docs/diploma

changeset 224:2575c1e8054a

further rework (stuff by Hans-Joerg)
author meillo@marmaro.de
date Tue, 06 Jan 2009 10:13:07 +0100
parents f88853595b7a
children 47af8eb539cf
files thesis/tex/2-MarketAnalysis.tex thesis/tex/3-MailTransferAgents.tex
diffstat 2 files changed, 40 insertions(+), 34 deletions(-) [+]
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     1.1 --- a/thesis/tex/2-MarketAnalysis.tex	Mon Jan 05 20:11:20 2009 +0100
     1.2 +++ b/thesis/tex/2-MarketAnalysis.tex	Tue Jan 06 10:13:07 2009 +0100
     1.3 @@ -1,7 +1,7 @@
     1.4  \chapter{Market analysis}
     1.5  \label{chap:market-analysis}
     1.6  
     1.7 -This chapter analyzes the current situation and future trends, for electronic communication in general and email in particular. First electronic mail's position within other electronic communication technologies is located. Then trends for the whole field of electronic communication are shown. Afterwards opportunities and threats in the market for email are located and trends are identified. The insights of these analysis result in a summary of things that are important for developing future-prove email software.
     1.8 +This chapter analyzes the current situation and future trends, for electronic communication in general and email in particular. First email's position within other electronic communication technologies is located. Then trends for the whole field of electronic communication are shown. Afterwards opportunities and threats in the market and trends for email are identified. The insights of these analysis result in a summary of things that are important for developing future-prove email software.
     1.9  
    1.10  
    1.11  
    1.12 @@ -9,21 +9,21 @@
    1.13  
    1.14  Electronic communication is ``communication by computer'', according to the \name{WordNet} database of \name{Princeton University} \citeweb{wordnet}. Mobile phones and telefax machines should be seen as computers here too. The \name{Science Glossary} of the \name{Pennsylvania Department of Education} describes electronic communication as ``System for the transmission of information using electronic technology (e.g., digital cameras, cellular telephones, Internet, television, fiber optics).'' \citeweb{science-glossary-pa}.
    1.15  
    1.16 -Electronic communication needs no transport of tangible things, only electrons, photons, or radio waves need to be transmitted. Thus electronic communication is fast in general. With having costs mainly for infrastructure and very low costs for data transmission, electronic communication is also cheap communication. As underlying transport infrastructure, mostly the Internet is used; this makes it available nearly everywhere around the world. These properties---fast, cheap, everywhere---make electronic communication well suited for long distance communication.
    1.17 +Electronic communication needs no transport of tangible things, only electrons, photons, or radio waves need to be transmitted. Thus electronic communication is fast in general. With costs mainly for infrastructure and very low costs for data transmission, electronic communication is also cheap communication. As underlying transport infrastructure, primary the Internet is used; thus electronic communication is available nearly everywhere around the world. These properties---fast, cheap, available---make electronic communication well suited for long distance communication.
    1.18  
    1.19 -As globalization proceeds and long distance communication becomes more and more important. The future of electronic communication is bright.
    1.20 +As globalization proceeds and long distance communication becomes more and more important, the future for electronic communication is bright.
    1.21  
    1.22 -Electronic communication includes the following technologies: electronic mail (email), instant messaging (\name{IM}), chats (e.g.\ \NAME{IRC}), short message service (\NAME{SMS}), voice mail, video messages, and Voice over \NAME{IP} (\NAME{VoIP}).
    1.23 +Electronic communication includes the following technologies: electronic mail (email), instant messaging (\name{IM}), chats (e.g.\ \NAME{IRC}), short message service (\NAME{SMS}), multimedia message service (\NAME{MMS}), voice mail, video messages, and Voice over \NAME{IP} (\NAME{VoIP}).
    1.24  
    1.25  
    1.26  \subsection{Classification}
    1.27 -Types of electronic communication can be divided in synchronous and asynchronous communication. Synchronous communication is direct dialog with little delay. Telephone conversation is an example. Asynchronous communication consists of independent messages. Dialogs are possible as well, but not in the same direct fashion. These two groups can also be split by the time needed for data delivery. Synchronous communication requires nearly real-time delivery, whereas for asynchronous communication message delivery times of several seconds or even minutes are sufficient.
