  This paper puts forth a networking paradigm, referred to as just-in-time
(JIT) communication, to support client-server applications with stringent
request-response latency requirement. Of interest is not just the round-trip
delay of the network, but the actual request-response latency experienced by
the application. The JIT framework contains two salient features. At the client
side, the communication layer will 'pull' a request from the client just when
there is an upcoming transmission opportunity from the network. This ensures
that the request contains information that is as fresh as possible (e.g., a
sensor reading obtained just before the transmission opportunity). At the
server side, the network ascertains that the server, after receiving and
processing the request to generate a response (e.g., a control command to be
sent to the client), will have a transmission opportunity at just this time. We
realize the JIT system, including the protocol stack, over a
Time-Division-Multiple-Access (TDMA) network implemented on a System-on-Chip
(SoC) platform. We prove that a TDMA network with a power-of-2 time slots per
superframe is optimal for realizing the server-side JIT function. Our
experimental results validate that JIT networks can yield significantly lower
request-response latency than networks without JIT support can.
