A Class 5 Softswitch is a key component of modern telecommunications networks that enables advanced calling features and intelligent network services.
As telecom networks transitioned from analog to digital in the 1990s, soft switches were developed to separate the call control functions from the physical voice-switching infrastructure.
This allowed telecom operators to offer innovative services and migrate to new technologies more easily.
Softswitches use software running on standard computer hardware, rather than proprietary hardware, to control calls and process signaling information.
They serve as the nerve center to route calls and trigger services across circuit-switched and packet-switched domains. Softswitches support VoIP, wireless, and legacy TDM networks while enabling convergence of services across these domains.
In this article, we will explain the overview of Class 5 Softswitch, its components, benefits, and emerging trends Read on to gain a comprehensive understanding of Class 5 Softswitches.
Overview of Class 5 Softswitches
A Class 5 Softswitch is designed to replace legacy Class 5 switches that were used in the Public Switched Telephone Network (PSTN).
Unlike their hardware-based predecessors, softswitches separate the call control and service logic from the transport infrastructure.
This provides greater flexibility to deploy advanced services and support new network technologies.
Key functions of a Class 5 Softswitch:
- Call control – call setup, tear down, call routing
- Signaling – processes SS7, SIP signaling protocols
- Service control – triggering intelligent network services
- Subscriber management – call authorization, class of service
- Interfacing – with other networks, gateways, application servers
- Management – operations, administration, maintenance, and provisioning
Benefits of Softswitches:
- Software-based – runs on COTS hardware
- Scalable – can expand capacity easily
- Flexible – supports multiple protocols and interfaces
- Future-proof – easier migration to new technologies
- Advanced services – enables value-added IP services
- Lower costs – reduces the need for proprietary hardware
Softswitch Architectures
There are three main architectural approaches used in Class 5 Softswitch design:
- Standalone – In this model, the Softswitch fully replaces the Class 5 switch and connects directly to the PSTN network. All call control and service logic functions are handled centrally by the softswitch platform.
- Distributed – Intelligence is distributed across multiple softswitch nodes to enhance scalability and redundancy. Call states are shared across nodes for seamless failover.
- Decomposed – Separates call control, service logic, and management functions into distinct modules or servers. Allows independent scaling of each function.
Most modern softswitch architectures are decomposed for maximum flexibility. Separate components typically include:
- Call agent – call routing and control
- Service broker – service logic execution
- Signaling gateway – protocol conversion
- Media gateway – TDM to IP conversion
- Operations server – billing, provisioning, OSS functions
Main Components of a Softswitch
The key components of the Class 5 Softswitch platform include:
1. Media Gateway Controller (MGC)
- Controls connectivity between PSTN and IP networks
- Manages voice trunks, signaling, call admission
2. Signaling Gateway (SGW)
- Terminates SS7 and converts to IP (SIGTRAN)
- Provides interworking between SIGTRAN and SIP
3. Media Gateway (MGW)
- Converts TDM voice to IP packets (and vice versa)
- Supports coding, echo cancellation, QoS marking
4. Service Platform
- Executes service application logic
- Provides APIs for value-added services
5. Operation & Management System
- Element, network, and service management
- Traffic engineering, monitoring, and control
Softswitch Support for VoIP Services
Softswitches play a critical role in enabling carrier-grade VoIP services by providing:
1. Call Routing and Address Translation
A key function of softswitches is to route calls between VoIP users as well as between VoIP and PSTN users. Softswitches have SIP and H.323 interfaces to connect VoIP clients.
They also interface with media gateways using MGCP or MEGACO protocols for interworking with TDM networks. Softswitches perform address translation between IP addresses and phone numbers using ENUM or SIP URI.
2. Call Admission Control
Softswitches implement call admission control (CAC) algorithms to manage bandwidth utilization for optimal voice quality over IP.
CAC restricts calls during network congestion and allocates bandwidth dynamically based on traffic patterns. This ensures good QoS by minimizing latency, jitter, and packet loss for VoIP calls.
3. Codec Negotiation
Softswitches handle codec negotiation between endpoints to establish a VoIP session using a commonly supported voice codec.
This maximizes interoperability as well as voice quality over the IP network. Softswitches also provide transcoding services if a common codec cannot be negotiated between end devices.
4. Emergency Services
For consumer VoIP offerings, service providers must ensure E911 access to emergency services.
Softswitches support emergency call routing and callback features to provide location information of VoIP callers to public safety answering points (PSAPs).
5. Least Cost Routing
Softswitches enable least-cost routing (LCR) whereby calls are dynamically routed over the most cost-efficient path based on time of day, call duration, and contracted rates with upstream VoIP carriers.
LCR optimizes margins for wholesale VoIP services.
6. Number Portability
Number portability allows consumers to retain their phone number when switching service providers.
Softswitches support local number portability (LNP) as well as toll-free number portability for VoIP services via integration with national number portability databases.
7. Billing Mediation
Softswitches generate call detail records (CDRs) that can be processed by back-office billing mediation systems for inter-carrier settlement and customer billing.
Standards like SDR and SS7’s TCAP are used to exchange billing information between softswitches and mediation systems.
In summary, softswitches deliver critical capabilities to enable and enhance VoIP service offerings for consumers and businesses. They are fundamental for service providers to effectively compete in the burgeoning VoIP services market.
