comp.os.linux.networking Google Group

Re: Keeping a VERY accurate time (within a millisecond)

jeandav...@verizon.net (Jean-David Beyer) — Mon, 08 Sep 2008 11:44:52 UT

I thought about this back when I was running sendmail open to the Internet
so people could send to me directly. I did get a lot of spam and I thought
it would help when getting in touch with other users of sendmail to have
accurate time so they could find things in their logs by knowing when they

Re: piping a data feed through a connectionless UDP driver

nos...@com.invalid (Maxwell Lol) — Mon, 08 Sep 2008 11:12:14 UT

Yes. I think netcat (nc) can do this, and I have used ttcp as well.
But do you realize that because UDP is unreliable, the OS may not even
TRANSMIT outgoing packets?
Also - the jitter may be unpredictable.

piping a data feed through a connectionless UDP driver

cml...@acedsl.com (Albretch Mueller) — Mon, 08 Sep 2008 10:23:29 UT

Hi,
~
I need to stream/convert bytes of data from a file or connection
oriented TC Protocol to connectionless UDP using Linux
~
I would like to be able to do something like going:
~
cat filename > /dev/udpdrvr
~
I was wondering if there exist such a utility in Linux?
~
Thanks
lbrtchx

Re: LAN IP addresses

boite-a-s...@plouf.fr.eu.org (Pascal Hambourg) — Mon, 08 Sep 2008 10:21:24 UT

Moe Trin a écrit :
Wasn't this true already with subnetting, even before CIDR ?
Hey, I interpret this paragraph this way too ! :-o
I quote it for completeness :
IP addresses are not permitted to have the value 0 or -1 for
any of the <Host-number>, <Network-number>, or <Subnet-
number> fields (except in the special cases listed above).

Re: Activating routing

theun...@rijnh.nl (Kees Theunissen) — Mon, 08 Sep 2008 09:22:09 UT

Use NAT (a.k.a. masquerading) on swift when forwarding packets to/from
slick. As slick uses the private IP number 192.168.1.4 you can't
simply forward slicks packets unmodified to the public internet.
Regards,
Kees.

Re: Activating routing

fdele...@mail.cpod.fr (Fabrice Delente) — Mon, 08 Sep 2008 05:05:02 UT

Yes, I did that too, but still can't access the internet from slick... Is
there anything else to configure (I have enable "Advanced route" in the
kernel options)?
Thanks.

Re: Keeping a VERY accurate time (within a millisecond)

ignoramus19...@nospam.19762.invalid (Ignoramus19762) — Mon, 08 Sep 2008 03:25:09 UT

Just to have accurate timestamps.
This is a big topic. I do not feel up to starting it. But suffice it
to say that response times improve greatly when nothing is swapped out
and there are more CPUs than the amount of stuff to compute.

Re: Help understanding nameservers

cr...@this-is-bogus.sbcglobal.net (CRC) — Mon, 08 Sep 2008 02:19:34 UT

Thanks for the input.

Re: Do I need a software firewall in addition to a NAT router/firewall?

cr...@this-is-bogus.sbcglobal.net (CRC) — Mon, 08 Sep 2008 02:16:42 UT

Thanks for the responses, folks.

Re: Detecting Zombies?

dbxxxx...@yahoo.com (DanB) — Mon, 08 Sep 2008 01:23:07 UT

Actually, I have done that. In fact, it is the only computer thing I have
done there. My career was computers from the mainframe days in 1968 to
a few years ago when I retired. Now I only work at different jobs that I
enjoy, and this one happens to have nothing to do with any type of system
admin or computers of any kind other than using one on occasion.

Experience Virtualization with VM-Knoppix

jamshed.ji...@gmail.com (Jamy-Virus) — Mon, 08 Sep 2008 01:15:57 UT

Hi to all,
This is my First post here, i have been working on linux for last 2
years, few days i was wondoring to play with virutalization so i came
accross a good brief over view
[link]
share your comments will improve the content of future posts.

Re: privoxy crash

nob...@cosgroves.us (Kevin the Drummer) — Sun, 07 Sep 2008 19:40:26 UT

Actually, I rotate my logs weekly and expire them monthly.
Thanks for the ideas!

Re: Keeping a VERY accurate time (within a millisecond)

jmm-list.axspa...@sohnen-moe.com (Jim Moe) — Sun, 07 Sep 2008 19:31:48 UT

What are your application requirements? Do you just need a highly
accurate time reference, or do you need the system to respond to
sub-millisecond events in sub-millisecond timeliness?
Linux is not a realtime system. Thread priorities can keep one thread
from responding to an event for 100s of milliseconds. Even acquiring a

Re: Activating routing

k...@not.available.tld (Clifford Kite) — Sun, 07 Sep 2008 18:59:40 UT

In addition to Moe's excellent advice be sure ip forwarding is enabled
on swift:
corncob:~# cat /proc/sys/net/ipv4/ip_forward
1
corncob:~#
That can be done at runtime in a script or with sysctl.

Re: Keeping a VERY accurate time (within a millisecond)

unruh-s...@physics.ubc.ca (Unruh) — Sun, 07 Sep 2008 17:48:19 UT

No, it is not. The delay comes about because of the traversal of the
operating system and the network card to finally getting the stuff out onto
the internet. Even the packet length on the network is greater than a usec.
You cannot get nanosecond precision, even with a GPS attached directly to
your system. And ntp does not do the best possible job of getting rid of