thad@cup.portal.com (Thad P Floryan) (01/14/90)
forrie@suntau.UUCP (Forrie Aldrich) in <33@suntau.UUCP> writes:
I am confused about names of computers... I have been told that you can
only have a maximum of 6 characters for a machine name...
Then, I saw a machine name called 'snorklewacker' (whatever!)... so I
am wondering just what the situation is here...
Could someone please explain the limitations, and the why's? I sure
would appreciate it. I have looked into books, etc... and nothing
specific...just generalizations.
The Usenet protocols were based on the (then) Arpanet protocols (now known as
the Internet (collectively, due to what connects onto it)).
One of the "workhorses" of the early Arpanet was the DEC PDP-10 (w/ variations
such as Tenex from BBN, and eventually the DEC-20); in fact, the Internet's
NIC (Network Information Center at SRI (nic.ddn.mil, IP 26.0.0.73) is still
a DEC-20. I've used PDP-10, Tenex, DEC-20, Foonly (all related) systems
since their inception (the PDP-10 back around 1965), and one interesting
aspect of it was that, for "efficiency", filenames were stored in a single
36-bit machine word allowing up to 6 characters in a filename. My conjecture
is THIS is the genesis of the 6-character machine name. ^^^^^^^^^^
The Usenet, as such, started circa 1980 (if memory serves), and was required
to be in conformance with Arpa protocols (e.g. email formats, and so forth,
based on what's known as RFC 822).
For whatever reason(s), all the early protocols permitted up to 6-char names,
and much extant uucp software still abides those restrictions. More
recently, HDB (aka BNU) (circa 1984) uucp software permits up to 8-character
names. I "believe" it's possible names can be longer (your "snorklewacker",
for instance :-) but they must be UNIQUE within the first 6 (or 8)
characters.
Since one never knows all the vagaries one's net postings will undergo, it's
best to use the lowest common denominator: names unique within the first 6
characters.
Thad Floryan [ thad@cup.portal.com (OR) ..!sun!portal!cup.portal.com!thad ]mjl@cs.rit.edu (01/15/90)
In article <25902@cup.portal.com> thad@cup.portal.com (Thad P Floryan) writes: >forrie@suntau.UUCP (Forrie Aldrich) in <33@suntau.UUCP> writes: > > I am confused about names of computers... I have been told that you can > only have a maximum of 6 characters for a machine name... > > Could someone please explain the limitations, and the why's? I sure > would appreciate it. I have looked into books, etc... and nothing > specific...just generalizations. > >The Usenet protocols were based on the (then) Arpanet protocols (now known as >the Internet (collectively, due to what connects onto it)). Not quite. The USENET message interchange format has some relationship to SMTP, and is now and Internet standard (I think), but has nothing to do with machine names. Nor is the 6 character limit the result of the use of DEC systems on the early Internet. Instead, it is a limitation in some versions of UUCP -- definitely a Unix artifact, and in no way connected with any Internet standard. Most UUCP systems use the destination site name to set up control files, which are then processed by uucico (a separate program) to do the file transfers. Uucico determines the destination by examining a fixed portion of the control file name -- on Unix systems based on the V7 version for the PDP-11 (such as BSD), this field was 7 characters long. However, one of the early commercial releases from AT&T (System III or and early rev of System V) used only 6 characters. To avoid chaos on the UUCP network, the convention was adopted that all sites are unique in the first 6 characters. This helps insure mail, etc., will get through arbitrary forwarding sites. Sites on the Internet proper, with no direct connection to UUCP, need not obey these conventions. And, indeed, "snorklewacker" or whatever may be unique in the first 6 characters, so the others are simply ignored (sort of like some C compilers' handling of external identifiers :-( ). There are some sites, such as uunet, that explicitly advertise the ability to handle longer site names, some of which may specify gatewaying to the Internet (or other network). Thus, I *think* the following will work to send mail to foo.baz.bar on the Internet: ...!uunet!foo.baz.bar!recipient Mike Lutz Mike Lutz Rochester Institute of Technology, Rochester NY UUCP: {rutgers,cornell}!rochester!rit!mjl INTERNET: mjlics@ultb.isc.rit.edu
david@ms.uky.edu (David Herron -- a slipped disk) (01/15/90)
