Comtech EF Data turboIP-45 - Manual (Page 19)

2–1
Chapter 2. Fail to Wire
2.1 Description
The Fail to Wire (FTW) function provides a low-cost solution for high network availability. If the unit
fails, then the installed FTW board allows traffic to bypass the turboIP-45
™ as if it were simply a wire.
This means that a unit failure will not bring down the whole network. Traffic will continue to pass and,
at most, the existing TCP sessions will be terminated and have to be restarted. The FTW functionality
provides network reliability without the added cost of one-for-one redundancy.
2.2 Fail to Wire Board Operation
If the turboIP-45 fails (excluding loss of power), then the FTW board switches into “wire” mode
approximately 7 to 10 seconds after the failure. At this time, all traffic is bypassed around the turboIP-
45. All active TCP sessions will timeout and need to be restarted. Newly started TCP sessions will be
bypassed around the turboIP-45 without acceleration.
If turboIP-45 reboots, then the FTW board switches to wire mode seven to 10 seconds after the reboot is
initiated, and stays in “wire” mode until the reboot is completed. Hence, 7 to 10 seconds is the extent of
network outage caused by a reboot of the turboIP-45.
If the turboIP-45 loses power, then the FTW board immediately switches into “wire” mode.
Approximately one second of traffic is lost during this switch. In addition, all TCP sessions will timeout
and have to be restarted.
While the turboIP-45 is off, the FTW board is in “wire” mode and all traffic is bypassed around the
turboIP-45. When the turboIP-45 is powered on again, the FTW board switches from “wire” mode to
“normal” mode during which time no traffic passes through the turboIP-45 for 7 to 10 seconds. After
this period, the board will switch back into “wire” mode and bypass traffic around the turboIP-45 for 33
seconds while turboIP-45 is booting. When the turboIP-45 finishes bootup, the FTW board switches
from “wire” mode to “normal” mode and the turboIP-45 begins normal operations. About one second of
traffic loss is possible during this final switch.