"Protocol Boosters" are modules inserted into Protocol graphs. They allow the protocol's behavior to adapt to its environment. Boosters can mask undesirable properties of links or subnets in an internetwork. The method permits use of proprietary protocols and supports end-to-end optimizations. We have implemented Protocol Boosters support in the FreeBSD version of UNIX for Intel architecture machines. Our prototype embeds boosters in the 4.4 BSD-Lite Internet protocol (IP) stack. We have measured the performance of two prototype boosters: an encryption booster (for passage across insecure subnets) and a compression booster (passage across bandwidth-impaired subnets). Our measurement data suggests that OS support for this method can be constructed with low performance overhead: execution of the protocol elements dominates any overhead introduction by our implementation. We discuss some lessons learned from implementation.