Edge STP

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An edge STP is an IP-SS7 hybrid network element that supports the transition of telecommunications signaling from the traditional common channel signaling approach to next generation IP-based signaling. It marries the old network architecture to new network interconnections, subnetworks, and service applications. The edge STP component is based on the proven concepts of the signaling transfer point (STP) and the SIGTRAN signaling gateway (SG), and includes capabilities and concepts derived from the world of routers and firewalls. While the edge STP concept evolves, it continues to gain traction with network equipment vendors, becoming an important network element that enables change while minimizing risk.

While similar in concept, an edge STP differs from the traditional STP in its use in the network, its placement in the network, and its core capability set. STPs are deployed in the core SS7 network and expected to provide routing for all traffic moving between core network elements – typically SSP (switches) and SCP (application servers or Service Control Points ). Since the service provider’s ‘crown jewels’ are connected to the STP, any change in the STP can be disruptive, and have potentially catastrophic side effects.

In contrast, an edge STP is deployed at the boundary of the signaling network and joins the core network to additional signaling network segments that perform specific functions - for example a new application, an external or physically remote network, the network of a competitor, or a network setup to arbitrage the transport cost/performance factors of IP. Typically, introduction of an edge STP into a network has a minimal impact on the core network. It is often used to route traffic ‘around’ the core network, to further minimize core network impacts.

Operating as a combination of traditional STP and internet router, an edge STP enables an incremental extension of existing telecommunication networks by providing new capabilities at the edge of the network, where advanced services and new networks plug into these existing networks.

The edge STP can make advanced routing decisions as packets cross between networks or network segments based upon information not available in a traditional STP. In addition to routing decisions supported by a traditional STP (point code routing and global title translation), an edge STP can make routing decisions based upon message content (via Deep Packet Inspection (DPI) techniques) and can use information about address plans for subtended networks and the state of nodes in the subtended networks to make further kinds of routing. Thus, an edge STP can differentiate services, optimize traffic flow, provide advanced kinds of load sharing, manage multi-node congestion, enable new hybrid services, provide access control, and hide information.

Edge STPs provide signaling packet routing between SS7 subnetworks, packet conversion between IP (IETF SIGTRAN) and SS7 as needed, selective packet filtering, content-based packet steering, dynamic load distribution, congestion and overload management, and packet screening. Intrinsic to its role, the edge STP must provide security for the networks that it joins. An edge STP provides address translation, much like the internet Network Address Translation (NAT) function. It also provides traffic screening and blocking of undesirable network elements.

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[edit] Use Cases for Edge of Network Routing Capabilities

[edit] Short Message Service (SMS) Optimization

With the burgeoning growth in Short Message Service (SMS) messages sent daily (SMS marketing, stock price updates, traffic alerts, televoting, outpatient medication reminders, package tracking, etc.), mobile operators have seen the capacity of their underlying network infrastructure become severely over-burdened. To address this concern, mobile operators can take advantage of some of the initiatives from the Internet Engineering Task Force (IETF), and move SMS traffic from TDM-based transport to IP-based transport in order to reduce some of the constraints inherent in more expensive, time-consuming TDM transport technology. Edge STPs can be used to offload the SMS traffic on IP and also to intelligently identify and route SMS services traffic (like televoting) appropriately. Edge STPs provide SMS optimization by:

 • Delivering increased SMS capacity with less cost. SMS traffic can be routed in a separate IP network without changing the signaling network infrastructure

 • Providing the protection of existing Short Message Service Center (SMSC) investments by redirecting service SMS traffic directly to the service nodes rather than to the SMSC

 • Offering improved peak-volume handling through the use of IP technology and not being restricted by limited TDM bandwidth. Reduces the cost for TDM links. Adding IP technology will reduce the need for additional TDM links

[edit] Network Security

An edge STP provides a way to implement security policies into various subnetworks without modifying their core behavior or components. As the interworking between telecom networks, the internet, and IP-based networks accelerates, security considerations become more and more critical. Traditional network components reside in the core of the network, where any change can have a catastrophic impact. Acting as a network border element with special routing and security capabilities, the edge STP can provide a secure way to join disparate networks and create a unified virtual network with controlled flow of information between network segments.

