Can Bind variables be an issue with respect to network transfer?

I investigate a software that gets single rows in a loop. In this case it is 2400 iterations each retrieving one or no row. Access is quick, via primary key index but the execution time is suspiciously high. My investigation shows in the runtime stats that the  statement is executed on the DB in a fraction of the time. The total run time for the statement is 8 minutes, the total database execution time for 2400 executions is about 10 seconds. Did iterative stack on the oracle process and it show that the time was spend on network transfer.
But the question still remains why network transfer is done in the execution phase of a statement.
I guess the reason could be bind variables since there are over 4700 bind variables and the binding is done in the execution phase. I wonder if that idea is reasonable. Even if there are many bind variables I wonder if it can make up to that amount of time. The bind variables are all rather short. 75% of the time I see this stack:
  ffffffff47de1d80 read     (18, ffffffff7d63d74e, 8010)   0000000117585650 nsprecv (ffffffff7d63bf08, ffffffff7fff5daf, ffffffff7d62b4c8, 0, 0, ffffffff7d63d680) + 1b0   00000001175993d0 nsrdr (ffffffff7db606b8, ffffffff7d62b4c8, ffffffff7d63bf08, 0, 0, ffffffff7da5d580) + 90   00000001174f659c nsfull_pkt_rcv (ffffffff7d62b2d8, 55, 1000, ffffffff7d62b550, ffffffff7fff9ecb, ffffffff7d62b4c8) + 1fdc   00000001174fc40c nsfull_brc (ffffffff7d62b2d8, 10000000, ffffffff7fff9ecb, 3, 2fc, f0e0c00) + 6c
  000000011763cb3c nioqrc (ffffffff7daad150, 11869cb48, ffffffff7fffce0d, 1, 0, ffffffff7d62b170) + 17c   0000000109de001c opikndf2 (ffffffff7daad150, 2, ffffffff7da92e0c, 1, 1a2, 1) + 45c
  0000000109dce4a8 opitsk (202db9, ffffffff7da92e08, ffffffff7da92e0c, ffffffff7da89768, 0, ffffffff7da8faf0) + 3a8   0000000109de2d24 opiino (1, ffffffff7fffe080, 10000, ffffffff7daad048, 10a, ffffffffffff3354) + 384
  0000000109e0456c opiodr (22000, ffffffff7daad050, 1328, 1358, 3c, 0) + 44c   0000000109dc2ae4 opidrv (1694, 0, ffffffff7daad048, ffffffff7da92e38, 1328, 1fc00) + 384
  000000010d0ea16c sou2o (ffffffff7fffe058, 3c, 4, ffffffff7fffe080, 102ebf000, 70) + 6c
  0000000104a667cc opimai_real (2, ffffffff7fffe458, 1, ffffffff7fffe080, 103392000, 103392) + 12c   000000010d110bc4 ssthrdmain (0, 1186a8, 1186a8000, 0, 118400, ffffffff7fffe280) + 1c4
  0000000104a660f8 main (2, ffffffff7fffe568, 0, ffffffff7fffe468, ffffffff7fffe578, 0) + 138
It seems to be obvious that this code part is receiving a message. 25% I also see this
ffffffff47de2638 __write (ffffffff7d63c6d0, 10, ffffffff7d63c168, 0, 1, 0) + c
  0000000117579de0 nsntwrn (ffffffff7d645ef8, ffffffff7d63c6d0, ffffffff7d5d82e6, ffffffff7d63c168, 200000, 0) + 40   000000011758c4e0 nspsend (ffffffff7d63bf08, ffffffff7d63c168, ffffffff7d62b420, 0, 0, 0) + 2a0
  00000001175385a8 nsdofls (30a, ffffffff7d62b420, ffffffff7d63bf08, 100400c, 0, 0) + 208
  0000000117534380 nsdo (ffffffff7d62b2d8, 54, ffffffff7d62b420, ffffffff7d62b420, 0, 0) + 7480
  00000001174fc464 nsfull_bsd (ffffffff7d62b2d8, ffffffff7d62b420, 1, 20, 300, 1) + 24
  000000011763cab0 nioqrc (ffffffff7daad150, 11869cb48, ffffffff7fffce0d, 1, 8, ffffffff7d62b170) + f0   0000000109de001c opikndf2 (ffffffff7daad150, 2, ffffffff7da92e0c, 1, 1a2, 1) + 45c
  0000000109dce4a8 opitsk (202db9, ffffffff7da92e08, ffffffff7da92e0c, ffffffff7da89768, 0, ffffffff7da8faf0) + 3a8   0000000109de2d24 opiino (1, ffffffff7fffe080, 10000, ffffffff7daad048, 10a, ffffffffffff3354) + 384
  0000000109e0456c opiodr (22000, ffffffff7daad050, 1328, 1358, 3c, 0) + 44c   0000000109dc2ae4 opidrv (1694, 0, ffffffff7daad048, ffffffff7da92e38, 1328, 1fc00) + 384
  000000010d0ea16c sou2o (ffffffff7fffe058, 3c, 4, ffffffff7fffe080, 102ebf000, 70) + 6c
  0000000104a667cc opimai_real (2, ffffffff7fffe458, 1, ffffffff7fffe080, 103392000, 103392) + 12c   000000010d110bc4 ssthrdmain (0, 1186a8, 1186a8000, 0, 118400, ffffffff7fffe280) + 1c4
  0000000104a660f8 main (2, ffffffff7fffe568, 0, ffffffff7fffe468, ffffffff7fffe578, 0) + 138
  0000000104a65f6c _start (0, 0, 0, 0, 0, 0) + 12c

That seems to be sending a message. What kind of Message could that be? An acknowledge?

Regards

Lothar

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