Interconnect a Wazo to a PBX via an ISDN link¶

The goal of this architecture can be one of:

start a smooth migration between an old telephony system towards IP telephony with Wazo
bring new features to the PBX like voicemail, conference, IVR etc.

First, Wazo is to be integrated transparently between the operator and the PBX. Then users or features are to be migrated from the PBX to the Wazo.

Warning

It requires a special call routing configuration on both the Wazo and the PBX.

Interconnect a Wazo to a PBX

Hardware¶

General uses¶

You must have an ISDN card able to support both the provider and PBX ISDN links.

Example : If you have two provider links towards the PBX, Wazo should have a 4 spans card : two towards the provider, and two towards the PBX.

If you use two cards¶

If you use two cards, you have to :

Use a cable for clock synchronization between the cards
Configure the wheel to define the cards order in the system.

Please refer to the section Sync cable

Configuration¶

You have now to configure two files :

/etc/dahdi/system.conf
/etc/asterisk/dahdi-channels.conf

system.conf¶

You mainly need to configure the timing parameter on each span. As a general rule :

Provider span - Wazo will get the clock from the provider : the timing value is to be different from 0 (see /etc/dahdi/system.conf section)
PBX span - Wazo will provide the clock to the PBX : the timing value is to be set to 0 (see /etc/dahdi/system.conf section)

Below is an example with two provider links and two PBX links:

# Span 1: TE4/0/1 "TE4XXP (PCI) Card 0 Span 1" (MASTER)
span=1,1,0,ccs,hdb3         # Span towards Provider
bchan=1-15,17-31
dchan=16
echocanceller=mg2,1-15,17-31

# Span 2: TE4/0/2 "TE4XXP (PCI) Card 0 Span 2"
span=2,2,0,ccs,hdb3         # Span towards Provider
bchan=32-46,48-62
dchan=47
echocanceller=mg2,32-46,48-62

# Span 3: TE4/0/3 "TE4XXP (PCI) Card 0 Span 3"
span=3,0,0,ccs,hdb3         # Span towards PBX
bchan=63-77,79-93
dchan=78
echocanceller=mg2,63-77,79-93

# Span 4: TE4/0/4 "TE4XXP (PCI) Card 0 Span 4"
span=4,0,0,ccs,hdb3         # Span towards PBX
bchan=94-108,110-124
dchan=109
echocanceller=mg2,94-108,110-124

dahdi-channels.conf¶

In the file /etc/asterisk/dahdi-channels.conf you need to adjust, for each span :

group : the group number (e.g. 0 for provider links, 2 for PBX links),
context : the context (e.g. from-extern for provider links, from-pabx for PBX links)
signalling : pri_cpe for provider links, pri_net for PBX side

Warning

most of the PBX uses overlap dialing for some destination (digits are sent one by one instead of by block). In this case, the overlapdial parameter has to be activated on the PBX spans:

overlapdial = incoming

Below an example of /etc/asterisk/dahdi-channels.conf:

; Span 1: TE4/0/1 "TE4XXP (PCI) Card 0 Span 1" (MASTER)
group=0,11
context=from-extern
switchtype = euroisdn
signalling = pri_cpe
channel => 1-15,17-31

; Span 2: TE4/0/2 "TE4XXP (PCI) Card 0 Span 2"
group=0,12
context=from-extern
switchtype = euroisdn
signalling = pri_cpe
channel => 32-46,48-62

; PBX link #1
; Span 3: TE4/0/3 "TE2XXP (PCI) Card 0 Span 3"
group=2,13
context=from-pabx     ; special context for PBX incoming calls
overlapdial=incoming  ; overlapdial activation
switchtype = euroisdn
signalling = pri_net  ; behave as the NET termination
channel => 63-77,79-93

; PBX link #2
; Span 4: TE4/0/4 "T4XXP (PCI) Card 0 Span 4"
group=2,14
context=from-pabx     ; special context for PBX incoming calls
overlapdial=incoming  ; overlapdial activation
switchtype = euroisdn
signalling = pri_net  ; behave as the NET termination
channel => 94-108,110-124

Passthru function¶

Route PBX incoming calls¶

We first need to create a route for calls coming from the PBX

# Create a file named pbx.conf in the directory /etc/asterisk/extensions_extra.d/, # Add the following lines in the file:

[from-pabx]
exten = _X.,1,NoOp(### Call from PBX ${CARLLERID(num)} towards ${EXTEN} ###)
exten = _X.,n,Goto(default,${EXTEN},1)

This dialplan routes incoming calls from the PBX in the default context of Wazo. It enables call from the PBX : * towards a SIP phone (in default context) * towards outgoing destniation (via the to-extern context included in default context)

Create the to-pabx context¶

Create a context named to-pabx:

POST /contexts {"name": "to-pabx", "type": "outcall"}

Route incoming calls to PBX¶

In our example, incoming calls on spans 1 and 2 (spans plugged to the provider) are routed by from-extern context. We are going to create a default route to redirect incoming calls to the PBX.

POST /extensions {"exten": "_XXXX", "context": "from-extern"} (according to the number of digits sent by the provider)
POST /incalls {"destination": {"type": "customiz", "command": "Goto(to-pabx,${XIVO_DSTNUM},1)}}
PUT /incalls/{incall_id}/extensions/{extension_id}

Create the interconnections¶

You have to create two interconnections :

provider side : dahdi/g0
PBX side : dahdi/g2

The first interconnection :

POST /trunks {'name': "t2-operatoeur", "context": "to-extern"}
POST /endpoints/custom {"interface": "dahdi/g0"}
PUT /trunks/{trunk_id}/endpoints/custom/{custom_id}

The second interconnection :

POST /trunks {"name": "t2-pabx", "context": "to-pabx"}
POST /endpoints/custom {"interface": "dahdi/g2"}
PUT /trunks/{trunk_id}/endpoints/custom/{custom_id}

Create outgoing calls¶

You must create two rules of outgoing calls:

Redirect calls to the PBX :

POST /outcalls {"name": "fsc-pabx"}
PUT /outcalls/{outcall_id}/trunks
POST /extensions {"exten": "_XXXX", "context": "to-pabx"}
PUT /outcalls/{outcall_id}/extensions/{extension_id}

Create a rule “fsc-operateur”:

POST /outcalls {"name": "fsc-operateur"}
PUT /outcalls/{outcall_id}/trunks
POST /extensions {"exten": "_X.", "context": "to-extern"}
PUT /outcalls/{outcall_id}/extensions/{extension_id}