Re: [dnssd] SRP: support of SRP message with zero service?

Esko Dijk <esko.dijk@iotconsultancy.nl> Wed, 07 December 2022 13:29 UTC

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From: Esko Dijk <esko.dijk@iotconsultancy.nl>
To: Ted Lemon <mellon@fugue.com>
CC: Kangping Dong <wgtdkp@google.com>, "dnssd@ietf.org" <dnssd@ietf.org>
Thread-Topic: [dnssd] SRP: support of SRP message with zero service?
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Archived-At: <https://mailarchive.ietf.org/arch/msg/dnssd/DQGJzt8trEE6ifgabSd5uxYMR-A>
Subject: Re: [dnssd] SRP: support of SRP message with zero service?
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> E.g. so you can ssh to your laptop by name.

Or, try to ssh into your light bulb by using the password “admin” – a somewhat different IoT usecase ;-)

Esko

From: Ted Lemon <mellon@fugue.com>
Sent: Wednesday, December 7, 2022 13:56
To: Esko Dijk <esko.dijk@iotconsultancy.nl>
Cc: Kangping Dong <wgtdkp@google.com>; dnssd@ietf.org
Subject: Re: [dnssd] SRP: support of SRP message with zero service?

Also bear in mind that SRP isn’t just for the constrained device use case. There may be cases where it’s useful to register a well known name and unnecessary to advertise a service. E.g. so you can ssh to your laptop by name.

Op wo 7 dec. 2022 om 07:52 schreef Esko Dijk <esko.dijk@iotconsultancy.nl<mailto:esko.dijk@iotconsultancy.nl>>
Yes we have, the link to the start of the thread is: https://mailarchive.ietf.org/arch/msg/dnssd/01voO6MkMBBvxeInncR6e-3u1bM/
(somewhat long discussion)

One use case mentioned also is an SRP client adding or removing an IP address in its registration, while keeping its services unchanged.

Esko

From: Kangping Dong <wgtdkp@google.com<mailto:wgtdkp@google.com>>
Sent: Wednesday, December 7, 2022 12:48
To: Esko Dijk <esko.dijk@iotconsultancy.nl<mailto:esko.dijk@iotconsultancy.nl>>
Cc: Ted Lemon <mellon@fugue.com<mailto:mellon@fugue.com>>; Abtin Keshavarzian <abtink@google.com<mailto:abtink@google.com>>; DNSSD <dnssd@ietf.org<mailto:dnssd@ietf.org>>; Jonathan Hui <jonhui@google.com<mailto:jonhui@google.com>>
Subject: Re: SRP: support of SRP message with zero service?

> Why is it useful to have a hostname and address generally?  :)

If the client knows only the hostname and address, it doesn't know what protocol should be used to communicate with the device, so it doesn't seem to be useful to
know only the address. One use case in my mind is that a device may register a well-known hostname, but didn't find a real case in local constraint networks...

> I recall that we discussed that a device could temporarily not have a particular service; and some expectation that in due time a service will become available again.
> During this time the device wants to keep its name registered, to show that it is still there and functional, and defend its name against potential other devices taking that name.
> So one use case is deleting its service(s) but keeping the name registered.

Will this encourage devices to always register their hostname even when they don't provide any service? Do we have a link to that discussion? @Esko Dijk<mailto:esko.dijk@iotconsultancy.nl>

BRs,
Kangping



On Wed, Dec 7, 2022 at 7:32 PM Esko Dijk <esko.dijk@iotconsultancy.nl<mailto:esko.dijk@iotconsultancy.nl>> wrote:
I recall that we discussed that a device could temporarily not have a particular service; and some expectation that in due time a service will become available again.
During this time the device wants to keep its name registered, to show that it is still there and functional, and defend its name against potential other devices taking that name.

So one use case is deleting its service(s) but keeping the name registered.

Regards
Esko

From: Ted Lemon <mellon@fugue.com<mailto:mellon@fugue.com>>
Sent: Wednesday, December 7, 2022 12:15
To: Kangping Dong <wgtdkp@google.com<mailto:wgtdkp@google.com>>
Cc: Abtin Keshavarzian <abtink@google.com<mailto:abtink@google.com>>; DNSSD <dnssd@ietf.org<mailto:dnssd@ietf.org>>; Esko Dijk <esko.dijk@iotconsultancy.nl<mailto:esko.dijk@iotconsultancy.nl>>; Jonathan Hui <jonhui@google.com<mailto:jonhui@google.com>>
Subject: Re: SRP: support of SRP message with zero service?

Why is it useful to have a hostname and address generally?  :)

Op wo 7 dec. 2022 om 06:09 schreef Kangping Dong <wgtdkp@google.com<mailto:wgtdkp@google.com>>
Hi,

Regarding SRP registration, it's unclear if at least one "Service Description Instruction" is required in a SRP message when the host is not being deleted.
If it's not required to register at least one service, what's the use case of registering only the host/address? Any examples? (It doesn't seem to be useful
to advertise only the host name and addresses with the Advertising Proxy :)

Thanks!



BRs,
Kangping
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