bind 8.2.4: limiting used memory?

Michael Renzmann mrenzmann at web.de
Tue Aug 7 12:01:52 UTC 2001


Hi Brad.

Brad Knowles <brad.knowles at skynet.be> schrieb am 07.08.01:

> 	The thing is that saving a little time with certain DNS queries 
> is likely to mean absolutely nothing in the grand scheme of
things 
> with a device like this.  Assuming that it is used as some
sort of 
> SOHO firewall/router device, you're going to be pretty much 
> completely dominated by network latency, and saving a few 
> milliseconds by caching only the ten most common queries is
just not 
> going to buy you a whole lot.

That shurely is true. Another thing I did not mention by no
is that this "dns cache" should resolve another problem.
Currently, many customers have many clients in their network.
Each client has the ISP dns configured. Now the IP of the DNS
have to be changed. In order to avoid problems like this the
router should be the institution that answers to every dns
query. Therefor it has to forward the queries to the correct
DNS. If it caches the queries or not the main point. It is a
side effect. If the effect is nearly useless as you pointed
out, we could leave this feature away.

I have to admit that I'm completely new to the concepts of
dns, dns cache, dns forwarder and such things. Maybe the way
I choosed is the wrong, and there might be better solutions
for what I want to do. If someone could point me to something
better I would be happy. 

In fact DJB wrote a nice program that seems to do what I
want. But it seems to depend on his own daemontools, which I
don't want to introduce as well to the system besides the
dnscache program. But this is offtopic here.

Bottom line: the main goal to achieve is that reconfiguration
of dns ips or similar things can be reduced to
reconfiguration of the router (which can be done remote)
rather than reconfiguring every client. If caching could have
some effect on the speed this would be fine, then caching can
be used (as long as enough memory is available). If not, we
could leave it away without suffering anything.

> 	I've been thinking myself about taking something like the 
> CerfBoard or maybe the CerfCube (see
<http://www.intrinsyc.com/>) and 
> running a "pico" version of NetBSD on the device (which has
only 32MB 
> of flash RAM on-board, along with some serial ports, a
10Base-T 
> Ethernet port, and a header for a CompactFlash card), and then 
> hooking up one of the upcoming CompactFlash format 802.11b 
> WiFi-certified WLAN cards, and basically cooking up my own 
> firewall/router/bridge.

Intrinsync is currently testing a new version of the
CerfBoard which has a pcmcia port instead of the compact
flash port. This is the better solution for usage with
802.11b wlans as such cards for pcmcia are much cheaper than
those fitting the compact flash socket. Besides that I doubt
there will be a lack of drivers for the compact flash
versions of cards in the next months.

Bye, Mike

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