Improve description of hardware network adapter

[sebastien-rosset]

What are you trying to achieve?

Improve the description of network adapter, which is currently defined as:

A physical network interface, or a network interface controller (NIC), excluding virtual adapters and loopbacks. Examples: an Ethernet adapter, an HBA, an fiber channel port or a Wi-Fi adapter.

https://github.com/open-telemetry/opentelemetry-specification/blob/main/specification/metrics/semantic_conventions/hardware-metrics.md#hwnetwork---network-adapter-metrics

What did you expect to see?

The definition excludes virtual adapters, which presumably refers to software-based network interfaces, such as virtual switches in a hypervisor or virtual interfaces in operating systems. That may have been implied, but since it's not explicit in the spec, that makes the spec ambiguous.

Many modern NICs (including smart NICs) have the ability to create virtualized network interfaces with hardware resources. The OS sees separate PCI devices. Since the whole section is about hardware, IMO network adapters should include adapters that are virtualized by the hardware.

Additional context.

Under common attributes, the spec states:

Physical system as opposed to a virtual system or a container. Examples: physical server, switch or disk array.

So presumably the network adapter metrics can be used for a server NIC, and also for Ethernet ports on switches, routers, firewalls, load balancers, etc. If that was the intent, it would be good to add examples in the description, because the name "network adapter" is seldom used for switches and routers. "Network adapter" tends to be used for hardware cards that are inserted in computers and appliances.

https://github.com/open-telemetry/opentelemetry-specification/blob/main/specification/metrics/semantic_conventions/hardware-metrics.md#hwhost---physical-host-metrics

Maybe the definition could be changed to:

A physical network interface, or a network interface controller (NIC), excluding software-based virtual adapters and loopbacks. For example, a physical network interface on a server, switch, router or firewall.