Router (Transit Duo) introduces an additional 150 ms latency?

[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.

Probable cause:
The Transit was employing a SIM card on one of the radios, Though 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) 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 SIM card demonstrates the difference.

The ping tests were run on Verizon connections on Band 13, Transit Duo to Balance 380.

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May I know both cellular WANs of Transit are configured as priority 1? If so, please disable the Visible cellular WAN, ensure the cellular band of all cellular WANs from Transit and HD2 is identical then test again. Since the SpeedFusion tunnel is terminating between HD2 IP67 and B380, either of the cellular WAN from Transit will be used. Disable the Visible cellular WAN helps to force the SpeedFusion traffic to go through the Verizon cellular WAN to do the comparison.

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Both the modems (Visible on cellular 1, Verizon on cellular 2) are at priority 1. Whenever both are enabled equally then the speedfusion session makes use of cellular 1. Disabling 1 moved the speedfusion session to cellular 2 (as expected), but enabling cellular 1 brings the speedfusion session back to 1 - it does not stay with 2.

Since the speedfusion session from the HD2 is treated as just another connection from a LAN client to the internet by the Transit (I assume), I suppose creating an outbound policy that forces UDP from port 32015 or destination to port 4500 to go to cellular 2 and leave the secondary policy to be the default (e.g., balance, persistence, whatever) might force the speedfusion to alway be across cellular 2 and leave other traffic untouched?

You are correct.

Please create outbound policies to force destination ports TCP 32015, UDP 4500, and UDP 32015 to cellular 2. Ensure the newly added polices at the top of the outbound policy list.