Wireshark · Wireshark-dev: Re: [Wireshark-dev] Link type proposal, IEEE 802.1Qbu Frame Preemption Protocol

[Anton Glukhov <anton.a.glukhov@xxxxxxxxx>]

1. You are right, I'm not subscribed there. I will fix this problem)

2. I'd like to have completely separate LinkType number and this is not LINKTYPE_ETHERNET, because preamble must be shown with specific SMD bytes, and CRC or mCRC must be also shown.

This linktype will show both regular and preemption traffic, with preamble and CRC for both of these types. So, my point of view, is to assign the new linktype which not related to LINKTYPE_ETHERNET or regular Ethernet traffic.

Thank you!

2017-11-30 11:10 GMT+01:00 Guy Harris <guy@xxxxxxxxxxxx>:

On Nov 30, 2017, at 1:42 AM, Anton Glukhov <anton.a.glukhov@xxxxxxxxx> wrote:

> I've been working for IEEE802.1Qbu Frame Preemption Protocol and now it's part of TSN set of protocols. I would like to propose the new link type and sent this proposal to tcpdump-workers@lists.tcpdump.org, but unfortunately no response.

It's hard to respond to a message that was never delivered. :-)

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> I'm working for Frame Preemption Protocol(IEEE 802.1Qbu), which is part of Time-Sensitive Networking(TSN) set of standards. The protocol has very interesting extension of standard Ethernet frame and I'd like to propose to add the new link-layer type. Here are the reasons:
> - protocol uses non-standard ethernet preamble, user must see the type of frame/fragment

LINKTYPE_ETHERNET frames don't include the preamble, so a preempting frame with a different preamble would look, in an LINKTYPE_ETHERNET capture, exactly like a non-preempting frame.

Are you saying that you want a variant of LINKTYPE_ETHERNET, in which the MAC header is preceded by something that indicates whether this is a regular or a preempting frame, so that captures with this link-layer header type can include both regular and preempting frames?

> - protocol uses specific CRC sum. It's called mCRC and depends on preamble, which means the type of frame/fragment

LINKTYPE_ETHERNET may, but aren't guaranteed to, include the CRC; to properly check the CRC, the additional metadata giving the frame type would be required, so it knows whether it's a regular or modified CRC.
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