Wednesday, March 5. 2008Carrier Bottlenecks - Is There A Solution?John Linton One of the things I never expected to have to deal with, and I'm sure that demonstrates my inexperience and naivety, is being a commercial provider of services to end users that is dependent on third parties for the quality of those services. I realise how stupid that makes me sound/read. For most of the past 24 months we have noticed an increasing number of inexplicable (to us) degraded performances across the country that 'ebb and flow' and can never be tied down to a specific scenario. Over the last three months of drenching rains in much of Eastern Australia these instances of slow speeds have been somewhat masked by the significantly increased number of "drop outs" and long periods of "service unavailability". Over the last twelve months there is no doubt that Exetel's moves to use P2P filtering and, over the past 3 months, P2P caching may have contributed, slightly, to some strange instances but not really that much - in fact those initiatives have given much more positive than negative results to the overwhelming majority of Exetel broadband users. What is becoming very clear, both to Exetel and without any doubt all other ISPs and carriers is that, as ADSL2 and higher speed ADSL1 services account for a larger percentage of total network use, the overall demand for bandwidth increases in every section of the network path is exceeding even the most generous allowances. For example - when Exetel connected its first broadband customer in February 2004 we provisioned the bandwidth between the customer and Exetel and between Exetel and the 'outside world' at a ratio of 25 kbps per customer - which had been over the preceding 3 years of providing ADSL1 services via other companies on the generous side. Over the past 4 years that provisioning ratio has risen to around 50 kbps for ADSL1 customers which reflects usage of streaming video and much wider use of P2P. OK - surprising but understandable and with the fall in pricing of IP bandwidth (no fall in customer connectivity bandwidth pricing) sustainable with only relatively minor end user price increases - the other mitigating factor over that time being the reduction in ADSL1 port rental costs from Telstra Wholesale. What is clearly not sustainable, at least by the carriers in terms of their back hauls, is the dramatic impact that ADSL2 services have had on those parts of the networks (from the end user via the carrier's network to the ISP). Exetel originally provisioned the parts of its network used for ADSL2 traffic at 50% greater than the parts used for ADSL1 traffic (per user). However over the two years we have been providing ADSL2 services we have increased that to 100% greater than ADSL1. We would be prepared to increase it to, say 200% of that provided to ADSL1 customers if we now believed it would eliminate the constantly shifting (geographically) end user complaints of periods of slow speeds can't play games etc, etc., but we have reached the point where we see no congestion/saturation at any time but there are still issues with packet loss and speed degradation. While it may well be that there are still issues we need to address that we haven't yet identified I, non-technical person that I am, have reached the end of my ability to believe that this is the case. I wouldn't be surprised if we now found something that we had overlooked but I no longer think it's remotely likely. The problem is almost certainly summed up in one of the carrier's contracts with a clause that states: "Carrier" will use its best efforts to maintain bandwidth equivalent to 30 kbps except if other ........: The other two carriers make no such statement other than to say they don't guarantee anything. So there is the problem: We see a need to provision an ADSL2 service at 100 kbps per user and at least one carrier sees it being acceptable to provision it at 30 kbps by contract although they do say they actually "over-provision" it at the moment - by how much they don't say.. I'm not sure what can be done in the immediate term. Stop selling ADSL2 services? Seems to be the only way forward. Trackbacks
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I for one was affected horribly by the Optus backhaul issues last year and never want to have that sort of connection issues again. It was horrid. I had to resort to dial-up on several occasions - it was actually faster.
Speaking to Exetel staff last year they indicated obliquely that Powertel provisioned a lot more generously and I seriously considered disconnecting from Optus and re-signing up to Powertel. However judging by your comments here: http://johnl.blogs.exetel.com.au/index.php?/archives/229-Enjoy-It-While-You-Can.html they are having issues as well now. 30kbps! Sheesh! No idea how they think that's acceptable. Can you possibly get some sort of backhaul provisioning written into future contracts? If the service was un-acceptable I'd stop providing/provisioning it! Big step for Exetel to take. Do you think it would make providers / other ISP's sit-up / listen / actually acknowledge the issue? Comments (2)
We are considering that but it means we would effectively cease providing ADSL services within a year.
