[159001] in North American Network Operators' Group
Validation of FCS
daemon@ATHENA.MIT.EDU (Jason Lixfeld)
Wed Dec 19 09:54:04 2012
From: Jason Lixfeld <jason@lixfeld.ca>
Date: Wed, 19 Dec 2012 09:53:26 -0500
To: "nanog@nanog.org" <nanog@nanog.org>
Errors-To: nanog-bounces+nanog.discuss=bloom-picayune.mit.edu@nanog.org
Hi all,=20
I'm trying to confirm (or debunk) my current understanding of FCS =
errors. An FCS error is a layer 2 error. In Ethernet spake, the 4 =
bytes of FCS data within each Ethernet frame is validated by a CRC =
check, which is done by the device receiving said frame. If the CRC =
check fails, an FCS error is reported by that receiving device.
If that understanding is true and presuming a "circuit" was made up of =
many layer 2 devices between the A and Z side of said circuit, it would =
be impossible for a CRC error somewhere along the path of that circuit =
to register on the receiving device of either the A or Z side. Perhaps =
in simpler terms, a CRC error is a localized thing and would never be =
forwarded from one device to another.
Is that fair and/or accurate?
Thanks in advance.=