The edge STP can route messages in and out of signaling network segments, providing translation services and content-based routing as necessary. It can use white- and black-lists to implement the necessary security policies and perform content-based routing using deep packet inspection if required. Edge STPs enable network security by:

 • Bridging existing and new network segments

 • Enabling functionality to be introduced without changes to network core elements or major network reconfiguration

 • Dynamically blocking unfriendly network elements to provide secured communications

 • Using IP transport transparently for SS7 offload and as the basis for transport across geographic separations

 • Providing translation of message header information, including network indicators and point codes, compensating for differences between network segments

[edit] Switch Migration

As voice networks evolve from traditional circuit switched networks to IP-based networks, legacy switches are being replaced by softswitches and application servers. This migration must be carefully coordinated to ensure uninterrupted service during the transition. An edge STP can manage the message routing to enable the graceful transition of circuits from a traditional switch to a softswitch using a combination of network address (point code) and circuit address (circuit identifier code or CIC) routing. Features enabling an edge STP to be used for switch migration include:

 • New switch equipment can be introduced without any network changes

 • Point code consumption is reduced by enabling many switches to share the same point code

 • Allows for the addition of more trunks without changing the network infrastructure

 • As additional trunks are required, new switching equipment can be added without affecting the public network

[edit] Cross Network Services

When the same SS7 variant is deployed in different countries, or by different network providers within the same country, it is highly probable that there will be point code overlap between countries and providers, which makes inter-operation between networks very difficult. It is impossible for two network elements with the same point code to co exist in an integrated network. These conditions are a common source of difficulty for Mobile Virtual Network Enablers (MVNEs) that offer their services across multiple countries or multiple carriers within a country. MTP network management across all the networks is complex. An edge STP solution can perform the interworking function that conceals the redundancy of point codes. It can translate point codes from one network to another, enabling a network element with one point code in one network to be addressed as another virtual point code in a different network. Edge STPs for cross network services:

 • Integrate into an existing network addressing plan

 • Perform interworking at the STP level of performance

 • Perform point code translation

 • Cause no network operations disruption

 • Deliver a single network management solution

[edit] Long Haul Link Replacement

SS7 traffic can be offloaded onto lower cost, shared-use IP networks by selective routing at the network boundary. This preserves core SS7 network capacity by routing traffic between Service Switching Points (SSPs) at the edge. In this way, edge signaling traffic stays local and does not consume core SS7 network bandwidth. Extending the SS7 network to an IP transport medium reduces carrier leasing and provisioning costs associated with dedicated, long haul SS7 links. The edge STP provides software reliability, powerful functionality in a small footprint, network transparency, and remote management. Features enabling Edge STPs to be used for long haul link replacement include:

 • The use of a single network management solution that is extendable to wireless Metropolitan Area Networks

 • Integration into an existing network addressing plan

 • SSPs are implemented using ISUP, SCCP, TCAP

 • No network operations disruption

 • Utilization of existing SS7 application assets

[edit] Virtual Signaling Network Solutions

As network providers continue to merge, there is a need to combine disparate signaling network segments to provide a cross provider whole signaling network. These segments may be geographically distributed. They may use conflicting values in message headers, requiring translation as messages cross from one network into another. They may have conflicting point codes, security considerations, or have special message routing requirements. Where traditional network components reside in the core of the network where any change can have catastrophic impact, an edge STP provides network integration at the edge of each network segment. Operating as a combination of traditional STP and internet router, the edge STP can route messages in and out of signaling network segments, providing translation services and content-based routing as needed. This approach can also extend the reach of the signaling traffic by using IP-based transport to interconnect geographically disparate signaling network segments. Edge STPs can enable virtual signaling network solutions:

 • Flexible network extension bridging existing networks and Next Generation Networks

 • Needed functionality can be introduced without changes to core network elements

 • Access can be restricted between network segments to enforce security considerations

 • Traffic can be routed to the appropriate network elements using optimal network transport. IP transport can be used transparently for SS7 offload

 • Content-based message routing

 • Translation of message header information including network indicators and point codes to compensate for differences between network segments

