OID value: 1.3.6.1.2.1.6.12
OID description:
tcpRetransSegs OBJECT-TYPE
              SYNTAX  Counter
              ACCESS  read-only
              STATUS  mandatory
              DESCRIPTION
                      "The total number of segments retransmitted - that
                      is, the number of TCP segments transmitted
                      containing one or more previously transmitted
                      octets."
              ::= { tcp 12 }
See also the OID Repository website reference for 1.3.6.1.2.1.6.12