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