IS-09 and IS-04

[VentuzVictorPerez]

Hi.

If you only implement the Node API (and not the Registration API), do you have to implement also the IS-09?

Is there any diagram or more information about how and when IS-04 and IS-09 interact?

Thanks in advance.

Regards.

[garethsb]

A Media Node acts as a client of a System API.

IS-04 does not require a Node to implement support for interacting with the System API, but JT-NM TR-1001-1 adds this requirement.

https://specs.amwa.tv/is-09/releases/v1.0.0/docs/4.1._Behaviour_-_Node_Start-Up.html describes the required behaviour, which in order to be useful, needs to happen before the Node starts heartbeating with the Registry.

[VentuzVictorPerez]

Ok.

Yet I still find myself a bit confused, especially when I read here and here.

Media Nodes are required to implement AMWA NMOS IS-04, IS-05 and IS-09 (defined as an appendix in TR-1001-1). These aspects can be tested using the following test suites in this tool.

According to what I have understood Media Nodes do NOT need to implement IS-09 but only INTERACT with IS-09 as a client, am I correct?

System Resources are required to implement AMWA NMOS IS-09. This can be tested using the following test suite in this tool.

What are "System Resources" ? Are they always the same ones that implement the "IS-04 Registry API"?

Thanks.

[prince-chrismc]

1. Media Nodes implement the client side which can be thought of as interacting with the API
2. The definition might a little circular. A System Resource implements IS-09... this can be completely separate from the registry.

[VentuzVictorPerez]

Hello, following with this topic.

Assuming we have two logical hosts A and B, each advertising a Registry API and a System API.

Since the documentation (here and here) specifies that the browsing of both _nmos-register._tcp and _nmos-system._tcp is done after the "Node comes online", how to guarantee that the node does not browse the Registry API of the logical host A with the SystemAPI of the logical host B?

That is to say, in this case it is possible to complete the Registered Operation on the logical host A with the configured parameters of the System API of logical host B.

Is this allowed? Otherwise, how to avoid this according to the specification?

[garethsb]

The DNS-SD mechanism is really there to support redundancy rather than alternatives. Therefore in the case that multiple Registries and System Resources are advertised, they should contain the same information, at least for the case that pri is between 0 and 99, indicating a production environment.

[VentuzVictorPerez]

Ok, perfect, on the other hand, what happens if we find a registry but not the service resources, should we use default values for the registry (like heartbeat interval = 5 seconds)? Or simply not register the resources at all?.

[garethsb]

In my understanding, a device is permitted to support deployment-time configuration for things like whether or not to ever use mDNS or only unicast DNS-SD, whether or not to allow insecure HTTP or only TLS, whether to require a System Resource as per JT-NM TR-1001-1, etc. However it should be up to the user not hardwired into the device. It's worth looking closely at TR-1001-1, but my recollection is that on starting up and not finding a System API, a Node should continue with its current configuration. Initially that would mean the defaults, such as 5s heartbeat interval.

[jmailhot]

thats my understanding as well (and the de#tent of TR-1001-1). if the node starts up and cannot locate the system resource (because maybe its not up yet, or has failed, or...) then the device uses what it last stored. the exact text of tr-1001-1 is: If the System API is unavailable at startup, the Media Node may continue with the startup using stored values from previous operation. Once the System API has been successfully read, Media Nodes should not do any periodic re-checking of it. during the drafting of TR-1001-1 there was a fair bit of discussion around this topic, but we came to the conclusion above, since in normal deployments the contents of the system registry are constants that almost never change, and when they do change its associated with some other disruption (like a major re-organization of the system). So a node is pretty safe to come up and use values it stored from prior operations.

…

On Wed, Jun 16, 2021 at 8:49 AM Gareth Sylvester-Bradley < ***@***.***> wrote: In my understanding, a device is permitted to support deployment-time configuration for things like whether or not to ever use mDNS or only unicast DNS-SD, whether or not to allow insecure HTTP or only TLS, whether to require a System Resource as per JT-NM TR-1001-1, etc. However it should be up to the user not hardwired into the device. It's worth looking closely at TR-1001-1, but my recollection is that on starting up and not finding a System API, a Node should continue with its current configuration. Initially that would mean the defaults, such as 5s heartbeat interval. — You are receiving this because you are subscribed to this thread. Reply to this email directly, view it on GitHub <#18 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/ACPBR3HLOMEKZRCZXYVGH2DTTCMUHANCNFSM46LVZYJQ> .

[peterbrightwell]

@AMWA-TV/nmos-architecture-review shall we close this?