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ICE-Lite Overview

The ICE-Lite (Interactive Connection Establishment) feature interfaces to the Microsoft TEAMS Direct Routing interface. The SBC integrates Microsoft Teams clients by acting as an ICE Lite agent endpoint for SIP calls involving Network Address Translators (NATs). This feature enables direct routing between an existing enterprise voice infrastructure (that is, the PSTN carrier and SIP trunks used for trunking services) and the Microsoft Phone System in Office 365. The SBC acts as a PSTN gateway; sessions for Microsoft Teams users can be routed directly to the PSTN through the SBC.

How does the SBC interoperate with Microsoft TEAMS?

As communications sessions are set up and negotiated, Session Description Protocol (SDP) is used to carry the IP addresses and ports of all participants that receive RTP streams. Because Network Address Translators (NATs) alter IP addresses and ports, the exchange of local IP addresses and ports may not be sufficient for establishing connectivity. Acting as an ICE-Lite agent, the SBC Edge responds to connectivity checks as required to establish and verify connectivity.

A Teams client initiates the media flow and becomes the controlling ICE agent for the SBC. During the establishment of a media session that uses ICE-Lite, the SBC Edge goes through candidate gathering and connectivity check phases that occur before the controlling agent (optionally) sends a final SDP offer that includes the best local and remote candidates selected for a media flow. The SBC Edge, acting as ICE-Lite agent, acknowledges the final offer with an answer, and both endpoints use the selected candidate pair for the media flow.

Configuration

Configuration for ICE-Lite is completed through the SIP Signaling Group.

For detailed configuration for using ICE-Lite with Microsoft TEAMS, refer to Microsoft Teams Direct Routing - On Premises Deployment.

For details on ICE-Lite configuration, refer to Creating and Modifying SIP Signaling Groups.

The screen shot below is for an SBC 2000.

Figure : SIP Signaling Group - ICE-Lite Configuration

The following fields must be configured to enable the ICE-Lite feature:

ICE Support

Table : ICE Support - Field Definition

FieldLocationDefinition
ICE SupportSettings > SIP Signaling GroupEnables/disables ICE support. This field must be enabled for ICE-Lite to be active.

ICE Mode

Table : ICE Mode - Field Definition

FieldLocationRecommended Configuration
ICE ModeSettings > SIP Signaling Group

Specifies the Interactive Connection Establishment (ICE) mode.

Valid entries:

For SBC 1000/2000: Lite or Full. To access the ICE-Lite feature, set this field to Lite.

For SBC SWe Lite: This field is configured as Lite automatically when ICE support is Enabled.

Interoperability Notes

ICE-Lite impacts the following on the SBC 1000/2000 and SBC SWe Lite.

SBC FeatureSupportsDoes not Support

ICE Restarts

The SBC Edge does not support ICE restarts as required to change the destination of a data stream.

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TURN server operation

The SBC Edge does not support TURN server operation. With some topologies the ICE protocol may require use of a TURN server to traverse a NAT on the SBC Edge side; the
the SBC is unable to establish connectivity between endpoints in such scenarios.

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STUN Server Operation with Full ICE Mode Only

The SBC Edge supports STUN server operation for gathering candidates only when the ICE Mode is Full, not with the Lite ICE Mode.

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Internet Connection Using UDP Candidate

As an ICE-Lite agent (controlled agent only) , the SBC Edge connects to the public Internet using a single host UDP candidate.

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RTP and RTCP Media

The SBC Edge supports Real-Time Transport Protocol (RTP) and Real-Time Transport Control Protocol (RTCP) as two separate components for each candidate unless data streams are multiplexed on the same port.

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Ports for RTP and RTCP

The SBC Edge supports sending and receiving RTP and RTCP on nonconsecutive ports for the SBC 1000/2000and the SBC SWe Lite.

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IPv4 Support Only

As an ICE-Lite agent, the SBC Edge connects to the public IP address using a single IPv4 address.

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