Diameter Routing Use Case Guide
Diameter Routing Use Case Guide Table Of Contents Introduction...1 Sonus Diameter Signaling Controller Overview...1 Centralized Routing...2 Deployment of Multiple s in Either an LTE/EPC or Network... 4 PCRF Binding... 5 Roaming to Non-LTE Network Providers... 6 Roam Steering...7 Security Inter-Network Topology Hiding... 8 Security TLS... 9 Security IPsec... 9 Routing Segmentation...10 Glossary... 11 About Sonus...12.
Introduction Today, mobile network operators are faced with the challenges of building 4G LTE/EPC networks to meet the demands of. subscriber devices such as smartphones and tablets, and the always on applications they support. As and LTE. infrastructures are deployed, new elements such as policy servers, gateways, session controllers and charging systems are interconnected. These new elements interwork via Diameter protocol to exchange critical network and services information. Diameter signaling capabilities support all subscriber services, both revenue generating and non-revenue generating; thus its criticality to the overall network performance and stability cannot be underestimated. The sheer volume and complexity of. this Diameter traffic places staggering demands on core signaling elements, causing serious concerns about the reliability. of the network. Many issues have arisen in the initial stages of network deployment, including network scalability, exponential increases in signaling traffic, network outages, compatibility of interconnected network elements, and others too numerous. to mention. Sonus Diameter Signaling Controller (DSC) Overview The Sonus Diameter Signaling Controller (DSC) provides a flexible, robust carrier-grade solution to the Diameter routing dilemma. The Sonus DSC provides essential functions of centralized core and edge routing for Diameter protocol elements widely used in the all-ip, service-oriented and Long Term Evolution (LTE) architecture networks. These functions include: Diameter Routing Agent (DRA) as Specified by 3GPP Diameter Edge Agent (DEA) as Specified by GSMA Subscription Location Function (SLF) Inter Working Function (IWF) The Sonus DSC s flexible and open architecture allows network planners the ability to make intelligent deployment decisions. Diameter features can be deployed separately or within the same unit. Extensible and Flexible Routing Sonus developed the Sonus DSC to be a flexible routing engine with advanced screening capabilities, providing the ability to route and screen on any AVP in the message. Architected for extensibility, as well as straightforward evolution to future Diameter applications, this high-powered platform makes the Sonus DSC ideal for LTE/EPC and networks. World-Class Support Sonus provides a vast array of support services, including network planning, engineering, installation and training. The support organization has a vast degree of expertise in network routing and protocols in mission-critical networks such as SS7. These services are offered on an a la carte basis and can be tailored to meet individual customer requirements. Diameter Routing Use Case Guide 1
HPMN Sh Ro S-CSCF Cx Ro Cx I-CSCF SWx OCS P-CSCF S6d S6a S6a Rf OFCS AAA Rx EIR Gy Gz H-PCRF S13 Gx S9 S6b SWd VPMN Gxc V-PCRF 3GPP AAA Proxy Gxb SGSN epdg SWm SWa Gxa STa Trusted Non Trusted Figure 1: LTE/EPC Network Centralized Routing Problem: The architecture of the LTE/EPC network defines a large quantity of network elements, each with its own functionality. Each network element can have multiple interfaces to other elements, based on the procedures and information exchanged. Additionally, the peer concepts of the Diameter protocol and the connection-oriented methodologies of the Stream Control Transmission Protocol (SCTP) significantly increase the complexity and quantity of routing rules within the network. As the network continues to evolve and grow, additional routing rules have to be provisioned in every network element. The routing complexity inherent within this mesh-type network presents a twofold problem. First, the large task of maintenance and administration of routing rules on individual nodes directly affects the consistency and scalability of the network. Second, placing the routing responsibility on the individual network elements can degrade the network element s ability to perform its primary function. 2
