We have actually seen better throughput here by setting ours to 128. This has doubled and in some tests tripled our throughput.
Tony Garrison I/T Sr. Systems Programmer USAA 210-913-9836 -----Original Message----- From: Gianluca Mariani1 [mailto:[EMAIL PROTECTED]] Sent: Wednesday, July 10, 2002 11:42 AM To: [EMAIL PROTECTED] Subject: Re: optimising tcpwindowsize and tcpbuffsizes I refer to our position as on the perf site. that is what I consider official as those are the recommendations of the perf team based on real tests. as I wrote in the other post. I'll quote again: "TCP/IP Window Size Use the Tivoli Storage Manager option TcpWindowSize 63 on both the Tivoli Storage Manager Windows NT client and Tivoli Storage Manager Windows NT server. Since Windows 2000 supports TCP window scaling, it may be beneficial to use a larger TCP window size for Windows 2000 systems that are communicating exclusively with other Windows 2000 or UNIX systems." Why? Because the maximum tcpwindowsize WITHOUT RFC 1323 (scaling windowsize support) is 65535 bytes, that's 64KB -1. TSM option tcpwindowsize 64 means 64*1024 or 65536 - one byte too big if the client doesn't support RFC 1323. win2000 does support rfc1323, but you have to set a registry entry to take advantage of it. the tcp windowsize sets the SO_RCVBUF option on the socket connection, which is the size of the total data buffered on the connection. MS docs say this size needs to be a multiple of the MTU for best results, but this is basically garbage. For standard Ethernet MTU of 1500 bytes, the difference in the number of packets that can be buffered between 63KB and 64KB is a nit. There is a difference between saying 64KB and meaning 65535 bytes. this does not mean that you can't put the parameter to 64 and actually see an improvement. I gave a general answer. I would be more careful with absolute assertions in this field. I'm somewhat disturbed that a certified TSM consultant is not aware of this. Cordiali saluti Gianluca Mariani Tivoli TSM Global Response Team, Roma Via Sciangai 53, Roma phones : +39(0)659664598 +393351270554 (mobile) [EMAIL PROTECTED] Mark Stapleton <stapleto@BERBEE. To: [EMAIL PROTECTED] COM> cc: Sent by: "ADSM: Subject: Re: optimising tcpwindowsize and tcpbuffsizes Dist Stor Manager" <[EMAIL PROTECTED] .EDU> 10/07/2002 15:35 Please respond to "ADSM: Dist Stor Manager" From: ADSM: Dist Stor Manager [mailto:[EMAIL PROTECTED]]On Behalf Of Gianluca Mariani1 > TCPWINDOWSIZE should be set to 63 on Win2k. >Cordiali saluti >Gianluca Mariani >Tivoli TSM Global Response Team, Roma You need to check your documentation. Windows 2K machines should have TCPWINDOWSIZE set to 64 (assuming 10 or 100Mb Ethernet). I'm somewhat disturbed that a member of the Tivoli TSM Global Response Team isn't aware of this. -- Mark Stapleton ([EMAIL PROTECTED]) Certified TSM consultant Certified AIX system engineer MCSE