High Available VoIP Server Failover Mechanism in Wide Area Network

Abstract

Voice over Internet Protocol (VoIP) MOS). The work utilizes Xen® Hypervisor with modified Remus extensions to provide the High Availability environment with GRE tunnelling and newtwork virtualization. Remus approach using checkpoint based is deployed to copy the primary server to the backup server. A range of 40ms -900ms has been applied as time interval of checkpoint. The results show that the the failover downtime is 1.4 s and mean jitter is 9,98 ms, packet loss 3,12% and MOS 3.61 for Remus 400ms checkpoint. MOS with different checkpoint time interval is also presentedKeywords: VoIP, High Availability, Virtualization, Tunneling, WAN IntroductionTraditional telephony carriers using circuit based switching has been designed as voice carrier. It is a very good technology in early communication since users only need voice service. User's needs in communication technology are then increase and varying, such as voice connection, video call, email, instant messaging, web browsing and others multimedia services. These needs, however are not suitable to be implemented using traditional circuit based switching. Thus, packet based switching using Internet Protocol (IP) become more attractive to fulfill this requirement.Telecommunication technology is also improved, in which the IP based technology had been chosen as next generation network. Voice over Internet Protocol (VoIP) introduced to overcome future telephony demand. Public or private networks have been utilised as the backbone of VoIP service. The utilisation of established internet network is one of VoIP advantage, therefore telecommunication providers do not need to build another special network to run VoIP service. However, these rapid changes are having problems, hence various researches have been done to make sure IP telephony could provide availability and reliability equally to circuit based telephony.One of the most significant challenges in next generation network is how to provide high carrier-grade for VoIP to overcome the public telephony availability and fault tolerant system. Availability means the ability of server to be in state to perform required services that client requested at any given time interval. Telephony industries demand the availability that have to reach 99.999 percent of the time, well known as five nine rules, which means those networks must have the maximum of 5 minutes downtime over a year [1]. VoIP as new emerging technology in telephony uses non reliable protocol since IP is firstly developed for packet delivering. However, to be able to replace the traditional telephony, this availability requirement should be fullfilled.

Performance evaluation for outdoor wireless scenarios based on IEEE 802.11b/g in the presence of co-channel interference

“…Additionaly, in [8] was proposed an adaptive scheduling method for emissions based on network statistics, PL rate and packet availability . Otherwise, the performance evaluation of WiFi technology in an indoor environment was presented in [9 -11], a handover analysis was performed in [12] with conventional Extended Service Set (ESS) infrastructure with VoIP services and QoS assurance, and some methods to improve the quality of VoIP over a WLAN mesh were presented in [13], the capacity of switching mechanisms using failover mechanisms in a WAN and the quality of VoIP calls was studied in [14], also verifying the inherent limitations of the Distributed Coordination Function (DCF) to calculate the maximum number of VoIP clients a single Access Point (AP) can support, in which support 12 simultaneous VoIP calls considering G711 voice codec and 14 simultaneous VoIP calls considering G729 voice codec over a wireless network [15]. In [16] was showed low VoIP capacity in a WLAN and the unacceptable performance in the presence of coexisting traffic, another way to evaluate the behavior of the standard was by generating real calls by the software PBX-VoIP Asterisk, in [17] an outdoor environment was presented, and a total of simultaneous sessions were found that can be performed by using G729 voice codec reaching 25 simultaneous sessions, while with G711 voice codec 20 simultaneous sessions were obtained, also a traffic injection strategy was used in [18], by using Distributed Internet Traffic Generator (D-ITG), in where a laboratory environment was analyzed, in such environment was reached six clients connected wirelessly to an AP where the codec with the best stability was the G723.…”