COMP247 Lecture Notes - Lecture 2: Network Layer, Ethernet Frame, Channel Access Method
19 Sep 2018
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Document Summary
Pan: personal area network, like bluetooth devices connected to your personal device. Fundamental problem in computer science is resource allocation (most systems revolve around resource allocation), since networks are shared. We want to arbitrate resource allocation, we want it to be safe, avoid deadlocks, resource requests are always successful (liveness), no processes are excluded (starvation) and ordered. Point-to-point access: exclusive, can transmit at anytime, no need for access control, no addresses, problem of triangle connectivity, physically secure. Multipoint network: share access, only transmit when clear, must control access, need address to identify who receives message, physically open (insecure, protocols, controlled-access protocol, reservation: reserve the medium for exclusive access for a time period. Controlled by a central authority e. g. aircraft on runways, telephone calls, satellite channel, theatre seat booking, tables at restaurants: polling: coordinator asks each participant if they need a resource, token passing: no coordinator.
