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Step 5
Step 6
Automatic Protection Switching on the PXM
Automatic Protection Switching (APS) provides redundancy for an OC-3 or OC-12 line on the PXM
if a failure occurs someplace other than the PXM front card. The failure can originate on the daughter
card, uplink card, or any part of the physical line. With APS, the active PXM remains active and
passes the cells from the failed line-path through the redundant line. The advantage of APS is that a
line switchover requires significantly less time than a full PXM switchover. (A failure of the PXM
front card in a redundant system causes the entire PXM card set to switch over.) As defined in
GR-253, a variety of APS modalities are possible (see the command summaries that follow).
The current requirements for APS service on an MGX 8850 switch are:
•
Redundant PXMs (currently, the PXM does not support an APS configuration where the working
and protection lines on the same uplink card).
•
A "B" version of an OC-3 or OC-12 back card (SMLR-1-622/B, and so on).
•
The connected network switch or CPE must also support APS.
Using an example of 100% of the bandwidth on one logical port 1:
addport 1 1 100 1 200
where the first "1" is the logical port number; the second "1" is the line number on the
PXM back card to which you are assigning this logical port number; "100" is the
percentage of bandwidth this port has in both directions; and the VPI range is 1–200.
If necessary, use cnfportrscprtn to modify port-level resources for a controller:
cnfportrscprtn <port_no> <controller> <ingress_%BW> <egress_%BW>
•
<min_VPI> <max_VPI> <min_VCI> <max_VCI> <max_GLCNs>
•
port_no is the logical port number in the range 1–32 for user-connections or 34 for
inband ATM PVCs for network management.
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controller is a string identifying the network controller—"PAR," "PNNI," or "TAG."
•
ingress_%BW is the percentage of ingress bandwidth in the range 0–100.
•
egress_%BW is the percentage of egress bandwidth in the range 0–100.
•
min_vpi is the minimum VPI in the range 0–4095.
•
max_vpi is the maximum VPI in the range 0–4095.
•
min_vci is the minimum VCI in the range 0–65535.
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max_vci is the maximum VCI in the range 0–65535.
•
max_chans is the maximum GLCNS in the range 0–32767.
On a stand-alone node, specify the cell header type as needed by executing cnfatmln.
cnfatmln <line_num> <type>
•
line_num is the line number in the range 1–4.
•
type is either 2 for UNI or 3 for NNI (the default).
UNI cell headers typically apply where a workstation connects through a line to a PXM
UNI port (rather than a SLIP-based port on the PXM-UI card). Such an implementation
is not common, so cnfatmln usually is not necessary.
Automatic Protection Switching on the PXM
Card and Service Configuration 6-7
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