[edit] Creating Network Apps using Server Farm Solutions

Edge STPs enable the creation of service applications that leverage the benefits of modern server farm technologies while being able to operate in both the IP-based internet space and the traditional SS7-based telecom signaling networks. Edge STPs provide capabilities such as multi-component availability management and overload control mechanisms that have yet to be provided in IP routers. The capabilities of the edge STP can significantly reduce application and deployment complexity by enabling the internet server farm model for deployment:

 • Deploy applications on few or many standard server farm computing elements

 • Right-size initial deployments, add new farm elements as the need arises

 • Service providers can chose modern internet-honed equipment and management tools

 • Information hiding for increased application security

 • Failures, addition of new farm elements, and hardware or software upgrades of farm elements are all invisible to the core network, causing no disruption

 • Dynamic, efficient load distribution and message steering minimize transaction response times and optimize equipment utilization

[edit] Signaling Hub

An ideal solution to the signaling requirements in the industry is the introduction of a signaling hub that offers the ability to isolate and centralize the interface to the network. Extracting the SS7 interfaces from the system enables the Network Equipment Provider (NEP) to focus on core competencies. Centralizing the interface to the core network in the signaling hub enables the certification of the signaling hub’s network interface one time, allowing additional services and systems to plug in using standardized protocols without the need to re-certify the core network interface. The edge STP is composed of multiple computing platforms maintaining a single point code and network appearance independent of the number of signaling links deployed. Multiple routing scenarios are supported by the edge STP, allowing systems behind the signaling hub to be addressed from the network as a distinct point code or as a segment of traffic of the edge STP’s point code. Edge STPs can be used to enable a signaling hub architecture by:

 • Using computing platforms with minimal bus slots

 • Extraction of the signaling interfaces

 • Leveraging the signaling hub’s pre-certification with the network

 • Enabling rack-and-stack architectures based on IT technology enabling systems to be added, equipment to be replaced, and capacity increased without network or customer impact

[edit] Softswitch of SIGTRAN Signaling Gateway (SG)

Softswitch architectures are composed of multiple open computing platforms where switching functions are disaggregated and divided among the computing platforms to provide scaling and high availability. The Softswitch disaggregation of the circuit switch into Media Gateway (MG), Media Gateway Controller (MGC), and the Signaling Gateway (SG) has provided a flexible architectural model. The SG function is responsible for providing the signaling interface to the network. As additional computing platforms are added to the SG, there is a need to maintain a single SS7 point code towards the network. Each SG is a stand-alone unit and could potentially require a separate SS7 point code, causing the softswitch to present multiple network appearances. The edge STP possesses a highly available architecture composed of multiple computing platforms maintaining a single point code and network appearance independent of the number of signaling links deployed. It has the ability to expand and contract the number of circuits supported by a specific MGC, as well as the number of MGCs while the system is in operation, eliminating downtime for circuit maintenance and capacity changes.

 • Highly available signaling solution minimizes downtime

 • Offloads signaling issues so the MGC need not be involved in network signaling tasks

 • Enables rack-and-stack architectures based on IT technology

[edit] Network Border Element

As networks grow, so does the need for additional network equipment, including STPs. As more STPs are introduced, more ingress/egress points to external networks are created, introducing a greater possibility of security compromise and interface issues. Rather than impact the core network by implementing these interfaces on an STP, a better solution is use of a “network border element”. This can be in the form of an edge STP as a session border controller. The goal is to enable seamless inter-working between networks regardless of the interface, region, or protocol. Security features such as address translations, address and content-based message screening, and content-based message routing capabilities are required. Deep Packet Inspection (DPI) techniques are a natural extension of this approach. The high cost of DPI can interfere with core network operations, so it is often best to deploy such functionality in edge network components rather than core network components. A network border element must often support several international signaling protocols including SS7, SIP, and SIGTRAN. It must commonly support multiple transports (like TDM, HSL, IP, and ATM) to effectively glue together the various network kinds. Use of a network border element or edge STP can offload a significant amount of the problems associated with combining disparate networks:

 • Scales to meet application needs

 • In the case of partnering agreements or Service Provider mergers, allows the re-use of existing equipment and infrastructure

 • Isolates and protects networks through Gateway Screening, point code translation, and content-based routing

 • Offers connections among any network with any other network through Global variant multiple interface support

[edit] See Also

[edit] References