Difference between network card size and capacity

Jeff asked:

When I run lshw -C netowrk I get

       description: Ethernet interface
       product: Ethernet Connection (6) I219-V
       vendor: Intel Corporation
       physical id: 1f.6
       bus info: [email protected]:00:1f.6
       logical name: eno1
       version: 30
       serial: 1c:69:7a:0d:82:69
   --> size: 100Mbit/s         
   --> capacity: 1Gbit/s       
       width: 32 bits
       clock: 33MHz
       capabilities: pm msi bus_master cap_list ethernet physical tp 10bt 10bt-fd 100bt 100bt-fd 1000bt-fd autonegotiation
       configuration: autonegotiation=on broadcast=yes driver=e1000e driverversion=3.2.6-k duplex=full firmware=0.4-4 ip= latency=0 link=yes multicast=yes port=twisted pair speed=100Mbit/s
       resources: irq:133 memory:c0b00000-c0b1ffff

What’s the difference between size and capacity in this case?

My answer:

Those field names were intended for other types of hardware, and mapping them to network interfaces doesn’t make that much sense. That said, in this context, "capacity" is the maximum bandwidth of the NIC, while "size" is the current bandwidth.

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