The IEC admits that the multi-protocol standards are "not elegant to the standards purist", but argues that they meet the practical needs of industry, and have evolved to incorporate new technologies and features such as safety.

In developing the standards, the IEC adopted a new approach that "challenged the IEC structure of vertical product-centric technical committees", the Commission acknowledges. It adds, however, that the standards had to allow multiple devices of varying capabilities to be connected. They also had to meet a wide variety of specific application requirements, in a wide variety of industries.

"The IEC Fieldbus Standards have been a challenge for the IEC in that the technology goes across a whole range of technologies traditionally covered by different expert groups," explains Bernard Dumortier, secretary of the IEC’s 65C technical sub-committee, which deals with industrial networks. "It was the first system-type challenge to the previous automation product-centric approach within the IEC technical committee."

As well as profiles for real-time Ethernet protocols such as Profinet, EtherCat and Ethernet PowerLink, the new standards include other profiles that were not in previous editions, as well as profiles that allow fieldbuses to transmit safety-related data. The protocols covered include: Foundation Fieldbus; CIP; P-Net; WorldFIP; Interbus; CC-Link; Hart; Vnet/IP; TCnet; EPA; Modbus RTPS; and Sercos.

Another addition is the inclusion of basic guidance for installing communications networks in industrial premises. Dedicated sections of the standards for each bus technology establish which options in the basic guidance apply, and what extra guidance is needed.

The main publications are: IEC 61158, which specifies fieldbuses for industrial networks; IEC 61784, which specifies profiles for industrial communications networks; and IEC 61918, which covers the installation of communications networks in industrial premises.