According to a study of three different evolution paths for mobile peer-to-peer (MP2P) communications in [7], it is a strong candidate for Internet VoIP support in worldwide interoperability for microwave access (WiMAX) or long term evolution (LTE) networks. Kademlia and dSIP are suitable for P2PSIP implementation on wireless networks. In this context, they yield good routing performance and scalability, allow self-organization and achieve secured, trustworthy P2P overlays. In [8,9], it is demonstrated that a Kademlia-based implementation can support general Internet services and distributed multimedia services on wireless networks. Kademlia’s exclusive-OR (XOR) topology-based routing schema requires less maintenance than other structured P2P overlays [10], such as Pastry [11] or Tapestry [12].

It also performs better than Chord [13] in terms of lookup routing, overlay routing scalability and overlay self-organization.From a practical perspective, we chose Kademlia for our study, because there is a real implementation of dSIP + Kademlia available (from the University of Parma [14]); the dSIP implementation is fully compatible with current commercial SIP solutions, and it is relatively simple to modify without compromising compatibility.Some goals of P2PSIP systems are:Automatic setup: neighbor discovery or initial registration should be automatic procedures.Efficient lookup: the system should scale well with an increasing number of peers and growing demands.Support for heterogeneous peers: the participants in the overlay should be able to own different resources and have different network and available capacities; the system must also be platform-independent.

Interoperability: A P2PSIP and another SIP-compliant node (even with traditional SIP implementations) should understand each other.In order to keep the DHT registers of the P2PSIP network up-to-date, they are refreshed periodically. This paper discusses previous algorithms for managing time-to-refresh (TTR) timers and proposes an adaptive algorithm to optimize these timers to ensure the consistency of distributed routing tables and resource registers in P2P wireless overlay networks. This goal is important, since it will improve the trade-off between management cost and updating accuracy. With static TTR algorithms, management load grows with updating accuracy.

The proposal, called adaptive TTR (ATTR), outperforms previous approaches in terms of management signaling overhead, by taking into account latencies between wireless network peers and by setting up a separate TTR timer for each Brefeldin_A P2PSIP resource to be refreshed, rather than a common timer per peer. Our work focuses on structured overlay networks [15], such as Kademlia [16] (employed by the eDonkey P2P system [17,18]) and Chord [13]. As previously mentioned, a joint Kademlia-based DHT/dSIP implementation of P2PSIP was considered.