RFC 3321 SigComp - Extended Operations January 2003 2. Terminology The reader should consult [SIGCOMP] for definitions of terminology, since this document uses the same terminology. Further terminology is defined below. Compressor Entity that encodes application messages using a certain compression algorithm and keeps track of state that can be used for compression. The compressor is responsible for ensuring that the messages it generates can be decompressed by the remote UDVM. Decompressor The decompressor is responsible for converting a SigComp message into uncompressed data. Decompression functionality is provided by the UDVM. Dynamic compression Compression relative to messages sent prior to the current compressed message. Explicit acknowledgement Acknowledgement for a state. The acknowledgment is explicitly sent from a decompressor to its remote compressor. The acknowledgement should be piggybacked onto a SigComp message in order not to create additional security risks. Shared compression Compression relative to messages received by the local endpoint prior to the current compressed message. Shared state A state used for shared compression consists only of an uncompressed message. This makes the state independent of the compression algorithm. Hannu, et. al. Informational