Emad Aboelela

Wireless sensor network based model for secure railway operations

The current state of the art in detecting immediate and long-term railway track problems involves both inspectors walking the track lines and train cars instrumented with accelerometers and ultrasonic sensors that are capable of detecting wear of the rail and breakages. Additionally, a widespread practice of sensing rail continuity by using the tracks to complete simple circuits is in place. In this paper, we propose a fundamentally different approach to improve the current practices in railway operations using wireless sensor network (WSN). The primary technical and scientific objectives of the system introduced in this paper are to generate innovative solutions for a number of the issues facing the railroad community through the development of a system based on WSN. The objectives from a railroad perspective include finding new approaches to reduce the occurrence rate of accidents and improving the efficiency of railroad maintenance activities

A parallel IP-address forwarding approach based on partitioned lookup table techniques

As traffic on the Internet has increased exponentially, it is vital that Internet routers handle the received packets faster. When a router receives a packet, it has to make a decision where to send it next. To forward an IP packet, the routers need to lookup the destination address of the received packet in the forwarding table, implement forwarding algorithms, then forward the packet to the appropriate next hop or outgoing port. We discuss a parallel approach that combines an IP packet forwarding technique based on a partitioned lookup table with linear search on prefix lengths, binary search on prefix lengths, and LC (level-compressed) trie. Simulation results show that the proposed partition schemes speeds up the IP address lookup process.

RSVP: Resource Reservation Protocol

RSVP, a new resource reservation protocol, was designed to provide a mechanism for distributed applications to request a specified quality of service over the network. This new protocol is unique, in the sense that it uses a receiver-oriented resource reservation technique, and it is highly flexible in both operation and design. Key Terms: RSVP, resource reservation, bandwidth allocation

Wireless Local Area Network

A Wireless Local Area Network (WLAN) implements a flexible data communication system frequently augmenting rather than replacing a wired LAN within a building or campus. WLANs use radio frequency to transmit and receive data over the air, minimizing the need for wired connections. The Cisco 819HGW and Cisco 819HWD ISRs have a Host router software running on the first core. The second core runs the WLAN Access Point software. If WLAN is not supported in an SKU, all 1 GB DRAM memory is allocated to the first core. For the SKUs that support WLAN, 128 MB out of the 1 GB main memory is allocated to the second core. If WLAN is not supported in an SKU, all 1 GB compact flash memory is allocated to the first core. For the SKUs that support WLAN, 64 MB out of the 1 GB main memory is allocated to the second core.

IDEM: an Internet delay emulator approach for assessing VoIP quality

Network emulations are imitations of real-time network behavior that help in testing and assessing protocols, and other network related applications in a controlled hardware and software environment. Most of the emulators existing today are hardware implemented emulators. There is a rising demand to emulate the network behavior using a software tool. Our Internet delay emulator (IDEM) is a software tool that captures the network details and reproduces an environment useful for research oriented projects. IDEM is based on bouncers that are distributed over the Internet. The concepts of firewall routing are used in designing IDEM. IDEM supports both TCP and UDP applications. Rigorous testing shows that actual delay in data sent is accurately modeled by IDEM. Advantages of IDEM especially for delay sensitive applications like VoIP are discussed.

Firewalls and VPN: Network Security and Virtual Private Networks

This chapter illustrates the role of firewalls and Virtual Private Networks (VPNs) in providing security to shared public networks such as the Internet. Computer networks are typically a shared resource used by many applications for many different purposes. Sometimes the data transmitted between application processes is confidential, and the application users prefer that others not be able to read it. A firewall is a specially programmed router that sits between a site and the rest of the network. It allows the system administrator to implement a security policy in one centralized place. Filter-based firewalls are the simplest and most widely deployed type of firewall. A VPN is an example of providing a controlled connectivity over a public network such as the Internet. VPNs utilize a concept called an IP tunnel, in which a virtual point-to-point link is established between a pair of nodes that are actually separated by an arbitrary number of networks. Whenever the router at the entrance of the tunnel wants to send a packet over this virtual link, it encapsulates the packet inside an IP datagram.

Token Ring: A Shared-Media Network with Media Access Control

This chapter illustrates the implementation of a token-ring network. It helps in examining the performance of the token-ring network under different scenarios. A token-ring network consists of a set of nodes connected in a ring. The ring is a single shared medium. The token-ring technology involves a distributed algorithm that controls when each node is allowed to transmit. All nodes visualize all frames, and the node identified as the destination in the frame header saves a copy of the frame as it flows past. The token is just a special sequence of bits that circulates around the ring. Each node receives and then forwards the token. When a node that has a frame to transmit sees the token, it takes the token off the ring and instead inserts its frame into the ring. When the frame makes its way back around to the sender, this node strips its frame off the ring and reinserts the token. The token holding time (THT) generally is the time a given node is allowed to hold the token.

Network Design: Planning a Network with Different Users, Hosts, and Services

This chapter illustrates the basics of designing a network and emphasizes on the users, services, and locations of the hosts. It is noted that optimizing the design of a network is a major issue. Simulations are usually required to analyze the conceptual design of the network. The initial conceptual design is usually refined several times until a final decision is made to implement the design. The objective is to have a design that maximizes the network performance, taking into account the cost constraints and the required services to be offered to different types of users. After the network has been implemented, network optimization should be performed periodically throughout the lifetime of the network in order to ensure maximum performance of the network and to monitor the utilization of the network resources. The chapter also explores how different design decisions can affect the performance of the network.

RSVP: Resource Reservation Protocol: Providing QoS by Reserving Resources in the Network

This chapter illustrates the Resource Reservation Protocol (RSVP) as a part of the integrated services approach in order to provide Quality of Service (QoS) to individual applications or flows. For many years, packet-switched networks have offered the promise of supporting multimedia applications, such as audio, video, and data. A network that can provide different levels of service is often said to support QoS. Two approaches developed to provide a range of QoS include integrated services and differentiated services. The RSVP follows the integrated services approach, whereby QoS is provided to individual applications or flows. The differentiated services approach provides QoS to large classes of data or aggregated traffic. One of the key assumptions underlying RSVP is that it should not detract from the robustness that is found in the Internet. RSVP uses the idea of “soft state” in the routers. “Soft state” in connection-oriented networks does not need to be explicitly deleted when it is no longer needed. Instead, it times out after some fairly short period if it is not periodically refreshed.

Queuing Disciplines: Order of Packet Transmission and Dropping

This chapter examines the effect of different queuing disciplines on packet delivery and delay for different services. It is noted that as a part of the resource allocation mechanisms, each router must implement some queuing discipline that governs how packets are buffered while waiting to be transmitted. Various queuing disciplines can be used to control, which packets get transmitted and which packets get dropped. The queuing discipline also affects the latency experienced by a packet, by determining how long a packet waits to be transmitted. Some of the common queuing disciplines are first-in-first-out (FIFO) queuing, priority queuing (PQ), and weighted-fair queuing (WFQ). In FIFO queuing, the first packet that arrives at a router is the first packet to be transmitted. PQ is a simple variation of the basic FIFO queuing. Each packet is marked with a priority; the mark can then be carried. WFQ allows a weight to be assigned to each flow. This weight effectively controls the percentage of the links bandwidth each flow can get.