Preboot Execution Environment

In computing, the Preboot eXecution Environment (PXE, sometimes pronounced as pixie) specification describes a standardized client-server environment that boots a software assembly, retrieved from a network, on PXE-enabled clients. On the client side it requires only a PXE-capable network interface controller (NIC), and uses a small set of industry-standard network protocols such as DHCP and TFTP.

The concept behind the PXE originated in the early days of protocols like BOOTP/DHCP/TFTP, and as of 2015^[update] it forms part of the Unified Extensible Firmware Interface (UEFI) standard. In modern data centers, PXE is the most frequent choice for operating system booting, installation and deployment.

Since the beginning of computer networks, there has been a persistent need for client systems which can boot appropriate software images, with appropriate configuration parameters, both retrieved at boot time from one or more network servers. This goal requires a client to use a set of pre-boot services, based on industry standard . Additionally, the Network Bootstrap Program (NBP) which is initially downloaded and run must be built using a client (the device to be bootstrapped via PXE) firmware layer providing a hardware independent standardized way to interact with the surrounding network booting environment. In this case the availability and subjection to standards are a key factor required to guarantee the network boot process system interoperability.

One of the first attempts in this regard was the Bootstrap Loading using TFTP standard RFC 906, published in 1984, which established the 1981 published (TFTP) standard RFC 783 to be used as the standard file transfer protocol for bootstrap loading. It was followed shortly after by the Bootstrap Protocol standard RFC 951 (BOOTP), published in 1985, which allowed a disk-less client machine to discover its own IP address, the address of a TFTP server, and the name of an NBP to be loaded into memory and executed. Difficulties on BOOTP implementation among other reasons eventually led to the development of the Dynamic Host Configuration Protocol standard RFC 2131 (DHCP) published in 1997. This pioneer TFTP/BOOTP/DHCP approach fell short because, at the time, it did not define the required standardized client side of the provisioning environment.

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