I applied 4.0.18 on my 877 routers to resolve the problem

regards

I’ve got a very similar problem here with ADSL2+ with our Cisco 837 routers. After reading about it has become apparent a firmware upgrade will perhaps cure this? Does anyone have the latest firmware for this particular router at all please?

Many thanks in advanced.

Windows 7 time is now specified as UTC. All previous version of Windows including Server 2008 still operate in GMT. (I expect the next version of windows server to operate in UTC time)

If timezone redirection is enabled in Group Policy and the ICA client is running on a linux device then the timezone information is not passed through the ICA session.

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“The default setting of “do not pass through timezone redirection” should be kept i.e. “disabled”. This overides any further settings made on the citrix farm.

By default, the session time zone is the same as the server time zone, and the client computer cannot redirect its time zone information.

If the status is set to Enabled, clients that are capable of time zone redirection send their time zone information to the server. The server base time is then used to calculate the current session time (current session time = server base time + client time zone). Currently, Remote Desktop Connection and Windows CE 5.1 are the only clients capable of time zone redirection.”

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This was diagnosed to a lack of capacity across the ISP’s backbone. The ISP increased capacity and the CRC errors went away.

A combination of the new Firware on the CISCO routers and the increase in capacity across the backbone has stabilised the problematic sites.

The ISP is recommending that the firmware upgrade is applied across the estate to prevent further sites becoming degraded.

Answer
This is not offered as an official resolution from BT. As mentioned above, the main problem was identified as a capacity issue. The stability settings and interleaving settings should only be adjusted only if there are further problems with a site now that we are sure the firmware and capacity issues are not contributing to the problem.
Interleaving is error correction on the line at BT’s side which will try to remove any errors in the data that is passing through the line, this is used to remove errors on the line by correcting any corrupted packets before they reach the EU router and has a side effect of higher ping times due to the time it takes to check and correct any packets before being passed onto the EU router.

SNR is the buffer in the signal between the throughput and noise on the line, the higher this is the bigger the buffer and lower effect any noise or line imperfections have on the connection, a side effect of raising the SNR is that there is less signal for the download speed so downloads will be reduced in speed. SNR can be used to eliminate errors on the line without the need for interleaving if those errors are due to noise.

The stability options reduce the delay on BT’s systems before either of these two options are changed. As a rule the standard stability option will allow for 12 drops within a 24 hour period before increasing the SNR while setting the line to Super stable will cause the SNR to rise after 3 drops in the same time period

Interleaving in detail
http://www.kitz.co.uk/adsl/interleaving.htm

SNR in detail
http://www.dslzoneuk.net/adslmax_explained.php – note, when we refer to changing the SNR it is the SNR margin mentioned here that is changed.

This would leave us to believe that an SNR attenuation is still requierd even with the replacement Zyxel router to stabilise the site.

Further routers at the remainder of the degraded sites will be installed over the course of the day.

There is still no news of a Cisco IOS firmware fix.