In this section:
Not supported by SBC SWe Lite in this release.
This document describes how to calculate DSP (Digital Signal Processor) resource consumption for hardware that began shipping from Ribbon as of November 2016. For DSP consumption associated with older versions of hardware, refer to the appropriate release documentation on the Ribbon Documentation Portal.
This guide is intended to help partners and customers regarding the capacity and use of DSP resources in the newly updated hardware that began shipping as of November 2016, with the expectation that partners and customers select the appropriate instance of SBC Edge to satisfy call deployment requirements.
This guide is intended to be used by Ribbon customers to help select a SBC Edge configuration instance that includes an appropriate quantity of DSP resources to support a given density of call sessions subject to DSP-related media intervention.
Transcoding: The action taken by a DSP (Digital Signal Processor) within a physical SBC Edge on a bi-directional media session to accomplish some form of intended media manipulation (e.g. translation of media from one codec to another, encrypting/decrypting media, etc.)
Default transcoding scenario: The most common IP ↔ IP transcoding scenario for SBC 1000 is from G.711 (RTP) to G.711 (SRTP). This is considered as the default transcoding scenario for SBC 1000 when calculating DSP resource requirements.
DSP resource: A DSP resource is a unit of DSP processing required to transcode from one codec to another. For the SBC 1000, one DSP resource is equivalent to the processing ability associated with one transcoding session for the default transcoding scenario (described above).
DSP resource requirement number: The number of DSP resources required to support a specific number of IP ↔ IP sessions. All calculations mentioned in this document build upon the default transcoding scenario mentioned above. For example, DSP resource requirement number for 100 IP ↔ IP sessions for a default transcoding scenario is 100.
Special case for multiple low-bit rate codecs: If two or more low-bit rate codecs (G.729ab, G.723.1, G.726, or T.38) are used (IP ↔ IP and/or TDM/IP), a 20% uplift is applied to the DSP resource requirement number.
Example: Two or more low-bit-rate codecs are used.
DSP Resource Requirement | 100 |
Plus 20% Uplift | 20 |
True DSP Resource Requirements | 120 |
Multiplication Factor: Value derived from Table 1. The multiplication factor is multiplied by the number of sessions required for your deployment to provide the total number of DSP resources required for those sessions and selected codecs.
DSP Mode: Implies a session that is to be acted upon by the DSPs; i.e., a session requiring media services.
RTP Proxy Mode: A session that is not subject to DSP services but flows through the SBC Edge for non-media intervention purposes (e.g., IP headers being modified for revised network addressing, etc.) is considered a session running in RTP Proxy mode and does not use any DSP resources.
Direct Media Mode: A session that is not subject to, and does not flow through, the SBC Edge is considered a session running in Direct Media mode. Sessions running in Direct Media mode do not use any SBC Edge media processing resources including DSP resources.
The following table provides the multiplication factor (for use in conjunction with the IP ↔ IP session count requirement) to help users determine the required quantity of DSP resources. The IP↔ IP operating mode is a bidirectional media session, anchored by the SBC Edge, between two SIP/RTP endpoints.
An SBC Edge can support both IP ↔ IP and TDM ↔ IP modes simultaneously.
To determine the multiplication factor for your transcoding scenario, select from-codec (Codec Type column) and to-codec (Codec Type row) in the following table. The intersecting cell gives you your multiplication factor.
SBC 1000 IP ↔ IP DSP Multiplication Factor (click to enlarge)
The TDM ↔ IP operating mode is a bidirectional media session, anchored by the SBC Edge, between a non-SIP/RTP endpoint (e.g., an FXS client, an FXO trunk, a PRI/BRI channel, etc.) and a SIP/RTP endpoint.
Resource requirements for TDM/FXx ↔ IP flows can be derived from Table 1. However, the DSP resource requirement presented from Table 1 will be subject to a 50% reduction in value. Note the TDM/FXx leg of the call can be approximated as a G.711 non-encrypted SIP leg from a media services perspective.
