Uma arquitetura baseada em SCTP e SIP para suporte a aplicações VoIP móveis e a especificação formal do seu módulo de controle

New versions of SCTP protocol allow the implementation of handover procedures in the transport layer, as well as the supply of a partially reliable communication service. A communication architecture is proposed herein, integrating SCTP with the session initiation protocol, SIP, besides additional protocols. This architecture is intended to handle voice applications over IP networks with mobility requirements. User localization procedures are specified in the application layer as well, using SIP, as an alternative mean to the mechanisms used by traditional protocols, that support mobility in the network layer. The SDL formal specification language is used to specify the operation of a control module, which coordinates the operation of the system component protocols. This formal specification is intended to prevent ambiguities and inconsistencies in the definition of this module, assisting in the correct implementation of the elements of this architecture

Implementing telephony signalling over IP networks using SIGTRAN standards

Diplomityössä tutkitaan yhteiskanavamerkinantoverkon signalointiliikenteen siirtoa IP-pohjaisiin verkkoihin käyttäen IETF:n aliorganisaation, SIGTRAN:in, määrittelemiä standardeja. Tutkimuksen lisäksi työssä suoritetaan myös toteutus, joka mahdollistaa em. verkkojen yhdistymisen. Ensin työssä käsitellään yhteiskanavamerkinantoverkon tulevaisuus ja alan yleiset näkymät, jotka luovat pohjan työn toteutuksen ymmärtämiseen. Toiseksi työssä esitellään toteutuksessa käytetyt teknologiat. Esiteltäviin teknologioihin kuuluvat yhteiskanavamerkinantoverkko, IP-pohjainen verkko, SIGTRAN:in määrittelemät standardit, toteutustyökalut sekä ympäristö, johon toteutus liitetään. Toteutukseen olennaisesti liittyvät asiat ovat painotettuina teknologioiden esittelyssä. Diplomityön loppuosassa kuvataan merkinantoyhdyskäytävän toteutus suunnittelun ja toteutettujen toiminnallisuuksien osalta. Diplomityön tuloksena saatiin uusi testattu merkinantosovellus, joka täyttää yhteiskanavamerkinantoverkolle asetetut vaatimukset. Toteutus toimii osana Intellitel(TM) ONE palvelualustaa. Toteutuksen kehitys tulee jatkumaan.

Connectivity management and dynamic context grouping in mobile heterogenous systems

In the last 10 years the number of mobile devices has grown rapidly. Each person usually brings at least two personal devices and researchers says that in a near future this number could raise up to ten devices per person. Moreover, all the devices are becoming more integrated to our life than in the past, therefore the amount of data exchanged increases accordingly to the improvement of people's lifestyle. This is what researchers call Internet of Things. Thus, in the future there will be more than 60 billions of nodes and the current infrastructure is not ready to keep track of all the exchanges of data between them. Therefore, infrastructure improvements have been proposed in the last years, like MobileIP and HIP in order to facilitate the exchange of packets in mobility, however none of them have been optimized for the purpose. In the last years, researchers from Mid Sweden University created The MediaSense Framework. Initially, this framework was based on the Chord protocol in order to route packets in a big network, but the most important change has been the introduction of PGrids in order to create the Overlay and the persistence. Thanks to this technology, a lookup in the trie takes up to 0.5*log(N), where N is the total number of nodes in the network. This result could be improved by further optimizations on the management of the nodes, for example by the dynamic creation of groups of nodes. Moreover, since the nodes move, an underlaying support for connectivity management is needed. SCTP has been selected as one of the most promising upcoming standards for simultaneous multiple connection's management.

On the Cost of Using Happy Eyeballs for Transport Protocol Selection

Concerns have been raised in the past several years that introducing new transport protocols on the Internet has be- come increasingly difficult, not least because there is no agreed-upon way for a source end host to find out if a trans- port protocol is supported all the way to a destination peer. A solution to a similar problem—finding out support for IPv6—has been proposed and is currently being deployed: the Happy Eyeballs (HE) mechanism. HE has also been proposed as an efficient way for an application to select an appropriate transport protocol. Still, there are few, if any, performance evaluations of transport HE. This paper demonstrates that transport HE could indeed be a feasible solution to the transport support problem. The paper evaluates HE between TCP and SCTP using TLS encrypted and unencrypted traffic, and shows that although there is indeed a cost in terms of CPU load to introduce HE, the cost is rel- atively small, especially in comparison with the cost of using TLS encryption. Moreover, our results suggest that HE has a marginal impact on memory usage. Finally, by introduc- ing caching of previous connection attempts, the additional cost of transport HE could be significantly reduced.