Benefits of Softswitches for Service Providers
Key benefits of deploying Class 5 soft switches for telecom operators:
1. Lower Operating Costs
Softswitches help reduce operating expenses for service providers in several ways. By consolidating multiple legacy telecom switches into a centralized software platform, softswitches eliminate the need for costly proprietary hardware.
The software-based architecture is also easier to maintain and upgrade compared to legacy hardware.
Softswitches enable network convergence so that service providers can transport voice, data, and video over a common IP backbone. This reduces network complexity and eliminates the need to operate separate voice and data networks.
2. Increased Scalability
Softswitches provide virtually unlimited scalability to handle growth in subscribers and services.
The centralized control layer makes it easy to add capacity by simply deploying additional media gateways and application servers.
Geographically distributed softswitches allow call control to be handled at local or regional levels while maintaining centralized intelligence. This distributed architecture enables excellent scalability for large network deployments.
3. New Revenue Generation
Softswitches enable providers to launch next-generation services that can drive new revenue.
These include VoIP, multimedia conferencing, IP Centrex, unified messaging, presence, and more.
Softswitches also support advanced call control capabilities like call forking which makes possible find-me/follow-me services.
Integrated class 4 and class 5 features in softswitches eliminate the need for additional SSPs or SCPs to deploy these revenue-generating services.
4. Reduced Time to Market
The software-centric architecture of softswitches allows new services to be introduced faster.
New capabilities can be added via software upgrades without having to replace hardware or add new equipment.
Softswitches also have open APIs that allow third-party applications to be integrated to create innovative offerings.
This future-proofs the network and enables rapid deployment of new services to meet evolving market demands.
5. Improved Network Reliability
Softswitches bring intelligence to call control. Features like automatic alternate routing improves network resilience by rerouting traffic in the event of network failures.
Softswitches also enable sophisticated call admission controls to improve QoS for high-priority voice and video traffic. Centralized network intelligence results in better traffic management compared to distributed architectures.
In summary, softswitches deliver numerous technology and business benefits for service providers. They are a strategic platform to enable next-generation networks and drive competitive advantage.
Emerging Trends in Softswitch Deployments
Softswitches have evolved as the preferred platform for delivering next-generation communications over IP networks.
Here are some key trends shaping softswitch deployments.
1. Virtualization
Virtual softswitches implemented as software applications on COTS servers are gaining prominence.
Virtualization provides inherent high availability, geographic redundancy, and multi-tenancy capabilities. Service providers can quickly deploy softswitch network functions on demand.
2. NFV Integration
Softswitches are integrating with NFV infrastructure for enhanced flexibility.
Media gateways, application servers, SBCs, etc. are evolving as virtual network functions (VNFs). This allows dynamic service chaining of virtual softswitch elements.
3. Cloud Deployment
Cloud-based deployment of softswitch network functions enables scalability and global service delivery.
Multi-national operators can manage centralized softswitch intelligence in the cloud while distributing media gateways at local PoPs.
4. 5G Integration
Softswitches are poised to deliver voice services over 5G NR networks.
They will incorporate network slicing capabilities and enhanced VoIP codecs like EVS for ultra-reliable low latency voice over 5G networks.
5. AI-driven Analytics
Softswitches are leveraging AI and big data analytics for improved traffic routing, predictive maintenance, and better network planning.
Real-time analytics also allows dynamic service creation and optimized user experiences.
6. IMS Integration
Fixed-mobile convergence is driving the integration of softswitches with IMS core for unified services across wireless and wireline networks.
This convergence enables new immersive services blending mobile, voice, video, and messaging.
7. Security Focus
With the proliferation of SIP-based threats, security is a prime focus area for softswitches.
Built-in protection against DDoS attacks, toll fraud, and robocalling provides network resiliency and prevents revenue leakage.
In summary, virtualization, cloud deployment, and enhanced intelligence are key trends guiding softswitch platform evolution to meet service provider demands in the digital era.
These trends are driving continued enhancements in the capabilities and cost-efficiency of softswitch solutions.
Frequently Asked Questions (FAQ)
Ques 1. What protocols are supported by softswitches?
Ans. Softswitches support a range of protocols including SS7, SIP, H.323, and SIGTRAN for telephony signaling as well as protocols like Diameter for authentication and charging functions.
Interworking between protocols is a key capability.
Ques 2. How do softswitches connect to the PSTN?
Ans. They connect to the PSTN via media gateways that convert TDM voice to IP and signaling gateways that translate between SS7 and IP signaling.
Together they enable interconnection between the packet and circuit worlds.
Ques 3. Can soft switches replace mobile switching centers?
Ans. Yes, softswitches with additional mobility functions can replace mobile switching platforms and are known as Media Gateway Controllers.
They enable fixed-mobile convergence.
Ques 4. What role do softswitches play in IMS architectures?
Ans. In IMS, softswitches take on the role of Call Session Control Functions (CSCF) to enable multimedia sessions by interfacing with application servers, gateways, and the HSS.
Ques 5. How does a softswitch support 911 emergency services?
Ans. It integrates with E911 systems to provide location-based routing of emergency calls. It supports features like callback numbers and location identification on emergency calls.
