[Detnet] Some Comments about the information model

["Gengxuesong (Geng Xuesong)" <[e-mail]>]

Hi Bala'zs


I have read "draft-farkas-detnet-flow-information-model-00". Thank you for offering the whole picture of DetNet information model, combining L2 and L3.

Here are some comments and questions after reading the draft:

6.1. Identification and Specification of Flows
"Identification options for TSN flows are specified by [IEEE8021CB], which also includes IP flow identification"

So I find the relative contents in [IEEE8021CB] as follows:
" The IP Stream identification is a passive Stream identification function that operates at the transport layer and Internet Protocol interface layer."

That is to say, the information of this part can only be recognized by the end station or other "DetNet edge node", which contain the transport layer(It is different from the transport layer in draft-finn-detnet-architecture-08. It is the transport layer in IP/TCP I think). However, the intermediate node which will forward the DetNet flow should also have the ability to separate DetNet flows from other flows, and send them to a special queue or make them go through queuing scheduler, in order to limit the delay in this node. So whether you have considered DetNet identification in every intermediate node as described above?


10. Status
"AccumulatedLatency is specified as an integer number of nanoseconds. Latency is measured using the time at which the data frame's message timestamp point passes the reference plane marking the boundary between the network media and PHY. The message timestamp point is specified by IEEE Std 802.1AS [IEEE8021AS] for various media. For a successful Status, the network returns a value less than or equal to the MaxLatency of the UserToNetworkRequirements (Section 9.3)."

If AccumulatedLatency of a particular path is MEASURED, even when it is less than the MaxLatency, it can not been proved that all the flows going through the path will experience latency which is less than their requirements. Because MEASUREMENT is only a special case. Maybe AccumulatedLatency should be defined as a value independent of the Internet conditions, such as a calculated value by the theory or other methods?





Best Regards,

Xuesong