Window Scaling (RFC 1323), 1/3 Previously in Windows, but off by default We ran into a number of problems testing it for Vista: IGD problems: multiple popular vendors, popular models Popular vendor #1, several models having SPI block TCP handshake with WS: automatic detection and recovery at end system Popular vendor #2, models with SPI drop packets on connections after a large scaling factor (>2) successfully negotiated during initial handshake: no way to recover at TCP layer Firewall problems: multiple vendors have almost identical bug in old versions Multiple popular vendors, multiple old models (one only if a non-default feature enabled) drop packets if scaling factor > 2 has been negotiated Core Issue: Broken firewall logic that does not scale window in TCP headers correctly while determining how much data to let through |