ENSEIRB, FranceCall/CSeptember 29, 2003 Call/C: A Domain Specific Language for IP Telephony Services Claus Brabrand [ joint work with Charles Consel &

ENSEIRB, FranceCall/CSeptember 29, 2003 Call/C: A Domain Specific Language for IP Telephony Services Claus Brabrand [ joint work with Charles Consel & Fabien Latry ] COMPOSE Group INRIA, University of Bordeaux I, France

ENSEIRB, FranceCall/CSeptember 29, 2003 Outline  Introduction  Infrastructure (SIP)  Programming Telephony Services  Call/C  Examples  Domain Specific Analysis  Conclusion and Future Work

ENSEIRB, FranceCall/CSeptember 29, 2003 Introduction  Yesterday: "Call a place" 05 12 34 56 78

ENSEIRB, FranceCall/CSeptember 29, 2003 Introduction  Today: "Call a phone" 06 12 34 56 78 1-1

ENSEIRB, FranceCall/CSeptember 29, 2003 Introduction  Tomorrow: "Call a person" chirac@elysee.fr

ENSEIRB, FranceCall/CSeptember 29, 2003  SIP (Session Initiation Protocol ): Infrastructure (SIP)

ENSEIRB, FranceCall/CSeptember 29, 2003  SIP (Session Initiation Protocol ): Infrastructure (SIP) SIP Servers

ENSEIRB, FranceCall/CSeptember 29, 2003  SIP (Session Initiation Protocol ): Infrastructure (SIP) SIP Servers SIP Clients

ENSEIRB, FranceCall/CSeptember 29, 2003 Infrastructure (SIP) SIP Servers SIP Clients  SIP (Session Initiation Protocol ):

ENSEIRB, FranceCall/CSeptember 29, 2003 SIP (Registration) 1.2.3.4chirac

ENSEIRB, FranceCall/CSeptember 29, 2003 SIP (Registration) 1.2.3.4chirac chirac@1.2.3.4

ENSEIRB, FranceCall/CSeptember 29, 2003 SIP (Registration) 1.2.3.4chiracelysee.fr REGISTER 200 OK chirac@ 1.2.3.4 Location server: [chirac  1.2.3.4] 200 OK chirac@1.2.3.4

ENSEIRB, FranceCall/CSeptember 29, 2003 SIP (Registration) 1.2.3.4chiracelysee.fr REGISTER 200 OK chirac@ 1.2.3.4 Location server: [chirac  1.2.3.4] 200 OK chirac@1.2.3.4 chirac@elysee.fr

ENSEIRB, FranceCall/CSeptember 29, 2003  Call: chirac@elysee.fr  bush@whitehouse.gov SIP (Initiation) 1.2.3.4chiracelysee.frwhitehouse.gov5.6.7.8bush

ENSEIRB, FranceCall/CSeptember 29, 2003 SIP (Initiation) 1.2.3.4chiracelysee.frwhitehouse.gov5.6.7.8bush INVITE bush? Location server: [bush  5.6.7.8] 5.6.7.8 DNS lookup: whitehouse.gov? 200 OK accept ring ACK...multi-media communication...

ENSEIRB, FranceCall/CSeptember 29, 2003 SIP (Initiation) 1.2.3.4chiracelysee.frwhitehouse.gov5.6.7.8bush INVITE bush? Location server: [bush  5.6.7.8] 5.6.7.8 DNS lookup: whitehouse.gov? 200 OK accept ring ACK...multi-media communication... 200 OK 302 Moved Temporarily 486 Busy Here 603 Decline...

ENSEIRB, FranceCall/CSeptember 29, 2003 SIP (Initiation) 1.2.3.4chiracelysee.frwhitehouse.gov5.6.7.8bush INVITE bush? Location server: [bush  5.6.7.8] 5.6.7.8 DNS lookup: whitehouse.gov? 200 OK accept ring ACK...multi-media communication...

ENSEIRB, FranceCall/CSeptember 29, 2003 Programming Telephony Services call forward response fixed behavior lookup

ENSEIRB, FranceCall/CSeptember 29, 2003 Programming Telephony Services call response programmable

ENSEIRB, FranceCall/CSeptember 29, 2003 Programming Telephony Services call response programmable  Dependent on (time, request, preferences, state, …): if(…) else

ENSEIRB, FranceCall/CSeptember 29, 2003 Programming Telephony Services call response programmable  Dependent on (time, request, preferences, state, …):  Signalling actions:  lookup, forward, respond forward if(…) else

ENSEIRB, FranceCall/CSeptember 29, 2003 Programming Telephony Services call response programmable  Dependent on (time, request, preferences, state, …):  Signalling actions:  lookup, forward, respond  Non-signalling actions:  computations, remote procedure calls, side-effects,... forward y = f(x) if(…) else

ENSEIRB, FranceCall/CSeptember 29, 2003 Existing Solutions  General Purpose Languages:  SIP Common Gateway Interface (SIP/CGI)  Java SIP Servlets ...

