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Session Control Protocol

Session Control Protocol definition

Many internet applications (FTP, GOPHER, and HTTP) establish a new Transmission Control Protocol connection for each transaction. This approach is not very efficient since it requires initiating a connection for every request. That’s even when multiple requests are sent to the same server.

The Session Control Protocol (SCP) addresses this inefficiency. It allows multiple exchanges to occur over a single TCP connection.

See also: gopher protocol, TCP handshake

Protocol Operations:

  • Session ID Allocation: Each session is assigned a unique identifier. IDs below 1024 are reserved, with client-allocated IDs being even and server-allocated IDs being odd.
  • Session Establishment: A session starts by sending a message with the SYN bit set on that channel.
  • Graceful Release: Sessions are closed by sending a message with the FIN bit. Connections can be ended independently at each end.
  • Disgraceful Release: A session can be abruptly terminated using a message with the RST bit. All pending data for that session is discarded.
  • Message Boundaries: These are defined by sending a message with the PUSH bit set, with the boundary including the final octet of this message.