BUSINESS BROADBAND SHDSL AND MPLS SERVICES

How to evaluate a DSL Service
There are so many offerings out in the market that it can be really hard to compare what they offer. How can you decide which DSL service is right for you?   The key considerations are
a. Performance
b. Reliability
c. Support
d. Value Add
e. Cost

Key Considerations
a.  Performance  
To illustrate this we will use a 512/512kbps SDSL (Symmetric Digital Subscriber Line) line as an example though the points apply to any service.  View the explanatory diagram at http://www.rosser.com.au/news/newsletter/Aug20042.htm

When you sign up for a service of a particular speed, you expect to get that speed but things may still run slowly.  The first point of congestion is the local loop.  Based on our example, if you are trying to download at more than 512kbps or upload at more than 512 kbps then you will create congestion on the line.  Your performance may also suffer from traffic that you didn't generate such as worm traffic, hacker probes, SPAM and denial of service attacks.  For all of these problems, your ISP is not really to blame.  Our Bandwidth Doctor Service can diagnose and these problems and recommend solutions.

http://www.rosser.com.au/solutions/bandwidthdoc.htm   Where it gets interesting is looking at the next step upstream. Your line terminates in a DSLAM (DSL Access Multiplexer ) in the local exchange with many other services.  From there your ISP must 'back haul' all this traffic to their point of aggregation (POA).

This backhaul costs money and every carrier will take care not to pay for more than they need.  But how much is that?  If they had 200 customers with a 512k service who all used their link flat out at the same time they'd need about 100Mb/s of backhaul for that exchange.  That would be a 1:1 contention ratio and very expensive.  The actual situation is very different.  Most customers hit 100% utilisation only for very short periods & average more like 5-8%during business hours.  So a service is considered business grade if the contention ratio on the back-haul is 20:1 or less.  Actually, the better carriers don't use a fixed contention ratio, they monitor the utilisation of the backhaul and add bandwidth as needed to prevent congestion.  For example, Request (now Powertel) and Comindico. 

Stay away from 'residential ADSL' where the backhaul contention ratio can reach 100:1   Does this mean that if you choose a residential based service you will get what you've paid for?  Not necessarily. Once the data has been
hauled back to the carrier's main point of aggregation (usually in the nearest capital city) from all the exchanges in the region, it still has to get to 'the internet'.  This is another point of possible congestion where ISPs can save money at your expense.  It is relatively cheap for an ISP to buy their upstream bandwidth 'by the pipe', eg an unlimited 10Mb/s service where they don't pay for download.  If their total customer base is paying for a combined throughput of 500Mb/s then, in the example, they've oversubscribed their bandwidth 50:1.  This may be OK for residential users who aren't online often but will not be acceptable for businesses.

Our SHDSL and Ethernet service does not get squeezed through a pipe like this - we pay for every megabyte which gives us priority and we are connected directly into their core internet at wire speeds. It is important that business grade customers ask questions to check on both bottlenecks. 

b.  Reliability  
Although reliability has improved enormously there are still outages and there are differences between carriers.  To assess this you need to know who owns and manages the DSLAM and whose infrastructure you are traversing.  Carriers such as Powertel and XYZ (Optus) have a better track record of uptime and better service guarantees that suit business connections.  

c.  Support  
Check Service Level agreements & availability of support to trouble shoot your service. Do you need your routers managed? Under maintenance? What do you do if your router dies? 

d.  Value Add  
Apart from the above, what features should you consider?
Powertel exchanges can handle symmetric services- something essential for offices running VPN & ecommerce.  can your current service provider do this?  Is Voice over DSL something your business may need? Is traffic prioritisation necessary? 

e.  Cost  
In summary, you get what you pay for. Cheaper bandwidth usually means inferior bandwidth that may cause time sensitive traffic to suffer.  Also, costs are falling so don't sign contracts for more than 12 months and review you carrier regularly. However, if you are on an private IP network, consider a 2 year contract minimum otherwise the initial costs of the hardware and installation is too high for only 12 months use & to return a significant ROI.