Every Ethernet package has a 32-bit checksum. This checksum is effective and discovers most transfer errors. The transport protocol tends to also use a checksum. For example, in TCP and UDP, there is an easier 16-bit checksum.

Why does the transport protocol add an extra checksum and why does it not just rely ln the checksum in the Ethernet package?

What type of error can you think of that a checksum in the transport protocol can detect but not of the Ethernet protocol?

Which of the alternatives below are correct (only two are).

A) Ethernet checksum only controls that the Ethernet frame is error free but not the TCP header and the load. If bit errors happens in the TCP header it will not be detected by the checksum in the Ethernet frame.

B) The checksum in Ehyernet controls the whole Ethernet frame and the content. The checksum in TCP controls the TCP header and the content in TCP.

During a transmission of Ethernet package on the network, the Ethernet frame can be rejected by a router and added in again by the same router for continued transfer in the network.

C) The TCP protocol is an old protocol that already had the checksum integrated when the Ethernet protocol came and there remained.

D) The Ethernet frame can be changed to another data link protocol during transmission between different networks.