IEEE 1588 was not designed for modern enterprise computer networks and contains many hacks to make it sort of work. The standard also suffers from being overly explicit on some things and overly unspecific on others. One marker of the flawed process is that IEEE 1588 transparent clocks don’t really comply with Ethernet standards because they modify packets without changing the MAC address. So in 2012 the 802.1 and 1588 standards groups started discussing what could be done. The 1588 committee notes that the “intent” (and practice) violates OSI layering but that 1588 doesn’t “mandate” that intent! Oy vey.
Questions have been raised concerning an IEEE 1588-2008 Transparent Clock layer 2 bridge modifying the CorrectionField of Ethernet transported PTP frames without changing the Ethernet source MAC address. The question is if this operation is permitted by IEEE 802.1Q [1]. The original intent of the IEEE 1588-2008 standard was that a Transparent Clock will forward PTP event frames with no modifications except for the CorrectionField and FCS updates, however IEEE 1588-2008 does not mandate that.