As ISPs and telcos converge toward all-IP network infrastructures, the problem of service reliability becomes more acute. In this article, we investigate to what extent DiffServ can provide service protection against optical failures in IP over optical (WDM) networks. For this, we propose two mechanisms: a DiffServ/WDM method and a WDM differentiated protection technique that we call DiffProtect. Results show that the priority traffic is equally well protected by both techniques. However, for medium-priority traffic, there is an improvement in delay and jitter under failure when DiffServ is used. Thus, the proposed DiffServ implementation can be used as an affordable and effective fault management technique to protect high-priority traffic with little delay