Least Cost Routing Challenges

Optimize Your VoIP Network By Managing Routing Decisions

Not too long ago, optimizing least cost routing was a relatively straight-forward exercise that could be managed part time by an industrious billing or switch technician. This is no longer the case.


The Challenges

Routing Table Size

Routing Table Size

Seven digit routing based on 1000 block partitions is more complicated than routing on six digit NPA-NXX blocks. In the Local Exchange Routing Guide (LERG) there are 166,431 six digit NPA-NXX dial codes. In contrast, there are 644,327 dial codes when routing based on seven digit one thousand blocks. 


In telephone routing tables, a dial code matched with a destination (IP address or trunk group) is called a translation. Most least cost routing tables have an average of three destinations per dial code. This means that a basic optimized least cost routing tables for domestic US routing can have more than one and half million translations. Some TransNexus customers have 50 million translations in their routing table. 



Jurisdictional Routing

For a service provider to optimize their least cost routing, they must have two routing tables, one for intra-state calls and a second for inter-state call. Jurisdictional routing is determined by the ANI (Automatic Number Identification), or telephone number, of the calling party. With VoIP calls, it is common for the ANI to be an invalid value,which are rated at the higher intra-state rate if they are completed. In addition, most major carriers will block calls that do not have a valid ANI. However, some service providers will accept calls with an invalid ANI so this creates an optimization for a third least cost routing table. One for inter-state, one for intra-state and a third for calls with invalid ANIs.


Deciphering Rates

Deciphering Rates by LATA, OCN and Tier

Least cost routing is concerned with analyzing dial codes and the rates carriers charge to complete calls to those dial codes. Unfortunately, most carriers to not quote rates for US termination by dial code. Instead they quotes rate in terms of OCN, LATA and Tier.


Technicians must normalize carrier rates from OCN, LATA and Tier to E.164 dial codes. Carriers often have six to eight rate tiers per LATA. Tiers are not standard and every carrier’s tier structure is different. Manually normalizing carrier rates using the LERG is too big a task for even the most industrious technician.


Number Portability Correction

Number Portability Correction

Today there are 197 million ported telephone numbers in North America. TransNexus customers report that 40% of their calls are to ported telephone numbers. This development has a dramatic impact on least cost routing. If least cost routing is based on the dialed telephone number, up to 40% of all calls will not be routed to the lowest cost provider.


The Solution

Optimized least cost routing requires software that can handle the complications of today’s VoIP industry.  With TransNexus solutions, you can easily copy and paste rate provisioning from carrier rate plans, Support up to 100,000,000 different VoIP routes, base LCR tables on inter-state rates, intra-state rates and customized local calling areas, and convert rate plans based on LATAs, OCNs and Tiers into a routing table and rate plans based on NPA-NXX-X breakouts.


TransNexus Products

NexOSS LogoNexOSS provides VoIP operators with an easy to use web interface for provisioning routes, rates, number translation rules and monitoring traffic analysis and billing reports.  View Product Details


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Case Studies

BroadRiver Communication Corp


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