The outbound calls routing from customer SIP endpoint to carrier partner networks is determined by routing rule tables. These rules allow you to define for the number called and the number calling which rules to use and in which order !

Explanation of notions

In order to understand the documentation, it is necessary to explain the basic concepts used:

• Routing table : logical group grouping a set of rules to determine the operator (s) to end the call.
• Routing rule : rule defining for a given destination an ordered list of operators to use.
• Destination : represents the destination determined by the longest prefix of the called number. For example, * France Orange Mobile *.
• Routing Type : Determines how to distribute calls between a list of providers
• Rate grid : groups together a tariff set for a given destination

Routing logic

An outgoing call from the PyFreeBilling platform to the outside world follows the following logic:

• 1: normalization of called and calling numbers to conform to E.164 without the +
• 2: from the client ID, the routing table to use is retrieved
• 3: search in the routing table, the corresponding rules by category. Each category is inspected in the following order: prefix, destination, country and type, country, region and type, region, and then the default routing category.
• 4: as soon as in a given category, a corresponding rule is found (several rules in the same category can match), the search stops
• 5: a list of tariffs of suppliers is recovered. This list is ordered according to the type of routing: the cheapest cost, the quality, the priority or the weight
• 6: From this list of supplier tariffs, a list of gateways is constructed and ordered according to the type of routing
• 7: the parameters related to the gateways (codec, prefix …) are recovered
• 8: the call is then sent sequentially in case of error to the gateways of the list
• 9: at each attempt and at the end of the call, the SIP messages are archived to facilitate the search for anomaly and the calculation of statistics

Examples of routing rules

A routing table includes one or more routing rules. The basic routing table includes a single rule of type “default”.

Rule “default”

In our example, we chose a rule type based on the cheapest cost (LCR). Weight and priority do not matter. We have in our example tariff grids called “OBS” and “BT” (we can quite rightly think that they refer to the eponymous operators). We have for “OBS” 2 gateways and for “BT” a defined one (it is quite possible that for “BT” several gateways are defined, but for specific reasons, we only want to use “BT1”).

Since the rule is “default “, all calls will use it.

Rule “destination”

Now, I want to route the calls from the destination “France Mobile SFR” to my interconnection with SFR. For that, I’m going to create a destination rule in addition to my previous rule. This gives us the following 2 tables:

Rule “destination”:

Rule “default “:

How is the routing table determined?

The routing table is assigned to the customer account. Thus, upon receipt of an outgoing call from a client SIP account, the system retrieves the identifier of the routing table to be used.
A routing table can be assigned to multiple clients, but in this case a modification of the latter will have an impact on all the clients using this table.

What are the different rule categories?

Categories are listed in order of priority of analysis (from the most accurate to the most general):

• prefix
• destination
• country and type
• country
• region and type
• region
• the default routing category

What are the search criteria for a rule?

First, the rules are analyzed in order of categories. In each category, the system will determine which rules correspond to the calling number: for the category “prefix”, the rules with the longest prefix will be retained, for the category “destination”, the rules with the corresponding category will be withholdings … and so on.
Then, for each rule obtained, the following points are analyzed:

• the status of the rule: the rule should not be disabled
• the purchase price to the supplier must be lower than the selling price to our client (unless we have authorized the sale at a loss in the price list of our client)
• the calling number must not be part of the list of excluded numbers (this allows the use of tariff grids from the same supplier according to the calling number and therefore to apply different purchase prices). This rule is managed at the level of the supplier’s fee schedule.

What are the statuses of a routing rule?

A routing rule can have 3 statuses:

• active: the rule can be used for the routing decision
• inactive: the rule is disabled and can not be used for the routing decision
• blocked: the rule thus defined blocks the routing of the call and terminates it.

Be careful, only define a “blocked” rule, or all rules in the same category for a given destination must be on “blocked”. If an “active” rule exists, calls will be routed. This allows you to block a route, for example calls to satellites.

What are the routing criteria between the selected suppliers?

The routing criteria are as follows:

• the lowest cost (LCR): the cheapest operator will be tested first, in case of failure, the next cheapest will be tested and so on
• by priority: the operator with the highest priority (1) will be tested first
• by weight: a destination has several rules with the same priority: the weight will divide the calls according to the desired ration
• by quality: at a supplier price scale, a grade of 10 corresponding to the quality is assigned by the administrator (10 being the highest value). The operator with the highest fee schedule will be tested first.

It is interesting to note that the use of the “quality” criterion makes it possible to manage the routing of calls between two different price grids of the same provider: for example, it is possible to route the calls via the GOLD grid. then priority to the SILVER grid in case of failure (we can imagine a limitation of capacity for example). In the case of routing according to the criterion “the cheapest cost”, the SILVER grid will be tested before the GOLD grid!

How is the list of gateways to be determined?

A routing rule is used to link a supplier fee schedule with a routing table. It is possible to define in this rule the gateways of our provider to use: all or just a few.
The distribution of calls between the selected gateways of our provider will be balanced.