[UPDATE - with the answer (it was the carrier)]
A cascaded system, with
- a MAX HD2 IP67 (two cellular (Verizon) and one WAN (the Transit Duo) connection
- a MAX Transit Duo with two cellular (Verizon, Visible) connections
The HD2 IP67 has a SpeedFusion connection to a Balance 380 (HW6) hub employing all three connections (2xCellular, 1xWAN). The B380 is on a 1Gbps fiber connection (gotta love Sonic!)
The connection from the HD2 to the hub has a significantly longer latency across the MAX transit than directly through Verizon. Specifically, the MAX Transit seems to consistently add approx. 150ms to the connection latency (i.e., when the HD2->Verizon->B380 connection is about 50ms, the HD2->Transit->Verizon->B380 is about 200ms.
Is the additional 150ms latency introduced by the Transit the expected (and unavoidable) cost of the routing, or is there a way to reduce it? It is a given that the Transit will add some to the latency.
The Transit was employing a visible.com SIM card on one of the radios, Though visible.com is a Verizon MVNO its traffic has lower priority than Verizon’s own. An that seems to manifest as increased latency (besides the general possibility of being deprioritized).
Even when running at full speed (no congestion) visible.com traffic seems to suffer from a consistent 150ms (give or take) additional latency. Running back-to-back ping tests with a Verizon SIM card and a visible.com SIM card demonstrates the difference.
The ping tests were run on Verizon connections on Band 13, Transit Duo to Balance 380.