Messages in this thread | | | Date | Fri, 16 May 2003 23:16:03 -0300 (EST) | From | Felipe Massia Pereira <> | Subject | mtu_expires variable |
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Hello,
I've been searching for the exact meaning of this variable through Documentation and I've found just empty descriptions (to be filled in, in Advanced Linux Routing HOWTO, and nothing also in Documentation/networking/ip-sysctl.txt). I've tried also to read the kernel source code (net/ipv4/route.c) but I could not figure out what they mean.
I've came accross this var because we want to do some experiments in class with Path MTU discovery. But it happens that MTU is recorded between experiments (and it's what we expect: that the stack does not do a PMTU every time). BTW where is the PMTU value kept? Is MTU value recorded for each destination or for each route?
So it would be nice if we could make the value found in a experiment to be forgotten by the kernel so the students could execute the ping several times. (ping -c 2 -m want ...) Is mtu_expires what we're looking for?
We tried to "echo 1 > /proc/sys/net/ipv4/route/mtu_expires" considering that it's expressed in seconds. The usual value is 600. But I've read that it's expressed in jiffies. Jiffies occur 100 times per sec on a PC, is it? So the value 600 on a PC means 6 seconds?
tia, -- Felipe
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