MCA634 Advance Computer Networks

SNMP (Simple Network Management Protocol) 145 3. Communication Model:  Transfer syntax  SNMP over TCP/IP  Communication services addressed by messages  Security framework community-based model Managed LAN NMS 192.168.252.110 172.17.252.1 192.168.252.1 Router 2 Backbone Network Router 1 172.16.46.1 Hub 1 Hub 2 172.16.46.2 172.16.46.3 Fig. 7.6: Managed LAN  NMS on subnet 192.168.252.1 manages the router and the hubs on subnet 172.16.46.1 across the backbone network.  Information obtained querying the hubs.  Data truly reflects what is stored in the hub. CU IDOL SELF LEARNING MATERIAL (SLM)

146 Advanced Computer Networks Internet Management History 1970s: Advanced Research Project Agency Network (ARPANET) comes up with Internet control Message Protocol (ICMP) Internet Engineering Task Force (IETF)  1990 SNMPv1  1995 SNMPv2  1998 SNMPv3 Internet Documents  Request for Comments (RFC)  Internet Standard (IETF STD)  For your information (FYI) Organization Model MIB SNMP Manager agent agent Managed Objects Unmanaged Objects A simplified hierarchical (2-tier) setup Fig. 7.7: Organization Model  Describes components of a network management system  Focuses on functions and infrastructure  Objects are network elements such as hubs, bridges, routers, etc.  Managed elements have a process running on them called an agent  Manager queries the agent, gets information, processes it and stores it in the MIB CU IDOL SELF LEARNING MATERIAL (SLM)

SNMP (Simple Network Management Protocol) 147 System Overview Fig. 7.8: SNMP System Overview 7.7 Object Identifiers An SNMP object identifier uniquely names an object and identifies its location within a Management Information Base (MIB) tree structure. Object identifiers are application- independent Abstract Syntax Notation One (ASN.1) data types that consist of a sequence of non- negative integers or sub-identifiers. Object identifiers must have a minimum of two sub- identifiers and they must not exceed 128 sub-identifiers. The WinSNMP programming environment uses the smiOID structure to manage object identifiers. The format of the object identifier array in an smiOID structure is one sub-identifier per array element. The dotted numeric string representation of an object identifier separates its sub-identifiers with periods, e.g., “1.2.3.4.5.6”. Object Identifiers (OIDs) are used to identify SNMP objects. OIDs are structured as a pattern of numbers separated by dots and are used to indicate specific values that can be read from and/or CU IDOL SELF LEARNING MATERIAL (SLM)

148 Advanced Computer Networks written to by a remote host. These objects provide a place to store configuration, state, performance or other information which can be polled by an SNMP master or sent via an SNMP Trap. For example, the OID at which the MIB for Cisco Gear is located is: .iso.org.dod.private.enterprises.cisco or .1.3.6.1.4.1.9. The location in the MIB where this OID is located looks like this: .ccitt (0) .iso (1) |-.org (3) |-.dod (6) |-.internet (1) |-.directory (1) |-.mgmt (2) |-.mib-2 |-.system (1) |-.ip (4) |-.icmp (5) |-.tcp (6) |-.udp (7) |-.private (4) |-.enterprises (1) |-.cisco (9) Each SNMP trap contains these OIDs: .1.3.6.1.2.1.2.2.1.6.1 (ifPhysAddress) .1.3.6.1.2.1.2.2.1.10.2 (ifInOctets) .1.3.6.1.2.1.2.2.1.16.2 (ifOutOctets) .1.3.6.1.4.1.30140.4.1.0 (wirelessStatus) .1.3.6.1.4.1.30140.4.2.0 (wirelessPLMN) .1.3.6.1.4.1.30140.4.3.0 (wirelessCell) .1.3.6.1.4.1.30140.4.4.0 (wirelessChannel) .1.3.6.1.4.1.30140.4.5.0 (wirelessLevel) .1.3.6.1.4.1.30140.4.6.0 (wirelessChannelN1) .1.3.6.1.4.1.30140.4.7.0 (wirelessLevelN1) .1.3.6.1.4.1.30140.4.8.0 (wirelessChannelN2) .1.3.6.1.4.1.30140.4.9.0 (wirelessLevelN2) .1.3.6.1.4.1.30140.4.10.0 (wirelessChannelN3) .1.3.6.1.4.1.30140.4.11.0 (wirelessLevelN3) .1.3.6.1.4.1.30140.4.12.0 (wirelessChannelN4) .1.3.6.1.4.1.30140.4.13.0 (wirelessLevelN4) .1.3.6.1.4.1.30140.4.14.0 (wirelessChannelN5) .1.3.6.1.4.1.30140.4.15.0 (wirelessLevelN5) .1.3.6.1.4.1.30140.4.16.0 (wirelessUptime) .1.3.6.1.4.1.30140.4.17.0 CU IDOL SELF LEARNING MATERIAL (SLM)

SNMP (Simple Network Management Protocol) 149 (wirelessConnect) .1.3.6.1.4.1.30140.4.18.0 (wirelessDisconnect) .1.3.6.1.4.1.30140.4.19.0 .1.3.6.1.4.1.30140.4.22.0 (wirelessCard) .1.3.6.1.4.1.30140.4.21.0 (wirelessLatency) (wirelessReportPeriod) .1.3.6.1.4.1.30140.5.1.10.0 (wirelessCells) Every 24 hours these OIDs are also transmited: .1.3.6.1.4.1.30140.6.3.0 (infoSN) .1.3.6.1.4.1.30140.6.4.0 (infoIMEI) .1.3.6.1.4.1.30140.6.5.0 (infoESN) .1.3.6.1.2.1.1.1.0 (sysDescr) .1.3.6.1.2.1.1.5.0 (sysName) .1.3.6.1.2.1.1.6.0 (sysLocation) 7.8 Problems with SNMP Some SNMP problems are caused by the content of the SNMP traps being sent. Because identifying these issues is a fairly quick process, it is a good idea to look for them before moving on to more time-intensive procedures. Be sure to check for these trap issues as you begin troubleshooting. 1. Incompatible Trap Versions: If your SNMP manager is configured to accept v1 traps and your device is sending v2 traps, you will encounter problems. Similarly, some managers that are configured to receive v2 traps will not correctly parse v1 traps. Configure your RTU to send the version of traps that your manager is set up to accept, or configure your manager to receive the type of traps that your remote equipment is sending. Generally speaking, most v2 managers can be configured to receive v1 traps. 2. Non-standard Trap Formats: SNMP managers can also run into trouble if a device is sending non-standard traps. Although SNMP is a standard protocol, some people have modified the formats of their traps to suit special needs. They might have, for example, added an extra field to their traps to transmit a particular piece of additional data. If this change was not properly documented, it can cause trouble later. Because this is not a very common SNMP issue, it tends to be one of the more difficult to identify. If you find yourself with a stubborn SNMP problem, don’t forget to check for non-standard trap formats/content. 3. Altered Community Names: In most SNMP implementations, the community name used by the devices and the manager is “public”. Some IT departments, however, have set up unique community names on their networks. This can cause trouble with your SNMP traps because some SNMP managers will use the community name as a unique identifier. If your manager is expecting “public”, but CU IDOL SELF LEARNING MATERIAL (SLM)

150 Advanced Computer Networks finds a customized community name instead (or vice versa), it may simply discard the trap. Another potential problem is switches that utilize variable community names. Devices connected to Shelf 1 might be given the community name “public-1”, those on Shelf 2 given “public-2”, etc. Unless you have a proprietary master that is expecting traps with variable community names, it may not handle them properly. Check for any altered community names and make any necessary adjustments. Remember that community names must match exactly and are case-sensitive. 7.9 Summary A numeral system (or system of numeration) is a writing system for expressing numbers, i.e., a mathematical notation for representing numbers of a given set, using digits or other symbols in a consistent manner. The number the numeral represents is called its value. The same sequence of symbols may represent different numbers in different numeral systems. For example, “11” represents the number eleven in the decimal numeral system (used in common life), the number three in the binary numeral system (used in computers), and the number two in the unary numeral system (e.g., used in tallying scores). 7.10 Keywords/Abbreviations  SNMP: Simple Network Management Protocol (SNMP) is an Internet Standard protocol for collecting and organizing information about managed devices on IP networks and for modifying that information to change device behavior. Devices that typically support SNMP include cable modems, routers, switches, servers, workstations, printers and more. SNMP Management Components :  SMI: The SMI (Structure of management information) is a component used in network management. Its main function is to define the type of data that can be stored in an object and to show how to encode the data for the transmission over a network.  MIB – The MIB (Management Information Base) is a second component for the network management. – Each agent has its own MIB, which is a collection of all the objects that the manager can manage. MIB is categorized into eight groups: system, interface, CU IDOL SELF LEARNING MATERIAL (SLM)

