Can applications set different lease times for different services?

[ndyck14]

There are cases where it is important to set shorter lived lease times (e.g. _matterc._udp) vs longer lease times (e.g. _matter._tcp). It appears that you can change the lease time, but its a universal time for all services rather than tracked per service. I suppose one could adjust this just before publishing, but since lease renewal is handled by OT, that seems very likely to be problematic. Is there a known way to handle this already or is this effectively a new feature request?

openthread/include/openthread/srp_client.h

Line 385 in ccf8ea6

void otSrpClientSetLeaseInterval(otInstance *aInstance, uint32_t aInterval);

[jwhui]

As you noted, OpenThread's SRP Client currently does not really support configuring different lease times for different service instances. While the SRP protocol supports maintaining different lease times, it will require adding some additional implementation complexity to manage updating service instances that have very different lease times - it affects how we aggregate and synchronize updates to reduce the number of SRP Update interactions with the server.

@abtink , thoughts?

[ndyck14]

interesting. Yes, if the lease renew time is tracked per service, it seems fine for the application to temporarily set the lease time to shorter just before it registers a short lived service, and set it back after, at least for the specific use-case i mentioned around matterc._udp.

There may still be other cases where it could be beneficial for separate lease times tracked - but if a service is to be renewed anyway and the application is expected to continue running gracefully, it is perhaps not a near term need

[abtink]

I am looking into adding general support for this into Srp::Client as a new feature (will work on it more when I get some time).

One thing about this is that it will be a bigger behavioral change and we need to make sure it does not break any of the functionality so make sense to do a lot of testing and validation.

[abtink]

Just adding note:

• If we have multiple services with different lease times, they need to be registered separately in different SRP update message and also refreshed in separate updates.
• The lease and key lease intervals are given in Additional Section (in an Update Lease Option) in an SRP update message and therefore are applicable to everything included in the SRP update message.

[jwhui]

If we have multiple services with different lease times, they need to be registered separately in different SRP update message and also refreshed in separate updates.

I think this makes sense. We could try to align phases when the periods are multiples of each other (i.e. harmonics), but I'm not sure the additional complexity is worth the benefit.

[abtink]

Just submitted for this:

• [srp-client] new feature to allow lease and key lease per service #8211