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==Phrack Inc.==
Volume Two, Issue 18, Phile #9 of 11
The Tribunal of Knowledge presents..
A Few Things About Networks
===========================
Brought to you by Prime Suspect (TOK)
June 1, 1988
Seems like if you're into hacking you sometime or another run into using
networks, whether it be Telenet, Tymnet, or one of the Wide Area Networks.
One popular Network that hackers have used for some time is Arpanet. Arpanet
has been around for quite a long time. There are changes made to it almost
daily and the uses of it are much more than just logging into other systems.
Many college students find themselves getting acquainted with Bitnet these
days. Bitnet is SO new compared to other networks that it's got a lot of
potential left. There is much more to it then just mail and file transfers.
There are interactive uses such as the RELAY for real-time discussion with
others (equivalent to a CB mode) and another popular use is the network
information center to receive technical files about networking. There are
many many mail addresses that are used for database searching, and subscribing
to electronic magazines. You will find these same uses on other Wide Area
Networks also. I will give you 3 related network areas. These three areas
include: The AT&T company networks, UUCP, and Usenet cooperative networks.
Please note that some of the information I gathered for this file dated back
to 1986. But I tried to keep it as current as possible.
AT&T (Company Network)
----------------------
AT&T has some internal networks, most of which use internally developed
transport mechanisms. Their most widely used networks are UUCP and USENET,
which are not limited to that corporation and which are discussed later. All
internal AT&T networks support UUCP-style h1!h2!h!u source routing syntax and
thus appear to the user to be UUCP. Within AT&T, UUCP links are typically
over 1,200-bps dial-up telephone lines or Datakit (see below).
Among AT&T's other networks, CORNET is an internal analog phone network
used by UUCP and modems as an alternative to Direct Distance Dialing (DDD).
Datakit is a circuit-switched digital net and is similar to X.25 in some
ways. Most of Bell Laboratories is trunked together on Datakit. On top of DK
transport service, people run UUCP for mail and dkcu for remote login. In
addition to host-to-host connections. Datakit supports RS232 connections for
terminals, printers, and hosts. ISN is the version of Datakit supported by
AT&T Information Systems. Bell Laboratories in Holmdel, New Jersey, uses ISN
for internal data communication. BLICN (Bell Labs Interlocation Computing
Network) is an IBM mainframe RJE network dating from the early 1970s when
Programmer's Workbench (PWB) was a common version of the UNIX operating
system. Many UNIX machines with PWB-style RJE links use BLICN to queue mail
and netnews for other UNIX machines. A major USENET host uses this mechanism
to feed news to about 80 neighbor hosts. BLICN covers Bell Laboratories
installations in New Jersey, Columbus, Ohio, and Chicago, and links most
computer center machines. BLN (Bell Labs Network) is an NSC Hyperchannel at
Indian Hill, Chicago.
AT&T Internet is a TCP/IP internet. It is not a major AT&T network, though
some of the best-known machines are on it. There are many ethernets connected
by TCP/IP over Datakit. This internet may soon be connected to the ARPA
Internet.
ACCUNET is AT&T's commercial X.25 network. AT&T MAIL is a commercial
service that is heavily used within AT&T Information Systems for corporate
internal mail.
UUCP (Cooperative Network)
--------------------------
The name "UUCP," for Unix to Unix CoPy, originally applied to a transport
service used over dial-ups between adjacent systems. File transfer and remote
command execution were the original intent and main use of UUCP. There was an
assumption that any pair of communicating machines had direct dial-up links,
that is, that no relaying was done through intermediate machines. By the end
of 1978, there were 82 hosts within Bell Laboratories connected by UUCP.
Though remote command execution and file transfer were heavily used, there is
no mention of mail in the standard reference. There was another similar
network of "operational" hosts with UUCP links that were apparently outside
Bell Laboratories, but still within the Bell System. The two networks
intersected at one Bell Laboratory machine.
