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6. Routing Configuration

The following sections in the config file can be used to configure how calls are routed.

Each call gets passed down a chain of routing policies. Each policy may route the call and terminate the chain or modify it and pass it on. You can use the setting in the following sections to specify which policies to use and modify their behavior.

6.1 Section [RoutingPolicy]

This section explains how the various possible routing policies within the gatekeeper work.

The incoming call requests can be routed using a number of routing providers:

Default configuration for routing policies is as follows:

[RoutingPolicy]
default=explicit,internal,parent,neighbor

If one policy does not match, the next policy is tried.

These policies can be applied to a number of routing request types, and routing input data. The different types are: ARQ, LRQ, Setup and Facility (with the callForwarded reason) There is also the general routing policy, which is kind of a default for the other types.

Example:

[RoutingPolicy]
h323_ID=dns,internal
002=neighbor,internal
Default=internal,neighbor,parent

When one of the messages is received which calls for a routing decision, all calls to an alias of the h323_ID type will be resolved using DNS. If DNS fails to resolve the alias, it is matched against the internal registration table. If a call is requested to an alias starting with 002, first the neighbors are checked and then the internal registration table. If the requested alias is not an h323_ID or an alias starting with 002, the default policy is used by querying the internal registration table, then the neighbors, and if that fails the parent.

For the ARQ, LRQ, Setup and Facility messages one would use the [RoutingPolicy::OnARQ], [RoutingPolicy::OnLRQ], [RoutingPolicy::OnSetup] and [RoutingPolicy::OnFacility] sections using the syntax explained above.

Example:

[RoutingPolicy::OnARQ]
default=numberanalysis,internal,neighbor

A typical ENUM routing setup would look like this:

Example:

[RoutingPolicy]
default=explicit,internal,enum,dns,internal,parent,neighbor

6.2 Section [RasSrv::RewriteE164]

This section defines the rewriting rules for dialedDigits (E.164 number).

Format:

[!]original-prefix=target-prefix

If the number is beginning with original-prefix, it is rewritten to target-prefix. If the `!' flag precedes the original-prefix, the sense is inverted and the target-prefix is prepended to the dialed number. Special wildcard characters ('.' and '%') are available.

Example:

08=18888

If you dial 08345718, it is rewritten to 18888345718.

Example:

!08=18888

If you dial 09345718, it is rewritten to 1888809345718.

Option:

6.3 Section [RasSrv::RewriteAlias]

This section defines the rewriting rules for aliases. This can be used to map gatekeeper assigned aliases to registered endpoints.

Format:

[!]original-alias=target-alias

If the alias is original-alias, it is rewritten to target-alias.

Example:

bill=033123456

6.4 Section [RasSrv::GWRewriteE164]

This section describes rewriting the dialedDigits E.164 number depending on the gateway a call has come from or is being sent to. This allows for more flexible manipulation of the dialedDigits for routing etc. In combination with the RasSrv::RewriteE164 you can have triple stage rewriting:

Call from "gw1", dialedDigits 0867822
                |
                |
                V
Input rules for "gw1", dialedDigits now 550867822
                |
                |
                V
Global rules, dialedDigits now 440867822
                |
                |
                V
Gateway selection, dialedDigits now 440867822, outbound gateway "gw2"
                |
                |
                V
Output rules for "gw2", dialedDigits now 0867822
                |
                |
                V
Call to "gw2", dialedDigits 0867822

Format:

gw-alias=in|out=[!]original-prefix=target-prefix[;in|out...]

If the call matches the gateway, the direction and begins with original-prefix it is rewritten to target-prefix. If the `!' flag precedes the original-prefix, the sense is inverted. Special wildcard characters ('.' and '%') are available. Multiple rules for the same gateway should be separated by ';'.

Example:

gw1=in=123=321

If a call is received from "gw1" to 12377897, it is rewritten to 32177897 before further action is taken.

6.5 Section [Endpoint::RewriteE164]

Once you specify prefix(es) for your gatekeeper endpoint, the parent gatekeeper will route calls with dialedDigits beginning with that prefixes. The child gatekeeper can rewrite the destination according to the rules specified in this section. By contrast, when an internal endpoint calls an endpoint registered to the parent gatekeeper, the source will be rewritten reversely.

Format:

external prefix=internal prefix

For example, if you have the following configuration,

                        [Parent GK]
                        ID=CitronGK
                        /         \
                       /           \
                      /             \
                     /               \
                [Child GK]          [EP3]
                ID=ProxyGK          E164=18888200
                Prefix=188886
                /       \
               /         \
              /           \
           [EP1]         [EP2]
           E164=601      E164=602

With this rule: 

188886=6

When EP1 calls EP3 by 18888200, the CallingPartyNumber in the Q.931 Setup will be rewritten to 18888601. Conversely, EP3 can reach EP1 and EP2 by calling 18888601 and 18888602, respectively. In consequence, an endpoint registered to the child GK with prefix '6' will appear as an endpoint with prefix '188886', for endpoints registered to the parent gatekeeper.