SNMP (Simple Network Management Protocol) 151 address translation, ip, icmp, tcp, udp and egp. These groups are under the mib object.  Object Identifiers: An SNMP object identifier uniquely names an object and identifies its location within a Management Information Base (MIB) tree structure. Object identifiers are application-independent Abstract Syntax Notation One (ASN.1) data types that consist of a sequence of non-negative integers, or sub-identifiers. Object identifiers must have a minimum of two sub-identifiers and they must not exceed 128 sub- identifiers. Abbreviations  MIB: Management Information Base  ASN.1: Abstract Syntax Notation One  SMI: Structure of Management Information  SNMP: Simple Network Management Protocol  IETF: Internet Engineering Task Force 7.11 Learning Activity 1. Explain different problems in SNMP. ----------------------------------------------------------------------------------------------------------- ----------------------------------------------------------------------------------------------------------- 2. Explain SNMP protocol with its versions and components. ----------------------------------------------------------------------------------------------------------- ----------------------------------------------------------------------------------------------------------- 3. Explain different SNMP messages. ----------------------------------------------------------------------------------------------------------- ----------------------------------------------------------------------------------------------------------- 7.12 Unit End Questions (MCQs and Descriptive) A. Descriptive Type Questions 1. Write a note on IP Management Protocol. 2. Explain different Network Management Protocols. CU IDOL SELF LEARNING MATERIAL (SLM)

152 Advanced Computer Networks 3. Explain SNMP in detail with its architecture. 4. Explain different SNMP Agents and Managers with neat diagram. 5. Write a note on Managed LAN of SNMP Management Model. 6. Explain different SNMP Messages with neat diagram. 7. Write a note on SNMP organization. 8. Explain SNMP organization model with neat diagram. 9. Explain different Object Identifiers of SNMP. 10. Explain different issues and problems with SNMP. B. Multiple Choice/Objective Type Questions 1. __________ uses community strings for authentication and use UDP only. (a) SNMPv1 (b) SNMPv3 (c) SNMPv2 (d) None of the above 2. Which version of SNMP uses community strings for authentication? (a) SNMPv1 (b) SNMPv3 (c) SNMPv2 (d) None of the above 3. Which SNMP version uses Hash based MAC with MD5 or SHA for authentication and DES-56 for privacy. (a) SNMPv1 (b) SNMPv3 (c) SNMPv2 (d) None of the above 4. __________ are components of Network Management Protocol. (a) MIB (b) SMI (c) Both (a) and (b) (d) None of the above 5. __________ are SNMP Messages. (a) GetRequest (b) SetRequest (c) Trap (d) All of the above Answers 1. (a), 2. (c), 3. (b), 4. (c), 5. (d) CU IDOL SELF LEARNING MATERIAL (SLM)

SNMP (Simple Network Management Protocol) 153 7.13 References 1. IP Address Management: Principles and Practice by Trimothy Rooney. 2. https://www.ciscopress.com/articles/article.asp?p=1073230&seqNum=4 3. Data Communications and Networking Book by Behrouz A. Forouzan. CU IDOL SELF LEARNING MATERIAL (SLM)

UNIT 8 WIRELESS SENSOR NETWORKS Structure: 8.0 Learning Objectives 8.1 Introduction 8.2 WSN Functioning 8.3 Operation System Support in Sensor Devices 8.4 WSN Characteristics 8.5 Sensor Network Operations 8.6 Sensor Architecture 8.7 Summary 8.8 Keywords/Abbreviations 8.9 Learning Activity 8.10 Unit End Questions (MCQs and Descriptive) 8.11 References 8.0 Learning Objectives After studying this unit, you will be able to:  Describe the functioning of wireless sensor networks  Illustrate sensor architecture  List WSN characteristics CU IDOL SELF LEARNING MATERIAL (SLM)

Wireless Sensor Networks 155 8.1 Introduction Wireless sensor networks (WSN) are composed of a finite set of sensor devices geographically distributed in a given indoor or outdoor environment (usually predefined). A WSN aims to gather environmental data and the node devices placement may be known or unknown a priori. Network nodes can have actual or logical communication with all devices. Such a communication defines a topology according to the application. For instance, there can be a WSN with both types of topologies being the same (mesh, star, etc.). However, this may not be the case for all applications. The logical topology is mainly defined based on the nodes logical role (tasks, etc.). It can be either ad hoc or strategy based (self-organization, clustering, pheromone tracking, and so on). The strategy is defined based on the network available resources. 8.2 WSN Functioning Wireless Sensor Networks (WSNs) can be defined as a self-configured and infrastructure- less wireless networks to monitor physical or environmental conditions, such as temperature, sound, vibration, pressure, motion or pollutants and to cooperatively pass their data through the network to a main location or sink where the data can be observed and analyzed. A sink or base station acts like an interface between users and the network. One can retrieve required information from the network by injecting queries and gathering results from the sink. Typically, a wireless sensor network contains hundreds of thousands of sensor nodes. The sensor nodes can communicate among themselves using radio signals. A wireless sensor node is equipped with sensing and computing devices, radio transceivers and power components. The individual nodes in a wireless sensor network (WSN) are inherently resource constrained. They have limited processing speed, storage capacity and communication bandwidth. After the sensor nodes are deployed, they are responsible for self-organizing an appropriate network infrastructure, often with multi-hop communication with them. Then the on-board sensors start collecting information of interest. Wireless sensor devices also respond to queries sent from a “control site” to perform specific instructions or provide sensing samples. The working mode of the sensor nodes may be either continuous or event-driven. Global Positioning System (GPS) and local positioning algorithms can be used to obtain location and positioning information. Wireless sensor devices can be equipped with actuators to “act” upon certain conditions. CU IDOL SELF LEARNING MATERIAL (SLM)

156 Advanced Computer Networks 8.3 Operation System Support in Sensor Devices In a sensor network, application-specific requirements drive the entire hardware design, from processing capabilities to radio bandwidth and sensor modules, thus requiring the hardware to be modular. These requirements have led to a huge variety of hardware components, making wireless sensor networks hardware not only modular, but also heterogeneous. In this, a sensor application developed for a given platform will seldom be portable to a different one, unless the run-time support systems on those platforms deliver mechanisms that abstract and encapsulate the sensor platform in an adequate manner. The limited resources typically found in sensor networks hardware require any run-time support for these systems to be efficient and not to use excessive resources. The need for connectivity, hardware abstraction and management of limited resources makes operating system support imperative for sensor network applications, considering current research, technology and applications. List a series of operating system requirements for wireless sensor networks. Such a system should: Provide basic operating system functionality: In order not to restrict the functionality and portability of sensor networks applications, an operating system for such devices should provide traditional operating system services such as: hardware abstraction, process management (usually following the mono-task, multithread prism, etc.), timing services and memory management. Provide efficient power management mechanisms: Efficient power management in the sensor nodes is a determining factor for the network’s lifetime. A run-time support system for sensor networks applications should provide power management mechanisms to the applications as well as use as little power as possible to provide its services. Provide field reprogramming mechanisms: Given that the sensor nodes may be located in inhospitable regions, and that application requirements and parameters may change with time, field reprogramming through the communication network is an important service in this type of networks. An operating system for sensor networks should ideally provide total or partial field reprogramming mechanisms for deployed applications. CU IDOL SELF LEARNING MATERIAL (SLM)

Wireless Sensor Networks 157 8.4 WSN Characteristics The main characteristics of a WSN include:  Power consumption constraints for nodes using batteries or energy harvesting  Ability to cope with node failures (resilience)  Some mobility of nodes (for highly mobile nodes, see MWSNs)  Heterogeneity of nodes  Homogeneity of nodes  Scalability to large scale of deployment  Ability to withstand harsh environmental conditions  Ease of use  Cross-layer optimization Distributed techniques are used when the application has to preserve some properties, namely, energy saving, the number of connections, memory, and efficiency, among others, or when the information processing is inefficient in a centralized way. The distributed techniques have some special characteristics: 1. Independence: It is present when a user is the only one who chooses where the data will be stored and when the data can be modified or deleted. The information saved does not have any information dependency with other devices. The important decisions are based on the device data. This feature offers most of the time information support by an own server or one host provided by a supporting company. 2. Integrity with respect to other services: Being present in this type of distributed techniques does not mean to give up to the integrity offered by the centralized models. 3. Scalability: According to the application, scalability allows adding more nodes to the network without changes on the network performance, which means that this does not affect the rest of the network. 4. Reduced information management: Networks are based on the local information knowledge, namely, neighbors. CU IDOL SELF LEARNING MATERIAL (SLM)

