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The shared port adapter (SPA) digital signal processor (DSP) is a single-width, half-height, high-power, SPA module that can be used across multiple Cisco platforms. The SPA DSP is designed for DSP-based voice and video solutions in the SPAs on the Cisco mid-range and high-end routers.
In Cisco IOS XE Release 3.2S, the following SPA DSP features have been deployed on the Cisco ASR 1000 Series Router for the session border controller (SBC):
Cisco Unified Border Element (SP Edition) was earlier known as Integrated Session Border Controller, and is referred to as SBC in this document.
For a complete description of the commands used in this chapter, refer to the Cisco Unified Border Element (SP Edition) Command Reference: Unified Model at http://www.cisco.com/en/US/docs/ios/sbc/command/reference/sbcu_book.html.
For information about all the Cisco IOS commands, use the Command Lookup Tool at http://tools.cisco.com/Support/CLILookup or the Cisco IOS master commands list.
Feature History of SPA DSP on the Cisco Unified Border Element (SP Edition)
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The SPA DSP onboard services were introduced on the Cisco ASR 1000 Series Routers. |
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The AMR-WB feature was supported on the SBC on the Cisco ASR 1000 Aggregation Services Routers. |
The following restrictions are applicable to a SPA DSP:
The DSP farm definition and SBC configuration and activation must be completed before transcoding the SBC calls. For more information about SPA configuration, see the “Configuring the Cisco DSP SPA for the ASR 1000 Series” chapter in Cisco ASR 1000 Series Aggregation Services Routers SIP and SPA Software Configuration Guide at:
http://www.cisco.com/en/US/docs/interfaces_modules/shared_port_adapters/configuration/ASR1000/asrcfgdsp.html
A SPA DSP contains digital signal processors and related hardware to provide voice transcoding capability for the SBC. In addition, Cisco Unified Border Element, Enterprise can use a SPA DSP for simple voice transcoding services.
You can find more information on terminating and generating the RTCP by the SPA-DSP at: http://www.cisco.com/en/US/docs/interfaces_modules/shared_port_adapters/configuration/ASR1000/ASRovdsp.html#wp1296621
SBC transcoding is used for codec translation between two VoIP networks as part of the Data Border Element (DBE) functions. Figure 41-1 shows how a SPA DSP performs codec transcoding for unified SBC and Figure 41-2 shows how a SPA DSP performs codec transcoding for distributed SBC.
Figure 41-1 SPA DSP Transcoding for Unified SBC
Figure 41-2 SPA DSP Transcoding for Distributed SBC
The SPA DSP allows the translation of one type of media stream or codec to another type of media stream that uses different media encoding and decoding technologies. Other translation activities include:
Transcoding is inferred from a Session Description Protocol (SDP) that is used to program a call. Programming terminations in the same call containing different codecs implicitly instruct the distributed SBC to perform transcoding.
Transrating is inferred from the SDP that is used to program a call. Programming terminations in the same call with different ptime implicitly instruct the distributed SBC to perform transrating.
Note Transrating is supported only for the different rates using the same codec, not across codecs. Therefore, transrating and transcoding cannot be performed simultaneously.
When an RTP packet is marked as DTMF using the telephone-event codec, the RTP packet is removed from the stream. The DBE sends an H.248 message to the signaling border element (SBE), indicating that a DTMF event has occurred, and that the RTP packet should be converted into a SIP DTMF event.
When an endpoint generates a SIP signal, the SIP DTMF signals arrive completely out of band. An endpoint that supports SIP DTMF generates the signals to be sent to the SBE. In turn, the SBE recognizes that this is a DTMF message and sends an H.248 message to the DBE, indicating that a DTMF tone is required to be inserted into the RTP stream. The DBE then inserts the RTP DTMF packets into the audio stream using telephone-event codec.
After the RTP packet is marked as DTMF using the telephone-event codec, the RTP packet is removed from the stream, and an RTP stream containing the DTMF waveform is sent to the other endpoint.
After the DTMF is sent as part of the voice waveform, the RTP packets are removed from the stream, and the DBE inserts the a new RTP packet with the payload-type telephone event into the audio stream.
