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Old March 23rd 15, 11:27 AM posted to uk.telecom.broadband
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Default Packet loss seems to have increased, how to diagnose?

Graham J wrote:
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

Yes, I know, but still I do at least now have a responsive internet
connection. Next time, if I have the patience, I may try a bit more
diagnosis (if there is a next time of course!).

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.

Yes, OK, I did try 'nearby' IPs such as the ISP's DNS. They all
showed the same level of packet loss.

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.

It was (I am almost certain) a bad ADSL connection between me and the
ISP, not an issue with ISP connectivity beyond.

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

It's showing 8 now. I still have the slightly improved speed, it's
4.7Mb/s as opposed to the 4.0Mb/s I was getting before.

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.

Dropping the connection and reconnecting has reset the counts. It has
been up just on 24 hours now and I have 1472 receive CRC errors and 35
transmit ones. (RX cells 246749443, packets 735020). I make 1472 in
735020 about 1 in 500 for receive.

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

I'm with PlusNet, they reset it for me some months ago when my speed
had migrated down to 3.3Mb/s or so and wasn't climbing back up. I'm
very happy with 4.7Mb/s, it's as good as I've ever seen from here,
over the years I've usually seen about 4.2 - 4.4Mb/s.

Thanks for all the comments/advice.

Chris Green