Master DNL Class4
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Introduction

Class 4 Fusion supports different kinds of configuration Stir Shaken configuration.
  1. 1.
    If you are already an iconnectiv certified SP, then you can use the built-in AS/VS within Class 4
  2. 2.
    If you are not an existing iconnectiv certified SP, you can use an external AS/VS service to sign and verify your calls.
  3. 3.
    If you just simply want to bypass stir shaken signature from ingress to egress, you can configure Class 4 to block calls that don't have valid stir shaken signature. This setting can be done on a per ingress trunk basis.

STIR/SHAKEN

I. Validating incoming requests

STIR/SHAKEN Identity is a JWT with encoded origination ANI and DNIS, signed by a certified STIR/SHAKEN Service Provider, included into the INVITE request.
Ingress and egress trunks may put requirements on incoming and outgoing INVITE requests respectively, using resource.shaken_vfy_policy parameter: 0 - Do not check STIR/SHAKEN Identity; 1 - Require STIR/SHAKEN Identity; 2 - Require valid STIR/SHAKEN Identity; 3 - Require STIR/SHAKEN Identity; Try to validate, but bypass if failed.
If the inbound INVITE request does not satisfy ingress verification policy, the call should be blocked with the corresponding reason:
Release cause | SIP code | Reason
------------------------------------------------------------------------------------------------------------
71 | 428 - Use Identity header | Ingress requires STIR/SHAKEN Identity
72 | 438 - Invalid Identity Header | Call blocked due to invalid STIR/SHAKEN Identity signature
Another set of codes represents errors in the STIR/SHAKEN module, which prevent ingress trunk from validating the Identity:
Release cause | SIP code | Reason
-------------------------------------------------------------------------------------
73 | 503 - Service Unavailable | All SHAKEN providers failed
74 | 503 - Service Unavailable | No SHAKEN providers configured
75 | 503 - Service Unavailable | General error in the STIR/SHAKEN module

II. Signing outgoing requests

  1. 1.
    STIR/SHAKEN identity creation
Switch can create STIR/SHAKEN Identity when placing the outbound INVITE, if caller did not provide it. Ingress trunk can regulate the conditions on which switch can generate Identity for the call, using resource.shaken_sign_policy parameter: 0 - Do not sign calls; 1 - Sign call, if ANI is a US numbers; 2 - Sign, if ANI is a valid phone number (do not allow URI as ANI); 3 - Sign, if ANI is in the SHAKEN ANI pool.
Since class4 switch has options to alter, replace or randomize ANI, final ANI/DNIS may not match numbers in the original Identity provided by the caller. In such scenarios, switch may re-create Identity using the new ANI and DNIS. This behavior is controlled by resource.shaken_allow_resign flag in the ingress trunk configuration. NOTE: New identity creation is allowed only due to ANI/DNIS mismatch. Switch cannot re-sign call, if STIR/SHAKEN Identity did not pass validation.
  1. 1.
    ANI pools and attestation levels
STIR/SHAKEN Identity contains a trust level for the call (attestation level): A - Full attestation B - Partial Attestation C - Gateway Attestation
Client may control attestation levels for each ANI, using SHAKEN ANI groups. Attestation level for numbers outside of the pool can be set with resource.shaken_default_attest_lvl ingress parameter.
  1. 1.
    SHAKEN ANI pool creation
Create SHAKEN ANI group:
INSERT INTO shaken_ani_group (name) VALUES ('my test group') RETURNING id;
Populate ANI group:
INSERT INTO shaken_ani_group_rel (group_id, did) VALUES (<shaken_ani_group.id>, <number>);
Create ANI pool (list of groups):
INSERT INTO shaken_ani_group_list (name) VALUES ('Trunk X ANI pool') RETURNING id;
Add created ANI group to the pool, defining the attestation level:
INSERT INTO shaken_ani_group_list_rel (ani_group_list_id, ani_group_id, attest_lvl) VALUES (<shaken_ani_group_list.id>, <shaken_ani_group.id>, 'B');
Assign SHAKEN ANI pool ID to the ingress trunk, using resource.shaken_ani_group_list_id parameter.
ANI groups and/or pools may be shared between different resources freely.

III. Routing

Egress trunks may put requirements on STIR/SHAKEN Identity using resource.shaken_vfy_policy parameter (see above). If verification policy cannot be satisfied, egress trunk should be removed from routing with the corresponding cause:
Egress cause | Reason
----------------------------------------------------------------------------
62 | Egress requires STIR/SHAKEN Identity
63 | Provided STIR/SHAKEN Identity is not valid
64 | All SHAKEN providers failed
65 | No SHAKEN providers configured
66 | General error in the STIR/SHAKEN module
If all egress routes failed due to STIR/SHAKEN policy, ingress shall block the call with the regular "No egress found" reason.