Very Computer

by **Alex Georgi** » Wed, 25 Jun 1997 04:00:00

[ Note: This message crossposted to four newsgroups. ]

A short intro:
DLC is a low level ethernet protocol, much faster than TCP/IP because
it finds machines by hardware address, not IP address, therefor no
extra processing... of course it can not be routed to different
subnet. As far as I know it is used for two things - to allow PCs to
talk to IBM mainframes and for printing to HP printers with JetDirect
cards... makes printing MUCH FASTER. Sorry, not sure where you can
find more detailed info in DLC, but there should be an rfc out there
for it. WinNT supports printing through DLC, but WinNT sucks big
time when it comes to print accounting... I am not paying more than
$500 bucks for a special printer accounting server, when I can write
the thing myself... but only for a UNIX os. ;-) Honestly, I don't
even want to know how to program for NT... yet.

So, does anybody know if Linux has support for DLC and DLC printing?
If not, do you guys think it would be worth it to implement such
support? Note that the only thing that would change is the way the
print job gets to the printer, nothing with the spooling, i.e. lpd
can stay pretty much the same. It would be just expanding the
networking capabilities of Linux... (personal opinion).

Cheers!
--

Computer Science Major, Michigan Tech
Michigan Tech Student Chapter of ACM
Pace Labs Consultant

by **Rick Ell** » Wed, 25 Jun 1997 04:00:00

>A short intro:
>DLC is a low level ethernet protocol, much faster than TCP/IP because
>it finds machines by hardware address, not IP address, therefor no
>extra processing... of course it can not be routed to different
>subnet. As far as I know it is used for two things - to allow PCs to
>talk to IBM mainframes and for printing to HP printers with JetDirect
>cards... makes printing MUCH FASTER.

Sounds like are quoting Microsoft.

by **Russell Cok** » Wed, 25 Jun 1997 04:00:00

Quote:>DLC is a low level ethernet protocol, much faster than TCP/IP because
>it finds machines by hardware address, not IP address, therefor no
>extra processing... of course it can not be routed to different

I don't believe that it's possible to get much faster than TCP. I've seen data
transferred over half duplex Ethernet using TCP at 900K/s. Dave Miller has
achieved speeds greater than 1100K/s using SPARC machines and full-duplex
Ethernet. Using a different protocol can't be much faster than these speeds,
maybe 5% faster if you're lucky.
As you say with TCP/IP you can easily change network routing without any
problems wheras DLC doesn't give you an option.

But if you want to do this then you'd be better off doing it in a user-space
program with RAW sockets IMHO.

Russell Coker

by **Joe Bu** » Wed, 25 Jun 1997 04:00:00

>DLC is a low level ethernet protocol, much faster than TCP/IP because
>it finds machines by hardware address, not IP address, therefor no
>extra processing...

But that extra processing (to map the IP address to the Ethernet address)
takes place only once for the whole time the host and printer are on
the wire. This is not a speed difference.

Quote:>As far as I know it is used for two things - to allow PCs to
>talk to IBM mainframes and for printing to HP printers with JetDirect
>cards... makes printing MUCH FASTER.

I seriously doubt that there is a measurable difference in speed, since
the bottleneck is generally the printer's speed rather than the capacity
of the wire. Even if the capacity of the wire were the limit, at most
you'd have 1% or so difference (yes, DLC's approach doesn't need as much
overhead per packet, but this overhead is small with TCP/IP already except
in applications like telnet/rlogin where there are one-character packets).
So whoever told you MUCH FASTER is either ignorant or engaging in
deception. (Some marketing department, perhaps?).

Quote:>So, does anybody know if Linux has support for DLC and DLC printing?

I believe the answer is no.

Quote:>If not, do you guys think it would be worth it to implement such
>support?

I don't think it's worth it (it would be worthless in any organization big
enough to have more than one Ethernet), but if someone wanted to
contribute it I don't see why it couldn't go in, especially if it's a
module.
--
-- Joe Buck http://www.synopsys.com/pubs/research/people/jbuck.html

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Very Computer

DLC support for Linux???

DLC support for Linux???

DLC support for Linux???

DLC support for Linux???

DLC support for Linux???