• Incoming Path
• Outgoing Path

This section describes the incoming and outgoing paths of the signaling transferred from the IP network to the PSTN.

It refers to the path of boards through which signaling messages from the IP network are processed by the SG7000 and routed to the PSTN, as shown in Figure 1.

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• When the front board of the SEPU is the SBPU, the SEPU can be configured with only the SHPU or SLPU.

• When the front board of the SEPU is the SBPE, the SEPU can be configured with the SHPE.

This section takes the SBPU, the front board of the SEPU, for an example to describe the IP-PSTN signaling path.

Figure 1 IP -> PSTN signaling path
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Incoming Path

• The VIEB provides FE interfaces to receive IP packets on the M3UA, M2UA or M2PA link over IP, and performs physical layer message processing.

• The VIEB transfers signaling messages to the SBPI through the internal physical connection, as path (1) shown in Figure 1.

• Based on the local IP address, local SCTP port number, peer IP address and peer SCTP port number, the SBPI transfers signaling messages to the SBPU configured with the broadband connection through the internal network cable, as path (1) shown in Figure 1.

• The SBPU performs SCTP and upper layer protocol message processing on signaling messages.

Outgoing Path

• The SBPU analyzes the DPC and queries the route information. If the destination of the outgoing link is SLPU/SHPU on the same board, the SBPU transmits the user layer messages to the SLPU/SHPU on the same board, as path (2) shown in Figure 1. Otherwise, the SBPU sends the messages to the SBPU configured with the outgoing link. This SBPU transmits the user layer messages to the SLPU/SHPU on the same board, as path (3) shown in Figure 1.

• The SLPU/SHPU performs MTP2 message processing on the user layer messages, and then sends the processed signaling messages to the SEPU in the same slot through the internal highway cable.

• If the outgoing link is configured on the SEPU, the SEPU directly sends the MTP messages to the PSTN through the E1/T1 interface, as paths (2) and (3) shown in Figure 1. If the outgoing link is configured on other SEPU, the SEPU then sends the MTP messages to the destination SEPU through the H.110 bus. The destination SEPU sends the MTP messages to the PSTN through the E1/T1 interface, as path (4) shown in Figure 1.

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The two SEPUs referred in step 3 must be configured in the same frame. The SG7000 does not support transferring messages between two SEPUs in different frames.

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