Editing Preboot Execution Environment (section)

== Availability  ==
PXE was conceived considering several system architectures. The version 2.1 of the specification defined architecture identifiers for six system types, including [[IA-64]] and [[DEC Alpha]]. However, PXE v2.1 only completely covered [[IA-32]]. Despite this apparent lack of completeness Intel has recently decided to widely support PXE within the new [[UEFI]] specification extending the PXE functionality to all EFI/UEFI environments. 
Current Unified Extensible Firmware Interface Specification 2.4A, Section 21 Network Protocols — SNP, PXE, and BIS defines the protocols that provide access to network devices
while executing in the UEFI boot services environment. These protocols include the Simple Network Protocol (SNP), the PXE Base Code Protocol (PXE), and the Boot Integrity Services Protocol (BIS).<ref name="2_4_Errata_A">{{cite web
 | url = http://www.uefi.org/sites/default/files/resources/2_4_Errata_A.pdf
 | title = Unified Extensible Firmware Interface Specification
 | publisher = UEFI
 | date = 2013-12-02
 | access-date = 2014-04-04
}}</ref><ref name="Intel_UEFI_PXE_Boot_Performance_Analysis">{{cite web
 | url = https://uefidk.com/sites/default/files/Intel_UEFI_PXE_Boot_Performance_Analysis.pdf
 | title = UEFI PXE Boot Performance Analysis
 | publisher = Intel Corporation
 | date = 2014-02-02
 | access-date = 2014-04-04
 | archive-url = https://web.archive.org/web/20140808044632/https://uefidk.com/sites/default/files/Intel_UEFI_PXE_Boot_Performance_Analysis.pdf
 | archive-date = 2014-08-08
 | url-status = dead
 }}</ref>
Today in a PXE environment the client architecture detection is rarely based on the identifiers originally included with the PXE v2.1 specification. Instead, each computer that will be booting from the network should have set DHCP option 93 to indicate the client's architecture. This enables a PXE server to know (at boot time) the exact architecture of the client from the first network boot packet.{{Ref RFC|4578}}

With the advent of [[IPv6]], DHCP has evolved into [[DHCPv6]]; the need for options supporting PXE within the new DHCP protocol has been addressed in 2010.{{Ref RFC|5970}}

The original PXE client firmware extension was designed as an [[Option ROM]] for the IA-32 [[BIOS]], so a [[personal computer]] (PC) was originally made PXE-capable by installing a [[network interface controller]] (NIC) that provided a PXE Option ROM. Today the client PXE code is directly included within the NIC's own firmware or as part of the UEFI firmware on the motherboard.

Even when the original client PXE firmware has been written by Intel and always provided at no cost as a linkable IA32 [[Object code file format|object code format]] module included in their Product Development Kit (PDK), the open source world has produced over the years non-standard derivative projects like [[gPXE]]/[[iPXE]] offering their own ROMs. While Intel based ROMs have been implementing the client side of the PXE standard for more than 20 years some users were willing to trade extra features for stability and PXE standard conformance.<ref name="gPXE">{{cite web
 | url = http://etherboot.org/wiki/
 | title = Etherboot/gPXE Wiki
 | publisher = Etherboo.org
}}</ref>