00280    a2200097   4500020001500000082001600015245005500031260004000086300001600126650004000142  a0749260521  a004.65bOPE  aBlock 10 networksbT322 digital telecommunications  aColombobOpen Unversityc1990g1990  a42p.c29cm.  aCOMMUNICATIONS NETWORK ARCHITECTURE