ANS1017E (RC-50) Session rejected: TCP/IP connection failure

We are switching from TokenRing to Ethernet (100MB,full duplex) to do our
TSM Backups.

I did test with two 'TDP for Lorus Domino' clients but  about 1/3 of the
Domino DB's backup are failing
with above error.
Funny thing is that I now get the same error also for 'TDP' clients NOT
backing up via Ethernet but via TR.
Does this mean that TSM Server can not cope in time with incoming data ?

I did increase some TCPIP settings but without any result.
Can anyone help me with this ?

Thanks,
Paul

TSM Server : 4.1.30 running on OS390 MVS R10 (Upgrade to 4.2 next weekend)
TSM clients concerned : TDP for Lotus Domino V1.1.1.0 (Lotus Domino 5.0
running on WIN/NT)

Extraction DOMISCH.LOG

   02/13/2002 19:26:02 ANS1017E (RC-50)  Session rejected: TCP/IP
   connection failure
   02/13/2002 19:26:08 Backup of Reservation\MBResource.nsf failed.
   02/13/2002 19:26:08 ANS1017E (RC-50)  Session rejected: TCP/IP
   connection failure
   02/13/2002 19:26:10 Backup of Reservation\poolCarReserv.nsf failed.
   02/13/2002 19:26:10 ANS1017E (RC-50)  Session rejected: TCP/IP
   connection failure
   02/13/2002 19:26:16 Backup of Reservation\ResourceISD.nsf failed.
   02/13/2002 19:26:16 ANS1017E (RC-50)  Session rejected: TCP/IP
   connection failure
   02/13/2002 19:26:18 Total Domino databases inspected:         529
   02/13/2002 19:26:18 Total Domino databases backed up:         212
   02/13/2002 19:26:18 Total Domino databases excluded:          6
   02/13/2002 19:26:18 Total Domino backup objects expired:      0
   02/13/2002 19:26:18 Throughput rate:                          2,271.94
   Kb/Sec
   02/13/2002 19:26:18 Total bytes transferred:
   11,437,230,890
   02/13/2002 19:26:18 Elapsed processing time:                  4,916.14
   Secs
   02/13/2002 19:26:18 ACD0151E Errors occurred while processing the
   request.

Extraction DSIERROR.LOG

   02/13/2002 18:07:10 TcpFlush: Error 10054 sending data on Tcp/Ip socket
   1012.
   02/13/2002 18:07:10 sessSendVerb: Error sending Verb, rc: -50
   02/13/2002 18:07:10 TcpFlush: Error 10054 sending data on Tcp/Ip socket
   1012.
   02/13/2002 18:07:10 TcpFlush: Error 10038 sending data on Tcp/Ip socket
   4294967295.
   02/13/2002 18:07:10 sessSendVerb: Error sending Verb, rc: -50
   02/13/2002 18:07:12 TcpFlush: Error 10054 sending data on Tcp/Ip socket
   1020.

Settings in DSM.OPT from TDP client :

     TXNBytelimit   25600
     TCPWindowsize 63
     TCPBuffsize 512
     TCPNodelay Yes
     Compression Off

Some settings on TSM Server :

     CommTmeOut 900
     BufPoolSize 32768
     TxnGroupMax 256
     MoveBatchSize 1000
     UseLargebuffers Yes
     MoveSizeTresh 500
     SelTuneBufPoolSize Yes
     SelfTuneTxnSize Yes
     TCPBufSize 32768
     LogpoolSize 512