SIP Attended Call Transfer In Cluster

Latest revision as of 11:00, 4 November 2013

This page documents how to configure Yate to handle a SIP attended call transfer for an unknown call leg in the cluster node.
If the SIP module can't find the call in its list, it will try to route and execute the transfer request.

Below are the steps to follow.

[edit] Enable REFER method handler in the SIP module

ysipchan.conf

[general]
;Allow handling the REFER message to perform transfers
transfer=yes

[edit] Enable and configure clustering

REMEMBER: It is mandatory to choose node names that can be easily resolved to an IP address.
The SIP call to another cluster will fail if its name can't be resolved.
See also Node Name and clustering.

Set node name

yate.conf

[general]
;Name of this node in a cluster
nodename=somehost

[edit] Enable and configure the clustering module

clustering.conf

[general]
;Regular expression describing node name match rules
regexp=^[[:alnum:].-]\+$
;Template for forwarding the call to target node
callto=sip/sip:cluster/${called}@\0

[edit] Enable and configure the line tracker

The line tracker is used to maintain the list of call legs in the database.
The example below assumes the existence of a 'cluster' account in a database module containing a 'lines' table with the following text columns: 'nodeprefix','chan','callid','nodename'. The database can be configured in mysqldb.conf or pgsqldb.conf
See also register.

register.conf

[general]
;Activate line status tracking on "call.cdr"
linetracker=yes

[linetracker]
; Queries for the line usage tracker
account=cluster
initquery=DELETE FROM lines WHERE nodename='${nodename}'
cdr_initialize=INSERT INTO lines(nodeprefix,chan,callid,nodename)\
VALUES('${nodeprefix}', '${chan}', '${callid}', '${nodename}')
cdr_finalize=DELETE FROM lines WHERE nodeprefix='${nodeprefix}' AND chan='${chan}'
cdr_update=UPDATE lines SET callid='${callid}' WHERE nodeprefix='${nodeprefix}' AND chan='${chan}'

[edit] Route transfer requests using the line tracker

The example below returns a cluster pickup target.

register.conf

[general]
;Activate handler on the "call.route" message
call.route=yes

[call.route]
; Query and result name for the routing message
account=cluster
query=SELECT nodeprefix || 'pickup/' || chan AS location FROM routes WHERE callid='${callid}' AND '${reason}'='transfer'
result=location

[edit] Configure cdrbuild to copy extra parameter(s)

We need the cdrbuild module to update and forward the callid parameter.
The callid parameter is added by the SIP module.
It is built from SIP dialog data ('Call-ID', 'From' tag, 'To' tag).

cdrbuild.conf

[parameters]
;added parameter callid to be monitorized, will appear in "call.cdr"
callid=true

See also

• Register
• Clustering
• CDR Build Module
• SIP Configuration File
• Telephony