The section does not relate to the section RasSrv::RewriteE164, though the later will take effect first.

6.6 Section [Routing::Sql]

Rewrite the called alias with an SQL query. Supports routing OnARQ, OnLRQ and OnSetup.

If the string returned from the database is 'REJECT' (upper or lower case), the call is rejected. If the string matches a dotted IP address, it is taken as destination IP and else it is treated as new destination alias. If 2 colums are returned, the first is treated as the new destination alias and the second is treated as new destination IP.

If the database returns nothing, the call is passed on unchanged.

6.7 Section [Routing::NumberAnalysis]

This section defines rules for the numberanalysis routing policy. The policy checks a dialed number for minimum and/or maximum number of digits and sends ARJ, if necessary (number of digits is out of range), to support overlapped digit sending. It also partially supports Setup messages (no overlapped sending - only number length validation).

Format:

prefix=MIN_DIGITS[:MAX_DIGITS]

If the number matches the prefix, it is verified to consist of at least MIN_DIGITS digits and (if MAX_DIGITS is present) at most MAX_DIGITS digits. Special wildcard characters (!, '.' and '%') are available. If the number is too short, an ARJ is send with rejectReason set to incompleteAddress. If the number is too long, an ARJ is send with rejectReason set to undefinedReason. Prefix list is searched from the longest to the shortest prefix for a match. For Setup messages, a Release Complete with "badFormatAddress" is sent when the number has an incorrect length.

Example:

[RoutingPolicy::OnARQ]
default=numberanalysis,internal

[Routing::NumberAnalysis]
0048=12
48=10
.=6:20

Calls to destinations starting with 0048 require at least 12 digits, to 48 - 10 digits and to all other at least 6 and at most 20 digits.

6.8 Section [RewriteCLI]

This section contains a set of rewrite rules for ANI/CLI numbers (caller id). The rewrite process is done at two stages - inbound rewrite and outbound rewrite. The inbound rewrite is done before any other Q.931 Setup message processing (like inbound GWRewrite, authentication, accounting, ...) and it will have visible effect inside auth/acct modules, as it affects Calling-Station-Id. The outbound rewrite takes place just before the Setup message is to be forwarded and its effect is visible only to the callee.

An inbound rewrite rule can be matched by a caller's IP and a dialed number or an original CLI/ANI. An outbound rewrite rule can be matched by a caller's IP, callee's IP and a dialed number or a destination number (the dialed number after rewrite) or a CLI/ANI (after inbound rewrite).

This module also provides CLIR (Calling Line Identification Restriction) feature that can be configured for each endpoint (rule).

Format for an inbound rule:

in:CALLER_IP=[pi=[allow|restrict][,forward|apply|applyforterminals]] [cli:|dno:]number_prefix(=|*=|~=)NEW_CLI[,NEW_CLI]...

The in: prefix tells that this is an inbound rule and the CALLER_IP will be used to match the rule (it can be a single IP or a whole subnet).

The optional pi= parameter controls CLIR (Calling Line Identification Restriction) features. Specifying either allow or restrict forces presentation indicator to be set to "presentation allowed" or "presentation restricted". forward, apply and applyforterminals controls how the received (if any) presentation indicator is processed by the gatekeeper. forward means just to forward it to the callee as is, apply means hiding CLI if the PI is set to "presentation restricted", applyforterminals is similar to apply, except that CLI is hidden only when sending the call to a terminal, not a gateway.

The prefix cli: or dno: (the default) selects what number will be used to match the number_prefix - a caller id (CLI/ANI) or a dialed number. Number matching/rewriting can be done in three ways:

After the equality (=/ =/*=) sign, there follows a list of new CLI values to be used. If more than one value is specified, a one will be chosen on a random basis. It's possible to specify whole number ranges, like 49173600000-49173699999 (for number ranges CLIs should have a fixed length). There is a special string constant "any", that can be used in place of the CALLER_IP or the number_prefix. To enable CLIR for this rule, use a special string constant "hide" instead of the list of new CLI values. Note that CLIR is far more useful for outbound rules.

Example 1:

[RewriteCLI]
in:192.168.1.1=dno:5551=3003
in:192.168.1.1=cli:1001=2222
in:192.168.1.1=any=1111

These rules tell that for calls from the IP 192.168.1.1: 1) if the user dialed a number beginning with 5551, set CLI to 3003, 2) if the call is from user with CLI beginning with 1001, set CLI to 2222, 3) for other calls from this IP, set CLI to 1111.

Example 2:

[RewriteCLI]
in:192.168.1.0/24=any=18001111
in:192.168.2.0/24=any=18002222
in:any=any=0

These rules tell that: 1) for calls from the network 192.168.1.0/24, set CLI to 18001111, 2) for calls from the network 192.168.2.0/24, set CLI to 18002222, 3) for other calls, set CLI to 0.

