Discuss the potential advantages and drawbacks of the use of an X$\mathrm{.}500$ directory service in place of the DNS and the Internet mail delivery programs.

Describe the advantages of the uniformity of Uniform Resource Identifiers $($URIs$)$ and Uniform Resource Locators $($URLs$).$

Discuss the problem associated with name services in a distributed system. How can this be solved?

Explain why a name space is important for a particular name service. What is the advantage of a hierarchic name space

A scheme for implementing at$-$most$-$once reliable message delivery uses synchronized clocks to reject duplicate messages. Processes place their local clock value $($a timestamp$)$ in the messages they send. Each receiver keeps a table giving, for each sending process, the largest message timestamp it has seen. Assume that clocks are synchronized to within $100$ ms$,$ and that messages can arrive at most $50$ ms after transmission.

When may a process ignore a message bearing a timestamp T$,$ if it has recorded the last message received from that process as having timestamp $?$

When may a receiver remove a timestamp $175,000($ms$)$ from its table? $($Hint: use the receivers local clock value.$)$

Should the clocks be internally synchronized or externally synchronized?