HPMN OFCS OCS Gz Gy Sh Ro Cx Ro S-CSCF Cx Rf Rx I-CSCF P-CSCF S6a SWx H-PCRF Gx S6b AAA VPMN MMC SGSN Gxc S6a S6d STa S9 V-PCRF Gxb SWd SWa epdg 3GPP AAA Proxy Gxa Trusted Non Trusted Figure 2: LTE/EPC Network with Sonus DSC Solution: Sonus Diameter Signaling Controller provides a more efficient and scalable network architecture. By placing the Sonus DSC in the core of the network, routing is centralized, reducing the quantity and complexity of inter-network and intra-network routing. Also, since the routing responsibility is removed from individual network elements, their expensive resources are freed up to perform their primary function, thus reducing network-wide capital expenditures. Benefits: The benefits realized from a network topology including a Sonus DSC are numerous: Simplifies Connectivity Maintenance/Provisioning Congestion Management Routing/Traffic Management Network Protection Security Firewalls Topology Hiding Cost-Effective and Flexible Network Deployment Scalability Load Balancing Session Routing and Control Interoperability Value-Added Services Roaming Management Roam Steering Diameter Routing Use Case Guide 3
Deployment of Multiple s in Either an LTE/EPC or Network Problem: Home Subscriber Servers (s). Routing Info are deployed in LTE/EPC and networks.. In networks, s are responsible for. subscriber-specific authorizations, service profiles and preferences. In LTE/EPC networks, the is responsible for Mobile Authentication and other HLR-like functionalities. Either. an increase in numbers of subscribers or the. S-CSCF -A need for network diversification can drive network operators to deploy multiple s. I-CSCF Diameter In networks that contain multiple s, the subscriber identity is used to route to the appropriate containing a particular AAA -B subscriber s information. Each node requesting the subscriber information would have to. be provisioned with routing information, including subscriber identity and the s address containing the subscriber s profile. Figure 3: Multiple s with No Diameter Router Routing Info Solution: By deploying the Sonus Diameter Signaling Controller with Subscription Locator Functionality,. S-CSCF -A a more efficient routing methodology can be used. The Sonus DSC with. SLF would be provisioned with I-CSCF subscriber identity and mapping to. the appropriate. AAA DRA with SLF Diameter -B Benefits: The benefits realized from. a network topology containing a Sonus DSC with SLF functionality include: Figure 4: Multiple s with Sonus DSC More Efficient Routing Enables a More Reliable. Network Multiple s Reduces Operations Expenditures Less Routing Rules to Administer Increases Network Scalability 4
PCRF Binding Problem: The Policy Charging Rules Function (PCRF) is becoming increasingly more important in managing network operators resources while balancing the subscriber s network data utilization experience. As network operators push to increase their Annual Revenue Per User (ARPU) by offering tiered data plans and the introduction of Voice over LTE (VoLTE), the role of the PCRF is one. of the most critical within the network. The PCRF is used for the authorization of a subscriber s bandwidth allocation based on multiple factors, including the subscriber s past usage, the level of service a subscriber has purchased, and the amount of resources currently available in the network. When a subscriber establishes an IP/data session (IP-CAN) within the network, a PCRF is assigned to authorize the session and maintain a Quality of Service (QoS) for the session. IP-CAN/PCRF binding ensures the initial PCRF assigned for the session is responsible for maintaining the rules and QoS during the life of the session. Multiple PCRFs are deployed in the network, based on either network scalability requirements or PCRF vendor product architectures. This type of network topology requires an. IP-CAN/PCRF binding capability within the network. Solution: By deploying the Sonus Diameter Signaling Controller including IP-CAN/PCRF binding capabilities, multiple PCRFs can be provisioned in the network. The flexibility provided by the Sonus DSC enables efficient network design to meet the needs of both operators and subscribers. The Sonus DSC IP-CAN/PCRF binding functionality can be integrated with any of the Sonus DSC functionalities or deployed on a standalone basis. Benefits: The benefits realized from a network topology containing a Sonus DSC with the IP-CAN/PCRF binding functionality include: Network Scalability Network Design Flexibility P-CSCF PCRF PCRF PCRF V-PCRF PCRF PCRF PCRF Trusted Figure 5: PCRF Binding with Sonus DSC Diameter Routing Use Case Guide 5
