Implementing voice over Internet protocol in mobile ad hoc network – analysing its features regarding efficiency, reliability and security Naveed Ahmed Sheikh1, Ashfaq Ahmad Malik1, Athar Mahboob2, Khairun Nisa3 1PN Engineering College, National University of Science & Technology, Karachi, Pakistan 2Department of Electrical Engineering, DHA Suffa University, Karachi, Pakistan 3Department of Computer Science and Engineering, University of Engineering & Technology, Lahore, Pakistan E-mail: [email protected]; [email protected] Published in The Journal of Engineering; Received on 1st February 2014; Accepted on 4th March 2014 Abstract: Providing secure and efficient real-time voice communication in mobile ad hoc network (MANET) environment is a challenging problem. Voice over Internet protocol (VoIP) has originally been developed over the past two decades for infrastructure-based networks. There are strict timing constraints for acceptable quality VoIP services, in addition to registration and discovery issues in VoIP end-points. In MANETs, ad hoc nature of networks and multi-hop wireless environment with significant packet loss and delays present formidable chal- lenges to the implementation. Providing a secure real-time VoIP service on MANET is the main design objective of this paper. The authors have successfully developed a prototype system that establishes reliable and efficient VoIP communication and provides an extremely flexible method for voice communication in MANETs. The authors’ cooperative mesh-based MANET implementation can be used for rapidly deployable VoIP communication with survivable and efficient dynamic networking using open source software. 1 Introduction also a bandwidth constraint in such a wireless network because it lacks access points and high-speed wired links. Furthermore, Our objective in this paper was to develop a prototype system to es- since the current routing protocols do not focus much on the secur- tablish reliable and efficient voice over Internet protocol (VoIP) ity aspects, MANETs are also more vulnerable to security threats as communication and provide an extremely flexible method for compared with traditional wired networks [3]. VoIP in mobile ad hoc networks (MANETs) using Smartphone and tablets running the Android operating system. We successfully 2.2 Survey of MANETs implementations on Android established cooperative mesh-based MANET with optimised link state routing (OLSR) as the routing protocol for rapidly deployable Ad hoc networking support on Linux-based laptop and desktop PCs VoIP communication. The system is survivable and efficient sup- has matured in recent years [4]. However, it is still an open research porting dynamic networking using open source software (OSS) problem for Android devices reason being that Android Open Source modules such as modified wireless fidelity (WiFi) Tethering [1] Project has not formally supported ad hoc network implementation in and PTTDroid [2] VoIP application. Android Kernel [5]. Primarily, Android OS is designed to work in in- After this short introduction Section 2 discusses the background frastructure mode or managed network scenario. In a managed information. Section 3 is about solution implementation and network, the client node is connected to an access point (AP) after describes the configuration of the application on Android and per- authentication. It utilises the wpa_supplicant command line utility sonal computer (PC) platforms. Section 4 covers security aspects for configuration as is done in standard Linux as well. Ad hoc net- considered for the proposed application. Section 5 discusses works on the other hand do not use AP devices for centralised man- performance-based results gathered on pre-set criteria. Finally, we agement and each device has the capability to do the routing for conclude and discuss future work in Section 6. others. The versions of Android older than the Ice Cream Sandwich (ICS) only supported managed networking. The 2 Background information direct-WiFi utility in ICS also does not cater to full ad hoc support. Hence, one has to resort configuring wireless chip through use of 2.1 MANETs iwconfig command supplying the parameters of wireless interface. MANETs are peer-to-peer self-organising networks and do not The Linux Kernel must also support wireless extension (WEXT) ap- require a fixed infrastructure. The nodes of a MANET have to self- plication programming interface (API) [6]. Next, we review some of configure in some arbitrary manner in order to perform their func- existing approaches to enabling ad hoc networking in Android. tion in the absence of a fixed infrastructure. The areas with depleted The Smartphone ad hoc network (SPAN) project [7] has con- fixed infrastructures can be a place where a natural disaster has oc- ducted significant work in this area and has developed few applica- curred such as an earthquake, flood or where a chaotic situation has tions such as MANET Manager, MANET Voice Chat and MANET been