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@xxxxxxxxxxxxxxxxx, 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.
