Markers, one of the building blocks of a traffic conditioner play a major role for resource allocation in a DiffServ network. Recently, there has been a considerable research interest in designing intelligent markers, tailored for TCP traffic. The TCP dynamics make the design of a marker difficult in many respects. We list out the issues related to designing a TCPfriendly marker and propose an intelligent marker, namely, Memory-Based Marker (MBM) to address those issues. We illustrate the benefits of the proposed marker over some existing markers in a DiffServ network. The marker was implemented in NS simulator and extensive simulations were done to study the behaviour of MBM. Our results show significant improvement in TCP performance, especially in achieving fairness among priority flows with distinct round trip times, windows, and target rates. The marker is capable of protecting TCP flows in cases of congestion caused by the unruly UDP flows. We also investigate the impact of coexisting assured service UDP flows on the assurance to the TCP flows. The major benefits of MBM are its simplicity, least sensitivity to parameters and transparency to the end hosts.