created by humans such as in a battlefield. The MANET nodes Visualiser. Stoker’s SPAN project used Mueller’s WiFi Wireless can directly communicate with each other because either they are in Tethering [8] initially. Its functions include tethering and executing the required radio range of each other or otherwise multi-hop the OLSR Daemon. Its graphical user interface (GUI) is very user routing can be used to establish connectivity. Well-known multi- friendly. However, it only supports WEXT Kernel resulting in ap- hop routing protocols include OLSR, a proactive routing protocol plicability to a limited number of Android devices. Samsung and ad hoc on-demand distance vector, a reactive routing protocol. Galaxy Tab 10.1, S II Epic Touch 4G SPH-D710, Nexus Since the MANET nodes may be in continuous motion and may SCH-I515, S III GT-I9300 I9300UBDLJ1, S-IIIGT-I9300, move into and out of the radio range of each other, frequent break- I9300XXBLH1 and ASUS Transformer Prime TF201, Nexus-7 age of data links can occur, resulting in high vulnerability of wire- are the devices supported by SPAN’s MANET Manager [6]. less link between nodes. The topology of a MANET is highly We have also successfully tested SPAN’s MANET Manager ap- dynamic, therefore routing information also changes. There is plication with limited functionalities on XPOD Bubblegum Tablet J Eng 2014 This is an open access article published by the IET under the Creative Commons doi: 10.1049/joe.2014.0035 Attribution License (http://creativecommons.org/licenses/by/3.0/) 1 (installed with ICS 4.0.4) and XPOD Tabloid running Jelly Beans (JB 4.1.1). Details are provided in the implementation section. However, it did not run successfully on all Smartphone devices such as Q-Mobile A8 or A950 installed with JB 4.1.1. Commotion [9] is another project demonstrating work on mesh networking for Android-based Smartphone, tablets, laptops, PCs, cellular networks and routers. The characteristic features of their implementation include tethering and executing OLSR protocol. It has a user friendly GUI. However, several shortcomings of their implementation hinder it from wide adoption. These include failure of proper execution of tethering application. Consequently, OLSR protocol also fails to execute. There are a few other projects also that have worked on MANETs or mesh networks on Android platform such as Thinktube [4], Barnacle [10], Open Garden [11], WiFi Tethering by Opengarden [12], WiFi ad hoc Enabler [13], Serval [14] etc. In our paper, we have mainly improved the WiFi Wireless Tether [8] application to work reliably in ad hoc mode along with OLSR. Details are pro- vided in the implementation section. Fig. 2 Ad hoc network configuration 2.3 VoIP in MANET Following configuration was set on laptop running with The VoIP technology has been a hot issue in the Information Ubuntu-12.04: Technology industry for more than ten years now. Providing a secure real-time VoIP service on the MANET is the main design objective of this research. It is perceived to be a difficult task † sudo ifconfig wlan0 10.10.10.10 netmask 255.255.255.0 because of restrictions in device resources, adverse properties of † sudo iwconfig wlan0 mode ad hoc the wireless channel, dynamic topology and the lack of central ad- † sudo iwconfig wlan0 essid ‘test’ ministration. In addition, the flexibility of the VoIP system and the † sudo iwconfig wlan0 channel 4 convergence of voice and data networks bring in additional security † sudo iwconfig wlan0 key off risks. All devices in an Internet protocol (IP) network become po- tential active or passive adversaries. It can be seen that the under- lying IP data network facility that a VoIP system relies on Owing to some built-in shortcomings of the Android JB 4.1.1 for complicates the security assurance requirement. XPOD Tabloid, the ad hoc node with essid ‘test’ could not be detected on the Tabloid device. However, it was displayed as (*) test on XPOD Bubblegum Tablet which was connected in ad hoc 3 Solution implementation mode with Ubuntu laptop. Following routing information was also updated on XPOD tablets as shown in Fig. 3. 3.1 Implementing MANET Manager The Stoker’s MANET Visualiser application created following As already discussed in Section 1, Stoker’s MANET Manager has link diagram as shown in Fig. 4. contributed significantly to implementation of ad hoc network on Using MANET Manager’s built-in messenger, hello chat mes- Android devices. We were able to localise two low-end Android sages were also exchanged on both tablets as shown in Fig. 5. tablets available as commercial off the shelf (COTS) which support WEXT and successfully installed MANET Manager appli- cation available on Play Store [5]. This was managed by lot of testing and trials. Snapshot of MANET Manager running in ad hoc mode is shown in Fig. 1. XPOD Bubblegum and Tabloid Tablets were assigned IP addresses as 10.10.10.20/24 and 10.10.10.60/24. However, the tablets did not connect to each other in ad hoc mode.