Optimizing softswitches: international versus national long distance

The similarities between softswitches optimized for international long distance (ILD) and those optimized for national long distance (NLD) are strong and fundamental. Both are softswitches and therefore have clean, layered architectures in which call control is detached from transport and transport is offloaded for handling by media gateways. Both types of softswitches are built for long distance, and therefore both must be able to control at least medium-scale, medium-density trunking media gateways. Both need to support network services such as calling card, and both need to integrate with public switched telephone network (PSTN) signaling. But the similarities basically stop there.

Softswitches optimized for ILD support sophisticated routing capabilities including time and date-based routing, source-based routing, priority (least cost) routing, intra- and inter-domain routing, private and global numbering plans, forwarding on busy/ring-no-answer, online dynamically modifiable routing, and resource availability routing. These capabilities are needed for managing complex international routes and networks composed of multiple domains operated by different carriers. They are also needed to build the features of global services such as VoIP virtual private networks and global call centers.

Softswitches optimized for ILD also need to support the special requirements of carrier interconnect services and wholesale international exchange carriers. These requirements include minimizing post dial delay (PDD) by dynamically updating routing tables based on resource availability indicator (RAI) information. In addition, call routing can begin as soon as the caller enters the first few digits. ILD-optimized softswitches must also support a very large number of country-specific signaling system 7 (SS7) variants, due to the nature of international traffic. ILD-optimized softswitches need to support distance insensitive services such as VOIP private networks, which need abbreviated numbering plans and closed user groups for all calls, avoiding PSTN toll charges in the process. Because ILD VoIP networks usually interconnect a large number of different carriers' closed and managed IP networks and sometimes unmanaged networks including the open Internet, security is essential - both in terms of VOIP access, authentication and authorization, and IP firewalls and NAT. And because international networks are generally heterogeneous interoperability between vendors for a large number of different protocols is an absolute must.

NLD-optimized softswitches are simpler, less "intelligent," but more "powerful" as measured in call attempts per second (CAPS) and/or busy hour call attempts (BHCA). CAPS and BHCA are typically four to ten times higher in NLD vs. ILD softswitches. This "power" is used to control large-scale, high-density trunking media gateways that support four to ten times the number of T1/E1 connections per chassis.

Routing and signaling for NLD-optimized softswitches are relatively simple since the networks are deployed and managed by a single carrier using a single vendor's equipment. Only one flavor of SS7 is needed for a particular nation, whereas vendors of ILD-optimized softswitches invest heavily in supporting and certifying dozens of national SS7 variants. Vendors focusing on NLD softswitches generally support and certify SS7 for only those nations in which they power national long distance networks, and only when they sell equipment into that country.

Since the differences between ILD-optimized and NLD-optimized softswitches may boil down to "brains" versus "brawn" and multi-national versus country-specific signaling and services, the natural questions are could, should and will they be combined? The answer to all three questions is probably "yes," but it won't happen overnight. On the one hand, softswitches are "soft," meaning that they are software running on standard platforms, controlling various types of hardware-based gateways. Since the protocols for controlling the gateways (H.323) and media gateways (MGCP/MEGACO) are standardized, ILD softswitches can be simply scaled up to support the large-scale, high-density media gateways supported by the NLD softwitches. Furthermore, their software can be enhanced to support integration with country-specific IN platforms.

On the other side of the equation, the software running NLD softswitches can be enhanced to support the sophisticated routing capabilities of ILD softswitches, from which global hosted services and international long distance exchange carrier features can be built.

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But the reason that this may not happen quickly, even though it is "only software", relates to the differences in the core competencies and experience required by vendors, in order for them to migrate from an ILD focus to an NLD focus, or vice versa. Supporting and certifying numerous national variants of SS7 is very demanding, requiring a large investment and enough deployments spread out across the world so as to provide the experience, shorten the learning curve and make the investment worthwhile. Similarly, international integration is complex, and although vendors focusing on NLD softswitches need only develop the competence and software for each new country as they sell into it, such efforts are costly and require very specialized skills. So while softswitches could be designed to excel at both ILD and NLD, they require strong vendors with sufficient skills to master both sets of requirements. Both time and some market consolidation are required to make the investment in this effort worthwhile.