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An Architectural Framework for Supporting Distributed Object Based Routing

An Architectural Framework for Supporting Distributed Object Based Routing. Dhavy Gantsou Department of Computer Science University of Valenciennes France Dhavy.gantsou@univ-valenciennes.fr SIGAda 2002, D. Gantsou. Basic networking terminology and concepts: Protocol ?. In general

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An Architectural Framework for Supporting Distributed Object Based Routing

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  1. An Architectural Framework for Supporting Distributed Object Based Routing Dhavy Gantsou Department of Computer Science University of Valenciennes France Dhavy.gantsou@univ-valenciennes.fr SIGAda 2002, D. Gantsou

  2. Basic networking terminology and concepts:Protocol ? In general A set of rules that govern all activity involving two or more entities that exchange messages in order to accomplish a task SIGAda 2002, D. Gantsou

  3. Basic networking terminology and concepts:Routing protocol ? Activity = transmitting data (packets) from a host (sender) to a remote host (receiver). Task = routing Communicating entities = software components of hosts and devices performing routing (routers ). SIGAda 2002, D. Gantsou

  4. Basic networking terminology and concepts:Routing ? Route computing. Involves: • Exchange of update messages (routing tables) only between neighboring routers • Use of received routing tables to dynamically determine the best path that a packet should take to reach its destination. SIGAda 2002, D. Gantsou

  5. Basic networking terminology and concepts:Routing ? Route computing. Requires : • Coherent route maintenance (route insertion, change, and deletion), may be periodic • Real-time inter-router communication. Receiving update messages at wrong time leads to instabilities SIGAda 2002, D. Gantsou

  6. Basic networking terminology and concepts:Routing ? R7 R3 R1 R5 R4 R2 R6

  7. Basic networking terminology and concepts: Routing ? cont.  Route lookup •Forwarding packets received on an input network interface to an appropriate output interface for transmission across the Internet. SIGAda 2002, D. Gantsou

  8. Basic networking terminology and concepts:Routing protocols issues  Implement multiple algorithms that : • execute concurrently • interact to achieve a common goal Require real-time communication SIGAda 2002, D. Gantsou

  9. Basic networking terminology and concepts: networking domain specific issues  Co-existence of two alternative data representation, due to exchanges of data among hosts having different byte-ordering.  Packets loss implying retransmission  Data error involving retransmission  Retransmission requiring timer management  Varying and complicated message formats,  Asynchronous communication SIGAda 2002, D. Gantsou

  10. Basic networking terminology and concepts: Concluding remark Given the issues that they raise, routing protocols belong to the domain of large-scale, real-time applications How to implement routing software ? SIGAda 2002, D. Gantsou

  11. Routing software implementation:Designs Conventional (monolithic)  Distributed object based  A poor choice of technology can make the implementation tedious and difficult SIGAda 2002, D. Gantsou

  12. Conventional design For single processor targets  Uses C and C++  Extensive use of operating system features for implementing real-time functionality  Widely used by network designers May be for historical and business reasons SIGAda 2002, D. Gantsou

  13. Conventional design cont.  Needs specific procedures for performing: • network byte-ordering • mapping between the logical view and realistic messages  Not suitable for the implementation of next generation Internet’s architecture SIGAda 2002, D. Gantsou

  14. Ada95 technology based Prototype  Uses GLADE features to perform data representation operations  Consists on four major classes: • Router_Class • Shared_Object •Service_Manager •OSPF_Router SIGAda 2002, D. Gantsou

  15. Ada95 technology based Prototype  Router_Class : An abstract (virtual) class specifying the behavior of communicating entities (routers) Subclasses derived from Router_Class must provide real methods (operations) performing the functionality of the routers SIGAda 2002, D. Gantsou

  16. Class Router_Class With common, common_types; package Router_Class is pragma Remote_Types ; type Router_Class is abstract tagged limited private ;    procedure Update (Router : Access router_Class; Message : Common.Message_Type) is abstract ;    private type Router_Class is abstract tagged limited null record ; end Router_Class ; SIGAda 2002, D. Gantsou

