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Overview

In a SIP-In-Core deployment, the SBC(s) process the 3xx response message as described below:

If a 3xx is received at the ingress SBC, it is processed at the ingress SBC.

If a 3xx is received at the egress SBC, the egress SBC handles the 3xx local redirection and the light dip to the PSX. If a heavy weight PSX dip is required, the egress SBC sends the 3xx message to the ingress SBC. The ingress SBC performs a heavy weight PSX dip with the Contact header information.

Note

For configuring SIP-In-Core, refer to Configuring SBC to use SIP in the Ribbon IP Core.

For details on using the Force Re-query for Redirection flag refer to, Redirect - Flags.

While handling 3xx at the egress SBC, the egress SBC sends 18x to the ingress SBC. However, in a SIP-In-Core setup, ensure the egress SBC does not send the 18x to the ingress SBC. Block it by enabling the following configuration at the egress TG of the egress SBC. The ingress SBC generates the 18x towards the ingress peer. Refer to SIP Trunk Group - Services - CLI, for details.

set addressContext <addressContext> zone <egress_zone> sipTrunkGroup <egress_TG> services blockProgressOn3XXResponse enabled

Use the relay "Status Code 3xx" flag only to relay a 3xx from an egress peer to an ingress peer. That is, use the "Status Code 3xx" flag when 3xx responses are not processed at either the egress or ingress SBC.

Examples

When a 3xx is received at the ingress SBC, it is processed at the ingress SBC itself. Therefore, the examples below describe the scenarios when the 3xx is received at the egress SBC.

Force Re-query flag is disabled and 3xx Contact has peer IP – Contact: sip:userinfo@peerIP:port

When the Force Re-query for Redirection flag is disabled at the egress TG of the egress SBC and the 3xx Contact is of the format userinfo@peerIP:port. The 3xx is handled as follows:

The egress SBC does local redirection and sends an INVITE to the peer IP. The egress SBC does not dip the PSX.

Force Re-query flag is disabled and 3xx Contact has SBC SIP Sigport IP – Contact: sip:userinfo@sbcSIPSigIP:port

When the Force Re-query for Redirection flag is disabled at the egress TG of the egress SBC and the 3xx Contact is of the format userinfo@sbcSIPSigIP:port. The 3xx is handled as follows:

The egress SBC sends the 3xx to the ingress SBC since a heavy weight PSX dip is required.

The ingress SBC does a heavy weight PSX dip with the contact information received in the 3xx. Based on the routes received from the PSX, the ingress SBC sends the INVITE towards an egress SBC, or directly to a peer.

Force Re-query flag is enabled and 3xx Contact has peer IP – Contact: sip:userinfo@peerIP:port

When the Force Re-query for Redirection flag is enabled at the egress TG of the egress SBC and the 3xx Contact is of the format userinfo@peerIP:port. The 3xx is handled as follows:

The egress SBC does a TRM lookup for the peer IP. If the TRM lookup returns a trunk group, the egress SBC passes the trunk group as a DTG in the light weight PSX dip. If the TRM lookup does not return a trunk group, the egress SBC sends the 3xx to the ingress SBC for a heavy weight PSX dip.

The ingress SBC does a heavy weight PSX dip with the contact information received in the 3xx. Based on the routes received from the PSX, the ingress SBC sends the INVITE towards an egress SBC, or directly to a peer.

Force Re-query flag is enabled and 3xx Contact has SBC SIP Sigport IP – Contact: sip:userinfo@sbcSIPSigIP:port

When the Force Re-query for Redirection flag is enabled at the egress TG of the egress SBC and the 3xx Contact is of the format userinfo@sbcSIPSigIP:port. The 3xx is handled as follows:

The egress SBC sends the 3xx to the ingress SBC since a heavy weight PSX dip is required.

The ingress SBC does a heavy weight PSX dip with the contact information received in the 3xx. Based on the routes received from the PSX, the ingress SBC sends the INVITE towards an egress SBC, or directly to a peer.