We have a 150MB TLS type circuit between our 2 main sites, connected to GB fiber ports on each end via Cat6509. File copies between servers with GB LAN connections 1 direction are fast (3 seconds for a 20MB file) but can take as long as 90 seconds the other way for the same 20MB file.
Flow control is enabled on the link and we do see RX Pauses incrementing, and we see retransmits occuring in the slow direction. It is not server specific and we have shown that local copies work fine.
The carrier has certified the WAN link as healthy and we are struggling with where to look next. Any suggestions?