Comtech EF Data turboIP-G2 - Manual (Page 161)

8–1
Chapter 8. FAIL TO WIRE
8.1 Introduction
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-G2 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.
8.2 Fail to Wire Board Operation
If the turboIP-G2 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-G2. All active TCP sessions will timeout and need to be restarted. Newly started TCP
sessions will be bypassed around the turboIP-G2 without acceleration.
If the turboIP-G2 reboots, then the FTW board switches to Wire Mode 7 to 10 seconds after the
reboot is initiated, and stays in this mode until the reboot is completed. Hence, 7 to 10 seconds is
the extent of network outage caused by a reboot of the turboIP-G2.
If the turboIP-G2 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-G2 is off, the FTW board is in Wire Mode and all traffic is bypassed around
the turboIP-G2. When the turboIP-G2 is powered on again, the FTW board switches from Wire
Mode to Normal Mode, during which time no traffic passes through the turboIP-G2 for 7 to 10
seconds. After this period, the board will switch back into Wire Mode and bypass traffic around
the turboIP-G2 for 33 seconds while the turboIP-G2 is booting. When the turboIP-G2 finishes
bootup, the FTW board switches from Wire Mode to Normal Mode, and the turboIP-G2 begins
normal operations. About one second of traffic loss is possible during this final switch.