Fragmentation and interleaving is implemented on the originating end of the traffic. In other words, in the upstream direction the CPE (or RG) is fragmenting and interleaving traffic. There is no interleaving or fragmentation processing in the upstream direction in the 7750 SR. The 7750 SR are on the receiving end and is only concerned with the reassembly of the fragments arriving from the CPE. Fragments are buffered until the packet can be reconstructed. If all fragments of a packet are not received within a preconfigured time frame, the received fragments of the partial packet are discarded (a packet cannot be reconstructed without all of its fragments). This time-out and discard is necessary to prevent buffer starvation in the BB-ISA. Two values for the time-out can be configured: 100ms and 1s.