Bundle Failover Between CTP Devices at Both the Local and Remote
Site Overview
You can use Y cables at both the local and
remote sites to provide a redundant path for bundles. As shown in Figure 1, you use a Y cable to connect two CTP
devices to the customer equipment (CE) at both sites. You then create
a primary bundle between one pair of CTP devices, and you create a
backup bundle between a second pair of CTP devices.
Figure 1: Y-Cable Redundancy at Both the
Local and Remote Sites
How Bundle Failover Between CTP Devices at Both the Local and
Remote Sites Works
Under normal conditions, both the primary and backup bundles
are in the running state and are consuming bandwidth. Under these
conditions, the primary bundle is carrying the data between the CEs.
If the primary bundle goes down or is no longer in the running
state, the CTP devices switch over to the backup bundle, and the backup
bundle carries the data. The time that it takes for the switchover
to occur depends on the bundle configuration. The switchover time
for a typical 1 MHz circuit is less than one second.
When the primary bundle returns to the running state, the CTP
devices switch back to the primary bundle, and the primary bundle
begins carrying data.
Requirements for Y-Cable Redundancy
Keep the following in mind when you use Y-cable redundancy:
- Y-cable redundancy is supported only on serial interfaces.
The serial interface cannot have a T1/E1 daughter card installed.
- This feature requires a special Y cable. The Y cable provides
control leads between the two CTP devices in addition to the standard
signal, clock, and data leads connected to the attached device. There
is one Y cable for CTP2000 devices and another Y cable for CTP150
devices. Therefore, you must use the same platform type at each site.
- The Y cable is short to maintain signal quality. The two
CTP devices connected to the Y cable must be in close proximity to
each other.
- To run diagnostics on a nonactive bundle attached to a
Y cable without introducing data errors on the active bundle, Y-cable
redundancy must be configured, and you cannot have a daughter card
installed.
Clocking Supported with Y-Cable Redundancy
Y-cable redundancy is supported with the following clock configurations:
- Configured rate without external TX clock (TT).
- Configured rate with external TX clock (TT).
- All clocked with external TX clock (TT).
- Adaptive clocking with internal clock.
- Adaptive clocking with external TX clock (TT).
Published: 2010-10-26