Rogier August Caspar Joseph Noldus

Assortativity in Complex Networks

We survey the concept of assortativity, starting from its original definition by Newman in 2002. Degree assortativity is the most commonly used form of assortativity. Degree assortativity is extensively used in network science. Since degree assortativity alone is not sufficient as a graph analysis tool, assortativity is usually combined with other graph metrics. Much of the research on assortativity considers undirected, non-weighted networks. The research on assortativity needs to be extended to encompass also directed links and weighted links. In addition, the relation between assortativity and line graphs, complementary graphs and graph spectra needs further work, to incorporate directed graphs and weighted links. The present survey paper aims to summarize the work in this area and provides a new scope of research. Keywords—Assortativity, Network, Graph, Graph Spectrum, Robustness, Degree, Degree correlation

Experience gained from IMS based Fixed Mobile Converged (FMC) network deployment

The present paper describes practical experience gained with IMS based Fixed Mobile Convergence (FMC) network deployment at TDC Denmark. The paper also takes a look into the near future, showing trend in technology. This network deployment, including the FMC component, is a joint project between TDC Denmark and Ericsson. The FMC implementation offers advanced services to enterprise users. Enterprise users may have a SIP phone, a GSM phone or both.

Effect of degree-preserving, assortative rewiring on OSPF router configuration

We study the impact of degree-preserving rewiring on the routing table configuration in an OSPF network. Degree-preserving rewiring may be applied to optimize specific network characteristics, such as assortativity. Rewiring has significant impact on IP router tables. This manifests itself through the number of nodes that are affected by the rewiring and the average number of routing table entries that are modified per affected node. Networks with high link density are generally less impacted. Through the use of Software Defined Networks (SDN), a number of rewiring steps can be aggregated, leading to fewer routing table updates in total. For aggregation of 15 - 20 rewiring steps, depending on network class and characteristics, almost all nodes in the network are affected.

IMS transit functionality: the missing link

The present paper introduces the concept of network based service triggering in IMS, as well as the functional entity that facilitates this. Network based service triggering ties in with the evolution in IMS interconnect networks and corporate IP networks. New SIP proxy functionality is proposed, Transit CSCF. This Transit CSCF may be realized through enhancement of an existing SIP proxy or may be realized as designated functional entity. The Transit CSCF enables transit SIP or SIP-I based networks to offer services for interconnected networks. One such service may be the connecting of IP-PBXs without requirement for registration of such PBX in the IMS network, but yet with optimized load distribution in IMS network. Transit CSCF leverages on the standardized service assertion methodology of IMS, namely the ISC reference point (of Serving CSCF). With the globalization of IMS networks, IMS interconnect becomes increasingly important for operators. IMS interconnect may be operated by independent parties. The usage of the IMS service control interface (ISC) reference point in transit networks further allows for third party service providers to offer services in these networks.

Adding value to enterprise and residential communication in the evolved multimedia communications network

The present paper builds on to previous papers presented at ICIN. We present and evaluate trends in the IMS network. Specifically, we look at how Multimedia communication service, including, but not limited to, voice calls, video calls and messaging, can be enhanced with Value Added Services (VAS). VAS has, since its inception two decades ago, undergone architectural changes, in order to adapt to and integrate with the IMS network. Many papers have been written on this topic and product development has been done. With Multimedia Telephony (MMTel), Voice-over-LTE (VoLTE) and Video-over-LTE becoming de facto standards for person-to-person communication in the 4G network, a renewed paradigm shift is needed for VAS. We have to ensure that VAS in the IMS/MMTel network does what its designed for: augmenting the end-user communication session, not controlling it. This has led to new insights lately. VAS, as we have known it since its inception, will evolve towards a concept & toolbox for enriching multimedia in the 4G mobile network, including both public communication networks and enterprise communication networks.

Operator-independent public user identities for IP multimedia communication services for enterprises

This paper describes usage of operator-independent Public user identities (PUI) for IP multimedia communication services for enterprises. This is a particular relevant topic for enterprises that wish to use their own domain name for public identification for (IMS based) communication services. Whereas usage of enterprises-specific domain names is common for services like mail and HTTP, it has some specific challenges for IMS based multimedia communication. These challenges include, among others: - uniform domain name for multimedia communication and other IP service, e.g. mail and http, without being tied to a single enterprise domain name administrator; - multi-IMS network subscription (within one country or across multiple countries); - non-country specific enterprise top level domain name (for example regional (e.g. .eu) or global (e.g. .com, .org) domain name); - real-time aspect of IMS services (as opposed to mail and http, which are not real-time).

Service enhancements for the converged communication network

The service layer in IMS is undergoing substantial architectural enhancement. IMS communication services, such as voice, video, messaging (incl. chat mode), are facilitated through designated and standardized SIP application servers. Traditionally, operators have a need for enhancing the service experience for their end-users [6]. These enhancements are implemented in the actual SIP-ASs as well as in separate application servers. Different methods are applied for connecting the separate application servers to said SIP-ASs. The advancements in service layer architecture are used also for creating services whereby a multitude of devices, using different communication protocols, are combined into a meta service. Smartphone, tablet and TV form, when connected to the IMS network, an integrated communication service. The present paper explores these advances in service layer architecture and sets out recommendations for further work.