PLC (PowerLine Communication) is becoming an interesting last mile solution for both in-home and access applications, this mainly due to its ubiquity and continually growing bit rate. However what is its capability to provide QoS guarantees for real-time applications is still an open problem. In this paper, we first analyse the real-time QoS supporting of the two main PLC MAC protocols, then address the performance problem of TCP Westwood over PLC by simulation. This simulation study revealed the impact of the packet loss rate on TCP performance. We also discuss the importance of coordinating TCP's RTT estimation with the ARQ of the underlying PLC MAC protocol.