MSILs are the bits of kit that link ISPs' systems to the BT Wholesale backhaul. The 21CN equivalent of BT Centrals on 20CN if you ever heard of those.

So all traffic between you and the ISP and back goes through an MSIL. Connection is:- Your modem >> cabinet DSLAM >> Openreach exchange kit >> BT Wholesale MSAN >> BT cloud >> MSIL >> ISP routers/servers.

In reply to a post by lexden16:

65Mbps down and 9.8Mbps up.

I find that speedtest results for upstream on fast connections underestimate by considerably more than downstream tests. Most put miy upstream at between around 12 but if I set a pile of data uploading to my external server in a single stream I see sustained rates closer to 17. The transfer starts slower but speeds up over the first ~10 seconds or more. I assume this is due to "slowstart" - part of TCP/IP's congestion management heuristics. Downstream is affected to, but not by as much - I assume the speedtest sites have tweak their TCP/IP settings to reduce the effect of slowstart in downstream tests, but they can't control those parameters at your end for the upstream test if they are only using flash and/or javascript for the test.

tl;dr: speedtest sites are known to be inaccurate (they are only intended as a guide not a precise measurement), but I find they seem to underestimate on 40/10 and 80/20 FTTC quite a bit more than they did on slower links.

In reply to a post by lexden16:

The error rate has increased slightly and there are more FECs(interleaving).

If you are getting double the throughput I would expect the error rate to approximately double (if you are meaning errors-per-time-period rather than errors-as-proportion-of-packets-sent).

In reply to a post by dspillett:

In reply to a post by lexden16:

65Mbps down and 9.8Mbps up.

I find that speedtest results for upstream on fast connections underestimate by considerably more than downstream tests.

http://forums.thinkbroadband.com/newsite/t/4115965-s...

NB:The situation is 'worse' now. Other testers show me as being 55/14. TBB thinks it's 55/8. As I noted in one of the later replies I have confirmed with a friend that my upload is at least 12Mb/s.

Edited by Andrue (Thu 17-May-12 10:37:21)

And I thought ADSL2+ was difficult to get my mind around! Thanks all.

I am in the fortunate position of being able to check my VDSL stats. I seem to have an anomaly that I cannot explain. My stats are showing an ADSL connection of 80/20 which matches a current throughput figure of 79992/20000. However, when I look at my System Log it shows DSL training following by a synchronisation of 44160/11040. A speedtest reveals speeds of 73.4 and 9.98. Having taken advice from others on a Fritz!Box forum, it would seem that other FBs are showing matching current throughput and synchronisation figures which is what I would expect. I am not bothered just curious. Any thoughts? I am inclined not to fiddle until I have a reason to re-boot the router.

In reply to a post by lexden16:

I am in the fortunate position of being able to check my VDSL stats. I seem to have an anomaly that I cannot explain. My stats are showing an ADSL connection of 80/20 which matches a current throughput figure of 79992/20000. However, when I look at my System Log it shows DSL training following by a synchronisation of 44160/11040. A speedtest reveals speeds of 73.4 and 9.98. Having taken advice from others on a Fritz!Box forum, it would seem that other FBs are showing matching current throughput and synchronisation figures which is what I would expect. I am not bothered just curious. Any thoughts? I am inclined not to fiddle until I have a reason to re-boot the router.

Just to close this thread with an update. I gave in and I left the Fritz!Box off overnight. When I powered it up, I again got DSL training followed by a 44/11 synchronisation. My stats showed a 79992/20000 current throughput and a BT Speedtest gave me IPs of 77.43/20 and speeds of 73 down and 9 up. As the Fritz!Box gets more updates than most boxes, I decided on a full factory reset followed by a manual re-install of my settings.

Immediately on powering up I got DSL training followed by synchronisation at 79992/20000. A further BT Speedtest gave the same IP profiles but my upstream rose to 17.65Mbps.

This may just be an isolated case but it serves to show that not all 80/20 upgrades go through smoothly. Moreover, it also shows that without the modem stats, a BT Speedtest will not reveal any issues.

That's great news, both the Fritz!Box anomoly and the BT hidden profile fixed in one go. Thanks for the feedback, I'm sure someone else will benefit from this in the future.