2.11BSD/new/man/cat1/pathalias.0
PATHALIAS(1) UNIX Programmer's Manual PATHALIAS(1)
NAME
pathalias, makedb, arpatxt - mail routing tools
SYNOPSIS
pathalias [ -ivcDf ] [ -t _l_i_n_k ] [ -l _h_o_s_t ] [ -a _h_o_s_t ] [
-d _l_i_n_k ] [ _f_i_l_e_s ... ]
makedb [ -a ] [ -o _d_b_m_f_i_l_e ] [ _f_i_l_e_s ... ]
arpatxt [ -@fi ] [ -g _g_a_t_e_w_a_y ] [ -p _p_r_i_v_a_t_e_f_i_l_e ] [
-d _d_i_r_e_c_t_o_r_y ] [ _f_i_l_e_s ... ]
DESCRIPTION
_P_a_t_h_a_l_i_a_s computes the shortest paths and corresponding
routes from one host (computer system) to all other known,
reachable hosts. _P_a_t_h_a_l_i_a_s reads host-to-host connectivity
information on standard input or in the named _f_i_l_e_s, and
writes a list of host-route pairs on the standard output.
Here are the _p_a_t_h_a_l_i_a_s 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 _h_o_s_t
Set local host name to _h_o_s_t. By default, _p_a_t_h_a_l_i_a_s
discovers the local host name in a system-dependent
way.
-a _h_o_s_t
Avoid _h_o_s_t; penalize all links out of _h_o_s_t by a small
amount. The -a option is cumulative.
-d _a_r_g
Declare a dead link, host, or network. If _a_r_g 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 _a_r_g 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 _a_r_g is a network name, the
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network requires a gateway.
-t _a_r_g
Trace input for link, host or network on the standard
error output. The form of _a_r_g is as above.
_M_a_k_e_d_b takes _p_a_t_h_a_l_i_a_s output and creates or appends to a
_d_b_m(3) database.
Here are the _m_a_k_e_d_b options:
-a Append to an existing database; by default, _m_a_k_e_d_b
truncates the database.
-o _d_b_m_f_i_l_e
Identify the output file base name.
_A_r_p_a_t_x_t converts the Internet hosts table _h_o_s_t_s._t_x_t into
_p_a_t_h_a_l_i_a_s input.
Here are the _a_r_p_a_t_x_t options:
-@ Generate _p_a_t_h_a_l_i_a_s input that specifies `@' style
addressing. The default is to produce _p_a_t_h_a_l_i_a_s input
that specifies `!' style addressing.
-f ``Filter mode'' - write output on stdout. Normally,
_a_r_p_a_t_x_t writes the description of each domain into a
separate file.
-i Map output to lower case.
-g _a_r_g
Declare a gateway to the Internet or one of its sub-
domains. If _a_r_g 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. Oth-
erwise, _a_r_g is declared a gateway to the Internet as a
whole.
-p _p_r_i_v_a_t_e_f_i_l_e
_P_r_i_v_a_t_e_f_i_l_e contains a list of host names that con-
flict with other names.
-d _d_i_r_e_c_t_o_r_y
Write output files in _d_i_r_e_c_t_o_r_y.
_P_a_t_h_a_l_i_a_s Input Format
A line beginning with white space continues the preceding
line. Anything following `#' on an input line is ignored.
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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 _l_i_n_k_s. A link
may be preceded or followed by a network character to use in
the route. Valid network characters 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
symbolic 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 infin-
ite), HIGH and LOW are -5 and +5 respectively, for baud-rate
or quality bonuses/penalties, and FAST is -80, for adjusting
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
used.
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,
%thrash(LOCAL)
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 brack-
ets, the link is considered _t_e_r_m_i_n_a_l, and further links
beyond this one are heavily penalized. _E._g., with input
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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 _a_l_i_a_s_e_s. 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 follows:
net = {host, host, ...}
The host-list may be preceded or followed by a routing char-
acter, and may be followed by a cost:
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 _g_a_t_e_w_a_y_s and _d_o_m_a_i_n_s .
Connection data may be given while hiding host names by
declaring
private {host, host, ...}
_P_a_t_h_a_l_i_a_s 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
declarations when reading from the standard input.
Dead hosts, links, or networks may be presented in the input
stream by declaring
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dead {arg, ...}
where _a_r_g has the same form as the argument to the -d
option.
Output Format
A list of host-route pairs is written to the standard out-
put, where route is a string appropriate for use with
_p_r_i_n_t_f(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 _d_o_m_a_i_n_s, 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.''
Gateways
A network is represented by a pseudo-host and a set of net-
work members. Links from the members to the network have
the weight given in the input, while the cost from the net-
work to the members is zero. If a network is declared dead,
the member-to-network links are marked dead, which effec-
tively 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 gate-
way. (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 gate-
way.
Domains
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.
_E._g.,
harvard .EDU # harvard is gateway to .EDU domain
.EDU = {.BERKELEY, .UMICH}
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.BERKELEY = {ernie}
yields
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, _p_a_t_h_a_l_i_a_s
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.
Databases
_M_a_k_e_d_b builds a _d_b_m(3) database from the standard input or
from the named _f_i_l_e_s. 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.
FILES ET AL.
/usr/local/lib/palias.{dir,pag} default dbm output
newsgroup comp.mail.maps likely location of some
input files
_g_e_t_o_p_t(3), available from comp.sources.unix archives (if not
in the C library).
BUGS
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.
_P_a_t_h_a_l_i_a_s can generate hybrid (_i._e. ambiguous) routes, which
are abhorrent and most certainly 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 _p_a_t_h_a_l_i_a_s resorts
to the ``magic %'' rule when necessary. This convention is
not documented anywhere, including here.
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The -D option elides insignificant routes to domain members.
This is benign, perhaps even beneficial, but confusing,
since the behavior is undocumented and somewhat unpredict-
able.
SEE ALSO
P. Honeyman and S.M. Bellovin, ``PATHALIAS _o_r The Care and
Feeding of Relative Addresses,'' in _P_r_o_c. _S_u_m_m_e_r _U_S_E_N_I_X
_C_o_n_f., Atlanta, 1986.
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