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PATHALIAS(1)									     PATHALIAS(1)

       pathalias, makedb, arpatxt - mail routing tools

       pathalias [ -ivcDf ] [ -t link ] [ -l host ] [ -a host ] [ -d link ] [ files ...  ]

       makedb [ -a ] [ -o dbmfile ] [ files ...  ]

       arpatxt [ -@fi ] [ -g gateway ] [ -p privatefile ] [ -d directory ] [ files ...	]

       Pathalias  computes  the  shortest  paths and corresponding routes from one host (computer
       system) to all other known, reachable hosts.  Pathalias	reads  host-to-host  connectivity
       information on standard input or in the named files, and writes a list of host-route pairs
       on the standard output.

       Here are the pathalias options:

       -i    Ignore case:  map all host names to lower case.  By default, case is significant.

       -c    Print costs: print the path cost before each host-route pair.

       -v    Verbose: report some statistics on the standard error output.

       -D    Terminal domains: domain members are terminal.

       -f    First hop cost: the printed cost is the cost to the first relay in a  path,  instead
	     of the cost of the path itself; implies (and overrides) the -c option.

       -l host
	     Set local host name to host.  By default, pathalias discovers the local host name in
	     a system-dependent way.

       -a host
	     Avoid host; penalize all links out of host by a small  amount.   The  -a  option  is

       -d arg
	     Declare a dead link, host, or network.  If arg is of the form ``host-1!host-2,'' the
	     link from host-1 to host-2 is treated as an extremely high cost (i.e.,  DEAD)  link.
	     If  arg  is  a single host name, that host is treated as dead and is used as a relay
	     host of last resort on any path.  If arg is a network name, the network  requires	a

       -t arg
	     Trace input for link, host or network on the standard error output.  The form of arg
	     is as above.

       Makedb takes pathalias output and creates or appends to a dbm(3) database.

       Here are the makedb options:

       -a    Append to an existing database; by default, makedb truncates the database.

       -o dbmfile
	     Identify the output file base name.

       Arpatxt converts the Internet hosts table hosts.txt into pathalias input.

       Here are the arpatxt options:

       -@    Generate pathalias input that specifies `@' style addressing.   The  default  is  to
	     produce pathalias input that specifies `!' style addressing.

       -f    ``Filter mode'' -- write output on stdout.  Normally, arpatxt writes the description
	     of each domain into a separate file.

       -i    Map output to lower case.

       -g arg
	     Declare a gateway to the Internet or one of its subdomains.  If arg contains one  or
	     more  dots, the left-hand side component that contains no dots is declared a gateway
	     to the domain to the right of the dot.  Otherwise, arg is declared a gateway to  the
	     Internet as a whole.

       -p privatefile
	     Privatefile contains a list of host names that conflict with other names.

       -d directory
	     Write output files in directory.

   Pathalias Input Format
       A line beginning with white space continues the preceding line.	Anything following `#' on
       an input line is ignored.

       A list of host-to-host connections consists of a ``from'' host in column  1,  followed  by
       white  space, followed by a comma-separated list of ``to' hosts, called links.  A link may
       be preceded or followed by a network character to use in the route.  Valid network charac-
       ters are `!' (default), `@', `:', and `%'.  A link (and network character, if present) may
       be followed by a ``cost'' enclosed in parentheses.   Costs  may	be  arbitrary  arithmetic
       expressions  involving  numbers,  parentheses, `+', `-', `*', and `/'.  The following sym-
       bolic costs are recognized:

	      LOCAL	  25   (local-area network connection)
	      DEDICATED   95   (high speed dedicated link)
	      DIRECT	 200   (toll-free call)
	      DEMAND	 300   (long-distance call)
	      HOURLY	 500   (hourly poll)
	      EVENING	1800   (time restricted call)
	      DAILY	5000   (daily poll, also called POLLED)
	      WEEKLY   30000   (irregular poll)

       In addition, DEAD is a very large number (effectively infinite), HIGH and LOW are  -5  and
       +5  respectively, for baud-rate or quality bonuses/penalties, and FAST is -80, for adjust-
       ing costs of links that use high-speed (9.6 Kbaud or more) modems.  These  symbolic  costs
       represent  an imperfect measure of bandwidth, monetary cost, and frequency of connections.
       For most mail traffic, it is important to minimize the number of hosts in a  route,  thus,
       e.g.,  HOURLY  *  24 is much larger than DAILY.	If no cost is given, a default of 4000 is

       For the most part, arithmetic expressions that mix symbolic  constants  other  than  HIGH,
       LOW,  and  FAST	make  no sense.  E.g., if a host calls a local neighbor whenever there is
       work, and additionally polls every evening, the cost is DIRECT, not DIRECT+EVENING.

       Some examples:

	      down	princeton!(DEDICATED), tilt,
	      princeton topaz!(DEMAND+LOW)
	      topaz	@rutgers(LOCAL+1)

       If a link is encountered more than once, the least-cost occurrence dictates the	cost  and
       network	character.   Links  are  treated  as  bidirectional but asymmetric: for each link
       declared in the input, a DEAD reverse link is assumed.

