S-38.188 exam, 12.5.2004

General comments about the grading (Lx:Sy = lecture nr. x, slide nr. y)

• a) L12:S2 b) L11:S5, c) L3:S23, d) L4:S34-35, e) L13:S13, f) L7:S31
• correct acronym gives 0.5p and a short explanation 0.5p
• some minor errors were tolerated in the acronyms (for example, one of the words could be false without penalty), as long as the explanation was correct

• definition of intra-domain, 1p
• most common algorithms: distance vector (RIP) and link state (OSPF), 1p
• more details of RIP (routing tables exchanged btw. neighbors, possibility of loops, cost=nof hops)(2p) and OSPF (flooding=>topology=>Dijkstra, more state info than in RIP, no loops, arbitrary link costs)(2p)

• MAC addresses: 48 bits, unique, non-hierarchical, hard-coded = 0.5p
• IP addresses: 32 bit or 128 in IPv6, usually unique = 0.5p; hierarchical (important!)= 0.5p
• transport layer: IP address + 16 bit port number = 0.5p
• SMTP: user@domain + explanation = 0.5p
• HTTP: URL ("domain name + directory path" ) = 0.5p

I subtracted 1p if the student believes DNS is used for mapping URI:s or URL:s to IP addresses. If the student does not even know for which purpose DNS is used, I have failed severely as a teacher. Another point is that the first part of the domain name is _not_ the name of service, but the hostname. Beware of the propaganda being fed to the common public!

Some students tried to hide their ignorance on who does what by using passive voice. As an examiner, I find it difficult to give points for this kind of answers. Otherwise, I feel I was generous in giving points.

The question has four subparts,

• 1) Domain name hierarchy. 1p was given rather lightly, the idea is that the student knows the tree structure of domain names. Note that x.fi. domain name does _not_ imply that the host is located in Finland, but that the subdomain was delegated by the Finnish registrar.
• 2) Administration. 1p was given for knowledge of organisations that administer domain names, 1p for the key point in the DNS system: the delegation of administration that the name hierarchy makes possible.
• 3) Functionality. 2p for explanation of how the local name server takes care of finding out the IP for the domain name. A common error was to think that DNS queries are chained. See the course book for the correct procedure.
• 4) Reverse name service. 1p was given for an answer containing something more than just "IP -> domain name" (which yielded .5p).

• DHCP: acronym + explanation (1p), functional discription of the server and relay agent (1p)
• IPv6: stateless autocnfiguration explanation (1p)

The answer is on the first slides of the network management lecture. FCAPS, 0.5p per area, 0.5p per explanation. As you can notice, this sums up to five points only, and thus one point is reserved for general discussion, e.g. on the overlap of certain functions for implementing management of different areas. There are some people who got the FCAPS model right but did not try to discuss it, and some people who discussed it but forgot some functional areas.

Many answers used other types of classifications of network management tasks and I tried to check if the tasks corresponding to the different parts of the FCAPS model were present. Also, an extra point was given to some clever classification.

The main problem on this question for many was the mix-up of network management with control mechanisms implemented in the network. This differentiation can be done for example by thinking of time scales -- the automated mechanisms such as congestion control act in very short time scales, while in network management the time scale focus is from minutes to even days or longer. Thus, discussion on flow and congestion control or ICMP did not yield points.

Some people who actually got to the problem domain (i.e. network management) were stuck in details such as MIBs and SNMP, and forgot the big picture which was the topic of the question. Naturally, SNMP can be used to implement part of configuration management, but it is just a tool. This was especially unlucky since there were a couple of brilliant answers to a question of what SNMP and MIB are, but since this was not the question I could not give points.

Valitustilaisuus

A "valitustilaisuus" will be arranged for questions about the grading. The time and place is: Friday, June 4, at 10 o'clock, room D302.

Results

The grading for the exam is at the end of the table below.

Remember that the final grade is obtained by giving 25% weight to the project grade and 75% weight to the exan grade, i.e., the final grade is given by (exam_grade*3 + project_grade)/4.