Can't break 20 Mbps

Hi guys,

I’ve got some PMP450 gear here in my office I’m learning. RF link capacity test 70/22 Mbps, VC 8X/6X. I’ve tested this on 12.1.3 and 12.2.2.

I cannot get more than 20 download Mbps with PPPoE. It might peak at 22 or so, but nowhere near even the “Link test with bridging and MIR” rate which is about 45 Mbps (bound by the SM’s CPU as I understand). On 12.1.3 using IP only, I saw a max of 31 Mbps. PPPoE on 12.1.3 was a similar story… max around 22 Mbps.

I’ve set my QoS stuff like I’m used to, everything is at high values. As far as I can tell there’s no reason I should be getting any less than 50 Mbps, certainly not less than the Link Test with Bridging and MIR value! I’ve even made sure to kill the broadcast/multicast allocation to 128 Kbps.

Any suggestions?


What size key do you have in the SM?

Size key? Not sure what you mean. The SM is optioned as Unlimited

I’m seeing the same thing. When running typical Internet speed tests, I see what you’re seeing. When I use iperf with multiple streams of data, I can consistently get about half what the link capacity test says is possible. I’m also running SMs with the unlimited license. I have been testing links with 100% efficiency with only test loads and the results are always the same: 50% of the downlink capacity. The uplink capacity seems to be fairly accurate.

I have gotten nowhere with Cambium support and I’ve been trying to get an answer for over a year. I gave up and thought to try this forum. It is my assumption that this limitation is by design, because it only affects PMP OFDM clients… which is both the 450 and 430 line-up. The fact that the PTP230 (same hardware/firmware as the PMP clients) does not have this issue, tells me the download limitation is controlled by the software. I would hope to have control over this using the QoS settings, but there is obviously something behind the scenes limiting this throughput.

I posted my own observations in a new thread before I saw this one:


It’s not just me then! I recall someone saying to me that the CPU in the SMs is a limitation in how much bandwidth it can punt but I figured this would at least match the “with bridging” test.

That was second-hand word-of-mouth from a Cambium CSE to a coworker. I also recall him saying that the underlying architecture is on a multi-core FPGA, and a future software release will allocate more resources to moving packets. I’ll see if I can get something a little more solid.

I responded to ncats in his other thread…

There are some packet processing limitations on the SM side of PMP 430 and PMP 450 systems.

We are indeed making improvements to this in an upcoming software release. Look for updates via our “Open Beta” software, which should be coming in the next week or so.

Also, I would encourage you to use the “newer” forums, located here:

These are far more actively monitored and responded to… (these forums are only being kept around for reference now).

Thanks for confirming.

You guys considering some sort of look for the “new forum”? It’s pretty hard to read and missing a lot of features. This venue has served your customers pretty well for the last decade or so.