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

[Ted Lemon <[e-mail]>]

On Dec 19, 2020, at 10:11 AM, Kangping Dong <[e-mail]> wrote:
> 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"? 

Delete is a type of DNS update. There is no “replace” in a DNS update. If you want to replace an RR on a name, you first delete the current version, and then add the new version. I have updated the text to make this clear.

> 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?

It’s relatively unusual, but we have to support it—SRP is not just for IoT use cases, where I agree that multiple TXT records are unlikely. See https://tools.ietf.org/html/rfc6763#section-6.8

I’ve submitted an update that contains new text to address the delete/replace concern.

The IETF datatracker status page for this draft is:
https://datatracker.ietf.org/doc/draft-ietf-dnssd-srp/ <https://datatracker.ietf.org/doc/draft-ietf-dnssd-srp/>

There is also an HTML version available at:
https://www.ietf.org/archive/id/draft-ietf-dnssd-srp-08.html <https://www.ietf.org/archive/id/draft-ietf-dnssd-srp-08.html>

A diff from the previous version is available at:
https://www.ietf.org/rfcdiff?url2=draft-ietf-dnssd-srp-08 <https://www.ietf.org/rfcdiff?url2=draft-ietf-dnssd-srp-08>