Legacy networks, both fixed and mobile, which were originally designed for voice communications, are progressively migrating to new infrastructures that promise to revolutionize the services offered. In this paper, we will cover this new generation of personal communication services, with an emphasis on the family of Internet protocol (IP)-based multimedia subsystem (IMS)-aided infrastructure that relies on the session initiation protocol (SIP). As a benefit, the end users will enjoy a new generation of personal communications services that are accessible anywhere and anytime. These services are directly related to the end users rather than to their diverse devices. It is anticipated that the new deployments of next-generation networks (all-IP based) will accelerate the adoption of the IMS technology.

The use of the Internet for delivering real-time traffic flows makes it necessary to fragment the information into small pieces, thus making the traffic have a bad efficiency. In order to avoid this, the IETF defined TCRTP as a mechanism capable of compressing headers and multiplexing a number of RTP packets into a bigger one, which was sent using a tunnel. However, some new applications that can be considered real-time, generate UDP or TCP packets, but do not use RTP. Based on some research results deployed in the academic context, a proposal for widening the scope of this standard is being developed in collaboration with the industry. Different traffics could be considered, and this would imply the possibility of utilizing a number of header compression algorithms, and also different multiplexing and tunneling protocols. This new standard could be used by different enterprises, as network operators, network equipment developers and game providers.

This paper focuses on reducing the Network Address Translator (NAT) traversal-related components of the session establishment delay in peer-to-peer Session Initiation Protocol (P2PSIP) overlays. To reduce the delay, we propose to group the management of different connections so that the (time-consuming) NAT traversal procedures performed for one connection can be reused when establishing other connections. To do this, we propose to use the Host Identity Protocol (HIP) to perform connection management in P2PSIP overlays. In order to evaluate the performance gains resulting from this approach, we have implemented a P2PSIP system whose modular design allows us to build overlay networks with and without HIP and measure their differences in performance. Our experiments show that grouping the management of different connections results in a significant reduction in the session establishment delay in the presence of NATs.

Peer-to-peer session initiation protocol (P2PSIP) is a new decentralized person-to-person communication system that is currently being standardized in the Internet Engineering Task Force (IETF). P2PSIP uses the session initiation protocol (SIP) to enable real-time communication in a peer-to-peer environment. The underlying lookup mechanism is implemented using a distributed hash table (DHT). In this paper, we study delays associated with joining, leaving, and initiating calls in a P2PSIP system through experiments in PlanetLab. We also compare the performance of P2PSIP and traditional client-server SIP.

Peer-to-Peer Session Initiation Protocol (P2PSIP) is a distributed communication system being standardized in the Internet Engineering Task Force (IETF). Since it uses the peer-to-peer paradigm, P2PSIP faces the problems created by Network Address Translators (NATs); even peers located behind NATs need to be able to not only initiate connections to other peers but also accept connections initiated by other peers. In this paper, we study the impact of standardized NAT traversal solutions, namely Session Traversal Utilities for NAT (STUN), Traversal Using Relays around NAT (TURN), and Interactive Connectivity Establishment (ICE), on delays in P2PSIP overlay networks. These delays are studied from the viewpoint of wireless and wired nodes acting as clients in a P2PSIP overlay network running in the PlanetLab. The delays are also compared to those of the traditional client/server Session Initiation Protocol (SIP).

In this paper, we describe an architecture for the Host Identify Protocol (HIP) to automatically manage the path to be used between two hosts for a given traffic flow. Different simultaneous flows between the two hosts can take different paths. The architecture is based on and extends the Simultaneous Multiaccess (SIMA) HIP extension and the Interactive Connectivity Establishment (ICE) framework. A key property of the policy-based path management proposed in this paper is that it includes NAT (Network Address Translation) traversal functionality.

Today many Peer-to-peer (P2P) applications are widely used on the Internet. Especially file sharing is a popular P2P application that has, at least partially, replaced the centralized file sharing infrastructure. However, there are still a number of legacy applications that utilize a centralized infrastructure as opposed to a decentralized approach. In this paper we present a generic framework for decentralizing legacy applications. Even though we focus especially on Voice over IP (VoIP), email, and web applications, we believe that our framework could also be utilized with other legacy applications. A notable feature of our framework is that it does not require any changes to legacy applications.

Peer-to-Peer Session Initiation Protocol (P2PSIP) is a new technology being standardized in the Internet Engineering Task Force. A P2PSIP network consists of a collection of nodes organized in a peer-to-peer fashion for the purpose of enabling real-time communication using the Session Initiation Protocol (SIP). In this paper, we present experimental results obtained by running a P2PSIP prototype in PlanetLab. Our prototype uses the Chord Distributed Hash Table (DHT) to organize the P2PSIP overlay and Peer-to-Peer Protocol (P2PP) as the protocol spoken between the peers. In the experiments, the performance of the system is studied under different churn rates and using different DHT maintenance intervals.

The session initiation protocol (SIP) is an application-layer protocol to establish and manage sessions. SIP provides user mobility by having user agents register their location with a server in the network. The host identity protocol (HIP) is a shim layer between the network and the transport layers to establish and manage secure connections between hosts which may be mobile. In this paper, we propose a framework to combine SIP and HIP, and discuss the advantages of doing so. The advantages this framework provides relate to security, mobility, and multihoming. Additionally, we discuss how a P2P SIP (peer- to-peer SIP) system can be implemented on top of a HIP-based overlay network and the characteristics of such a system. We also offer some insights into an experimental prototype implemented as a proof-of-concept of the SIP-HIP interaction.

This paper evaluates several O(log n)-hop DHT (Distributed Hash Table) algorithms' suitability for interpersonal communications. DHTs have been widely used for file sharing, but recent research and standardization efforts are exploring their use for interpersonal communication as well. We identify the desired features of DHTs from the viewpoint of interpersonal communications and evaluate several current DHTs with respect to these features.

The Stream Control Transmission Protocol (SCTP) is a reliable message-based transport protocol developed by the IETF that could replace TCP in some applications. SCTP allows endpoints to have multiple IP addresses for the purposes of fault tolerance. There is on-going work to extend the SCTP multihoming functions to support dynamic addressing and endpoint mobility. This paper explains how the multihoming and mobility features can be exploited for denial-of-service attacks, connection hijacking, and packet flooding. We propose implementation guidelines for SCTP and changes to the mobility extensions that prevent most of the attacks. The same lessons apply to multihomed TCP variants and other transport-layer protocols that incorporate some flavor of dynamic addressing.