rfc338.txt:Bob Braden:isi:usa:6:may:1972:17:pdf,postscript,figure:draft-ietf-smtpext-transition:2011-03-10:2009-02-04:165:57:390:154:766:5:2006-08-03:324:draft-marjou-behave-app-rtp-keepalive:2007-06-22:592:2011-06-16:96