Signaling Transfer Point (STP) Replacement

8 Aug

As telecommunications service providers worldwide navigate the uncharted waters of network migration from either circuit switched to VoIP/IMS or GSM/CDMA to LTE/EPC Diameter-based networks, they are encountering a major decision point. With manySignal Transfer Point (STP) vendors exiting the market or reaching End of Life/Support for their products—“What do I do with my SS7 Signaling Transfer Points?”

stp-replacement-questionsIn this post we will discuss important issues that need to be addressed in order to maintain the viability of the existing Signaling System No. 7 (SS7) Signaling infrastructure while migrating to Next-Generation Networks.

Since the start of deployment of the SS7 networks in the mid 1980s, there have been numerous vendors of Signaling Transfer Points (STP) including most switching equipment vendors and other specialized suppliers. With the maturity of the network, there has been consolidation and attrition in the STP market.

Today the number of STP suppliers has dwindled to 4 or 5 vendors, some of which are quite small. The attrition in the STP market and the need to maintain the integrity of the SS7 network is causing major concern to service providers.

These concerns/questions will be discussed in the remainder of this post.


As defined by Wikipedia — End-of-life (EOL) is a term used with respect to a product supplied to customers, indicating that the product is at the end of its useful lifetime. At this point, a vendor will no longer market, sell or sustain a particular product and may also be limiting or ending support for that product.

At the time when vendors make an End-of-Life announcement, service providers must ask themselves several questions:

  • Can I continue to use the existing STP equipment until I migrate to Next-Generation Networks (IMS or LTE/EPC/Diameter)?
  • How long will I have to maintain the existing SS7 network?
  • Given that this product is no longer a focus for my vendor, what happens to my ongoing support?

Major Upgrades

Some equipment vendors are announcing major equipment upgrades (that can be very costly) required for their customer to remain on support contracts. This is being driven by proprietor nature of the hardware platforms and the ability to supply required components, or simply the vendors desire to get the most revenues out of a mature and declining market.

When vendors announce these major upgrades, service providers are forced to answer the following questions:stp-replacement-question1

  • Should I implement the upgrades or can I run my network without support until I migrate to Next-Generation Networks (IMS or LTE/EPC/Diameter)?
  • Should I replace the existing STPs?
  • What is the Total Cost of Ownership for the replacement STP?

Ongoing Support for SS7/STP

Along with the end-of-life discussed earlier, ongoing support for the SS7 network and the associated STPs is a major concern for the service providers. These support issues are both hardware and software. Questions that arise for service providers regarding ongoing support should include:

  • Has my STP equipment vendor announced end of support?
  • Can I continue to run my network without vendor support?
  • Has my equipment vendor announced an upgrade program to remain on support contracts? If so, how much does it cost?

stp-replacement-question2Evolution to Diameter

The next issue to be addressed is the evolution to Next-Generation Networks (once the decision has been made to upgrade or replace the existing STPs). In order for the service providers to protect their investment by replacing their existing STPs, the STPs have to be able to evolve in providing signaling switching and routing for next-generation networks, i.e. STPs operating as Diameter routers.

Although the SS7 and Diameter-based networks do not typically intercommunicate (except in the case of roaming), Capital and Operational cost savings can be realized if the same platform can handle both SS7 and Diameter.

The questions that service providers need to answer regarding the protocol routing capabilities of the replacement STPs should include:

  • Does the replacement STP only support SS7?
  • Can Diameter Routing capabilities be implemented on the STP platform?


In the selection of replacement STPs, architectural issues have to be addressed as they have a direct impact on the cost of implementation and operations. Additionally, these architectural issues can insure that the platform selected provides evolution capabilities and thus does not “Dead End” the service provider in SS7 capabilities only.

  • IP Switching

One of the most important architectural issues to be addressed is the IP switching capability of the selected STP. If internal IP switching is not provided within the selected STP, external IP switches have to be installed, provisioned and maintained especially for the SS7-over-IP (SIGTRAN) deployment.

Questions that service providers need to answer regarding IP switching capabilities of the replacement STPs should include:stp-replacement-question3

  • Does the replacement STP have IP switching within the platform?
  • Does the replacement STP require external IP-switching equipment?

Protocol Routing Engine/Platform

Another important architectural issue to be considered in the selection of replacement STPs is whether or not the internal software design is based on universal protocol switching and routing concepts. These concepts can provide assurance to service providers that as new protocols are defined and implemented within the network, the switching equipment can evolve to meet the needs of Next- Generation Network requirements.

