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Advanced
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1997-04-12
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FreeNews' Advanced Configuration
================================
PLEASE NOTE: The options in advanved configuration are exactly that. Advanced. DO NOT alter
them unless you know what you are doing, or you have been specifically advised
to do so.
(This file last updated Sun 08th September 1996 for FreeNews 1.03)
(version 1.10 does not add any Advanced parameters)
Advanced configuration options control internal parameters for FreeNews, and
once set, should generally left well alone. If you do make any changes, you
are strongly advised to make a backup copy of your "Config" file.
To change an option, you must load the file <FreeNews$Dir>.Data.Config into
an editor, and change the lines with the relevant tags.
Pipelining
----------
Pipelining is the process by which articles are fetched from an NNTP server
so that all components in the link (server, phone line and client) are kept
as busy as possible. If any component is idle waiting for others to complete
a task, the overall process of news fetching will become slower.
There are two advanced configuration options that control pipelining,
"pipeline_min" and "pipeline_max". Their use is determined by the narrative
below:
Once connected to the server, FreeNews will attempt to keep the line and
the server as busy as possible. To do this, it will request not just one
article, but as many as possible. Since the reply to such a request will keep
the phone line busy for a while, the process will be sped up.
"As many as possible" is defined as the number of requests that will fit into
an NNTP command buffer (512 bytes) up to a certain limit. The limit is there
so that any buffers on the server do not get overloaded. This limit is
"pipeline_max".
However, as article requests are of varying lengths, FreeNews does not know
in advance how many requests to send. FreeNews will attempt to add requests
to the 512 byte buffer until there are a total of pipline_max requests
pending (in the buffer or at ther server already). However, if the output
buffer becomes full, only the currently composed article requests will be
sent. In this way, FreeNews only sends a maximum of one buffer (hopefully,
one TCP/IP packet) at a time.
Each time the server completes sending a message to FreeNews, FreeNews
inspects the parameter "pipeline_min". If the current number of articles
which have pending requests is LESS than pipeline_min, FreeNews will request
some more (as above) until either a block is full, or pipeline_max is
reached.
The reason that these parameters may require changing is that if you have a
very fast line and/or a very lightly loaded server, the pipe could empty more
quickly.
It is important to note that pipeline_min must always be less than
pipeline_max, and that the difference between them is not too great to avoid
overflowing server buffers.
Defaults :-
pipeline_min: 15
pipeline_max: 22
Ignore_502
----------
With the release of FreeNews 1.00, some people observed that their server
sometimes returned the string "502 Permission Denied" to the request of a
message. This is only returned for occasional messages, and succeeding ones
would fetch correctly.
FreeNews 1.01 onwards will now ignore "502" responses (or rather, they are
treated in the same way as a "220 Article Retrieved" message.
However, this is an option because the NNTP standard, RFC977 states that
messages of the form 5xx are fatal errors. Thus, if you experience 502
responses, you should set this option to "Yes".
WARNING: FreeNews' behaviour is undefined should a 502 response occur at
other times during transfer.
Default :-
ignore_502: No
Check_rate
----------
To ensure that FreeNews' downloads are not slowed down by additional tasks
on the icon bar, 1.03+ of FreeNews supports the "check_rate" advanced option.
In 1.02 and before, FreeNews' behaviour was to be super-nice to any other
tasks on the machine by calling wimp_poll as often as possible, usually after
every line is received from the server ("check_rate: 1").
From version 1.03, FreeNews can be instructed to read and process "n" lines
per Wimp_Poll. Please note that setting this value too low will result in FreeNews
slowing down when other tasks are loaded. Setting it too high will result in
maximum throughput, but with great effect on the machine's ability to multitask.