ENSEIRB, FranceCall/CSeptember 29, 2003 Existing Solutions  General Purpose Languages:  SIP Common Gateway Interface (SIP/CGI)  Java SIP Servlets ... Expressive, but unsafe

ENSEIRB, FranceCall/CSeptember 29, 2003 Safety  Requirements for a call processing language:  Verifiability:  Call completion:  Safety of execution: ... "Programming Internet Telephony Services" -- J. Rosenberg, J. Lennox, and H. Schulzrinne

ENSEIRB, FranceCall/CSeptember 29, 2003 Safety  Requirements for a call processing language:  Verifiability:  Static syntactic/semantic analysis  Call completion:  Safety of execution: ... "Programming Internet Telephony Services" -- J. Rosenberg, J. Lennox, and H. Schulzrinne

ENSEIRB, FranceCall/CSeptember 29, 2003 Safety  Requirements for a call processing language:  Verifiability:  Static syntactic/semantic analysis  Call completion:  All calls handled (termination)  Safety of execution: ... "Programming Internet Telephony Services" -- J. Rosenberg, J. Lennox, and H. Schulzrinne

ENSEIRB, FranceCall/CSeptember 29, 2003 Safety  Requirements for a call processing language:  Verifiability:  Static syntactic/semantic analysis  Call completion:  All calls handled (termination)  Safety of execution:  Controlled access to underlying server and platform  Bounded resource consumption ... "Programming Internet Telephony Services" -- J. Rosenberg, J. Lennox, and H. Schulzrinne

ENSEIRB, FranceCall/CSeptember 29, 2003 Existing Solutions (cont’d)  General Purpose Languages:  SIP Common Gateway Interface (SIP/CGI)  Java SIP Servlets ... Expressive, but unsafe

ENSEIRB, FranceCall/CSeptember 29, 2003 Existing Solutions (cont’d)  General Purpose Languages:  SIP Common Gateway Interface (SIP/CGI)  Java SIP Servlets ...  Domain Specific Languages:  The Call Processing Language (CPL) Expressive, but unsafe

ENSEIRB, FranceCall/CSeptember 29, 2003 Existing Solutions (cont’d)  General Purpose Languages:  SIP Common Gateway Interface (SIP/CGI)  Java SIP Servlets ...  Domain Specific Languages:  The Call Processing Language (CPL) Expressive, but unsafe Safe, but inexpressive

ENSEIRB, FranceCall/CSeptember 29, 2003 Interaction Approach Rest of Internet Telephony Service

ENSEIRB, FranceCall/CSeptember 29, 2003 Interaction Approach Rest of Internet call Telephony Service

ENSEIRB, FranceCall/CSeptember 29, 2003 Interaction Approach Rest of Internet call lookup Telephony Service

ENSEIRB, FranceCall/CSeptember 29, 2003 Interaction Approach Rest of Internet call result lookup Telephony Service

ENSEIRB, FranceCall/CSeptember 29, 2003 Interaction Approach Rest of Internet call forward result lookup Telephony Service

ENSEIRB, FranceCall/CSeptember 29, 2003 Interaction Approach Rest of Internet call response forward result lookup Telephony Service

ENSEIRB, FranceCall/CSeptember 29, 2003 Implicit Control-Flow Rest of Internet call response forward result lookup Telephony Service

ENSEIRB, FranceCall/CSeptember 29, 2003 Manually save/restore state Rest of Internet call response forward result lookup Telephony Service SAVE SAVE RESTORE RESTORE

ENSEIRB, FranceCall/CSeptember 29, 2003 Session-Centered with High-Level Signalling Abstractions 1 Service Program Rest of Internet forward lookup call return

ENSEIRB, FranceCall/CSeptember 29, 2003 Explicit Control-Flow Rest of Internet forward lookup call return 1 Service Program

ENSEIRB, FranceCall/CSeptember 29, 2003 Automatically Compiled to Underlying model (with save/restore) Rest of Internet forward lookup call return SAVE;EXIT RESTORE RESTORE 1 Service Program

ENSEIRB, FranceCall/CSeptember 29, 2003 C-like core language with...  Safety restrictions:  Domain-specific extensions:

ENSEIRB, FranceCall/CSeptember 29, 2003 C-like core language with...  Safety restrictions:  Looping control structures: do / while / for  Recursion, pointers, array indexing,...  Domain-specific extensions:

ENSEIRB, FranceCall/CSeptember 29, 2003 C-like core language with...  Safety restrictions:  Looping control structures: do / while / for  Recursion, pointers, array indexing,...  Domain-specific extensions:  Session abstractions: incoming / outgoing  Signalling abstractions: forward / lookup / return  SIP address type: sip  Predefined structures: call / response  Predefined responses: ok / busy / decline /...