Roaming to Non-LTE Network Providers Problem: When mobile network operators start their deployment of LTE/EPC, it is important to provide subscribers with the widest breadth of coverage possible. In order to provide the coverage required by the subscribers, the home network (LTE/EPC) provider might have roaming agreements with non-lte networks such as 2G or 3G operators. The home network provider would have provided its customers with multi-mode handsets to facilitate this roaming. Since the 2G/3G networks are SS7 signaling based, and the LTE/EPC networks are Diameter signaling based, an interworking function is required to translate from the Diameter signaling protocol in. the LTE network to the SS7/MAP signaling protocol used in the 2G/3G networks. Without this translation/interworking function, it is impossible for a subscriber to roam from an LTE/EPC/Diameter network to a 2G/3G/SS7/MAP network. SGSN HLR SS7/MAP Diameter Home LTE/EPC Network Visited 2G/3G Network Figure 6: Roaming to Non-LTE Network Solution: The deployment of the Sonus Diameter Signaling Controller, complete with the Inter Working Function (IWF), solves the. problem of subscribers roaming from an LTE/EPC Diameter signaling protocol network to a non-lte network by providing the translation and mapping capability required for communication between Diameter-based networks and SS7-based networks. Benefits: The benefits realized from a network topology containing a Sonus DSC with the SS7/Diameter IWF include: Smooth Migration to. LTE/EPC Network Topologies Better Roaming Capabilities Increased Subscriber Satisfaction Reduced Churn Increased Revenues LTE Subscriber Information LTE Subscriber SGSN HLR Diameter Diameter - MAP Interworking SS7/MAP DRA IWF Home LTE/EPC Network Visited 2G/3G Network Figure 7: Roaming to Non-LTE Network with Sonus DSC 6
Roam Steering Problem: As mobile operators address the business challenges of trying to increase ARPU and decrease subscriber churn, some of the most critical factors they face are roaming management, roaming agreements and QoS while roaming. To maintain financial margins, mobile operators must be able to negotiate equitable roaming agreements and subsequently manage subscriber roaming to meet the conditions of the roaming agreements. Additionally, subscriber roaming satisfaction directly correlates to a reduction in churn. Currently most of the Steering of Roaming (SoR) solutions are SS7-based and are not deployable in LTE/EPC networks without major modifications. Solution: The deployment of the Sonus DSC as a Diameter Edge Agent as recommended by GSMA (PRD IR.88 LTE Roaming Guidelines 3.0 ) provides a single point of interface to all interconnected networks, whether directly connected or connected through a Hub Provider. Diameter messages used for Roam Steering pass from the VPLMNs through the Sonus DSC acting as a Diameter Edge Agent. The Diameter messages are passed to the Roam Steering application registered with the UDR, where they are acted upon and the resultant message sent back to the UDR for routing. Benefits: The benefits realized from a network. topology containing a Sonus DSC acting as a. Diameter Edge Agent with Roam Steering include: hpcrf HPMN More Efficient Routing Higher Roaming Revenues Better Roaming Capabilities Increased Subscriber Satisfaction. Reduced Churn Increased Revenues SGSN PCRF SGSN PCRF SGSN PCRF VPLMN A x LTE Subscriber VPLMN B VPLMN C Figure 8: Roam Steering with Sonus DSC The following explanation is represented in Figure 8 (above). LTE Subscriber turns on their phone in an area served by VPLMN A, VPLMN B and VPLMN C. Both VPLMN A and VPLMN B have roaming agreements with LTE Subscriber s HPLMN; however, the agreement with VPLMN B calls for a higher percentage of traffic than VPLMN A. The LTE Subscriber handset sends a registration message to its HPLMN through VPLMN A and the message is received by the Sonus Diameter Signaling Controller in the HPLMN. The Sonus DSC forwards the registration message to the Roam Steering application, which checks the subscriber, roaming conditions and roaming agreement parameters. The Roam Steering application finds that VPLMN B is the optimum roaming provider for both itself and the subscriber. The Roam Steering application sends rejection messages to the UDR for routing to VPLMN A and ultimately to the LTE Subscriber s handset. The rejection message is received by the LTE Subscriber s handset. The LTE Subscriber s handset sends a registration message to its HPLMN through VPLMN B and the message is received by the Sonus DSC in the HPLMN. The UDR forwards the registration message to the Roam Steering application which checks the subscriber, roaming conditions and roaming agreement parameters. The Roam Steering application sees that the registration is for VPLMN B and that it is the chosen provider. The Roam Steering application lets the registration process continue to its completion. Diameter Routing Use Case Guide 7
