Off-net Calling with BGCF and IBCF¶

The Clearwater IBCF (Interconnection Border Control Function) provides an interface point between a Clearwater deployment and one or more trusted SIP trunks.

The IBCF does not currently provide all of the functions of an IMS compliant IBCF - in particular it does not support topology hiding or an H.248 interface to control a Transition Gateway.

To use the IBCF function you must install and configure at least one IBCF node, set up the ENUM configuration appropriately, and set up BGCF (Breakout Gateway Control Function) routing configuration on the Sprout nodes.

Install and Configure an IBCF¶

Install and configure an IBCF node with the following steps.

Install the node as if installing a Bono node, either manually or using Chef. If using Chef, use the ibcf role, for example
```
knife box create -E <name> ibcf
```
Edit the /etc/clearwater/user_settings file (creating it if it does not already exist) and add or update the line defining the IP addresses of SIP trunk peer nodes.
```
trusted_peers="<trunk 1 IP address>,<trunk 2 IP address>,<trunk 3 IP address>, ..."
```

Restart the Bono daemon.

service stop bono (allow monit to restart Bono)

ENUM Configuration¶

The number ranges that should be routed over the SIP trunk must be set up in the ENUM configuration to map to a SIP URI owned by the SIP trunk provider, and routable to that provider. For example, you would normally want to map a dialed number to a URI of the form <number>@<domain>.

This can either be achieved by defining rules for each number range you want to route over the trunk, for example

*.0.1.5 IN NAPTR 1 1 "u" "E2U+sip" "!(^.*$)!sip:\\1@<trunk IP address>!" .
*.0.1.5.1 IN NAPTR 1 1 "u" "E2U+sip" "!(^.*$)!sip:\\1@<trunk IP address>!" .

or by defining a default mapping to the trunk and exceptions for number ranges you want to keep on-net, for example

* IN NAPTR 1 1 "u" "E2U+sip" "!(^.*$)!sip:\\1@<trunk IP address>!" .
*.3.2.1.2.4.2 IN NAPTR 1 1 "u" "E2U+sip" "!(^.*$)!sip:\\1@<local domain>!" .
*.3.2.1.2.4.2.1 IN NAPTR 1 1 "u" "E2U+sip" "!(^.*$)!sip:\\1@<local domain>!" .

You can also use ENUM to provide number portability information, for example

*.3.2.1.2.4.2 IN NAPTR 1 1 "u" "E2U+pstn:tel" "!(^.*$)!sip:\\1;npdi;rn=+242123@<local domain>!" .
*.3.2.1.2.4.2.1 IN NAPTR 1 1 "u" "E2U+pstn:tel" "!(^.*$)!sip:\\1;npdi@<local domain>!" .

Refer to the ENUM guide for more about how to configure ENUM.

BGCF Configuration¶

BGCF (Border Gateway Control Function) configuration is stored in the bgcf.json file in /etc/clearwater on each sprout node (both I- and S-CSCF). The file stores two types of mappings. This first maps from SIP trunk IP addresses and/or host names to IBCF host names, and the second maps from a routing number (using prefix matching) to IBCF host names. These mappings control which IBCF nodes are used to route to a particular destination. Each entry can only apply to one type of mapping.

Multiple nodes to route to can be specified. In this case, Route headers are added to the message such that it is sent to the first node and the first node sends it to the second node and so on; the message is not tried at the second node if it fails at the first node.

The file is in JSON format, for example.

{
    "routes" : [
        {   "name" : "<route 1 descriptive name>",
            "domain" : "<SIP trunk IP address or host name>",
            "route" : ["<IBCF SIP URI>"]
        },
        {   "name" : "<route 2 descriptive name>",
            "domain" : "<SIP trunk IP address or host name>",
            "route" : ["<IBCF SIP URI>", "<IBCF SIP URI>"]
        },
        {   "name" : "<route 3 descriptive name>",
            "number" : "<Routing number>",
            "route" : ["<IBCF SIP URI>", "<IBCF SIP URI>"]
        }
    ]
}

There can be only one route set for any given SIP trunk IP address or host name. If there are multiple routes with the same destination IP address or host name, only the first will be used. Likewise, there can only be one route set for any given routing number; if there are multiple routes with the same routing number only the first will be used.

A default route set can be configured by having an entry where the domain is set to "*". This will be used by the BGCF if it is trying to route based on the the domain and there’s no explicit match for the domain in the configuration.

There is no default route set if the BGCF is routing based on the routing number provided.

After making a change to this file you should run sudo /usr/share/clearwater/clearwater-config-manager/scripts/upload_bgcf_json to ensure the change is synchronized to other Sprout nodes on your system (including nodes added in the future).