An apparatus, comprising: a receiver unit capable of receiving frames at a redundant port connecting a node to a communications network; a memory comprising groups of data structures, wherein a data structure comprises reception information for a portion of consecutive frames in a sequence of frames transmitted by a specific transmitter node, the reception information indicating whether a frame belonging to the portion of consecutive frames has been received or not; a processing unit operatively connected to the receiver unit and the memory to cause together with the receiver unit and the memory: deriving, from a frame received by the receiver unit, a communications layer address of the transmitter node of the frame and information capable of identifying a portion of consecutive frames in a sequence of frames the received frame belongs to; generating, on the basis of the derived communications layer address and the information capable of identifying a portion of consecutive frames in a sequence of frames, at least one address for accessing a group of data structures in the groups of data structures; determining, on the basis of the derived communications layer address, an available data structure for storing reception information for frames from the transmitter node in the group of data structures accessible by the generated address for accessing a group of data structures in the groups of data structures; deriving, from the received frame, information capable of identifying the received frame within the portion of consecutive frames in a sequence of frames; reading, on the basis of the derived information capable of identifying the received frame within the portion of consecutive frames in a sequence of frames, the reception information for the received frame in the data structure; and determining whether the received frame is a duplicate frame on the basis of the read reception information. a receiver unit capable of receiving frames at a redundant port connecting a node to a communications network; a memory comprising groups of data structures, wherein a data structure comprises reception information for a portion of consecutive frames in a sequence of frames transmitted by a specific transmitter node, the reception information indicating whether a frame belonging to the portion of consecutive frames has been received or not; a processing unit operatively connected to the receiver unit and the memory to cause together with the receiver unit and the memory: deriving, from a frame received by the receiver unit, a communications layer address of the transmitter node of the frame and information capable of identifying a portion of consecutive frames in a sequence of frames the received frame belongs to; generating, on the basis of the derived communications layer address and the information capable of identifying a portion of consecutive frames in a sequence of frames, at least one address for accessing a group of data structures in the groups of data structures; determining, on the basis of the derived communications layer address, an available data structure for storing reception information for frames from the transmitter node in the group of data structures accessible by the generated address for accessing a group of data structures in the groups of data structures; deriving, from the received frame, information capable of identifying the received frame within the portion of consecutive frames in a sequence of frames; reading, on the basis of the derived information capable of identifying the received frame within the portion of consecutive frames in a sequence of frames, the reception information for the received frame in the data structure; and determining whether the received frame is a duplicate frame on the basis of the read reception information. deriving, from a frame received by the receiver unit, a communications layer address of the transmitter node of the frame and information capable of identifying a portion of consecutive frames in a sequence of frames the received frame belongs to; generating, on the basis of the derived communications layer address and the information capable of identifying a portion of consecutive frames in a sequence of frames, at least one address for accessing a group of data structures in the groups of data structures; determining, on the basis of the derived communications layer address, an available data structure for storing reception information for frames from the transmitter node in the group of data structures accessible by the generated address for accessing a group of data structures in the groups of data structures; deriving, from the received frame, information capable of identifying the received frame within the portion of consecutive frames in a sequence of frames; reading, on the basis of the derived information capable of identifying the received frame within the portion of consecutive frames in a sequence of frames, the reception information for the received frame in the data structure; and determining whether the received frame is a duplicate frame on the basis of the read reception information.