EBC
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ELEMENT BASED CHARGING
Information for Operators
CONTENTS
Introduction
What Is Element Based Charging
Timescales
Retardation
Indirect Access, CPS and DQ118
Removed Switches
Other Published Files
EBC Systems
Exchange Types
Virtual Switch Locations (VSLs)
DMSU Pairing
Other Documentation
© British Telecommunications plc
Issue 1 October 2003
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INTRODUCTION
At the EBC Industry Workshop held by BT Wholesale on 26 September 2003
Operators requested more information on EBC. This document aims to
provide the requested information in an easy to understand form. At the
bottom of this document is another document, called EBC Guidance Notes.
This is held on the EBC web site. Any Operator wanting to access the EBC
web site can obtain a user identifier (user ID) and password by sending an
e-mail message to wsmf.ad-hoc.reports@bt.com
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WHAT IS ELEMENT BASED CHARGING
Element Based Charging (EBC) is a the wholesale charging methodology
which BT uses to charge Other Licensed Operators (OLOs) for their use of the
BT network. EBC charges are based on the theoretically smallest number of
BT exchanges, consistent with the topology of the BT network, an
interconnect call would pass through with a secondary factor being the
dogleg distance between these exchanges.
The published matrix shows the EBC charge band associated with a Point
Of Connect (POC), where a call enters the BT network, and a retarded
number range - where the call either terminates or exits the BT network. BT
then uses this charge band to derive how much an Operator should be
charged for using the BT network, on a per call basis.
Only certain types of call are subject to the EBC Pricing Methodology:
 Calls terminating on the BT network with a geographic UK destination,
including calls to numbers ported into BT
 Incoming calls (both geographic and non-geographic) transiting the BT
network en route to a third party including calls to ported numbers and
Targeted Transit calls
 Calls originating on the BT network to Operators’ Indirect Access, Carrier
Pre Select and Operator DQ118 services
© British Telecommunications plc
Issue 1 October 2003
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Transit calls (those from one Operator via the BT PSTN to another Operator)
attract a different set of EBC Charge Bands to non-transit calls passing
through the same number of switches.
In EBC, all geographic number portability prefixes and Operator nongeographic number portability prefixes1 are treated the same way as called
numbers (i.e. as though the prefix is part of the called number).
All other types of call (international, BT non-geographic services, Level ‘1’
numbers etc.) appear in a Non-EBC file, as these numbers are not charged
using the EBC matrix.
The EBC Matrix is built up from a snapshot of the network (numbering and
connectivity) on a quarterly basis; the resulting charge band list remains in
force for three months regardless of any changes to network connectivity or
numbering.
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TIME SCALES
The effective dates for the Matrix are the first calendar day of each quarter
(1 January, 1 April, 1 July and 1 October) with publication two weeks
before this. The snapshot of network data occurs about 1 month before the
effective date
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RETARDATION
A Charging Number String (CNS) as allocated by Oftel has retail charging
information associated with it. There are tens of thousands of such number
strings in use and so to reduce file sizes EBC employs “Number
Retardation”. A Retarded Number String contains the minimum number of
digits in a ‘phone number’ necessary to identify the switch or exchange
hosting the number range containing the 'phone number' and the
appropriate EBC Charge Band.
© British Telecommunications plc
Issue 1 October 2003
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Consider the following matrix for an OLO
POC
Retarded Number String
EBC Charge Band
4090285
0191505
528
4090285
019150
529
4090285
0191
525
As shown above, this significantly reduces the size of the EBC data files.
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INDIRECT ACCESS, CPS and DQ118
Charging data for BT originated calls to Operators’ IA, CPS and Operator
DQ118XXX services can be found in a separate “ia_cpsnnn.001” file.
Call records for BT originated Indirect Access traffic are not captured from
the POC but instead from the DLE where the BT customer originating the
Indirect Access call is connected. The charge covers the cost of the network
elements used from the originating DLE, identified from the CLI (GNP
import is catered for), to the agreed IA exit POC.
In order to calculate the EBC Charge Band for an Indirect Access call the
POC where the call is handed over to the Indirect Access Operator has to be
derived and this is shown in the last column of the “ia_cpsnnn.001” file.
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REMOVED SWITCHES
If an exchange has been removed from the network then the rows for that
switch will not appear in subsequent issues of EBC Matrix files.
Top of document
© British Telecommunications plc
Issue 1 October 2003
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OTHER PUBLISHED FILES
EBC files are published on the EBC Internet site at least two weeks before the
matrix becomes effective. A checksum is available on request to enable
Operators to confirm the data has been correctly downloaded.
The file set includes a file showing exchange name and NNI as well as a file
showing Charge Bands and their descriptions. A full list of the published
files can be found in the embedded document EBC Guidance Notes.
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EBC SYSTEMS
The core of the EBC system is a module, which uses BT exchange
connectivity data to construct a “matrix” showing the cheapest logical path
between each pair of BT exchanges. Connectivity in this context simply
means that one exchange can pass speech traffic direct to another. The
cheapest path is the one with the lowest number of exchanges and the
shortest total dogleg distance combination.
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EXCHANGE TYPES
There are several different types of exchange in the BT network and these
each have rules, regarding connectivity, number string associations, valid
traffic types etc. associated with them. These rules are reflected in EBC.
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VIRTUAL SWITCH LOCATIONS (VSLs)
VSLs are no longer allowed, but for any that have not yet been removed the
VSL data is provided to the EBC system on the basis of information provided
by the relevant Operator and as far as EBC is concerned affects the
definition of the EBC charge band for the “charging POC”. The BT call
© British Telecommunications plc
Issue 1 October 2003
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charging system will override the POC in the call record with the
“charging” POC and search for that charging POC in the EBC data; this
process must be emulated by the OLOs – no automatic data is provided by
the EBC system.
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DMSU PAIRING
Where an NGS DMSU has replaced a System X DMSU some routes may have
remained on the replaced System X DMSU. Operator connections have been
transferred to the NGS DMSU and the Operators informed that they will see
no difference in charging as a result.
In order for BT to meet its obligations, and not financially penalise the
Operator for the interim co-hosting of System X and NGS DMSUs route data
for the two switches is “merged”.
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OTHER DOCUMENTATION
EBC Guidance notes:
Top of document
© British Telecommunications plc
Issue 1 October 2003
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