Atm adaptation layer validating the atm header

Under ordinary operating conditions, lookup requests to the database are likely to be much more numerous than database editing operations.

However, database editing operations are generally more complex than database lookup operations.

Efficient execution of these management tasks can be facilitated by maintaining the database in a sorted order using a modified bubblesort algorithm.

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Moreover, the demand for ordinary voice telephone service is becoming a decreasingly smaller part of the overall traffic demand in comparison to other telecommunications services such as data communications between computers, graphical image transmissions, video-conferencing and similar broadband services.Eight or twelve bits of the header segment contain the Virtual Path Identifier (VPI), and sixteen bits of the header segment contain the Virtual Channel Identifier (VCI).Each ATM exchange translates the abstract routing information represented by the VPI and VCI bits into the addresses of physical or logical network links and routes each ATM cell appropriately.Computational efficiency considerations mandate that the database be organized in such a manner that database lookup requests are handled expeditiously without letting any pending database editing operations get too backlogged.An ATM link operating at 155.52 megabits per second (the STM-1 rate) handles over 365,000 ATM cells every second.This operation is referred to hereinafter as a database lookup operation.During the operation of an ATM exchange, the connection information database needs to be concurrently available for both editing as well as for lookup.If the cell-bandwidth-averaged duration of each connection were one minute, then the connection database will have about one million entries that would have to be replaced or revised once every minute.Since frequent database edit operations are thus likely, there is a great need for efficient techniques to manage an ATM connection database.Since an ATM exchange is likely to have multiple incoming and outgoing links operating at the STM-1 rate, it is possible for the connection database to get over one million lookup requests a second.Since database lookup requests are so frequent, it is important for the database to be continually sorted, especially if a binary search algorithm is to be used for handling lookup requests.

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