Notes and Limitations

IPv6 Requires additional configuration when Auto is Configured

When Auto is set as the Signaling/Media Source IP field (in the SIP Signaling Group facing the Front End Server/Skype Mediation Server), call scenarios using IPv6 are not being transferred correctly. Most cases include a Skype Mediation Server or Front End Server which invokes call transfer (REFER SIP msg) incoming to the SBC Edge.

As a result, the following additional configuration is required for the calls to transfer correctly.

Step 1: Add Number/Name Transformation Entry

Add a Transformation Table (if the FQDN of the Skype Mediation Server/Front End Server is set as a pool), that includes a wildcard regex expression for the FQDN configured on the Transformation table (to match all Skype Mediation Server/Front End Servers within the pool).

For example:

If the Skype Mediation Server/Front End Server FQDN is "lync-rdc2.njsbclab.dev",  then ".*lync-rdc2.njsbclab.dev.*" regex expression must be configured as the Transformation entry.

If multiple Skype Mediation Server/Front End Server FQDNs, (i.e, sfbfe1.sfb.tst, sfbfe2.sfb.tst, ….) are configured within a pool, then “.*sfbfe..sfb.tst.*” regex expression must be configured as the Transformation Entry.

Example Transformation Entry

Step 2: Add Call Routing Table

Add a Call Routing Table which includes the following:

Example Call Route

Lync E911 ELIN Support

Security desk conferencing with the emergency call in Unidirectional and Bidirectional mode is not supported.

ISDN

The Sonus SBC 1000/2000 rejects inbound BRI calls if the first channel is blocked.

CAS

• Transferred calls to a Busy FXO line will receive Ringback instead of Busy Tone.
• Silence based disconnect only checks for audio in one direction. For this reason a long timeout should be used

SIP

The following SIP features are not supported in the Sonus SBC 1000/2000:

• DTMF via SIP INFO messages.
• Privacy and Screening on Diversion number.
• REGISTER messages with multiple contacts do not use multiple Registrar licenses. Multiple licenses will be supported in a future release.
• Sonus SBC 1000/2000 does not switch to the next server in the table if connection re-use is enabled per the configured value, it always waits 5 seconds.
• Multiple M-Lines works for Audio/FAX/Image combinations only. If the Multiple M-Lines have multiple audio or audio + video, only the first m=audio is recognized.

RTP Proxy

RTP Proxy mode does not use SBC 1000/2000 DSP resources.  As a result, the following features are not supported in the Sonus SBC 1000/2000 when calls are operating in RTP Proxy mode;

• Ring-back generation
• Early 183
• Music on Hold
• Dead Call Detection
• QoE
• Call Transfers

Additionally, Sonus recommends the SMM message translation with SDP manipulation not be used when operating in RTP Proxy mode, as it may introduce offer/answer issues

Real Time Status View (Monitor tab)

A small number of SIP channels from the same SIP Signaling Group may show Out of Service in the Real Time Monitor view of the Sonus SBC 1000/2000. The channel status under the Settings tab shows them as OOS. The channels are actually in service. The issue is a display problem and does not affect calls.

The Monitor tab does not reload upon refreshing the browser or returning to the Monitor tab. This is only seen with Firefox 3.6.14 version, where Java applets load only once and do not reload in the same session when you return to the page. Details regarding this issue can be found in this Mozilla forum Q&A post. This problem has been fixed in Firefox version 3.6.15 and Sonus recommends upgrading from version 3.6.14. Internet Explorer (IE) and other supported versions of Firefox do not exhibit this issue.

Application Solution Module

When the Microsoft Windows is used on the ASM, the computer name cannot exceed the NetBIOS limit of 15 characters when it is set via the WebUI.

Music on Hold

The Sonus SBC 1000/2000 requires a reboot to switch from live music to file music on hold.

SNMP

In rare cases, the sym-snmp process restarts with a probable loss of SNMP traps sent during this interval of process restart during high volume periods of SNMP traps being sent from the SBC 1000/2000 to the management stations. This behavior is exhibited when the SBC 100/2000 is not licensed for Transcoding and is experiencing high call volumes (2-3 calls/sec). The node generates an alarm trap for failure to acquire a Transcoding license for attempted call.

Unsupported SNMP Counters

SIP/ISDN Counters

The following SNMP counters in the uxPortTable are unsupported:

• Blocked Calls (not supported for SIP)
• IngressBlockedCalls
• EgressBlockedCalls

Large MIB Table Retrievals

The retrieval of large MIB tables via SNMP during periods of heavy call volumes can result in call failures and failed SNMP requests. Tables in excess of 1000 rows when traffic exceeds 2 calls/second or tables in excess of 500 rows when traffic exceeds 4 calls/second are consider large.

