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Old March 23rd 15, 09:47 AM posted to uk.telecom.broadband
Graham J[_2_]
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Posts: 723
Default Packet loss seems to have increased, how to diagnose?

My son and I both felt recently that "the internet seemed a bit slow".

Well a disconnect/reconnect of the 2820n to the phone line seems to
have fixed it. It's renegotiated its speed up a bit too. :-)

Sadly, re-syncing the ADSL modem or rebooting the router will cure a lot
of things, but then you never know why the problem occurred in the first

As regards ping, the first IP address to try would be the Default
Gateway shown in the router. On a 2820n this is called GW IP, in the
WAN1 Status section.

This is the first router in the chain between you and the rest of the
internet, and is generally operated by your ISP. If pinging it is
unreliable then you should take it up with your ISP. However be sure
that you don't have other network traffic using some of the available
bandwidth - this may delay ping responses (by design, ping has a very
low priority). The 2820 will show you a traffic graph to allow you to
identify whether there is any other usage.

If this is reliable, but other addresses (such as are
not, then it's an issue for your ISP. Try several different addresses
from services that likely to have high availability.

Your 11dB SNR margin is not ideal. Having rebooted, what is it now?

If you reboot the router the TX/RX cell count, and TX/RX CRC error
counts should all reset to zero. Note the counts, and work out the
error rate as a proportion of the total packets. Yours look acceptably
low (1 in 10^4 and 1 in 10^5) but beware that all the counters wrap and
I don't know at how many digits). So monitor every few hours.

Also note whether the error counts increase smoothly, or stay fairly
static and increase rapidly on occasion. RouterStats would help here,
but I don't know how to make it work with a 2820. I think I had it
working with a 2800, and certainly with a 2600. Any sudden increase in
error counts would indicate an intermittent noise problem.

If the noise margin increases and the speed consequently decreases your
BRAS profile will reduce, and may take some time to return to its
previously good figure. With some ISPs (BT, Demon) this never happens
and you have to threaten to migrate away to get them to reset it. The
perceived speed will stay slow until the BRAS profile returns to its
former good value. Does your ISP give you a mechanism to see the BRAS

Graham J