China 
Africa 
Explore chapters and articles related to this topic
Interworking Services in SIP
Published in Radhika Ranjan Roy, Handbook on Session Initiation Protocol, 2018
It turns out that SIP, being an upper application-layer protocol, needs to be NAT-aware, that is, a lower-layer (layer 3 or 4) device, in order to cross NATs. That is, enhancements in NAT functionalities need to be made like a gateway that is aware of the network layer to the SIP application layer as if acting as a SIP B2BUA. Session Traversal of UDP through NAT (STUN) (RFC 5389), Traversal Using Relays around NAT (TURN) (RFC 5766), and Interactive Connectivity Establishment (ICE) (RFC 5245) protocols have been developed to cross the NATs by SIP so that, first, the session is established and then the media is transferred between the conferencing end points. Each of these NAT-crossing protocols has its own pros, cons, and particular usages depending on different network settings. We will only discuss some basic features of NAT crossing.
Negotiations Model in SDP
Published in Radhika Ranjan Roy, Handbook of SDP for Multimedia Session Negotiations, 2018
This section describes the SDP offer/answer model for network address translator (NAT) traversal for User Datagram Protocol (UDP)-based multimedia sessions (RFC 5245). Note that NATs are troublesome devices in network paths that not only hamper multimedia session negotiations; they are also vulnerable for security attacks. The NAT crossing for multimedia sessions is so complicated, in fact, RFC 5245 has used Interactive Connectivity Establishment (ICE) protocol. It uses traversal using relays around NAT (TURN) and simple traversal of UDP around NAT (STUN) and its extensions for crossing NATs by UDP-based multimedia sessions that are established with the SDP offer/answer model.
Comparison of QoS optimisation techniques in adaptive smart device peer-to-peer overlay networks
Published in International Journal of Parallel, Emergent and Distributed Systems, 2021
Ananda Maiti, Andrew Maxwell, Alexander Kist
NDCs are used to create Content delivery networks. For content delivery, a number of replication servers can be installed in geographically diverse locations to minimize latency with respect to geographical location [14]. NDCs allow saving considerable energy, still maintaining required scalability. Such systems are more spread apart geographically than conventional data centers and are often larger in numbers to make up for their lower performance. In the context of establishing an end-to-end connection between users, NDCs may play a role in relaying data as well as in addressing communication issues such as firewalls. Traversal Using Relays around NAT (TURN) [15] protocol uses this principle to operate. A significant impact of protocols like Interactive Connectivity Establishment [16] (ICE), STUN, and TURN protocols on delays in operation of Peer-to-Peer Session Initiation Protocol is presented in [17]. These factors further necessitate correct positioning of the relay NDC servers. The following sections describes several ways to choose the optimal positions of the nodes in the network architecture.