Leaving Modem connected?

securityguy

I think the whole Internet speed thing is a case of people arguing from limited data, and those who really understand it aren't talking. I was one of the designers of the original BT ADSL offer (indeed, it was me that pitched the basic "never mind films and sport over DSL, what about Internet provision?" in 1996) and I had some significant involvement in DLM, but I've not worked in that area for some years. However, I'm sceptical as to whether when people talk about "speed" it's really DLM that's involved.

Consider my situation. I've got a slightly unusual setup in that I have a cheap DLink DSL modem acting as a bridge, and an enterprise router running PPPoE actually talking to my ISP. That means I can tell the difference between a DSL retrain (which is basically between me and the exchange, with the results reported up to my ISP as part of whatever backhaul technique they use) and a PPPoA/E restart (which is between me and my ISP, based on the reported DSL performance plus anything else the ISP cares to throw into the blender). People using a router with the ADSL integrated can't tell the difference.

The modem stays on all the time, so from a DSL training perspective I've been online for a month or more. I used to collect the stats daily, but foolishly I upgraded the firmware and broke the backdoor I used to get the information automatically, but it was pretty solid for two or three years (I reduced the density of the graph by removing all the duplicate points: in reality, there's a data point at 3am every day recording the line speed at that moment). Since I broke the graphing my line has been up continuously, and it's as I type negotiated at 15736k downstream.



Because I've been testing and configuring some stuff over the month, the PPPoE session drops out and restarts several times per day. And the speed of that has been all over the shop, and my ISP's perception of my line speed (which is re-calculated each time I restart the PPPoE session, not just when I restart the DSL) is headed markedly downwards:



There's been some other changes (I don't have Annex M any more, for example) and this is not remotely scientific. But my ISP is definitely changing their perception of my speed massively more frequently than I'm resyncing my DSL, and even though my DSL connection has been up for a month, cycling the PPPoE (PPPoA from the ISP's perspective) appears to have a pretty bad effect on negotiated throughput. My ISP is rate-limiting my download based on (I suspect) congestion and error rates. Because I'm cycling the PPPoA/E connection regularly, they're probably seeing it as an unreliable line and backing things off a bit to reduce errors. Hmm, that graph's a bit violently downwards, I think I'll have a chat to them and see what their take on it is.

closed

adsl routers can disconnect and reconnect manually too. Any system that interprets an overnight router switch off or a manual disconnect signal as an error condition is clearly flawed.

meanwhile back at the ranch, rebooted router, sync speed and ip profile and speedtest went UP.

aqua111

Just realised how little I know about the technical side of Computers!