Both of these early networks differed from the current UUCP network in
assuming direct connections between communicating hosts and in not having
mail service. The UUCP mail network proper developed from the early networks
and spread as the UUCP programs were distributed as part of the Unix system.
Remote command execution can be made to work over successive links by
arranging for each job in the chain to submit the next one. There are several
programs that do this: Unfortunately, they are all incompatible. There is no
facility at the transport level for routing beyond adjacent systems or for
error acknowledgement. All routing and end-to-end reliability support is done
explicitly by application protocols implemented using the remote command
execution facility. There has never been any remote login facility associated
with UUCP, though the cu and tip programs are sometimes used over the same
telephone links.
The UUCP mail network connects a very diverse set of machines and users.
Most of the host machines run the UNIX operating system. Mail is the only
service provided throughout the network. In addition to the usual uses of
mail, much traffic is generated as responses to USENET news. The same
underlying UUCP transport mechanisms are also used to support much
of USENET.
The UUCP mail network has many problems with routing (it is one of the few
major networks that uses source routing) and with its scale. Nonetheless, it
is extremely popular and still growing rapidly. This is attributable to three
circumstances: ease of connection, low cost, and its close relationship with
the USENET news network.
Mailing lists similar to those long current on the ARPANET have recently
increased in popularity on the UUCP mail network. These permit a feature that
USENET newsgroups cannot readily supply: a limitation on access on a
per-person basis. Also, for low-traffic discussions mailing lists are more
economical, since traffic can be directed to individuals according to their
specific interests.
There is no central administration. To connect to the network, one need
only find one machine that will agree to be a neighbor. For people at other
hosts to be able to find your host, however, it is good to be registered in
the UUCP map, which is kept by the group of volunteers known as the UUCP
Project. The map is posted monthly in the USENET newsgroup "comp.mail.maps".
There is a directory of personal addresses on the UUCP network, although this
is a commercial venture unrelated to the UUCP Project.
Each host pays for it's own links; some hosts encourage others to connect
to them in order to shorten mail delivery paths.
There is no clear distinction between transport and network layers in UUCP,
and there is nothing resembling an Internet Protocol. The details of the
transport protocol are undocumented (apparently not actually proprietary to
AT&T, contrary to rumor, though the source code that implements the protocol
and is distributed with UNIX is AT&T's trade secret).
Mail is transferred by submitting a mail command over a direct connection
by the UUCP remote command execution mechanism. The arguments of the mail
command indicate whether the mail is to be delivered locally on that system
or resubmitted to another system. In the early days, it was necessary to
guess the route to a given host and hope. The only method of acknowledgment
was to ask the addressee to reply. Now there is a program (pathalias) that
can compute reasonable routes from the UUCP map, and there is software that
can automatically look up those routes for users.
The UUCP mail network is currently supported in North America mostly by
dial-up telephone links. In Europe there is a closely associated network
called EUnet, and in Japan there is JUNET.
The most common dial-up link speed on the UUCP mail network is 1,200 bps
though there are still a few 300-bps links, and 2,400 bps is becoming
more popular. Actually, now I believe that 1200-bps is still very common,
but 2400 may be just as common, and 9600-bps is much more common than ever
thought it would be in 1986. There are also many sites that use 19,200-bps
for using UUCP. When systems are very close, they are sometimes linked by
dedicated lines, often running at 9,600 bps. Some UUCP links are run over
local-area networks such as ethernets, sometimes on top of TCP/IP (though more
appropriate protocols than UUCP are usually used over such transport media,
when UUCP is used it's usual point-to-point error correction code is bypassed
to take advantage of the reliability of the underlying network and to improve
bandwidth). Some such links even exist on long-haul packet networks.
The widespread use of more sophisticated mail relay programs (such as
sendmail and MMDF) has increased reliability. Still, there are many hosts
with none of these new facilities, and the sheer size of the network makes
it unwieldly.
