P2P Network Architectures - Peer-to-Peer Computing: Applications, Architecture, Protocols, and Challenges - page 52

mance, such as CAN and Chord, requires strict compliance to the protocols
on the peer's part; otherwise, the structured query and response mechanisms
would not work. At the other end, totally unstructured network architectures,
such as those manifested by a Gnutella or BitTorrent network, provide high
robustness and resilience to peer dynamics, at the expense of having an un-
predictable performance. Many efforts are thus proposed to combine the best
of both worlds, in the form of some hybrid designs, such as UBCA and Bris-
tle. In media applications such as video and voice, QoS guarantees are very
important and highly desirable features, motivating many network architec-
ture designs with QoS provisions. Unfortunately, we have yet to see real life
implementations of these research ideas. One plausible reason for the lack of
practical implementation of QoS guaranteed architecture is that there are still
many unresolved issues. Among them, incentives and security are two of the
more crucial ones.
3.9 Review Questions
1. Explain why a Chord DHT system has O(log N ) routing steps.
2. Compare and contrast the CAN and Chord DHT systems.
3. Why is an unstructured network architecture more robust?
4. What are the essential features of a typical hybrid network architecture
design?
5. How does a carrier-grade P2P network architecture provide QoS guar-
antees?
6. Describe the trade-off between a SIMS/MIMS architecture and a FAMS
architecture.