00297nam a2200121 a 450000500170000002000150001708200150003210000230004724500370007025000120010726000350011930000210015420251203110731.0  a8129702061  a004.6bSTA  aStallings, William  aData and Computer communications  a7th ed.  aDelhibPearson Educationc2004  a855p.c24 cm. PB