Perhaps that's the only real solution. ISPs who have deployed their own DSLAMs can control their own back hauls so any problem they may have is simply their own policy decision. I've been considering these issues for some months now and I see no solution. Comments (3)
Because your backhaul is UDP (L2TP) it's 'unreliable transport' yet is providing the transport layer for IP for your xDSL services. If bandwidth on backhaul is marginal, it'll go to crap faster than you can count the miserable margin you're making and will affect everybody (tunnel degradation).
If you're not already, you might want to keep an eye on bandwidth graphs (mrtg) and establish what's your upper thresholds for peak and average. Also have your tech report the sub-5-minute interface stats from your L2 edge devices as these will be averaged out by mrtg. Maintain these and then see what your contention ratios work out at (while looking for a new vocation). PS I can't see that wireless is a panacea for your malaise assuming you'd also backhaul for wireless. If you're going to use a layer 3/visp product for wireless then wouldn't it all be equal to using a visp product (ie Soul) for wireline now (which probably would not work for you)? -Rattus Comments (2)
Just as importantly, if you control your own exchange backhaul you get better visibility to where the bottlenecks are.
Comment (1)
I would have assumed that an ISP that provisioned its own back hauls would never have that problem.
Though, empirically, that is clearly not the case. Comments (3)
The most likely point of contention (imo) is the ISP edge. Beyond that, each LEC will impact the delivery also though we hope not to the point of packet loss.
Resorting again to anecdote, Telstra is reputed (by lore) to provide backhaul for L2IG with managed contention of 100:1 although this is a 5 year old value and it's always been mooted to be higher (all quite harmless in reality). However, Powertel's backhaul for their business products has a much reduced contention - shall we guess 15% of the above? This includes (anecdotally) backhaul through to their Telstra ports making this the very good product we know it to be (albeit with craphouse provisioning GUI and no API). The Optus backhaul is a different fish altogether and it's not public info nor 'aged into the public domain' so I'm/we're not at liberty to discuss it. I doubt that it's your problem but you would logically look into this for your Optus aDSL2+ after acquiring your empirical data on your edge devices to ensure you're not dropping packets due to a lack of provisioned capacity into Optus (for backhaul and this is the most likely cause imo) - or due to a routing anomally (you should also check this really carefully). Comments (2)
Yikes, roll on an affordable wireless solution!
Fingers xxxx'ed you find one soon. Comments (2)
I appreciate the difficult position you find yourself in all too well, as I am one of the unfortunate customers of exetel that appears to be very badly affected by backhaul provisioning.
My ADSL2+ service runs at almost dialup speeds after midnight. Do you think that continuing to offer/advertise an adsl2+ service to the general public - when your company is very aware of the fact that there are significant technical obstacles uncontrollable by exetel preventing many of those potential new users from obtaining a decent adsl2+ service - is an ethical and decent business strategy? I am waiting for exetel's internal fault resolution processes to establish why my speeds drop to almost dialup at 00:01 every night. This has happened since I signed up in late january. If exetel discovers that the reason I am getting sub 512/128 speeds is inadequate backhaul, then perhaps I can expect a no fault dissolution of my contract and a penalty free move to another provider that can try to provide me with the service that they advertise? Comment (1)
Provisioning provisions by ALL carriers and I doubt that any ISP is any exception is having to be changed from the provisioning policies of the past.
ALL carriers. This means that the manifestation, as far as I can see, is that the cariers are playing 'catch up' in terms of additional provisioning instead of, largely, staying ahead of growing demand. For those people, like me, who were an early user of BigPond ADSL would remember what those days were like. Any person whose speeds drop to zero at midnight has a problem completely unrelated to carier provisining. Comments (3)
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