There should be four ways to get two Linux machines connected via Linux/IrDA.
Please note this feature is still quite experimental! Dag Brattli wrote: "Just wanted you to know I have just added COMPRESSION support to IrLAP! As you may know, this is _not_ part of the IrDA(TM) standard, but Linux can now negotiate with its peer and check if it has the same compression capabilities). So obviously if you are talking to Win95, Palm III or whatever, you will _not_ get compression!!! This is something which is exclusive for Linux as far as I know! The IrDA(TM) standard says that devices should ignore unknown field in the negotiation header, so we are still "compatible" with IrDA(TM) (have just borrowed an unused header value).
If you want to try using the compression code (Linux <-> Linux) you will have to insert the irda_deflate module some time before you actually make the connection. I do it before irattach.
The compression standard I have added is the deflate format used by the zlib library which is described by RFCs (Request for Comments) 1950 to 1952 in the files ftp://ds.internic.net/rfc/rfc1950.txt (zlib format), rfc1951.txt (deflate format) and rfc1952.txt (gzip format).
The compression interface is similar to PPP, so you can add as many different compressors as you want. Currently there is only support for GZIP, but BSD compression will be added later. ... Have just tested GZIP compression at 4Mbps. It was a really bad idea! Compressing the frames takes so much time that the performance is actually worse than when not using compression at all. The conclusion is that compression should only be used for SIR speeds, ..."