
Table 3-67. Call Acceptance Vector Commands and 
Qualifications
Call Acceptance 
Vector Commands Qualification
announcement Announcement available
or
Queued for announcement
or
Retrying announcement
check-backupCall terminates to agent
or
Call queued for sp lit
c ollect Always
converse-on VRU answers the call
or
Call queued to converse sp lit
disconnect With announcement and announcement available
or
With announcement and queued for announcement
or
With announcement and retrying announcement
messaging Successful
or
Queued
Continued on next page 
						

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Issue  3   March 1996
3-851
If, during inflow checking, the receiving switch decides that it is unable to accept 
the look ahead call, call denial can be accomplished by executing any of the 
vector commands listed in  Table 3-68. Use of the busy command is 
recommended over the disconnect command to allow for compati bility with 
network services.
q ueue-to main Call terminates to agent
or
Call queued for sp lit
route-toTerminates to valid local destination
or
Successfully seizes a non-PRI trunk
or
Results in Look Ahead Interflow call attempt and the 
call is accepted by the far end switch
wait-time Always (exc ept 
wait-time hearing i-silent which is 
neutral)
Table 3-68. Call Denial Vector Commands and Qualifications
Call Denial Vector 
Commands Qualification
busy Always
disconnect With no announcement
or
With announcement but announcement unavailable Table 3-67. Call Acceptance Vector Commands and 
Qualifications — Continued  
Call Acceptance 
Vector Commands Qualification
Continued on next page 
						

							Feature Descriptions
3-852Issue  3   March 1996 
The vector commands shown in Table 3-69 do not generate either call 
acceptance or denial messages and are considered neutral.
The following is an example of an inflow vector used by a receiving switch.
1. goto step 6 if staffed-agents in split 12 is <  3
2. goto step 6 if queued-calls in split 12 pri l is > 4
3. queue-to main split 12 pri h
4. wait-time 30 secs hearing music
5. stop
6. busy
Steps 1 and 2 do inflow checking. For split 12, if the numb er of staffed agents is 
less than three or the number of calls in queue is greater than 4, call control is 
transferred to Step 6 which denies the look ahead call. Otherwise, Step 3 will 
queue the call for split 12 and return a call acceptance message to the sending 
switch.
Table 3-69. Neutral Vector Commands and Qualifications
Neutral Vector 
Commands Qualification
adjunct routing Always
announcement Announcement unavailable
check-backup The call neither terminates nor queues
converse-on Call neither terminates nor queues
goto step Always
goto vector Always
messaging Failure
q ueue-to main The call neither terminates nor queues
route-to Unsuccessful termination
or
Trunk not seized
or
Look Ahead Interflow call denied by far end switch
sto p Always
wait-time hearing 
i-silentAlways (New with G3V4) 
						

							Look Ahead Interflow
Issue  3   March 1996
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Tandem Switch Configuration
Tandem Look Ahead Interflow can be accomplished with Call Vectoring and 
Look Ahead Interflow active at the receiving switch by using route-to 
commands that contain external destinations which use ISDN-PRI facilities.
An examp le of a tandem Look Ahead Interflow configuration is shown in Figure 
3-25. The o peration of the sending switch and the receiving switch are d escribed 
in the following paragraphs.
Figure 3-25. Look Ahead Interflow Using a Tandem Switch
Sending Switch Operation
The sending switch is unaware of the fact that its Look Ahead Interflow call is 
being tandeme d to an alternate switch. The operation of the sending switch in 
the tandeming configuration is exactly as for the two switch configuration.
Tandem Switch Operation
If the receiving switch executes a route-to command that routes the call over 
an ISDN facility before call acceptance, the route-to command is performe d 
on a ‘‘look ahead’’ basis in the same manner as a sending switch. If the call is 
accepted at the far end switch, a c ceptance is p assed to the sending switch, and 
control of the call is passed to the far end switch with tandeming of the original 
calling party information and the original DNIS name. If the call is denied, the 
next step of the tandem switch vector is executed.  If a denial is retained by the 
Tandem Switch to the originating switch, the next vector step on the originating 
switch is executed.
INCOMINGSENDING
SWITCH SWITCHISDN - PRI
MAIN
SPLITBACKUP
SPLIT
FAR END
SWITCHISDN - PRITANDEM
CALLS
ALTERNATE
BACKUP
SPLIT 
						

							Feature Descriptions
3-854Issue  3   March 1996 
Great c are should b e taken by the vector programmer to ensure that the sending 
switch is not used as a backup location for the tandem switch or any of the far 
end switches. If administered in this manner, all trunk facilities could be tied up 
by a single call.
Example of Tandem Switch Vector
An examp le of a tandem switch vector follows:
1. goto ste p 4if staffed-agents in split 30 > 5
2. route-to  if unconditionally
3. busy
4. queue-to main split 30 pri m
5. announcement 2300
6. wait-time 60 secs hearing music
7. goto step 5 if unconditionally
Step 1 checks the inflow thresholds.  If the inflow criteria is acceptable, Step 
4(queue-to main) will p rovide acceptance to the sending switch. Therefore, 
Steps 5-7 provide a typical q ueuing-wait sc heme. If the call c annot b e handled at 
split 30, the route-to command checks another Look Ahead Interflow 
equip ped switch on a ‘‘look ahead’’ basis. If the far end switch  rejects the call, 
the busy
 command causes a denial to be sent to the sending switch. If the 
far-end switch accepts the call, then the acceptance is relayed back to the 
sending switch.
Far End Switch Operation
The far end switch is also unaware that tandeming has taken place. The far end 
switch will operate the same as in the case of the receiving switch in the 
two-switch configuration.
Display Information
Answering Agent’s Display
The DNIS information in the Look Ahead Interflow information element provided 
by ISDN-PRI is presented on the answering agent’s display on the receiving 
switch if the Look Ahead Interflow o ption is enabled, the c all routes to a VDN, and 
the DNIS name is not blank.
The DNIS name included in the Look Ahead Interflow information element is as 
follows:
nIf this is a tandemed look ahead call, then the Look Ahead Interflow DNIS 
information from the original look ahead call is used.
nIf no redirection has taken place at the sending switch, the VDN name 
according to display override rules are used. 
						

