Mimosa A5x and C5x

I have a Mimosa A5x that has a C5x connected to it with Version installed on both. My problem is that I can’t get packets larger than 1.45mbps over them, any solutions that I can try please? I have looked to increase the MTU, but can’t find anywhere to do it.

Do you mean you can’t pass packets larger the 1450 bytes and this is a MTU problem or do you mean you cant pass more then 1.45 Mbps through the link and there is some sort of connectivity issue?

Not sure whether it is a MTU problem, have looked for where I can increase it but no luck. The connectivity is fine between the two units, according to the dashboard I should be able to pass 300mbps, but no such luck

Ok, so the problem is that you can’t pass more then 1.45 Mbps?

Your original post was unclear, but I am going to assume it’s a bandwidth question and roll from there…

How are you testing your bandwidth?

I have the radio’s connected to the PDU only and a laptop on the one end. I then run continuous pings with incrementing sizes to the radio at the far end.


Obviously we are talking past each other.

Let’s get some definitions out of the way so we are on the same page:
MTU: Maximum Transmission Unit, this is the largest size of packet that can be passed, the MTU of the internet is 1500 Bytes. Above that the packet will become fragmented.

Mbps: Mega bits per second, a measurement of how much data is being passed in a seconds worth of time.

Ping: A program that sends an ICMP packet (sometimes a UDP packet depending on the application) which carries a payload. You are probably setting the size of this payload with an argument and that’s where you are getting your 1450 number. An ICMP packet has more to it then the payload, source and destination addresses as well as a few other bits that are required for it to do it’s job. The stuff that is not the payload is referred to as the “headers” for ICMP the header size is variable, but for most simple pings it will be about 28 Bytes. This means that around 1472 byte sized packets, if you have the “Do not fragment flag” turned on you will see an error that says something along the lines of “Packet need to be fragmented but DF set” or the packet will be dropped with no notification.

You are trying to test the bandwidth of your link by sending individual ICMP packets across it, you will never get very far with this. Firstly, Mimosa radios put a really low priority on responding to pings, so if you blast a radio with a ton of ping messages not only will you possible kick off the firewall (which will block you from accessing the radio for 1 hour)

Now, yes it is possible to test bandwidth with pings, if you send enough of them, but that’s taking the hard route.

If you turn off the “Do not Fragment” flag you “should” be able to send packets that are significantly larger, but that doesn’t really help you. I would recommend looking into iPerf and setting up a server and client to test with, but that can be a bit complicated. A large file transfer can work as well, but then you are dealing with a lot of moving parts. If you have a fast enough internet connection you could use that and use something like DSLReports’ speed test, but again you have a lot of moving parts to keep track of. iPerf is the go to, even though it can be complicated to setup…