The UUCP mail network has traditionally used source code routing with a
syntax like hosta!hostb!hostc!host!user. The UUCP map and pathalias have made
this bearable, but it is still a nuisance. An effort is underway to alleviate
the routing problems by implementing naming in the style of ARPA Internet
domains. This might also allow integration of the UUCP name space into
the ARPA Internet domain name space. In fact there is now an ATT.COM domain
in which most hosts are only on UUCP or CSNET. Most UUCP hosts are not yet in
any Internet domain, however. This domain effort is also handled by the UUCP
Project and appears to be proceeding at a methodical but persistent pace.
The hardware used in the UUCP mail network ranges from small personal
computers through workstations to minicomputers, mainframes and super-
computers. The network extends throughout most of North America and parts of
Asia (Korea and Israel). Including hosts on the related networks JUNET (in
Japan) and EUnet (in Europe), there are at least 7,000 hosts on the network;
possibly 10,000 or more. (EUnet and JUNET hosts are listed in the UUCP maps.)
The UUCP Project addresses are:
uucp-query@cbatt.ATT.COM
cbatt!uucp-query
uucp-query@cbatt.UUCP
Much information about UUCP is published in USENET newsgroups.
USENET (Cooperative Network)
----------------------------
USENET began in 1980 as a medium of communication between users of two
machines, one at the University of North Carolina, the other at Duke
University. It has since grown exponentially to its current size of more than
2000 machines. In the process, the software has been rewritten several times,
and the transport mechanisms now used to support it include not only the
original UUCP links, but also X.25, ACSNET, and others.
USENET combines the idea of mailing lists as long used on the ARPANET with
bulletin-board service such as has existed for many years on TOPS-20 and other
systems, adding a freedom of subject matter that could never exist on the
ARPANET, and reaching a more varied constituency. While chaotic and inane
ramblings abound, the network is quite popular.
The USENET news network is a distributed computer conferencing system
bearing some similarities to commercial conferencing systems like CompuServe,
though USENET is much more distributed. Users pursue both technical and
social ends on USENET. Exchanges are submitted to newsgroups on various
topics, ranging from gardening to astronomy.
The name "USENET" comes from the USENIX Association. The Professional and
Technical UNIX User's Group. The name UNIX is a pun on Multics, which is the
name of a major predecessor operating system. (The pun indicates that, in
areas where Multics tries to do many things, UNIX tries to do one thing well.)
USENET has no central administration, though there are newsgroups to which
introductory and other information about the network is posted monthly.
USENET is currently defined as the set of hosts receiving the newsgroup
news.announce. There are about a dozen hosts that constitute the backbone of
the network, keeping transit times low by doing frequent transfers among
themselves and with other hosts that they feed. Since these hosts bear much
of the burden of the network, their administrators tend to take a strong
interest in the state of the network. Most newsgroups can be posted to by
anyone on the network. For others, it is necessary to mail a submission to a
moderator, who decides whether to post it. Most moderators just filter out
redundant articles, though some make decisions on other grounds. These
newsgroup moderators form another group interested in the state of the
network. Newsgroups are created or deleted according to the decisions made
after the discussion in the newsgroup "news.groups".
Each host pays its own telephone bills. The backbone hosts have higher
bills than most other hosts due to their long-distance links among themselves.
The unit of communication is the news article. Each article is sent by a
flooding routing algorithm to all nodes on the network. The transport layer
is UUCP for most links, although many others are used, including ethernets,
berknets, and long-haul packet-switched networks; sometimes UUCP is run on top
of the others, and sometimes UUCP is not used at all.
The many problems with USENET (e.g. reader overload, old software, slow
propagation speed, and high and unevenly carried costs of transmission) have
raised the possibility of using the experience gained in USENET to design a
new network to replace it. The new network might also involve at least a
partial replacement for the UUCP mail network.
