My application has to talk to different hosts over https, and the default setting of ServicePointManager.SecurityProtocol = TLS served me well up to this day. Now I have some hosts which (as System.Net trace log shows) don't answer the initial TLS handshake message but keep the underlying connection open until it times out, throwing a timeout exception. I tried setting HttpWebRequest's timeout to as much as 5mins, with the same result. Presumably these hosts are waiting for an SSL3 handshake since both IE and Firefox are able to connect to these hosts after a 30-40 seconds' delay. There seems to be some fallback mechanism in .NET which degrades TLS to SSL3, but it doesn't kick in for some reason.

FWIW, here's the handshake message my request is sending:

00000000 : 16 03 01 00 57 01 00 00-53 03 01 4C 12 39 B4 F9 : ....W...S..L.9..
00000010 : A3 2C 3D EE E1 2A 7A 3E-D2 D6 0D 2E A9 A8 6C 03 : .,=..*z>......l.
00000020 : E7 8F A3 43 0A 73 9C CE-D7 EE CF 00 00 18 00 2F : ...C.s........./
00000030 : 00 35 00 05 00 0A C0 09-C0 0A C0 13 C0 14 00 32 : .5.............2
00000040 : 00 38 00 13 00 04 01 00-00 12 00 0A 00 08 00 06 : .8..............
00000050 : 00 17 00 18 00 19 00 0B-00 02 01 00             : ............    

Is there a way to use SSL3 instead of TLS in a particular HttpWebRequest, or force a fallback? It seems that ServicePointManager's setting is global, and I'd really hate to have to degrade the security protocol setting to SSL3 for the whole application.