In article <25902@cup.portal.com> thad@cup.portal.com (Thad P Floryan) writes: >forrie@suntau.UUCP (Forrie Aldrich) in <33@suntau.UUCP> writes: > I am confused about names of computers... I have been told that you can > only have a maximum of 6 characters for a machine name... ... I'm afraid that there's enough mis-information here that I must step in and correct what I can.. Generally, Thad, I enjoy reading your postings but this time you're a bit off the track. >... I've used PDP-10, Tenex, DEC-20, Foonly (all related) systems >since their inception (the PDP-10 back around 1965), and one interesting >aspect of it was that, for "efficiency", filenames were stored in a single >36-bit machine word allowing up to 6 characters in a filename. My conjecture >is THIS is the genesis of the 6-character machine name. ^^^^^^^^^^ Good thing you labeled this as conjecture.. I fail to see how a strangeness on a non-Unix OS could affect naming of machines in a network of what amounts to being Unix BBS's. I know TOPS-10 quite well (incidently, they fit 6 characters into 36 bits by using a restricted character set that fit into 6 bits/character. tricks like this are easy on the PDP-6/10/20 architecture since it allows for varying byte sizes) >The Usenet, as such, started circa 1980 (if memory serves), and was required >to be in conformance with Arpa protocols (e.g. email formats, and so forth, >based on what's known as RFC 822). Yes, 1980. But, RFC-822 wasn't written until a couple years later. Also the earlier versions of Usenet -- remember that we're on the B version of Usenet right now, earlier version was A -- used a very different header format. And again within the B version there was a number of changes in format over time. Earlier versions of B had (conscious?) incompatibilities with RFC-822, for instance Article-ID: instead of Message-ID:. The compatibility with RFC-822 came in around the time of B v2.11 and RFC-950. >For whatever reason(s), all the early protocols permitted up to 6-char names, >and much extant uucp software still abides those restrictions. More >recently, HDB (aka BNU) (circa 1984) uucp software permits up to 8-character >names. I "believe" it's possible names can be longer (your "snorklewacker", >for instance :-) but they must be UNIQUE within the first 6 (or 8) >characters. There's a couple places where a limit can come from: -- Usenet software & what it can put into the sys file, and Path: lines. I wouldn't be surprised if early versions of Usenet software had a limit on this name. I'd also be surprised if there were *still* a limit. There isn't any intrinsic limit since the format is "name!name!..." Note that the name for Usenet purposes is (can be) different from your UUCP or domain names. Especially since a Path: line looks so much like a UUCP route-address that people insist on believing that it contains useful information for routing e-mail. It is best if you use the same name everywhere... but the software doesn't require this. -- UUCP software has had a variety of limits on host names. Usually in the range of 6-8 characters. There's no really good reason for this other than early development was done on PDP-11's and the software from that era shows all sorts of strange limits supposedly to make the software *fit* in the first place. Funny, this 3b1 I'm on right now seems rather small (memory wise) -- especially when I think about porting X to it. -- Arpanet names. I don't believe there was ever a limit, except for what people were willing to type. In fact, there were numerous machine names which were rather long when I started in on the nets in '84 .. a whole bunch of 'em at CMU with names like cmu-cs-foo-baz.arpa Then the naming pattern for gateway machines is to name the connected networks and tack "gw" on the end. Like uky-sura-gw.uky.edu. There was some interaction between arpanet hosts and Usenet hosts in the early days of Usenet. In fact, my first lesson on the uselessness of Path: lines as e-mail addresses was while I was trying to use Path: lines to get UUCP routing information. I learned real quick that the machine named "vgr" wouldn't pass any UUCP mail through it, despite what it said in the Path: line.(vgr.arpa is now == vgr.brl.mil) -- <- David Herron; an MMDF guy <david@ms.uky.edu> <- ska: David le casse\*' {rutgers,uunet}!ukma!david, david@UKMA.BITNET <- <- New official address: attmail!sparsdev!dsh@attunix.att.com
ignatz@chinet.chi.il.us (Dave Ihnat) (01/16/90)
As has been commented earlier, the six-character limit is purely an artifact-- whether of short-sighted arbitrary design restrictions, or a laudable desire to make sure all software was downward compatible, I choose not to judge. But the upshot is that, while it should be only archaic software that enforces this limitation, many fairly recently-shipped versions of UUCP still have an arbitrary limitation. (Think of the thousands of Unix-PC machines!) The reason I'm posting, however, is to warn about the side effects of assuming truncation will produce acceptable transfers. In particular, if a site on which UUCP expects short names, and truncates, talks to a site which allows long names--especially HDB UUCP--there will be a mismatch. Assume you're site 'foobarber', and your software assumes 6-character names. You'll appear to the HDB site to be simply 'foobar'. Unfortunately, if they try to enter you in their permissions and Systems files as 'foobarber', they not only won't truncate, but they'll reject your calls identifying you with the shorter name unless you have them modify the Permissions file entries. Also, in some cases, I've seen versions of "short-name" UUCP reject the long names sent by HDB. Even though the software only expects 6-character names, it seemed to still compare on the longer incoming name's full length. In short, you may well be introducing some fragility if you rely on name-length truncation.