This paper describes the problem of locating terminals using E.164 numbers, and the problem of selecting a suitable gateway for calls from an IP telephony network to the public switched telephone network (PSTN). Generally, these are the problems of mapping the name of a destination into an address, and to find the best route to the destination in a combined IP and PSTN network. Number portabili...

Some services delivered in IP networks, like IP television, Telephony over IP and critical services, have strong robustness requirements. Consequently, the communications delivering those services must be resilient to failures in the network. This paper proposes a new approach to improve communication protection. It consists in deploying a routing overlay dedicated to resilience in an autonomou...

Session Initiation Protocol (SIP) is a control protocol standardized by IETF and implemented on the application layer. It can be used to establish, modify, and terminate Internet conferencing, telephony and some other multimedia sessions.[1] SIP uses server and client architecture, Peer-toPeer (P2P) is another popular technology that accomplishes the same functionality in an overlay network whe...

Deploying IP telephony or voice over IP (VoIP) is a major and challenging task. This paper describes an analytical design and planning simulator to assess the readiness of existing IP networks for the deployment of VoIP. The analytical simulator utilizes techniques used for network flows and queueing network analysis to compute two key performance bounds for VoIP: delay and bandwidth. The simul...

In this paper, we propose the use of QoS routing to enhance the support of IP Telephony. Our proposed scheme is based on QoS intradomain OSPF routing, an extension of the conventional OSPF routing protocol. A Diff Serv model is used (no per flow signalling, nor per flow accounting at intermediate nodes). Processing O/H is shifted from core to edge routers, which compute routes, monitor QoS path...

Recently problems with commercial IP telephony systems have been reported one after another, in Japan. One of the important causes is congestion in the control plane. It has been recognized that with the current Internet it is important to control not only congestion caused by overload of the data plane but also congestion caused by overload of the control plane. In particular, “retry traffic,”...

Session Initiation Protocol is currently receiving much attention and seems to be the most promising candidate as signaling protocol for the current and future IP telephony services, also becoming a real competitor to plain old telephone service. For the realization of such a scenario, there is the obvious need to provide a certain level of quality and security, comparable to that provided by t...

With rapid growth in use of multimedia applications, including IP Telephony (also known as Voice over IP), the demand for security and privacy of communications has significantly increased. Given the fact that IP Telephony utilizes public IP infrastructure, deployment of IP VPN is one approach to protect traffic of interest. However, VPN is presumed to have a negative impact on VOIP performance...

The two key resources in an IP Telephony network are the Internet Telephony Gateways (ITGs) and the IP network. These resources must be effectively managed to simultaneously provide good QoS to calls and maximize network resource utilization. This paper presents two main contributions. First, we design a call admission policy based on congestion sensitive pricing. As the load increases, this po...