1 APPLICATION GUIDE SIP Signaling Router (R) Use Cases Using SIP to improve network performance and deliver advanced services This application guide discusses how operators can use a SIP Signaling Router (R) to solve many of their next-gen network challenges Paramount Parkway Morrisville, NC (USA) or This document is for informational purposes only, and Tekelec reserves the right to change any aspect of the products, features or functionality described in this document without notice. Please contact Tekelec for additional information and updates. Solutions and examples are provided for illustration only. Actual implementation of these solutions may vary based on individual needs and circumstances Tekelec. All rights reserved. The Tekelec logo is a registered trademark of Tekelec. All other trademarks are the property of their respective owners. TKLC-AG-001-NA
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3 Table of Contents Introduction...1 The Challenge Session Initiation Protocol (SIP) Signaling Router...1 Use Case 1: Enhanced Application Server... 1 Use Case 2: SIP Trunking...4 Use Case 3: SIP Number Portability... 6 Use Case 4: Centralized SIP Routing...7 Use Case 5: Specialized SIP Proxy Summary...11 About Tekelec...11 Appendix 1: Acronyms used in this document...12 i
4 Introduction The appeal of next-generation, voice over Internet protocol (VoIP) networks is compelling for operators worldwide. Deployments cut across all types of telecom operators from the largest incumbents to the smallest regional players. Providers see VoIP and session initiation protocol (SIP)-based services as an opportunity to cut their operating expenses and boost their bottom line with new revenue. Delivering VoIP and SIP services to consumer and enterprise customers enables providers to expand their subscriber base. And, SIP facilitates the interworking of real-time applications with voice and video to create new, multimedia services. However, as VoIP and SIP traffic and applications grow, so do the requirements placed on the network to support it. Many operators are discovering that their current next-generation networks (NGNs) are based on an outdated, voicearchitecture, which does not support multimedia services, access independence, backward network centric, softswitch compatibility or network growth. The Challenge Unlike signaling system 7 (7) and Internet protocol multimedia subsystem (IMS) networks, which are hierarchical, there is no separate signaling and session control layer at the core of the NGN. From a signaling perspective, each NGN network element must handle all application-layer related tasks such as routing, traffic management, redundancy and service implementation. All possible routes must be defined at each node, creating a logical mesh- signaling tasks network, routing architecture. Expanding the NGN without a framework that offloads session and from the edge elements is complex and costly. Session Initiation Protocol (SIP) Signaling Router Tekelec s SIP Signaling Router (R) solution, a SIP proxy with enhanced routing capabilities, creates a signaling and session control framework for NGNs by implementing SIP routing functionality in the core network. The R enhances routing capabilities and increases service and network flexibility by relieving endpoints of session management duties. The resulting architecture allows the NGN to grow systematically in response to increasing demand for VoIP and multimedia services. The R solution complies with 3 rd Generation Partnership Project (3GPP) specifications and offers adaptations for interworking with non-3gpp-compliant IP environments. It provides seamless interworking and creates an evolution path to future technologies such as IMS, long term evolution (LTE) and WiMAX. This paper explores five use cases that demonstrate the applications and associated benefits of deploying Tekelec s R in NGN networks. They include: Enhanced application server selection SIP trunking SIP number portability Centralized SIP routing Specialized SIP proxy Use Case 1: Enhanced Application Server Problem: The operator, DanTel, provides VoIP services to small enterprise customers, using a SIP enterprise application server (AS) and SIP phones. The SIP AS provides voice features such as find-me, follow-me and simultaneous ring. Each subscriber must be identified and registered on the SIP AS platform. Prior to shipping, DanTel configures each SIP phone with the address of the SIP AS, which is voipsvc.dantel.com. The SIP phone uses this address for registration and to make voice calls. SIP Signaling Router (R) Use Cases Using SIP to improve network performance and deliver advanced services 1
5 Address = voipsvc.dantel.com VoIP AS Hosting Subscriber A through Z DanTel IP Network voipsvc.dantel.com voipsvc.dantel.com voipsvc.dantel.com voipsvc.dantel.com voipsvc.dantel.com voipsvc.dantel.com Figure 1: Subscribers are identified and registered on the SIP AS platform. DanTel has developed a solid reputation for its service quality, and its subscriber numbers have grown significantly. To support current and future growth, the company deploys three additional application servers, each with its own address. Subscribers are now distributed among four application servers. voipsvc1.dantel.com voipsvc2.dantel.com voipsvc3.dantel.com voipsvc4.dantel.com Sub A - F Sub G - M Sub N - S Sub T - Z DanTel IP Network Figure 2: How can DanTel easily map subscribers to the application servers? This new configuration poses a number of problems. With four application servers in the network, how does the SIP phone know which AS to request? And, since the SIP AS address is configured on the SIP phone, each time a customer is assigned to another application server, the address programmed on the SIP phone must be reconfigured. From a technical perspective, the problem is the result of a tight coupling between the SIP endpoints the SIP phones and the SIP AS. Any changes to the physical network, such as adding a new application server, have a direct impact on the way the SIP phones access a service. As a result, complex provisioning is increasing operational costs, and quality of service is being impacted by service disruptions due to provisioning errors. DanTel needs a solution that will allow the company to: 2 Application Guide Tekelec, Inc.
