Using Van Jacobson TCP/IP header compression on high-speed synchronous lines is not recommended, because---unlike Stac compression---it degrades performance. Stac compression is available on the Office Routers (OR-U, OR-HS, OR-LS) and on all PortMaster 3 products, but not on the PortMaster 2R, 2ER, and the IRX routers.
| ON | Compression is enabled. The PortMaster tries to negotiate both Van Jacobson and Stac LZS compression. |
| OFF | Compression is disabled. |
| STAC | Stac LZS data compression alone is enabled. |
| VJ | Van Jacobson TCP/IP header compression only is enabled. |