Path: utzoo!utgpu!water!watmath!codas!mikel
From: mikel@codas.att.com (Mikel Manitius)
Newsgroups: news.software.b
Subject: Re: Two News feeds (howto: ihave/sendme)
Message-ID: <2024@codas.att.com>
Date: 12 Feb 88 06:37:37 GMT
References: <484@wa3wbu.UUCP>
Organization: AT&T, Altamonte Springs, FL
Lines: 69

In article <484@wa3wbu.UUCP> john@wa3wbu.UUCP (John Gayman) writes:
> 
>    I'm currently attempting to have two systems feed me News. Is this
> advisable and if so, how can I set up my "sys" file so that all the news
> I get from each site doesn't get forwarded to the other site ?  I put
> the "L" flag on the one feed but it looks like I never saw any of the
> News that came in last night. Any ideas ???

If it's advisable depends upon your resources.

You should keep in mind that although the news system will not send an
article to your neighbor if he has already seen it, it is possible, and
highly probable you and your neighbors will have a high duplicate rate.


			a ------ b -- x
			 \      /
			  \    /
			   \  /
			    c

If (b) posts something, he will send it to (a, c, x), (a) will send
to (c). If (c) gets it from (b) first, it will send to (a).

However if (x) posts, it will send to (b), who will send to (a, c)
which will in turn feed each other, causing dups.

Duplicates can be avoided using ihave/sendme. In ihave/sendme each
site will first send the other a list the article IDs of what it has.
The receiving site will then request what it doesn't have.

This is good, however it causes time delay between reception of
messages, and duplicates may still occur, because (c) may receive
an article from (b) after it already requested it from (a).

An ihave/sendme sys entry, using batching looks like this:

foovax:[newsgroups]:FI:

With a sendbatch cron entry of:

sendbatch -i -c foovax

It also requires "to.foovax" to exist with the proper distribution.

Another possibility is for (c) to send only articles to (a) that have
not been to (b). This can signifigantly reduce duplicates in a small
network, but the topology of USENET is too large for a site such as
for example "codas" which has many feeds, to set this up effectivley.

A sys line for (c), not to send things to (a) that have been through
through (b) could be:

a/b:[newsgroups]:F:

The "a" is the site you're feeding, everything after the slash, up
to the colon is a list of sites that should not have seen the message
if it is to be sent. This could be "a/b,x:", to include (b) and (x).

Finally, the "L" type in the third field. A simple "L" sais to feed
only things that were posted locally. An "Ln" where "n" is a number
between 1 and 9, sais to feed only things that were posted at a maximum
of "n" hops away. It doesn't approach the above issues.

Other possibilities exist, the above are most appropriate for what
you are trying to do.
-- 
					Mikel Manitius @ AT&T
					mikel@codas.att.com