For folks jumping on saying "that's not a carrier thing". All comms are a carrier thing. Whether it's ETWS, SMS, or IP, it's going through the carrier, they process it, and they do extensive traffic management. Carriers absolutely can and will inspect, proxy, aggregate, and do anything else that will tease out another few % of "free" capacity.
[Edit:] All too real scenario: Carrier knows about particular IP addresses and ports used by alert service. Carrier makes provision for separate path for it. Carrier also tries to shave said provisioning to the bone, calculates a worst-case, and adds 5% capacity. Which doesn't get updated when that particular app gets a 6% boost in subscriptions. Back in the old days the traffic management folks would be on top if it, but that's all been outsourced...
[Edit:] All too real scenario: Carrier knows about particular IP addresses and ports used by alert service. Carrier makes provision for separate path for it. Carrier also tries to shave said provisioning to the bone, calculates a worst-case, and adds 5% capacity. Which doesn't get updated when that particular app gets a 6% boost in subscriptions. Back in the old days the traffic management folks would be on top if it, but that's all been outsourced...