Flexible host-based Handoff Selection for Next Generation Networks Michael Mackay 1 , Jose Moura 1,2 , Christopher Edwards 1 1 Computing Department, Infolab21, Lancaster University, LA1 4YU, UK, m.mackay, rochasae, ce@comp.lancs.ac.uk 2 ADETTI/ISCTE, Av. Forças Armadas, 1600-082 Lisboa, Portugal jose.moura@iscte.pt Abstract In contrast to the traditional ‘fixed’ network model, future devices will roam between points of attachment while maintaining the best Layer 2 connectivity. It therefore becomes critical for Mobile Nodes to determine semi-independently the most appropriate technology and Access Network for a given scenario. This supports both the dynamic selection of the ‘best’ point of attachment and near-seamless handoff. Several solutions have already been proposed both within standards bodies and the wider academic community. Our aim is to define an intelligent network selection mechanism, capable of representing and enforcing explicit user-defined parameters as part of a host-based handoff mechanism. Moreover, our proposal works both independently and in cooperation with network-based handoff mechanisms. 1. Introduction A critical aspect of Next Generation Networking (NGN) will be enabling Mobile Nodes to roam between networks with minimal interruption to active sessions. At Layer 3, Mobile IP is central to this, and now this has been standardised, the way is paved for deployments to begin. This however represents only upper-layer protocols as functionality at Layer 2 have yet to be finalised. Particularly, support for roaming between Access Networks (and selecting when and how to do this) is still underdeveloped as is supporting communication between Layer 2 and 3. This paper presents a host-based Intelligent Network Selection (INS) mechanism to support network roaming in Mobile Nodes (MNs) regardless of the configuration or capabilities of the device. We propose a management mechanism to monitor and coordinate the use of Layer 2 technologies on behalf of Layer 3 and higher processes. We achieve this by employing a module between Layer 2 and 3 that actively selects the most appropriate handoff based on a set of predefined requirements. The challenges we address here are ensuring interoperation with network-based handoff mechanisms while enforcing user preferences. The majority of the existing solutions focus on developing functionality within the network to support handoffs. This is on the basis that mobile devices are too limited in their capabilities to perform extensive internal management. Our contention, however, is that while this may be the case with current devices, there is an increasingly significant portion of the market (e.g. laptops and powerful handheld devices) that supports this functionality. Moreover, we expect that ‘expert’ users will demand more control over this process in terms of handoff selection. Our mechanism is also designed both to cooperate with ‘existing’ network- based approaches by defining ‘standard’ host functionality and it can also operate independently as a complete system in its own right. These two modes allow for the gradual deployment of our mechanism while enforcing user-defined preferences. This paper is organised as follows; Section 2 discusses related work and Section 3 provides an analysis of the INS problem space. Section 4 presents our design and Section 5 provides a performance analysis of the INS and we conclude by highlighting our contribution to the area and some further work. 2. Background and Related Work Choosing the optimal Access Network during handoffs is a critical aspect of service delivery in heterogeneous systems [4] as the selection of a non-optimal network can result in higher costs or poor service. Seventh International Conference on Networking 978-0-7695-3106-9/08 $25.00 © 2008 IEEE DOI 10.1109/ICN.2008.106 703 Seventh International Conference on Networking 978-0-7695-3106-9/08 $25.00 © 2008 IEEE DOI 10.1109/ICN.2008.106 703