Many envisioned applications of ad hoc networks involve only small-scale networks that we term Vicinity Ad-hoc Groups (VAGs). Distributed coordination services, instead of pairwise communications, are the primary requirements of VAGs. Existing designs for distributed services apply either a layered structure or a vertical integration. While the former contributes to design simplicity, the latter improves runtime efficiency. In this paper, we argue that, since distributed services require group-oriented communications, our NASCENT approach can achieve both design simplicity and runtime efficiency in VAGs. NASCENT is a network layer service dedicated for VAGs. It provides a light-weight membership service along with a routing structure for message passing, and it supports the concurrent execution of various distributed algorithms. NASCENT is also tailored to cope with the transiency of VAGs. We demonstrate how smoothly distributed algorithms can be built on top of NASCENT. With a complexity-based analysis, we also show that NASCENT greatly improves the runtime efficiency of these distributed algorithms. Finally, through simulations with ns-2, we confirm the ability of NASCENT to support the envisioned VAG applications.