IP: Rethinking the design of the Internet: The end to end argumentsvs. the brave new world (fwd)

Eugene Leitl Eugene.Leitl@lrz.uni-muenchen.de
Fri, 5 Oct 2001 12:59:41 +0200 (MET DST)

---------- Forwarded message ----------
Date: Fri, 05 Oct 2001 02:37:45 -0400
From: David Farber <dave@farber.net>
Reply-To: farber@cis.upenn.edu
To: ip-sub-1@majordomo.pobox.com
Subject: IP: Rethinking the design of the Internet: The end to end
    arguments vs. the  brave new world

>"Rethinking the design of the Internet:
>The end to end arguments vs. the brave new world"
>Marjory S. Blumenthal Computer Science & Telecommunications Board, NRC
>David D. Clark M.I.T. Lab for Computer Science ddc@lcs.mit.edu
>A version of this paper to appear in the ACM Transactions on Internet
>A version also to appear in Communications Policy in Transition: The
>Internet and Beyond,
>edited by Benjamin Compaine and Shane Greenstein, MIT Press, Sept. 2001
>This paper looks at the Internet and the changing set of requirements
>for the Internet that are emerging as it becomes more commercial, more
>oriented towards the consumer, and used for a wider set of purposes. We
>discuss a set of principles that have guided the design of the Internet,
>called the end to end arguments, and we conclude that there is a risk
>that the range of new requirements now emerging could have the
>consequence of compromising the Internet's original design principles.
>Were this to happen, the Internet might lose some of its key features,
>in particular its ability to support new and unanticipated applications.
>We link this possible outcome to a number of trends: the rise of new
>stakeholders in the Internet, in particular Internet Service Providers;
>new government interests; the changing motivations of the growing user
>base; and the tension between the demand for trustworthy overall
>operation and the inability to trust the behavior of individual users.
>The end to end arguments are a set of design principles that
>characterize (among other things) how the Internet has been designed.
>These principles were first articulated in the early 1980s, and they
>have served as an architectural model in countless design debates for
>almost 20 years.
>The end to end arguments concern how application requirements should be
>met in a system. When a general purpose system (for example, a network
>or an operating system) is built, and specific applications are then
>built using this system (for example, e-mail or the World Wide Web over
>the Internet), there is a question of how these specific applications
>and their required supporting services should be designed. The end to
>end arguments suggest that specific application-level functions usually
>cannot, and preferably should not, be built into the lower levels of the
>system-the core of the network. The reason why was stated as follows in
>the original paper:
>"The function in question can completely and correctly be implemented
>only with the knowledge and help of the application standing at the
>endpoints of the communications system. Therefore, providing that
>questioned function as a feature of the communications systems itself is
>not possible."
>In the original paper, the primary example of this end to end reasoning
>about application functions is the assurance of accurate and reliable
>transfer of information across the network. Even if any one lower level
>subsystem, such as a network, tries hard to ensure reliability, data can
>be lost or corrupted after it leaves that subsystem. The ultimate check
>of correct execution has to be at the application level, at the
>endpoints of the transfer. There are many examples of this observation
>in practice.
>Even if parts of an application-level function can potentially be
>implemented in the core of the network, the end to end arguments state
>that one should resist this approach if possible. There are a number of
>advantages of moving application-specific functions up out of the core
>of the network and providing only general-purpose system services there.
>o The complexity of the core network is reduced, which reduces costs and
>facilitates future upgrades to the network.
>o Generality in the network increases the chances that a new application
>can be added without having to change the core of the network.
>o Applications do not have to depend on the successful implementation
>and operation of application-specific services in the network, which may
>increase their reliability.
>Of course, the end to end arguments are not offered as an absolute.
>There are functions that can only be implemented in the core of the
>network, and issues of efficiency and performance may motivate
>core-located features. Features that enhance popular applications can be
>added to the core of the network in such a way that they do not prevent
>other applications from functioning. But the bias toward movement of
>function "up" from the core and "out" to the edge node has served very
>well as a central Internet design principle.
>As a consequence of the end to end arguments, the Internet has evolved
>to have certain characteristics. The functions implemented "in" the
>Internet-by the routers that forward packets-have remained rather simple
>and general. The bulk of the functions that implement specific
>applications, such as e-mail, the World Wide Web, multi-player games,
>and so on, have been implemented in software on the computers attached
>to the "edge" of the Net. The edge-orientation for applications and
>comparative simplicity within the Internet together have facilitated the
>creation of new applications, and they are part of the context for
>innovation on the Internet.
>Moving away from end to end
>For its first 20 years, much of the Internet's design has been shaped by
>the end to end arguments. To a large extent, the core of the network
>provides a very general data transfer service, which is used by all the
>different applications running over it. The individual applications have
>been designed in different ways, but mostly in ways that are sensitive
>to the advantages of the end to end design approach. However, over the
>last few years, a number of new requirements have emerged for the
>Internet and its applications. To certain stakeholders, these various
>new requirements might best be met through the addition of new mechanism
>in the core of the network. This perspective has, in turn, raised
>concerns among those who wish to preserve the benefits of the original
>Internet design.
>Continued at:

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