Dual-Homing Protocol (Dhp) - GE MiCOM P40 Agile Technical Manual

Chapter 5 - Operation
1
Switch
Hx5x
V01013
Figure 13: Redundant Ethernet ring architecture with IED, bay computer and Ethernet switches
1
Switch
Hx5x
V01014
Figure 14: Redundant Ethernet ring architecture with IED, bay computer and Ethernet switches after failure
3.5

DUAL-HOMING PROTOCOL (DHP)

Unlike RSTP, the GE DHP solution responds to the constraints of critical time applications such as the GOOSE
messaging of IEC 61850.
DHP is applied to double-star network topologies. If the optical fibre connection between two devices is broken,
the network continues to operate correctly.
The Dual Homing Manager (DHM) handles topologies where a device is connected to two independent networks,
one being the "main" path, the other being the "backup" path. Both are active at the same time.
In sending mode, packets from the device are sent by the DHM to the two networks. In receive mode, the duplicate
discard principle is used. This means that when both links are up, the MiCOM Alstom H16x switch receives the
same Ethernet frame twice. The DHM transmits the first frame received to upper layers for processing, and the
second frame is discarded. If one link is down, the frame is sent through the link, received by the device, and
passed to upper layers for processing.
GE's DHM fulfils automation requirements by delivering a very fast recovery time for the entire network (less than 1
ms).
To increase reliability some specific mechanisms are used:
Each frame carries a sequence number which is incremented and inserted into both frames.
●
Specific frames are used to synchronize the discard mechanism.
●
66
2 3
Rx (Ep) Tx (Ep)
A B
Tx (Es) Rx (Rs)
IED
2 3
Rx (Ep) Tx (Ep)
A B
Tx (Es) Rx (Rs)
IED
Primary Fibre
1 2 3
Switch
C D
C264 IED
Secondary Fibre
Primary Fibre
1 2 3
Switch
C D
C264 IED
Secondary Fibre
1 2 3
Switch
E
Hx5x
1 2 3
Switch
E
Hx5x
Px4x-REB-TM-EN-6