After an endpoint generates a SIP signal, the SIP DTMF signals arrive completely out of band. The endpoint that supports SIP DTMF generates the signals to be sent to the SBE. In turn, the SBE recognizes that this is a DTMF message, and sends an H.248 message to the DBE, indicating that a DTMF tone is required to be inserted into the RTP stream. The DBE then inserts a stream containing the DTMF waveform.
When the DTMF is sent as part of the voice waveform, the RTP packets are removed from the stream, and the DBE sends an H.248 message to the SBE, indicating that a DTMF event has occurred, and that the RTP packets should be converted into a SIP DTMF event.
From Cisco IOS XE Release 3.3S, calls on a partially crashed SPA DSP can be recovered within the call outage time of 2.5s.
When part of a SPA DSP crashes, a crash recovery process runs, and then the RP reprograms the crashed part of the SPA DSP with all calls that were previously on it. For example, a simple transcoding scenario, a-law to u-law transcoding, can represent up to 129 calls that require reprogramming.
Depending on the part of the SPA DSP that crashes, the total recovery time may be longer because it might have to recover more components and also reprogram more calls. However, the entire media path outage time for all the recovered calls is less than 2.5s.
In all cases of the SPA DSP call recovery, the call recovery occurs on the same SPA DSP where the call existed prior to the crash. The calls are not moved to another SPA DSP.
The SPA DSP failure call recovery can be disabled or rendered ineffective if the SPA DSP crash dumps are enabled. It can push the call outage time beyond 2.5s.
The show voice dsp group all command indicates when a SPA DSP is undergoing call recovery.
Note The show voice dsp group all command displays the output HA State : DSP_HA_STATE_PENDING1 only during the recovery process which can be upto a few milliseconds.
Adaptive Multi-Rate Wideband (AMR-WB) is a patented speech coding standard based on Adaptive Multi-Rate encoding, using a methodology that is similar to the Algebraic code-excited linear prediction (ACELP). AMR-WB, which was specified by 3GPP, provides improved speech quality due to a wider speech bandwidth of 50 to 7000Hz compared to narrowband speech coders what are in general optimized for Plain old telephone service (POTS) wireline quality of 300 to 3400 Hz.
AMR-WB is codified as G.722.2, an ITU-T standard speech codec, formally known as Wideband coding of speech at around 16 kbps using AMR-WB. G.722.2 AMR-WB is the same codec as the 3GPP AMR-WB.
AMR-WB operates like AMR with nine different bit rates. The lowest bit rate providing excellent speech quality in a clean environment is 12.65 kbps. Higher bit rates are useful in background noise conditions and for music. Also, lower bit rates of 6.60 and 8.85 kbps provide reasonable quality, especially compared to narrowband codecs.
Note The AMR-WB feature requires DSP firmware with AMR-WB codec support.
Table 41-1 shows the relationship between the AMR rate mode and bit-rate.
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SID1 |
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This section describes the tasks to involved in configuring the SPA DSP services for the SBC:
Use the following procedure to set up the SPA DSP in the DSP farm mode for the DSP services:
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voice-card slot number/subslot number |
Specifies the slot number of the voice card and enters the voice card interface configuration mode. |
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For more information about configuring DSP farm services on a SPA DSP, see the “Configuring the Cisco DSP SPA for ASR 1000 Series” chapter in the Cisco ASR 1000 Series Aggregation Services Routers SIP and SPA Software Configuration Guide at:
http://www.cisco.com/en/US/docs/interfaces_modules/shared_port_adapters/configuration/ASR1000/asrcfgdsp.html
2. dspfarm profile profile-identifier {conference | mtp | transcode}
3. description profile-description-text
This section explains the various ways in which to configure the SBC for the SPA DSP voice card:
Association of the SBC to the DSP farm profiles is possible only after the corresponding DSP farm profile is created. Use the associate dspfarm profile command in the global configuration mode.
1. show dspfarm { all | dsp | profile}
This task configures the SBC for enabling the transcoding feature.
Note The caller and callee commands have been used in this procedure. In some scenarios, the branch command can be used as an alternative to the caller and callee command pair. The branch command has been introduced in Release 3.5.0. See the “Configuring Directed Nonlimiting CAC Policies” section for information about this command.