6 Solution: Manage growth without sacrificing quality of service. Make changes to its application server assignments without reconfiguring the phones that are already in service. DanTel deploys the R solution in its network to shield the endpoints from changes in the physical network. Through a process called abstraction, the phones are decoupled from direct knowledge of the complex and changing network. The SIP phones just have to be configured with a single abstract address voip.dantel.com. Endpoints send requests to the R, which resolves the voip.dantel.com address to the appropriate SIP AS platform and routes the request to that platform. Since the endpoint only deals with an abstract view of the network, it is not impacted by changes in the physical network such as adding a new application server. Regardless of changes in the SIP AS topology, the address on the SIP phone remains the same, and no re-configuration is necessary. voipsvc1.dantel.com voipsvc2.dantel.com voipsvc3.dantel.com voipsvc4.dantel.com Sub A - F Sub G - M Sub N - S Sub T - Z Forward the request to correct AS platform where Nick is assigned R Consult internal routing policy A number directed routing Request to voip.dantel.com Figure 3: Endpoints are shielded from changes in the physical network. Nick Benefits: By deploying the R solution, DanTel: Creates a flexible architecture free of endpoint constraints. Saves capital costs by simplifying subscriber management and maximizing the efficiency of application servers through load sharing and flexible subscriber management. Can explore different business models such as using third-party, hosted services. Creates a foundation for multimedia services. SIP Signaling Router (R) Use Cases Using SIP to improve network performance and deliver advanced services 3
7 Use Case 2: SIP Trunking Problem: LinTel is a long-distance (LD) operator that provides service to local phone companies. The company has a number of points of presence (s) conveniently located near the networks it serves. The local phone companies provide service to enterprise customers via primary rate interfaces (PRIs) to private branch exchanges (PBXs). Figure 4: LinTel provides service to local phone companies. With deregulation, LinTel decides to enter the local service market and offer fixed-line services directly to enterprise customers. LinTel can deliver substantial savings by cutting out the middle men, the local phone companies. With SIP trunking, LinTel can enable business customers with IP PBXs to use their Internet connection to provide off-net service. In addition to voice services, LinTel wants to create a foundation for delivering multimedia services to its enterprise customers in the future. LinTel faces several challenges and needs a solution that will enable the company to: Provide enterprise voice service immediately while laying the foundation for future multimedia SIP services. Maintain low start-up cost without compromising the long-term plan. The company could implement a softswitch-based solution, but that alternative has a number of disadvantages. Since it is based on a per connection cost model, the approach can become costly very quickly. The softswitch-based model is voice centric and may not be suited to delivering multimedia services. Softswitch implementations usually are deployed with the switch vendor s choice of application server, so it is difficult to gain the economy of a best-ofbreed solution. 4 Application Guide Tekelec, Inc.
8 Figure 5. SIP trunking enables enterprise customers to use their Internet connection for off-net services. Solution: By implementing Tekelec s R solution, LinTel can use a session-based approach, which balances cost and flexibility. The R creates a SIP signaling and session control layer that routes on-net calls (IP PBX to IP PBX) over the VoIP network, off-net local calls (IP PBX to local numbers), and off-net long-distance calls (IP PBX to long-distance numbers). A PSTN gateway handles IP PBX to public switched telephone network (PSTN) calls. Figure 6: R creates a SIP signaling and session layer to route on- and off-net calls. SIP Signaling Router (R) Use Cases Using SIP to improve network performance and deliver advanced services 5
9 In the process, the company also creates a framework that complies with Internet Engineering Task Force (IETF) and 3GPP standards for the delivery of multimedia services. The solution enables LinTel to create a volume-based cost structure and reduces costs by allowing the company to select best-of-breed application servers. Benefits: With the R solution, LinTel can compete with local telephone companies by offering SIP trunking to enterprise customers. The company receives additional benefits that include: Laying the foundation for multimedia services. Saving money by maximizing the capacity of application servers through load sharing and flexible subscriber management. Creating a SIP peering point to interconnect with other VoIP providers. Use Case 3: SIP Number Portability Problem: LinTel, an LD operator, entered the local calling service market by deploying Tekelec s R solution to build a SIP trunking infrastructure. LinTel is an operator in the call routing sequence immediately prior to the terminating operator. So, it s customary for LinTel to perform number portability, or NP service, for VoIP calls from their SIP- time division trunking service. The company could simply dump calls onto the PSTN gateway and use its existing multiplexing (TDM)-based, number portability solution to route calls to the correct network. However, to do so, there must be adequate intelligent network capacity to handle the increased traffic, and the terminating network must be TDM. If the terminating number is an IP PBX or belongs to another VoIP provider, the call must be shuttled from VoIP to TDM and back to VoIP again. Running pure VoIP calls over the TDM network to perform NP wastes capacity on the PST N gateway and degrades voice quality. Figure 7: Calls destined for a VoIP provider or IP PBX must be routed over the TDM network. Solution: LinTel could replicate an NP solution in its SIP domain, but that is an expensive approach. A more cost-effective and efficient method is to make the TDM-NP solution available to the SIP network. The TDM-NP database can be accessed using the R s 7 access feature. This capability allows the R to augment its routing capabilities with data from the 7 domain. The R provides NP services to the SIP domain in one of three ways: 6 Application Guide Tekelec, Inc.
10 Number portability corrected forwarding proxy: The R receives a request from an originating user agent (UA) such as an IP PBX. The R performs the NP function and then forwards the request to the appropriate SIP endpoint for call completion. Number portability corrected redirect server: The originating UA sends a request to the R, which performs the NP function to determine the endpoint destination. The R then sends a SIP redirect message to the UA that instructs the UA to forward the request to the appropriate destination. Number portability corrected forwarding application server: After receiving a request from the originating UA, the R performs the NP processing to locate the called number. It modifies the request with the destination information and sends it back to the originating UA. The UA then proxies the call to the appropriate SIP endpoint. Figure 8: R accesses TDM-NP database using 7 access feature. Benefits: Since NP is deployed through a standard SIP framework, the approach can be used in the next-gen network as well as a future IMS network. End-to-end media transparency is maintained, so the NP solution can be applied to voice service AND any other type of multimedia service such as a video or IPTV. The 7-access feature used for the NP application also supports access to other 7-based applications like calling name, toll-free and message-waiting indicator. Use Case 4: Centralized SIP Routing Proble m: AsiaTel, a hub provider, offers voice transit and signaling services to fixed-line and mobile operators. The company deployed softswitch technology to take advantage of lower Internet protocol (IP) transport costs. Softswitches, which serve as s, are installed throughout Southeast Asia in a fully meshed framework. Every switch must be defined in the translation table of every other switch. SIP Signaling Router (R) Use Cases Using SIP to improve network performance and deliver advanced services 7
11 AsiaTel Network Voice Text Multi-media SIP Client Figure 9: Softswitches, serving as s, form a fully meshed architecture. AsiaTel would like to expand its network to serve other Asian markets. The company also plans to enhance its portfolio by offering transit services for text messaging and multimedia applications. And, it would like to provide SIP peering as an alternative to TDM to other VoIP providers. The new business plan presents a number of issues for the meshed, softswitch network. Expanding the network requires the addition of new softswitches to increase capacity. Provisioning is complex as each new piece of equipment must be provisioned with the routing entries for all of the existing softswitches. And, the existing softswitches must be updated with the routing entries for the new equipment. Since routing is based on pre-defined SIP trunks, route management becomes increasingly complex as the network expands. Service and subscriber data are tightly coupled with the softswitch, making it difficult to change an existing service or add new applications uniformly. AsiaTel must address several complex issues related to growing its network, including how to: Expand its network AND keep network operation costs low. Offer voice and non-voice services AND reduce capital costs. Prevent degradation as media flows through its network. Like many operators, AsiaTel views these as three, unrelated challenges. As a result, they deploy multiple, point solutions, which increase long-term CAPEX and OPEX. However, if AsiaTel took a holistic view of the network, they would see that they are, in fact, all related. A piecemeal approach will not address the challenges because solving one problem likely exacerbates another. Solution: AsiaTel creates a SIP-based reference architecture over it existing network by deploying the R as a SIP proxy. With this approach, all calls are routed by default from the softswitch to the R. The R makes layer-5 SIP routing decisions based on advanced routing algorithms and forwards the request to the appropriate SIP destination. 8 Application Guide Tekelec, Inc.
