Electronic Mail and Computer-Mediated Communication

SU course*:48 KTH course 2I1261

Exam 16 September 1993 with examples of correct answers

Note: If you want the exam questions in English, you must inform Jacob Palme about this at least two weeks before the exam.

  1. Swedish question: Forskning kring införande av elektronisk post visar att vissa anställda får mer inflytande och andra mindre inflytande än tidigare. Vilka är dessa grupper? (5 poäng)
    English question: Research on the introduction of e-mail shows that some employees get more influence and other employees get less influence than before. Which are these groups? (5 points)

    Correct answer: More influence: Younger employees, employees with computer exerience, non-supervisors, timid and quiet people. Less influence: Middle managment, older employees.

  2. Swedish question: Varför är det ibland fördelaktigt att använda sig av s.k. öppen-nyckelkryptering? Nämn några vanliga användningar av sådan kryptering. (6 poäng)
    English question: Why is it sometimes useful to use so-called open-key-encryption? Mention some common uses of such encryption techniques. (6 points)

    Correct answer: Advantages: You do not have to find a separate channel for the secure distribution of keys which have to be kept secret. The same key can be used for letters to a certain recipients from different senders. Common uses: Transfer of symmetric encryption keys, identification, digital signatures, digital seals.

  3. Swedish question: Vad menas med att ett protokoll är uppbyggt i flera lager (nivåer)? Vilken information kommuniceras vart i de olika nivåerna? På vilket sätt kan man säga att X.400 uppbyggt i två sub-lager inom applikationslagret? Beskriv vilka enheter som kommunicerar vilka objekt i de två sub-lagren. (6 poäng)
    English question: What is meant by saying that a protocol is built in several layers? What information is communicated to whom in each layer? In which way can you say that X.400 is built with two sub-layers within the application layer? Describe which units communicate which objects in the two sub-layers of X.400.

    Correct answer: Lower layes will see information belonging to higher layers as a stream of bits, to which the lower layers add information, which to even lower layers will again be seen as a stream of bits. Higher layers communicate with higher layers indirectly through the lower layers.

    X.400 can be seen as a protocol with two sublayers, one for MTS (P1, P3) and one for IPM (P2, P22). P2 is a protocol between UA-s, P1 is a protocol between MTA-s.

  4. Swedish question: Beskriv hur och varför s.k. "name servers" används när man skall skicka elektronisk post till en mottagare i en främmande domän. Vad är det man söker reda på? Nämn också om en funktion som gör name servers effektivare genom att reducera antalet uppkopplingar. (OBS: "name server" är inte exakt samma sak som ett X.500 katalogsystem, även om funktionen har stora likheter.) (4 poäng)
    English question: Describe how and why so ckalled "Name servers" are used when sending electronic mail to a recipient in a foreign domain. What is it you retrieve from the name servers? Mention also a functionality which can make name servers more efficient by reducing the number of necessary interconnections. (NOTE: "Name server" is not the same thing as X.500 directory systems, even though there are similarities.) (4 points)

    Correct answer: To translate a domain address into an IP address so that mail can be sent directly to the IP address of the receiving computer. Name servers can call each other and can cache the answers they get, so that a new question for the same domain name can be answered more rapidly.

  5. Swedish question: Ange några sätt på vilka man kan ha nytta av att varje meddelande har ett globalt unikt identifieringsnummer, IPMessage-ID. (6 poäng)
    English question: Specify some ways in which it is useful if each message has a globally unique identifying number, the IPMessage-ID. (6 points)
    Correct answer: To eliminate duplicates of the same message, to stop loops of circulating nested distribution lists, to transfer references between messages such as In-Reply-To, References, Obsoletes/Supersedes.