Member Avatar for ElieM

I'll make it more clear.

a network card is unique in the whole world by it's mac address.
the mac is unique in the world, unless it's cloned.

what's similar to mac in usb that makes it unique?

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  • Latest Post Latest Post by whipaway

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Brief answer grounded in the thread: asked for a single criterion that makes a USB port globally unique. As and observed, the USB architecture does not give a physical receptacle a world-wide, vendor-assigned serial like an IEEE MAC. Instead, uniqueness is a function you build from local pieces (host identity + controller + hub/port path) or you rely on identifiers provided by the device plugged into the port.

A practical way to make a reproducible, globally unique identifier for "this physical socket on that machine" is to concatenate three things: (1) a stable host identifier (SMBIOS/DMI UUID or system serial), (2) the host controller identification (PCI slot or HCI instance), and (3) the USB topology path from root hub to port (the hub+port sequence the kernel reports, e.g. the "1-2.3" style sysfs name). On Linux you can inspect topology and host UUID with tools in sysfs and udev; on Windows use the device instance/ContainerID and the system UUID exposed by WMI. Be aware this composite ID is only stable while the machine and controller layout remain unchanged.

Quick examples (Linux):

cat /sys/class/dmi/id/product_uuid
lsusb -t
udevadm info -q path -n /dev/bus/usb/002/003

Notes and cautions: many devices do not expose unique serial strings, some vendor tools set identical serials, and system DMI UUIDs are sometimes missing or duplicated on cheap hardware. Also moving a hub or adding PCI controllers will change port paths, so a per-host composite is much more reliable than trying to find any single, universal “port ID.”

Further reading: USB overview and descriptors at the USB-IF site and Linux kernel USB/sysfs docs; Windows device instance and ContainerID guidance on Microsoft Docs.

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Member Avatar for Xlphos

Hello,

I don't think there is any unique identifier for USB ports, there isn't a need for it. MAC addresses are used for effective communication. USB ports are usually for transfer of data in some way; the source and destination address is obvious, there is no need for the USB port to be unique.

Member Avatar for whipaway

There is no need for the USB port to be unique, the same way a parallel or serial port has no unique identifier.
A device attached to USB port, however, such as webcam, may have its serial number available for access, or a WIFI dongle have its MAC address, etc available.

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