Now let's talk about a concept that a lot of engineers struggle with which is incoming and outgoing
Gulp is for incoming and outgoing call legs.
The first thing to remember is always look at adult is from the point of view of the road not from the
phone's point of view.
In other words from the rudest point of view when 1000 phones 1001 there is an incoming call from 1000
and an outgoing call to 1001 so from the writer's point of view there is an incoming call late or incoming
WPA.
When the call arrives from telephone 1000.
So this is an incoming call leg when the call is established to 1001.
That is an outgoing call leg or outgoing dull.
Yeah essentially what happens is the rudder breaks the call up into two parts.
There's the initial call setup from 1000 which is the incoming call leg or incoming Delta the second
half is the establishment of the call to 1001 which is the outgoing call leg or outgoing Delta.
The rudder then combines those to call legs into an internal call.
So we have an incoming call leg and an outgoing call leg to separate calls if you're like or half of
calls which are then bonded together or joined together to form the into n call.
So from the writer's point of view there are two cool legs involved in the establishment of a call from
1000 to 1001.
You have what's called the incoming call leg once again and the outgoing call leg or a call to be established.
There must always be an incoming call leg and an outgoing call leg.
So how does the rider choose which does appear to use as the incoming call leg and which doubled it
to use as the outgoing call leg on our original configuration with these two phones.
We created to Dalby as we credit adults for phone 1000 and we created adult here for phone 1001 so our
configuration would look as follows is adult Pier 1 puts this nation pattern 1000 pointing to the first
port of 0 selection errors there 0 and there's another plot style here pointing to 1001 on the second
port.
Now when a call arrives on the road it the first thing you need to look at is the direction of the call.
So in this example when 1000 phones 1001 the direction is from right to left.
So the call is arriving from 1000 going to 1001.
So from the riders point of view the incoming dot here that is used for 1000 is this all doll.
Pier 1 even though the word destination pattern is configured in the doll pier and this example the
destination pattern is not used as the destination pattern.
It's used as the DNI automatic no identification or CSI whichever term you prefer the caller line ID.
So 1000 is the CLIA that is allocated to the phone.
I'm going to demonstrate this in a moment.
So you'll see exactly what I mean.
But essentially the call is coming from 1000 going to 1001 so dull.
Pier 1 with destination pattern 1000 is uses the incoming WBA adult Pier 2 with this nation pattern
1001.
It uses the outgoing pier.
The reason why is from the rudest point of view.
The call arrived from 1000 and was made to 1001 so it does establish that into then call an incoming
Dole is allocated to this part of the call or call lake and an outgoing adult is allocated to the second
part of the call leg.
The thing to remember is that they are to call legs in this example an incoming call leg and an outgoing
call leg to call legs make the implement call the let's set up a call between this optic communicator
and the optic communicator en route a team so that I can explain some more detail so it's important
to realize that we've got two IP communicators 1004 is registered to the U.S. Five hundred and two thousand
is registered to write it to the going will hook
you can see the call from two thousand two 1004 successful
and I can answer the call and then muted in our example when the call was made from 1004 to thousand.
There was an incoming call leg to the Rada member using the hidden power created by the E F export.
There is an outgoing dollop here from the U.S. 520 V to the VoIP infrastructures so there is an outgoing
VoIP up here on CMC 2 or added two's point of view.
There is an incoming VoIP here and an aunt going hidden pot style peer to the E F access port for the
IP communicator so they are for double peers or for call legs when a call is made from 1040 2000 just
to go through that again.
There is an incoming Potts doll here it's hidden.
It was created when we created the iPhone the for IP phones.
There is an outgoing voice adult here.
There is an incoming VoIP Delta on Roddick 2 and an outgoing hot stop here for the hidden e f access
port for the IP communicator.
So in other words they are for is if we made a call from the IP communicator to the BlackBerry from
the U.S. 500 point of view.
There is an incoming stop here for the hidden E F X a sport and there is an outgoing port stalled on
the ethics O port to get to the PSTN so they are two dull PS so to demonstrate the concept of cool legs
I'm going to make a call from 1000 to 1001 and you should see that from the rudest point of view.
There is an incoming Delta and an outgoing Delta.
The point to remember is always look at Delta is from the rudest point of view not from the phone's
point of view.
When 1000 phones 1001 is an incoming Delta from 1000 and an outgoing does appear to 1001 if the call
was made in the reverse direction it would be an incoming Dolby for this phone one thousand and one
and an outgoing dollop if for 1000 so teleporting to the U.S. 500
I can do the command debug voice C.C. API in out top to month so we can see the DB bucks please be very
careful with this come on in the real world because it's going to produce a lot of output so I'll go
hook on 1000
and you can see already there is a lot of output there and then I'll go on hook again.
So going through the output there's the debug that we typed
you can see here for instance it's a non ISDN call because we making a call from an analog phone and
what I want to point out is notice yet says incoming Delta 1.
The reason why is the call is being made from telephone number 1000.
