Global Documentation
H38x/EN GL/D11
DS Agile H38x
Page 13/53
3. FUNCTIONAL
DESCRIPTION
The H38x enables Ethernet equipped devices to connect via a Parallel Redundancy Protocol
(PRP in accordance with IEC 62439-3). Devices connect to the switch by electrical
connections using RJ45 connectors. These connections comply with 10/100Base-Tx. Three
ports are provided. Each port, independently, detects the speed of the connected device
(10Mbps or 100Mbps) and whether the link is half-duplex or full-duplex. It then automatically
adjusts the port configuration to suit.
Electrical Ethernet links are limited in distance and subject to interference. You should keep
them as short as possible.
The Parallel Redundancy Protocol connection uses fibre-optic inter-switch connections. A
multi-mode fibre-optic version is available for short distance connections (typically up to
around 2km), and a single-mode version is available for longer distances (potentially in
excess of 15km). The PRP ports support 100Base-Fx using LC connectors.
Providing Ethernet redundancy, the product can be described as a redundancy box, called a
“RedBox”.
The product also supports Network Time Protocol (NTP), as well as the Precision Time
Protocol (PTP in accordance with IEEE 1588 v2), to provide real-time synchronisation.
The figure below shows the main functional blocks of the product.
FIGURE 1: DS AGILE H38X FUNCTIONAL DIAGRAM
3.1
Parallel Redundancy Protocol (PRP)
The Parallel Redundancy Protocol (PRP) is implemented according to the definition in the
standard IEC 62439-3.
PRP allows seamless (sometimes called “bumpless”) communication in the face of a single
network disruption (for instance cable, driver, switch or controller failure).
A PRP compatible device has two ports operating in parallel, each port being connected to a
separate local area network (LAN) segment. IEC62439-3 assigns the term DANP (Doubly
Attached Node running PRP) to such devices. Critical devices should be doubly attached
using two ports.
