Epsr And Spanning Tree Operation - Allied Telesis AT-8600 Release Note

Ethernet Protection Switching Ring (EPSR)

EPSR and Spanning Tree Operation

EPSR and the Spanning Tree protocols (STP) each address the issue of data
loop prevention, although their method of doing so is quite different. For
information on STP, see the Spanning Tree Chapter of your switch's Software
Refernce. EPSR is manually configured to explicitly identify which link(s) will
be broken in the defined ring, whereas STP/RSTP calculates where to break
links based upon user provisioned values (metrics) that are compared to
determine the "best" (or lowest cost) paths for data traffic.
At the practical level these two techniques can be employed to create
complementary hybrid EPSR / STP configurations. Such a configuration might
have a high speed fibre loop topology backbone—controlled and managed
using EPSR. Lobes could extend out from each loop node into a user mesh
network. Any loops existing within this mesh network would be controlled
and managed using STP/RSTP.
combined EPSR / STP network.
Figure 1-9: EPSR and Spanning Tree Operation
Secondary
Other
Ports
Node 2
Port 1
Other
Ports
Control VLAN (control_ring)
Note that EPSR and STP cannot share the same ports.
Figure 1-9 on page 1-13
Port 2
Other
Ports
S P
Node 1
Master
Node
Transit
EPSR Ring
Node
Transit
Port 1
Node
Port 4 Node 3
STP/RSTP
Network
Data VLAN
Port 2 Port 2
Data VLAN
shows a basic
Port 1
Primary
Transit
Other
Ports
Node
Node 4
Port 2
Port 3
Port 1
Other
Ports
13
EPSR 5.eps