News Big switch-over
During August 2009 we are switching lines over to IPStream Connect (IPSC). This page explains what and why and what that means for you as a customer.
In summary
Working with BT we are changing the way some lines are connecting within the network between BT and ourselves. It will mean a few seconds outage one night and that is it. You should not see any changes or problems if all goes well.
How it works
Originally 20th Century network (20CN) broadband lines provided using ADSL1 to customers (up to 8M) were connected over BTs ATM and IP networks to a pair of 155Mb/s BT Central links to us. The network largely used technology that had been around for decades. The links to us (BT Central) are expensive and difficult to manage
The new way of working with 21st Century network (21CN) means using ADSL2+ (up to 24M) which connect over a new 21CN IP network in BT and connect to us using a dual giga-bit link. This new link is much more flexible and economical.
At present we have both. For some time we have been upgrading individual lines from 20CN to 21CN as BT upgrade exchanges. This will continue for some years until all exchanges are upgraded. Running both types of network is expensive.
Switching over
In principle the switch over is simple. It means diverting the 20CN links within BTs 20CN network to the 21CN network so that we get all of the traffic, 20CN and 21CN down our new faster link to BT.
This has, however, taken something like a year longer than expected due to complications within BT. BT actually launched this link over a year ago, but that only got the traffic to 20 interconnect nodes for 21CN. Another part of BT had to build back-haul to connect in to the rest of the network to hand the traffic over to us. We never expected to be running both networks for any length of time, and have had to change our plans many times. Now, it is finally coming together.
Why change
There are two main reasons for the changes to 21CN: commercial and technical. On a technical front the end user connections on ADSL2+ 21CN are better and faster and the link to us is better and faster. On a commercial basis the links both ends are cheaper. We already reduced prices for this earlier in the year, before unexpected delays and costs.
One of the big advantages for us as an ISP with having all traffic on the new faster links to BT is that we can scale our operation now. As it was, we had two 155M BT Centrals. A third would immediately add an extra 50% to our costs for no immediate extra income. It would also cost around £50,000 and take at least three months to install. Had 21CN not come along we would have done that. The new link to BT is much cheaper for the link and costs match the usage. So if we have 10% more customers and 10% more usage and 10% more income we have 10% more cost. It is simple. It means as an ISP we can grow quickly or slowly, but always profitably. Even if we ever fill the giga-bit links, getting another is much much cheaper and quicker and simpler than getting new BT Centrals. This all means we can offer better value for money and also continue to offer a high quality of service as we are not hitting artificial commercial stepping stones any more.
There are benefits to customer apart from just price. The technical aspects of the new system allow us to manage bandwidth better and ensure we have spare capacity when needed. It also allows us to manage unexpected bursts (like major sport or news events) and do so in a better way with less impact on things like Voice over IP (VoIP). It also means an end to over night rebalancing of lines as the links to BT are not split up in to smaller virtual paths that have to be managed.
Time table
The change was completed 17th August.
Possible issues
There are several possible issues we have considered. The main one is we are not entirely sure how much bandwidth to allocate when we switch over as we are also moving a lot of individual lines to 21CN. Yes, we have to manage bandwidth separately for 20CN and 21CN even on the new link (BT charge around 50% more for 20CN than 21CN usage). We have to set this and stick with at least what we request for 3 months, and we cannot change faster than 5 working days. These are artificial constraints BT place on us, and a real nuisance. However we also have some bursting capability (at a cost).
In short this may mean that for the first few hours, and possibly to some extent for the first week of switch over the internet may be slightly slower than normal on 20CN lines. We don't expect so though.
Contingencies and back-out
There are also other possibilities we have to consider...
- What if IPSC does not work? We are switching around 100 lines over first and testing for 2 weeks. There has already been a long test process with a number of internet providers that worked well, so we have no reason to think there will be any issues. If these lines fail we can abort the whole process and try again later when we and BT are ready.
- What if the new IPSC system fails after switching over? We are retaining a BT Central link for 2 months after the process starts. This will allow us to switch customers back within around 15 minutes if there is a major failure. We are moving a lot of lines to 21CN so one central should just cope with the remaining 20CN lines. It certainly makes sense as a temporary fall-back in the even of a major failure.
- What if BT do something unexpected like withdraw the service? This is a new product and BT and ourselves are taking it one step at a time to make sure it all works. If there are too many issues it is possible that BT, or ourselves, could decide that the service is just not ready and cancel the whole thing. If this happens we will switch the 20CN lines back to the BT Central we are retaining and cancel the cease planned for October. By then we expect to have moved enough lines to 21CN to make the service viable on one BT Central rather that two. Obviously, having done that we will continue to migrate lines to 21CN and so provide more capacity for remaining 20CN customers as time goes on. We know BT are very keen on this and would expect BT and ourselves to try this again at some point. However, we expect this to just work and abandoning the whole project is extremely unlikely.
When we switch lines over, we will retain a test line on the BT Centrals and install a new LNS with new traffic monitoring which will make it easier to manage should we have to switch lines back at all. We will then test the fall-back on this test line just in case.
Thanks to BT
We'd like to take the chance to thank Mandy in BT for getting the sign off on the whole migration process for IPStream Connect. This has allowed us to maintain an existing BT Central while migrating lines to IPSC without paying twice for the bandwidth. Without this the process would be much more risky and expensive.
