CLI, NCLI and STIR/SHAKEN

CLI (Caller Line Identification)

If call goes out on a CLI route ( White Route ) the received party will likely see your callerID information
lawful – Termination is legal on the remote end ie abiding country’s telco infrastructure and stable
Expensive – usually with direct or via leased line (TDM) interconnections with the tier-1 carriers.

Non-CLI (Non-Caller Line Identification)

The Caller ID is not visible at the call
If call goes out on a Non-CLI route (Grey Route) goes out on a non-CLI routes they will see either a blocked call or some generic number.
Unlawful – questionable legality or maybe violating some providers AUP(Acceptable Use Policy ) on the remote end.
Cheaper – low quality , usually via VoIP-GSM gateways

STIR/SHAKEN

Secure Telephony Identity Revisited / Signature-based Handling of Asserted information using toKENs

suite of protocols and procedures intended to combat caller ID spoofing on public telephone networks.
used by robocallers to mask their identity or to make it appear the call is from a legitimate source
usually orignates from voice-over-IP (VOIP) systems

STIR system aims to add information to the SIP headers that allow the endpoints along the system to positively identify the origin of the data , such as JSON web tokens encrypted with the provider’s private key, encoded using Base64,

There are three levels of verification, or “attestation”

  • A : Full Attestation
    indicates that the provider recognizes the entire phone number as being registered with the originating subscriber.
  • B : Partial Attestation
    call originated with a known customer but the entire number cannot be verified,
  • C : Gateway Attestation
    call can only be verified as coming from a known gateway

Device Feature Key Synchronization (DFKS)

SIP SUBSCRIBE/NOTIFY mechanism to enable feature status synchronization between SIP server and SIP phone
When a supported phone powers up, it sends a SIP SUBSCRIBE request to the Application Server to establish this subscription.

SIP phone is responsble to refresh the subscription to avoid the expiration.
Application Server persists the subscriptions to its database so that they survive a restart or a switch to the secondary Application Server in a failure scenario.

BLF ( Busy Lamp Field )

indicators on a phone that indicate who is talking on other phones connected to the same PBX or Key System.
Aids in manual routing of incoming calls.
part of Class 5 services

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