The other two challenges that snoop protocols face are direct consequences of performing snoop broadcasts on all cache misses. These snoops consume large amounts of network bandwidth and this is the central factor that limits the scalability of snoop coherence protocols. In addition to network bandwidth, each broadcast consumes significant tag lookup bandwidth as each cache checks to see if it has a copy of the requested block. As the number of cores in the system grows, the rate of snoop-induced tag lookups can cause contention that delays demand lookups from the local core and hurts performance.In addition the challenge of simply providing sufficient network and tag lookup bandwidth, it is important to consider the energy consummed in the network and in the tag arrays as a result of snoop broadcasts.