HSR nodes have two ports and act as a bridge, which allows arranging them into a ring or meshed structure without dedicated switches.

This is in contrast to the companion standard Parallel Redundancy Protocol (PRP),[1] with which HSR shares the operating principle.

[2] PRP and HSR are suited for applications that request high availability and short switchover time.

[5] The cost of HSR is that nodes require hardware support (FPGA or ASIC) to forward or discard frames within microseconds.

In an HSR ring, only about half of the network bandwidth is available to applications for multicast traffic (compared to RSTP).

In practice, hardware support (FPGA) [8] is required to bring down the per-hop latency to a reasonable value (some 5μs at 100 Mbit/s), using cut-through switching.

IEC 62439-3 Annex C specifies a Precision Time Protocol Industry Profile (PIP L2P2P), that allows a clock synchronization down to an accuracy of 1 μs in a ring of 16 HSR nodes.

This PTP protocol also allows operating the HSR ring deterministically for a dedicated class of traffic, for instance Sampled Values in IEC 61850.

[9] Originally, the protocol was named HASAR for the initial of the five companies working for electrical utilities that created it (Hirschmann, ABB, Siemens, Alstom and RuggedCom).