

paths                 Technical Information                 paths




Routing data base for mail

/uussrr/lliibb/mmaaiill/ppaatthhss

File /uussrr/lliibb/mmaaiill/ppaatthhss holds the data base used by the COHERENT
mail system  to route mail.  Each  line gives routing information
to a host, and has the following format:


        host    route   [cost]


_h_o_s_t  names a  UUCP  host.  Because  ssmmaaiill  uses a  binary-search
algorithm when searching the data base for a given host name, the
lines in  ppaatthhss must  be sorted  into ascending order.   (See the
Lexicon entry for  bbsseeaarrcchh for details on binary searches.) ssmmaaiill
ignores case  when it searches ppaatthhss, so  you should convert each
host name to lower case before you sort ppaatthhss.

The _r_o_u_t_e  field details the route by which  mail can travel from
your system to _h_o_s_t.  Note that it includes a pprriinnttff-style format
string.

The optional  field _c_o_s_t is  used by the COHERENT  mail system to
decide whether  to queue outbound UUCP mail,  or to invoke uuuucciiccoo
to  deliver the  mail immediately.   If the _c_o_s_t  is at  or below
ssmmaaiill's  ``queueing  threshold'',  then  ssmmaaiill  will  attempt  to
deliver it immediately.   This speeds mail delivery between hosts
that enjoy  an inexpensive UUCP link, such  as a hard-wired line,
and batches mail that must  be sent over expensive media, such as
long-distance  telephone.  If  the  _c_o_s_t field  is absent,  ssmmaaiill
gives  this  host  a  cost  value  above  that  of  its  queueing
threshold.

***** Example *****

The following  gives a  sample ppaatthhss  file for a  COHERENT system
that its owner has named lleeppaannttoo.


friend  friend!%s       300
hubsys  hubsys!%s       95
lepanto %s      0
lepanto.ampr.org        %s      0
smart-host      hubsys!%s       95
widget  hubsys!widget!%s        95


As  this file  shows,  lleeppaannttoo is  linked to  systems hhuubbssyyss  and
ffrriieenndd.  The cost  of 95  associated with hhuubbssyyss  is low,  and is
appropriate to a low-cost link, such as a hard-wired link; On the
other hand, the cost of 300 associated with ffrriieenndd is high, which
indicates that the connection with ffrriieenndd is high-cost, such as a
long-distance telephone  connection.  If cost is  100 or greater,


COHERENT Lexicon                                           Page 1




paths                 Technical Information                 paths



mail will be queued for latter delivery.  A cost below 100 causes
ssmmaaiill to attempt immediate delivery.

In this  example, machine lleeppaannttoo  is registered in  the aammpprr.oorrgg
Amateur  Packet Radio  domain.   Note that  machine name  lleeppaannttoo
appears in  both conventional and  domain forms in  order to help
resolve addressing.

In order to avoid having to  maintain a huge data base, the owner
of  lleeppaannttoo   uses  hhuubbssyyss  as  a   _s_m_a_r_t  _h_o_s_t.  The  ssmmaarrtt-hhoosstt
designation in  the ppaatthhss data base signals  ssmmaaiill to forward any
mail that it doesn't know how to deliver onto site hhuubbssyyss.

Finally, lleeppaannttoo can use hhuubbssyyss  to pass mail on to wwiiddggeett. Thus,
when rrmmaaiill  receives mail for system wwiiddggeett,  it will transmit it
to hhuubbssyyss for  forwarding.  Note that hhuubbssyyss's administrator must
have given lleeppaannttoo permission to use  it as a mail relay, or this
would not work.

***** See Also *****

mmaaiill, tteecchhnniiccaall iinnffoorrmmaattiioonn



































COHERENT Lexicon                                           Page 2


