Planet Networking & Communication SGS-5240 Series User Manual page 168

◆MEG Level – The maintenance entity group (MEG) level which provides a communication channel for ring automatic
protection switching (R-APS) information. (Range: 0-7) This parameter is used to ensure that received R-APS PDUs are
directed for this ring. A unique level should be configured for each local ring if there are many R-APS PDUs passing through this
switch.
◆Node ID – A MAC address unique to the ring node. The MAC address must be specified in the format xx-xx-xx-xx-xx-xx or
xxxxxxxxxxxx.
◆Node State – Refer to the parameters for the Show page.
◆West Port – Connects to next ring node to the west. Each node must be connected to two neighbors on the ring. For
convenience, the ports connected are referred to as east and west ports. Alternatively, the closest neighbor to the east should
be the next node in the ring in a clockwise direction, and the closest neighbor to the west should be the next node in the ring in a
counter-clockwise direction. Note that a ring port cannot be configured as a member of a spanning tree, a dynamic trunk, or a
static trunk. Once configured, this field shows the ring port for this node, and the interface state:

Blocking – The transmission and reception of traffic is blocked and the forwarding of R-APS messages is blocked,
but the transmission of locally generated R-APS messages is allowed and the reception of all R-APS messages is
allowed.

Forwarding – The transmission and reception of traffic is allowed; transmission, reception and forwarding of R-APS
messages is allowed.

Down – The interface is not linked up.
◆East Port – Connects to next ring node to the east.

Unknown – The interface is not in a known state.
◆RPL Port – If node is connected to the RPL, this shows by which interface.
◆RPL Owner – Configures a ring node to be the Ring Protection Link (RPL) owner.
◆Holdoff Timer – The hold-off timer is used to filter out intermittent link faults. Faults will only be reported to the ring protection
mechanism if this timer expires. (Range: 0-10000 milliseconds, in steps of 100 milliseconds) In order to coordinate timing of
protection switches at multiple layers, a hold-off timer may be required. Its purpose is to allow, for example, a server layer
protection switch to have a chance to fix the problem before switching at a client layer. When a new defect or more severe
defect occurs (new Signal Failure), this event will not be reported immediately to the protection switching mechanism if the
provisioned hold-off timer value is non-zero. Instead, the hold-off timer will be started. When the timer expires, whether a defect
still exists or not, the timer will be checked. If one does exist, that defect will be reported to the protection switching mechanism.
◆Guard Timer – The guard timer is used to prevent ring nodes from receiving outdated R-APS messages. During the duration
The reported defect need not be the same one that started the timer.
of the guard timer, all received R-APS messages are ignored by the ring protection control process, giving time for old
messages still circulating on the ring to expire. (Range: 10-2000 milliseconds, in steps of 10 milliseconds) The guard timer
duration should be greater than the maximum expected forwarding delay for an R-APS message to pass around the ring. A
side-effect of the guard timer is that during its duration, a node will be unaware of new or existing ring requests transmitted from
◆WTR Timer – The wait-to-restore timer is used to verify that the ring has stabilized before blocking the RPL after recovery
other nodes.
from a signal failure. (Range: 5-12 minutes) If the switch goes into ring protection state due to a signal failure, after the failure
condition is cleared, the RPL owner will start the wait-to-restore timer and wait until it expires to verify that the ring has stabilized
before blocking the RPL and returning to the Idle (normal operating) state.
◆Control VLAN – A dedicated VLAN used for sending and receiving E-APS protocol messages. (Range: 1-4093) Configure
one control VLAN for each ERPS ring. First create the VLAN to be used as the control VLAN, add the ring ports for the east and
west interface as tagged members to this VLAN, and then use this parameter to add it to the ring. The following restrictions are
recommended to avoid creating a loop in the network or other problems which may occur under some situations:

The Control VLAN must not be configured as a Layer 3 interface (with an IP address), a dynamic VLAN (with GVRP
enabled), nor as a private VLAN.

In addition, only ring ports may be added to the Control VLAN. No other ports can be members of this VLAN.
User's Manual of SGS-5240 Series Managed Switch
168