TLS Fallback Signaling Cipher Suite Value (SCSV) is defined in RFC 7507
and provides for a work around interoperability problems with legacy servers, many TLS user-agent
implementations do not rely on the TLS
protocol version negotiation mechanism alone but will intentionally reconnect using a downgraded protocol if initial handshake attempts fail. Such user-agent
s may fall back to connections in which they announce a version as low as TLS 1.0
(or even its predecessor, Secure Socket Layer (SSL) 3.0) as the highest supported version.
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