Introduction
This document describes how to calculate DSP (Digital Signal Processor) resource consumption for hardware that began shipping from
Unable to show "metadata-from": No such page "_space_variables"
as of November 2016. For DSP consumption associated with older versions of hardware, refer to the appropriate release documentation on the
Ribbon Documentation Portal.
Purpose
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
Unable to show "metadata-from": No such page "_space_variables"
to satisfy call deployment requirements.
How to Use This Guide
This guide is intended to be used by
Unable to show "metadata-from": No such page "_space_variables"
customers to help select a
Unable to show "metadata-from": No such page "_space_variables"
configuration instance that includes an appropriate quantity of DSP resources to support a given density of call sessions subject to DSP-related media intervention. The available
Unable to show "metadata-from": No such page "_space_variables"
configurations (i.e. "Partner Configurator"), which includes a description of embedded features and options (including DSP resources and supported I/O), is
available behind the partner portal.
Definitions and Terminology
Transcoding: The action taken by a DSP (Digital Signal Processor) within a physical
Unable to show "metadata-from": No such page "_space_variables"
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 fRTP). This is considered as the default transcoding scenario for SBC 2000 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 2000, 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 |
- This uplift requirement only applies for multiple low-bit-rate codecs (G.729ab, G.723.1, G.726, or T.38).
- The combination of a single low-bit rate codec with G.711 does not require an uplift.
- It is also important to design for the most DSP-intensive usage. If multiple codecs are used and the split among these codecs varies, be sure to calculate using the codec that is most DSP-intensive and then apply the 20% uplift.
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
Unable to show "metadata-from": No such page "_space_variables"
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
Unable to show "metadata-from": No such page "_space_variables"
is considered a session running in Direct Media mode. Sessions running in Direct Media mode do not use any
Unable to show "metadata-from": No such page "_space_variables"
media processing resources including DSP resources.
DSP Resource Consumption for the IP ↔ IP Operating Mode
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
Unable to show "metadata-from": No such page "_space_variables"
, between two SIP/RTP endpoints.
An
Unable to show "metadata-from": No such page "_space_variables"
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 2000 IP ↔ IP DSP Multiplication Factor (click to enlarge)
Note
Densities assume VAD on (60% silence during call), RTCP on, RFC2833 on, and 20 ms packet size for all codecs (except 30 ms for G.723.1), G.722.2 at 12.65 kbit/s, RTP (unless specified with SRTP).
DSP Resource Consumption for the TDM ↔ IP Operating Mode
The TDM ↔ IP operating mode is a bidirectional media session, anchored by the
Unable to show "metadata-from": No such page "_space_variables"
, 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 the following table.
TDM/Analog-to-DSP Resource Mapping
Interface | DSP Resources Required |
---|
24 FXS | 24 |
1 T1/E1 | 25 |
2 T1/E1 | 50 |
3 T1/E1 | 75 |
4 T1/E1 | 100 |
5 T1/E1 | 125 |
6 T1/E1 | 150 |
7 T1/E1 | 175 |
8 T1/E1 | 200 |
The preceding calculation scheme assumes VAD (Voice Activity Detection) 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
Unable to show "metadata-from": No such page "_space_variables"
can support both IP ↔ IP and TDM↔ IP modes simultaneously.
SBC 2000 Configurations and the DSP Resource-to-DSP SKU Mapping
Customer-orderable SKUs are pre-populated with DSP physical resources to support calls that require media services. Depending upon the configuration, the SBC 2000 features up to six 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 | 200 |
2 | 400 |
4 | 700 |
6 | 984 |
Expansion of DSP Resource capability is non-linear.
For the list of available customer-orderable SKUs and the number of DSPs within a given SKU, please contact your
Unable to show "metadata-from": No such page "_space_variables"
sales representative, or refer to the Partner Configurator.
Calculating DSP Resource Requirement
Follow these steps to determine the appropriate configuration and the number of DSPs required.
- Determine the number of IP ↔ IP sessions needed (taking into account future growth).
- Determine the IP ↔ IP DSP multiplication factor from Table 1.
- Multiply the IP ↔ IP session count with the multiplication factor to obtain the DSP resource requirement number.
- Repeat steps 1-3 for different IP ↔ IP session scenarios for use in this unit at a given time.
- Determine the number of TDM ↔ IP sessions .
- For simultaneous TDM and IP usage, add all DSP resources from steps 3 and 5; otherwise, pick the usage with the larger DSP resource requirement.
- If using multiple low-bit rate codecs, apply 20% uplift to the DSP resource requirement number calculated in step 6.
- Refer to the DSPs to DSP Resource Mapping table to determine the number of DSPs needed to support requirements.
- Select the specific customer-orderable SKU from the Partner Portal that includes adequate DSPs plus the required TDM/FXx interfaces.
Example 1 - Calculating the DSP resource requirements for a medium-density, IP ↔ IP and TDM ↔ IP deployment
- I need 200 IP ↔ IP sessions and 60 TDM ↔ IP sessions (TDM flows across 2 E1 ISDN Primary Rate Interface links).
- Regarding the IP ↔ IP sessions, I want to transcode from G.711 (SRTP) to/from G.729ab (RTP). My multiplication factor is 1.36, and as such my IP ↔ IP DSP resource requirement number is 200 * 1.36 = 272. Furthermore, no 20% uplift is required as we do not have multiple low bit rate codecs in the expected IP ↔ IP flows.
- Regarding the TDM ↔ IP flows, I also want 60 TDM to/from IP sessions, where the media on the IP legs will be encoded as G.729ab. From Table 2 , the DSP Resource Requirement number is 50.
- Simultaneous usage: total DSP resource requirement is 50 + 272 = 322.
- Based on the I can select any SBC 2000 customer-orderable SKU that features a minimum of 2 DSPs. You will also need an SBC-2K-CRD-T1E1 with 2 E1 ports enabled.
Example 2 - Calculating the DSP resource usage in a high-capacity, TDM ↔ IP deployment
- I need 480 TDM ↔ IP sessions (TDM flows across 16 E1 ISDN Primary Rate Interface links). No IP ↔IP sessions are required.
- Regarding the TDM ↔ IP flows, the media on the IP legs will be encoded as G.722.2(SRTP). From Table 2, the DSP Resource Requirement number for 8 E1s is 200; therefore, the DSP resource requirement number for 16 E1s is 400.
- Based on the DSPs to DSP Resource mapping table, I can select any SBC 2000 customer-orderable SKU that features a minimum of 2 DSPs. You will also need 2 SBC-2K-CRD-T1E1 cards with a total of 16 E1 ports enabled .
.
An SBC 2000 supports up to 600 total calls, regardless of the number of DSPs in the system. The DSP resource requirement identifies the minimum number of available DSPs required in the system to process media associated with a subset, or all, of the 600 total calls.
Considerations for DSP Mode versus RTP Proxy Mode
In the case of RTP Proxy Mode (media pass-though), media passes through the
Unable to show "metadata-from": No such page "_space_variables"
but does not use DSP resources, as opposed to the DSP Mode.
Considerations for FAX
Considerations for DTMF
There are several alternatives for DTMF calls:
DSP resource usage is unaffected within an
Unable to show "metadata-from": No such page "_space_variables"
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
Unable to show "metadata-from": No such page "_space_variables"
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.