Browse Prior Art Database

AUTOMATIC PROTECTION OF DROP & INSERT T1 LINES

IP.com Disclosure Number: IPCOM000006975D
Original Publication Date: 1993-Jun-01
Included in the Prior Art Database: 2002-Feb-13
Document File: 3 page(s) / 106K

Publishing Venue

Motorola

Related People

Tim Groch: AUTHOR [+3]

Abstract

Drop & insert Tl distribution is a cost effective method of implementing a digital communications net- work between multiple sites where the tratlic is too low to warrant a network of dedicated Tl's between each site. In a drop & insert system, a single Tl is used to interconnect multiple sites, but only a handful of chan- nels are dropped at a particular site. The remaining chan- nels are passed through to subsequent sites. Outbound information is inserted into the time slots which were dropped. Figure 1 shows a fully interconnected topol- ogy usmg dedicated communication links between each site versus the topology of a system using a Drop/Insert scheme.

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MOTOROLA /NC. Technical Developments Volume 19 June 1993

AUTOMATIC PROTECTION OF DROP & INSERT Tl LINES

by Tim Groch, Mark Em and Tim Wilson

  Drop & insert Tl distribution is a cost effective method of implementing a digital communications net- work between multiple sites where the tratlic is too low to warrant a network of dedicated Tl's between each site. In a drop & insert system, a single Tl is used to interconnect multiple sites, but only a handful of chan- nels are dropped at a particular site. The remaining chan- nels are passed through to subsequent sites. Outbound information is inserted into the time slots which were dropped. Figure 1 shows a fully interconnected topol- ogy usmg dedicated communication links between each site versus the topology of a system using a Drop/Insert scheme.

  An inherent reliability problem arises in a drop & insert system because of the shared Tl link. A failure of the Tl span anywhere in the network will cause a com- munications failure of the entire system. Automatic Pro- tection Switches (APS's) have long been used to protect point-to-pdint Tl spans by allowing the traffic to switch to a redundant Tl upon failure of the main Tl span. The following describes a method of using those same APS's to protect a drop & insert type ofT1 network.

  Figure 2 shows a block diagram of a typical APS. Tl traffic, under normal conditions, is routed between the "Main" side of the switch and the local equipment. When a failure is detected on the "Main" side, traffic is routed through the "Standby" &de of the switch. When

service is restored to the "Main" Tl, traffic is reverted to this side, typically after some small time delay.

  Figure 3 shows a typical drop & insert system. Traf- tic flows in a loop through the system, with data in spe- cific time slots being removed at particular sites and th...