158 Advanced Computer Networks 8.5 Sensor Network Operations WSNs are spatially distributed autonomous sensors to monitor physical or environmental conditions, such as temperature, sound, pressure, etc. and to cooperatively pass their data through the network to a main location. The propagation technique between the hops of the network can be routing or flooding. Centralized networks take directions from a unique device. This central node is responsible for providing network operation services such as node localization, event detection and traffic routing. A suitable logical topology for this approach is a star. The centralized networks can be classified according to how the information is processed. These groups include the following: 1. Single Sink: The objective of the formation strategy is to reduce the forwarding time and route the information towards a unique sink. The main drawback of single sink systems is the lack of redundancy. 2. Multisink: Multiple sinks are employed for scenarios in which the previous tasks are distributed to several nodes. This is done for a number of reasons such as network density, coverage area, redundancy, distribution of traffic flows, network life span, and possible energy consumption. 3. Multiple Task Devices: Recent research works suggest the use of auxiliary network devices. These devices can be responsible for doing a specific activity inside the network such as knowing the complete environment to define a route, control of nodes movements, and definition of a target node, to improve the overall WSN application performance. 8.6 Sensor Architecture A sensor node is made up of four basic components such as sensing unit, processing unit, transceiver unit and a power unit. It also has application-dependent additional components such as a location finding system, a power generator and a mobilizer. Sensing units are usually composed of two subunits: sensors and analogue to digital converters (ADCs) (Akyildiz et al., 2002). The analogue signals produced by the sensors are converted to digital signals by the ADC, and then fed into the processing unit. The processing unit is generally associated with a small storage unit and it can manage the procedures that make the sensor node collaborate with the CU IDOL SELF LEARNING MATERIAL (SLM)

Wireless Sensor Networks 159 other nodes to carry out the assigned sensing tasks. A transceiver unit connects the node to the network. One of the most important components of a sensor node is the power unit. Power units can be supported by a power scavenging unit such as solar cells. The other subunits of the node are application-dependent. Modular design approach provides a flexible and versatile platform to address the needs of a wide variety of applications. For example, depending on the sensors to be deployed, the signal conditioning block can be reprogrammed or replaced. This allows for a wide variety of different sensors to be used with the wireless sensing node. Similarly, the radio link may be swapped out as required for a given applications’ wireless range requirement and the need for bi-directional communications. Internet BS Sensor node Target User Position Finding System Mobilizer Sensing Unit Processing Unit Transmission Unit Sensor ADC Processor Transceiver Storage Power Unit Power Generator Fig. 8.1: The Components of a Sensor Node CU IDOL SELF LEARNING MATERIAL (SLM)

160 Advanced Computer Networks Sensor Inputs Lithium thionyl Radio frequency chloride battery (RF) transceiver Sensor signal conditioning 8 bit, low power, Flash EEPROM for microcontroller sensor logging Multiplexer, PG instrumentation A/D converter (12 bit resolution) amplifier Fig. 8.2: Functional Block Diagram of a Sensor Node Using flash memory, the remote nodes acquire data on command from a base station, or by an event sensed by one or more inputs to the node. Moreover, the embedded firmware can be upgraded through the wireless network in the field. The microprocessor has a number of functions including:  Managing data collection from the sensors  Performing power management functions  Interfacing the sensor data to the physical radio layer  Managing the radio network protocol A key aspect of any wireless sensing node is to minimize the power consumed by the system. Usually, the radio subsystem requires the largest amount of power. Therefore, data is sent over the radio network only when it is required. An algorithm is to be loaded into the node to determine when to send data based on the sensed event. Furthermore, it is important to minimize the power consumed by the sensor itself. Therefore, the hardware should be designed to allow the microprocessor to judiciously control power to the radio, sensor and sensor signal conditioner. CU IDOL SELF LEARNING MATERIAL (SLM)

Wireless Sensor Networks 161 8.7 Summary WSN Functioning Wireless Sensor Networks (WSNs) can be defined as a self-configured and infrastructure- less wireless networks to monitor physical or environmental conditions, such as temperature, sound, vibration, pressure, motion or pollutants and to cooperatively pass their data through the network to a main location or sink where the data can be observed and analyzed. A sink or base station acts like an interface between users and the network. One can retrieve required information from the network by injecting queries and gathering results from the sink. Typically, a wireless sensor network contains hundreds of thousands of sensor nodes. WSN Characteristics The main characteristics of a WSN include:  Power consumption constraints for nodes using batteries or energy harvesting  Ability to cope with node failures (resilience)  Some mobility of nodes (for highly mobile nodes, see MWSNs)  Heterogeneity of nodes  Homogeneity of nodes  Scalability to large scale of deployment  Ability to withstand harsh environmental conditions  Ease of use  Cross-layer optimization  Independence  Integrity with respect to other services  Scalability Sensor Network Operations 1. Single Sink: The objective of the formation strategy is to reduce the forwarding time and route the information towards a unique sink. 2. Multisink: Multiple sinks are employed for scenarios in which the previous tasks are distributed to several nodes. CU IDOL SELF LEARNING MATERIAL (SLM)

162 Advanced Computer Networks 3. Multiple Task Devices: Recent research works suggest the use of auxiliary network devices. Sensor Architecture A sensor node is made up of four basic components such as sensing unit, processing unit, transceiver unit and a power unit. It also has application-dependent additional components such as a location finding system, a power generator and a mobilizer. Modular design approach provides a flexible and versatile platform to address the needs of a wide variety of applications. For example, depending on the sensors to be deployed, the signal conditioning block can be reprogrammed or replaced. 8.8 Keywords/Abbreviations  WSN Functioning: Wireless Sensor Networks (WSNs) can be defined as a self- configured and infrastructure-less wireless networks to monitor physical or environmental conditions, such as temperature, sound, vibration, pressure, motion or pollutants and to cooperatively pass their data through the network to a main location or sink where the data can be observed and analyzed.  Sensor Network Operations: Single Sink, Multisink and Multiple Task Devices. Abbreviations  WSN: Wireless Sensor Networks  GPS: Global Positioning System  ADC: Analogue to Digital Converters 8.9 Learning Activity 1. Explain WSN functioning with respect to self-configuration and infrastructure. ----------------------------------------------------------------------------------------------------------- ----------------------------------------------------------------------------------------------------------- 2. Explain difference between Single Sink and Multisink. ----------------------------------------------------------------------------------------------------------- ----------------------------------------------------------------------------------------------------------- CU IDOL SELF LEARNING MATERIAL (SLM)

Wireless Sensor Networks 163 3. Explain different components of sensor node. ----------------------------------------------------------------------------------------------------------- ----------------------------------------------------------------------------------------------------------- 8.10 Unit End Questions (MCQs and Descriptive) A. Descriptive Type Questions 1. Write a note on WSN functioning. 2. Explain Operation System Support in sensor devices. 3. What are different WSN characteristics? 4. Explain different sensor network operations. 5. Explain sensor architecture with neat diagram. B. Multiple Choice/Objective Type Questions 1. Which is main component of sensor node? (a) Session identifier (b) Transceiver unit (c) Processing and power unit (d) All of the above 2. Which logical topology is used for sensor network operations? (a) Bus (b) Ring (c) Star (d) None of the above 3. Which are WSN characteristics? (a) Independence (b) Scalability (c) Integrity with respect to other services (d) All of the above 4. The sensor nodes can communicate among themselves using __________ signals. (a) Analog (b) Digital (c) Radio (d) None of the above CU IDOL SELF LEARNING MATERIAL (SLM)

164 Advanced Computer Networks 5. Which system along with local positioning algorithms can be used to obtain location and positioning information? (a) Wireless (b) GPS (c) All of the above (d) None of the above Answers 1. (d), 2. (c), 3. (d), 4. (c), 5. (b) 8.11 References 1. https://www.hindawi.com/journals/js/2016/2081902/ 2. https://www.intechopen.com/books/wireless-sensor-networks-technology-and-protocols/ overview-of-wireless-sensor-network 3. Data Communications and Networking Book by Behrouz A. Forouzan. CU IDOL SELF LEARNING MATERIAL (SLM)

UNIT 9 WIRELESS MASH NETWORKS Structure: 9.0 Learning Objectives 9.1 Introduction 9.2 WMN Design 9.3 Issues in WMNs 9.4 Summary 9.5 Keywords/Abbreviations 9.6 Learning Activity 9.7 Unit End Questions (MCQs and Descriptive) 9.8 References 9.0 Learning Objectives After studying this unit, you will be able to:  Describe WMN design  Elaborate issues in WNMs 9.1 Introduction Wireless mesh network is a network which comprises various wireless nodes with access points. Each node in the network acts as a forwarding node to transfer the data. Since the network is decentralized, forwarding of data is possible only to the neighboring node. This results in the network structure simple and easy. WMN makes the people connected with the Internet who CU IDOL SELF LEARNING MATERIAL (SLM)

