Bhaskar Sardar

A survey of tcp enhancements for last-hop wireless networks

TCP continues to be an important transport-layer communication protocol that is typically tuned to perform well in traditional wired networks, where bit error rate (BER) is low and congestion is the primary cause of packet loss. The emergence of various mobile access networks has prompted researchers to look for suitable modifications to TCP so as to make it survive in the wireless era as well. Networks with wireless links and mobile hosts incur significant losses due to high BER, host motion, and handoff mechanisms. Mobile devices face temporary and unannounced loss of network connectivity when they move. They are likely to have scarce resources, and they react to frequent changes in the environment. Motion causes varying, increased delays and packet losses, while the network learns how to deliver packets to the new location of the host. TCP incorrectly interprets these delays and losses as signs of network congestion and throttles its transmission rate, causing degraded end-to-end performance. This article provides an in-depth survey of various TCP enhancements which are specifically targeted for last-hop wireless environments. The objective is to review the performance issues of TCP variations, when employed in last-hop wireless networks, and to provide a categorized analysis of different existing solutions comparatively, as we all know that it is difficult to create a “one size fits all” TCP for last-hop wireless networks.

Performance analysis of Basic Support Protocol (BSP) in nested Network Mobility (NeNEMO)

The IETF has standardized NEtwork MObility (NEMO) Basic Support Protocol (NEMO BSP) to support network mobility. It uses a specialized mobile router (MR) that directly connects to the cellular network. However, in some situations, to maintain connectivity, one MR may come under the control of another MR resulting in nested NEMO (NeNEMO). The nesting can be multi-level too in the worst cases. In this paper, we develop an analytical model to analyze NEMO BSP in NeNEMO situation for determining its handoff delay and throughput. Our numerical analysis reveals that the handoff delay increases linearly with nesting levels, while throughput decreases sharply with an increase in the number of levels. Since this fact entails in deterioration in the application performance, it is important to decide on how many nesting levels NEMO BSP should allow such that both handoff delay and throughput do not suffer severely. We observe graphically that the maximum nesting level should not go beyond 2 for typical network configurations.

ROTIO+: A Modified ROTIO for Nested Network Mobility

The NEMO Basic Support (NBS) protocol ensures session continuity for all nodes in a moving network by maintaining a tunnel between Mobile Router (MR) and its Home Agent (HA). The NBS protocol, however, suffers from sub-optimality problem in routing, which gets amplified as the level of nesting increases [4]. The ROTIO [5] is a route optimization scheme for nested NEMO that restricts the number of tunnels to two thereby alleviating the pinball routing problem to a great extent. In this paper, we propose ROTIO+, a simple but practical extension of ROTIO scheme, to further reduce the number of tunnels to one in nested NEMO. In ROTIO+ scheme, the MR uses two binding updates (BUs): one to its HA and the other to the Top Level Mobile Router (TLMR). In the BU to its HA, it provides both the Care of Address (CoA) and Home Address (HoA) of the TLMR. Under normal circumstances, the HA routes all packets for the MR to the CoA of the TLMR. When the QoS decreases beyond a threshold i.e. the TLMR is changing the point of attachment, the HA sends the packet to the HoA of the TLMR. Thus, the scheme limits the number of visits to HA to one for a nested network and also has a fall back scheme when the TLMR changes point of attachment. The results show that it is an effective solution for route optimisation problem in nested NEMO.

A novel enhancement of TCP for on-board IP networks with wireless cellular connectivity

Abstract Network mobility (NEMO) allows various types of in-vehicle networks (e.g., WLANs inside public transport vehicle) to be seamlessly connected to the Internet. An on-board mobile router (MR) connects the moving network to the Internet by means of high-speed cellular mobile data services. Unlike terminal mobility, where the mobile hosts (MHs) connect to the cellular base station directly, MHs in NEMO encounter an additional wireless link (MR–MH) before they get connected to the Internet. In this paper, we first note the impact of this additional wireless link on the performance of the wireless enhancements of TCP and observe that the existing TCP enhancement schemes designed for conventional terminal mobility are not equally effective in NEMO. So, we propose an extension of TCP, called on-board TCP (obTCP), to effectively address the double wireless link related issues in NEMO. We compare obTCP against a classical scheme, called snoop, known for its effectiveness in terminal mobility, and analytically demonstrate that the performance gain of obTCP over snoop increases linearly with the delays, and non-linearly with the loss probabilities in the wireless links. Finally, we extend these analyses to obtain throughput models for snoop and obTCP in NEMO. The throughput models are validated through ns-2 simulations.

Optimization of probability of false alarm and probability of detection in cognitive radio networks using GA

In this paper, we optimize probability of detection and probability of false alarm in cognitive radio network to minimize probability of error of a particular SU in a centralized cognitive radio network using Genetic algorithm (GA). Our objective is to minimize probability of error and find out optimum values of probability of occupancy detection or probability of detection and probability of false alarm. We use Genetic Algorithm to solve this optimization problem. The result is compared with Differential Evolution algorithm and it is evident from the comparison that DE finds better solution and takes much lesser number of evaluations to find optimum solution.