Questions that service providers need to answer regarding routing engines inherent within the STP platform should include:

  • Is the replacement STP designed around universal protocol routing concepts?
  • Is the routing capability of the STP dedicated solely to SS7?

Feature Compatibility

As service providers gain experience with SS7 routing over time, they define required routing capabilities to support their business needs. These specialized routing scenarios can be outside the standard routing capabilities based on:

  • Originating Point Codes (OPC)
  • Destination Point Codes (DPC)
  • Global Title Translations (GTT)

The replacement STPs should have the same routing features and be compatible with the ones that they are replacing.

stp-replacement-question5Ease of Migration STP to STP

After the decision has been made to replace the legacy STP, the next important issue to be resolved is the implementation of the new STPs. This causes concern regarding the ease of migration regarding the following:

  • Implementation without disrupting network services.
  • Implementation without impacting interconnected networks.
  • Cutover without impacting the scarce resource of Point Codes.

Cap and Evolve

One of the key strategies in the replacement of STPs is to co-locate the replacement STPs with the existing STPs and to efficiently migrate the services in a step-by-step approach to the new STPs. This Cap and Evolve strategy allows new growth to be implemented in the replacement STPs. Over time, migrating existing SS7 connectivity to the replacement STPs, thus collapsing the legacy STPs in a controlled and step-by-step approach.

Questions service providers need to answer about the migration strategy of the replacement STP vendor should include:

  • Is the replacement STP implementation strategy step-by-step?
  • Is the replacement STP implementation strategy a “Flash cut?”

Cutover Tools

When service providers and STP vendors start the process of replacing existing STPs, it is of the utmost importance that efficient cutover tools are used. These tools reduce the impact on both interconnected networks and subtending switches.

Questions service providers have to resolve about the cutover tools available should include:stp-replacement-question6

  • Does the replacement STP vendor have STP cutover tools?
  • Do the cutover tools eliminate issues involved with Point Codes?

Simplicity of Installation

Some companies decide to perform the installation of the replacement STP with little or no assistance from the STP vendor, depending on the breadth of experience and the desired involvement of the service provider. The level of complexity of installation determines whether this can be accomplished in an efficient manner by the service provider.

Questions service providers need to address about the installation of the replacement STP should include:

  • Can the service provider install the replacement STP?
  • Does the installation require ‘out of the ordinary’ level of expertise?

Web-based Interface

The implementation of any new technology within the telecommunications network requires that the support and operations personnel, as well as the service provider, be capable of ongoing support and maintenance. The inclusion of a web-based intuitive user interface reduces the training and effort required for the replacement STPs.

stp-replacement-question10Questions service providers need answered about the user interface of the replacement STP should include:

  • Does the replacement STP have a web-based user interface?
  • Is the web-based interface intuitive and easy to use?
  • Does the replacement STP have a command line interface for “power users?”

Vast Network Routing Experience

The selection of a replacement STP and the associated vendor should be based on both the capabilities of the equipment and the experience level of the vendor. The experience level of the vendor is tantamount to the success of the replacement project.

Questions service providers need to address about the experience level of the replacement STP vendor should include:

  • What is the experience level of the vendor?
  • Is the experience related to wireless or wireline, or both?
  • Is this experience US national or international, or both?
  • Is telecommunications signaling the vendors primary focus?

Decision/Implementation Timing

Another important aspect of STP replacement is the timing of the decision to replace the existing STPs relative to the actual installation and implementation of the replacement STP. From the time the decision to replace existing STP is made until the actual turn-up of the STPs is accomplished can range from 6 months to well over a year, dependent on the processes used for vendor selection and the complexity of the SS7 network.

Questions service providers need to address regarding the timing of STP replacement process:stp-replacement-question9

  • Are we going to use a request for proposal process with several prospective vendors?
  • How long does the request for proposal process take?
  • Are a short list and trials going to be part of the process?
  • After the conclusion of any associated trials, what is the installation, implementation and turn-up schedule?

Future Proof

The answers to the questions provided in this post will determine whether the replacement of legacy STPs is simply a replacement strategy or if this strategy is truly a path to Next-Generation Networks. These decisions can lead to an efficient implementation of replacement STPs, thus supporting the most robust, long lived, feature rich signaling protocol in the history of telecommunications, while providing an evolutionary path to the networks of the future.



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