Communication protocol stack apparatus and method of implementing same

A method of implementing a communication protocol stack of at least a higher protocol layer and a lower protocol layer, comprising the steps of:

• (i) determining for each protocol layer of said stack the maximum aggregate header and aggregate trailer length for the layer and each lower layer;
• (ii) allocating, for each protocol layer of the stack, at least one memory buffer having a length at least equal to the sum of the determined maximum aggregate header and maximum aggregate trailer lengths for the layer and a selected maximum data payload length;
• (iii) receiving at a first layer data to be transmitted from said stack;
• (iv) selecting an available buffer from said at least one memory buffer allocated for said first layer;
• (v) copying information representing a portion of said received data, not exceeding said selected maximum data payload length, to said buffer starting at a position offset from the start of said buffer by a length equal to said determined maximum header length for said protocol layer;
• (vi) copying information representing an encapsulating header for said protocol layer to the positions in said buffer immediately preceding said information previously copied into said buffer and copying information representing an encapsulating trailer for said layer to the positions in said buffer immediately following said information previously copied into said buffer;
• (vii) setting a first indicator to indicate the first position in said buffer of said information representing said encapsulating header of said protocol layer and setting a second indicator to indicate the last position in said buffer of said information representing said encapsulating trailer for said protocol layer;
• (viii) passing said buffer to the next lower protocol layer in said stack;
• (ix) repeating steps (vi) through (viii) until information from the lowest layer has been copied into said buffer and said first and second indicators set accordingly;
• and
• (x) copying the information in said buffer, between the position indicated by said first indicator and the position indicated by said second indicator, to a data transmission device.

A protocol stack apparatus including at least two protocol layers arranged to form the stack, the stack apparatus comprising:

• means for determining the aggregated maximum encapsulating header and trailer lengths for each layer of the stack;
• means for pre-allocating for each said protocol layer of said stack, at least one buffer of a length equal to the sum of the determined aggregate maximum header length and the determined aggregate trailer length and a pre-selected maximum data length;
• means for receiving at a protocol layer data from an application to copy said data into one of said pre-allocated buffers for said layer at a position offset by the determined maximum aggregate header length and to copy an encapsulating header for said layer to a position immediately before the location of the data in said buffer and to copy an encapsulating trailer for said layer to a position immediately after said data in said buffer;
• means for setting an indicator of the position of the start of said encapsulating header in said buffer and for setting an indicator of the position of the end of said encapsulating trailer in said buffer;
• means for passing said buffers in turn, to each next lower layer of said protocol stack;
• means for copying the encapsulating header of said lower layer into said buffer before the position indicated by said indicator of the position of the start of the encapsulating header and for updating said indicator to indicate the start position of the encapsulating header of said lower layer;
• means for copying the encapsulating trailer of said lower layer into said buffer after the position indicated by the indicator of the position of end of the encapsulating trailer and for updating said indicator to indicate the end position of the encapsulating trailer of said lower level;
• means for copying the buffer contents between said indicator of the start position of said encapsulating header and the indicator of the end position of said encapsulating trailer to a transmission device at the lowest layer of said stack.

A method of constructing and using a protocol stack comprising at least two protocol layers, comprising:

• (i) for each layer of said stack determining a maximum length comprising the sum of a preselected maximum data payload length and a maximum aggregate header length and a maximum aggregate trailer length, said aggregates including each layer in said protocol stack below said layer;
• (ii) for each layer allocating at least one buffer of said maximum length;
• (iii) receiving data to be transmitted at a layer and copying said data into said at least one buffer at a position offset from the start of the buffer by said maximum aggregate header length determined for said layer, copying into said buffer immediately before said copied data a header for said layer, copying into said buffer immediately after said copied data a trailer for said layer and setting indicators of the positions within said buffer of the start of said header and the end of said trailer;
• (iv) passing said buffer to a lower layer of said stack, said lower layer copying into said buffer immediately preceding the start of the header in said buffer as indicated by said indicator a header for said layer and copying into said buffer immediately after the end of the trailer in said buffer as indicated by said indicator a trailer for said layer and updating said indicators of the positions of the start of the headers and the end of the trailers accordingly;
• (v) at the lowest level of said stack, copying to a data transmission device said data between said indicators.

An apparatus for managing a buffer for a protocol stack having at least two protocol layers, said apparatus comprising:

• means for allocating for each layer a buffer of a maximum length, said maximum length including the sum of a selected maximum data payload length and a maximum aggregate header length and a maximum aggregate trailer length, said aggregates including each layer in said protocol stack below said layer;
• means for copying receiving data to be transmitted at a layer into said buffer at a position offset from the start of the buffer by said maximum aggregate header length determined for said layer;
• means for copying a header and a trailer for said layer into said buffer at positions determined by header and trailer indicators, respectively;
• means for updating said header and trailer indicators so as to indicate the positions of the start of said header and the end of said trailer in said buffer;
• means for passing said buffer to a lower layer to cause said updating means and said means for copying a header and a trailer to operate for said lower layer;
• and
• means for copying data between said references to a data transmission device after the header and trailer for the lowest layer are copied into the buffer.