In powerline communications (PLC) more so than in many other media, there is a strong interaction between the medium access control (MAC) layer and the physical (PHY) layer. This paper investigates one of the manifestations of this interaction, that of MAC framing and error recovery with PHY transmission characteristics. MAC framing for high-speed PLC systems should be capable of concatenating multiple MAC service data units (MSDUs, e.g., Ethernet or IP packets) in order to amortize the high and fixed overheads associated with each MAC protocol data unit (MPDU). By itself, this is easy. However, transmission errors may damage portions of an MPDU, which can further rob a system of efficiency. This paper presents a 2-level MAC framing mechanism that enables efficient retransmission of corrupted data. Both analytical and simulation results are used to compare the performance of the proposed MAC framing scheme with other existing viable approaches. The results show that the proposed scheme is significantly superior to existing approaches. A slightly modified version of this 2-level framing mechanism provided in this paper was used in the new generation 200 Mbps class homeplug standard, homeplug A V.