Self-Organizing Communication Services in Future Network Architectures Rahamatullah Khondoker # , S. M. Taslim Arif $ , Nathan Kerr # , Dennis Schwerdel # # Integrated
Communication Systems, University of Kaiserslautern, 67655 Kaiserslautern, Germany {khondoker, kerr, schwerdel}@informatik.uni-kl.de $ Fraunhofer Institute of Experimental Software Engineering, Kaiserslautern, Germany
[email protected]
I. I NTRODUCTION Adding new functionality into the current Internet architecture is difficult because of the tight-coupling in network protocol stacks. One method of creating loosely-coupled network stacks is to split the functionality of the entire stack into a set of services. Each service provides a specific function known as a capability. Creating a network stack from these communication services is done through service composition [1]. Service composition selects services in a manner that fulfills an overall goal and composing them into a new network stack. Selection is usually performed by searching a set of service descriptions for the desired capabilities and qualities desired for the overall result. Here we describe a method of using self-organization for communication service composition. II. S ELF -O RGANIZING S ERVICE C OMPOSITION The basic unit in this approach is a communication service. Each service provides a capability and is able to communicate with other communication services. Capabilities are organized in an ontology [2]. The capabilities are ordered such that a working network stack could be built. For example, compression must be done before encryption. An environment in which self-organizing service composition could operate is shown in figure 1. Let us assume that an application wants to send audio data to a peer on the network. This requirement is sent to a service agent through a network abstraction API. The service agent translates the requirements into an ordered list of capabilities by using the ordered ontology previously described. The service agent could produce something like the following list of capabilities: low pass filtering, compression, encryption, error detection, error correction and transmission. To initiate a self-organized network stack, the service agent sends a broadcast message to all the services asking which one(s) provide the first capability, in this case low pass filtering. Each service that provides the capability will respond with additional qualitative information such as cost, bandwidth required, etc. The best of these offers will be selected as the first service in the stack. This process will be referred to
Fig. 1.
A Model for Self-organizing network service composition
as findService(capabilities). A method such as AHP [3] can be used for this. The service agent will then call that service’s findNextCapabilityProvider function (see algorithm 1), which starts the self-organization process. When a particular service in a service pool has its findNextCapabilityProvider function called, it assumes responsibility to create the network stack. In our scenario, the low pass filtering capability provider gets the CapabilitiesRequired = {low pass filtering, compression, encryption, error detection, error correction and transmission}, an empty network stack, and the address of the service agent. The first step is to add itself to the network stack and note that its capability has been fulfilled. This is done by popping
Input: NetworkStack = empty CapabilitiesRequired = capability list from service agent ServiceAgent = Address of service agent Output: A composed network stack pop(CapabilitiesRequired); push(Self,NetworkStack); if (CapabilitiesRequired==NULL) then serviceAgent.Completed(NetworkStack); else nextService=findService(CapabilitiesRequired); nextService.findNextCapabilityProvider(NetworkStack, CapabilitiesRequired,ServiceAgent); end Algorithm 1: findNextCapabilityProvider
the list of capabilities required and pushing its own address onto the network stack. The service then searches for the service which fulfills the next capability in the list by calling findService with the now reduced list of capabilities. The responsibility of completing the network stack is passed on to the returned service. This process is continued until the CapabilitiesRequired is empty. As soon as the CapabilitiesRequired is empty, the network stack is sent to the service agent. Upon reception of the list of providers that will form the network stack, the service agent creates the specified stack and returns the resulting network connection to the application. III. A NALYSIS The described approach can be used during design-time, deployment-time, or run-time composition. Analysis of the computation and data requirements have not been made, nor has any attempt at optimization such as caching. Therefore we cannot determine the suitability of this approach as to when it should be used. This approach allows communication services to be distributed, which allows network engineers and developers to make their services available over the Internet. Should this happen, it will be necessary to make use of those services by using dynamic composition techniques. This approach can be used dynamically. IV. C ONCLUSION One method of loosely-coupling network stacks involves service composition. This approach is self-organizing where fine-grained active services communicate with each other to form the network stack based on requirements given by an application. It can be used for anywhere composition is needed, though actual performance characteristics are not known. R EFERENCES [1] C. Henke, A. Siddiqui, and R. Khondoker, “Network functional composition: State of the art,” in ATNAC’10: Proceedings of Australasian Telecommunication Networks and Application Conference. IEEE, 2010. [2] J. Euzenat and P. Shvaiko, Ontology Matching. Heidelberg: SpringerVerlag Berlin Heidelberg, 2007.
[3] R. Khondoker, B. Reuther, D. Schwerdel, A. Siddiqui, and P. Mueller, “Describing and selecting communication services in a service oriented network architecture,” in Beyond the Internet Innovations for future networks and services, Proceedings of the ITU-T Kaleidoscope event, Pune, India, 1315 Dec 2010. ITUT Kleidoscope, Pune, India: ITUT, 2010.