       If the ``to'' host in a link is surrounded by angle brackets, the link is considered  ter-
       minal, and further links beyond this one are heavily penalized.	E.g., with input

	      seismo	<research>(10), research(100), ihnp4(10)
	      research	allegra(10)
	      ihnp4	allegra(50)

       the path from seismo to research is direct, but the path from seismo to allegra uses ihnp4
       as a relay, not research.  The way to think of this is to imagine two copies of	research,
       one  that's cheap to get to, but has no neighbors, and one that's expensive to get to, but
       has neighbors.  (This is an exception to the ``least-cost link'' rule above.)

       The set of names by which a host is known to its neighbors is called its aliases.  Aliases
       are declared as follows:

	      name = alias, alias ...

       The  name  used	in the route to or through aliased hosts is the name by which the host is
       known to its predecessor in the route.

       Fully connected networks, such as the ARPANET or a local-area  network,	are  declared  as

	      net = {host, host, ...}

       The host-list may be preceded or followed by a routing character, and may be followed by a

	      princeton-ethernet = {down, up, princeton}!(LOCAL)
	      ARPA = @{sri-unix, mit-ai, su-score}(DEDICATED)

       The routing character used in a route to a network member  is  the  one	encountered  when
       ``entering'' the network.  See also the sections on gateways and domains .

       Connection data may be given while hiding host names by declaring

	      private {host, host, ...}

       Pathalias will not generate routes for private hosts, but may produce routes through them.
       The scope of a private declaration extends from the declaration to the end  of  the  input
       file  in  which it appears, or to a private declaration with an empty host list, whichever
       comes first.  The latter scope rule offers a way to retain the semantics of private decla-
       rations when reading from the standard input.

       Dead hosts, links, or networks may be presented in the input stream by declaring

	      dead {arg, ...}

       where arg has the same form as the argument to the -d option.

   Output Format
       A  list	of  host-route	pairs  is written to the standard output, where route is a string
       appropriate for use with printf(3), e.g.,

	      rutgers	princeton!topaz!%s@rutgers

       The ``%s'' in the route string should be replaced by the  user  name  at  the  destination
       host.  (This task is normally performed by a mailer.)

       Except  for  domains, the name of a network is never used in routes.  Thus, in the earlier
       example, the path from down to up would be ``up!%s,'' not ``princeton-ethernet!up!%s.''

       A network is represented by a pseudo-host and a set of network members.	 Links	from  the
       members to the network have the weight given in the input, while the cost from the network
       to the members is zero.	If a network is declared dead, the  member-to-network  links  are
       marked dead, which effectively prohibits access to the network from its members.

       However,  if the input also shows an explicit link from any host to the network, then that
       host can be used as a gateway.  (In particular, the gateway need not be a network member.)

       E.g., if CSNET is declared dead and the input contains

	      CSNET = {...}
	      csnet-relay	  CSNET

       then routes to CSNET hosts will use csnet-relay as a gateway.

       A network whose name begins with `.' is called a domain.  Domains are presumed to  require
       gateways,  i.e.,  they are DEAD.  The route given by a path through a domain is similar to
       that for a network, but here the domain name is tacked onto the	end  of  the  next  host.
       Subdomains are permitted.


	      harvard	.EDU	  # harvard is gateway to .EDU domain
	      .EDU	= {.BERKELEY, .UMICH}
	      .BERKELEY = {ernie}


	      ernie	...!harvard!ernie.BERKELEY.EDU!%s

       Output is given for the nearest gateway to a domain, e.g., the example above gives

	      .EDU	...!harvard!%s

       Output  is given for a subdomain if it has a different route than its parent domain, or if
       all its ancestor domains are private.

       If the -D option is given on the command line, pathalias treats a link from a domain to	a
       host  member  of  that  domain as terminal.  This discourages the use of routes that use a
       domain member as a relay.

       Makedb builds a dbm(3) database from the standard input or from the named files.  Input is
       expected  to be sequence of ASCII records, each consisting of a key field and a data field
       separated by a single tab.  If the tab is missing, the data field is assumed to be empty.

       /usr/local/lib/palias.{dir,pag}	   default dbm output
       newsgroup comp.mail.maps 	   likely location of some input files
       getopt(3), available from comp.sources.unix archives (if not in the C library).

       Terminal nets are not implemented.

       The -i option should be the default.

       The order of arguments is significant.  In particular, -i and -t should appear early.

       Pathalias can generate hybrid (i.e. ambiguous) routes, which are abhorrent and  most  cer-
       tainly  should  not be given as examples in the manual entry.  Experienced mappers largely
       shun `@' when preparing input; this is historical, but also reflects UUCP's facile  syntax
       for source routes.

       Multiple  `@'s  in routes are loathsome, so pathalias resorts to the ``magic %'' rule when
       necessary.  This convention is not documented anywhere, including here.

       The -D option elides insignificant routes to domain members.  This is benign, perhaps even
       beneficial, but confusing, since the behavior is undocumented and somewhat unpredictable.

       P.  Honeyman  and  S.M.	Bellovin,  ``PATHALIAS	or  The  Care  and  Feeding  of  Relative
       Addresses,'' in Proc. Summer USENIX Conf., Atlanta, 1986.

Public Domain				     10/4/87				     PATHALIAS(1)
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