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c) Check frame sequence. The FCS (4 bytes in length) field is used to detect errors in a frame
* addressing * error detection * frame delimiting
Error detection at data link level is achieved by using a Frame Check Sequence (FCS) method like Parity, Checksum Calculation or Cyclic Redundancy Check (CRC).
Each Ethernet frame contains a trailer with a cyclic redundancy check (CRC) of the frame contents. After reception of a frame, the receiving node creates a CRC from the bits in the frame to compare to the CRC value in the frame trailer. If these two CRC calculations match, the frame can be trusted as being received without error. The trusted frame will then be processed. A frame received with bad, nonmatching CRC's will be discarded.
--CORRECTION--from Network+ Guide To Networks, fifth edition. This marks the end of the frame. The "trailer" indicates the frame check sequence number. It is used for error control in a frame.
In an Ethernet frame, FCS stands for "Frame Check Sequence". It is a four-octet field used to verify that the frame was received without loss or error. The method used for verification is known as a Cyclic Redundancy Check (CRC).
to represent the frames sequence numberI believe this is wrong in the 5th edition....Network+ Guide to Networks on page57 it states that protocols in the data link layer add a header to the front of each packet and a trailer to the end of each packet to make frames. (The trailer indicates where a frame ends.)paragraph 4
The purpose of the FCS field is to transmit the extra checksum characters added to a frame in "xyz" protocol for error detection. The most popular algorithm I've used is the CRC (cyclic redundancy check) employed in things like ethernet or PPP on a routed network. Keep in mind that ethernet defines that the errored frame should be discarded, but ethernet takes no action to cause the frame to be retransmitted. Typically most tech's see it as unnecessary overhead and opt to rely on CSMA\CD or CSMA\CA if the route is not deemed to carry time sensitive data. Hope that clears things up a bit.
The feild is inside the picture, the frame is out
CEIA Spa makes metal detection used by Governments, etc. CEIA Spa makes metal detection used by Governments, etc.
A translation error occurs.
It calculates a check-sum from the data in the frame and sends it to the source for verification