Distributed Broker-Agent Architecture for Multimedia Communications Traversing NAT／Firewall in NGN

The forthcoming Next Generation Network (NGN) is an all IP network. Multimedia communications over IP networks are a type of bundled session communications, which cannot directly traverse Network Address Translations (NATs) and firewalls even in NGN. To solve the problem that the existing traversal methods are not suitable for service providers to set up a real system in NGN,a Distributed Broker-agent Architecture (DBA) is addressed. DBA is secure and realizable for service providers and enterprises because it is easy to set up and does not need to upgrade the existing devices like Firewalls, NATs or endpoint devices of subscribers.DBA is composed of two-layer distributed agents, the server proxies and the client agents, in which all multimedia communications use shared tunnels to carry signaling messages and media data between broker-agents, and the call signaling is encrypted over Security Socket Layer (SSL) to guarantee the security of calling. Moreover, the function model and multiplexed connection messages format of DBA are designed, which lays a basis for the protocol in the future NGN. In addition, a simple implementation based on H.323 verifyies the main function of traversing firewalls and NATs.     

艇内多媒体通信加密实现及安全性分析

艇内多媒体通信的安全对于现代战争非常重要,因此多媒体通信的加密操作是解决通信安全、可靠的关键问题之一。本文将DES加密应用到艇内多媒体通信加密中,阐述安全技术的实现,最后从初始化密值、加密密钥及会话密钥3个方面进行安全性分析。     

多媒体通信及其技术基础

多媒体通信具有集成性、交互性、同步性、分布性、实时性五个特点。多媒体的关键技术有：（1）对网络环境的要求，主要是要有较高的带宽和传输速度。（2）数据压缩技术。可以大大降低数据量，降低多媒体网络对带宽、传输速率的要求，数据压缩的总目标是减小数据中的冗余度，减小容纳给定消息集合的信号空间。评价压缩的标准有信息压缩比、压缩速度和重现精度。（3）同步技术的缓冲法、反馈法、时间戳法。（4）多媒体数据库的特点和基本要求，（5）多媒体终端，包括软件系统和硬件系统的任务和特点，多媒体通信向着宽代化、综合化、智能化、数字化、个人化发展。     

多媒体通信系统在智能交通中的应用

智能交通系统是集通信技术和交通运输为一体的新型的交通系统.文章主要叙述了智能交通领域中的多媒体及网络通信技术:无线通信技术、视频技术、ATM技术等,并且给出了多媒体通信系统在智能交通中应用的实例.