Verification of Session Initiation Protocol Using Timed Colored Petri Net

In this work, Session Initiation Protocol model is established by using Timed Colored Petri Nets (TCPN). SIP (Session Initiation Protocol) is a protocol developed to assist in providing advanced telephony services across the Internet. The Session Initiation Protocol (SIP) has become the quasi-standard for Voiceover-Internet Protocol (VoIP) communications. SIP is based on a client–server infrastructure in which user agents represent the end-terminals as clients, proxy servers handle SIP message routing between the user agents, and registrar servers store the client’s contact information into a location service. By use of timed color set and useful time attributes in tokens defined in CPN tools, timer and time-related problems of SIP are modeled and analyzed. Timer is an important part for SIP, especially the INVITE transaction.

An rFC based service triggering algorithm for IMS network

To reduce the potential signaling traffic in IP multimedia subsystem （IMS）, the session establishment procedures were investigated. The serving call session eontrol function （S-CSCF） is the major bottleneck in IMS and the existing 3GPP service triggering algorithm （STA） based on initial filter eriteria （iFC） increases the end-to-end session setup delay remarkably. To reduce the session setup delay and improve the system performanee, a SIP response message based filter criteria （rFC） was proposed. Based on the rFC, a SIP response message based STA （RSTA） was further proposed. The modeling and theoretical analysis of 3GPP STA and RSTA were presented. Simulation results show that, compared with 3GPP STA, the RSTA can avoid the additional signaling traffie load of the S-CSCF and application server （AS） effectively, reduce the session setup delay eonsiderably, increase the throughput of the S-CSCF and improve the quality of service （QoS） of IMS network.

MSPnet: MANAGEABLE SIP P2P MEDIA DISTRIBUTION SYSTEM

The letter proposes a three-layer manageable media distribution network system architecture called MSPnet, which is based on Session Initiation ProtocolIll and Peer to Peer （SIP P2P） technology. MSPnet performs application-level structured DHT routing and resource location among domains and unstructured ones in domain. Except for media distribution, it can be used to support a variety of P2P applications, including video broadcasting, video on demand, VoIP, etc. MSPnet is composed of three layers, namely, the signal control layer, the management layer, and the media transportation layer. The MSPnet prototype consists of the SIP server, the management server, the media server, and the node User Agent （UA）. Results from a prototype experiment in a large-scale Internet environment show that MSPnet is feasible, scalable and manageable.

A P2PSIP System with Intelligent Routing Function on the Media Plane

Decentralized peer-to-peer session initiation protocol （P2PSIP） provides the same services as legacy SIPs such as IMS. However, in relatively open network, the requirement for route efficiency in a complex environment brings about undefined problems. To deploy a controllable P2PSIP network, perfect mechanisms have to be appended, especially in QoS, security, and management. Several proposals for QoS, network address translation （NAT）, and interworking have been put forward. In this paper, we propose an integrated architecture for a P2PSIP system as well as a proactive intelligent routing scheme on the media plane used in system. Implementation and simulation show that our solution is suitable for operation and management.

An ALM Model for Streaming Media Service in P2P-SIP Network

Application layer multicast （ALM） has been widely applied in Internet, as a substitute for IP multicast. However, it causes network load to increase because it adopts unlcast in data transmission, which limits the application. In this article, in order to improve the ALM performance in P2P-SIP network, an ALM model was proposed which reduced network load via merging messages in concast mode. Finally network simulations prove that this model has better benefit on single node load and average network load. Therefore, it is suitable for streaming media service in P2P-SIP Network.

Research of Session Initial Protocol Security Mechanism on Public Key Technique

Two common kinds of security mechanisms used in session initial protocol （S1P） are analyzed. An improved HTTP digest authentication scheme is put forward based on the existing SIP authentication theories. This mechanism is combined with the merits of the HTTP digest authentication and the public key encryption, so the communicating parties complete two-way authentication and public key exchange in pre-calling, and the session key can be randomly generated in post-calling. The mixture of security encryption mechanism with public key encryption and symmetric-key encryption algorithm can ensure the security for network communication data. The emulation of the scheme is verified, and the security analysis is conducted in the end. The researches show that the simulations efficiency of this method is about 78% of HTTP＇s, and it can prevent four kinds of attacks including impersonating a server, offline password guessing attacks, relay-attack, and session monitoring.

RESEARCH ON GROUPING STRATEGY OF SIP-BASED STREAMING MEDIA P2P LIVE BROADCAST NETWORK

The rapid development of Internet has led to the explosion of information sharing, and how to supervise the sharing is a main research topic on current Internet. Aiming at the disadvantage that the current Peer-to-Peer (P2P) is hard to manage and control, this paper presents a Session Initial Protocol (SIP)-based P2P network of three-level architecture. SIP middleware is introduced to the middle level of the three-layer architecture. By the connection function of the SIP signaling, the P2P transmission on media-level can be controlled. Using SIP’s register and authentication function, the manage layer can manage the whole P2P network. Based on the aforementioned architecture, this paper investigates the grouping strategy on a live broadcast application in P2P network. Combined with the function of SIP register, the paper works on several grouping strategies, sets up models to manage users by grouping them, presents a weight-based K-means IP address grouping algorithm, and realizes it. The experiment shows that the grouping strategy presented in this paper can solve the problem of group sharing of network resource, and can realize the efficient-sharing, reasonable-distributing of network resource.

A Component-Based Conference Control Model and Implementation for Loosely Coupled Sessions

Conference control is a very important core part to compose a completeInternet multimedia conference system and has been a hot research area over the years, but there arecurrently no -widely accepted robust and scalable solutions and standards. This paper proposes acomponent-based conference control model for loosely coupled sessions in which media applicationscan collaborate with a Session Controller (SC) to provide the conference control. A SC prototype hasbeen built.

SIP Conformance Testing Based on TTCN-2

The session initiation protocol (SIP) is a signaling protocol for Internet telephony, multimedia conferencing, presence, event notification, and instant messaging. With the gaining popularity, more and more SIP implementations have been developed and deployed. How to guarantee the conformance of those SIP implementations is the key point of interconnection and interoperation among them. This paper proposes the test method and architecture for the SIP protocol based on the IPv6 tester system. Tree and tabular combined notation (TTCN-2) is adopted to describe the test suite. With an enhanced reference implementation, the data-processing ability to the original test system has been greatly improved. In the following test practices, some errors have been found in the SIP entities under test. It is proved that the proposed test method and architecture are effective to verify the conformance of the SIP entities, and the result of the conformance test may provide helpful reference to the development of SIP products.