Re: [dnssd] SRP Update - removing individual services (draft-ietf-dnssd-srp-06)

[Kangping Dong <[e-mail]>]

Sorry, another question :)

In section 2.3.1. Validation of Adds
<https://www.ietf.org/archive/id/draft-ietf-dnssd-srp-07.html#name-validation-of-adds>,
we have:

 SRP Updates consist of a set of *instructions* that together add or remove
> one or more services.

Each instruction consists either of a single add, a single delete, or a
> delete optionally followed by an add.

When an instruction contains a delete and an add, the delete MUST precede
> the add.


What is the use case of the "single add"? To my understanding,  the "delete
+ add" pattern is
for resetting the service to our current SRP update. So the "single add"
pattern is for updating
the existing service, for example, adding one more AAAA RR, right?

I think, for most SRP clients, it will be more convenient for them to track
all IP Addresses and
always update with the whole IP addresses list rather than depending on
this "update" model
and register the addresses separately. The server, I think can also be
simplified. Thoughts?

Another issue with this sentence is that, the Service & Host Description
Invalidation requires:

> exactly one "Delete all RRsets from a name" RR,

Seems disallowing the "single add" pattern?

BRs,
Kangping

On Sat, Dec 19, 2020 at 11:11 PM Kangping Dong <[e-mail]> wrote:

> Hi Ted,
>
> Thanks for creating the 07 draft so quickly! The change overall looks good
> to me and I agree we should check the KEY RR rather than the SRV RR.
>
> I have some questions when reading the related sections:
>
> 1. in 2.2.5.5.2. Removing some published services
> <https://www.ietf.org/archive/id/draft-ietf-dnssd-srp-07.html#section-2.2.5.5.2>,
> we have:
>
>> The second alternative is to send a normal SRP update, but as in the
>> first alternative,
>
> including a Service Discovery Instruction and a Service Description that
>> *delete* the service being removed.
>
> Should the "*delete*" be "*replace*"?
>
> 2. What's the use case of supporting multiple TXT RRs?
> in section *2.3.1.2. Service Description Instruction
> <https://www.ietf.org/archive/id/draft-ietf-dnssd-srp-07.html#name-service-description-instruc>*,
> we have:
>
>> zero or more "Add to an RRset" TXT RRs,
>>
>
> Are there real use cases that we need more than one TXT RRs? What is the
> expected behavior
> for the advertising proxy to publish this service with multiple TXT RRs?
> (I think DNS-SD requires
> a single TXT RR, is it correct?) Should multiple TXT RRs be concatenated
> to form a new TXT RR?
> If there is no such use case, should we require a single TXT RR? It will
> be easier to implement on both
> client and server side and consistent with DNS-SD. thoughts?
>
>
> BRs,
> Kangping
>
> On Sat, Dec 19, 2020 at 8:17 PM Ted Lemon <[e-mail]> wrote:
>
>> Actually, on second thought, maybe the right thing to do is check for the
>> KEY RR and not the SRV RR. If the key matches, the delete is okay. If there
>> are no records on the name, the delete is okay.
>>
>> On Dec 19, 2020, at 12:25 AM, Abtin Keshavarzian <[e-mail]>
>> wrote:
>>
>> Does it sound ok?
>>
>>
>>