An apparatus (22, 24, 70) comprising: a synchronization monitor operable to monitor a stream of communication traffic, on each communication link of a plurality of communication links (21, 23, 25, 90, 92) from which communication traffic is to be extracted and combined into a single communication traffic stream, for receipt of respective synchronization information (ICPn) for the communication link; and a synchronization recovery module operatively coupled to the synchronization monitor and operable to determine whether an error has occurred in receipt of the synchronization information (ICPn) for any of the communication links (21, 23, 25, 90, 92), and to modify a stream of communication traffic received on a communication link responsive to an error in receipt of the synchronization information (ICPn) for the communication link, the synchronization information (ICPn) having an expected position in a stream of communication traffic on a communication link, the apparatus (22, 24, 70) being characterised in that the synchronization recovery module is further operable to determine that an error has occurred where the synchronization information (ICPn) for a communication link is received at its expected position and is received again at a position lagging its expected position; to determine, based on an amount of communication traffic by which the position lags the expected position, an amount of communication traffic, in the stream of communication traffic received on the communication link, which was previously received on the communication link and is received again on the communication link; and to modify the stream of communication traffic received on the communication link by removing the determined amount of received communication traffic from the stream. a synchronization monitor operable to monitor a stream of communication traffic, on each communication link of a plurality of communication links (21, 23, 25, 90, 92) from which communication traffic is to be extracted and combined into a single communication traffic stream, for receipt of respective synchronization information (ICPn) for the communication link; and a synchronization recovery module operatively coupled to the synchronization monitor and operable to determine whether an error has occurred in receipt of the synchronization information (ICPn) for any of the communication links (21, 23, 25, 90, 92), and to modify a stream of communication traffic received on a communication link responsive to an error in receipt of the synchronization information (ICPn) for the communication link, the synchronization information (ICPn) having an expected position in a stream of communication traffic on a communication link, the apparatus (22, 24, 70) being characterised in that the synchronization recovery module is further operable to determine that an error has occurred where the synchronization information (ICPn) for a communication link is received at its expected position and is received again at a position lagging its expected position; to determine, based on an amount of communication traffic by which the position lags the expected position, an amount of communication traffic, in the stream of communication traffic received on the communication link, which was previously received on the communication link and is received again on the communication link; and to modify the stream of communication traffic received on the communication link by removing the determined amount of received communication traffic from the stream.