166 Advanced Computer Networks work at remote areas and operating business. This chapter throws light on WMN architecture, layer functionalities, and various other networking standards and applications. 9.2 WMN Design Wireless Mesh Network (WMN) is defined as the types of the new encouraging type of technology which depends upon the use of already existing software and hardware components. In order to understand the project, the research of the network of flying Unmanned Aerial Vehicles was done. The use of various types of the reactive and the proactive routing characteristics for the purpose of transforming the information is also studied for the purpose of carrying the project linearly. For the purpose of simulation, the use of various standards along with the standalone simulator were studied for varying the number of the nodes, nodes mobility and density. Wireless mesh network is an upcoming technology that has the potential to deliver Internet broadband access, wireless local area network coverage, and network connectivity for network operators and customers at low costs. It is a communication network that have increasingly attracted Internet Service Providers (ISPs) recently because of its rapid growing and developing of wireless technologies. WMN is a promising technology in providing high bandwidth network coverage. WMNs will greatly help the users to be always online anywhere anytime by connecting to wireless mesh routers. WMN Architecture Wireless mesh architecture design is a first step towards providing high bandwidth Internet access over a specific coverage area. WMNs consist of Mesh Clients (MCs) and Wireless Mesh Routers (WMRs), where mesh routers have minimal mobility and form the Backbone of WMNs (BWMNs). WMN is made up of wireless communication nodes, each of which can communicate with other nodes. Mesh architecture breaks the long distance into a series of shorter hops to boost the signal by intermediate nodes. Intermediate nodes not only sustain signal strength, but also forward packages on behalf of other nodes based on their knowledge of the network. Such architecture allows continuous connections and reconfiguration around broken or blocked paths by making forwarding decisions from node to node until the destination is reached. Besides, it provides high-bandwidth Internet access and offers low cost and flexible deployment. CU IDOL SELF LEARNING MATERIAL (SLM)

Wireless Mash Networks 167 The infrastructure that supports a WMN is a wireless mesh router network or Backbone Wireless Mesh Network (BWMN) . BWMN provides Internet connectivity to MCs in a multi-hop fashion. MCs can access the Internet via BWMN formed by Wireless Mesh Routers (WMRs). BWMN consists of some special WMRs called as Internet Gateways (IGWs). IGWs act as communication bridges between the Internet and BWMN, and provide Internet accessibility. A typical WMN is as shown in the figure. Wireless mesh Internet Mesh router backbone Mesh router with gateway Mesh router with gateway Mesh router WiFi network Sensor network WiMAX network Mobile ad hoc network Fig. 9.1: Wireless Mesh Network Components of WMNs There are three types of node in a WMN: WMN client, WMN router and WMN gateway WMN clients are the end-user devices such as laptops, PDAs, smartphones, etc. that can access the network for using applications like e-mail, VoIP, game, location detection, etc. These devices are assumed to be mobile; they have limited power; they may have routing capability; and they may or may not be always connected to the network. CU IDOL SELF LEARNING MATERIAL (SLM)

168 Advanced Computer Networks WMN routers are in the network to route the network traffic. They cannot terminate nor originate the traffic. The routers have limitation in mobility and they have reliable characteristics. Transmission power consumption in mesh routers is low for multi-hop communications strategy. The Medium Access Control (MAC) protocol in a mesh router supports multiple channels and multiple interfaces to enable scalability in a multi-hop mesh environment. WMN gateways are routers with direct access to the wired infrastructure/Internet. Since the gateways in WMNs have multiple interfaces to connect to both wired and wireless networks, they are expensive. Therefore, there are a few number of WMN gateways in the network. Moreover, their placement has a significant impact on the performance of the network. Applications of WMNs There are some applications which cannot be directed and fully supported by other wireless technologies rather than WMNs. 1. Broadband Wireless Access: Currently, Broadband access has an important role in information economy. It provides services for real-time applications such as video telephony, online gaming, video on demand and telecommunications. Each new application has a significant impact on quality of life. For example, telecommuting can reduce daily traveling of individuals. It leads to increased productivity for the time saving. It also reduces traffic on the streets. Thus, it has a positive impact on the environment. Satellite access has two drawbacks: expensive technology and high latency due to the distance between the end client and the satellite. In the case of cellular networks, the towers are expensive to install and operate. Lack of service providers and the higher cost of the service itself makes lower usage of broadband access. In order to wider adoption of Internet access, WMNs offer an easy-to-deploy and cost- effective alternative in areas where cable TV or DSL lines are not available. 2. Industrial Applications: Building Automation: In a building, there are many devices which need to be monitored and controlled like electrical devices including power, light, air conditioner, elevator, etc. Today, the wired networks are taking care of such environment. This is very expensive due to the complexity in deployment and maintenance of a wired network. Currently, Wi-Fi networks are another option to reduce the cost of such CU IDOL SELF LEARNING MATERIAL (SLM)

Wireless Mash Networks 169 networks. But, this solution has not achieved satisfactory performance yet for expensive wiring of Ethernet which is needed for Wi-Fi Access Points (APs). Replacing APs by mesh routers will solve the problem. The deployment process will be much simpler, and also the deployment cost will be significantly reduced. 3. Healthcare: In a hospital or medical center, monitoring and updating patient information like medical history, test results, insurance information, etc. need to be processed and transmitted from room to room. The ability to connect to the network is crucial to ensure data access in every operating room, office and lab. In many hospitals, data transmission is usually broadband due to large amount of data, e.g., high resolution medical images and periodical monitoring information. WMN provides unlimited network access to any fixed medical devices. It does not need to use existed Ethernet connections, so that it will eliminate dead spots, and also cause low system cost and simplicity which cannot be found in traditional wired networks. 4. Transportation Systems: Internet access is limited to stations and stops using IEEE 802.11 and IEEE 802.16. WMN technology can help to extend access into buses, plains, ferries and trains, etc. Thus, passengers on-board can access to the net while traveling from one place to another. Other services such as remote monitoring in-vehicle, driver communications and security cameras can be supported too. 5. Hospitality: In hotels and resorts, one of their services is high-speed Internet connectivity which is free. WMNs are easy to set up, lower in cost, and without having to change the existing structures or disrupt business for both indoor and outdoor. 6. Warehouses: One way to keep track of stock in warehouses is using handheld scanners. It needs connectivity throughout the area. WMNs can ensure connectivity in modern warehouses and shipping logistics with little cost and effort. 7. Temporary Venues: Construction sites can enjoy the easy setup and removal of wireless mesh networks. Architects and engineers can stay connected by using camera to communicate and talk to each other on spot. It provides them to see the real picture of the project progresses. Other temporary venues such as political rallies, street fairs and outdoor concerts can set up and remove wireless mesh networks in minutes. 9.3 Issues in WNMs Different Security Issues in WNMs are as follows: CU IDOL SELF LEARNING MATERIAL (SLM)

170 Advanced Computer Networks 1. Secure Medium Access Control: The IEEE 802.11 medium access control (MAC) protocol has been adopted as the de facto MAC scheme of WMNs in many research projects and commercial products The cryptographic approach for securing the 802.11 MAC protocol had evolved from Wired Equivalent Privacy (WEP) protocol to IEEE 802.11i standard. 2. Physical Attacks: Internet access speeds up when more users contribute to the network, but it also opens up the network to multiple points of access. As all computers in a wireless mesh function as routers, each computer represents a possible point of attack. Computer nodes also can be compromised by the loss or theft of a laptop or desktop computer. In this case, the attacker stealing the computer can use the access provided by the stolen computer to enter the network, or simply disrupt the entire system by removing crucial routing nodes. 3. Denial of Service: Even without physical access to the network, hackers can create “zombie” computers using virus infections. Once infected, each computer does the bidding of the attacker without direct monitoring. Meanwhile, the hacker launches a concentrated denial-of-service attack, which floods a particular computer or system with overwhelming bits of information to effectively shut down that system’s ability to communicate with other networks. If a computer in a mesh network becomes infected, it can attack other computers inside its own network, and infect them as well, causing a cascading effect. 4. Passive Monitoring: A zombie computer does not need to attack the system to cause damage. Hidden and compromised computers can passively monitor Internet traffic moving through the network, giving the attacker the ability to intercept bank information, login credentials for any website accessed and routing information for the network itself. At this point, the attacker can chose to leave the network without anyone knowing, while possessing enough data to steal bank funds, commit identity fraud or re-enter the network at will. 5. Gray, Black and Worm Holes: If a computer becomes infected or malicious computer enters a mesh network, it can pretend to be a trusted member of that network and then modify sent data and disrupt how the network passes information. In a black hole attack, information passing through the infected computer will not continue through the network, blocking the flow of data. In gray hole attacks, some data may be blocked, while other data is allowed, making it seem like the computer is still a working part of the network. Worm hole attacks are harder to detect. They tunnel into a network computer from the CU IDOL SELF LEARNING MATERIAL (SLM)

