these figures have in common the application of a compression algorithm only to that portion of a packet occurring after the header which in both figures is presumed since the format of input packets will be known to end at the 38 th byte the techniques implemented by the switches differ in the criterion employed for storing an uncompressed packet in preference to a packet to which a compression algorithm has been applied it is possible to apply a compression algorithm to the non header portions of all packets and to store such packets indiscriminately however as will be indicated later typical compression algorithms may especially for small packets but generally in dependence on the information content of a packet actually increase the size of the packet such an increase will occur at least with appropriate selection of compression algorithms in a minority and normally a small minority of packets but even so the basic compression and decompression method described herein is preferably modified so that the possibility of the storage of a packet which has been subjected to a compression algorithm but has actually increased in size is either significantly reduced or eliminated in fig2 and 3 thicker lines denote the paths for packet data and may be constituted by groups of parallel data lines whereas the narrower.