Task 1:
    a)The Internet used to consist of only 4 Systems. It has since
    grown considerably, making the Client-Server model obsolete in
    many cases. This increase in end systems has lead to increasingly
    widespread adoption of distributed models of computing and
    communication. Also, it has made an extension of the IP Addressspace
    unavoidable.  b)There are many different areas where new technology
    is needed.
        * Back in the day only big Mainframes had internet access. The
        internet was not as accessible to the general public making
        security a lesser priority. The increase in personal computing and
        personal internet access entails a whole new array of demands,
        such as e.g. privacy, security, reliability, scalability.  *
        Many (mobile) devices have Internet connectivity nowadays. Hence,
        wireless technology and corresponding protocols, and scalability
        solutions are necessary. This extends to endsystems as well
        as infrastructure.  * Nowadays, the internet is often used for
        personal reasons, such as social networking etc as opposed to
        being a research or corporate network.  * Data transmission has
        changed in several areas. For mobility reasons many devices use
        wireless technologies. Also cablebound protocols have changed
        significantly in the past, in respect to efficiency and a growing
        number of endsystems (users), see IPv6.
    c)
        The most common model for personal internet access is ADSL
        by far. This skews the traffic on personal endsystems towards
        downstream heavy applications. For a lot of applications, this
        makes sense, as the user generally wants to pull in information
        from some remote source, e.g. a webserver or "the cloud". But
        especially in recent years, upstream has become more and more
        relevant for users, since the focus is often placed on user
        contributed data. This comes in many forms, like for example
        uploading a photo album to a social network or doing live
        (potentially mobile) audio (and often even video) streaming.
        With increasing use of such features, capacities of centralized
        ressources, e.g. webservers, are used up very quickly, which is
        why many services have started incorporating P2P technology. Many
        video streaming services use the upstream bandwidth of the users
        (peers) to broadcast their data in order to lessen ressource
        requirements on their backends. This is also true for intrisically
        person-to-person based services, like instant messengers, voip
        calls etc. Modern P2P filesharing networks are pretty much the
        epitome of this development, trading in distributed usage of
        ressources for increased robustness of the network (eliminating
        central servers as a single point of failure).

Task 2:
    a)  * Scalability:
            Modern internet applications generally have a lot of users and
            high interaction between these users. This is very ressource
            intensive, especially in a centralized model. This problem
            is not always remedied by throwing money at it (i.e. buy
            more servers etc), which often makes a deeper analysis
            necessary. New protocols, more efficient procedures and
            potentially P2P technology are often needed.
        * Security:
            The internet being very much open to the public introduces
            a whole new category of security considerations. Protocols
            have to be designed robustly, and implemented in a secure
            fashion. Authentication technologies are indispensable. And
            a whole new class of attacks, like e.g. DDoS attacks, have
            to be dealt with properly. The increasing proliferation of
            "social networking" aspects in internet applications also
            calls into question issues of privacy.
        * Reliability:
            The applications should always be accessible and should act
            as expected. This means that single points of failure should
            be eliminated or at least minimized. Also, the application
            should be built in a robust fashion in order to be able to
            withstand unexpected failures of components without degrading
            the user experience.
    b)  Obviously, Scalability and Reliability are closely
    linked. Increasing realiability, for example by introducing
    redundancies, makes scalability harder, because the redundancy
    solutions have to scale as well. Also, redundancies can pose a
    security risk, because the failure mitigation procedures could
    pontentially be exploited. Thus a more reliable system is often harder
    to make secure. Security and Scalability are also somewhat related,
    as security constraints forbid certain designs that would make an
    application more scalable, for example possibly sensitive user data
    can not necessarily be stored in a distributed system because of
    privacy issues. Also, security technologies like for example SSL/TLS
    cause additional overhead, thus further complicating the challenge
    of scalability.
        Furthermore, none of these challenges are necessarily more
        important than any other, because failing to overcome any one
        of them will cause the entire application to fail. But as they
        all influence each other, there cannot be a perfect solution. A
        compromise has to be made.
    c)  The problems of security and scalability are very important
    ones. If the users can't be/aren't confident in the security and
    most of all the privacy of their data, they will not be as willing
    to submit it, potentially causing loss of income. Also, the service
    must be scalable, because the goal is to get as many users as possible
    using the services as much as possible. Thus, if the application is
    not scalable, its success will be its failure. Long waiting times,
    maintenance downtimes etc all degrade the user experience and are
    thus detrimental to my income.

Task #3:
    a) Even though most end user nowdays have flat rates, traffic for
    service providers is expensive. By letting the consumers redristrube
    the content the service can save a significant amount of money. i.e
    every megabyte one peer uploads to another is a megabyte the service
    provider doesn't have to pay for.  Similar things can be said
    about cpu time for cpu-heavy P2P systems.  These advantages transfer
    to the end user of course, by virtue of a pontentially faster/more
    responsive service (especially in data distribution applications).
    b) Distributing data is one of the best use cases for P2P-systems. Useing
    BitTorrent for example to disribute "World of Warcraft" patches
    or Linux Distributions has almost no downsides for consumers
    and only upsides (minimizing traffic costs) for the provider.
    The Client/Server model thought still has its upsides when it
    comes to latency or cases where one needs absolute control and 100%
    consistancy in the data.
    c) Managing the balance of a skype account
    in the cloud might not be a good idea as users could easily change
    it - or if not for themself at least for other users. Storing the
    username in the cloud would be rather complicatied because there
    has to be a way to lookup and exchange public keys. (And one don't
    want to endeavor a second communcition tool (like email) to exchange
    that information) However the most important reasons for Skype to
    rely on central servers is to keep control over the system. (This,
    and some weird obfuscation of the protocol.)