What is DLM?
DLM, (Dynamic Line Management) is the Openreach system used to monitor and control the speed / stability of FTTC circuits. All FTTC services provided by Ghost will prioritise speed over stability within thresholds defined by the DLM system for the current enforced profile.
Day of install
When your service goes live on the day of install. (depending on line conditions) DLM might already make changes to the line such as enabling interleaving or error correction. Both interleaving and error correction can add latency to your experience (between 9-18ms) as by their very nature, they are designed to correct errors on the line. This is something we want to avoid!
What can be done?
We allow 2-5 days after install for DLM to settle on a line before we can take a closer look, as in most cases the line will sort its-self out.
For lines that remain on an interleaved profile after this time, we will review options to see if it’s possible to remove this, such as lowering the sync speed profile. Typically, lines that remain on an interleaved profile will have a reason why.
Each line has its own characteristics and acts differently. DLM on FTTC is fully managed by Openreach with limited options for service providers to make / request changes. However, we will do all we can to provide the best possible service for your line.
Instability
When we provision a copper based broadband service, we select a “Speed” or “Standard” profile depending if the service is WBC or GEA provided.
These profiles operate with more leniency and result in DLM being less aggressive with the aim of keeping interleaving disabled and enabling G.INP with a lower SNR where supported.
On some lines this can result in service dropouts and DLM not taking any corrective action. Where this occurs, we may have to manually increase the stability profile via a service modify. This can take up to 48 hours per change request and will reset DLM “learning”.
We can raise the stability profile 2 “levels” after a change we have to allow the new changes to take affect and DLM to re “learn” which can take 5 working days.
Changes can also result in interleaving being re-enabled.