SRAM based longest prefix matching approach for multigigabit IP processing

This paper proposes a novel hardware architecture based on static random access memory (SRAM) for longest prefix match (LPM) search scheme to achieve wire speed IP processing. The central idea of this architecture is to store the IP prefixes virtually in routing table. To virtually store IP prefixes, we reserve only a single bit per prefix irrespective of their lengths. The proposed architecture consumes single memory write cycle to store the IP prefixes those share common initial bits and also takes single memory read cycle for LPM search unlike conventional and existing LPM solutions. The read, write, update time complexity is O(1). This architecture exhibits LPM search time as approximately 1.25 ns and offers search throughput of 805.8 million-search/sec. The numerical results show that this architecture significantly reduces memory requirement, power consumption, and transistor-count/bit requirement.

Implementation and performance evaluation of a mobile IPv6 (MIPv6) simulation model for ns-3

Abstract Mobile internet protocol version 6 (MIPv6) is the base standard from the Internet Engineering Task Force (IETF) for Internet Protocol (IP) based mobility management in wireless networks. The next generation mobility management schemes are mainly following the protocol stack of MIPv6. However, till date the widely-used network simulator version 3 (ns-3) – which aims to replace the aging ns-2 and its associated old-featured simulators – does not have even in its latest version an MIPv6 module that is fully compliant to the IETF specification. To fill this gap, we present in this work a novel MIPv6 simulation model which can be integrated into ns-3. We explain the complete design logic of the module, and also perform evaluation of the same in ns-3. To validate our proposition, we compare its handoff performance results with both numerical results, obtained analytically, and published results, based on Linux test bed, CNI-MIPv6 test bed and Objective modular network testbed (OMNET++) simulation. To show the usefulness of our contribution, we have exemplified how hierarchical MIPv6 (HMIPv6) can be implemented by extending the basic MIPv6 module proposed by us.

Performance analysis of SINEMO and NEMO BSP for vehicle-infrastructure-vehicle communications

Network mobility (NEMO) basic support protocol (BSP) and seamless IP diversity based NEMO (SINEMO) have been designed to provide seamless and uninterrupted services to the mobile hosts in NEMO. SINEMO outperforms NEMO BSP by utilizing the advanced loss recovery and multi-homing feature of stream control transmission protocol (SCTP). To improve the performance of NEMO BSP, we could utilize the services of on-board TCP (obTCP) which implements local retransmission mechanism in the wireless links to recover wireless losses quickly and effectively. In this paper, we analytically compare NEMO BSP along with obTCP and SINEMO based on end-to-end packet loss probability, end-to-end packet delivery delay, handoff latency, and throughput degradation time during handoff. The numerical results show that NEMO BSP when used with obTCP performs better than SINEMO.

Performance analysis of CSMA/CA protocol during white space identification in cognitive radio networks

In this paper, we analyze the delay performance of distributed and centralized cooperative sensing approaches to find out which one is suitable for sensing inter packet white space. For simultaneous sharing of channels by primary users (PUs) and secondary users (SUs), the white space has duration of approximately 50 ms. In distributed cooperative sensing, the SUs perform carrier sense multiple access with collision avoidance (CSMA/CA) with distributed coordination function (DCF) for accessing common control channel to share sensing information among each other. In centralized cooperative sensing, SUs access common control channel to send sensing result to a fusion centre (FC) using CSMA/CA point coordination function (PCF) mechanism. Total delay of these two sensing approaches is given as the sum of total channel access delay and queuing delay. We find that for a particular number of SUs, the delay of sensing in centralized environment is within the permissible limit (i.e. within 50 ms). Although distributed cooperative sensing is much more reliable and scalable than centralized cooperative sensing, it has higher sensing delay than centralized sensing approach.

Security in Network Mobility (NEMO): Issues, Solutions, Classification, Evaluation, and Future Research Directions

The IETF has standardized network mobility (NEMO) basic support protocol (BSP) to extend Internet services to networks in motion such as in bus, trains etc. The NEMO BSP uses a bidirectional tunnel between the mobile router (MR) and its home agent (HA) resulting in suboptimal routing. Route optimization may be incorporated between the MR and the correspondent node (CN), by informing the HA and the CN about the MR’s current location through binding updates. However, these binding updates are vulnerable to different attacks as malicious users may send fabricated binding updates to fool the MR, the HA, and the CN. Although the path between the MR and the HA is protected by IPSec tunnel, the path between the MR and CN, between the HA and CN, and between a mobile network node and the MR remains unprotected. So the requirements of extending Internet services in NEMO and use of optimized route between the MR and the CN have introduced several security threats in NEMO. In this survey, we describe security requirements, issues, and attacks with their corresponding countermeasures in NEMO. Major attacks in NEMO include bombing attack, redirection attack, denial of service attack, man-in-the-middle attack, replay attack, home agent poisoning attack etc. These attacks can affect the integrity and privacy of data. This survey also provides an in-depth and categorized description of various security protocols and key management techniques which are specifically targeted for NEMO. Along the way we highlight the advantages and disadvantages of existing NEMO security protocols, evaluate them, and discuss open research issues.