    1.28 +Electronic communication technologies can be divided in synchronous and asynchronous communication. Synchronous communication is direct dialog with little delay. Telephone conversation is an example. Asynchronous communication consists of independent messages. Dialogs are possible as well, but not in the same direct fashion. These two groups can also be split by the time needed for data delivery. Synchronous communication requires nearly real-time delivery, whereas for asynchronous communication message delivery times of several seconds or minutes are sufficient.
    1.29  
    1.30 -Another possible separation is to distinguished written and recorded information. Recorded information, like audio or video data, is accessible only in a linear way by spooling and replay. Written information, on the other hand, can be accessed in arbitrary sequence, detail and speed.
    1.31 +Another possible separation is to distinguish recorded and written information. Recorded information, like audio or video data, is accessible only in a linear way by spooling and replay. Written information, on the other hand, can be accessed in arbitrary sequence, detail and speed.
    1.32  
    1.33 -\person{Lenke} and \person{Schmitz} \cite{lenke95} use the same criteria to classify \emph{new media}. They additionally divide into local and remote communication---the latter is presumed here---and by the number of communication participants. As communication technologies for n:m communication (like chat rooms) are usable for 1:1 too (private chat), and ones for 1:1 (email) are usable for n:m (mailing lists), a classification by participant structures is omitted here.
    1.34 +\person{Lenke} and \person{Schmitz} use the same criteria to classify \emph{new media} \cite{lenke95}. They additionally divide into local and remote communication---the latter is presumed here---and by the number of communication participants. As communication technologies for many-to-many communication (like chat rooms) are usable for one-to-one (private chat) too, and ones for one-to-one (email) are usable for many-to-many (mailing lists), a classification by participant structures is omitted here.
    1.35  
    1.36 -Figure \ref{fig:comm-classification} shows a classification of communication technologies sorted by the properties synchronous/asynchronous and written/recorded. Email and \NAME{SMS} are written and asynchronous communication; \NAME{IM} and chats are written information too, but synchronous. Recorded information are voice mail and video messages as examples for asynchronous communication. VoIP is an example for synchronous communication.
    1.37 +Figure \ref{fig:comm-classification} shows a classification of communication technologies sorted by the properties synchronous/asynchronous and written/recorded. Email and \NAME{SMS} are examples for written and asynchronous communication; \NAME{IM} and chats are ones for written but synchronous communication. Voice mail and video messages stand as examples for recorded asynchronous communication. VoIP represents recorded synchronous communication.
    1.38  
    1.39  \begin{figure}
    1.40  	\begin{center}
    1.41 @@ -41,9 +41,9 @@
    1.42  
    1.43  
    1.44  \subsection{Life cycle analysis}
    1.45 -Life cycle analysis are common for products but also for technologies. This one here is for electronic communication technologies. The first dimensions regarded is the life time of the subject. It is segmented into the introduction, growth, mature, saturation, and decline phases. The second dimension can display sales, market share, importance, or similar values. The graph has always an S-line shape, with a slow start, a rapidly increasing first half, the highest level in the third quarter, and a slowly declining end. Reaching the end of the life cycle means, the subject is inherited by its successor or the market situation changed thus making it old fashioned.
    1.46 +Life cycle analysis are common for products but also for technologies. This one here is for electronic communication technologies. The first dimensions regarded is the life time of the subject. It is segmented into the introduction, growth, mature, saturation, and decline phases. The second dimension can display sales, market share, importance, or similar values. The graph has always an S-line shape, with a slow start, a rapidly increasing first half, the highest level in the fourth phase, and a slowly declining end. Reaching the end of the life cycle means, the subject gets inherited by successors or the market situation changed thus it is old fashioned.
    1.47  
    1.48 -The current position on the life cycle of the introduced communication technologies is depicted in figure \ref{fig:comm-lifecycle}. It is important to notice that there is no time line matching for all of them---some life cycles are shorter than others---the shape of the graph, however, is the same.