Security Inter-Network Topology Hiding Problem: During the design phase of an. LTE/EPC network, service providers might decide to interconnect other networks at the individual network element level, using the topology shown in Figure 9. When using this interconnection scheme, both the visited and home networks topology. are totally open to each other, including node types, addresses, etc. In this open type of interconnection, if a malicious hacker is able to compromise a trusted node within the network, access can be gained to most other network components and then further attacks mounted based on the information gained.. HPMN S6d VPMN SGSN S6a S13 S6a EIR SWx Sh Ro Cx Gy OCS Gz Gx Gxc Gxa Trusted OFCS H-PCRF S9 V-PCRF Gxb epdg Ro STa SWm Rf S6b Cx AAA SWd 3GPP AAA Proxy S-CSCF SWa I-CSCF P-CSCF Non Trusted Solution: The deployment of the Sonus Diameter Signaling Controller as a Diameter Edge Agent as recommended Figure 9: LTE/EPC Network by GSMA (PRD IR.88 LTE Roaming Guidelines 3.0 ) provides a single point of interface to all interconnected networks, whether directly connected or connected through a Hub Provider. This single point of contact for all interconnected networks enables Topology Hiding, thus increasing the security of the network by protecting the nodes/addresses from being exported to foreign networks. Benefits: The benefits realized from a network topology containing the Sonus DSC deployed as a Diameter Edge Agent include: Better Network Security More Efficient Inter-Network Routing Rx VPMN HPMN S6a SGSN S6d vpcrf S9 hpcrf Figure 10: Sonus DSC/Diameter Edge Agent 8
Security TLS Problem: Although there are a large number of security mechanisms specified for the EPC network, security challenges continue. to exist due to the open nature of the architecture. Protocols used in the EPC, including Diameter, Stream Control Transmission. Protocol (SCTP) and GPRS Tunneling Protocol (GTP), have specified security improvements. However, security vulnerabilities still. exist and can be introduced in the network design phase, the implementation phase or the operations/configuration phase. Solution: The deployment of a Sonus Diameter Signaling Controller with its inherent Transport Layer Security (TLS) capability significantly increases the security of the control/signaling plane. TLS is a cryptographic protocol that provides security for IP communications. TLS encrypts packets within a segment of network connections at the application layer, using asymmetric cryptography for key exchange, symmetric encryption for privacy and message authentication codes for message integrity. Benefits: The benefits realized from a network topology including a Sonus DSC including TLS include: Increased Network Control/Signaling Plane Security Increased Network Reliability Hop by Hop Security Network Address Translator (NAT) Traversal. Security IPsec Problem: Although there are a large number of security mechanisms specified for the EPC network, security challenges continue to exist due to the open nature of the architecture. Protocols used in the EPC, including Diameter, Stream Control Transmission Protocol (SCTP) and GPRS Tunneling Protocol (GTP), have specified security improvements. However, security vulnerabilities still exist and can be introduced in the network design phase, the implementation phase or the operations/configuration phase. Solution: The deployment of a Sonus DSC with its inherent IP Security (IPsec) capability significantly increases the security of the control/signaling plane. IPsec is a protocol suite used to secure IP communications by using authentication and encryption of IP packets during the communications session. IPsec has the capability to establish mutual authentication at the beginning of a session and to negotiate cryptographic keys used during the session. IPsec (RFCs 2401, 2406, 2409, 2411) is a protocol suite that runs at the networking layer (L3). It provides confidentiality, integrity protection, data origin authentication and replay protection of each message by encrypting and signing every message. Benefits: The benefits realized from a network topology containing a Sonus DSC with IPsec include: Increased Network Control/Signaling Plane Security Increased Network Reliability Diameter Routing Use Case Guide 9
Routing Segmentation Problem: The deployment of LTE/EPC by network service providers has uncovered issues and opportunities directly related to routing messages to other interconnected networks. One of the key opportunities is for an LTE/EPC network operator to resell internetwork connection and message transport capabilities to other operators. The combination of a complex LTE/EPC network, numerous interconnected networks, and vendors wide diversity of equipment presents service providers with the challenge of setting up routing rules, shaping traffic and handling Diameter protocol inconsistencies on an interconnected network basis. The deployment of separate Diameter routers has been investigated; however, this significantly increases the operations and capital cost. Another solution is having consolidated routing rules for both intra-network and inter-network traffic. This massive routing configuration leads to complexity and increases the chances of errors when making routing/traffic rules changes. Solution: The Sonus Diameter Signaling