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21CN Broadband MSE bRAS

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BT Wholesale is introducing new Multi-service Edge Broadband Remote access Servers (MSE BRAS) to expand the 21CN broadband platform that supports WBC/WBMC.



~ What is a BRAS?

The Broadband Remote Access Server (BRAS/RAS) is a major component of any DSL access network. It can be thought of as a super hub where users traffic is merged on to the core network.  

The bRAS undertakes several important tasks:

  • Aggregation of traffic
  • Policy Management (QoS etc)
  • Authentication on to a network

The bRAS is the first major hop of your connection to the Internet. The terms BRAS, BBRAS and RAS are used interchangeably.


~ BT Wholesale bRAS

BT Wholesale has ten 20/21CN bRAS which are located at Birmingham, Bletchley (MK), Ealing, Edinburgh, Ilford, Kingston, Manchester, Reading, Sheffield, Faraday.

These 8, then 10 Broadband RASes have served the whole of the UK for more than 14 years and will have been responsible for making sure that your Internet traffic goes to the correct ISP. If your ISP uses BT Wholesale for routing then you can be sure that all your traffic will have passed through one of the above bRAS locations.

Today we require much more from our broadband connection than even just a couple of years ago. Most households and work places now have access to the Internet. Broadband speeds have got much faster and demands for bandwidth has grown enormously.

To cope with the increase demands BT have embarked on expanding the 21CN platform and deploying several hundred Multi Service Edge (MSE) Routers at multiple locations around the UK.


~ What is a Multi Service Edge Router?

These powerful routers sit on the edge of the main backbone or core network.

They converge and aggregate traffic from multiple VLANs/SVLANs on towards the 21CN core network. Depending upon the make and model they can route up to 400Gbps of traffic on to the core network.

They can perform QoS, translation of network protocols, support a wide variety of communication technologies etc. One of their main benefits for BTs 21CN network is that they undertake authentication access on to the core without the need for a separate dedicated bRAS server.

It is known that BT has purchased a large volume of Alcatel-Lucent 7750 Service Routers. It is not known if these are used at all locations.

Alcatel 7750 Service Router
Alcatel 7750 MSE


 ~ What are the benefits of MSE?

Previously authentication was carried out at the BRAS at one of only 11 locations in the UK. Allocation of the old RAS's wasn't always geographically logical and could extend traffic routing causing slight additional latency.

Deployment of MSEs brings the authentication process much nearer to the user and more logical access to the Core Network. Bringing bRASes nearer to the customer may see very slight improvements to latency.


 ~ How many MSE's have been deployed?

This is unclear.  In early 2013, BTw said that they aimed to deploy 535 MSEs.  An update in November 2013 stated 219 MSE's in place and a total of 457.
Elsewhere in SIN 471 dated Aug 2014, it says that "There is the potential for the number of WBC BRASes to grow by up to 2560 in future."

A list of known MSEs can be found here: 21CN Multi Service Edge (MSE) Locations


 ~ Notes

From what I can gather, not all services may have been moved over to MSE's yet. 

At the present time (Oct 2014) it would appear that NGA products (ie fibre) are/have been migrated first. For example my own exchange still has several 21CN VPs/VLANs from the exchange MSANs, but since this year FTTC services are now routed via an SVLAN to a much larger neighbouring exchange.  This larger exchange still has a few of the old VPs, and its own SLVANs, but would also appear to be taking in SVLANs from several other local exchanges.

Time scale varies depending upon location.  Some areas have had MSEs deployed since 2013 and some are now also routing traffic from the Copper MSANs. A lot of migrations appear to have occurred during Sept/Oct 2014 and is still ongoing.  Eventually the old RASes will be retired.


Last updated Nov 2014

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