A communication apparatus in a relay node in a communication network includes an interface unit 12 and a core unit 13. Header data contained in framed data based on a communication signal from a signal receiving portion 21 is transmitted from the interface unit 12 to the core unit 13 and, in the core unit 13, a comparison between the header data and history data preserved in a history database are carried out and a flag responding to a result of the comparison is added to the header data, so that the header data having the flag is transmitted to the interface unit 12 from the core unit 13. In the interface unit 12, identification information in the original header data is changed in response to the flag and an output communication signal based on the framed data having the changed identification information is produced to be transmitted.