    1.49 +The current position on the life cycle of some selected communication technologies is depicted in figure \ref{fig:comm-lifecycle}. It is important to notice that the time dimension can be different for each technology---some life cycles are shorter than others---the shape of the graph, however, is the same.
    1.50  
    1.51  \begin{figure}
    1.52  	\begin{center}
    1.53 @@ -53,11 +53,13 @@
    1.54  	\label{fig:comm-lifecycle}
    1.55  \end{figure}
    1.56  
    1.57 -Video messages and voice mail are technologies in the introduction phase. Voice over \NAME{IP} is heavily growing these days. Instant Messaging has reached maturation, but still growing. Email is an example for a technology in the saturation phase. Declining does none of the above mentioned; telefax is an example for a declining technology.
    1.58 +Video messages and voice mail are technologies in the introduction phase. Voice over \NAME{IP} is heavily growing these days. Instant Messaging has reached maturation, but is still growing. Email is an example for a technology in the saturation phase. Telefax is an example for a declining technology.
    1.59  
    1.60  Email ranges in the saturation phase, which is defined by a saturated market, no more products are needed, there is no more growth. This means, email is a technology used by everyone who want to use it. It is a standard technology. The current form of email in the current market is on the top of its life cycle. The future is decline, sooner or later.
    1.61  
    1.62 -But life cycles positions change as the subject or the market changes. An examples is the \name{Flash} animation software. The product's change from a drawing and animation system to a technology for website building, advertising, and movie distribution, and the then changing target market, made it slip back on the life cycle. If the email system would evolve to become the basis for Unified Messaging (see section \ref{sec:unified-messaging}), a similar slip back would be the consequence. An example for a changing market are the \NAME{DVD} standards \NAME{DVD+} and \NAME{DVD$-$}. With the upcoming next generation formats BlueRay and \NAME{HD-DVD}, a much sooner decline of \NAME{DVD+} and \NAME{DVD$-$} started, even before reaching their last development steps in storage size. Such can happen to email too, if Unified Messaging is a revolution to the email system instead of an evolution.
    1.63 +But life cycles positions change as the subject or the market changes. An examples is the \name{Flash} animation software. The product's change from a drawing and animation system to a technology for website building, advertising, and movie distribution, and the thus changing target market, made it slip back on the life cycle. If the email system would evolve to become the basis for Unified Messaging (see section \ref{sec:unified-messaging}), a similar slip back would be the consequence.
    1.64 +
    1.65 +An example for a changing market are the \NAME{DVD} standards \NAME{DVD+} and \NAME{DVD$-$}. With the upcoming next generation formats BlueRay and \NAME{HD-DVD}, a much sooner decline of \NAME{DVD+} and \NAME{DVD$-$} started, even before reaching their last improvement steps in storage size. Such can happen to email too, if Unified Messaging is a revolution to the email system instead of an evolution.
    1.66  
    1.67  
    1.68  
    1.69 @@ -66,44 +68,48 @@
    1.70  Following are the trends for electronic communication. The trends are shown from the view point of \mta{}s. Nevertheless are these trends common for all of the communication technology.
    1.71  
    1.72  \subsubsection*{Consolidation}
    1.73 -There is a consolidation of communication technologies with similar transport characteristics, nowadays. Email is the most flexible kind of asynchronous communication technology already in major use. Hence email is the best choice for transferring messages of any kind today. But in future it probably will be \name{Unified Messaging}, which tries to group all kinds of asynchronous messaging into one communication system. It aims to provide a single transport protocol for all content and a flexible access interface for all kinds of clients. Unified messaging seems to have the potential to be the successor of all asynchronous communication technologies, including email.
    1.74 +There is a consolidation of communication technologies with similar transport characteristics, nowadays. Email is the most flexible kind of asynchronous communication technology in major use. Hence email is the best choice for transferring messages of any kind today. But in future it probably will be \name{Unified Messaging}, which tries to group all kinds of asynchronous messaging into one communication system. It aims to provide a single transport protocol for all content and flexible access interfaces for all kinds of clients. Unified messaging seems to have the potential to be the successor of all asynchronous communication technologies, including email.
