Web Management Guide-R01

Table Of Contents
Chapter 13
| Basic Administration Protocols
Ethernet Ring Protection Switching
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request) message indicating they have no local request. When the RPL owner
receives an R-APS (NR) message it starts the Wait-To-Recover (WTR) timer. Once
WTR timer expires, the RPL owner blocks the RPL and transmits an R-APS (NR, RB -
ring blocked) message. Nodes receiving this message flush the forwarding
database and unblock their previously blocked ports. The ring is now returned to
Idle state.
Figure 308: ERPS Ring Components
Multi-ring/Ladder Network – ERPSv2 also supports multipoint-to-multipoint
connectivity within interconnected rings, called a “multi-ring/ladder network
topology. This arrangement consists of conjoined rings connected by one or more
interconnection points, and is based on the following criteria:
The R-APS channels are not shared across Ethernet Ring interconnections.
On each ring port, each traffic channel and each R-APS channel are controlled
(e.g., for blocking or flushing) by the Ethernet Ring Protection Control Process
(ERP Control Process) of only one ring.
Each Major Ring or Sub-Ring must have its own RPL.
Figure 309 on page 471 (Normal Condition) depicts an example of a multi-ring/
ladder network. If the network is in normal operating condition, the RPL owner
node of each ring blocks the transmission and reception of traffic over the RPL for
that ring. This figure presents the configuration when no failure exists on any ring
link.
In the figure for the Normal Condition there are two interconnected rings. Ring
ERP1 is composed of ring nodes A, B, C and D and the ring links between these
nodes. Ring ERP2 is composed of ring nodes C, D, E and F and the ring links C-to-F,
F-to-E, E-to-D. The ring link between D and C is used for traffic on rings ERP1 and
ERP2. On their own ERP2 ring links do not form a closed loop. A closed loop may be
formed by the ring links of ERP2 and the ring link between the interconnection
nodes that is controlled by ERP1. ERP2 is a sub-ring. Ring node A is the RPL owner
node for ERP1, and ring node E is the RPL owner node for ERP2. These ring nodes (A
and E) are responsible for blocking the traffic channel on the RPL for ERP1 and ERP2
respectively. There is no restriction on which ring link on an ring may be set as the
RPL. For example the RPL of ERP1 could be set as the link between ring node C and
D.
East Port
West Port
RPL Owner
CC Messages
RPL
x
CC Messages
(Idle State)