27 Feb
2009
27 Feb
'09
10:21 p.m.
Paul Koning wrote:
"Johnny" == Johnny Billquist <bqt at softjar.se> writes:
gerry> We still do not know how these UDP related problems would/will
gerry> impact other protocols like LAT, LAD/LAST and MOP because we
gerry> haven't experimented so much as with pure DECnet. Any
gerry> contribution and suggestions on how to force reduced frame
gerry> size for those protocols would be much appreciated. :-)
> I can't think of any. The general rule at
DEC was that some basic
> level of design competence was assumed. Getting the Ethernet
> frame size right was certainly part of the basic IQ test.
> >> The only solution I can think of is to reduce the MTU of your
> local Ethernet on the machine doing the UDP encapsulation. That
> would force the packets to be fragmented at origination time,
> which means your defective routers will see small-enough packets.
Johnny> If
I suspect right, that won't solve it. I haven't any
Johnny> direct experience with these kind of problems, but the few
Johnny> cases that I'm semi-aware of are actually of
Johnny> bridges/gateways/routers that can't handled IP
Johnny> fragments. Forcing a fragment even earlier won't help.
Oh. I thought the issue was that those "routers" couldn't do
fragmentation right.
It could be. As I said, I'm just "guessing".
If the problem is that they look at the header to see if it's
fragmented -- which is something they should not care about -- and
then proceed to get confused, then indeed they are beyond all hope and
the only solution is to scrap them and get real routers.
Well, the problem with policy based firewalls/routers is that they inspect more (in fact,
they have to) than the IP header. And some of them are too stupid to deal with fragments.
Johnny
--
Johnny Billquist || "I'm on a bus
|| on a psychedelic
trip
email: bqt at softjar.se || Reading murder books
pdp is alive! || tryin' to stay hip" -
B. Idol