For example, in an TDM/FXx ↔ IP flow where encryption on the IP media flow is required with the selection of the G.722.2 codec:
Note the preceding calculation scheme assumes VAD on (60% silence during call), RTCP on, RFC2833 on, and 20ms packet size for all codecs (except 30ms for G.723.1), G.722.2 at 12.65 kbit/s, RTP(unless specified with SRTP ), and standard Line Echo Canceller.
An SBC Edge can support both IP ↔ IP and TDM↔ IP modes simultaneously.
Customer-orderable SKUs are pre-populated with DSP physical resources to support calls that require media services. Depending upon the configuration, the SBC 1000 features up to three DSPs. The mapping of available DSP resources to available DSPs is presented in the following table:
DSPs to DSP Resource Mapping
Number of DSPs | Available DSP Resources |
---|---|
1 | 64 |
2 | 128 |
3 | 192 |
For the list of available customer-orderable SKUs and the number of DSPs within a given SKU, please contact your Ribbon sales representative, or refer to the Partner Configurator.
Follow these steps to determine the appropriate configuration and the number of DSPs required.
An SBC 1000 (release 6.1 and later hardware) supports up to 192 total calls . Point (d) in example 3 identifies the maximum simultaneous number of calls that are subject to DSP intervention; additional calls are supported when the SBC runs in direct media or RTP proxy mode.
In the case of RTP Proxy Mode (media pass-though), media passes through the SBC Edge but does not use DSP resources, as opposed to the DSP Mode.
There are several alternatives for DTMF calls:
DSP resource usage is unaffected within an SBC Edge product with an onboard Microsoft Skype for Business SBA or CCE. Sessions that originate from, or terminate to, the onboard SBA or CCE are treated by the SBC Edge as exactly equivalent to an off-board SBA or CCE application (analogous to a SIP server residing within its own physically separate processing environment). As such, these calls impose no requirements over and above a call to/from an off-board SIP entity.
The SBC Edge supports the SILK audio codec. Skype designates SILK as an internet wideband audio codec for use in VoIP. SILK operates at two different sampling rates: 8000 Hz narrowband and 16,000 Hz wideband (see the SILK Bandwith Options table). These rates allow for the capture of higher frequencies, which provide fuller sound, while also allowing interoperability with the Public Switched Telephone Network (PSTN). SILK has Low Bit Rate Redundancy (LBRR), also called Forward Error Correction (FEC), which protects the SBC Edge against packet loss. The network bit rate of SILK is adaptive within the range that the following table specifies. The SBC Edge defines and modifies the average network bit rate in real-time, while the actual bit rate depends on the input signal and change over time. The bit rate can dynamically change within that range. Since all other parameters are equal, the higher bit rates result in higher audio quality. SILK Bandwidth Options Narrowband WidebandAudio Bandwidth Frequency (Hz) Bit Rate (KBPS) Description 8000 6 - 20 16,000 8 - 30
The following table outlines the SBC 1000 SILK performance capacity. SBC 1000 SILK Performance Capacity SBC 1000, SIP entry model SBC-1K-R-SIP-E SBC 1000, SIP SBC-1K-R-SIP SBC 1000 with PRI SBC-1K-R-FXS8FXO-P, SBC-1K-R-P SBC 1000 with FXx, no PRI SBC-1K-R-FXSFXO, SBC-1K-R-FXS SBC 1000 gatewaysConfiguration (post-Release 6.1.x) Example SKU(s) Number of DSPs Number of Sessions, SILK NB <-> G.711 1 14 3 42 2 28 1 14 SBC-1K-R-4P-FXSFXO-GW 1 14
The following table outlines the SBC 1000 SILK codec combinations. SBC 1000 SILK Codec CombinationsNumber of DSPs Scenario Sessions Supported 1 DSP SILK-NB-G711U 14 1 DSP SILK-NB-G729 12 1 DSP SILK-NB-SILK-NB 11 1 DSP SILK-NB-SILK-WB 10 1 DSP SILK-WB-SILK-WB 6