Vincent St-Amour PDF
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S3: the Small Scheme Stack A Scheme TCP/IP Stack Targeting Small Embedded Applications Vincent St-Amour Universit´e de Montr´eal Joint work with Lysiane Bouchard and Marc Feeley Scheme and Functional Programming Workshop September 20, 2008 1/37 Outline ◮ Motivation for a Scheme network stack ◮ Protocols supported by S3 ◮ Application program interface ◮ Implementation ◮ Related work ◮ Experimental results 2/37 Small embedded systems ◮ High volume ◮ Low cost ◮ Low memory ◮ Low computational power ◮ Need to interact with ◮ user (configuration,control) ◮ storage device (to keep logs) ◮ other embedded systems (automation, distribution) 3/37 Why use TCP/IP in embedded systems Networking infrastructure ◮ is ubiquitous (⇑ accessibility) ◮ gives access to many services (⇑ features) ◮ eliminates need for I/O periperals (⇓ cost) 4/37 Sample application: house temperature monitor NFS SMTP HTTP AD−HOC NETWORK 5/37 Goals ◮ Show that a network stack can be implemented in Scheme ◮ Why use Scheme? ◮ Why not? ◮ Scheme’s high-level features → compact code ◮ Portability to different Scheme implementations 6/37 Outline ◮ Motivation for a Scheme network stack ◮ Protocols supported by S3 ◮ Application program interface ◮ Implementation ◮ Related work ◮ Experimental results 7/37 Protocols supported by S3 OSI Model Layers 8/37 TCP ◮ Most complex protocol implemented in S3 ◮ Connection-based ◮ Server listens for connections on a port number ◮ Client connects to that port ◮ Stream paradigm ◮ Packets are acknowledgedby receiver ◮ Sender retransmits after timeout 9/37 Highlights of our approach ◮ We target very small systems (2 kB data, 32 kB program, < $5) ◮ Discard seldom-used features of the protocols ◮ Minimal buffering ◮ Polling-based API ◮ Scheme-specific ◮ PICOBIT Scheme virtual machine ◮ Higher-order functions 10/37
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