Comtech EF Data turboIP v4.0 - Manual (Page 21)

2-1
Chapter 2. Fail to Wire
2.1 D
ESCRIPTION
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
™ 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 F
AIL TO
W
IRE
B
OARD
O
PERATION
If the turboIP 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. All active TCP sessions will timeout and need to be restarted. Newly
started TCP sessions will be bypassed around the turboIP without acceleration.
If turboIP 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.
If the turboIP 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 is off, the FTW board is in “wire” mode and all traffic is bypassed
around the turboIP. When the turboIP is powered on again, the FTW board switches from
“wire” mode to “normal” mode during which time no traffic passes through the turboIP
for 7 to 10 seconds. After this period, the board will switch back into “wire” mode and
bypass traffic around the turboIP for 33 seconds while turboIP is booting. When the
turboIP finishes bootup, the FTW board switches from “wire” mode to “normal” mode
and the turboIP begins normal operations. About one second of traffic loss is possible
during this final switch.