The secure and robust functioning of a network relies on
the defect-free implementation of network applications. As
network protocols have become increasingly complex, however,
hand-writing network message processing code has become
increasingly error-prone.

In this paper, we present a domain-specific language,
Zebu, for generating robust and efficient message processing
layers. A Zebu specification, based on the notation used in
RFCs, describes protocol message formats and related processing
constraints. Zebu-based applications are efficient,
since message fragments can be specified to be processed
on demand. Zebu-based applications are also robust, as
the Zebu compiler automatically checks specification consistency
and generates parsing stubs that include validation
of the message structure. Using a message torture suite in
the context of SIP and RTSP, we show that Zebu-generated
code is both complete and defect-free.