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PACK1.BEG
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1985-06-15
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THE ORIGINS OF PACKET RADIO
.
.
T
he widely-accepted AX.25 packet protocols were ingeniously
adapted by the Tucson AmRecommendation X.25, the internationally-accepted standa
rd and pack-
the Rand Corporation, a government-funded "think National
Physical Laboratory (NPL) proposed that a store-ated and received short communic
ation, but it led to the same kind of network design that
ters where ARPA-funded projects were in progress. (ARPA is is the
Advanced Research Projects Agency of the U.S. Department of De-
fense.)
.
In Europe, parallel work by many organizations led to the real-
ization that standards had to be derived for international opera-
tions using packet transmission and switching. Packet networks had
already begun operation in the U.S. (Telenet), England, Canada
(Infoswitch), Switzerland (Bernet), and Germany.
.
The CCITT, (French acronym for "International Consultative Com-
mittee on Telephone and Telegraph"), an agency of the ITU (Interna-
tional Telecommunications Union), charged with development of recom-
mendations and standards, tasked Study Group VII on Data Transmis-
sion, to draft a series of recommendations that would insure the
uniform development of packet transmission and switching protocols
and methods. In 1976, the Plenary Session of the ITU unanimously
approved CCITT Recommendation X.25, titled "Interface Between Data
Terminal Equipment (DTE) and Data Circuit Terminating Equipment
(DCE) for Terminals Operating in the Packet Mode on Public Data Net-
works". Recommendation X.25 stated that "the establishment in var-
ious countries of public data networks providing packet-switched
data transmission services creates a need to produce standards to
facilitate international interworking".
.
Recommendation X.25 was amended and expanded in 1980, and pre-
sently contains 99 single-spaced pages of detailed specifications.
X.25 makes references to a series of other Recommendations, includ-
ing X.1, X.2, X.21, X.21 bis, X.92, X.96 and a variety of other re-
lated standards. This Recommendation has been accepted by nations
signatory to the ITU treaties and conventions,
and has been adopted
by the Bell Operating Companies (as Bell Standard BX.25).
.
The impact and importance of X.25 can be best understood when
you consider that the American Bell companies have rarely adopted an
international standard for use within the Bell System.
.
Without delving further into the history of X.25, we can sum-
marize the topic by recognizing the brilliance with which the Tucson
Amateur Packet Radio Corporation designers modified, adapted and
executed the present standard for the Amateur Radio fraternity -
AX.25.
.
Amateur Radio standard AX.25 generally follows the provisions
of Recommendation X.25, complies with link access procedures and and
almost all other protocols and methods. The area in which AX.25
departs significantly from CCITT Recommendation X.25 is in the con-
cept of addressing of the destination station and the originating
station. X.25 supports and complies with a standardized commercial
numbering system suitable for the international common carrier net-
works.
.
AX.25 has a modified addressing scheme which permits the orig-
inating station to direct his packets to a destination station and
up to eight (8) digipeaters (digital packet repeaters), thus provid-
ing an integrated, rational method of establishing network routing,
as well as permitting automatic linked operation of individual pack-
et controllers as digipeaters.