On Sun, 29 Feb 2004, Christopher Aldridge wrote:
Is a USB Ethernet Adapter a "converter"? Personally, I say "no". My coworkers seem to say "yes".
I suspect the truth is that it is and it isnt... the complication being what you mean by terms like 'Ethernet' which comprises a number of standards across various layers of the OSI model.. also, does 'convertor' have a technical definition, I mean you plug ethernet in one side and USB in the other so there is obviously some sort of converting going on :) I'm not motivated enough to go thro all this email but just to expand on my point about ethernet, when you say ethernet you are talking about the cable, the rj45 plugs, the manchester encoding (it is manchester 4B5B isnt it?), the 802.x, 802.y (I forget), the llc, mac, framing, blah....... I suspect what the convertor does is take the frame, and send it out the USB in whatever format it needs to be data intact. Call this process what you like :) Steve
My argument:
1) Ethernet isnt "converted" to USB. The adapted information from the ethernet segment may traverse the USB segment if the NIC adapts it to the CPU, but is never "converted" to USB.
You can use USB for many things, thus making it an underlying "serial bus" in which other technologies can traverse.
Whatis.com definition: USB (Universal Serial Bus) is a plug-and-play interface between a computer and add-on devices (such as audio players, joysticks, keyboards, telephones, scanners, and printers). With USB, a new device can be added to your computer without having to add an adapter card or even having to turn the computer off.
USB in this scenario would be synonymous with PCI, in regards to the type of technology that interfaces with the cpu.
2) I cant seem to place "converter" above layer 1. Yet a Network adapter ( both PCI or USB ) have layer 2 mac addresses that are stored into the PROM from the manufactor. From my understanding, if an ethernet frame comes in via cat5, and is destined for the wrong MAC address, the traffic will not move up the OSI model and to the PC; It will be dropped right there and then. Only frames destined for the correct MAC or broadcast will traverse the USB portion. If this is true, then aparantly our "converter" is doing a lot more than "converting" ethernet to "USB"! - Filtering, forwarding, encapsulating, de-encapsulating, etc.
3) Just because a device has two physical mediums of connectivity, dosent make it a "converter". My coworkers argue that a USB Ethernet adapter is an "Ethernet to USB Converter". If this is true, then the following could be said:
a. A PCI Ethernet Adapter is a "converter" because it "converts" Ethernet to PCI.
b. An Alcatel switch w/ a T1 and a DS3 controller card would be a "converter" because it "converts" cat5 from the T1 card to coax on the DS3 card.
c. Lastly ( I love this one ), An integrated Ethernet adapter on a motherboard is a "converter" because it "converts" ethernet to uhh ?? processor? Riiiiight"
My co-workers arguments are basically that because Ethernet is plugged into one side, and usb is plugged into the other, it's a converter.
I strongly that's an understament if not an incorrect statement. Whats your take and why?
Input from ANY of you would be GREATLY appreciated. Otherwise, a simple "I aggree with you" will be fine also!
Thanks in advance!
Christopher Aldridge
Network Analyst
CCNA/MCP/MCSA