  Cache-equipped Base-Stations (CBSs) is an attractive alternative to offload
the rapidly growing backhaul traffic in a mobile network. New 5G technology and
dense femtocell enable one user to connect to multiple base-stations
simultaneously. Practical implementation requires the caches in BSs to be
regarded as a cache server, but few of the existing works considered how to
offload traffic, or how to schedule HTTP requests to CBSs. In this work, we
propose a DNS-based HTTP traffic allocation framework. It schedules user
traffic among multiple CBSs by DNS resolution, with the consideration of
load-balancing, traffic allocation consistency and scheduling granularity of
DNS. To address these issues, we formulate the user-traffic allocation problem
in DNS-based mobile edge caching, aiming at maximizing QoS gain and allocation
consistency while maintaining load balance. Then we present a simple greedy
algorithm which gives a more consistent solution when user-traffic changes
dynamically. Theoretical analysis proves that it is within 3/4 of the optimal
solution. Extensive evaluations in numerical and trace-driven situations show
that the greedy algorithm can avoid about 50% unnecessary shift in user-traffic
allocation, yield more stable cache hit ratio and balance the load between CBSs
without losing much of the QoS gain.
