METHOD AND APPARATUS FOR PLACING A TIMESTAMP IN A FRAME

摘要

Timestamp information can le placed in a frame (fig. 3) that includes a first portion processable at a selected layer of a protocol stack and a second portion processable at a lower protocol layer of the protocol stack subsequently to the processing of the first portion wherein the first portion is contained within the second portion and wherein a numerically computed error detection code for the second portion is computed during processing of the second portion. A timestamp signature having a timestamp subfield of initialized data and a corrector subfield of initialized data is embedded (34) in the first portion during processing thereof at the selected protocol layer. A numerical constant functionally equivalent to the numerically computed error detection code is determinable from the initialized data in the timestamp subfield and the corrector subfield (46). The data in said timestamp subfield is modified (36) with timestamp information subsequently to processing of the second portion at the lower protocol layer. The data in the corrector subfield is then modified (38) such that the numerical constant as determinable from the modified data in the timestamp subfield and the corrector subfield remains unchanged, whereby the numerically computed error detection code computed at the lower protocol layer remains valid.