<S,G> switching between I-PMSI and S-PMSI is not symmetrical (synchronized in time) on the active and the inactive UMH. While the active UMH attempts to switch an <S,G> between I-PMSI and S-PMSI, the active PMSI traffic rate arriving from the active UMH may be different from that arriving from the inactive UMH. This asymmetrical behavior can generate a premature switch from the active PMSI to the inactive PMSI.
The traffic rate delta can be set to account for this behavior. For example, if a 1080P channel uses 5 Mb/s, the traffic rate delta can be set to 15 Mb/s to avoid the switchover from the primary to the secondary PMSI if one or two 1080 <S,G>s are switched between I-PMSI and S-PMSI. This provides a 10 Mb/s tolerance of asymmetric traffic.