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Likewise, each layer on the receiving system unwraps the received message, often called a protocol data unit (PDU), with each layer examining, using, and stripping off the information it needs to complete its task, and passing the remainder up to the next layer (except for the application layer, which passes what’s left off to the application program itself). For example, the data link layer removes the wrapper meant for it, uses it to decide what it should do with this data unit, and then passes the remainder up to the network layer.


Cover of The Illustrated Network


received PDU unwraps the info and forwaord the remainder to upper layer