What is an SBC?
To understand the role of a Session Border Controller, let us break the term down to its basic elements:
Session
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A session is defined as a single connection between a pair of signaling devices that passes through the SBC system. Each session is comprised of two call legs: one call leg on a trusted interface and the other on an untrusted interface. Each session in the SBC is identified by a Global Call ID, which is a globally unique identifier assigned by the SBC software. |
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A call leg is defined as a single connection between the SBC and another device. So a session between two devices includes a call leg between device A and the SBC, and a call leg between the SBC and device B.
A call may require a single session or it may require multiple sessions resulting from call forking, conference call, call transfer, call recording or other mechanisms. For example, a call between two registered users through a feature server consumes two sessions: one session from User A to the Feature Server and one session from the Feature Server to User B.
The total number of concurrent sessions supported on the SBC platform may be limited by different factors, including:
- Available Bandwidth – For calls with pass-through media, the SBC computes the media bandwidth required for each call leg, and determines if there is sufficient bandwidth available to host the call. Calls exceeding the bandwidth limit of the interface are rejected.
- Call Rate – If the incoming call rate exceeds the rated capacity of the platform, calls are discarded to protect the system from overload. The number of concurrent sessions required is directly related to the Call Rate and the Call Hold Time (CHT). High call rates with a low average CHT value will result in fewer sessions than the same call rate with a high average CHT value.
- System Limits – Each platform includes upper limits on the number of sessions supported. For example, the SBC 5200 supports a maximum of 64,000 sessions, while the SBC 5100 supports a maximum of 10,000 sessions.
- License Limits – The SBC is licensed for the maximum number of sessions desired. However, the license limit may be less than what the Bandwidth, Call Rate or System limits support. Any call that exceeds the licensed limit of the SBC platform are rejected.
Example #1: Call with one Session
A customer has purchased a 5,000 package of licenses, calls are coming in and egressing the SBC with no call forking – so each ingress and egress is one session. The maximum number of active calls is 5,000.
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Example #2: Call with two Sessions
A customer has purchase a 5,000 package of licenses. Calls are coming in and getting transferred back through the SBC. Each call consists of two sessions, so the maximum number of simultaneous active calls is 2,500.
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For multiple transfers, each new GCID and SIP REFER is considered a session. |
Border
Typically, these sessions will traverse one or more IP networks, whether on an enterprise network or multiple service provider networks. The SBC sits at the border of each network in order to control the amount and type of sessions, as well as the type of data that can be used during these sessions. In this sense the SBC is part firewall, protecting the network from malicious IP traffic, and part traffic cop, policing how much traffic can enter the network in order to prevent overloads.
Controller
The SBC is a controller, which means it controls not only whether traffic can enter the network, but where it should be sent (referred to as session routing) and what type of modifications should be made to the traffic (example, transforming a SIP message header into an H.323 message header or downgrading an HD voice call to a compatible voice codec).
Sonus SBC Portfolio Components
The Sonus
is comprised of the following Sonus Session Border Controller products:
Sonus SBC Edge
Sonus SBC Core
The
addresses the next-generation needs of SIP communications by delivering embedded media transcoding, robust security and advanced call routing in a high-performance, small form-factor device enabling service providers and enterprises to quickly and securely enhance their network by implementing services like SIP trunking, secure Unified Communications and Voice over IP (VoIP).
The
provides a reliable, scalable platform for IP interconnect to deliver security, session control, bandwidth management, advanced media services and integrated billing/reporting tools in an SBC appliance. This versatile series of SBCs can be deployed as peering SBCs, access SBCs or enterprise-SBCs (e-SBCs). The SBC product family is tested for interoperability and performance against a variety of third party products and call flow configurations in the customer networks.
The
can be further expanded to:
- SBC 5000 Series
- SBC / Platforms
Targets small to medium session count deployments (250 to 10,000). These capacities make this product particularly well suited for medium enterprises and small to medium service providers.
- SBC / Platforms
Targets medium to large session count deployments (500 to 64,000). These capacities make this product particularly well suited for large enterprises and medium to large service providers.
- SBC 7000 Series
Targets large session count deployments (up to 150,000 sessions). The product capacity is well suited for large service providers. Example deployment scenarios include:
- Service Provider Access – High subscriber and simultaneous call scale coupled with high availability and redundancy.
- Service Provider Peering – High simultaneous call scale coupled with high availability and redundancy.
- Enterprise and Service Provider Video – Supports large WAN interface bandwidth.
- Wireless – Supports a large number of subscribers and calls where high availability is essential.
- SBC Software Edition (SBC SWe)
Targets small to large session count deployments (25 to unlimited). These capacities make this product particularly well suited for small to large enterprises and service providers. SBC SWe application resides on a private or public virtualized cloud,or on a dedicated server.
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| 1 | SBC Platform Comparison |
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| 3 | SBC Platform Comparison |
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 = supported | Medium Enterprises / Small to Medium Service Providers | Large Enterprises / Medium to Large Service Providers | Scalable SBC |
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Platform | 51x0
| 52x0
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| SBC SWe / SWe on Cloud 
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Maximum number of
non-transcoded sessions | 10,000 | 64,000 | 150,000 | (Refer to SBC SWe Performance Metrics) |
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| Call handling capacity | 250 - 10,000 sessions | 500 - 64,000 sessions | up to 150,000 sessions | 25-unlimited |
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| Full SBC Feature Set | | | | (Refer to SBC Core Key Features) |
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| User Interface | Embedded EMA or external EMS | Embedded EMA or external EMS | Embedded EMA or external EMS | Embedded EMA or external EMS |
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| DSP Expansion Module Types | - 5100: SPS100 / SPS100DB (FRU)
- 5110: DSP20 / DSP25 (CRU)
| - 5200: SPS100 / SPS100DB (FRU)
- 5210: DSP20 / DSP25 (CRU)
| DSP-LC (CRU) | N/A |
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The following table lists the number of ports and storage capacities of the various
platforms.
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| 1 | Ports and Storage Capacities |
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| 3 | Ports and Storage Capacities |
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SBC Core Architecture
This following pages detail the SBC Core and SBC Software Edition architectures: