On Tuesday 22 June 2004 01:40 am, it clown wrote:
Hi
I have added the AT commands to enable compression for my modem in wvdial.conf. I have also added bsdcomp 9,9 and deflate 15,15 to the ppp options file. After i connect to isp i run pppstats -z all its values are zero i do not see any compression. How do i know if compression is enabled?
I think you should just leave it up to the modem. Whatever compression occurs would have to be done on both sides of a connection and the modems usually take care of that with MNPx or V42BIS protocols. Best to check what CHAT says when a connection is made. I would suspect you're getting V42BIS. V.42bis standard A description of the V.42bis standard is given in "The V.42bis standard for data-compressing modems," by Clark Thomborson , IEEE Micro, Oct 1992, pp. 41-53. Short introduction, by Alejo Hausner : The V.42bis Compression Standard was proposed by the International Consultative Committee on Telephony and Telegraphy (CCITT) as an addition to the v.42 error-correction protocol for modems. Its purpose is to increase data throughput, and uses a variant of the Lempel-Ziv-Welch (LZW) compression method. It is meant to be implemented in the modem hardware, but can also be built into the software that interfaces to an ordinary non-compressing modem. V.42bis can send data compressed or not, depending on the data. There are some types of data that cannot be compressed. For example, if a file was compressed first, and then sent through a V.42bis modem, the modem would not likely reduce the number of bits sent. Indeed it is likely that the amount of data would increase somewhat. To avoid this problem, the algorithm constantly monitors the compressibility of the data, and if it finds fewer bits would be necessary to send it uncompressed, it switches to transparent mode. The sender informs the receiver of this transition through a reserved code word. Henceforth the data is passed as plain bytes.
Regards
On Fri, 18 Jun 2004 18:32:13 -0500
Patrick Shanahan
wrote: * it clown
[06-18-04 15:38]: Just wondering how do you turn on compression when
using wvdial? Is it
done auto? I see you can enable ppp deflate and bsd
compression in the
kernel. Or do you have to do it with a init string?
wvdial does not do compression. It dials a modem and starts PPP in order to connect to the Internet. -- Patrick Shanahan Registered Linux User #207535 http://wahoo.no-ip.org @ http://counter.li.org HOG # US1244711 Photo Album: http://wahoo.no-ip.org/photos
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