hese operations occur within the overlay, rather than on the conventional server. 9.5.2.4 Other Features of dSIP dSIP does not specify which of the three mechanisms will be used for routing: Iterative, recursive, or semi-recursive. In general, the messages can be routed using any of these mechanisms. Various mechanisms may be used within the same overlay and even within the same search. dSIP provides mechanisms that are used for a number of operations, including peer registration, resource registration, session establishment, and DHT maintenance. 9.5.3 The RELOAD Protocol RELOAD is an extensible and lightweight distributed REsource LOcation And Discovery protocol. RELOAD is one possible implementation of the P2P SIP protocols. RELOAD uses binary messages, derived as much as possi- ble from the STUN protocol [21], as the underlying protocol. In this archi- tecture, no P2P SIP client protocol is needed, unmodified SIP is used for access by non-peers. The protocol considers NAT traversal and fragmen- tation, supports storage of information other than registrations, allows for C 2009 by Taylor & Francis Group, LLC P2P SIP: Network Architecture and Resource Location Strategy multiple DHT and hash algorithms, and provides hooks for multiple security schemes. As described earlier, dSIP transported all messages, including those used to maintain the DHT, using SIP. However, concerns were raised about the "misuse" of SIP messages and the heaviness of the SIP as the P2P peer proto- col. For these concerns, the RELOAD draft presents a binary protocol for the P2P SIP peer protocol. The protocol provides the framework for exchanging P2P messages, and is designed to be extended by pluggable DHT algorithms and security solutions. The benefit of moving away from SIP as the encoding for the P2P SIP peer protocol is the ability to design a new protocol wholly focused on the requirements of P2P SIP. The major advantages of the protocol include the following aspects. A fixed-length header is defined that can be used for routing the m