12 SIP Client AsiaTel Network SIP Signaling Router SIP Signaling Router SIP Client Figure 10: R creates a SIP-based reference architecture. Benefits: The company now has a centralized SIP signaling and session control framework that: Acts as a route manager for all of the softswitches, relieving them of routing functions. Eliminates the mesh network, so there is no longer a need to provision translation tables on each and every switch. Maintains end-to-end media transparency so the endpoints can communicate using any media voice, text, video, or data streaming. Preserves media quality because there is no decoding/encoding required in the network. Use Case 5: Specialized SIP Proxy Problem: EuroTel is a provider of fixed and mobile services. The company maintains its operation as two, separate businesses EuroTel Telecom and EuroTel Mobile. The fixed and mobile networks are loosely coupled through TDM peering. Each network views the other as a foreign network. Figure 11: EuroTel s network before consolidation. SIP Signaling Router (R) Use Cases Using SIP to improve network performance and deliver advanced services 9
13 EuroTel wants to consolidate the networks and create a single operating entity EuroTel to reduce its operating costs. The company also plans to expand its offerings with integrated mobile and fixed services, mobility solutions for fixed-line enterprise customers and future multimedia services. Since EuroTel already has some SIP deployments in its fixed-line network, it has decided to take the opportunity to upgrade its underlying wireless network technology to SIP as well. By doing so, the company can lower the cost of network integration and create a future path for multimedia services. EuroTel s plan is to cap its existing TDM-based mobile switching centers (MSCs) and begin deploying SIP-capable mobile softswitches. Its strategy is to interconnect the mobile softswitches with the existing wireline SIP softswitches. EuroTel MSC SMSC Switch VM SCP Mobile Softswitch Softswitch Figure 12: EuroTel connects mobile and wireline softswitches with SIP technology. However, EuroTel faces a problem common to many operators: different vendors supply the mobile and landline softswitches. The softswitches are unable to establish sessions because the vendors use different SIP implementations. The two vendors refuse to recognize the interoperability issue as a problem, but they gladly will provide a customized solution to EuroTel - if the company is willing to pay for it. EuroTel is caught in a situation called vendor lock-in. As long as the company deploys equipment from a single vendor, there is no problem. But, when it introduces equipment from another vendor, interoperability problems arise. This situation creates significant challenges for the company. How can it solve the interoperability issue without spending an excessive amount of money for a customized solution or being forced to purchase all of its equipment from a single vendor? How can the company avoid the same problem in the future as it brings new elements from other vendors into the network? Solution: EuroTel deploys the Tekelec R as a protocol mediation point between the different vendor products. This approach creates an architectural solution that is independent of the endpoints and eliminates interoperability problems. The R solution, which is deployed in the signaling layer, can be implemented in one of two ways: as an internal R feature or as an external application. With the R solution, EuroTel creates a SIP-based, NGN reference architecture over its existing network. In this role, the R acts as a proxy server to route SIP traffic between the mobile and landline softswitches. It also forms a mediation point that fixes protocol variations on-the-fly between the softswitches. 10 Application Guide Tekelec, Inc.
14 Benefits: Figure 13: R acts as a mediation point between softswitches and routes traffic between them. EuroTel now has the SIP signaling and session control framework that solves its immediate interoperability needs and: Creates the foundation for a multi-vendor environment and future multimedia services. Enables the company to choose best-of-breed products, avoiding vendor lock-in. Provides a centralized SIP monitoring point. Summary The current NGN architecture has no core signaling/session framework, which greatly limits its expansion capabilities. History shows that the signaling and session control layer is critically important to any large-scale network architecture. Having softswitches and other endpoints perform layer-5 session management may be sufficient for fairly small deployments and simple management tasks. But, as the network expands, the lack of a capable session framework introduces a host of network issues. A suitable session framework that off-loads the various signaling and session tasks from the edge NGN elements enables NGN networks to expand efficiently and avoids the pitfalls created by a point-to-point, virtual-mesh routing network. Just as core routers are used to minimize the routing burden on IP endpoints, layer-5 SIP routing capability can be used to reduce the routing burden on NGN endpoints by centralizing session management tasks at the network core instead of at each endpoint. The resulting architecture can expand systematically to support VoIP subscriber growth, deliver advanced multimedia services and create the foundation for future technologies and services. About Tekelec Found at the heart of most global networks, Tekelec s market-leading, mission-critical, high-performance network solutions enable the secure and instant delivery of calls and text messages for more than one billion mobile and fixedline subscribers. The company s session management solutions allow telecom operators to manage the diverse applications, devices, technologies and protocols, across existing and evolving networks, to meet the demands of today s consumer. Tekelec uniquely ensures telecom operators have a clear migration path to SIP-based IP networks, and whatever comes next, with the flexibility to deploy solutions at a pace dictated by their business needs. For more information, please visit SIP Signaling Router (R) Use Cases Using SIP to improve network performance and deliver advanced services 11
15 Appendix 1: Acronyms used in this document 3GPP 3 rd Generation Partnership Program AS Application server IETF Internet Engineering Task Force IMS Internet protocol multimedia subsystem IP Internet protocol IP PBX Internet protocol private branch exchange LD Long distance MSC Mobile switching center NGN Next generation network NP Number portability Point of presence PRI Primary rate interface SIP Session initiation protocol 7 Signaling session 7 R SIP signaling router TDM Time division multiplexing UA User agent VoIP Voice over Internet protocol 12 Application Guide Tekelec, Inc.