Wireless Mash Networks 171 outside and pretend to be other nodes in the network, essentially becoming invisible nodes. They can then monitor network traffic as it passes from one node to the next. 9.4 Summary WMN Design Wireless Mesh Network (WMN) is defined as the types of the new encouraging type of technology which depends upon the use of already existing software and the hardware components. In order to understand the project, the research of the network of flying Unmanned Aerial Vehicles was done. WMN Architecture Wireless mesh architecture design is a first step towards providing high bandwidth Internet access over a specific coverage area. WMNs consist of Mesh Clients (MCs) and Wireless Mesh Routers (WMRs), where mesh routers have minimal mobility and form the Backbone of WMNs (BWMNs). WMN is made up of wireless communication nodes, each of which can communicate with other nodes. Mesh architecture breaks the long distance into a series of shorter hops to boost the signal by intermediate nodes. Intermediate nodes not only sustain signal strength, but also forward packages on behalf of other nodes based on their knowledge of the network. Applications of WMNs 1. Broadband Wireless Access 2. Industrial Applications 3. Healthcare 4. Transportation Systems 5. Hospitality 6. Warehouses 7. Temporary Venues Issues in WNMs  Physical Attacks  Denial of Service CU IDOL SELF LEARNING MATERIAL (SLM)

172 Advanced Computer Networks  Passive Monitoring  Gray, Black and Worm Holes 9.5 Keywords/Abbreviations  WMN: Wireless mesh network is a network which comprises various wireless nodes with access points. Each node in the network acts as a forwarding node to transfer the data. Since the network is decentralized, forwarding of data is possible only to the neighboring node.  Components of WMNs: WMN clients are the end-user devices such as laptops, PDAs, smartphones, etc. that can access the network for using applications like e-mail, VoIP, game, location detection, etc. These devices are assumed to be mobile; they have limited power; they may have routing capability; and they may or may not be always connected to the network. WMN routers are in the network to route the network traffic. They cannot terminate nor originate the traffic. The routers have limitation in mobility and they have reliable characteristics. Transmission power consumption in mesh routers is low for multi-hop communications strategy.  Physical Attacks: Internet access speeds up when more users contribute to the network, but it also opens up the network to multiple points of access. As all computers in a wireless mesh function as routers, each computer represents a possible point of attack.  Denial of Service: Even without physical access to the network, hackers can create “zombie” computers using virus infections. Once infected, each computer does the bidding of the attacker without direct monitoring. Meanwhile, the hacker launches a concentrated denial-of-service attack, which floods a particular computer or system with overwhelming bits of information.  Passive Monitoring: A zombie computer does not need to attack the system to cause damage. Hidden and compromised computers can passively monitor Internet traffic moving through the network, giving the attacker the ability to intercept bank information, login credentials for any website accessed and routing information for the network itself.  Gray, Black and Worm Holes: If a computer becomes infected or malicious computer enters a mesh network, it can pretend to be a trusted member of that network, then modify sent data and disrupt how the network passes information. In a black hole attack, CU IDOL SELF LEARNING MATERIAL (SLM)

Wireless Mash Networks 173 information passing through the infected computer will not continue through the network, blocking the flow of data. Abbreviations  WMN: Wireless Mesh Network  ISPs: Internet Service Providers  MCs: Mesh Clients  WMRs: Wireless Mesh Routers  IGWs: Internet Gateways  BWMNs: Backbone of WMNs  MAC: Medium Access Control  PDA: Personal Digital Assistant  VoIP: Voice over Internet Protocol 9.6 Learning Activity 1. Explain WMN architecture with its components. ----------------------------------------------------------------------------------------------------------- ----------------------------------------------------------------------------------------------------------- 2. State different applications of WMN. ----------------------------------------------------------------------------------------------------------- ----------------------------------------------------------------------------------------------------------- 3. State the issues of WMN. ----------------------------------------------------------------------------------------------------------- ----------------------------------------------------------------------------------------------------------- 9.7 Unit End Questions (MCQs and Descriptive) A. Descriptive Type Questions 1. Explain WNM design with its architecture. 2. Explain WMN client, WMN router and WMN gateway. CU IDOL SELF LEARNING MATERIAL (SLM)

174 Advanced Computer Networks 3. Explain Industrial and Healthcare WNM applications. 4. Explain different security issues in WNM. B. Multiple Choice/Objective Type Questions 1. What is range of the IEEE 802.11a standard? (a) 2.4 Gbps (b) 5 Gbps (c) 2.4 GHz (d) 5 GHz 2. __________ act as communication bridges between the Internet and BWMN. (a) IGW (b) WMR (c) Both (a) and (b) (d) None of the above 3. __________ are routers with direct access to the wired infrastructure/Internet. (a) WMN clients (b) WMN gateways (c) WMN routers (d) All of the above 4. Which protocol in a mesh router supports multiple channels and multiple interfaces to enable scalability in a multi-hop mesh environment? (a) IP (b) TCP (c) MAC (d) None of the above 5. Which type of Attack can attack even without physical access to the network, hackers can create “zombie” computers using virus infections? (a) Passive Attack (b) Denial of Service (c) Active Attack (d) None of the above Answers 1. (d), 2. (a), 3. (b), 4. (c), 5. (b) 9.8 References 1. https://www.intechopen.com/online-first/an-overview-of-wireless-mesh-networks 2. https://www.cse.unsw.edu.au/~mahbub/PDF_Publications/mesh_2008.pdf 3. https://www.sciencedirect.com/topics/computer-science/wireless-mesh-network 4. https://www.researchgate.net/publication/311252676_Architecture_issues_and_ challenges_of_wireless_mesh_network CU IDOL SELF LEARNING MATERIAL (SLM)

UNIT 10 COMPUTATIONAL GRIDS Structure: 10.0 Learning Objectives 10.1 Introduction 10.2 Grid Features 10.2.1 Definition of Computational Grids 10.2.2 The Impact of Grids 10.3 Issues in Grid Construction Technology 10.4 Summary 10.5 Keywords/Abbreviations 10.6 Learning Activity 10.7 Unit End Questions (MCQs and Descriptive) 10.8 References 10.0 Learning Objectives After studying this unit, you will be able to:  List grid features  Describe issues in grid construction technology 10.1 Introduction Grid computing is the federation of computer resources from multiple administrative domains to reach a common goal. “Computational grid is a hardware and software infrastructure CU IDOL SELF LEARNING MATERIAL (SLM)

176 Advanced Computer Networks that provides independent, pervasive and inexpensive access to high-end computational capabilities. The performance characteristics that are of interest will vary widely from application to application, but may include network bandwidth, latency, jitter, computer power, software services, security and reliability. 10.2 Grid Features 10.2.1 Definition of Computational Grids A computational grid is a hardware and software infrastructure that provides dependable, consistent, pervasive and inexpensive access to high-end computational capabilities. An infrastructure of computational grid is with large-scale pooling of resources, whether compute cycles, data, sensors or people. Such pooling requires significant hardware infrastructure to achieve the necessary interconnections and software infrastructure to monitor and control the resulting ensemble. An infrastructure must offer inexpensive (relative to income) access if it is to be broadly accepted and used. A computational grid must achieve similarly attractive economics. 10.2.2 The Impact of Grids The history of network computing shows that orders-of-magnitude improvements in underlying technology invariably enable revolutionary, often unanticipated, applications of that technology, which in turn motivate further technological improvements. As a result, our view of network computing has undergone repeated transformations over the past 40 years. There is considerable evidence that another such revolution is imminent. The capabilities of both computers and networks continue to increase dramatically. Ten years of research on meta computing has created a solid base of experience in new applications that couple high-speed networking and computing. The time seems ripe for a transition from the heroic days of meta computing to more integrated computational grids with dependable and pervasive computational capabilities and consistent interfaces. In such grids, today’s meta computing applications will be routine, and programmers will be able to explore a new generation of yet more interesting applications that leverage teraflop computers and petabyte storage systems interconnected by gigabit networks. CU IDOL SELF LEARNING MATERIAL (SLM)

Computational Grids 177 Today, citizen groups evaluating a proposed new urban development must study uninspiring blueprints or perspective drawings at city hall. A computational grid will allow them to call on powerful graphics computers and databases to transform the architect’s plans into realistic virtual reality depictions and to explore such design issues as energy consumption, lighting efficiency or sound quality. Meeting online to walk through and discuss the impact of the new development on their community, they can arrive at better urban design and hence improved quality of life.  Electric Power Grids The electric power grid is remarkable in terms of its construction and function, which together make it one of the technological marvels of the 20th century. Within large geographical regions (e.g., North America), it forms essentially a single entity that provides power to billions of devices, in a relatively low-cost and reliable fashion. The North American grid alone links more than ten thousand generators with billions of outlets via a complex web of physical connections and trading mechanisms. The components from which the grid is constructed are highly heterogeneous in terms of their physical characteristics, and are owned and operated by different organizations.  Main Grid Characteristics Ten definitions extracted from main grid literature sources have been examined to find out the essential characteristics that a grid is supposed to have in order to be considered as such. As a result, a total number of ten characteristics have been identified. These characteristics may be described as follows: – Large scale: A grid must be able to deal with a number of resources ranging from just a few to millions. This raises the very serious problem of avoiding potential performance degradation as the grid size increases. – Geographical distribution: Grid’s resources may be located at distant places. – Heterogeneity: A grid hosts both software and hardware resources that can be very varied ranging from data, files, software components or programs to sensors, scientific instruments, display devices, personal digital organizers, computers, supercomputers and networks. – Resource sharing: Resources in a grid belong to many different organizations that allow other organizations (i.e., users) to access them. Non-local resource scan thus be used by applications, promoting efficiency and reducing costs. CU IDOL SELF LEARNING MATERIAL (SLM)

