The story so far...

Under linux with roaring penguin PPPoE software
( http://www.roaringpenguin.com/pppoe/ ), the 3Com dual link
adsl modem likes to disconnect itself if it doesn't get any traffic
for 15 seconds. There have been two solutions put forward for this:

- Ping something every 14 seconds or so, e.g.
        ping -i 14 -q xxx.xxx.xxx.xxx > /dev/null &

- Send LCP echo requests every 14 seconds or so. From /etc/ppp/pppoe.conf:
        # LCP echo interval and failure count.
        LCP_INTERVAL=14
        LCP_FAILURE=3
        # PPPOE_TIMEOUT should be about 4*LCP_INTERVAL
        PPPOE_TIMEOUT=80

Both of these seem to work fine under moderate usage. Pinging has
the disadvantage of annoying the server operators (maybe) and generating
traffic (bad for those with traffic limits). So the LCP echo method
is probably preferable.

However, I have found that under heavy usage, that this method
has a few problems. When I saturate my 128k Jetstart link, there is often
no reply to three requests (LCP_FAILURE=3) and the modem disconnects. In
one 12 hour period of heavy usage I was disconnected 28 times. I tried
it out later just to be sure and got 6 disconnections in 2 hours (before
I gave up).

So I changed the settings to:
        LCP_INTERVAL=14
        LCP_FAILURE=6
        PPPOE_TIMEOUT=100
and saturated the link (at least the download bit) for 12 hours. There
was just one disconnection (after 5.5 hours). Seems like a big improvement.
I hope this helps all the people out there, and I hope it helps me with
the not-easily-resumable downloading.

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Received on Sun Mar 18 15:22:16 2001