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October 8. 1997

Mr Richard Metzger. Jr.

Acting Chief: Common Carrier Bureau

1919 M Street. N.W. Room 500

Washington, D.C. 20036

Dear Mr. Metzger:

The undersigned, all members of the Number Pooling Subcommittee of the Illinois Number Portability Workshop, are assessing the feasibility and practicality of implementing number pooling to conserve numbering resources in the 847 area code in Chicago. The purpose of this letter is to communicate our findings, the status of our progress to date, and our plan for moving forward. Our plan is rooted in a proposal that we believe could become the basis for number pooling. The number pooling method we propose to test, while promising, would stretch the existing capabilities of number administration systems and LNP network routing databases.

Under the number pooling proposal explored by the Subcommittee, local exchange carriers would share central office codes (NXXs) within a rate center. Instead of allocating an entire NXX of 10,000 numbers as is the current practice, carriers would receive numbers in blocks of 1.000 identified by NXX-X. This would enable up to ten carriers to share a single central office code, significantly reducing demand for these codes and permitting more efficient utilization of numbering resources by avoiding the designation of large blocks of unused numbers. The sharing of NXXs by more than one carrier is made possible through the use of the permanent number portability solution mandated by the FCC, the Location Routing Number (LRN) methodology. Hence, this proposal is called NXX-X/LRN. (1)

Today, when an NXX is allotted to a carrier, calls to numbers within this NXX are terminated in the carrier's network. This carrier, the code holder, provides vacant number treatment when calls are made to unassigned numbers. Under NXX-X/LRN, pooled numbers could be handled in one of two ways: port-on-demand or pre-port. In a "port-on-demand" scenario, each number in the l,000s block would be ported only when the block holder assigns and activates a particular number for a customer, and the code holder would continue to provide vacant number treatment. A "pre-port" methodology would port an entire block of 1,000 numbers to the block holder's network at the time the block is allotted. The block holder would then assign and activate particular numbers in the block for its customers. In this scenario, vacant number treatment would be provided by the block holder.


(1) We acknowledge that there are certain constraints with the use of NXX-X/LRN, most significantly that number pooling would initially be limited to only wireline carriers whose networks are LRN-capable. This means that wireless and other non-LRN-capable carriers would still need to be assigned whole NXXs to ensure that numbering resources are available to all carriers in an equitable manner. When wireless carriers implement LRN in mid-1999 according to the Commission s rules. and as number portability implementation grows. more carriers will participate in number pooling, and it will be applied in more switches. This will increase its effectiveness in conserving numbers.


The Subcommittee has agreed that the pre-port option for NXX-X/LRN is workable if the industry can address limitations on service control point (SCP) capacity, as discussed below. The pre-port option has the advantage of permitting each carrier the greatest control over the numbers it receives for assignment to its customers. and most closely resembles a carrier's current number administration process in that numbers are assigned to customers from the carrier's own inventory of unassigned numbers. In addition. the pre-port option simplifies the porting of pooled numbers because the NXX-X block is ported all at once rather than individually each time a number is assigned to a customer.

However, number pooling, if implemented using existing local number portability (LNP) processes and systems, would strain number administration systems and LNP network routing databases. Carriers would need to implement number administration processes, which could potentially be manual. to accommodate numbers in blocks of 1,000, and processing and storage requirements for service management systems ("SMS") for LNP would increase significantly because each regional SMS would be required to process and store records for both ported numbers and pooled numbers. (2)

The most significant issue affecting the pre-port option is that of SCP (carrier routing database) capacity. As LNP is currently configured, pooled numbers would be down loaded from the regional SMS to SCPs and each pooled number would be represented by an individual record. If the pre-port NXX-X/LRN solution were applied in multiple NPAs, the required SCP storage capacity could eventually exceed tens of millions of records, an amount which exceeds the record storage capacity of many carriers' networks. Once SCP capacity limits were reached, carriers would be unable to port additional numbers for customers who sought to switch to another carrier.

The Subcommittee is considering enhancements to the SMS and SCPs that would permit blocks of pooled numbers to be represented by ranges rather than the individual numbers themselves. This proposal would permit 1,000-number NXX-X blocks to be represented by a single record rather than 1,000 records, alleviating processing and capacity concerns in both the SMS and carrier SCPs. However, it will take some time to design and implement such enhancements, and these changes may not be available when capacity limits are reached. Therefore, until these concerns can be resolved, the Subcommittee believes that the FCC and State Commissions must consider the SCP capacity issue and must monitor and control implementation of NXX-X/LRN number pooling.

Despite the constraints described above, the Subcommittee believes that there is significant merit in proceeding with a trial of pre-port-based NXX-X/LRN number pooling in the Chicago area limited to the 847 area code. The proposed trial will provide an important reaming experience and contribute greatly to future efforts to implement number pooling.


(2) The NANC Architecture and Administrative Plan for LNP, approved by the FCC in its Second Report and Order in CC Docket No. 95-1 16 released August 18. 1997 (FCC 97-289), limits the SMS database to only ported numbers and the associated routing and service provider information."



ICC Commission Staff



Citizens Utility Board






Cc: Federal Communications Commission

Ms. Geraldine Matise, Chief Network Services Division

Ms. Marian R. Gordan, Designated Federal Officer to the NANC

Ms. Erin Duffy Attorney

Mr. Andre H. Rausch, Engineer

Illinois Commerce Commission

Mr. Charles Fisher, Executive Director