Satisfying critical QoS requirements in next generation networks poses major challenges, due to its intrinsic complexity of network resource allocation. This paper considers the problem of load balance based bandwidth allocation for delay sensitive services. For satisfying deterministic end-to-end delay requirement, a simple and efficient algorithm for path level optimal bandwidth allocation, Path level Equal Ratio Allocation algorithm (P-ERA), is developed first. Based on P-ERA, another algorithm for network level optimized bandwidth allocation, Network level Equal Ratio Allocation algorithm (N-ERA), is also presented for much more complicated network circumstances. N-ERA algorithm features appropriate route selection and balanced bandwidth allocation, and can adaptively avoid, or at least delay, the emergence of network bottleneck when a network is heavily loaded. Extensive simulations indicate that N-ERA algorithm can make full use of network bandwidth and admit more services, even if they are delay critical, than other ones dealing with the same problem. And the less computation complexity of N-ERA algorithm makes it of great application value.