PNNI Signaling Protocol
89
connection is established and the data is sent. These connections are
permanent because they are established administratively, rather than on a
demand basis. If the signal is to be established by demand, it is known as
a soft PVC or soft PVCC.
Alternate Routing
and Crankback
Occasionally, after the decision has been made by the switch to open a
channel in a certain direction, the link may fail or the attributes may
change. When the switch detects this change, it does not close the
connection and send a disconnect message. Instead it hops backwards,
or cranksback
.
In
crankback
, hops are decreased. The switch will
crankback to a point where an alternate route exists and will open the
rest of the channel in that direction. If, the network is a flat network,
crankback will be done to the source. Figure 28 shows the same signal
with a bad connection between two switches.
Figure 28
Sending a Signal with a Failed Link
A.1.1
A.1.2
A.1.3
A.1.4
A.1.5
A.1.6
A.1.7
A.1.8
A.1.9
A.2.0
A.2.1
A .2 .2
A.2.3
A.2.4
A.2.5
A.2.6
A.2.7
Source
Destination
Place Where Link Failed
Chosen Path to Take
Physical Link
Summary of Contents for CoreBuilder 7000
Page 12: ......
Page 30: ...30 CHAPTER 1 ATM NETWORK BASICS...
Page 32: ...32 CHAPTER 1 ATM NETWORK BASICS...
Page 34: ...34 CHAPTER 1 ATM NETWORK BASICS Figure 8 LANE Network over WAN...
Page 96: ...96 CHAPTER 4 PRIVATE NETWORK TO NETWORK INTERFACE PNNI VERSION 1 0...
Page 184: ...184 CHAPTER 7 LAN EMULATION VERSIONS 1 0 AND 2 0...
Page 206: ...206 CHAPTER 9 DEVICE MANAGEMENT...
Page 222: ...222 APPENDIX A TECHNICAL SUPPORT...
Page 234: ...234 APPENDIX B PROTOCOLS AND INTERFACES...
Page 238: ...238 APPENDIX C COREBUILDER 7000 FAMILY ATM SWITCH SPECIFICATIONS...
Page 242: ...242 APPENDIX D SAFETY INFORMATION...