178 Advanced Computer Networks – Multiple administrations: Each organization may establish different security and administrative policies under which their owned resources can be accessed and used. As a result, the already challenging network security problem is complicated even more with the need of taking into account all different policies. – Resource coordination: Resources in a grid must be coordinated in order to provide aggregated computing capabilities. – Transparent access: A grid should be seen as a single virtual computer. – Dependable access: A grid must assure the delivery of services under established Quality of Service (QoS) requirements. The need for dependable service is fundamental since users require assurances that they will receive predictable, sustained and often high levels of performance. – Consistent access: A grid must be built with standard services, protocols and interfaces thus hiding the heterogeneity of the resources while allowing its scalability. Without such standards, application development and pervasive use would not be possible. – Pervasive access: The grid must grant access to available resources by adapting to a dynamic environment in which resource failure is commonplace. 10.3 Issues in Grid Construction Technology Distributed Supercomputing Distributed supercomputing applications use grids to aggregate substantial computational resources in order to tackle problems that cannot be solved on a single system. Depending on the grid on which we are working these aggregated resources might comprise the majority of the supercomputers in the country or simply all of the workstations within a company. 1. The Nature of Applications: Early meta computing experiments provide useful clues regarding the nature of the applications that will motivate and drive early grid development. However, history also tells us that dramatic changes in capabilities such as those discussed here are likely to lead to radically new ways of using computers ways as yet unimagined. Research is required to explore the bounds of what is possible, both within those scientific and engineering domains in which meta computing has traditionally been applied, and in other areas such as business, art and entertainment. CU IDOL SELF LEARNING MATERIAL (SLM)

Computational Grids 179 2. Programming Models and Tools: Grid environments will require a rethinking of existing programming models and, most likely, new thinking about novel models more suitable for the specific characteristics of grid applications and environments. Within individual applications, new techniques are required for expressing advanced algorithms, for mapping those algorithms onto complex grid architectures, for translating user performance requirements into system resource requirements, and for adapting to changes in underlying system structure and state. Increased application and system complexity increases the importance of code reuse. So, techniques for the construction and composition of grid-enabled software components will be important. Another significant challenge is to provide tools that allow programmers to understand and explain program behavior and performance. 3. System Architecture: A need for broad deployment implies that these systems must be simple and place minimal demands on local sites. At the same time, the need to achieve a wide variety of complex, performance-sensitive applications implies that these systems must provide a range of potentially sophisticated services. Other complicating factors include the need for scalability and evolution to future systems and services. It seems likely that new approaches to software architecture will be needed to meet these requirements approaches that do not appear to be satisfied by existing Internet, distributed computing or parallel computing technologies. 4. Algorithms and Problem-solving Methods: Grid environments differ substantially from conventional uni processor and parallel computing systems in their performance, cost, reliability and security characteristics. These new characteristics will undoubtedly motivate the development of new classes of problem-solving methods and algorithms. 5. Resource Management: A defining feature of computational grids is that they involve sharing of networks, computers and other resources. This sharing introduces challenging resource management problems that are beyond the state of the art in a variety of areas. Many of the applications need to meet stringent end-to-end performance requirements across multiple computational resources connected by heterogeneous, shared networks. To meet these requirements, we must provide improved methods for specifying application-level requirements, for translating these requirements into computational resources and network-level quality-of-service parameters, and for arbitrating between constricting demands. 6. Security: Sharing also introduces challenging security problems. Traditional network security research has focused primarily on two-party client-server interactions with relatively low performance requirements. Grid applications frequently involve many CU IDOL SELF LEARNING MATERIAL (SLM)

180 Advanced Computer Networks more entities, impose stringent performance requirements, and involve more complex activities such as collective operations and the downloading of code. In larger grids, issues that arise in electronic markets become important. Users may require assurance and licensing mechanisms that can provide guarantees that services behave as advertised. 7. Instrumentation and Performance Analysis: The complexity of grid environments and the performance complexity of many grid applications make techniques for collecting, analyzing and explaining performance data of critical importance. Depending on the application and computing environment, poor performance as perceived by a user can be due to any one or a combination of many factors: an inappropriate algorithm, poor load balancing, inappropriate choice of communication protocol, contention for resources, or a faulty router. Significant advances in instrumentation, measurement and analysis are required if we are to be able to relate subtle performance problems in the complex environments of future grids to appropriate application and system characteristics. 8. End Systems: Grids also have implications for the end systems from which they are constructed. Today’s end systems are relatively small and are connected to networks by interfaces and with operating system mechanisms originally developed for reading and writing slow disks. Grids require that this model evolve in two dimensions. First, by increasing demand for high-performance networking, grid systems will motivate new approaches to operating system and network interface design in which networks are integrated with computers and operating systems at a more fundamental level than is the case today. Second by developing new applications for networked computers, grids will accelerate local integration and hence increase the size and complexity of the end systems from which they are constructed. 9. Network Protocols and Infrastructure: Grid applications can be expected to have significant implications for future network protocols and hardware technologies. Mainstream developments in networking, particularly in the Internet community, have focused on service for large numbers of relatively low bandwidth. Many of the future grid applications discussed in this book require both high bandwidths and performance assurances. Meeting these requirements will require major advances in the technologies used to transport, switch, route and manage network. CU IDOL SELF LEARNING MATERIAL (SLM)

Computational Grids 181 10.4 Summary Computational Grids A computational grid is a loose network of computers linked to perform grid computing. In a computational grid, a large computational task is divided up among individual machines, which run calculations in parallel and then return results to the original computer. These individual machines are nodes in a network, which may span multiple administrative domains and may be geographically distant. Each of the nodes may be thought of as a discrete system that can perform work and has access to a network. Computational grids are often more cost-effective than supercomputers of equal computing power. Grid Characteristics There is an important relationship between this view and the processes that regulators and electric utilities use in defining grid modernization strategies and roadmaps. These processes typically start with a set of objectives that lead to a determination of the necessary assets and improvements to be made in the grid modernization process. In practice, it is not unusual to see objectives that relate directly to properties rather than to qualities, but this is because the nature of these two categories, their relationships, and the reasons for them are typically not understood. 10.5 Keywords/Abbreviations  Grid Computing: Computational grid is a hardware and software infrastructure that provides independent pervasive and inexpensive access to high end computational capabilities.  Geographical Distribution: Grid’s resources may be located at distant places.  Resource Management: A defining feature of computational grids is that they involve sharing of networks, computers and other resources. This sharing introduces challenging resource management problems that are beyond the state of the art in a variety of areas.  Heterogeneity: A grid hosts both software and hardware resources that can be very varied ranging from data, files, software components or programs to sensors, scientific instruments, display devices, personal digital organizers, computers, supercomputers and networks.  Pervasive Access: The grid must grant access to available resources by adapting to a dynamic environment in which resource failure is commonplace. CU IDOL SELF LEARNING MATERIAL (SLM)

182 Advanced Computer Networks Abbreviations  DIS: Distributed Interactive Simulation  QoS: Quality of Service 10.6 Learning Activity 1. Describe Grid characteristics related to Security and Resource Management. ----------------------------------------------------------------------------------------------------------- ----------------------------------------------------------------------------------------------------------- 2. Define Homogeneity and Heterogeneity of Grid Computing. ----------------------------------------------------------------------------------------------------------- ----------------------------------------------------------------------------------------------------------- 10.7 Unit End Questions (MCQs and Descriptive) A. Descriptive Type Questions 1. Explain Grid and its features and characteristics. 2. What are the different issues in Grid Computing? B. Multiple Choice/Objective Type Questions 1. __________ characteristics of a grid should be seen as a single virtual computer. (a) Resource Sharing (b) Scalabilty (c) Transparent Access (d) None of the above 2. __________ issue provides significant challenge to provide tools that allow programmers to understand and explain program behavior and performance. (a) Programming Models and Tools (b) End Systems (c) Security (d) System Architecture 3. __________ feature of grid must grant access to available resources by adapting to a dynamic environment in which resource failure is common place. (a) Request-URL (b) Response-URI (c) Pervasive access (d) Request-URL CU IDOL SELF LEARNING MATERIAL (SLM)

