National Numbering Plan: The Power of 10 Digits

The elongated inning of the existing National Numbering Plan is approaching
an inevitable end. The plan, which was designed in 1965 and revised in 1990-91,
served the country well for 35 long years. But the communication revolution has
thrown up a host of compelling new services that are pressing too hard for the
introduction of new codes and numbers. So the existing numbering scheme, which
was designed for a monopoly operator, looks exhausted and calls for immediate
replacement. Any delay will lead to violations of the ground rules of the plan,
to accommodate new requirements. This will cause complexity in network
operations and add to confusion among users.

The TRAI Proposal

Telecom Regulatory Authority of India (TRAI) had envisaged the situation well in
advance and suggested a modified numbering plan on 24 July 1998. But while the
recommended plan may take care of the present crisis, it will fall short of
expectations within a short period of time. A discussion on the pros and cons of
the TRAI-proposed plan is still on with major operators. In the mean time, in
the last three years, the unprecedented growth of mobile and Internet users has
challenged the long-term viability of the plan. A close look shows that TRAI’s
plan is a compromise solution, which provides some openness to the existing
numbering plan, while maintaining the existing network hierarchy.

As against the existing nine-digit PSTN format AB CDE XXXX, TRAI has proposed
the ten-digit format N ABCDE XXXX (See Table 1). The proposal has reserved an N
digit 2 to 5 for basic service operators and used a linked number plan. This has
neither opened up enough numbers to last for future nor is easy to adopt. The
reasons why TRAI’s numbering plan is not likely to take off are:

• Conservative approach to change
  the basic service number plan hampered the value proposition of the plan

• The plan does not simplify the
  network structure or call-handling process, as it has followed the existing
  hierarchy

• It has not opened up enough
  numbers for future; hence, it has not generated enough interest among
  operators to take up the challenge of implementation

• It has not considered some of the
  upcoming services like VoIP, which will be important for our country due
  their affordability

As the change in the numbering plan in a national network with millions of
customers is a major exercise, it is worth reviewing closely the proposed
numbering plan of TRAI.

National Perspective

Historically, in all our plans, we have under-estimated the potential and
need of the population. Many of our plans did not survive their life-cycles due
to under-planning. The present numbering plan never considered penetration of
communication to masses. Hence, the available numbers are inadequate. The
telephone-based numbering plan and trunking plan are of miniscule size in
comparison to the future requirement and are not flexible enough for dramatic
expansion.

Also, over-utilization of the present number plan has created certain
anomalies in the network. New plan should aim at bringing uniformity and
eliminating undue advantages of incumbent operators. The new plan should be
capable of handling enough unique numbers to accommodate every individual of the
country for the next 50 years.

Due to our large population, we need many more numbers than any of the
developed countries. The government plans to provide 150 million connections by
2010. Our problem is more complicated than any of the developed countries and
therefore borrowed solutions from other countries will not be sustainable.

India is a vast country with a variety of vintage networks. Any changes in
this heterogeneous network will be difficult, time-consuming and mostly manual.
However, in most cases, the network is voice-centric, hierarchical and follows a
uniform tariff structure.

Changing the numbering plan for a small customer base is more practical and
cost-effective today than in future. As the change in numbering plan is
inevitable to support the expected explosion of customer base, it will be
comparatively simpler to do it at this stage.

Modify for Growth

TRAI proposed a 10-digit linked numbering plan, applicable to all telecom
services. For STD and ISD calls, as well as for carrier selection, one has to
dial extra prefixes before these 10 digits.

TRAI proposed N ABCDE XXXX as the standard number length, to be used by all
telecom users of the country.

We agree with TRAI to adopt the 10-digit common numbering scheme. However, we
have suggested a different way of usage of this scheme, as NABC DEXXXX.

If no restriction is imposed, the scheme may accommodate 1x1010 — 1
numbers, ie 10 billion numbers.

At present, India has a population of more than one billion. In the next 50
years, it is expected that the country’s population will be two billion (with
2 percent simple growth). To provide a unique number as communication identity
for each Indian, we need to design a scheme which can support at least three
times of 2 billion, i.e. 6 billion numbers.

N being the most significant number in the scheme, loss of one digit in N
means loss of 1 billion numbers.

It is suggested that N should be used in the most open manner and as far as
possible it should not be used for identification purposes. This is important to
keep the number length to 10 digits. Otherwise in the near future, we may need
to proceed to an 11-digit scheme.

New plan allows utilization of all 10 digits. Billions of numbers are saved
as the most significant digit N is neither used as access code nor as service
pointer.

We suggest to allot N = 2 to 5 to all access providers, (as defined by NTP’99).
This will provide for 4 billion numbers to access providers. Even with one-third
utilization of 4 billion numbers, we may sustain for a long time.

As N=6 and N=9 are kept spare, 2 billion numbers will be available for future
allotment. Hence, the scheme is meeting the requirement of 6 billion numbers.

By avoiding the use of the most significant digits NABC for identification of
services or addressing level-1 and level-2 taxes, wastage of a big chunk of
numbers can be avoided. A uniform 10-digit numbering scheme will be available
for all end users and no prefix will be needed to dial any number within the
country.

Ample Support for Future Services

To support convergence of services, various equipment capable of handling
specific protocol will be introduced as new elements in the network along with
existing voice switches. These elements and switches, which will handle various
intra-operator, inter-operator and inter-service traffic, may be called nodes of
the network.

A node may be a transit exchange; IP switch or a high-end router used in
network to handle inter-operator traffic, which includes voice, data, voice over
IP and multimedia traffic.

It is recommended that nodes of different services and of different operators
be interconnected through a suitable interconnect exchange for network
simplicity and for the ease of inter-operator protocol handling.