ENSEIRB, FranceCall/CSeptember 29, 2003  Decline calls outside working hours…: Call/C Example I bool isWorkHour() { time t = now(); if (t.weekday > FRIDAY) return false; return (t.hour >= 9) && (t.hour <= 17); } response incoming(call in) { if (!isWorkHour()) { return decline("OFFICE HOURS 9-17"); }

ENSEIRB, FranceCall/CSeptember 29, 2003  Forward depending on caller…: Call/C Example II sip WORK_PHONE = 'sip:office328@enseirb.fr'; sip CELL_PHONE = 'sip:claus_brabrand@bouygues.fr'; response incoming(call in) { if (in.from ~ [.*@enseirb.fr]) { in.subject = "[WORK: " + in.subject + "]"; return forward(in, WORK_PHONE); } else { return forward(in, CELL_PHONE); }

ENSEIRB, FranceCall/CSeptember 29, 2003  Forward unhandled calls to secretary…: Call/C Example III sip BOSS = 'sip:CEO@company.com'; sip SECRETARY = 'sip:secr@company.com'; response incoming(call in) { response x = forward(in, BOSS); switch (x) { case busy: case decline: in.subject = "[Fwd: " + in.subject + "]"; return forward(in, SECRETARY); default: return x; }

ENSEIRB, FranceCall/CSeptember 29, 2003 Domain Specific Analyses   Domain-specific optimization response x; … x = forward(in, 'sip:user@domain.com'); return x;

ENSEIRB, FranceCall/CSeptember 29, 2003 Domain Specific Analyses   Domain-specific optimization  Tail-call identification:  Disable script invocation after forward  Default (SIP server) behavior: propagate response response x; … x = forward(in, 'sip:user@domain.com'); return x;

ENSEIRB, FranceCall/CSeptember 29, 2003 Future Work  Composable services:  Specification and semantics  Interference analysis

ENSEIRB, FranceCall/CSeptember 29, 2003 Future Work  Composable services:  Specification and semantics  Interference analysis  Cost analysis:  Resource cost models for billing, admission control, server size prediction, …

ENSEIRB, FranceCall/CSeptember 29, 2003 Future Work  Composable services:  Specification and semantics  Interference analysis  Cost analysis:  Resource cost models for billing, admission control, server size prediction, …  Capability-based compilation:  Different users have different capabilities

ENSEIRB, FranceCall/CSeptember 29, 2003 Conclusion  Safety:  Verifiability  Call completion  Safety of execution

ENSEIRB, FranceCall/CSeptember 29, 2003 Conclusion  Safety:  Verifiability  Call completion  Safety of execution  Expressivity:  Enough for many interesting services (beyond CPL)

ENSEIRB, FranceCall/CSeptember 29, 2003 Conclusion  Safety:  Verifiability  Call completion  Safety of execution  Expressivity:  Enough for many interesting services (beyond CPL)  …and "usual" DSL benefits:  Conciseness, readability, maintainability, usability,...

ENSEIRB, FranceCall/CSeptember 29, 2003 Merci!

ENSEIRB, FranceCall/CSeptember 29, 2003 [ bonus slides ]

ENSEIRB, FranceCall/CSeptember 29, 2003 Session Abstractions: incoming / outgoing // declarations response incoming(call in) { // handle incoming call } response outgoing(call out) { // handle outgoing call }  Program bound to user (SIP address) dispatched when: in.to == user dispatched when: out.from == user

ENSEIRB, FranceCall/CSeptember 29, 2003 response incoming(call in) { response x; in.subject = "Hello!"; x = forward(in, 'sip:x@y.z'); return x; } Predefined Structures: call / response struct call { sip from; sip to; string subject; sip[] via; } union response { { } ok; // 200 OK { string contact; } redirect; // 302 MOVED TEMP’LY { } busy; // 486 BUSY HERE { string reason; } decline; // 603 DECLINE { int code; } error; // xxx ERROR... }

ENSEIRB, FranceCall/CSeptember 29, 2003 Domain Specific Analyses   Domain-specific verification: response incoming(call in) { … if (…) { … x = forward(in, s); … } … x = forward(in, 'sip:user@domain.com'); … return x; }

ENSEIRB, FranceCall/CSeptember 29, 2003 Domain Specific Analyses   Domain-specific verification: response incoming(call in) { … if (…) { … x = forward(in, s); … } … x = forward(in, 'sip:user@domain.com'); … return x; } Explicit control-flow!

ENSEIRB, FranceCall/CSeptember 29, 2003 Call/C: A Domain Specific Language for IP Telephony Services Claus Brabrand [ joint work with Charles Consel &

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ENSEIRB, FranceCall/CSeptember 29, 2003 Call/C: A Domain Specific Language for IP Telephony Services Claus Brabrand [ joint work with Charles Consel &

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