`Notes on the Networks
`
`
`
`Telcordia Technologies Special Report
`SR-2275
`Issue 4
`October 2000
`
`An SAIC Company
`
`AT&T, Exh. 1012, p. 1
`
`
`
`Telcordia Notes on the Networks
`Copyright Page
`
`SR-2275
`Issue 4
`October 2000
`
`Telcordia Notes on the Networks
`
`SR-2275 replaces SR-2275, Bellcore Notes on the Networks, Issue 3, December 1997.
`
`Related documents:
`
`SR-NOTES-SERIES-01, Telcordia Notes on the Synchronous Optical Network
`(SONET)
`SR-NOTES-SERIES-02, Telcordia Notes on Dense Wavelength-Division
`Multiplexing (DWDM) and Optical Networking
`SR-NOTES-SERIES-03, Telcordia Notes on Number Portability and
`Number Pooling
`SR-NOTES-SERIES-04, Telcordia Notes on the Evolution of Enhanced
`Emergency Services.
`
`To obtain copies of this document, contact your company’s document coordinator
`or your Telcordia account manager, or call +1 800.521.2673 (from the USA and
`Canada) or +1 732.699.5800 (all others), or visit our Web site at www.telcordia.com.
`Telcordia employees should call +1 732.699.5802.
`
`Copyright © 2000 Telcordia Technologies, Inc. All rights reserved. This document
`may not be reproduced without the express written permission of Telcordia
`Technologies, and any reproduction without written authorization is an
`infringement of copyright.
`
`Trademark Acknowledgments
`Telcordia is a trademark of Telcordia Technologies, Inc.
`CLCI, CLEI, CLFI, CLLI, ISCP, NMA, and SEAS are trademarks of Telcordia Technologies, Inc.
`COMMON LANGUAGE, SPACE, TELEGATE, AIRBOSS, and TIRKS are registered trademarks of
`Telcordia Technologies, Inc.
`CLASS is a service mark of Telcordia Technologies, Inc.
`Appletalk is a registered trademark of Apple Computer, Inc.
`DECNet is a trademark of Digital Equipment Corporation.
`1/1AESS, 4ESS, 5ESS, Dataphone, and SLC are registered trademarks of Lucent Technologies, Inc.
`DMS-10, DMS-100F, DATAPATH, and TOPS are trademarks of Nortel.
`DMS-100 is a registered trademark of Nortel.
`NEAX-61E is a trademark of NEC America, Inc.
`EWSD is a registered trademark of Siemens AG.
`
`Any other companies and products not specifically mentioned herein are trademarks or service marks
`of their respective trademark and service mark owners.
`
`ii
`
`AT&T, Exh. 1012, p. 2
`
`
`
`SR-2275
`Issue 4
`October 2000
`
`Telcordia Notes on the Networks
`Surveillance and Control
`
`Figure 10-2. Network Congestion
`
`At the onset of the overload, also known as circuit shortage, the dominant cause
`for customer blockage is the failure to find an idle circuit. Circuit blocking alone
`limits the number of extra calls that can be completed but does not cause a
`significant loss in the call-carrying capacity of the network below its maximum.
`As the overload persists and the network enters a congested state, regenerated-
`calling pressure changes customer blockage from circuit shortage to switching
`delays.
`
`Switching delays cause timeout conditions during call setup and occur when
`switching systems become severely overloaded. Timeouts are designed into
`switching systems to release common-control components after excessively
`long delay periods and provide the customer with a signal indicating call-
`attempt failure. Switching-congestion timeouts with short holding-time
`attempts on circuit groups replace normal holding-time calls. Switching delays
`spread quickly throughout the network.
`(cid:127) A trunk-group overload usually occurs during general or focused overloads
`and/or atypical busy hours. Some of the overload causes not discussed above
`are facility outages, inadequate trunk provisioning, and routing errors. The
`results of a trunk-group overload can be essentially the same as those
`previously discussed for general overloads. However, the adverse effects are
`usually confined to the particular trunk group or the apex area formed by the
`trunk group and those groups’ alternate-routing to the overloaded trunk group.
`
`10–7
`
`AT&T, Exh. 1012, p. 3
`
`
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