BT Central/ Central Plus Features & Benefits
BT Central
A BT Central links BT Wholesale"s broadband network and a Service Provider"s premises
and is used to aggregate and back-haul End User traffic.
There are six BT Central options to choose from, offering a range of data-rates and number of
simultaneous sessions supported:
2 to 34 Mbit/s
2M/bits
10Mbit/s
34M/bits
Sessions supported
250
1600
1600
Service level
TotalCare
TotalCare
TotalCare
Interface
10baseT
100baseT
100baseT
Physical interface
RJ45
RJ45
RJ45
Network Terminating
Equipment (NTE)
Cisco 3640/3725
Cisco 7204VXR
Cisco 7204VXR
155Mbit/s
155Mbit/s L2TP
622Mbit/s L2TP/LNSv1
Sessions supported
6400
8000
25600 max
Service Level
TotalCare
TotalCare
TotalCare
Interface
Gigabit Ethernet
Single Mode Optical
Fibre
Gigabit Ethernet
Physical Interface
STM-1
STM-1
STM-4
NTE
Cisco 7204VXR or Cisco
ADM
7507
155 Mbit/s - 622 Mbit/s
For further information, please see SIN329
2 x Cisco 3550
Lead Times
The standard lead time for provision of the variants of BT Central are:



2Mbits/s - 35 working days
10Mbit/s, 34Mbit/s, 155Mbit/s and 155Mbit/s (L2TP) - 65 working days
622Mbit/s (L2TP) - 77 working days
Please note that the maximum radial distance reach of BT Central 622Mbit/s is 25km from a
BT IPStream PoP site. All other variants of BT Central have a fixed rental price up to a radial
distance of 40km from a BT IPstream PoP site but can be extended beyond 40km at an
additional per km rental charge. All installations are subject to a site survey.
Layer 2 Tunnelling Protocol (L2TP) pass-through option
The L2TP option offers a tunnelled presentation rather than the standard BT Central routed
presentation and is available on the 155Mbit/s and 622Mbit/s service. With L2TP, End User
sessions are passed through to the Service Provider’s network, giving greater flexibility to
control the termination of PPP sessions. L2TP is ideal for Service Provider central
management centres or central IP address allocation. To use the L2TP option, Service
Providers must provide the infrastructure to terminate the End User PPP sessions.
Further Information is available in SIN 374
Pricing
Service providers can choose between charging methods for BT Central. Three options are
available: standard, usage or capacity based charging. For further pricing information please
see the Service Provider Price List.
For further information about these pricing options please contact your BT account manager.
BT Central 622Mbit/s Flexing Bandwidth Rental Charges
For the L2TP and LNSv1 options on the 622Mbit/s service, an Service Provider can order
any one of the bandwidth increments to begin with and then flex this up to the maximum at
any time during the first 12 months. At the end of this 12 month period, the full BT Central
622Mbit/s charge will apply regardless of the current increments being rented.
Full pricing information is available from the Service Provider Price List.
BT Central Resilience
The level of resilience on the link between the Service Provider’s premises and the BT
network varies between BT Central bandwidth options as follows:


BT Central 2 Mbit/s - this has a single option of a single fibre through a single duct to the
Service Provider’s premises.
BT Central 10 Mbit/s and 34 Mbit/s - this has a standard resilience of a single fibre through a
single duct between BT's network and the Service Provider’s premises. An additional fibre


can be provided in the single duct or it can be routed to your premises through a second
duct at an additional cost as detailed in the BT Price List. This additional duct is subject to
site survey and can only be ordered in conjunction with a second fibre.
BT Central 155 Mbit/s - this has a standard resilience of dual fibres through a single duct
between BT"s network and the Service Provider’s premises. A second duct is available at an
additional cost, each duct containing a fibre. This is subject to site survey and costs will
depend on the work carried out.. Please use a CRF if you wish to order this facility.
BT Central 622 Mbit/s - this has a standard resilience of dual fibres through a single duct
between BT’s network and the Service Provider’s premises. A separate duct will be provided
where possible, subject to survey.
Please note:


BT Central products do not support the ability to route the individual fibres of a dual fibre
access to your premises from separate broadband PoP sites.
BT Central products do not support the ability for you to nominate the specific broadband
PoP sites that your BT Centrals are connected to. BT will normally connect BT Centrals to the
nearest broadband PoP site.
RADIUS server
The Service Provider is responsible for providing their own RADIUS server, connected to
BT’s NTE, to authenticate user logins and allocate IP addresses.
Further Information is available in SIN 329
RADIUS Accounting Data
BT Central supports RADIUS End User accounting data, at no charge, except for the
155Mbit/s L2TP variant and except for BT Central Plus. The accounting data will be
available via a data feed to the Service Provider’s RADIUS server. As well as stop and start
accounting data, the data will be refreshed every two hours to provide interim accounting
messages. Service providers also have the option to ask BT to turn on the extra RADIUS
traffic attributes 42, 43, 47 & 48.
Further Information is available in SIN 329.
RADIUS accounting data transfer attributes 42, 43, 47 and 48 have a level of accuracy
comparable with typical IP traffic measurement equipment. There are, however,
circumstances in which accounting packets and records may be lost. The traffic
measurements are therefore an approximate indication of the individual End User traffic.
Please request RADIUS End User accounting data using the BT Central CRF.
Domain Name Options
This is a service enabling Service Providers to map domain names to multiple BT Central
connections and provides a simple process for adding new BT Centrals.
There are three options; any combination of them is known as ‘many-to-many’.
One-to-one
The default option maps one domain name to one BT Central link.
Many-to-one
This option maps more than one domain name to a BT Central link. BT IPstream can support
up to ten domain names per BT Central, offering Service Providers more flexibility in
constructing and tailoring their End User services.
One-to-many
This option maps one domain name to a group of BT Centrals. End user sessions are
sequentially distributed over the Home Gateways and LTSs, offering a form of resilience that
falls short of true load balancing. If a BT Central is lost, End User sessions will be reestablished on one of the other BT Centrals in the group; when service resumes, Service
Provider can either force End User sessions to be re-established manually or allow them to
rebalance over time. A maximum of 100 Home Gateways or LTSs can be supported in a oneto-many group - for example 25 BT Central 155Mbit/s or 50 BT Central L2TP 155Mbit/s.
Recommendations
;BT strongly recommends that Service Providers create a group of BT Centrals with the same
bandwidth and supported simultaneous sessions. There have been issues with throughput and
contention where End Users are terminated on a group of BT centrals with different
bandwidths - for example BT Central 10Mbit/s and BT Central 34Mbit/s.
BT strongly recommends that Service Providers provide an additional two IP addresses. BT
will NAT the proxy RADIUS to those addresses, as this is more efficient with RADIUS
Packet Routing
BT will not support one-to-many groups of mixed services - for example ‘Classic’ and L2TP
If the Service Provider does not use dynamic IP addressing and the Address Pool is hosted on
the BT Home Gateway, BGP4 Routing must be used
BGP4 Routing Protocol will be part of the standard configuration of BT Home Gateways.
The BT Home Gateway router will be configured with a private AS number - AS65400 - to
be used with iBGP
BGP4 Routing Protocol is only available on BT Central 10Mbit/s and above products
Only BT hosted dynamic IP address pools are supported with a One-to-many group of BT
Central 2Mbit/s links.