4. cac-policy-set policy-set-id
8. table-type limit list of limit tables
11. callee-codec-list list-name
12. caller-codec-list list-name
13. media police strip | reject | degrade
The following example shows an output of the show sbc sbe call-stats global current5min command that lists the count of the active transcoded and transrated calls.
Note Transrating is supported only for different rates using the same codec, not across codecs. Therefore, transrating and transcoding cannot be performed simultaneously.
This section describes how to enable transrating using either of the following methods:
This task configures the SBC for enabling the transrating using the same codec policy.
Note The caller and callee commands have been used in this procedure. In some scenarios, the branch command can be used as an alternative to the caller and callee command pair. The branch command has been introduced in Release 3.5.0. See the “Configuring Directed Nonlimiting CAC Policies” section for information about this command.
4. cac-policy-set policy-set-id
7. table-type {policy-set | limit {list of limit tables}}
9. cac-scope {list of scope options}
12. media police strip | reject | degrade
This task configures the SBC for enabling the transrating feature. This is an alternative mechanism to that described in the “Transrating Using the Same Codec Policy” section section for configuring transrating.
5. policy {minimum | transrating}
6. codec codec-name packetization-period packet-period [priority priority-value ]
Although Secure Real-time Transport Protocol (SRTP) is independent of transcoding, both can be configured to be used simultaneously.
This task configures the unified SBC to enable the SRTP and transcoding features.
Note The caller and callee commands have been used in this procedure. In some scenarios, the branch command can be used as an alternative to the caller and callee command pair. The branch command has been introduced in Release 3.5.0. See the “Configuring Directed Nonlimiting CAC Policies” section for information about this command.
4. cac-policy-set policy-set-id
7. table-type {policy-set | limit {list of limit tables}}
9. cac-scope {list of scope options}
11. srtp caller forbid | mandate | allow | prefer
12. srtp callee forbid | mandate | allow | prefer
13. srtp interworking forbid | allow
14. srtp media interworking forbid | allow
15. action next-table goto-table-name
19. table-type limit list of limit tables
22. callee-codec-list list-name
A SPA DSP can be used to detect the DTMF tones, called inband, that are played in the real-time transport protocol (RTP) stream. Inband DTMF interworking uses SPA DSP resources, and can be used for plain calls and transcoded calls.
Note The caller and callee commands have been used in this procedure. In some scenarios, the branch command can be used as an alternative to the caller and callee command pair. The branch command has been introduced in Release 3.5.0. See the “Configuring Directed Nonlimiting CAC Policies” section for information about this command.
4. cac-policy-set policy-set-id
7. table-type { policy-set | limit {list of limit tables}}
9. cac-scope {list of scope options}
10. callee inband-dtmf-mode always
11. caller inband-dtmf-mode never
12. action next-table goto-table-name
This section explains how to configure the Unified SBC to support AMR-WB.
2. dspfarm profile profile-identifier transcode
This section contains the following examples:
The following example shows how to enable DSP farm services on the SPA DSP:
The following example shows how to configure a DSP farm profile:
After a DSP farm profile is created, use the show command to display a DSP farm profile configuration and status. The following examples show the output of the show commands:
This section contains the following examples:
The following example shows how to associate the Unified SBC with a DSP farm profile:
The following example shows how to configure the unified SBC to enable transcoding.
Note The caller and callee commands have been used in this procedure. In some scenarios, the branch command can be used as an alternative to the caller and callee command pair. The branch command has been introduced in Release 3.5.0. See the “Configuring Directed Nonlimiting CAC Policies” section for information about this command.
Note Transrating is supported only for different rates using the same codec, not across codecs. Therefore, transrating and transcoding cannot be performed simultaneously.
The following example shows how to configure the unified SBC for enabling the transrating feature using the same codec policy:
The following example shows how to configure the Unified SBC for enabling the transrating feature using the same codec policy:
The following example shows how to configure SBC to enable the SRTP and transcoding features.
The following example shows how to configure the unified SBC for inband DTMF transmission.
Note The caller and callee commands have been used in this procedure. In some scenarios, the branch command can be used as an alternative to the caller and callee command pair. The branch command has been introduced in Release 3.5.0. See the “Configuring Directed Nonlimiting CAC Policies” section for information about this command.
The following example shows how to configure the Unified SBC to support AMR-WB: