network topology

http://uva.ulb.ac.be/cit_courseware/networks/pt2_1.htm

http://compnetworking.about.com/od/networkdesign/a/topologies.htm

http://en.wikipedia.org/wiki/Network_topology

http://www.networktutorials.info/topology.html

http://compnetworking.about.com/od/networkingdesign/a/topologies.htm