    1.75  
    1.76  Today email still is the major asynchronous communication technology and it probably will be it for the next years. As Unified Messaging needs similar transfer facilities to email, it may to be an evolution not a revolution. Hence \mta{}s will still have importance in future, maybe in a modified way.
    1.77  %todo: decentral organization, like the internet -> MTAs are well suited -> further technologies will need something similar
    1.78  
    1.79  
    1.80  \subsubsection*{Integration}
    1.81 -Integration of communication technologies becomes popular. This goes beyond consolidation, because communication technologies of different kinds are bundled together to make communication more convenient for human. User interfaces tend to this direction. The underlying technologies will get grouped, but it seems as if synchronous and asynchronous communication can not be joined together in a sane way, so they will probably only merge at the surface.
    1.82 +Integration of communication technologies becomes popular. This goes beyond consolidation, because communication technologies of different kinds are bundled together to make communication more convenient for human beings. User interfaces tend to go the same direction. The underlying technologies are going to get grouped, but it seems as if synchronous and asynchronous communication can not be joined together in a sane way, so they will probably only merge at the surface.
    1.83  
    1.84  
    1.85  
    1.86  \subsubsection*{Communication hardware}
    1.87 -Hardware needed for communicating comes from two different roots: On the one side, the telephone, now available as mobile phones. This group centers around recorded data and dialog, but messages are supported by the answering machine and \NAME{SMS}. On the other side, mail and its relatives like email, using computers as main hardware. They center around document messages, support dialog communication in Instant Messaging and Voice over \NAME{IP}.
    1.88 +Hardware needed for communicating comes from two different roots: On one side, the telephone, now available as mobile phones. This group centers around recorded data and dialog, but messages are supported by the answering machine and \NAME{SMS}. On the other side, mail and its relatives like email, using computers as main hardware. They center around document messages, but do support dialog communication in Instant Messaging and Voice over \NAME{IP}.
    1.89  
    1.90  The last years finally brought the two groups together, with \name{smart phones} being the merging hardware element. Smart phones are computers in the size of mobile phones or mobile phones with the capabilities of computers, however one likes to see it. They provide both functions, being telephones and computers.
    1.91  
    1.92 -Smart Phones match well the requirements of recorded data, for which they were designed. Writing text is not good to do with the minimal keyboards available for smart phones; speech to text converters may provide help in future. This leaves us with the need for ordinary computers for the field of exchanging documents and as better input hardware for all written information.
    1.93 +Smart Phones match well the requirements of recorded data, for which they were designed. Text is difficult to write with the minimal keyboards available for smart phones; speech to text converters may provide help in future. This leaves us with the need for ordinary computers for the field of exchanging documents and as better input hardware for all written information.
    1.94  
    1.95 -It seems as if a combination of computers and smart phones will be the hardware used for communication in future. Both specialized to the best matching communication technologies, but supporting the others too. Hence facilities for transferring information off and onto the devices will be needed.
    1.96 +It seems as if a combination of desktop computers and smart phones will be the hardware used for communication in future. Both specialized to the best matching communication technologies, but with support for the others, too. Hence facilities for transferring information off and onto the devices will be needed.
    1.97  
    1.98  
    1.99  
   1.100  \subsubsection*{Unified Communication}
   1.101 -\name{Unified communication} is the technology aiming to consolidate and integrate all electronic communication and providing access for all kinds of hardware clients. Unified communication tries to bring the tree trends here mentioned together. The \name{{\smaller PC} Magazine} has the following definition in its Encyclopedia \citeweb{pcmag:uc}: ``[Unified communications is] The real-time redirection of a voice, text or e-mail message to the device closest to the intended recipient at any given time.'' The main goal is to integrate all kinds of communication (asynchronous and synchronous) into one system, hence this requires real-time delivery of data.
