IETF Session Initiation Protocol Research Articles

Communications fabric for scientific collaboration

Today's fusion experiments are geographically and institutionally dispersed collaborations. This makes the need for good remote collaboration tools particularly acute. Informal interactions between scientists are particularly important and hard to realize with traditional communications approaches. We are testing existing packages based on the IETF SIP (session initiation protocol) standard and integrating them into our applications to address these issues. Development of additional tools may be needed to provide better integration and enhanced functionality. By providing a spectrum of tools encompassing instant messaging, voice, video, presence, event notification and application sharing, we hope to overcome technical hurdles and a natural reluctance, among researchers, to interact with colleagues who are not on site. Existing web pages, which support integrated and shared workspaces, such as electronic logbooks, code and experimental run management, records of presentations and publications, personnel databases, and physical site maps will be ‘communications enabled’, so that just as currently there are ‘mailto’ links we will be able to have ‘speak to:’, ‘instant message to:’, ‘video to:’, and ‘share with:’ links. Mechanisms will be provided for session portability; a conference might be moved from a hard phone to a soft phone so that video or application sharing could be enabled. This paper discusses our ongoing efforts in these areas, including a prototype implementation of some of these tools.

Mobile multimedia supports with hierarchical multicast SIP framework on heterogeneous wireless networks

For supporting the mobile host (MH) to be the multicast receivers on wireless networks, the traditional approaches such as the Hierarchical Remote Subscription (HRS) and Bi-directional Tunneling with Mobile Multicast (BT-MoM) integrate the Mobile IP protocol with the IP multicast technique. However, they inherit intrinsic problems to handle mobility and suffer significant delays to rebuild the multicast tree when the MH moves out of the multicast tree, which results in serious playback interruption and quality of service (QoS) degradation for the ongoing multimedia service especially when the MH are scattered over different kinds of wireless networks. In this paper, we propose a cross-layer framework and the Hierarchical Multicast Session Initiation Protocol (HMSIP), which extend the IETF Session Initiation Protocol (SIP) with the concept of multicast SIP session and integrate the underlying IP Multicast QoS routing protocol and the RSVP resource reservation technique, to support mobile multimedia multicasts. This framework significantly reduces handoff delays and deployment costs and hence achieves end-to-end QoS support for MHs on heterogeneous wireless networks. Further, we mathematically analyze handoff delays of the HRS, BT-MOM and HMSIP schemes. Moreover, simulation results show that the HMSIP can significantly achieve much more stable and lower handoff delays than those of the BT-MOM and HRS only with a small proportion of extra bandwidth than the bandwidth-optimal HRS, thereby supporting higher numbers of handoffs without interrupting multimedia playback of the mobile multicast activity. Tradeoffs between costs for deploying HMSIP Proxies in the framework and corresponding performances of the HMSIP families are discussed. Finally, multimedia QoS improvements of MHs are shown to emphasize advantages by integrating RSVP in this HMSIP framework.

A SIP-enabled all-IP architecture for converged next-generation networks

The success of converged next-generation networks (NGNs) will be contingent on the ability of subscribers to access data, voice, and other real-time multimedia services seamlessly, whether they are roaming wireline wide area networks (WWANs) or wireless local area network (WLAN) hot spots. Session Initiation Protocol (SIP) is one of the underlying technologies required to implement an access-agnostic Internet Protocol (IP) multimedia network infrastructure. In this paper, we investigate the key challenges involved in supporting SIP-based real-time (e.g., voice over IP [VoIP]) and multimedia services over heterogeneous networks and we describe a SIP-enabled all-IP architecture (SEAA) that leverages 3rd Generation Partnership Project/3rd Generation Partnership Project2 (3GPP/3GPP2) IP Multimedia Subsystem (IMS) framework, and IETF's SIP profile to support access-independent NGNs. We develop a multilayered policy-based quality of service (QoS) control mechanism and propose an interaction mechanism involving the application service layer, the session control layer, and the transport network layer to support end-to-end consistent QoS and service level agreements (SLAs). We address a SIP-based session control mechanism and the implications for unified service management and describe in detail the end-to-end SIP call flow in an example policy-based network to demonstrate the validity of our solution. We also analyze the interworking architecture between SIP and legacy networks.

Modelling and verification of interworking between SIP and H.323

There are currently two standards for signaling and control of Internet telephone calls, namely ITU-T Recommendation H.323 and the IETF session initiation protocol (SIP). Both protocols provide similar functionality using different mechanisms. Both H.323 and SIP provide interoperability, flexibility and scalability in different aspects and environments. Interworking between SIP and H.323 is essential to ensure full end-to-end connectivity through the network, although the current number of deployed commercial SIP endpoints is relatively small compared to widely deployed H.323 endpoints. To formally specify the SIP-H.323 Interworking, this paper gives a new system model for interworking between SIP and H.323. Five main components of this system are modeled using system description language and message sequence chart: H.323 endpoint, H.323 gatekeeper, SIP-H.323 Interworking facility, SIP server, SIP endpoint. We design and define the internal structure and behavior for each component, which is established for simulating and verifying interworking between SIP and H.323. Under two different configurations that both protocols work within the same administrative domain and that both protocols are operating in separate administrative domains, we use a series of scenarios to show that our model meets the functional specifications outlined in the SIP-H323-Interworking specification documents.

A protocol for wide area secure networked appliance communication

This article describes problems associated with remotely accessing networked appliances (e.g., from the Internet). Networked appliances are widely viewed as the next wave of devices on the Internet. We discuss some possible uses for networked appliances and the requirements for communicating with them. We present details of a solution to meet these communication requirements based on the IETF Session Initiation Protocol. In addition, we discuss the rationale for our approach and reasons other approaches were not adopted. An example of the use of the SIP in this domain is presented to illustrate how the solution can be used. We conclude with outstanding challenges and reiterate advantages of this approach.