| Stream Control Transmission Protocol (SCTP) is the third general-purpose transport protocol developed by the IETF after TCP and UDP. The original design purpose of SCTP was to transmit SS7 messages of PSTN over IP based network. During the course of design, many new features were added into the original framework and finally SCTP was designed to be a general-purpose transport protocol. SCTP is a reliable, connection oriented and message oriented transport protocol. Term"association"in SCTP is used to represent the connection between two SCTP endpoints. SCTP supports transport-level multi-homing. One SCTP endpoint can have multiple IP addresses. SCTP supports multi-streaming. There can be multiple unidirectional ordered message sequence in one association and the ordering of each sequence is independent. SCTP is message oriented and data are always processed in form of messages. SCTP supports ordered or unordered message delivery. SCTP is stronger to resist SYN flooding attack than TCP.P2P file sharing technique is totally different from network file service based on Client/Server mode. Nodes in P2P network can exchange files directly without through file servers. Each node is a downloader and an uploader at the same time. Message is the information exchange format adopted generally in all kinds of P2P file sharing systems. Between node and node, and between node and centralized index server, messages are used to carry information which accomplishes control functionalities of resource searching and locating. Some P2P system, such as eDonkey, eMule and BitTorrent,take the strategy of downloading from multiple peers simultaneity to... |
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