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Featurenet is the UK managed voice network offering from
British Telecom. There are two types of Featurenet Service. These are Featurenet 1000
which is a VPN service and Featurenet 5000 which is a combined centrex and VPN based
service. The complexity of the tariffing structures for Featurenet can make an analysis of
the financial benefits of the services a daunting task. The methods of applying Westplan
to the analyse of VPN networks are described in the Westplan User Guide. This paper
discusses the differences between Featurenet and conventional VPN networks, and the ways
in which the use of Westplan can be modified to take account of these differences. |
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| Description of Featurenet |
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Featurenet is a managed network offered by BT in the UK.
Customers connecting to Featurenet can choose between two service offerings. |
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Featurenet 1000 is a VPN network which, as described in
Chapter 2 of the Westplan User Guide, is a modern alternative to private voice networking.
VPN requires only a single group of trunks to be connected to each PABX. The VPN switches
the calls based on the dialled digits offered and so alleviates the requirement for tandem
switching in a private network resulting in a saving on PABX hardware costs. The
connection of smaller sites whose connection to a traditional private network could not be
justified can often become financially viable using VPN. |
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Featurenet 5000 is a centrex solution. Customers connecting to
Featurenet 5000 do not have PABXs installed in their buildings. Their telephones are
connected directly to Featurenet public exchanges via concentrating devices called Small
Remote Units. All switching, even desk to desk calls within the same building, is achieved
using the serving Featurenet public exchange. The use of Featurenet 5000 avoids the large
capital investment required when purchasing PABXs and offers an upgrade path to Voice Mail
and ACD, all charged on a revenue basis. Featurenet 5000 customers are also offered desk
to desk dialling between their offices using a dial plan with unique site codes. This
network is very similar in nature to VPN. |
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To appreciate the Featurenet tariffing
options, the two types of calls which can be offered to a VPN network should be
understood: |
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These are calls made between two locations which are both
connected to a VPN network. |
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These are calls which are made from locations connected to a
VPN network and whose destinations are sites not connected to a VPN network. |
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In addition, there are two main tariffing options associated
with Featurenet: |
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This is the charging option adopted by most VPN network
providers. Charges are applied to both on-net and off-net calls. Both charges are usually
lower than the equivalent PSTN costs and on-net calls are always lower in cost than
off-net calls. |
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With National Networking, links are installed WITHIN the VPN
network for the customer's exclusive use. Distance related rental charges are incurred for
these National Networking Channels (NNCs). On-net calls are carried using these NNCs and
are free of charge. Charges are made for off-net calls and on-net calls which overflow
from NNCs. Network wide features such as Calling Line Identity and Call Back When Free
require National Networking. |
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| Applying Westplan to Featurenet |
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Featurenet 5000
with Usage Based Charging
With this combination, there are no PABXs installed and no
National Networking Channels. Westplan cannot be used to analyse such installations.
Featurenet 5000 with National
Networking
Westplan can be used to design National Networking Channels
(NNCs). The steps required to set up a project for this type of analysis are detailed
below. |
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| Sites configured in network drawings |
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One site should be entered for each Featurenet 5000 site. The
sites actually represent the Featurenet public exchanges (DMS). Each site should have the
following properties:
- Analogue private circuits should be enabled.
- Digital private circuits should be disabled.
- NNCs can be engineered to allow peak calls to overflow to
off-net and so save money on NNC rental. The disadvantage of this strategy is that
overflowed calls do not allow the passing of network facilities such as Calling Line
Identity and Call Back When Free. To allow overflow, enable PSTN overflow at each site.
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The annual rental charges for NNCs between each site should be
entered in this table. This information should be available from BT account
representatives. |
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The per minute charges for off-net calls should be entered
into this table. This is only required if overflow has been enabled (see Sites
configured in network drawings). |
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Network traffic between each Featurenet site should be entered
into this table. If these figures are not available, then reasonable estimates should be
made from your understanding of the business for which you are designing the network. |
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Having set a new project up in this way, new networks can be
set up within that project to analyse different NNC configurations. Links should be added
in the usual way, each link representing a NNC link between two Featurenet exchanges. When
a network has been entered, it should be optimised using the Optimum network option on the
Networks menu. This will change the NNCs to their optimum number of trunks. Returning to
the Networks Index will show all defined networks; the lowest cost network will be
displayed in blue. When studying the cost summary,
some figures have slightly different meanings than they do when analysing private voice
networks:
- Private circuit costs - These are the rental costs
associated with National Networking Channels
- PSTN costs - These are the off-net call charges for calls
which have overflowed from NNCs
Featurenet 1000 with Usage Based
Charging
Westplan can be used to design the access links to the VPN
network. Featurenet 1000 with Usage Based Charging is very similar to other vendors' VPN
offerings. In addition to the network locations, an additional site should be added to
represent the VPN network.
