The PXE Specification (http://www.pix.net/software/pxeboot/archive/pxespec.pdf) specifies the following values for the client system architecture of the DHCP
0 = IA x86 PC(2)
1 = NEC/PC98(2)
2 = IA64 PC.(2)
3 = DEC Alpha (2)
4 = ArcX86 (2)
5 = Intel Lean Client (2)
While the list looks a bit dated, what do modern Architectures use for the Arch Field.
e.g. If I have a ARM Server or a RISC-V server and want to perform a PXE Boot what value should I provide for the ARCH Field?
From https://www.rfc-editor.org/rfc/rfc5970#section-6: "The following options have been assigned by the IANA from the option number space defined in Section 24 of the DHCPv6 RFC [RFC3315]."
So, I would suggest that https://www.iana.org/assignments/dhcpv6-parameters/dhcpv6-parameters.xhtml#processor-architecture is probably a good source.
Yes, this is DHCPv6, not DHCPv4, but no one appears to have cared enough to supersede rfc4578 with an updated version.
Having reached that conclusion, I peeked in UEFI 2.8. In Table 210. PXE Tag Definitions for EFI, the description for
Client System Architecture
is:That link in fact points to the IANA page again.