I wanted to start a new experience thread simply to discuss MTNL VDSL.
Some things to consider before/after taking a new VDSL connection
SNR margins (SNRM)
Below 9 dB : Poor experience with lots of HEC and CRC errors. Line will disconnect frequently.
9 - 11 dB : Ok but not ideal. Disconnections will be there if some unexpected variance is introduced by rains, humidity in the wire.
12 - 16 dB : Ideal and realistic value. Expect almost no disconnections as the line has more wiggle room for tolerating variances.
17 dB and up : God Mode. Lucky few get this on VDSL synced at 30 mbps and up. So far I have seen various stats and no one has reported this SNRM (That is because VDSL sync rates are always higher)
Higher you sync rate, lower the SNRM will be. Lower the SNRM, lower the connection reliability. Lower reliability means frequent disconnections. Hence ISP's have a setting in DSLAM to artificially increase SNRM value for a particular phone line. Hence you sync at lower rate and line automagically becomes stable.
Attenuation may not be that important after all. It reduces sync speeds over a distance but is not an indicator of connection reliability. (You can roughly calculate your line length from it. Do it here)
Apply for VDSL connection only if you are within half km. Otherwise you will get ADSL like sync rates.
I will update this entry with some of our findings. Since VDSL is somewhat new to India, this thread can help some early adopters.
Currently the speeds are decent for fast servers. But single streams are slow due to a bottleneck somewhere.
Some things to consider before/after taking a new VDSL connection
SNR margins (SNRM)
Below 9 dB : Poor experience with lots of HEC and CRC errors. Line will disconnect frequently.
9 - 11 dB : Ok but not ideal. Disconnections will be there if some unexpected variance is introduced by rains, humidity in the wire.
12 - 16 dB : Ideal and realistic value. Expect almost no disconnections as the line has more wiggle room for tolerating variances.
17 dB and up : God Mode. Lucky few get this on VDSL synced at 30 mbps and up. So far I have seen various stats and no one has reported this SNRM (That is because VDSL sync rates are always higher)
Higher you sync rate, lower the SNRM will be. Lower the SNRM, lower the connection reliability. Lower reliability means frequent disconnections. Hence ISP's have a setting in DSLAM to artificially increase SNRM value for a particular phone line. Hence you sync at lower rate and line automagically becomes stable.
Attenuation may not be that important after all. It reduces sync speeds over a distance but is not an indicator of connection reliability. (You can roughly calculate your line length from it. Do it here)
Apply for VDSL connection only if you are within half km. Otherwise you will get ADSL like sync rates.
I will update this entry with some of our findings. Since VDSL is somewhat new to India, this thread can help some early adopters.
Currently the speeds are decent for fast servers. But single streams are slow due to a bottleneck somewhere.
