What is SST (Structured Steam Transport)?

Structured stream transport is an experimental transport protocol that is similar to TCP (Transmission control protocol) that provides an organized, reliable byte-stream abstraction. SST enhances the traditional stream abstraction hierarchical hereditary structure, which allows applications to create lightweight child streams from any existing stream. Datagrams that support small transactions and streams are best suited for long-running conversations but neither of two support applications like HTTP(HyperText Transfer Protocol) which is a mixture of transaction sizes and applications or multiple transport instances(like FTP). TCP streams support 3-way hand-shaking delays on startup whereas Time-Wait streams in SST offer independent data transfer and flow control. All streams share one congestion control context.

SST Protocol Architecture:

1. The channel protocol provides sequencing, connection security, and congestion control.
2. The negotiation protocol provides mechanical of establishing channels between hosts, including symmetric key agreement for channel security and negotiating optional protocol extension.
3. The registration protocol provides support for a simple, optional host registration and lookup service. Secure host identification and NAT(Network Access Transaction) traversal.
4. The stream protocol is a convenient, high stream abstraction based on the above three protocols to implement the SST application.

SST Protocol Architecture

Features of SST:

1. Over a single SST session, multiple independent streams can run in parallel.
2. Relative priority between streams to apply application-specific policies.
3. It provides wire efficiency, including header overhead of SST, UDP encapsulation is only 4 bytes larger than TCP.
4. It provides built-in communication security.
5. It provides efficient support for the short use of reliable steams.
6. Streams can be arbitrarily long-running and may preserve internal application-specific record marks.
7. Hole punching support for transparent communication across most NATs and Firewalls.