When an Ethernet frame arrives at a computer, the Ethernet layer must hand the packet that it contains to the next higher layer to be processed. The act of finding the right higher layer to pro-cess received packets is called demultiplexing. We know that in our case the higher layer is IP. But how does the Ethernet protocol know this? After all, the higher-layer could have been another protocol entirely (such as ARP). We have the same issue at the IP layer – IP must be able to deter-mine that the contents of IP message is a TCP packet so that it can hand it to the TCP protocol to process. The answer is that protocols use information in their header known as a "demultiplexing key" to determine the higher layer. O true O false

In the TCP/IP suite, when travelling through a physical network, information comes encapsulated in frames, which format depends on the Data Link Layer Protocol used.

For Ethernet networks, there is a special field, called TYPE, that once read by the software, informs to the Ethernet software to which higher layer must send the packet, once stripped the frame header.

This field TYPE is known as a "demultiplexing key" for the Data Link Layer Protocol.

At the IP level, the IP header contains a similar field, called PROTOCOL in IPv4 and NEXT HEADER in IPv6, which acts in the same way, telling to the IP software which is the higher layer to send the datagram, once stripped the IP Header.