CRC vs FCS on dot1q

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Nov 15th, 2006
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In the text below, if I say *CRC* instead of *FCS*, is the statement below still correct?


"IEEE 802.1Q uses an internal tagging mechanism which inserts a 4-byte tag field in the original Ethernet frame itself between the Source Address and Type/Length fields. Because the frame is altered, the trunking device recomputes the *FCS* on the modified frame."

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Richard Burts Wed, 11/15/2006 - 10:03
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Marlon


Cyclic Redundancy Check (CRC) and Frame Check Sequence (FCS) are roughly equivalent terms. Depending on the context in which you are examining them (and the degree of precision required in the definition) the statement is probably true with either term inserted.


HTH


Rick

mohammedmahmoud Thu, 01/25/2007 - 06:04
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Hi Marlon,


I think its tooooo late replying on this post, but i've got this result so i liked to share it with you:


"The 4-bit cyclic redundancy check (CRC4) is an error-checking technique that uses a calculated numeric

value to detect errors in transmitted data. By default, CRC4 is not enabled. The sender of a data frame

calculates the frame check sequence (FCS). Before it sends a frame, the sender appends the FCS value

to the message. The receiver recalculates the FCS and compares its calculation to the FCS from the

sender. If there is a difference between the two calculations, the receiver assumes that a transmission

error occurred and sends a request to the sender to resend the frame.

"


http://www.cisco.com/en/US/products/hw/modules/ps2033/products_module_installation_guide_chapter09186a00800c4bcd.html#1025058


Briefly what i understood, CRC is the error-checking technique while FCS is the calculated value used by this technique.


best regards,

Mohammed Mahmoud.

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