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Date:      07 Dec 2001 15:21:54 -0500
From:      Andrew Heybey <ath@niksun.com>
To:        Lars Eggert <larse@ISI.EDU>
Cc:        Mike D <d01f1n@yahoo.com>, hackers@FreeBSD.ORG
Subject:   Re: cable modem connection problem
Message-ID:  <85k7vyzspp.fsf@stiegl.niksun.com>
In-Reply-To: <3C100F4D.3080900@isi.edu>
References:  <20011206071926.QTHW27606.mta05-svc.ntlworld.com@there> <3C0F7966.908CD6E6@bturtle.ch> <3C1005ED.4090001@isi.edu> <20011207000918.JIID10846.mta07-svc.ntlworld.com@there> <3C100F4D.3080900@isi.edu>

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I'm going to answer these questions to provide another datapoint (even
though they are not addressed to me) because I have seen exactly the
same behavior with my cable modem:

> Mike D wrote:
> > going out. I haven't checked for either packet drops / RTT increase
> > (how?) but when I say slow, I mean for eaxmple to get www.google.com
> > up takes 5-10 minutes. Also other machines on the LAN can not really
> > get out at all.
> 
> 
> 
> If you ping/traceroute, do you see losses (and where)? If you look at
> "netstat -s" output, do you see retransmissions?

In my case, "ping -i 1" dropped very close to 50% of the packets.
"ping -i 2": they all got through.  "ping -i 0.5" dropped about 75% of
the packets.  It was almost as if something somewhere was allowing
only strictly less than one packet per second.

Traceroute lost on the last hop (if I remember correctly) before my box.

> > Somebody mentioned on this list that deleting the arp table entry of
> > the default router of the cable modem provider (as a cron job)
> > solved the problem.
> 

> Does this work for you, too?

Yup.

> > Could this have something to do with leases being renewed (by the
> > isp dhcp server and consequently the cable modem) and FreeBSD not
> > updating routing tables? (I'm guessing big time here - not an expert
> > by any means)
> 
> 
> If your cable modem provides IP, it's probably not involved in the
> DHCP negotiations. Does your IP address change before you start to see
> this slowdown?

No new address.

I wondered if there is not some parameter that windows supplies
in the DHCP request that dhclient does not?  This started happening to
me when my cable company (with @home) took over the cable modem isp
business from my old ISP.

andrew

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