ll, the serving MSC may discover that the best handoff is a handoff back to an MSC that is already involved in the call (either the anchor MSC or a tandem MSC). In this case, a handoff back is required. A handoff back is like any other inter-MSC handoff in that it is a change of serving MSC, but it has the advantage that the hand- off back should shorten rather than lengthen the handoff chain. A handoff back pre- vents tromboning. Here is a typical handoff-back scenario: The serving MSC requests a handoff back. The target MSC accepts the handoff back. The serving MSC tells the user terminal to change channel. The user terminal changes channel. The target MSC detects the user terminal on its channel. The target MSC requests release of the extra link. The serving MSC accepts the release. The link is released. The handoff is complete. 15.1.4 Path minimization Path minimization is more complex than handoff back. If the serving MSC or the an- chor MSC performs path minimization, then the handoff link will go as directly as pos- sible from the anchor MSC to the target MSC. A third alternative is to have a tandem MSC perform the path-minimization process, which creates a path from that tandem MSC as directly as possible to the target MSC. Here is a typical path minimization scenario: The serving MSC sends a path-minimization message to the anchor MSC. The anchor MSC sets up a direct path to the target MSC. The anchor MSC sends a handoff message to the target MSC. The serving MSC tells the user terminal to change channel. The user terminal changes channel. The target MSC detects the user terminal on its channel. The target MSC notifies the anchor MSC. The anchor MSC connects the call to the target MSC. The old circuits are released. The handoff is complete. Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies. All rights reserved. Any use is subject to the Terms of Use as given at the website. ANSI-41 Key Telephony Concepts Path minimizat