SDU setting being ignored?

Yes, I'm traveling down the dark path of Oracle traffic over a WAN. Naturally, I want to test changing the SDU to optimize it. Client is 32-bit WinXP, server is AIX 5.3TL8 and both are using v10.1.0.5.0 Oracle.

To test, I added these entries to $OH/network/admin/listener.ora on the server:

MYDBWAN =
  (DESCRIPTION_LIST=(DESCRIPTION=(ADDRESS_LIST =     (ADDRESS=(PROTOCOL=TCP)(HOST=myhost)(PORT=1526)(QUEUESIZE=32)))))

SID_LIST_MYDBWAN =
  (SID_LIST = (SID_DESC = (SDU = 8192)(SID_NAME = mydb)))

I then started the MYDBWAN listener, so as not to affect connections to the default listener:

lsnrctl start mydbwan

On the client's %OH%\network\admin\tnsnames.ora, I added:

MYDBWAN=
  (DESCRIPTION=(ADDRESS=(PROTOCOL=TCP)(HOST=myhost)(PORT=1526)(SDU=8192))     (CONNECT_DATA=(SERVICE_NAME=mydb)))

I enabled a net trace in the client's sqlnet.ora. When connecting to MYDBWAN from SQL*Plus, the trace has:

[28-JAN-2009 13:01:15:966] nsc2addr:

(DESCRIPTION=(ADDRESS=(PROTOCOL=TCP)(HOST=1.2.3.4)(PORT=1526)(SDU=8192))(CONNECT_DATA=(SID=mydb)(CID=(PROGRAM=C:\Oracle\product\10.1.0\Client_1\bin\sqlplus.exe)(HOST=mylaptop)(USER=rich))))
[28-JAN-2009 13:01:15:966] nttbnd2addr: entry
[28-JAN-2009 13:01:15:966] nttgetport: entry
[28-JAN-2009 13:01:15:966] nttgetport: port resolved to 1526
...
[28-JAN-2009 13:01:15:976] nsopen: lcl[0]=0xf4ffefff, lcl[1]=0x102000,
gbl[0]=0xfabf, gbl[1]=0x0, tdu=32767, sdu=2048

Still only 2048! I've tried changing "SERVICE_NAME" to "SID" in the tnsnames.ora, selecting different values for SDU on both client and server, and bouncing the listener in between each change. But I can't confirm that SQL*Net's using a non-default SDU value.

I've searched the Oracle Net Admin Guide, Metalink, and the List archives, but no luck. I think the last time I messed with this was in the Fatcity days...

Thoughts anyone?

TIA!
Rich

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