OpenWrt 21.02.0 Fourth release candidate - DSA docs

[Arınç ÜNAL]

Hello Paul.

On 18/09/2021 15:36, Paul D wrote:
> On 2021-09-17 13:27, Perry wrote:
>> Hi all,
>>
>> On 9/17/21 1:30 PM, Rich Brown wrote:
>>> Hi Arınç
>>>
>>>> On Sep 17, 2021, at 3:17 AM, Arınç ÜNAL <arinc.unal at arinc9.com> wrote:
>>>>
>>>> The current naming used on LuCI/UCI is inaccurate and confusing. The 
>>>> “interfaces” under Network → Interfaces actually represent networks. 
>>>> The actual interfaces are called “device”.
>>>
>>> I agree that the terminology is confusing. I really struggled with 
>>> the names when I added them into the preface to the DSA Mini-tutorial 
>>> (https://openwrt.org/docs/guide-user/network/dsa/dsa-mini-tutorial). 
>>> I did some research looking at the original DSA documentation: it 
>>> didn't offer much in the way of definitions. So I followed my usual 
>>> practice of documenting the lingo of whatever application I'm using.
>>>
>>> After looking hard at how LuCI seemed to work, I wrote:
>>>
>>> --------
>>>     • Devices are physical connections that convey bits/frames to 
>>> other computers. They operate at layer 2 in the protocol stack, have 
>>> a MAC address along with several other configurable parameters...
>>>
>>>     • Interfaces route IP packets and operate at layer 3 in the 
>>> protocol stack. An interface is associated with a single device that 
>>> sends/receives its packets. Interfaces get their IP address 
>>> parameters by the choice of protocol...
>>> ---------
>>>
>>> I haven't heard any corrections from others about these assertions, 
>>> so I am hopeful that I got those definitions right.
>>>
>>> When you say that "interfaces... actually represent networks" I think 
>>> you mean that they're "subnets" (and have a subnet address range, IP 
>>> address, and other characteristics). Is that what you mean? Although 
>>> I'm neither a Linux OS or network expert, I can see an explanation 
>>> for using the terms "devices" and "interfaces" as defined above.
>>
>> This is not always the case.  For example, it is possible to have a tun
>> or tap interface which does not have a corresponding ip address.  This
>> is more than just a device, because layer 3 packets can arrive on such
>> an interface.
>>
>> Another example, from Freifunk, are mesh (either Ad-Hoc or 802.11s)
>> interfaces.  These are interfaces which have a static IP address, but
>> the netmask is 255.255.255.255.  This is not a network in the sense most
>> people are used to using, but still a completely valid configuration.
>>
>> I think staying with the terminology "device" and "interface" is the
>> right way to go.
>>
>> Greets,
>> Perry
>>
> 
> Largely agree -  device --> hardware device --> hwdev
> 
> interface ....? GUI is an interface. NIC is an interface. This is 
> abstract. Trying to make it concrete is just confusing. Specify:
> 
You're confusing the term "network interface" with others ("GUI 
interface" in this case). The term "interface", when used in computer 
networking, means that it's short for the term "network interface".

A Network Interface Card (NIC) is not a network interface by itself. The 
software creates a network interface that uses the NIC to connect to a 
network. Let's give swconfig & DSA as an example. A switch port is not a 
network interface by itself. Here's how DSA & swconfig make use of the 
switch ports;

- DSA would set up each switch port as a network interface. (wan, lan1, 
lan2, etc.)
- swconfig on the other hand would rather set up a vlan network 
interface to make use of the switch ports. (eth0.1, eth0.2, etc.)

When you run ip link, whether by Linux or Cisco's computer networking 
terms, what you see on each entry is a network interface. Network 
interfaces can be created by making use of physical devices (a NIC, a 
wireless radio) and/or logical features of the software (vlan, tunnelling).

> L3interface
> L4interface
> MLinterface (multi layer)
> 
Bridge interface, wireless interface, 802.1q vlan interface, veth 
interface, tunnel interface or the ones above... These are all called 
network interfaces in the most generic form.

Throughout LuCI, it can be seen that they're already called interfaces.

- wireless: Choose the network(s) you want to attach to this wireless 
interface
- (whilst choosing the interface for a network) Tunnel Interface, Alias 
Interface.

> 
> This terminology desperately needs disambiguating (just an observation, 
> not a criticism), at least away from single word terms.
> 
> But currently it seems to be:
> -device is the hardware
> -interface is hardware configured to operate at some network layer
> 
> 
> What do Linux (kernel) devs use?
> 
> 
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