One unusual mechanism that has been proposed to support the new network is
stargate. Commercial television broadcasting techniques leave unused
bandwidth in the vertical blanking interval between picture frames. Some
broadcasters are currently using this part of the signal to transmit Teletext
services. Since many cable-television channels are distributed via
geo-synchronous satellites, a single input to a satellite uplink facility can
reach all of North America on an appropriate satellite and channel. A
satellite uplink company interested in allowing USENET-like articles to be
broadcast by satellite on a well-known cable-television channel has been
found. Prototypes of hardware and software to encode the articles and other
hardware to decode them from a cable-television signal have been built and
tested in the field for more than a year. A new, reasonably price model of
the decoding box may be available soon.
This facility would allow most compatible systems within the footprint
(area of coverage) of the satellite and with access to the appropriate cable-
television channel to obtain decoding equipment and hook into the network at a
very reasonable cost. Articles would be submitted for transmission by UUCP
links to the satellite uplink facility. Most of the technical problems of
Stargate seem to have been solved.
More than 90 percent of all USENET articles reach 90 percent of all hosts
on the network within three days. Though there have been some famous bugs
that caused loss of articles, that particular problem has become rare.
Every USENET host has a name. That host name and the name of the poster
are used to identify the source of an article. Though those hosts that are on
both the UUCP mail and USENET news networks usually have the same name on both
networks, mail addresses have no meaning on USENET: Mail related to USENET
articles is usually sent via UUCP mail; it cannot be sent over USENET, by
definition. Though the two networks have always been closely related, there
are many more hosts on UUCP than on USENET. In Australia the two networks do
not even intersect except at one host.
There are different distributions of newsgroups on USENET. Some go
everywhere, whereas others are limited to a particular continent, nation,
state or province, city, organization, or even machine, though the more local
distributions are not really part of USENET proper. The European network
EUnet carries some USENET newsgroups and has another set of it's own. JUNET
in Japan is similar to EUnet in this regard.
There are about 2000 USENET hosts in the United States, Canada, Australia,
and probably in other countries. The hosts on EUnet, SDN, and JUNET
communicate with USENET hosts: The total number of news hosts including ones
on those three networks is probably at least 2500. The UUCP map includes
USENET map information as annotations. A list of legitimate netwide
newsgroups is posted to several newsgroups monthly. Volunteers keep
statistics on the use of the various newsgroups (all 250 of them) and on
frequency of posting by persons and hosts. These are posted to news.newslists
once a month, as is the list of newsgroups. Important announcements are
posted to moderated newsgroups, news.announce and news.announce.newusers,
which are intended to reach all users (the current moderator is Mark Horton,
cbosgd!mark). An address for information on the network is
seismo!usenet-request.
News on UUNET - June 1988
-------------------------
A year ago, UUNET (Fairfax, VA) was formed to help ease the communication
load of the beleaguered Usenet network of UNIX users. Usenet connections
were becoming increasingly costly and difficult to maintain, a situation that
prompted the Usenix Association to fund the creation of the UUNET
Communications Service to assist users in accessing Usenet. Now, UUNET has
become the "best connected" UNIX computer in the world, and has been
authorized to function as an Arpanet mail gateway. Gateways to other networks
are expected to be established in the future.
I guess all use of UUNET is done through the UUCP program found on Unix
operating systems. Many people are getting PC versions of the Unix Operating
system now-a-days, so knowing what's available before getting hooked into
a network, if that's your plan, is advised. There is an advertisement about
UUNET on Bix in the networks conference somewhere. The message may be old,
but still useful.
The cost of using UUNET is: $30/month... and $2/hour. I think the hourly
charge may only apply if connecting through Tymnet. Not sure.
Accessible via Tymnet, their 800 number, or a regular local POTS number.
Connections can definitely be made up to 9600 baud. 19.2K baud access may
also exist. I think it does.
If you're a UUNET user, and want to receive mail from someone through the
UUCP network, they would address it just as any other UUCP mail address.
An example is: ...uunet!warble!joeuser
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