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Tom dot Evans at
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TCPG Telecom Patterns

Software Design Patterns

The Twin Cities Patterns Group meets monthly in association with the Object Technology User Group of St. Paul and Minneapolis Minnesota.

This year TCPG is working through the J2EE patterns book, and each meeting also has the goal of one pattern 'not from the J2EE book'.

For the May '02 meeting, Tom Evans presented:

Fault-Tolerant Telecommunication System Pattern
by Michael Adams, James Coplien, Robert Gamoke, Robert Hanmer, Fred Keeve, Keith Nicodemus, AT&T Bell Laboratories.

This work published in the PloP/95 or PloP 2 Patterns book is also available from James Coplien here:
www.bell-labs.com/user/cope/Patterns/PLoP95_telecom.html.

As a motivator for the patterns, the Long Distance melt-down of 1980 was discussed based on this reference:

AT&T Failure of January 15, 1990

On January 15, 1990, 114 switching nodes of the AT&T long distance system went down. The published cause of the crash was a bug in the failure recovery code of the switches. When a node crashed, it sent "out of service" message to the neighboring nodes, which are supposed to re-route traffic around it. However, the bug (a misplaced "break" statement in C code) caused the neighboring nodes to crash themselves upon receiving the "out of service" message, and further propagate the fault by sending an "out of service" message to nodes further out in the network.
...

Tom's handout included the above two articles, a rendition of the pattern map found in the PLoP 95 reference, and a summary. As the full hand out was primarily a reprint of the material accessable from the authors above, it is no longer available.

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