XVI. DSL Diagnostics

Some VDSL2 lines in the UK are now using G.998.4 / G.INP as an alternative to interleaving. Both are methods of protection against data errors caused by noise or interference to the line. For a more detailed explanation of G.INP, click here.

Lines that have this enabled do require the router's modem code to support it, otherwise the latency seen on the line may increase.

G.INP support requires using the VDSL firmware (modem code 574307) from the DrayTek UK site, the modem code used by the ADSL firmware (modem code 548006) does not support G.INP. Please check your specific router/modem's specification to check if it supports G.INP / G998.4. If it is supported, but you have older firmware, you may need to upgrade it for support.

Some VDSL line are using Vectoring. The presence of crosstalk can reduce the maximum synch speed that a line could obtain and vectoring is a method used to protect against crosstalk (a form of interference) from neighbouring VDSL lines by coordinating the transmission of the signal of each line and putting them into a vectoring group which is managed by the MSAN. The coordination of the transmission allows, using noise cancelling technlogy, some affects of crosstalk to be cancelled - thereby enabling the line to sync at rate it could be capable of had it not been for the affect of crosstalk. Noise or interference from sources which are not part of the vectoring group can reduce the benefit of vectoring.

You can check if your router is using G.998.4 / G.INP from a telnet command as follows. Replace 192.168.1.1 with your own router's IP address if you have changed it:

1. On Windows go to the Start menu, select Run and on there type "cmd" and click OK, or if the Run option is not present, type "cmd" in the "Start Search" textbox above the Start button and press enter. Other operating systems also have an equivalent telnet program or app.
2. Type "telnet 192.168.1.1"
3. Enter the username of "admin", press enter, then enter the password for the router.
4. Enter "sys ver" to show the firmware version and modem code details.
5. Enter "vdsl status more" which will show the following:

The router firmware you can see highlighted is version 3.7.8 and the modem code is 05-06-07-05-01-07 (which can also be written 567517).

The ReTxEnable setting relates to G.998.4 support, if the value is "1" then it is active on the line. 0 (zero) indicates that it is not active. The right hand column is downstream (your received data) and the left hand is upstream.

Type "exit" at the telnet prompt to close the session.

To check if your line is using Fast or Interleaved mode, see this article.

You can check to see if your line has vectoring activing by looking for the words "Vectoring Active" in the VDSL2 Information section of the [Online Status] page as shown in the screenshot below.

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