  17. Ada95 technology based Prototype  Shared_Object : A class implementing concurrent query and/or modify methods that are inherent to the OSPF DR (designated router) concept. A single member of a set of OSPF routers, which is elected by its neighbors to serve as central point of contact for routing information exchange SIGAda 2002, D. Gantsou

  18. Class Shared_Object Generic type For_Multiple_Inheritence is tagged limited private ; package Virtual_DR is pragma Shared_Passive ; type Shared_Object is new For_Multiple_Inheritence with private ;    procedure Insert (DR : Access Shared_Object ; Msg : Common.Message_Type; Where: Natural ) ;    private type Shared_Object is new For_Multiple_Inheritence with null record ; end Virtual_DR ; SIGAda 2002, D. Gantsou

  19. package body Virtual_DR is    protected Acces_Control is    private    end protected Acces_Control ; protected body Acces_Control is    end protected Acces_Control ; procedure Insert (DR : Access Shared_Object ; Msg : Common.Message_Type; Where: Natural ) is    end Insert ; end Virtual_DR ; SIGAda 2002, D. Gantsou

  20. Ada95 technology based Prototype  Service_Manager : provides methods that enable: • to register distributed objects • clients (objects requiring services) to find and retrieve references of distributed objects providing remote services (server) SIGAda 2002, D. Gantsou

  21. Class Service_Manager With Router_Class, Common; package Service_Manager is Pragma Remote_Call_Interface ; type Router_Class_Ref is Access all Router_Class. Router_Class’Class ; type Remote_Router_Reference is record Router_Ref: Router_Class_Ref ; Router_Id : Common.Address ; end record ;    procedure Registry (Router : Access Router_Class_Ref; Router_ID: Common.Address ; Host : Common.Host_Name) ; function Give_Router_Reference(Key : Natural) return Router_Class_Ref ;    end Service_Manager ; SIGAda 2002, D. Gantsou

  22. package body Service_Manager is protected Synchro_Ref_Acces is procedure Registry (Router : Access Router_Class_Ref; Router_ID: Common.Address ; Host : Common.Host_Name) ; function Give_Router_Reference(Key : Natural) return Router_Class_Ref ;    private Router_Reference : Router_Reference_List ; end Synchro_Ref_Acces ; protected body Synchro_Ref_Acces is procedure Registry (Router : Access Router_Class_Ref; Router_ID: Common.Address ; Host : Common.Host_Name) is    end Synchro_Ref_Acces ; procedure Registry (Router : Access Router_Class_Ref; Router_ID: Common.Address ; Host : Common.Host_Name) is begin Synchro_Ref_Acces.Registry(Router, Router_ID,Host) ;    end Service_Manager ; SIGAda 2002, D. Gantsou

  23. Ada95 technology based Prototype  Ospf_Router : a class implementing methods that perform the functionality of a router running the Open Shortest Path First(OSPF) protocol. • Provides methods that perform : - basic routing functionality - OSPF specific services such as the designated router concept (Class Shared_Object) • Must inherit methods from Router_Class and Shared_Object (multiple inheritance ) SIGAda 2002, D. Gantsou

  24. Class OSPF_Router With Router_Class, Virtual_DR , …; package OSPF_Router is Pragma Remote_Types ; type OSPF_Router is new Router_Class.Router_Class with record    end record ; package VDR is new Virtual_DR (OSPF_Router) ; type DR is new VDR.Shared_Object with null record ;    procedure Update (Router : Access OSPF_Router ; Message : Common.Message_Type) ;    end OSPF_Router ; SIGAda 2002, D. Gantsou

  25. With Ada.Real_Time, Service_Manager, …; package body OSPF_Router is    Local_Router : Aliased OSPF_Router ; Local_DR : Aliased DR ; package VDR is new Virtual_DR (OSPF_Router) ; type DR is new VDR.Shared_Object with null record ; procedure Update (Router : Access OSPF_Router ; Message : Common.Message_Type) is    begin Insert.(Local_DR’Acces, Message, Hash(Service_Manager.Give_Router_Reference(Message.Source_Message))) ;    end Update ; declare    begin Service_Manager.Registry(Local_Router’Access, Host_ID ,Host_Name) ;    end OSPF_Router ; SIGAda 2002, D. Gantsou

  26. ? SIGAda 2002, D. Gantsou

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