In NABC DEXXXX scheme, NABC is recommended as the address of any node. We
further recommend NABC to be allotted as signaling point code of the node. Hence
to direct a call to a node, no translation or digit-by-digit analysis is needed.

The most significant fourth digit of the national dialing code shall be the
SPC of the called node. SPC is an unique address of a node in a complex network.

A node defined above may support 1 million numbers. These million numbers may
be sub-divided to many network elements connected to the node. Network hierarchy
below the node may be as per the specific service requirement.

An access provider may have one or more nodes. They are to be interconnected
and to be in the same license area. Calls between nodes of the same operator in
the same service area are expected to be handled by operator-owned/leased
interconnect links or may be routed through interconnect exchange of SSA.

Addressing the Nodes

By using NABC, we can address 9,999 nodes. As N=0, 1, 7 and 8 are fully or
partly allotted for other purposes (See Allocation of ‘N’ table), usable
address for nodes will be 5,999.

These numbers are to be allotted to access providers (defined in NTP ’99),
without wasting any series for special identification. Any access provider will
get a minimum bunch of 1 million numbers for a node. The million numbers may be
subdivided into smaller exchanges, according to the need of the network. At
present, India has less than 400 Level-1 and Level-2 TAXs, a few tandem
exchanges and about 100 MSCs of cellular operators working as inter-operator
transit exchanges. Even after considering multiple operators in every service,
5,999 nodes with 6 billion numbers will be there for access service providers.

It is highly recommended that Level 1 and Level 2 TAXs be replaced by or
upgraded to interconnect exchanges, with multi-protocol handling capability.
NLDOs will collect/deliver the calls from or to interconnect exchanges and
deploy only one or two inter-circle nodes in a circle. The interconnect
exchanges and inter-circle NLDO nodes, though critical transit points of the
network, will not be identified by subscriber-dialed numbers, as they are
neither the originating nor destination nodes of the call. Hence, SPCs of these
transit nodes should be different and are not addressed by the NABC part of any
number starting with N = 2,3,4,5,6 or 9. Hence, 6 billion numbers specified for
access providers are untouched.

For Maximum Utilization...

Some simple measures can be effective in increasing the addressing potential of
the TRAI-proposed numbering scheme. Let’s look at some problem areas and the
possible solutions.

Problem #1: Significant digits

Whenever we use the most significant or subsequently higher order digits for
specific identification purpose, we lose a huge chunk of precious numbers. By
allotting N=1 for emergency and special dialing numbers, for example, we loose 1
billion numbers out of 10 billion numbers of the 10-digit numbering scheme.

Wastage is also due to region-wise, circle-wise and LDCA/SDCA-based
divisions. Our network is at present hierarchically divided into regions,
circles, LDCAs, and SDCAs. A series of numbers are allotted to them. Numbers in
different significant positions are used to identify each stage of network
hierarchy. Number analysis is needed in each stage to physically route the call.

Solution: Service identification through significant numbers is to be
avoided as far as possible.

Problem #2: Allotment

Allotment of 92, 93, 94 and 95 to mobile operators in the TRAI proposal
theoretically delivers 400 million numbers for cellular operation. TRAI proposes
to use ABC as MSC address. Then only it will allow 400 MSCs in the network each
of 1 million capacity ie 400 million numbers. This is almost in line with our
proposal.

Solution: All access providers should be grouped
together and a common pool of number be allotted. Each operator should be
provided with a minimum of 1 million numbers, without any discrimination. No
prefix should be used for service identification, and service providers should
be monitored for optimal utilization of all the million numbers allotted.

Problem #3: Number of digits

Let us take an example of two STD calls made to two adjacent SSAs, namely,
Delhi and Gurgaon, from Ahmedabad.

In the call to Delhi, where 011 MNP XXXX has been dialed by
Ahmedabad subscriber (011 is STD code, MNP is Delhi’s local exchange identity
and XXXX is the end-user identity in that exchange). On the other hand, in the
call to Gurgaon, 0124 MNP XXXX has been dialed (0124 is STD code of Gurgaon, MNP
is Gurgaon’s local exchange identity and XXXX is the user identity in that
exchange).

The number-length of both the calls are different–10 digits
for Delhi and 11 digits for Gurgaon. This is because STD codes are of different
lengths–011 for Delhi and 0124 for Gurgaon.

Solution: The suggested 10-digit format will remove
this disparity.

Advantages of New Scheme

The uniform 10-digit national numbering scheme will solve ambiguities of
non-uniform number length used for local as well as long-distance calls.

Complexity of number analysis and dropping and addition of
digits will be eliminated, thereby increasing call-handling efficiency and ease
in database maintenance.

In the present scenario, up to the four significant digits
get blocked to identify 320 Level I and Level II TAXs to address 7,500 STD
codes, thus causing huge wastage of numbers. The number availability in TRAI
proposal is restricted to 500 million for basic and 500 million for cellular and
other services. In contrast, the new proposal is capable of allotting 6 billion
numbers for access providers even after fulfilling number requirements for other
services.

The manual procedures of database maintenance in different
TAX exchanges for digit analysis and addition or deletion of digits for route
selection is a serious bottleneck and creates immense customer dissatisfaction.
In the new proposal, call-routing database should preferably be controlled
through a centralized NMS.

However, it is not easy to implement the suggested changes in
a very short span of time across the country. A better approach will be to fully
adopt these changes in all new-generation electronic exchanges. For older
exchanges, a separate migration plan has to be worked out. And for convenience
of migration, both the plans may have to work simultaneously for some time.

Amitabh Mukhopadhyaya chief technical officer Fascel
(Gujarat)