An Architectural Framework for Supporting Distributed Object Based Routing Dhavy Gantsou Department of Computer Science University of Valenciennes France SIGAda 2002, D. Gantsou

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

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

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

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

R3 R5R4 R2 R7 R1 R6 Basic networking terminology and concepts: Routing ?

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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