What is the DATA_DELAY_INTERVAL?

The DATADELAYINTERVAL, also known as the S-PMSI data delay interval, is a configurable timer on the ingress (source) Provider Edge (PE) router in a Next-Generation Multicast VPN (NG-MVPN) environment. When a multicast source's traffic rate exceeds a configured threshold, the ingress PE decides to switch from the default Inclusive-PMSI (I-PMSI) to a more efficient Selective-PMSI (S-PMSI). The PE first signals the creation of the S-PMSI to other PEs. The DATADELAYINTERVAL is the period the ingress PE waits before it begins forwarding the multicast traffic onto the newly established S-PMSI. This delay is crucial to prevent traffic loss by allowing egress PEs sufficient time to join the new S-PMSI tree.

B. The source PE advertises the S-PMSI via an S-PMSI A-D route; it does not send MDT Join TLVs. MDT Join TLVs are sent by receiver PEs.

C. This describes a hold-down timer used when switching back from an S-PMSI to the I-PMSI to prevent flapping, which is a different function and parameter.

D. Pruning an S-PMSI is an action performed by a receiver PE when it no longer has local listeners for the stream; it is not controlled by this source PE timer.

1. IETF RFC 6514: BGP Encodings and Procedures for Multicast in MPLS/BGP IP VPNs.

Section 5.2, "Switching from I-PMSI to S-PMSI", Paragraph 2: "Before the ingress PE starts sending the C-multicast traffic on the S-PMSI, it MUST wait for a period of time sufficient for the S-PMSI to be established, so that the traffic is not lost. This time period is a configurable parameter. We will refer to it as the S-PMSI data delay interval."

DOI: https://doi.org/10.17487/RFC6514

2. Nokia 7750 SR OS Services Guide, Release 22.10.R1.

Section: NG-MVPN Configuration Overview, Data-MDTs: The documentation describes the data-delay command within the data-threshold context. It states: "This command configures the time the system waits before switching from the I-PMSI to an S-PMSI... This allows time for the S-PMSI to be set up to avoid packet loss." (The exact wording and section may vary slightly between releases, but the concept and parameter function are consistent).