21.1 Introduction to Social Networks21.1.1 Milgram’s Experiment21.2 Metrics of Social Networks21.2.1 Clustering Coefficient21.2.2 Diameter21.3 Modeling Social Networks21.3.1 Erdös–Rényi Model21.3.2 Small-World Model21.3.3 Power-Law Graphs21.4 Centrality Measures in Social Networks21.4.1 Degree Centrality21.4.2 Closeness Centrality21.4.3 Betweenness Centrality21.5 Community Detection21.5.1 Girvan–Newman Algorithm21.6 Introduction to Peer-to-Peer Networks21.7 First-Generation P2P Systems21.7.1 Napster21.7.2 Gnutella21.8 Second-Generation P2P Systems21.8.1 KaZaA21.8.2 Chord21.8.3 Content-Addressable Network21.8.4 Pastry21.9 Koorde and De Bruijn Graph21.10 Skip Graph21.11 Replication Management21.12 BitTorrent and Free Riding21.13 Censorship Resistance, Anonymity21.14 Concluding Remarks21.15 Bibliographic NotesExercises