tcpdump mailing list archives
Re: Link-Layer Header Type request: USB 2.0
From: Tomasz Moń <desowin () gmail com>
Date: Mon, 22 Jul 2019 06:22:52 +0200
On Sun, Jul 21, 2019 at 10:47 PM Guy Harris <gharris () sonic net> wrote:
It looks as if USB 3.1's packets are different from USB 2.0's packets, so this would be 2.0-specific.
USB 3 operates on different hardware signals. USB 3 hubs do contain USB 3 and USB 2.0 hubs inside them. The USB 2.0 data is sent on the D+/D- differential pair, while the USB 3 data uses dedicated Superspeed differential pairs for RX and TX. Valid USB 1.0 and 1.1 packets can be dissected as USB 2.0. However, this is not always true the other way round. For example USB 1.1 device won't understand SPLIT packet. Fortunately compliant USB 2.0 Host won't ever send SPLIT to the USB 1.1 device as this PID can only be sent on High Speed link (which was introduced in USB 2.0). USB 1.0 and 1.1, did feature Low- and Full- speed transmission speeds. USB 2.0 features Low-, Full- and High- speed transmission speeds. As the proposed Link-Layer Header Type operates on packet level, it has no information about the speed the packet was transmitted at.
The new Link-Layer Header Type is supposed to contain the USB 2.0 packets. That is, anything that appears on the bus between the Start- and End-of-Packet delimiters. The packet format is described in Chapter 8 Protocol Layer of Universal Serial Bus Specification Revision 2.0.So that's the PID as the first byte and continuing from there?
Yes. PID is 4 bits long. The first byte contains PID and completed PID. _______________________________________________ tcpdump-workers mailing list tcpdump-workers () lists tcpdump org https://lists.sandelman.ca/mailman/listinfo/tcpdump-workers
Current thread:
- Link-Layer Header Type request: USB 2.0 Tomasz Moń (Jul 21)
- Re: Link-Layer Header Type request: USB 2.0 Guy Harris (Jul 21)
- Re: Link-Layer Header Type request: USB 2.0 Tomasz Moń (Jul 21)
- Re: Link-Layer Header Type request: USB 2.0 Guy Harris (Jul 22)
- Re: Link-Layer Header Type request: USB 2.0 Tomasz Moń (Jul 22)
- Re: Link-Layer Header Type request: USB 2.0 Guy Harris (Jul 22)
- Re: Link-Layer Header Type request: USB 2.0 Tomasz Moń (Jul 22)
- Re: Link-Layer Header Type request: USB 2.0 Guy Harris (Jul 23)
- Re: Link-Layer Header Type request: USB 2.0 Tomasz Moń (Jul 21)
- Re: Link-Layer Header Type request: USB 2.0 Guy Harris (Jul 21)