[PERFORMANCE] reduced overhead of transfer description

The transfer description overhead is now constant and is currently 15
bytes in size. Down from approx. 120 bytes.

Change-Id: I7a32b12addc359ee4506830cd2a472fd6cb529ce
Reviewed-on: http://saros-build.imp.fu-berlin.de/gerrit/1604
Tested-by: Jenkins CI
Reviewed-by: Stefan Rossbach <srossbach@arcor.de>