Re: Problem connecting to Linux from DECnet/OSI Digital UNIX 4.0E system

[Steve Whitehouse <steve@gw.chygwyn.com>]

> 
> >>>>> "Rob" == Rob Davies <robdavies@worldnet.att.net> writes:
> 
>  Rob> Hi all, Following on from my earlier post, here's another two
>  Rob> traces.
> 
> That one looks better, no repeated connect confirms because they are
> getting acked this time...
> 
>  Rob> A couple of things I noticed:
> 
>  Rob> - When using interface lo, it appears that the DECnet
>  Rob> short-format frames are being used, whereas the long-format is
>  Rob> used on Ethernet ?  I haven't done the hex decode to confirm
>  Rob> this, but the headers definitely appear shorter.
> 
> lo isn't an Ethernet type interface.  I looked at it for a bit as a
> way to test DECnet within a box and found it not really useable
> (that's why I use ethertap now).
> 

The lo interface is set to send short headers rather than the long ethernet
type simply because I'd no other device which I could test the short
header code on and I forgot to set it back to use long headers afterwards :-)

There is a switch in the struct dn_dev called use_long, or something similar
which needs to be set to one in order for it to use long headers. I didn't
really consider it a problem though, since the same information is available
in both long and short headers, and using short headers gives less overhead.

If anyone is bothered, I'll change it to use long headers, I don't really
mind which it uses.

btw, what do people think that DECnet over IP/GRE should use ? Short headers
would be my choice, since thay have less overhead, but long headers would
seem the more correct considering its a broadcast device. (Well that really
depends upon whether you are using the "virtual lan" multicast stuff, but 
I don't want to land up having two different settings). PPP uses long
headers, depsite the fact its point-to-point.

Perhaps its time for /proc/sys/net/decnet/conf/<dev>/short_headers ?

Steve.
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