Description – Intel Extensible Firmware Interface User Manual
Page 646
Extensible Firmware Interface Specification
15-40
12/01/02
Version 1.10
Table 15-1. PXE Tag Definitions for EFI (continued)
Tag Name
Tag #
Length
Data Field
Class Identifier
60 [0x3C]
32 [0x20]
"PXEClient:Arch:xxxxx:UNDI:yyyzzz"
"PXEClient
:
…" is used to identify communication between PXE
clients and servers. Information from tags 93 & 94 is embedded
in the Class Identifier string. (The strings defined in this tag are
case sensitive and must not be NULL-terminated.)
xxxxx = ASCII representation of Client System Architecture.
yyyzzz = ASCII representation of Client Network Interface
Identifier version numbers MajorVer(yyy) and MinorVer(zzz).
Example
"PXEClient
:
Arch
:
00002
:
UNDI
:
00300" identifies an IA64 PC w/
32/64-bit UNDI
Description
The basic mechanisms and flow for remote booting in EFI are identical to the remote boot
functionality described in detail in the PXE Specification. However, the actual execution
environment, linkage, and calling conventions are replaced and enhanced for the EFI environment.
The DHCP Option for the Client System Architecture is used to inform the DHCP server if the
client is an EFI environment in an IA-32 or Itanium-based system. The server may use this
information to provide default images if it does not have a specific boot profile for the client.
protocol is required to support the
protocol. The
LOAD_FILE_Protocol
protocol function
is used by the firmware to load files from devices that do not support file system
type accesses. Specifically, the firmware’s boot manager invokes
LoadFile()
with
BootPolicy
being
TRUE
when attempting to boot from the device. The firmware then loads and
transfers control to the downloaded PXE boot image. Once the remote image is successfully
loaded, it may utilize the
EFI_PXE_BASE_CODE
interfaces, or even the
interfaces, to continue the remote process.