							Look Ahead Interflow
Issue  3   March 1996
3-855
nIf redirection has occurred, display override rules do not take effect. The 
Look Ahead Interflow DNIS will contain the original VDN name, or, if 
multiple VDNs are accessed, the name of the VDN last accessed by 
means of a route-to vector command.
VDNs that ma p to vectors which place Look Ahead Interflow calls must have their 
ISDN CPN prefixes administered. Failure to administer the ISDN CPN prefix 
results in a Look Ahead Interflow DNIS of all spaces being sent and disp layed on 
the answering agent’s terminal.
Originator’s Display
On internal calls, the originator’s display is the same as for normal Call Vectoring. 
However, the following precaution should be taken to prevent undesirable 
display up dates from being received during Look Ahead Interflow call attempts.
Since most customers would not like the originator’s display to be updated on 
each Look Ahead Interflow call attempt, Look Ahead Interflow calls should 
normally go out over trunk groups with the “Outgoing Display” field set to no.
Audible Feedback
Audible ringback is provided to the caller when a wait-time hearing 
ringback vector command is executed or when the call is successfully route d 
to a local destination.
Care must be taken by the vector programmer not to confuse callers by 
providing incompatible audible feedback at both the outflow and inflow vectors. 
For exam ple,  providing ringback at the receiving switch might be confusing to 
the caller if ringback and an announcement had previously been supplied by the 
sending switch.
Normally a vector for human callers should initially return audible feedback such 
as ringback, music, or an announcement so that the caller knows that the c all g ot 
through.  However, vectors which do not return any audible feedback may be 
used in situations where VDNs are a c cessed b y machines and audible feedback 
may be inappropriate and/or undesirable.
The receiving switch vector does not initially give Look Ahead Interflow calls any 
locally denied termination treatment such as busy tone, reord er tone, or intercept 
tone. The caller  does not hear these because feedback is still being provided by 
the sending switch vector.
Considerations
The receiving vector should not be administered to have calls route back to the 
vector for the outflowing switch. If administered as such, all trunk facilities may 
eventually be tied up with the same call. 
						

							Feature Descriptions
3-856Issue  3   March 1996 
All calls routed over ISDN-PRI facilities by means of route-to number with 
cov n
 and route-to digits with cov n vector commands on a switch 
where the Look Ahead Interflow option is enabled are treated as Look Ahead 
Interflow call attempts.
Initial audible feedback may be provided to the caller before interflow is 
attempted. Therefore, another audible feedback from the receiving switch may 
not be appropriate. For exam ple, a caller hearing ringback on the sending switch 
may be confused if music is suddenly a p plied when the call interflows to the 
receiving switch.
Delay in interflowing should be minimized. An acceptance or denial response 
should be provided to the sending switch as quickly as possible by the vectors 
on the receiving switch.
If, d uring Look Ahead Interflow, the call terminates to an agent on the sending 
switch or the call is abandoned by the originator, the Look Ahead Interflow call is 
dropped, vector processing terminates, and the original call is removed from all 
split queues.
It is p ossible d uring a Look Ahead Interflow call attempt for a call to b e accepted 
at a receiving switch, by means of a queue-to main or check-backup 
command, an instant before the call is answered at the sending switch. If the 
acceptance message is d elayed due to signal propagation d elay, there could b e 
a short interval when the c aller and the receiving switch agent are  connected. An 
agent at the sending switch may then answer the call before the a c ceptance 
message arrives at the sending switch. The caller would then be disconnected 
from the receiving switch agent and connected to the sending switch a gent. 
These phantom calls can be eliminated by appropriate programming of the 
inflow vector. If calls are accepted by wait-time or announcement vector 
commands before the call is q ueued to a split, there is no possibility of a 
phantom call occurring.
It is perfectly acceptable for a vector to route a call over an ISDN-PRI facility to a 
destination which is not a VDN. As far as the sending switch is concerned, this 
call will be treate d as a Look Ahead Interflow call even though this is not in fact 
the case. Generic ISDN p rocessing at the receiving switch will cause the call to 
be accepted. The DNIS name and any other information in the Look Ahead 
Interflow information element is ignored.
If a Look Ahead Interflow call terminates to a VDN on a receiving switch where 
the Look Ahead Interflow option is not enabled, intelligent interflow will result. 
However, the DNIS information in the Look Ahead Interflow information element is 
ignored and no intelligent interflow to far-end switches is possible.
Interactions
The following features interact with the Look Ahead Interflow feature: