ibps-so 2016 · Question 19 of 394

The mainframe on which Chandrabhaga Urban Bank keeps its customer master stores every character of a name in EBCDIC, while the workstations standing in its branches, and the tablet computers issued to its eld o cers, all hold the same names in ASCII. A message raised at a branch must therefore be converted from one coded character set to the other before the receiving process can make sense of it, and the same message must in addition be compressed to save line charges and enciphered to satisfy the bank's security policy. The network cell has told the trainees that all three of these operations — recoding, compression and encipherment — are concerned not with delivering the message but with the syntax and the form in which it is represented, and that the reference model of Figure 1 gathers them at one layer and one layer only. The layer of the OSI model at which such translation between di ering data representations is performed is:

1. AThe application layer, layer 7, since it is the layer nearest the user process that raised the message
2. BThe session layer, layer 5, since the conversion must be agreed before the dialogue between the two processes opens
3. CThe presentation layer, layer 6, which is charged with translation, compression and encryption — that is, with the syntax and semantics of the information exchangedCorrect
4. DThe transport layer, layer 4, since the conversion applies to the whole end-to-end message and not to a single link
5. EThe data link layer, layer 2, since the change of representation must be made before the bits are framed for the medium