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36. Firewalls, Packet Filtering -- Network packet footer?

cfuchs
cfuchs Posts: 15
edited February 23 in LFS201 Class Forum

One of the first sections of chapter 36 "Firewalls", namely "Packet Filtering", mentions that each packet sent over the network also has a footer.

I wonder if there are any cases where the footer is relevant.

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What I could check for myself so far:

  • ethernet frames merely finish with a checksum?
  • IP, UDP, TCP have no footer; they are specified by header+payload

I think data with a bad checksum will be rejected anyway and is not relevant for firewalls. Also, a footer may only be beneficial on low-level layers, when logic can be hardwired on silicon, and higher levels may try to avoid it (and just split the bytes between metadata-header and payload-body)

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Is there any footer data, or any protocol footer, that should be considered here? Or can I safely focus on header and payload, and ignore any footers?

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