On 6/27/22 12:27 PM, Harald Welte wrote:
Hi Grant,
Hi Harald,
Sure. I was just assuming that people who playing with legacy tech would also likely want to interface legacy hardware.
Fair enough. But "legacy hardware" can be a lot of things. As you say, it can be something with an X.21 interface. It can also be something with an RS-232 serial interface. The latter RS-232 serial interface can be had with contemporary equipment fairly easily; e.g. Raspberry Pi (et al.) with a TTL/RS-232 voltage level shifter and / or USB/RS-232 interface.
There's also for example the FarSite WAN boards that expose X.21. Those should also show up as hldcX netdev and hence be used with the X.25 code. But of course there are always many different use cases.
I suspect this would be in the realm of people that explicitly want an X.21 interface, probably because they have another piece of equipment that has a matching X.21 interface which they want to connect to.
good luck :)
Thank you.
My personal take is that with at least some of those incomplete old kernel implementations for ancient protocols it's often easier to simply rewrite what's needed in userspace (I did so with frame relay about two years ago).
I largely agree. Though I question how well a user space process can interface with specific hardware /without/ some sort of kernel involvement / blessing, even if it's only a stub driver to provide something minimal for the user space program to glom onto.
At the speed of modern computers, there's not really any advantage of running it in the kernel. And if the mainline code has some constraints or bugs you need to work around, you have to rebuild the kernel etc. - a lot of effort.
Fair enough.
The kernel FR for example imposes some arbitrary MTU limits (1500?) while the FR specs permit for larger message sizes, and non-IP users actually use those in the real world (3GPP Gb interface over FR).
1500 -- I presume -- bytes sounds like an Ethernet limitation applied to Frame Relay under the assumption that the FR is transporting Ethernet frames.
--
Grant. . . .
unix || die
