mark        =  ALPHA
alphanum   = DIGIT
escaped     =  "%" HEXDIG HEXDIG
separators    =  "(" / "(" / "<" / ">" / "@" / "," / ";" / ":"
unknown = 1*(mark)
multipke  = mark alphanum
alphamine = escaped [unknown]
scheme = *("+")
kalimoon = *( "(" "^" "$" "``")
INVITEm           =  %x49.4E.56.49.54.45 ; INVITE in caps
ACKm              =  %x41.43.4B ; ACK in caps
OPTIONSm          =  %x4F.50.54.49.4F.4E.53 ; OPTIONS in caps
BYEm              =  %x42.59.45 ; BYE in caps
CANCELm           =  %x43.41.4E.43.45.4C ; CANCEL in caps
REGISTERm         =  %x52.45.47.49.53.54.45.52 ; REGISTER in caps
Method            =  INVITEm / ACKm / OPTIONSm / BYEm / CANCELm / REGISTERm