Controller, built on Sonus s network-proven Dynamic Routing Engine, provides more efficient, flexible and scalable Diameter routing solutions. The Sonus DSC enables the definition of separate Diameter Routing Agents within a single Sonus DSC. Each of these virtual Sonus DSCs has its own separate routing and screening rules which include the ability to shape traffic on a per-peer basis. This shaping includes traffic flow control, throttling and congestion per peer. Sonus s industry-proven, flexible routing concept provides increased control, as well as ease of implementation, and it opens the door to increased service provider revenues. Benefits: The benefits realized from a network topology containing a Sonus DSC are numerous: Simplifies Routing Maintenance/Provisioning Congestion Management Routing/Traffic Management Load Balancing Session Routing and Control Interoperability Network Protection Topology Hiding Cost-Effective and Flexible. Network Deployment Value-Added Services LTE/EPC LTE/EPC enodeb CSCF enodeb CSCF UDR Virtual Virtual Virtual Virtual LTE/EPC LTE/EPC CSCF enodeb enodeb CSCF Figure 11: Roam Steering with Sonus DSC 10
Glossary 2G Second Generation LTE Long Term Evolution 3G Third Generation MAP Mobile Application Part 3GPP Third Generation Project Partnership Mobility Management Entity 4G Fourth Generation NAT Network Address Translator AAA Authentication Authorization Accounting OCS Online Charging System ARPU Annual Revenue Per User OEM Original Equipment Manufacturer Application Server OFCS Off Line Charging System AVP Attribute Value Pair OPex Operations Expenditures DEA Diameter Edge Agent PCRF Policy and Charging Rules Function DRA Diameter Routing Agent P-CSCF Proxy Call Session Control Function DSC Diameter Signaling Controller PDN Gateway Packet Data Network Gateway EPC Evolved Packet Core PRD Permanent Reference Document EPDG Evolved Packet Data Gateway QoS Quality of Service GPRS General Packet Radio Service RFC Request for Comment GSMA GSM Association S-CSCF Serving Call Session Control Function GTPQ GPRS Tunneling Protocol SBC Session Border Controller HPLMN Home Public Land Mobile Network SCTP Stream Control Transmission Protocol HLR Home Location Register SGSN Serving GPRS Support Node Home Subscriber Server Serving Gateway I-CSCF Interrogating Call Session Control Function SLF Subscription Locator Function IETF Internet Engineering Task Force SoR Steering of Roaming IP Multimedia Subsystem SS7 Signaling System Seven IP Internet Protocol TLS Transport Layer Security IP-CAN Internet Protocol Connection Access Network VoLTE Voice over Long Term Evolution IPsec Internet Protocol Security VPLMN Visited Public Land Mobile Network IWF Inter Working Function Diameter Routing Use Case Guide 11
About Sonus Sonus is a global supplier of advanced, high availability network communications solutions. Its Diameter and SS7 Signaling Systems provide tightly integrated signaling and advanced routing capabilities and applications that uniquely span the mission-critical demands of both existing and next-generation 4G LTE and telecommunications networks. From VoIP to SIP, session border controllers to session management, the world communicates better on Sonus Networks. Since 1997, Sonus has built some of the world s most advanced IP communications networks both as the preferred technology partner to the world s largest service providers, and as a trusted partner to Global 500 enterprises that require secure, real-time communications. Today, Sonus solutions drive more VoIP traffic than any other vendor: over one billion minutes every day. Sonus North American. Headquarters Sonus APAC Headquarters Sonus EMEA Headquarters 4 Technology Park Drive Westford, MA 01886 U.S.A. Tel: +1-855-GO-SONUS 1 Fullerton Road #02-01 One Fullerton Singapore 049213 Singapore Tel: +65-68325589 Edison House Edison Road Dorcan, Swindon Wiltshire SN3 5JX Tel: +44-14-0378-8114 To learn more, call Sonus at 855-GO-SONUS or visit us online at www.sonus.net The content in this document is for informational purposes only and is subject to change by Sonus Networks without notice. While reasonable efforts have been made in the preparation of this publication to assure its accuracy, Sonus Networks assumes no liability resulting from technical or editorial errors or omissions, or for any damages resulting from the use of this information. Unless specifically included in a written agreement with Sonus Networks, Sonus Networks has no obligation to develop or deliver any future release or upgrade or any feature, enhancement or function. Copyright 2014 Sonus Networks, Inc. All rights reserved. Sonus is a registered trademark of Sonus Networks, Inc. All other trademarks, service marks, registered trademarks or registered service marks may be the property of their respective owners. 12 DS-1401 5/28