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Traditionally, a DSL customer's synch rate was provisioned directly on the DSLAM and hard set to a specific profile. A customer with a 256/128Kbps service would synch at 256/128Kbps between the DSLAM and the modem, regardless of the overall attainable line rate possible. MaxSync introduces two important differences.
1. The synch rate is no longer provisioned on the DSLAM. The DSLAM and modem will synch at the highest rate possible (within certain criteria).
2. Service speed is controlled via a RADIUS profile.
So the customer mentioned above with 256/128 service could possibly see a 8128/512 synch rate if they were changed to a MaxSync profile depending on their individual line conditions yet only have 256/128 speeds to the Internet.

The good news
Changes can be done without reprovisioning the DSLAM and accomplished with a simple RADIUS change. MaxSync enables the possibility of offering bandwidth on demand services in the future. It also gives the customer and BellSouth the ability to gauge the overall condition/capability of the customer's loop. If a customer's line can only MaxSync at 3552/384 they obviously would not be a good candidate for the 6000/512 service. Conversely, a customer currently on 256/128 that MaxSyncs at 8128/512 shouldn't have any problems upgrading to 3000/384.

The bad news
Generally, higher sync rates and bandwidth lower the overall signal to noise margin and increases line attenuation. The MaxSync profile could create problems for a customer that were never an issue before. For example:

1472/256 service with traditional provisioning at the DSLAM
- Marginal line with attainable line rate of 3600/500
- Signal to noise margin of 10dB
- Line attenuation of 55dB
- Loop Capacity is about 41%
The customer has never had any problems even tough the line is marginal because of the low synch rate.

Same 1472/256 service set to MaxSync profile
- Marginal line attainable line rate of 3600/500
- MaxSynch rate of 3552/384 (possibly with interleaving)
- Signal to noise margin of 7dB
- Line attenuation of 60dB
- Loop Capacity is almost 100%
The customer may now experience connectivity issues and may have also be placed on interleaved profile. Although newer interleaving techniques have reduced the overall latency as compared to older methods, it still introduces some latency.

Important Information:
Due to differences in network topologies, MaxSync is not available to all FastAccess customers.

Additional Information:
How do I check modem statistics? What do the numbers mean and are my stats good?
What is Interleaving and Fastpath?

Andy Houtz DSL

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last modified: 2009-04-16 11:07:13