SPMLD: Sub-Packet Based Multipath Load Distribution for Real-Time Multimedia Traffic

Load distribution is vital to the performance of multipath transport. The task becomes more challenging in real-time multimedia applications (RTMA), which impose stringent delay requirements. Two key issues to be addressed are: 1) how to minimize end-to-end delay, and 2) how to alleviate packet reordering that incurs additional recovery time at the receiver. In this paper, we propose SPMLD, a new model that splits traffic at the granularity of sub-packet. The Sub-Packet based Multipath Load Distribution (SPMLD) model aims to minimize total packet delay by effectively aggregating multiple parallel paths as a single virtual path. First, we formulate the packet splitting over multiple paths as a constrained optimization problem and derive its solution based on progressive approximation method. Second, in the solution, we analyze queuing delay by introducing D/M/1 model and obtain the expression of dynamic packet splitting ratio for each path. The performances of SPMLD are evaluated through extensive simulations in QualNet using real-time H.264 video streaming. Experimental results demonstrate that: SPMLD outperforms previous flow and packet based load distribution models in total packet delay, end-to-end delay and seldom induces packet reordering. Besides, SPMLD's extra overhead is tiny compared to the input video streaming.