Most of the flexibility that has been brought to the development of software defined radios resides in components that can be associated with the physical layer of the radio. This talk tries to shed some light on how SDRs can also benefit from flexibility in higher protocol layers such as link-layer protocols. Specifically, the talk introduces a component-based link-layer protocol architecture that allows to build self-contained protocol components that can be combined to complete link-layer protocol solutions in a Lego-like manner. The talk will cover some architectural aspects as well as some implementation-specific problems that we came across during the development of a prototype using Iris.