Most academics depend upon email to do their jobs.
However, email is not trustworthy. Specifically, it is almost never possible to verify, using the email alone, that a received message has come from the apparent sender. As a side-benefit, students get an introduction to the principles of operation of network protocol, and an example of the use of a state machine as a program design technique. This paper studies space bounded algorithms, i.e., algorithms that use a constant amount of scratch space, for the k-server problem. The paper first shows a characterization of the set of space bounded algorithms that are competitive in finite metric spaces.