Computational Grids 183 4. __________ issue is challenge for major advances in the technologies used to transport, switch, route and manage network. (a) End Systems (b) System Architecture (c) Resource Management (d) Network Protocols and Infrastructure 5. __________ is DIS. (a) Distributed Internet Simulation (b) Distributed Interactive Simulation (c) Distributed Interactive Software (d) Dual Interactive Simulation Answers 1. (c), 2. (a), 3. (c), 4. (d), 5. (b) 10.8 References 1. https://www.globus.org/sites/default/files/chapter2.pdf_ 2. https://www.google.com/search?q=introduction+to+grid+computing&rlz=1C1CHBD_ enIN893IN893&oq=introduction+to+grid&aqs=chrome.0.0j69i57j0l6.8985j0j8&sourcei d=chrome&ie=UTF-8 3. https://www.researchgate.net/publication/2561452_Grid_Characteristics_and_Uses_a_ Grid_Definition 4. Dillenbourg, P. (1999), Collaborative Learning: Cognitive and Computational Approaches, Elsevier Science, Oxford, Google Scholar. 5. Grimshaw, A. (2002), What is a Grid?, Grid Today, 1(26), Google Scholar. CU IDOL SELF LEARNING MATERIAL (SLM)

UNIT 11 P2P NETWORKS Structure: 11.0 Learning Objectives 11.1 Introduction 11.2 WMN Design 11.3 Introduction to SIP 11.4 Characteristics and Addressing 11.5 Components of SIP 11.6 SIP Session Establishment 11.7 SIP Security 11.8 Summary 11.9 Keywords/Abbreviations 11.10 Learning Activity 11.11 Unit End Questions (MCQs and Descriptive) 11.12 References 11.0 Learning Objectives After studying this unit, you will be able to:  Describe the components of SIP  Explain SIP session establishment  Discuss SIP security CU IDOL SELF LEARNING MATERIAL (SLM)

P2P Networks 185 11.1 Introduction Peer-to-peer (P2P) computing or networking is a distributed application architecture that partitions tasks or workloads between peers. Peers are equally privileged, equipotent participants in the application. They are said to form a peer-to-peer network of nodes. Peers make a portion of their resources, such as processing power, disk storage or network bandwidth, directly available to other network participants, without the need for central coordination by servers or stable hosts. Peers are both suppliers and consumers of resources, in contrast to the traditional client-server model in which the consumption and supply of resources is divided. Emerging collaborative P2P systems are going beyond the era of peers doing similar things while sharing resources, and are looking for diverse peers that can bring in unique resources and capabilities to a virtual community thereby empowering it to engage in greater tasks beyond those that can be accomplished by individual peers, yet that are beneficial to all the peers. 11.2 WMN Design Wireless mesh networks (WMNs) are communication networks which comprise radio nodes in which nodes are arranged in a mesh topology. Mesh topology is an interconnection of all nodes connected with all other nodes in the network. The network includes devices like nodes, clients, routers, gateways, etc. As the nodes are fully connected, mesh networks are usually less mobile as rerouting is less difficult in predicting the reroute results in delay in data transmission. Mesh clients can be of any wireless devices like cellphones, laptops, etc. The gateways which act as forwarding nodes may not be connected with the Internet. As different devices come under a single network, it is also referred as mesh cloud. WMN is self-healable. It works better with various different networks which include cellular networks and IEEE 802.11, 802.15 and 802.16 as well. WMN is flexible to work with more than one protocol. 11.3 Introduction to SIP Session Initiation Protocol (SIP) is a signaling protocol used for initiating, maintaining, modifying and terminating real-time sessions that involve video, voice, messaging and other communications applications and services between two or more endpoints on IP networks.  SIP is a signalling protocol used to create, modify and terminate a multimedia session over the Internet Protocol. A session is nothing but a simple call between two endpoints. An endpoint can be a smartphone, a laptop or any device that can receive and send multimedia content over the Internet. CU IDOL SELF LEARNING MATERIAL (SLM)

186 Advanced Computer Networks  SIP is an application layer protocol defined by IETF (Internet Engineering Task Force) standard. It is defined in RFC 3261.  SIP embodies client-server architecture,d the use of URL and URI from HTTP, and a text encoding scheme and a header style from SMTP.  SIP takes the help of SDP (Session Description Protocol) which describes a session and RTP (Real-time Transport Protocol) used for delivering voice and video over IP network.  SIP can be used for two-party (unicast) or multiparty (multicast) sessions.  Other SIP applications include file transfer, instant messaging, video conferencing, online games and steaming multimedia distribution. SIP Application Layer Protocol Basically, SIP is an application layer protocol. It is a simple network signaling protocol for creating and terminating sessions with one or more participants. The SIP protocol is designed to be independent of the underlying transport protocol. So, SIP applications can run on TCP, UDP or other lower-layer networking protocols. The following illustration depicts where SIP fits in the general scheme of things: Typically, the SIP protocol is used for internet telephony and multimedia distribution between two or more endpoints. For example, one person can initiate a telephone call to another person using SIP, or someone may create a conference call with many participants. CU IDOL SELF LEARNING MATERIAL (SLM)

P2P Networks 187 The SIP protocol was designed to be very simple, with a limited set of commands. It is also text-based. So, anyone can read a SIP message passed between the endpoints in a SIP session. 11.4 Characteristics and Addressing SIP is an ASCII protocol that facilitates the formation, modification and execution of communication sessions between individual or multiple participants. The participants can either be a person (videoconferencing clients) or an automation component (voicemail server) or a device that can interact in a similar manner. Various interaction types can be incorporated in these communications, including peer-to-peer or multipoint communication. Users have an address that simulates an e-mail address for identification and location purposes. Peer-to-peer SIP (P2P-SIP) is an implementation of a distributed voice over Internet Protocol (VoIP) or instant messaging communications application using a peer-to-peer (P2P) architecture in which session control between communication endpoints is facilitated with the Session Initiation Protocol (SIP). In a pure peer-to-peer application architecture, no central servers are required whereas traditional SIP telephony networks have relied on using centrally deployed and managed SIP servers, in analogy to the centralized switching architecture of the public switched telephone network (PSTN). P2P application design can improve scalability and survivability in the event of central network outages. The Session Initiation Protocol is in principle a client-server protocol. However, it has been described in analogy to the P2P relationship, called a dialog, which is defined by a unique combination of SIP protocol parameters (To-tag, From-tag, Call-ID). Both endpoints of a communication session implement a user-agent server and a user-agent client, which enables any two user agents to communicate directly with one another without the mediation of another a central switching system. SIP also provides facilities of registering (REGISTER request) the network location of a user agent with other SIP elements and subscription (SUBSCRIBE request) and notification (NOTIFY request) features for event tracking between user agents. Based on these inherent SIP features, it is possible to construct a peer-to-peer network of SIP nodes. In another approach, SIP over P2P, the SIP location service is replaced by conventional P2P overlay networking approach, such as the OverSim framework. In this model, the overlay network is used for service or node discovery and rendezvous. The search key in such a mechanism is the Uniform Resource Identifier (URI) of a user agent. This URI requires resolution to a particular device or Uniform Resource Locator (URL) that must be performed in real time. CU IDOL SELF LEARNING MATERIAL (SLM)

188 Advanced Computer Networks P2P-SIP systems may employ structured peer-to-peer approaches as well as unstructured peer-to- peer architectures. SIP Key Points SIP has four key functions provided by that facilitates various interaction capabilities. Think of SIP as a building being built with different capabilities as it is being built. Name Mapping and Redirection This involves the translation of participants’ (clients’) descriptive naming information to SIP location information. This function is one of two which occurs during the session’s setup. Capabilities Negotiation This incorporates the second function occurring during session setup. The various media capabilities of the participants are determined by the SIP in order to assure appropriate usage of media facilities during the session. Participant Management This SIP function enables participant management by allowing participants to control the incorporation of new arrivals into a session or the termination of existing participants during a session. An example of this would be establishing a conference session and adding additional users to the session so that they too can participate in full multimedia session. Capabilities Management SIP is able to monitor the media capabilities during a session and thus make the appropriate adjustments when necessary. This dynamic capability will adjust the client’s interaction with other clients by adjusting the session dynamically to reflect a compounded matrix of capabilities. All SIP-based communication sessions share at least three typical separate activities and protocols. They are as follows: 1. SIP provides the basic signaling between participants to set up the session. 2. SIP uses the Session Description Protocol (SDP) to classify the nature of the communication utilized within session. 3. SIP uses the suitable protocol to convey information in the session. CU IDOL SELF LEARNING MATERIAL (SLM)

P2P Networks 189 SIP Characteristics There are five methods that are used for establishing and terminating multimedia communications. Establishing and terminating multimedia communications produces the appended results as shown below in the functionalities that SIP can provide: SIP aids in name mapping, address resolution and redirecting calls.  Determination of media capabilities of the target endpoint: SIP provides determination of the least level of common services that exist between the endpoints. Multimedia capabilities that are supported by endpoints are used for establishing conferences.  Determination of availability of the target endpoint: In case due to unavailability of the target endpoint, SIP undertakes determination if the party to whom the call has been made is already connected to a call or has not answered the call within the specified number of rings. Once the reason for non-availability is determined, a message is returned reporting the same.  Establishing a session between the originating and target endpoints: In case the call is capable of being completed, SIP establishes a session between the originating and the target points. It is also possible to undertake changes in the middle of a call. For example, an endpoint can be introduced during a call.  Managing the transfer and termination of calls: SIP allows transfer of calls between endpoints. Structure of a SIP Address A SIP address is a lot like an e-mail address, in that it also serves as a locator of the user. SIP addresses even look very similar to e-mail addresses. Like e-mail addresses, they are comprised of two parts: a username and a domain. A SIP address resembles an e-mail address. The structure is: sip:user@domain:port As an example, this is a SIP address obtained by registering with Ekiga: sip:[email protected] In this example, sip denotes the protocol and does not change. It starts every SIP address. Some SIP addresses are passed without the sip part since it is understood as the format. CU IDOL SELF LEARNING MATERIAL (SLM)

