12 Networking Truths: The Twelve Networking Truths
Twelve fundamental truths and paradoxes of network design.
Callon, R., "The Twelve Networking Truths", RFC 1925, DOI 10.17487/RFC1925, April 1996, <https://www.rfc-editor.org/info/rfc1925>.
@misc{rfc1925,
series = {Request for Comments},
number = 1925,
howpublished = {RFC 1925},
publisher = {RFC Editor},
doi = {10.17487/RFC1925},
url = {https://www.rfc-editor.org/info/rfc1925},
author = {R. Callon},
title = {{The Twelve Networking Truths}},
pagetotal = 3,
year = 1996,
month = apr,
} RFC text
Contents
Network Working Group R. Callon, Editor
Request for Comments: 1925 IOOF
Category: Informational 1 April 1996
The Twelve Networking Truths
Status of this Memo
This memo provides information for the Internet community. This memo
does not specify an Internet standard of any kind. Distribution of
this memo is unlimited.
Abstract
This memo documents the fundamental truths of networking for the
Internet community. This memo does not specify a standard, except in
the sense that all standards must implicitly follow the fundamental
truths.
Acknowledgements
The truths described in this memo result from extensive study over an
extended period of time by many people, some of whom did not intend
to contribute to this work. The editor merely has collected these
truths, and would like to thank the networking community for
originally illuminating these truths.
1. Introduction
This Request for Comments (RFC) provides information about the
fundamental truths underlying all networking. These truths apply to
networking in general, and are not limited to TCP/IP, the Internet,
or any other subset of the networking community.
2. The Fundamental Truths
(1) It Has To Work.
(2) No matter how hard you push and no matter what the priority,
you can't increase the speed of light.
(2a) (corollary). No matter how hard you try, you can't make a
baby in much less than 9 months. Trying to speed this up
*might* make it slower, but it won't make it happen any
quicker.
(3) With sufficient thrust, pigs fly just fine. However, this is
not necessarily a good idea. It is hard to be sure where they
are going to land, and it could be dangerous sitting under them
as they fly overhead.
(4) Some things in life can never be fully appreciated nor
understood unless experienced firsthand. Some things in
networking can never be fully understood by someone who neither
builds commercial networking equipment nor runs an operational
network.
(5) It is always possible to aglutenate multiple separate problems
into a single complex interdependent solution. In most cases
this is a bad idea.
(6) It is easier to move a problem around (for example, by moving
the problem to a different part of the overall network
architecture) than it is to solve it.
(6a) (corollary). It is always possible to add another level of
indirection.
(7) It is always something
(7a) (corollary). Good, Fast, Cheap: Pick any two (you can't
have all three).
(8) It is more complicated than you think.
(9) For all resources, whatever it is, you need more.
(9a) (corollary) Every networking problem always takes longer to
solve than it seems like it should.
(10) One size never fits all.
(11) Every old idea will be proposed again with a different name and
a different presentation, regardless of whether it works.
(11a) (corollary). See rule 6a.
(12) In protocol design, perfection has been reached not when there
is nothing left to add, but when there is nothing left to take
away.
Security Considerations
This RFC raises no security issues. However, security protocols are
subject to the fundamental networking truths.
References
The references have been deleted in order to protect the guilty and
avoid enriching the lawyers.
Author's Address
Ross Callon
Internet Order of Old Farts
c/o Bay Networks
3 Federal Street
Billerica, MA 01821
Phone: 508-436-3936
EMail: rcallon@baynetworks.com
AI ELI5
On this page
§1The Fundamental Truths
RFC 1925 is an April 1st memo that documents the Twelve Networking Truths. The first truth is simply "It Has To Work," the fundamental requirement. The second truth invokes a physical law: no amount of effort can increase the speed of light, and therefore communication latency is a hard constraint. It includes a corollary that you cannot make a baby faster than nine months, acknowledging that some constraints of human nature cannot be overcome by additional effort.
The first truth is that the network must work. The second is that light only travels so fast, so you can never send a message faster than the laws of physics allow.
§2Complexity, Trade-offs and Indirection
Subsequent truths address design reality. Truth 3 notes that with enough thrust, pigs can fly (a playful metaphor for doing unlikely things), but this does not mean it is a good idea. Truth 5 states that multiple problems can always be combined into a single interdependent solution, but this is usually a mistake. Truth 6 says it is easier to move a problem around in the architecture than to solve it, with a corollary that you can always add another layer of indirection. Truth 7 notes that something always goes wrong, and good, fast, and cheap are only achievable two at a time. Truth 8 asserts that everything is more complicated than expected.
Some truths say you can always make things more complicated, or move problems instead of solving them. Another says everything takes longer than you think and costs more than you budget.
§3Resources, Universality and Perfection
Truth 9 declares that whatever the resource, you always need more. Truth 10 states that one design never fits all cases. Truth 11 warns that old ideas come back with new names regardless of whether they work. Truth 12, the final and most design-focused truth, says that in protocol design, perfection is reached not when there is nothing left to add, but when there is nothing left to take away. This truth champions simplicity and elegance in design.
You always need bigger and better computers. Nothing works for everyone. Old bad ideas keep being proposed with new names. And the best designs are as simple as possible.