Ericsson, Sweden The RObust Header Compression WG (ROHC) is developing compression schemes initially for IP/UDP/RTP header compression [ROHC]. The group is also chartered to develop compression for IP/TCP and after re- chartering it is possible (probable) that also compression of other protocols will follow. Compression and decompression must always follow well defined rules but there exist a number of variables that will affect details in the way compression should be carried out and how these rules are set. The purpose of this document is to identify such variables and outline a way to make ROHC both adaptable to various conditions and possible to extend for future needs.