Tomasz Mrugalski

Analysis of IPv6 handovers in IEEE 802.16 environment

The second generation of WiMAX solutions, based on IEEE 802.16-2005 standard, offers limited mobility support. Unfortunately, after quickly changing the point of attachment on the WiMAX data link layer (DLL), very slow and inefficient IPv6 reconfiguration takes place. Delays introduced by automatic configuration (DHCPv6 and IPv6 protocols) and Mobile IPv6 can easily diminish or even render useless all benefits gained using the efficient handover performed on DLL. As handover is a crucial process in mobile cellular environments, reasons behind delays introduced by IPv6 layer mechanisms have to be analyzed and appropriate countermeasures applied.In order to analyse influence of different factors on the handover delay a simulation environment modelling the full handover procedure in a WiMAX environment has been developed. It allows simulation and analysis of various mobility related issues, offering support for multiple base stations with groups of subscribers, both fixed and mobile, with various mobility models. Also support for tight integration with higher layers (IPv6, DHCPv6, and Mobile IPv6) is fully implemented. All stages of full IPv6 handover in IEEE 802.16 environment, focusing on major reasons of reconfiguration delays are described.The paper presents components, functional requirements and architecture of the simulation environment, together with example simulation results. The obtained results clearly show that most significant delays are caused by the IPv6 layer. The areas of improvement in several autoconfiguration mechanisms are identified. Proposals include novel use of DHCPv6 relays for remote configuration, solving DAD delays, limiting Binding Update procedure in Mobile IPv6, and configuring routing through DHCPv6 communication.A universal metric for assessing impact of every stage on handover efficiency is also defined. Several proposed improvements to the IPv6 handover process are evaluated. Discussion regarding possible generalization of best improvement proposals and remarks on further research areas conclude this paper.

Extension Management of a Knowledge Base Migration Process to IPv6

There are many reasons to deploy IPv6 protocol with IPv4 address space depletion being the most indisputable. Unfortunately, migration to the IPv6 protocol seems slower than anticipated. To improve pace of the IPv6 deployment, authors of the article developed the two applications -- IPv6 Migration Guide and IPv6 Knowledge Builder -- that support the migration process. Their main purpose of both applications is to help less experienced network administrators facilitate the migration process. Even though both application are generic in principle, they are focusing on enabling IPv6 in SOHO networks at this stage of development. This paper presents IPv6 Migration Guide with detailed description of available network detection techniques. A prototype of IPv6 Knowledge Builder application, its design concepts, intended usage scenarios and development details are also presented. It will allow extending existing knowledge base by defining new knowledge entities (questions, answers, advices and tests) to IPv6 Migration Guide in an easy manner. Used together with already developed IPv6 Migration Guide tool, it will provide significant assistance to network administrators during IPv6 enabling phase.

Remote DHCPv6 autoconfiguration for mobile IPv6 nodes

During interdomain handover, IPv6 node requires a new address at its new location. Once the L2 handover procedure is completed, the mobile node (MN) starts its IPv6 configuration process, using stateless (router advertisements) or stateful (DHCPv6) mode. When so-called care-of address (CoA) is assigned, its uniqueness has to be verified, using Duplicate Address Detection (DAD) procedure. Depending on a network type, this procedure may even take more than 1000ms. The obtained CoA can be used only when configuration and DAD procedures are completed for informing corresponding nodes about new MN location. Such significant delay introduces unacceptable gaps in communication capability. This paper proposes a new mechanism that enables obtaining IPv6 address and other configuration options in advance, before actual handover is performed. MN contacts its destination location and obtains its new parameters, while still maintaining connectivity at old location. Such a priori knowledge about target location configuration may be exploited to speed up configuration process itself, but also to initiate Mobile IPv6 operations earlier, thus further shortening delays. Mechanism itself and its verification techniques are discussed. Results of extensive simulations, statistical analysis as well as areas of further study conclude this paper.

