Hello,

Multi-path routing could be a solution for this problem.

Queue priority with selective dropping could be used too. If you want to work in the routing layer, you could consider the usage of routing metrics for this issue. I have a paper about it: "Using fuzzy link cost and dynamic choice of link quality metrics to achieve QoS and QoE in wireless mesh networks. Journal of Network and Computer Applications"

http://www.sciencedirect.com/science/article/pii/S1084804510000615 

These articles will help you:

http://arxiv.org/ftp/arxiv/papers/1012/1012.0887.pdf

http://www.issres.net/journal/index.php/csl/article/viewFile/57/13

http://ieeexplore.ieee.org/xpl/login.jsp?tp=&arnumber=4289081&url=http%3A%2F%2Fieeexplore.ieee.org%2Fxpls%2Fabs_all.jsp%3Farnumber%3D4289081

You can study differentiated services and integrated services for this along with various queueing techniques.