Browse Prior Art Database

Method for Extending the Utopia Level 2 Interface to Handle ATM Cells With and Without Pre-Pended Header up to 64 Bytes.

IP.com Disclosure Number: IPCOM000011372D
Original Publication Date: 2003-Feb-14
Included in the Prior Art Database: 2003-Feb-14
Document File: 2 page(s) / 49K

Publishing Venue

IBM

Abstract

Many systems use pre-pended headers to help route frames and cells through the system. Disclosed is a method used to place the Asynchronous Transfer Mode (ATM) Cells in a fixed buffer location regardless of the length of the pre-pended header. This fixed location makes it easy for the system software to locate the Cell.

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  Method for Extending the Utopia Level 2 Interface to Handle ATM Cells With and Without Pre-Pended Header up to 64 Bytes.

   Disclosed is a method of extending a Utopia Level 2 Interface to include pre-pended header bytes. This method is used to store, into a temporary buffer, Asynchronous Transfer Mode (ATM) cells with pre-pended headers, while minimizing the control logic required to move the ATM cells from the temporary buffer to the system. The pre-pended header bytes can be used to pass physical layer specific or connection specific data across a private network. One advantage of this method is that the ATM Cell header and payload is always located starting at a fixed offset in the temporary buffer. A second advantage of the method is the ATM Cell Header can be transferred to the system in one clock cycle (note: it is assumed that data is moved from the temporary buffer to the system layer in 8 byte slices). Without this method, different length pre-pended headers would require the ATM Cells to start at different temporary buffer offsets making it very difficult for the system software to locate the ATM Cell within the Temporary buffer. ATM Cell location becomes even more important in multidrop environments.

     The figure below shows storing the ATM cell in the temporary buffer using the disclosed method. In the preferred embodiment, a maximum of 64 bytes is implemented as this is a typical transfer size for a POS-Phy Interface. Therefore, an additional 9 pre-pende...