Intermediate Systems QSs) are off-the-shelf elements that route Internet
Protocol (IP) and IS0 Connectionless Network Protocol (CLNP) datagrams
between MD-ISS, and between MD-ISS and Fixed End Systems (F-ESs)
(Figure 1010-1). ISS also may be used to route mobile data link frames that
are encapsulated in CLNP datagrams between Mobile Data Base Stations
(MDBSs) and MD-ISS.