190 Advanced Computer Networks The user name is the part you choose when you register for a SIP address. It can be a string of numbers or letters. In this example, the user part is nadeem.u. In other addresses, it may be a phone number (as used for SIP trunking for PBX systems) or any other combination of letters and numbers. The At symbol (@) is mandatory between the user and the domain, as is the case with an e- mail address. The domain name of the service you registered with appears immediately following the At symbol. It can be a fully qualified domain or simply an IP address. In this example, the domain is ekiga.net. Other examples are sip.mydomain.com and 14.18.10.23. You do not control the domain name as a user. The port is optional and is absent from SIP addresses most of the time because there is no technical reason for their explicit presence in many cases. When a port appears, it denotes the port to access on a proxy server or another server dedicated to the SIP activity. Examples of SIP addresses include: sip:[email protected], the Ekiga test number used to test a SIP configuration sip:[email protected] sip:[email protected]:5090 A SIP address is different from a phone number and an e-mail address in that it is attached to the user and not to the service provider. It follows you wherever you go and is not tied to the service as is a phone number. Where to Get a SIP Address? You can obtain free SIP addresses from several providers online. How to Use a SIP Address? Use your SIP address to configure a SIP client. Businesses use a service to set up the system and provide a SIP address for each employee. Then give the SIP address to your friends and clients who use SIP. So, there is free voice and video communication between you and them. You can also use your SIP address to contact people who do not use SIP on their landline or mobile phones. This requires a paid service to terminate the call from the IP network to the phone network. CU IDOL SELF LEARNING MATERIAL (SLM)

P2P Networks 191 Do not overlook the VoIP services out there. People who use regular phones can also call you on your SIP address, but you need to have a phone number attached to the SIP address, which is their handle to you. For communication over the internet, SIP is interesting, with the many features associated with voice and video calls, often involving multiple parties. For that, choose a good SIP client and enjoy. 11.5 Components of SIP The Five SIP Components 1. User Agent Client (UAC) 2. User Agent Server (UAS) 3. Proxy Server 4. Redirect Server 5. Registrar Server User Agent Client (UAC) UAC is one of two client-side components, the other being the User Agent Server (UAS). The UAC is an application that initiates up to six feasible SIP requests to a UAS. The six requests issued by the UAC are: INVITE, ACK, OPTIONS, BYE, CANCEL and REGISTER. When the SIP session is being initiated by the UAC SIP component, the UAC determines the information essential for the request, which is the protocol, the port and the IP address of the UAS to which the request is being sent. This information can be dynamic and this will make it challenging to put through a firewall. For this reason, it may be recommended to open the specific application type on the firewall. The UAC is also capable of using the information in the request URI to establish the course of the SIP request to its destination, as the request URI always specifies the host which is essential. The port and protocol are not always specified by the request URI. Thus, if the request does not specify a port or protocol, a default port or protocol is contacted. Using this method may be the preferred message when not using an application layer firewall like a Cisco PIX, application layer firewalls like to know what applications are flowing through which ports and it is possible CU IDOL SELF LEARNING MATERIAL (SLM)

192 Advanced Computer Networks using content types that other applications other than the one you are trying to let through be denied. User Agent Server (UAS) UAS is the Server that hosts the application responsible for receiving the SIP requests from a UAC, and on reception, it returns a response to the request back to the UAC. The UAS may issue multiple responses to the UAC, not necessarily a single response. Communication between UAC and UAS is client-server and (peer-to-peer). Proxy Server The proxy server as in most cases acts as mediator that services the requests or forwards them to other UASs or UACs for servicing. Proxy server can use an intra-organizational configuration through which to route all its SIP communications. Intra-organizational configuration can be described when user’s messages are routed through a proxy server before the messages are relayed to the destination SIP client. This occurs when initiating a SIP session to another user within the same organization. This can be useful for internal communication where security over an internet link can be a problem. The inter-organizational configuration is an extension of the intra-organizational one. Users from various organizations have their UA configured to be directed to their respective proxy servers. The proxy servers then communicate with each other to convey the message. Proxy server can also be used for name mapping, i.e., a proxy server can question a location service and map an external SIP identity to an internal SIP identity. These proxy servers are not firewalls. They are independent servers on the internet that proxy the request on behalf of the user for various reasons. Redirect Server The redirect server allows for redirection which enables users to temporarily change geographic location and still be contactable through the same SIP identity. In the future, this will be the way that telephone communications will work and with the arrival of wireless is an accommodating way to enable the client to be handed over from server to server as the user moves around. The RTC server implements the proxy server and the redirect server on one server. A server with combined functions is called a SIP server. Determination of how the SIP messages will be processed, i.e., whether the messages go to the proxy or the redirect server is determined through the configuration settings on the SIP server. Using this technology, it is also possible to keep the service running while some of the servers are being worked on and maintained. CU IDOL SELF LEARNING MATERIAL (SLM)

P2P Networks 193 Registrar Server The Registrar server makes it possible for users to alter the address at which they are contactable. This is possible through the SIP client sending a REGISTER request of change of an address to the registrar server, which then accepts the request and records the user’s new address. There are two ways in which the SIP clients can contact the registrar server. The first way is through a direct approach by utilizing information that is configured into the client. Secondly, through an indirect approach, which users the multicast address to contact the registrar server. The registrar function can also be added to the SIP server containing the proxy server and redirect server as discussed previously. Thus, the RTC server implements the proxy, redirect and registrar functions on one SIP server. This function can only be performed once authentication has taken place and valid user credentials are checked. SIP uses port UDP5050 to communicate and establish connectionless sessions to servers and clients on ports specified during the session. There is a move afoot to use SIP more and more on IP-compatible PSTN networks as telephone switching starts to become incorporated into interconnected LANs, WANs and MANs. Telecommunication looks bright and affordable if this protocol is harnessed. Some search engines are already beginning to harness the technology’s potential by planning to incorporate a call now feature after searching for a company or resource takes place. Where is Client X Redirect Server Client X is linked to Server ABC Client A SIP Gateway Server ABC Proxy Server Client X Register Server City Fig. 11.1: One Client Links to Another Client using the SIP Infrastructure CU IDOL SELF LEARNING MATERIAL (SLM)

194 Advanced Computer Networks 11.6 SIP Session Establishment Session Initiation Protocol (SIP) is an application layer signaling protocol for creating, modifying and terminating multimedia sessions (voice, video or data) with either one or more participants (Johnston, 2000; Schulzrinne and Rosenburg, 2000; Arora and Jain, 1999). SIP does not define what a session is. This is defined by the content carried opaquely in SIP messages. To establish a multimedia session, SIP has to go through the following stages:  Session initiation: Initiating a session is perhaps the hardest part because it requires determining where the user to be contacted is residing at the current moment. The user may be at home working on a home PC or may be at work on an office PC. Thus, SIP allows users to be located and addressed by a single global address (usually an e-mail address) irrespective of the user’s physical location.  Delivery of session description: Once the user is located, SIP performs the second function of delivering a description of the session that the user is invited to. SIP itself is opaque to the session description in the sense that it does not know anything about the session. It merely notifies the user about the protocol to be used so that the user can understand the session description. Session Description Protocol (SDP) is the most common protocol used for this purpose. SIP can also be used to decide a common format to describe a session so that protocols other than SDP can also be used.  Active session management: Once the session description is delivered, SIP conveys the response (accept or reject) to the session initiation point (the caller). If the response is “accept,” the session becomes active. If the session involves multimedia, media streams can now be exchanged between the two users. RTP and RTCP are some common protocols for transporting real-time data. SIP can also be used to change the parameters of an active session, such as removing some video media stream or reducing the quality of the audio stream.  Session termination: Finally, SIP is used to terminate the session. Thus, SIP is only a signaling protocol and must be used in conjunction with other protocols like SDP, RTP or RTCP to provide a complete multimedia service architecture as the one provided in H.323. Note that the basic functionality and operation of SIP does not depend on any of these protocols. The SIP signaling system consists of the following components:  User agents: The end system acts on behalf of a user. If the user-agent initiates SIP requests, it is called user-agent client (UAC); a user-agent server (UAS) receives such requests and return responses. CU IDOL SELF LEARNING MATERIAL (SLM)