Example 3:

[RewriteCLI]
%r1% in:192.168.1.0/24=0048*=48
%r2% in:192.168.1.0/24=0*=48
in:any=100.~=48900900900

These rules tell that: 1) for calls from the network 192.168.1.0/24, rewrite 0048 to 48 (example - 0048900900900 => 48900900900), 2) for other calls from the network 192.168.1.0/24, rewrite 0 to 48 (example - 0900900900 => 48900900900), 3) for other calls, if CLI is 4 digits and starts with 100, set it to 48900900900.

Example 4 (CLIR):

[RewriteCLI]
in:192.168.1.0/24=any=hide

This example causes caller's number to be removed from Setup messages originating from the 192.168.1.0/24 network. It also causes proper presentation and screening indicators to be set in Setup messages.

Format for an outbound rule:

out:CALLER_IP=CALLEE_IP [pi=[allow|restrict][,forward|apply|applyforterminals]] [cli:|dno:|cno:]number_prefix(=|~=|*=)NEW_CLI[,NEW_CLI]...

The out: prefix tells that this is an outbound rule, the CALLER_IP and the CALLEE_IP will be used to match the rule and can be a single IP or a whole network address.

The optional pi= parameter controls CLIR (Calling Line Identification Restriction) features. Specifying either allow or restrict forces presentation indicator to be set to "presentation allowed" or "presentation restricted". forward, apply and applyforterminals controls how the received (if any) presentation indicator is processed by the gatekeeper. forward means just to forward it to the callee as is, apply means hiding CLI if the PI is set to "presentation restricted", applyforterminals is similar to apply, except that CLI is hidden only when sending the call to a terminal, not a gateway.

The prefix cli:, dno: (the default) or cno: selects what number will be used to match the number_prefix - a caller id (CLI/ANI), a dialed number or a destination/called number (the dialed number after rewrite). Number matching/rewriting can be done in three ways:

After the equality sign (=/ =/*=), a list of new CLI values to be used follows. If more than one value is specified, a one will be chosen on a random basis. It's possible to specify whole number ranges, like 49173600000-49173699999. There is a special string constant "any", that can be used in place of the CALLER_IP, the CALLEE_IP or the number_prefix. To enable CLIR for this rule, use a special string constant "hide" or "hidefromterminals" instead of the list of new CLI values.

Example 1:

[RewriteCLI]
out:any=192.168.1.1 any=1001
out:any=192.168.1.2 any=1002

These rules set a fixed ANI/CLI for each terminating IP: 1) present myself with ANI 1001, when sending calls to IP 192.168.1.1, 2) present myself with ANI 1002, when sending calls to IP 192.168.1.2.

Example 2:

[RewriteCLI]
out:any=192.168.1.1 any=1001-1999,3001-3999

This rule randomly selects ANI/CLI from range 1001-1999, 3001-3999 for calls sent to 192.168.1.1.

Example 3 (CLIR):

[RewriteCLI]
out:any=any any=hidefromterminals
out:192.168.1.1=any any=hide

In this example each subscriber has enabled CLIR. So all calls to terminals will have a caller's number removed and presentation/screening indicators set. Calls to gateways will have only a presentation indicator set to "presentation restricted" and the caller's number will not be removed to allow proper call routing and number removal at the destination equipment.
One exception to these rules are calls from 192.168.1.1 which will have a caller's number always removed, no matter whether calling a terminal or a gateway.

Example 4 (CLIP):

[RewriteCLI]
out:any=192.168.1.1 any=hide

In this example CLIP (Calling Line Identification Presentation) feature is disabled for the user 192.168.1.1.

Example 5 (CLIR):

[RewriteCLI]
out:192.168.1.1=any pi=restrict,apply cli:.*=.
out:any=any pi=allow cli:.*=.

These rules do not change CLI (.*=.) and: 1) enable CLIR for an endpoint 192.168.1.1. apply tells the gatekeeper to not only set the PI, but also to hide the number actually, 2) force CLI presentation for other endpoints.

Rule matching process has a strictly defined order:

  1. the closest caller's IP match is determined (closest means with the longest network mask - single IPs have the highest priority, "any" has the lowest priority),
  2. (outbound rules) the closest callee's IP match is determined,
  3. the longest matching prefix/number is searched for the given IP/IP pair in the following order:
    1. dno: type (dialed number) rules are searched,
    2. cno: type (destination/called number) rules are searched,
    3. cli: type (caller id) rules are searched.
After a match for caller's/caller's IP is found, no more rules are checked, even if no prefix/number is matched inside the set of rules for these IPs.

On Windows platform, there is a problem with duplicated config keys, so there is a workaround for this restriction. This example will not work because of the same key (in:192.168.1.1): 

[RewriteCLI]
in:192.168.1.1=1001=2001
in:192.168.1.1=any=2000
As workaround, you can use a string with percent signs (%) at the beginning and at the end before the key. This prefix will be automatically stripped from the key name before loading rules: 
[RewriteCLI]
%r1% in:192.168.1.1=1001=2001
%r2% in:192.168.1.1=any=2000

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