The costs of circuits from this site to the network
locations should reflect the monthly cost of Featurenet 1000 access lines. The traffic
figures to and from the VPN site should be zero as the VPN network effectively acts as a
tandem switch and does not generate or receive traffic.
Featurenet 1000 with National
Networking
Westplan can be used to design access links and National
Networking Channels (NNCs). As there are two networks involved (end sites / VPN and NNCs),
each Featurenet site needs to be represented by two sites in the Westplan Sites Table. The
first site represents the site where the PABXs are installed and the second site
represents the Featurenet public exchange (DMS). The steps required to set up a project
for this type of analysis are detailed below. |
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| Sites configured in network drawings |
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Two sites should be entered for each Featurenet 1000 site.
Imagine that there are four sites connected to Featurenet 1000. Create four new sites
called A, B, C and D; these represent the end sites with PABXs installed. Then, create
four additional sites called VA, VB, VC and VD; these represent the Featurenet exchanges
between which NNCs are installed. Each end site
(A..D) should have the following properties:
- Analogue private circuits should be enabled.
- Digital private circuits should be enabled.
- PSTN overflow should be disabled.
Each VPN exchange site (VA..VD) should have the following
properties:
- Analogue private circuits should be enabled.
- Digital private circuits should be disabled.
- NNCs can be engineered to allow peak calls to overflow to
off-net and so save money on NNC rental. The disadvantage of this strategy is that
overflowed calls do not allow the passing of network facilities such as Calling Line
Identity and Call Back When Free. To allow overflow, enable PSTN overflow at each
Featurenet exchange site.
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Two types of line rentals should be entered in this table:
- Enter rentals for VPN access lines between end sites and
their Featurenet exchanges (A to VA, B to VB etc).
- Enter rentals for NNC circuits between each combination of
Featurenet exchange sites (VA..VD).
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The per minute charges for off-net calls should be entered
into this table. This is only required if overflow has been enabled (see Sites Table). |
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Network traffic between each Featurenet end site should be
entered into this table (A to B, A to C etc). If these figures are not available, then
reasonable estimates should be made from your understanding of the business for which you
are designing the network. In addition, Featurenet may be used for off-net calling as a
cheaper alternative to PSTN. Traffic relating to these calls should be entered in the
Traffic Table from each end site to its corresponding Featurenet exchange site (A to VA, B
to VB etc.). |
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Having defined a new project up in this way, new networks can
be set up within that project to analyse different NNC configurations. Create the first
network with links between each end site and its associated Featurenet exchange (A to VA,
B to VB etc.). These links represent the VPN access circuits and with this type of project
can only be analogue lines. This is because entry of digital lines is only allowed in
multiples of 24 or 30. If digital lines are to be analysed, the costs per channel should
be entered into the Analogue PW Costs Table and the lines should be drawn on the network
as analogue. Conventional links can also be added between end sites if required. Links should be added between the Featurenet exchanges in the usual
way, each link representing an NNC between two Featurenet exchanges. When a network has
been entered, it should be optimised using the Optimum network option on the Networks
menu. This will change the NNCs and access circuits to their optimum number of trunks.
Because only analogue lines can be entered into these drawings, in this mode, Westplan
cannot be used to work out the break-even point between providing analogue and digital
access lines. VPN analysis in its usual form (see Featurenet 5000 with National
Networking) can make these calculations.
When studying the cost summary, some figures have slightly
different meanings than they do when analysing private voice networks:
- Private circuit costs - These are the rental costs
associated with National Networking Channels and VPN access links.
- PSTN costs - These are the off-net call charges for calls to
other Featurenet end sites which have overflowed from NNCs
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Westplan is
a Windows 95 / 98 / NT4 voice network modelling tool which can be used to simplify the
analysis and design of private voice networks and VPN. |
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This document has offered a brief
introduction to Featurenet, and demonstrated Westplan's ability to analyse Featurenet
customer networks. If you have any questions, please send
us an email. Why not try
our Telecom Design Forum? It is an interactive newsgroup
which you can use to exchange ideas about telecommunications design.
Return
to the technical document index
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| This
document should not be viewed as a consultative
document. It is the readers responsibility to
ensure that the most appropriate
telecommunications strategy is applied to his or
her business. No liability is accepted by Westbay
Engineers Ltd. for omission or error. |
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| Last modified: 05 July 1999 |
Copyright © 1999. All rights reserved. |
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