Re: [net-next RFC PATCH 00/13] net: hsr: Add PRP driver

From: Murali Karicheri
Date: Tue May 26 2020 - 17:33:16 EST

Hi Vladimir

On 5/26/20 2:25 PM, Vladimir Oltean wrote:
Hi Murali,

On Tue, 26 May 2020 at 17:12, Murali Karicheri <m-karicheri2@xxxxxx> wrote:

Hi Vladimir,

I haven't looked the spec for 802.1CB. If they re-use HSR/PRP Tag in the
L2 protocol it make sense to enhance the driver. Else I don't see any
re-use possibility. Do you know the above?



IEEE 802.1CB redundancy tag sits between Source MAC address and
Ethertype or any VLAN tag, is 6 bytes in length, of which:
- first 2 bytes are the 0xf1c1 EtherType
- next 2 bytes are reserved
- last 2 bytes are the sequence number
There is also a pre-standard version of the IEEE 802.1CB redundancy
tag, which is only 4 bytes in length. I assume vendors of pre-standard
equipment will want to have support for this 4-byte tag as well, as
well as a mechanism of converting between HSR/PRP/pre-standard 802.1CB
tag on one set of ports, and 802.1CB on another set of ports.

Thanks for sharing the details. I also took a quick glance at the
802.1CB spec today. It answered also my above question
1) In addition to FRER tag, it also includes HSR tag and PRP trailer
that can be provisioned through management objects.
2) Now I think I get what Vinicius refers to the interoperability. there
can be HSR tag received on ingress port and PRP on the egress port of
a relay function.

Essentially tag usage is configurable on a stream basis. Since both
HSR and PRP functions for frame formatting and decoding would be
re-usable. In addition driver could be enhanced for FRER functions.



Murali Karicheri
Texas Instruments


Murali Karicheri
Texas Instruments