Diagnostic Test
How do we confirm or suspect that my suboptimal throughput issue is indeed coming from the interface mismatch?
- Draw a network map.
- Write down link speed at each level
- Mark 10G/1G (or perhaps other interface mismatch e.g. N-BaseT/1G)
For example, below are real world examples in my home network where the issues turned out to be the high to low mismatch.
Internet speed
In my latest setup, Arris SurfBoard S33 modem to UDM Pro router are connected using 2.5 Gigabit Ethernet port on the modem to the 10G port on UDM Pro using a SFP+ 10GbE transceiver.
As for detail, I am not 100% certain actual link rate between the two. It may be 10G link just utilizing 2.5Gbps bandwidth or alternatively it maybe actually linking at 2.5G-BaseT rate. Since UDM Pro officially only supports 1G or 10G and Network controller reports 10G link, I assume the former. With this assumption, the I have two pathways between my modem and iMac: full 10G or 1G link between USW Pro 24 Gen 2 switch to iMac. Internet to the iMac i.e. download path have “high to low” mismatch indeed between these two.
Here indeed there is only a half throughput when 1G pathway is utilized despite the whole pathway should be capable of 940 Mbps.
LAN speed
For the local speed test, two paths (10G and 1G) between NAS and Pro 24 Gen 2 Switch exist. When 1 Gbps path is utilized whole path between access point to NAS utilize 1G. However, when 10G path is used there is high to low mismatch from USW Gen 2 switch to HD access point.
The speed test result indeed shows degradation of download speed when 10G pathway is utilized.