I used tcpdump and tcptrace to dig up this data.

Basically, it appears that TCP window scaling is enabled on the ESMF as well as on opendap.optiputer.net, but the connections aren't all using it, limiting some of our communications to a max TCP window of 64K.  Any table entry below with a red "N" is having TCP window scaling (RFC 1323) trouble (other than "Not useful", of course).

	To seki.nac (Fedora Core 4, kernel 2.6.11-1.1369_FC4)	To nsc-1.nacs (Redhat Enterprise 3, kernel 2.4.21-37.EL)	To ESMF (AIX 5.1 ML 4)	To Opendap (CentOS 4.2, kernel 2.6.9)	To los angeles (CentOS 4.0, kernel 2.6.9-5.0.5.EL)
From seki.nac (Fedora Core 4, kernel 2.6.11-1.1369_FC4)	Not useful	Y/Y Y/Y	Y/Y Y/Y	Y/Y Y/Y	Y/Y Y/Y
From nsc-1.nacs (Redhat Enterprise 3, kernel 2.4.21-37.EL)	Y/Y Y/Y	Not useful	Y/Y Y/Y	Y/Y Y/Y	Y/Y Y/Y
From ESMF (AIX 5.1 ML 4)	Y/Y Y/Y	N/Y Y/Y	Not useful	Y/Y N/Y	N/Y Y/Y
From Opendap (CentOS 4.2, kernel 2.6.9)	Traffic into 128.200.34 blocked	Traffic into 128.200.34 blocked	N/Y Y/Y	Not useful	Y/Y Y/Y
From los angeles (CentOS 4.0, kernel 2.6.9-5.0.5.EL)	Traffic into 128.200.34 blocked	Traffic into 128.200.34 blocked	N/Y Y/Y	Y/Y Y/Y	Not useful