Gonzalo Camarillo

Evaluation of transport protocols for the session initiation protocol

SCTP is a newly developed transport protocol tailored for signaling transport. Whereas in theory SCTP is supposed to achieve a much better performance than TCP and UDP, at present there are no experimental results showing SCTPs real benefits. This article analyzes SCTPs strengths and weaknesses and provides simulation results. We implemented SIP on top of UDP, TCP, and SCTP in the network simulator and compared the three transport protocols under different network conditions.

Study on maintenance operations in a chord-based Peer-to-Peer session initiation protocol overlay network

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.

Effects of mobility and multihoming on transport-protocol security

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.

Towards an innovation oriented IP multimedia subsystem [IP Multimedia Systems (IMS) Infrastructure and Services]

This article proposes an approach to IMS policy control based on session policies that achieve transparent end-to-end session establishments between IMS terminals. The article identifies drawbacks in the current IMS policy control methodology, discusses how these drawbacks may negatively influence the potential of IMS to provide innovative services, and describes how the new approach overcomes these drawbacks. Our proposal offers modularity and scalability properties that enable operators to establish policies and modify existing ones without major changes in the IMS core. Thus, policies can be applied transparently to SIP dialogs between terminals and modified on the fly without tearing down ongoing dialogs. The article also discusses a test bed implementation that worked as a proof-of-concept

Impact of Network Address Translator Traversal on Delays in Peer-to-Peer Session Initiation Protocol

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).

Analysis of Delays in a Peer-to-Peer Session Initiation Protocol Overlay Network

Peer-to-Peer Session Initiation Protocol (P2PJSIP) 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.

IMS: The New Generation of Internet-Protocol-Based Multimedia Services

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.

Estimating operating conditions in a Peer-to-Peer Session Initiation Protocol overlay network

Distributed Hash Table (DHT) based peer-to-peer overlays are decentralized, scalable, and fault tolerant. However, due to their decentralized nature, it is very hard to know the state and prevailing operating conditions of a running overlay. If the system could figure out the operating conditions, it would be easier to monitor the system and re-configure it in response to changing conditions. Many DHT-based system such as the Peer-to-Peer Session Initiation Protocol (P2PSIP) would benefit from the ability to accurately estimate the prevailing operating conditions of the overlay. In this paper, we evaluate mechanisms that can be used to do this. We focus on network size, join rate, and leave rate. We start from existing mechanisms and show that their accuracy is not sufficient. Next, we show how the mechanisms can be improved to achieve a higher level of accuracy. The improvements we study include various mechanisms improving the accuracy of leave rate estimation, use of a secondary network size estimate, sharing of estimates between peers, and statistical mechanisms to process shared estimates.

Reducing delays related to NAT traversal in P2PSIP session establishments

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.

Towards the Convergence between IMS and Social Networks

The need of interaction, communication, and data and affections interchange is speeding up the evolution of the technologies that permit the proliferation of social networks. This paradigm permits people with common interests to feel closer and to interchange content. The present work analyzes the necessity of mobile social networks and proposes an integration between the current social networks and the new generation networks by providing new interfaces to the IMS architecture. Some advantages of this integration will be analyzed. Also, the new communication possibilities and enabler utilization (presence, group management) will be taken into consideration. To finalize, we present an example of integration between Facebook and IMS networks through a RESTful interface.