How to Improve the Efficiency of IPv6 Handovers in IEEE 802.16 Networks

The first generation of fully conformant IEEE 802.16-based networks is being deployed throughout the world. Most of these networks do not support full mobility, due to radio access layer limitations. Newer solutions, based on IEEE 802.16-2005 standard, offer mobility support for subscriber stations. Unfortunately, after quickly changing the point of attachment on the WiMAX layer, very slow and inefficient IPv6 reconfiguration takes place. Delays introduced by DHCPv6 stateless automatic configuration and mobile IPv6 can easily diminish or even render useless all benefits gained using the efficient WiMAX - data link layer. IPv6 automatic configuration process was not designed with fast reconfiguration in mind. As handover speed is a crucial requirement in mobile cellular environments, reasons behind delays introduced by IPv6 layer mechanisms have to be analyzed and appropriate countermeasures applied. Proposals include novel use of DHCPv6 relays for remote configuration, solving DAD delays, limiting Binding Update procedure in Mobile IPv6, configuring routing through DHCPv6 communication and some other. This paper describes all stages of full IPv6 handover in IEEE 802.16 environment, focusing on major reasons of reconfiguration delays. A new metric for assessing impact of every stage on handover efficiency is defined. Several proposed improvements to the IPv6 handover process are evaluated and simulation results are presented. A discussion regarding possible generalization of best improvement proposals and further research areas concludes this paper.

Numbat - extensible simulation environment for mobile, IPv6 capable IEEE 802.16 stations

Numbat is a new simulation environment, developed with IPv6 mobile stations supporting WiMAX in mind. To provide near real-time capabilities (required for VoIP or video streaming) in a mobile environment, full handover procedure has to be as fast as possible. Both investigated components - IEEE 802.16 based networks and IPv6 capable nodes - are rapidly gaining acceptance. Therefore it appears essential to perform full scale analysis of the handover procedure in such an environment. Numbat allows simulation and analysis of various mobility related issues. It offers support for multiple base stations with groups of subscribers, both fixed and mobile. Also support for tight integration with higher layers (IPv6, DHCPv6, Mobile IPv6) is usable, but still under development. This paper presents the purpose, functional requirements and architecture of the simulation environment. The current state of implementation, validation, future areas of improvement and an example simulation results are also discussed in detail. Obtained results clearly show that most significant delays are caused by the IPv6 layer. Some of the possible areas of improvement in several auto-configuration mechanisms are identified. Some optimization proposals are also discussed.

Knowledge Managemenent in the IPv6 Migration Process

There are many reasons to deploy IPv6 protocol with IPv4 address space depletion being the most obvious. Unfortunately, migration to IPv6 protocol seems slower than anticipated. To improve pace of the IPv6 deployment, authors of the article developed an application that supports the migration process. Its main purpose is to help less experienced network administrators to facilitate the migration process with a particular target usage being SOHO networks.

Remote stateful autoconfiguration for mobile IPv6 nodes with server side Duplicate Address Detection

During interdomain handover, IPv6 node has to acquire new address at its new location. Once the L2 handover procedure is completed, mobile node (MN) starts its IPv6 configuration, using stateless (router advertisements) or stateful (DHCPv6 communication) mode. After the address is obtained, its uniqueness has to be verified, using Duplicate Address Detection (DAD) procedure. Depending on the interface type, this procedure may easily take more than 1000ms. Assigned address can be used only after DAD procedure is complete, e.g. for informing corresponding nodes (CNs) about new MN location. DAD procedure introduces unwanted delays in handover and reconfiguration process. In the paper new mechanism that moves the burden of address uniqueness verification from mobile IPv6 nodes to static DHCPv6 servers is proposed. Proposed server-side DAD mechanism is presented, together with validation techniques used to verify its usefulness. The paper also proposes updated, recently introduced [16] mechanism that enables IPv6 address acquisition and other configuration options in advance, before actual handover is performed. Mechanism itself and its verification techniques are discussed. Results of extensive simulation experiments performed in a mobile WiMAX network with IPv6 support, statistical analysis as well as areas of further study conclude this paper.

Next generation automatic IP configuration deployment issues

Although Dynamic Host Configuration Protocol for IPv6 (DHCPv6) protocol was defined in 2003, it was designed as a framework rather than a complete solution to the automatic configuration in IPv6 networks. There are still some unsolved problems and new options yet to be defined. One example of such case is Fully Qualified Domain Name (FQDN) option, which final version has been published in late 2007. It describes DHCPv6 client and server behavior, but some important aspects remain unaddressed. Authors developed and released working open source implementation over a year before FQDN standard reached mature phase. This paper discuses those issues and recommends possible solutions. Another important development area in the DHCPv6 protocol is a lack of well defined authentication and authorization. Experimental AAA implementation has been developed and reached validation phase. Quick overview of the Dibbler project - a working, multi-platform, open-source DHCPv6 implementation - is also provided, its strengths, used solutions and validation methods used to prove its correctness are discussed. Conclusions and discussion regarding areas for further studies appears in the last section of this article.