6.2.22 WebRTC

23.3343GPPIP Multimedia Subsystem (IMS) Application Level Gateway (IMS-ALG) - IMS Access Gateway (IMS-AGW) interface: Procedures descriptionsRelease 17TS

6.2.22.1 Establishment of a WebRTC data channel

See clause 6.2.10.6.2.

6.2.22.2 Release of a WebRTC data channel

The H.248 Context model for a WebRTC call in figure 6.2.10.6.2.1 is assumed. However, the example flow in this clause focuses on the WebRTC data channel part only. Thus, only H.248 Streams S1 (for de-aggregation of multiple data channels) and S2 (for MSRP traffic) are indicated subsequently.

Figure 6.2.22.2.1 shows the message sequence chart example for the WIC originated procedure to release a WebRTC MSRP data channel following the procedures in clause 5.20.2.3.2.

Figure 6.2.22.2.1: Call flow for the Release of a single WebRTC data channel

NOTE: Steps 9, 10, 13 and 14: A data channel is constituted by a pair of unidirectional SCTP Streams (with the same SCTP Stream identifier value in above flow). The SCTP Outgoing SSN Reset Request procedure does reset a single SCTP Stream only (due to the configuration in this example), hence the procedure will be executed twice (towards and from remote WIC).

6.2.22.3 Media Plane Optimization

6.2.22.3.1 Media Plane Optimization including DTLS layer for WIC originating call

The H.248 Context model for a WebRTC call in figure 6.2.10.6.2.1 is assumed. However, the example flow in this clause focuses on the WebRTC data channel part only. Thus, only H.248 Streams S1 (for de-aggregation of multiple data channels) and S2 (for MSRP traffic) are indicated subsequently.

Figure 6.2.22.3.1.1 shows the message sequence chart example for the WIC originated procedure to establish a WebRTC data channel with media plane optimization following the procedures in clause 5.20.3.2.

NOTE: Message 16 (DTLS ClientHello) can be received by the eIMS-AGW from the remote peer before the eIMS-AGW is configured to pass it (in steps 8.-13.) and will then be dropped by the eIMS-AGW. However, the remote peer will then resend message 16 after a timeout while waiting for a response.

Figure 6.2.22.3.1.1: WIC originated procedure for WebRTC data channel establishment with media plane optimization including DTLS layer

6.2.22.3.2 Media Plane Optimization excluding DTLS layer for WIC originating call

The H.248 Context model for a WebRTC call in figure 6.2.10.6.2.1 is assumed. However, the example flow in this clause focuses on the WebRTC data channel part only. Thus, only H.248 Streams S1 (for de-aggregation of multiple data channels) and S2 (for MSRP traffic) are indicated subsequently. Furthermore, there is an additional termination T3 towards the IMS core network to handle DTLS.

Figure 6.2.22.3.2.1 shows the message sequence chart example for the WIC originated procedure to establish a WebRTC data channel with media plane optimization following the procedures in clause 5.20.3.2.

Figure 6.2.22.3.2.1: WIC originated procedure for WebRTC data channel establishment with media plane optimization excluding DTLS layer