Technological advances have increased the transistor density, thereby ushering in multi- and more recently many-core systems, distinguished by the presence of hundreds of cores on a single chip. For such a platform, the Network-on-Chip (NoC) has emerged as a scalable and efficient interconnect fabric to realize the communication across an ever increasing number of processor cores, memories, and specialized IP blocks both on- and off-chip. In this paper, we highlighted some key problems in NoC based architectures that must be addressed before the deployment of real-time applications onto these platforms becomes possible. A paradigm shift from function centric to data and communication centric approaches is required. Combining hardware and software based flow-regulation seems to be the only way to ensure that NoCs go beyond the best-effort service and address the requirements of diverse applications.