So that is the source of the call topping the come on show dial dash fear voice summary shows me that
Delta 1 has been configured with telephone number one thousand on Port 0 6 0 7 0
so when I made a call call it originating from 1000 and thus the incoming DOL peers Pier 1
other information to take note of is the digit timeout and into digit timeout by default set to 10 seconds
you have ten seconds when going off foot to put in your first digit and 10 seconds between each digit
before a call is attempted all the call is torn down
so let's go fuck again.
Now I'm gonna double my first digit and you can see the digit that I dialed was 1 second digit.
You can see it's digit zero third digit.
You can see at zero last digit
and you can hear the phone ring and I've just disconnected the call.
Notice that they called Disconnect so if we go through the output again notice yet says outgoing Delta
is Delta 2.
The call is coming from one thousand notice it says Cisco a Anni or automatic no ID or to put into other
terms that people may use calling line ID so see a lie or cell I.D. or meaning.
This is the calling party no.
Notice the destination number is 1001.
But what I want you to take note of these is that the incoming Delta was one and the outgoing gulp is
to show dial dash give voice summary shows us incoming DLP is one.
The call is coming from one thousand outgoing Delta is to call is going to 1001 so back to our simple
example.
We've got a call from 1000 to 1001.
They're going to be to call legs an incoming and outgoing call leg.
So how are incoming colleagues chosen and how are outgoing colleagues chosen if you've only got two
adult is like in this example.
When the call is made from 1000 to 1001 the destination pattern is used for the CLIA.
So in other words DLP one becomes the incoming bulkier and don't get to becomes the outgoing or outgoing
colleague.
When a call is made from 1001 to 1000 then does appear to becomes the incoming bulkier or incoming call
leg and Dulcie one becomes the outgoing call leg or outgoing gulp.
So the direction of the call affects whether adult is used as the incoming or outgoing DLP it unfortunately
can get more complicated than that to choose an incoming WTO inbound all year.
The route to makes the following decision it firstly looks for adult here with this command incoming
cold no which essentially matches the dial number information service or called number or the number
that you dialed to adult peer.
We haven't configured incoming call numbers in our topology but if you had configured an incoming call
number on one of the dope is that adult here would more likely be chosen as the incoming here than others
because the first choice for an incoming adult is based on incoming cold.
This applies to VoIP Potts T1 E1 cars an ISDN bulb is the second choice is based on what's called answer
address which looks for adult here with a command answer address matching the calling number or call
on ID or automatic no identification.
In other words the number that you're calling from it also applies to white clutch t want you on cars
and ISDN is.
So in other words if you've configured a list of dolphins and one of them has incoming call number and
one of them has answer address incoming call number is more likely to be chosen.
I'll show you an example in a moment.
So the first choice is incoming calls.
No second choices answer address and only then is the third choice of incoming bulkier chosen based
on Destination pattern which uses once again the calling number or a Anni to determine the incoming
double yet if none of that is configured then the Rada uses the port to match on an incoming bulkier
set matches the config adult port to the voice port that is associated with incoming call.
That only applies to what stop is because VoIP adult is don't arrive on a port they arrive on an interface.
And if we can match on any of those then we match on a special piece called doll Pier 0.
So let me show you an example to try and clear this up he has a sample topology where we've got 1000
phoning 1000 or 1 and we want to set up an intra in call the right in each to choose an incoming Delta
and an outgoing call yet so the call is made from 1000 to 1000 and one set to match the incoming dob
in the first half of the poll.
Which of the following would be chosen as the incoming bulb.
If we had configured these three adult is on the route.
Notice we've got adult here one incoming cold number 1001 we've got adult voice 2 Potts answer address
one thousand and Delta three parts.
Destination pattern 1000.
Going back to our list of choices.
The first choices based on incoming call number which is based on DNS so the caller arrives at the Rada
it's made from 1000 to 1001 so you must agree that this will match because the called number or dialled
number or DNS number is 1001.
However the C ally also matches answer address and destination pattern but based on what choices this
is chosen first just to remind you first choices choices incoming call no second choices answer address
and third choices destination pattern.
So in this example gold tier 1 is chosen as the incoming gold here.
If we hadn't configured WPA 1 we had only configured these two dolphins then appear to would be chosen
because answer address is chosen before destination pattern.
If we hadn't configured adult there one or Dota 2 and had only configured adult get 3 then this dull
pair would be chosen as the incoming dolphin here because that's the third choice in our list remembered
incoming call no answer address in the destination pattern and we haven't configured an incoming call
number or answer address.
So the next choice is destination pattern if none of those had been configured then the dull pair would
be chosen based on the port if it was a VoIP call as an example or we couldn't use the port then Delta
0 would be use an incoming Delta and an outgoing Delta has to always be chosen if you hadn't configured
any incoming Delta is Delta 0 would be chosen as it said both in here when nothing else matches so when
there's no match the rider will use adult is zero you can configure adult is zero you can't manipulate
it it is bolted to the Iaw and has the following properties none of which you can change so as an example
you cannot disable that you cannot enable X relay if at all possible you should try and avoid the use
of gulp is zero because you cannot control the setting you should always configure your Rada with an
incoming and outgoing Delta.