OpenBCM V1.08-4-g0592 (Linux)

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I0OJJ  > BPQ      16.02.25 05:59l 58 Lines 2313 Bytes #21 (0) @ WW
BID : F2ZI0OJJ_006
Read: JH4XSY GUEST
Subj: L4 (NETROM) Compression
Path: JH4XSY<IW0QNL<IZ3LSV<DB0ERF<DK0WUE<DK0WUE<VK5RSV<PI8ZTM<I0OJJ
Sent: 250215/2056z @:I0OJJ.ITA.EU [Rome] obcm1.08-6-g5b69
From: I0OJJ @ I0OJJ.ITA.EU (Gustavo)
To:   BPQ @ WW
X-Info: Sent with login password


Hi all,
just to inform you about a new feature added today to linBPQ (.62).
Enjoy!

TNX to John Wiseman, G8BPQ!

--
73 and ciao, gustavo i0ojj/ir0aab/ir0eq
non multa, sed multum

------------
Sat 15 Feb 2025 09:31:42 PM CET     L4 (NETROM) Compression

I've added an option to compress NETROM (L4) frames. As large blocks of
data compress better than small ones it takes all data queued to be sent
on a connection and compresses them using Deflate. The compressed data is
then split up into packets (default size 236) to be sent over the link.
Once all the compressed packets have been received the data is expanded
and passed to the session partner. There is a trade off between
compression efficiency and latency - the receiving end has to receive the
whole compressed message before it can be expanded and sent on. So the
code limits the number of compressed packets (default is 3) that can be
sent. If the compressed data exceeds this limit the input data is split
and re-compressed in chunks. Both the send packet size and limit on
frames is configurable. Compression is only used if both ends of the
connection have compression enabled.

Configuration.

L4Compress=1 turns on compression. default is off. L4CompMaxframe=n
limits number of frames of compressed data to send. Default 3.
L4CompPaclen=n sets packet size of compressed frames. Default it 236.

Compatibility.

The code uses a spare bit in the NETROM Opcode to indicate compressed
frames and a spare bit in the BPQ NETROM Connect Request extensions to
request and confirm compression. This is backwards compatible with
earlier versions of BPQ. There is a possibility that these bits could be
handled differently in other node software so please check for problems
if communicating with other software.

Monitoring.

In BPQ monitor output compressed frames have a C on end of monitor
header, eg MB7NPW to G8BPQ-9 ttl 21 cct=09F2 C: At the end of each
session a line is written to syslog (Linux) or DebugView log (Windows)
giving compression stats. L4 Compression Stats G8BPQ-9 MB7NPW TX 171 133
22% RX 1157 1311 13%. Numbers are input then output so for receive the
bytes output is greater than the bytes input.

John Wiseman, G8BPQ
February 2025
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