   1.102 +\name{Unified communication} is the technology aiming to consolidate and integrate all electronic communication and providing access for all kinds of hardware clients. Unified communication tries to bring the three trends here mentioned together. The \name{{\smaller PC} Magazine} has the following definition in its Encyclopedia: ``[Unified communications is t]he real-time redirection of a voice, text or e-mail message to the device closest to the intended recipient at any given time.'' \citeweb{pcmag:uc}. The main goal is to integrate all kinds of communication (asynchronous and synchronous) into one system, hence this requires real-time delivery of data.
   1.103  
   1.104 -According to Michael \person{Osterman} \cite{osterman08}, unified communications is already possible as far as various incoming sources are routed to one storage where messages can be accessed by one or a few clients. But a system with an ``intelligent parser of a single data stream into separate streams that are designed to meet the real-time needs of the user'' is a goal for the future, he says.
   1.105 +According to Michael \person{Osterman}, unified communications is already possible as far as various incoming sources are routed to one storage where messages can be accessed by one or a few clients \cite{osterman08}. But a system with an ``intelligent parser of a single data stream into separate streams that are designed to meet the real-time needs of the user'' is a goal for the future, he says.
   1.106  
   1.107 -The question is, if the integration of synchronous and asynchronous message transfer does make sense. A communication between one person talking on the phone and the other replying using his instant messenger, certainly does, if the text-to-speech and speech-to-text converting is fast and the quality good enough. But transferring large video messages and real-time communication data with the same technology, possibly does not.
   1.108 +The question is, whether the integration of synchronous and asynchronous communication does make sense. A communication between one person talking on the phone and the other replying using his instant messenger, certainly does (assumed the text-to-speech and speech-to-text converting is fast and the quality good enough). But transferring large video messages and real-time communication data with the same technology, possibly does not.
   1.109  
   1.110  
   1.111  
   1.112  \subsubsection*{Unified Messaging}
   1.113  \label{sec:unified-messaging}
   1.114 -\name{Unified messaging}, although often used exchangeable with unified communications, is only a subset of it. It does not require real-time data transmission and is therefor only usable for asynchronous communication \citeweb{wikipedia:uc}. Unified messaging's function is basically: Receiving incoming messages from various channels, converting it to a common format, and storing it into a single space. The stored messages can then be accessed from different devices. \citeweb{wikipedia:um}
   1.115 +\name{Unified messaging}, although often used exchangeable with unified communications, is only a subset of it. It does not require real-time data transmission and is therefore only usable for asynchronous communication \citeweb{wikipedia:uc}. Unified messaging's function is basically: Receiving incoming messages from various channels, converting them into a common format, and storing them into a single memory. The stored messages can then be accessed from different devices \citeweb{wikipedia:um}.
   1.116  
   1.117 -The easiest way of unified messaging is to base it on either email and convert all input sources to email messages (as attachments for instance) and store them in the user's mail box. Or use the telephone system as basis and convert text messages to speech. Both is no problem for asynchronous communication.
   1.118 +The easiest way of Unified Messaging is to base it on either email and convert all input sources to email messages (as attachments for instance) and store them in the user's mail box, or use the telephone system as basis and convert text messages to speech. Both is technically possible for asynchronous communication.
   1.119  
   1.120 -Finally a critical voice from Jesse \person{Freund}, who voted unified messaging on top of a hype list for \name{Wired.com}, ten years ago \cite{wired:hype}. His description of the technology ended with the humorous sentences: ``Unified messaging is a nice idea, but a tough sell: The reason you bought a cell phone, a pager, and a fax/modem is because each does its job well. No one wants to download voice mail as a series of RealAudio messages or sit through a voice mail bot spelling out email, complete with `semicolon dash end-parenthesis' for ;-).''
   1.121 +Finally, a critical voice from Jesse \person{Freund}, who voted Unified Messaging on top of a hype list, published by \name{Wired.com} ten years ago. His description of the technology ended with the humorous sentences:
   1.122 +\begin{quote}
   1.123 +Unified messaging is a nice idea, but a tough sell: The reason you bought a cell phone, a pager, and a fax/modem is because each does its job well. No one wants to download voice mail as a series of RealAudio messages or sit through a voice mail bot spelling out email, complete with `semicolon dash end-parenthesis' for ;-).
