Questions from previous exams

Pagina 1

Questions from previous exams JANUARY 2018 Q1. Consider the network below. Assume that initially the routing algorithm had already achieved convergence and all links have equal cost 2. Explain why and how the count -to-infinity phenomenon occurs (when split horizon is not adopted), after link CD fails. Report t he sequence of DVs exchanged by the nodes A, B and C regarding destination D during the count to infinity. (see Q1 - January 2019) Q2. Graphically illustrate the components involved in an e-mail system based on the protocols SMTP and POP3. Briefly expla in the role of each component and show all application -layer messages exchanged when [email protected] sends an e-mail to [email protected], specifying for each message: type, source, destination and layer-4 protocol used to transfer it. (see Q2 - February 2019, IMAP) Q3. Briefly explain what a VLAN is and how multiple VLANs can be configured in an Ethernet switch, considering that the switch has several access ports and a trunk port. (see Q2 – June 2019) Q4. What is a POP (Point-Of-Presence) in the Internet infrastructure? FEBRUARY 2018 Q1. With an example of a symbolic name resolution, show the difference between recursive- and iterative-mode DNS query. Draw the two situations to display graphically the comparison. Name all the components that appear in the picture using the appropriate DNS-database terminology. Q2. Consider a client that has to retrieve three different -size objects from an HTTP server. By using time diagrams, graphically compare the following four situations: H TTP/1.0 - non persistent, HTTP/1.1 - persistent without pipelining, HTTP/1.1 - persistent with pipelining, HTTP/2 - use of streams and frames (“chunks”). Explain the consequent practical advantage of HTTP/2 versus HTTP/1.1 .…