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Five Less Taught
Topics in Data Communications University of Washington – EE461 – Spring 2010
Mohsen BANAN
E-mail: http://mohsen.banan.1.byname.net/ContactMe
http://mohsen.banan.1.byname.net/Records/20100601 June 1, 2010
Varbatim Copying Permitted Part Outlines
Outline
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What Are We Here For?
Themes.
Messaging Model and Terminology
PIC
Some Basic MHS (email) Terminology Review
Since we are going to use email as the example through out, let’s quickly review some basic terms. Part I
The End-To-End Argument
Part I: End-To-End Argument
Relevant Literature.
E2E Paper Key Point 1
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. Because, 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.
E2E Paper Key Point 2
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. Advantages of moving application-specific functions up out of the core include:
E2E Paper Key Point 3
The most important benefit of the end to end arguments is that they preserve the flexibility, generality, and openness of the Internet. Movement to put more functions inside the network jeopardizes that generality and flexibility as well as historic patterns of innovation. A new principle evident already is that elements that implement functions that are invisible or hostile to the end to end application, in general, have to be “in” the network, because the application cannot be expected to include that intermediate element voluntarily.
Engineering Summary.
Email(SMTP) vs Texting (SMS) – E2E vs In-The-Core.
End-to-End (E2E) and Network-Address-Translators(NTAs)
Illich’s Concept of Convivial Tools
Tools are intrinsic to social relationships. An individual relates himself in action to his society through the use of tools that he actively masters, or by which he is passively acted upon. To the degree that he masters his tools, he can invest the world with his meaning; to the degree that he is mastered by his tools, the shape of the tool determines his own self-image. Convivial tools are those which give each person who uses them the greatest opportunity to enrich the environment with the fruits of his or her vision. Industrial tools deny this possibility to those who use them and they allow their designers to determine the meaning and expectations of others. Most tools today cannot be used in a convivial fashion.
Was: E2E Argument – Now: The Autonomous Services Argument.
Facebook is Very Central and Very Much non E2E – What Are We To Do?.
The Autonomous Libre Services Argument.
Part II
Characteristics of Successful Protocols
Part II: Characteristics of Successful Protocols
Relevant Literature.
Mentioned Success Factors.
A Protocol’s Position in The Protocol Hour Glass
PIC
Other Success Factors.
Part III
Patents and Protocols
Part II: Patents and Protocols
Relevant Literature.
What Are Protocols? – What Are Patents?
How Patents Fit Into Protocols
Patents are applied to software, not to protocols. It is not possible to patent a protocol; in general only a process or an algorithm can be patented. However, a protocol may include a patented algorithm as an integral part of its specification. In this case, any software implementation of the protocol requires the use of patented software. That is, a patented process is an inherent part of the protocol. Even if a protocol does not explicitly decree the use of a specific patented software process, it may still be the case that any practical implementation of the protocol requires the use of patented software components. The protocol could in principle be implemented in a way which avoids the use of patented software; in practice, however, the result would be a significantly inferior implementation, for example in terms of efficiency.
How Patents Fit Into Protocol Dev-elopement Process
The Patent Controversy
Part IV
The Correct Ultimate Protocol Implementation
Part IV: The Correct Ultimate Protocol Implementation
Relevant Literature.
What Is Correct Ultimate?
MTA Comparisons – qmail my choice of ultimate MTA.
The Robustness Principle.
Be liberal in what you accept, and conservative in what you send
Software should be written to deal with every conceivable error, no matter how unlikely; sooner or later a packet will come in with that particular combination of errors and attributes, and unless the software is prepared, chaos can ensue. In general, it is best to assume that the network is filled with malevolent entities that will send in packets designed to have the worst possible effect.
Unix Philosophy.
The Right qmail Server Configuration
PIC
The Right qmail Autonomous Client Configuration
PIC
qmail Server Configuration Expanded for Mobile Email
PIC
qmail Autonomous Client Configuration Expanded for Mobile Email
PIC
Part V
Some Acknowledged and Some Unacknowledged Internet Errors
Part V: Some Acknowledged and Some Unacknowledged Internet Errors
IP Address Exhaustion.
Longer Term Ramifications of Simple Protocols.
Domain Name Notation Is Backwards.
mailto:desk@hommer.1.simposon.byname.net should have been mailto:net.byname.simposon.1.hommer@desk We can not complete urls. Actually that is quite important!
Colophon
Questions/Comments/Discussion