Support of Multi-SIM lines in CAMARA APIs

[jgarciahospital]

To be considered as part of #273

Intro

Current CAMARA APIs based their functionality on subscriber's line identity, usually phone_number. Specifically for mobile lines, that is a suitable identity for the most of scenarios, but there is an specific case that requires analysis.

MultiSIM lines

MNOs usually offer a line enhancement that allows users to install the same phone line (same MSISDN) in multiple devices, known as MultiSIM. Even when different technical solutions are posible, the service is based on multiple SIMs (phisical or virtual) that are binded to the same main phone_number, it is, multiple IMEIs associated to the same MSISDN This approach is commonly used to enable secondary/companion devices like:

• Wearables
• Tablets
• Wi-Fi hotspots
• Backup smartphones

MultiSIM in CAMARA APIs

While certain APIs are agnostic to MultiSIM situation, since they refer to information of the proper line or even subscriber like carrier billing, KYC, OTP..., other APIs are tied to a device and require a different consideration to be managed in a MultiSIM scenario.

Just as couple of examples:

• when enabling a QoD session targeted for a MSISDN, if multiple SIMs and devices are associated to that same MSISDN, the telco need to know/decide which of those SIMs are to be affected. Behaviour need to be defined.
• when verifying the location of an MSISDN, if multiple SIMs and devices are associated to that same MSISDN, the telco need to know/decide which device's location information to retrieve, since different geographical locations can co-exist for each device associated to the same MSISDN.

Action required

Based on this scenario analysis and handled by a common aligned approach for similar cases:
CAMARA APIs need to analyze their impact when a MultiSIM scenario is handled, define a specific behaviour and adapt the API (if needed)

As example of current discussions or defined behaviours, SIM Swap already considers MultiSIM lines as part of the information that the API needs to retrieve.

[eric-murray]

For the Vodafone implementation of multi-SIM, phoneNumber is still a valid identifier for each of the secondary devices, as each SIM still has its own MSISDN (the "secondary" MSISDN). For the "primary" device (usually the smartphone), the primary and secondary MSISDNs are the same.

Whether an implementation will treat a phoneNumber as the primary or secondary MSISDN is dependent on that implementation. For the Device Identifier API, I added a statement that phoneNumber would be treated as the secondary MSISDN, which would allow retrieval of the IMEI for secondary devices without affecting the ability to retrieve the IMEI for the primary device.

For at least some other APIs, I think treating the phoneNumber as the secondary MSISDN will also work just as well, but does pose the following questions:

• How does the API consumer learn the secondary MSISDN if they do not already know it?
• Are there any implementations of multi-SIM where secondary devices do not have their own MSISDN? If so, what identifiers for secondary devices are valid in those cases?

[jgarciahospital]

Thanks @eric-murray,

Let me include one other question:

• How does the API consumer learn the secondary MSISDN if they do not already know it?
• Are there any implementations of multi-SIM where secondary devices do not have their own MSISDN? If so, what identifiers for secondary devices are valid in those cases?
• How do we manage request when primary MSISDN is included? First because user may not be aware of the rest of secondary MSISDNs (if exist), and second because applications will for sure only have the primary.

1. Either consider that the users know that primary device is exactly the device identifier they want to use.
2. Or consider that maybe the user/developer only knows the primary MSISDN, and therefore we cannot be sure that they are targeting exactly primary device and a different behaviour need to be considered for the rest of devices too.

[sachinvodafone]

for MultiSim definition clarification, just checking whether we are considering multi-SIM as a scenario where both devices have separate MSISDNs under one account (i.e., the primary device has its own MSISDN, and each secondary device has its own distinct MSISDN), allowing each device to operate independently without sharing call/message capabilities?

Or, are we considering scenarios where secondary devices share the same MSISDN as the primary device, meaning all devices are linked to the same number under the same account, enabling users to receive calls and messages on any of the devices?

[jlurien]

It's the second one @sachinvodafone, several SIMs (IMSI) linked (publicly) to the same MSISDN. Implementations may assign internally a secondary MSISDN to each SIM, for network operation, but in general customers are not aware of this secondary MSISDN.