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IP or TCP checksum

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When two hosts exchange packets through a few LANs, if there are corruptions in packets, it's going to be likely caught by the ethernet frame CRC and dropped by either router/switch/PC NIC. Wonder if this is a correct assumption.

asked 08 Nov '15, 05:44

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pktUser1001
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One Answer:

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Yes, the assumption is correct, even though the FCS may still match for corrupted packets on very rare occasions.

answered 08 Nov '15, 06:52

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Jasper ♦♦
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Agree. FCS and IP/TCP header checksum use different algorithm. So that's possible. Thanks.

(08 Nov '15, 06:56) pktUser1001

Recently we experienced a faulty network device that was corrupting packets internally but sending valid Ethernet frames containing that corrupted data, so I don't think this is necessarily a correct assumption. Statistically speaking, it's probably safe to say that in most cases the FCS will catch the bad frames, but in cases like this, it won't.

(08 Nov '15, 07:45) cmaynard ♦♦