Polling of these tables should be limited to a maximum frequency of once per 45 minute period. The SNMP timeout should be set between 60 and 120 seconds. Retries should be limited to a maximum of 5.

Transcoding between Tenor, Sonus SBC 1000/2000, and any SIP phone that sends a 180 without SDP

No audio is transmitted between the end points when any SIP phone that sends a 180 without SDP employes a G.711 A-Law codec and the Sonus SBC 1000/2000 uses G.711 µ-Law codecs as the secondary codec in the Media List configuration in the following network topology:

Inter-digit Timer Begins Early

The inter-digit timer is designed to begin after the DTMF tone is generated, however it currently begins before. This may result in an early timeout and could result in a mis-dialed number. To compensate, increase the inter-digit timer by the time equal to the duration of incoming MF/DTMF tones.

This issue will be addressed in a future release

Log Reload Functionality Limitation

The Reload button appearing in the bottom left-hand corner of the Local Logs page of the WebUI becomes inactive when the logfile exceeds 10 Megabytes in size. This is done to prevent the log file from overloading the browser.

Internet Explorer: Browser Limitation
The previous description not withstanding, Internet Explorer has an additional browser dependent limitation of 3MB. When the log file exceeds 3MB, IE disables the Reload button.

FXO Conference Calls

In the following specific scenario, ringback is heard by all parties when adding another extension to a conference call.

Scenario:

• The Loop Start Type in the CAS FXO Signaling Group is set to either Basic or Forward Disconnect.
• One member of a conference call attempts to call another extension and add it to the conference. The attempt originates from an FXS port, through Lync and outbound over an FXO port to a corresponding FXS port.

When this scenario is encountered all parties to the conference call hear the ringback tones. No ringback tone should be heard when attempting to add another party to a conference call.

This issue will be addressed in a future release.

No Progress Tone in Transfer Scenario

When a call is transferred and the target extension is busy, a fast busy tone should be heard. In the following scenario, only a normal ringback signal is heard until the call times out:

• The call is transferred out over an FXO port.
• The Loop Start Type in the FXO Profile is set to Reverse Battery.

This issue will be addressed in a future release.

Lync Server 2013 Does Not Support Reason Headers

When a forked call to Lync is answered elsewhere, the Sonus SBC automatically generates a SIP CANCEL (including a Reason header) to suppress Lync's missed call notification. However, the Microsoft Lync Server 2013 does not support receiving the Reason header from gateways. Without Microsoft support, there is no mechanism to suppress the missed call notification sent from Lync to Exchange.

Lync SBA versions require different Operating Systems

Due to a Microsoft requirement, specific SBA versions require different Operation Systems:

The Windows license that allows the SBC to run the latest SBA version is included at the time of shipment. In order reuse the same hardware, Sonus provides service packs that allow you to purchase additional Operating System licenses. As a result, you can receive an ASM license for one of the following:

• Windows Server 2012R2 by default to run Windows Server 2008R2
• Windows Server 2008R2 by default to run Windows Server 2012R2

The image that is based on a non-licensed Operating System will not be offered for re-initialization. If you are running a non-licensed OS, an alarm will be triggered. Ensure you are running a proper license for the ASM.

ASM Windows Server Support Specifications

An OS License is included at the time of shipment. To determine what OS was shipped, see below. If required, upgrade/downgrade packs for ASM images if needed are available for nodes that do not have the proper licensing for Windows 2008R2 or Windows 2012R2.

Downgrade Pack: Available for a node that needs Lync 2010 SBA but does not have a Windows Server 2008R2 license (see Skype for Business - Best Practice Downgrade to Lync 2010 SBA). Sonus will supply: 

• —A Microsoft Windows Server 2008R2 license (includes physical license label)
• —A Sonus license to use Windows Server 2008R2 (includes a feature activation key)
• —A Microsoft Lync 2010 SBA License (includes physical license label)

Upgrade Pack: Available for a node that needs Skype for Business 2015 SBA but does not have a Windows Server 2012R2 license (Skype for Business - Best Practice Upgrade to Skype for Business 2015 SBA). Sonus will supply:

• —A Microsoft Windows Server 2012R2 license (includes physical license label)
• —A Sonus license to use Windows Server 2012R2 (includes a feature activation key)
• A Skype for Business 2015 SBA License (includes physical license label)

—Perform the following to apply a downgrade/upgrade pack:

1. Obtain the upgrade/downgrade package from Sonus.
2. Apply the license. See Installing Licenses. See Attach License Label for attaching the label on the unit. 

Connected Name Feature Limitation

Lync/Skype for Business does not support the connected name feature.