   1.124 +\hfill\cite{wired:hype}
   1.125 +\end{quote}
   1.126  
   1.127  
   1.128  
   1.129 @@ -112,14 +118,14 @@
   1.130  
   1.131  \section{Electronic mail}
   1.132  
   1.133 -After viewing the whole market of electronic communication, a zoom in to the market of electronic mail follows. Email is an asynchronous communication technology that transports textual information primary. This thesis is about a \mta, so the market situation for email is important. Interesting questions are: Is email future-safe? How will electronic mail change? Will it change at all? Which are the critical parts? These questions matter when deciding on the directions for further development of an \MTA. They are discussed in this section.
   1.134 +After viewing the whole market of electronic communication, a zoom into the market of electronic mail follows. Email is an asynchronous communication technology that transports textual information primary. This thesis is about a \mta, so the market situation for email is important. Interesting questions are: Is email future-safe? How will electronic mail change? Will it change at all? Which are the critical parts? These questions matter when deciding on the directions for further development of an \MTA. They are discussed in this section.
   1.135  
   1.136  
   1.137  
   1.138  \subsection{SWOT analysis}
   1.139  \label{sec:swot-analysis}
   1.140  
   1.141 -A \NAME{SWOT} analysis regards the strengths and weaknesses of a subject against the opportunities and threats of its market. The slightly altered form called \name{Dialectical {\smaller SWOT} analysis}, which is used here, is described in \cite{powerof2x2}. \NAME{SWOT} analysis should always focus on a specific specific goal to reach with the product. In this case, the main goal is to make email future-safe.
   1.142 +A \NAME{SWOT} analysis regards the strengths and weaknesses of a subject against the opportunities and threats of its market. The slightly altered form called \name{Dialectical {\smaller SWOT} analysis}, which is used here, is described in \cite{powerof2x2}. \NAME{SWOT} analysis should always focus on a specific goal to reach with the product. In this case, the main goal is to make email future-safe.
   1.143  
   1.144  The two dimension---a subject and the market---are regarded in relation to each other by the analysis. Here the analysis shall be driven by the market's dimension. Thus first opportunities of the market are identified and split into being stengths or weaknesses of email. Then the same is done for threats of the market.
   1.145  
   1.146 @@ -137,14 +143,14 @@
   1.147  
   1.148  \subsubsection*{Opportunities}
   1.149  
   1.150 -Opportunities of the market are large data transfers, coming from multimedia content, which becomes popular. If email is used as basis for unified messaging, lots of voice and video mail will need to be transferred. Email is weak related to that kind of data: the data needs to be encoded to \NAME{ASCII} and stresses mail servers a lot.
   1.151 +Opportunities of the market are large data transfers, coming from multimedia content, which becomes popular. If email is used as basis for Unified Messaging, lots of voice and video mail will be transferred. Email is weak related to that kind of data: the data needs to be encoded to \NAME{ASCII} and stresses mail servers a lot.
   1.152  
   1.153  The use of various hardware to access mail is another opportunity of the market. But more hardware gets involved and the networks get more complex. Thus the software and infrastructure needed to transfer mail within the growing network might be a weakness of the email system. %fixme: think about that
   1.154  
   1.155  An opportunity of the market and at the same time a strength of electronic mail is its standardization. Few other communication technologies are standardized and thus freely available in a similar way. %fixme: ref
   1.156  Another opportunity and strength is the modular and extensible structure of electronic mail; it can easily evolve to new requirements. %fixme: ref
   1.157  
   1.158 -The increasing integration of communication channels, is an opportunity for the market. But deciding whether it is a weakness or strength of email is difficult. It is a weakness because the impossible integration of synchronous stream data and the bad integration of large binary data. But it is also a strength, because arbitrary asynchronous communication data already can be integrated. On the other hand, the integration might be a threat too, because it often leads to complexity of software. Complex software is more error prone and thus less reliable. This however could again be a strength of electronic mail because of its modular design that decreases complexity.
   1.159 +The increasing integration of communication channels, is an opportunity for the market. But deciding whether it is a weakness or strength of email is difficult. Due to the impossibility to integrate synchronous stream data and large binary data is it a weakness. But it is also a strength, because arbitrary asynchronous communication data already can be integrated. On the other hand, the integration might be a threat too, because it often leads to complexity of software. Complex software is more error prone and thus less reliable. This however could again be a strength of electronic mail because of its modular design that decreases complexity.
   1.160  
   1.161  Figure \ref{fig:email-swot} displays the \NAME{SWOT} analysis in a handy overview. It is obvious to see, that the opportunities outweigh. This is an indicator for a still increasing market. %fixme: ref
   1.162  
   1.163 @@ -186,9 +192,9 @@
   1.164  
   1.165  Nowadays, dial-up Internet access became rare; the majority has broadband Internet access paying a flat rate for it. Hence the time being online not affect costs anymore, even traffic is unlimited. Today it is possible to have an own mail server running at home. The technical problem remaining is the changing \NAME{IP} addresses one gets assigned every 24 hours. But this is solvable with one of the dynamic \NAME{DNS} services; they provide the mapping of a fixed domain name to the changing \NAME{IP} addresses.
   1.166  
   1.167 -Home servers become popular for central data storage and multimedia services, these days. Being assembled of energy efficient elements, power consumption is no big problem anymore. These home servers will replace video recorders and \NAME{CD} music collections in the near future. It is also realistic that they will manage heating systems and intercoms too. Given the future leads to this direction, it is a logical step to have email and other communication provided by the own home server as well.
   1.168 +Home servers become popular for central data storage and multimedia services, these days. Being assembled of energy efficient elements, power consumption is no big problem anymore. These home servers will replace video recorders and \NAME{CD} music collections in the near future. It is also realistic that they will manage heating systems and intercoms too. Given the future leads to this direction, it will be a logical step to have email and other communication provided by the own home server as well.
   1.169  
   1.170 -After \mta{}s have not been popular for users in the last years, the next years might bring them back to the users. Maybe in a few years nearly everyone will have one running at home.
   1.171 +After \mta{}s have not been popular for users in the past years, the next years might bring the \MTA{}s back to the users. Maybe in a few years nearly everyone will have one running at home.
   1.172  
   1.173  
   1.174  \subsubsection*{Pushing versus polling}
   1.175 @@ -231,11 +237,11 @@
   1.176  It still lets the specialist do complex and detailed configuration, and also offering a simple configuration interface to novices. \sendmail\ took this approach with the \name{m4} macros. %fixme: add ref
   1.177  Further more is it well suited to provide various wrappers with different user interfaces (e.g.\ graphical programs, websites, command line programs; all of them either in a questionnaire style or interactive).
   1.178  
   1.179 -When \MTA{}s become popular on home servers and maybe even on workstations and smart phones, then performance will be less important. Providers need \mta{}s that process large amounts of mail in short time. Home servers or workstations however, do not see that much mail; they need to handle only tens or hundreds of email messages per hour. Thus performance will probably not be a main requirement for an \MTA\ in future, if they mainly run on private machines.
   1.180 +When \MTA{}s become popular on home servers and maybe even on workstations and smart phones, then performance will be less important. Providers need \mta{}s that process large amounts of mail in short time. However, there is no need for home servers and workstations to handle that much mail; they need to process far less email messages per time unit. Thus performance will probably not be a main requirement for an \MTA\ in future, if they mainly run on private machines.
   1.181  
   1.182 -New mailing concepts and architectures like push email or \name{Internet Mail 2000} will, if they succeed, require \mta{}s to adopt the new technology. \MTA{}s that are not able to change are going to be sorted out by evolution. Thus it is important to not focus too much on one use case, but to stay flexible. Allman saw the flexibility of \sendmail\ one reason for its huge success (see section \ref{sec:sendmail}).
   1.183 +New mailing concepts and architectures like push email or \name{Internet Mail 2000} will, if they succeed, require \mta{}s to adopt the new technology. \MTA{}s that are not able to change are going to be sorted out by evolution. Thus it is important not to focus too much on one use case, but to stay flexible. Allman saw the flexibility of \sendmail\ one reason for its huge success (see section \ref{sec:sendmail}).
   1.184  
   1.185 -Another important requirement for all kinds of software will be security. There is a constant trend coming from completely non-secured software, in the 70s and 80s, over growing security awareness, in the 90s, to security being a primary goal, now. This leads to the conclusion that software security will be even more important in the next years. As more clients get connected to the Internet and especially more computers are listening for incoming connections (like an \MTA\ in a home server), there are more possibilities to break into systems. Securing of software systems will be done with increasing effort in future.
   1.186 +Another important requirement for all kinds of software will be security. There is a constant trend coming from completely non-secured software, in the 70s and 80s, over growing security awareness, in the 90s, to security being a primary goal, now. This leads to the conclusion that software security will be even more important within the next years. As more clients get connected to the Internet and especially more computers are listening for incoming connections (like an \MTA\ in a home server), there are more possibilities to break into systems. Securing of software systems will be done with increasing effort in future.
   1.187  
   1.188  ``Plug-and-play''-able hardware with preconfigured software running can be expected to become popular. Like someone buys a set-top box to watch Pay-\NAME{TV} today, he might be buying a box acting as mail server in a few years. He plugs the power cable in, inserts his email address in a web interface and selects the clients (workstation computers or smart phones) to which mail should be send and from which mail is accepted to receive. That's all. It would just work then, like everyone expects it from a set-top box today. Secure and robust software is a pre-requisite for such boxes to make that vision possible.
   1.189  
     2.1 --- a/thesis/tex/3-MailTransferAgents.tex	Mon Jan 05 20:11:20 2009 +0100
     2.2 +++ b/thesis/tex/3-MailTransferAgents.tex	Tue Jan 06 10:13:07 2009 +0100
     2.3 @@ -46,7 +46,7 @@
     2.4  \subsubsection*{``Real'' MTAs}
     2.5  There is a third type of \mta{}s in between the minimalistic \name{relay-only} \MTA{}s and the feature loaded \name{groupware}. Those programs may be named ``real \MTA{}s'', or ``proper \MTA{}s'', though there is no common name. They are what is meant with the term ``\mta''---programs that transfer mail between hosts.
     2.6  
     2.7 -Common to them is their focus on transferring email, while being able to act as \name{smart host}. Their variety ranges from ones mostly restricted to mail transfer (e.g.\ \qmail) to others having interfaces for adding further mail processing modules (e.g.\ \postfix). This group covers everything in between the other two groups.
     2.8 +Common to them is their focus on transferring email, while being able to act as \name{smart host}s. Their variety ranges from ones mostly restricted to mail transfer (e.g.\ \qmail) to others having interfaces for adding further mail processing modules (e.g.\ \postfix). This group covers everything in between the other two groups.
     2.9  
    2.10  ``Real \MTA{}s'' are of importance in this document. All programs selected for the comparison in the following section are ``real \MTA{}s''. \masqmail\ is one too.
    2.11  
    2.12 @@ -107,7 +107,7 @@
    2.13  
    2.14  The program was written by Eric \person{Allman} as the successor of his program \name{delivermail}. \person{Allman} was not the only one working on the program. Other people developed own versions of it and a variety of flavors came up, especially in the late eighties when Allman was inactive. %fixme: ref
    2.15  
    2.16 -\sendmail\ is focused on transferring mails between different protocols and networks, this lead to a very flexible, though complex, configuration.
    2.17 +\sendmail\ designed to transfer mails between different protocols and networks, this lead to a very flexible, though complex, configuration.
    2.18  
    2.19  It was first released with \NAME{BSD} 4.1c in 1983. The latest version is 8.14.3 from May 2008. The program is distributed under the \name{Sendmail License} as both, \freesw\ and proprietary software.
    2.20