Here's output from Wireshark:
1) TLS v1.0, server raises Unsupported Extension (110) alert:
TLSv1 Record Layer: Handshake Protocol: Client Hello
Content Type: Handshake (22)
Version: TLS 1.0 (0x0301)
Length: 78
Handshake Protocol: Client Hello
Handshake Type: Client Hello (1)
Length: 74
Version: TLS 1.0 (0x0301)
Random
Session ID Length: 0
Cipher Suites Length: 8
Cipher Suites (4 suites)
Cipher Suite: TLS_DHE_RSA_WITH_AES_256_CBC_SHA (0x0039)
Cipher Suite: TLS_DHE_RSA_WITH_AES_128_CBC_SHA (0x0033)
Cipher Suite: TLS_RSA_WITH_AES_128_CBC_SHA (0x002f)
Cipher Suite: TLS_EMPTY_RENEGOTIATION_INFO_SCSV (0x00ff)
Compression Methods Length: 1
Compression Methods (1 method)
Compression Method: null (0)
Extensions Length: 25
Extension: server_name
Type: server_name (0x0000)
Length: 21
Server Name Indication extension
Server Name list length: 19
Server Name Type: host_name (0)
Server Name length: 16
Server Name: www.google.co.uk
TLSv1 Record Layer: Handshake Protocol: Server Hello
Content Type: Handshake (22)
Version: TLS 1.0 (0x0301)
Length: 85
Handshake Protocol: Server Hello
Handshake Type: Server Hello (2)
Length: 81
Version: TLS 1.0 (0x0301)
Random
Session ID Length: 32
Session ID: 56b1b6faae75e76baecb8a5727480a2b7687315baaeceb06...
Cipher Suite: TLS_RSA_WITH_AES_128_CBC_SHA (0x002f)
Compression Method: null (0)
Extensions Length: 9
Extension: renegotiation_info
Type: renegotiation_info (0xff01)
Length: 1
Renegotiation Info extension
Extension: server_name
Type: server_name (0x0000)
Length: 0
TLSv1 Record Layer: Handshake Protocol: Server Hello Done
Content Type: Handshake (22)
Version: TLS 1.0 (0x0301)
Length: 4
Handshake Protocol: Server Hello Done
Handshake Type: Server Hello Done (14)
Length: 0
TLSv1 Record Layer: Alert (Level: Fatal, Description: Unsupported Extension)
Content Type: Alert (21)
Version: TLS 1.0 (0x0301)
Length: 2
Alert Message
Level: Fatal (2)
Description: Unsupported Extension (110)
2) TLS v1.2 works fine, as expected:
TLSv1.2 Record Layer: Handshake Protocol: Client Hello
Content Type: Handshake (22)
Version: TLS 1.2 (0x0303)
Length: 78
Handshake Protocol: Client Hello
Handshake Type: Client Hello (1)
Length: 74
Version: TLS 1.2 (0x0303)
Random
Session ID Length: 0
Cipher Suites Length: 8
Cipher Suites (4 suites)
Cipher Suite: TLS_DHE_RSA_WITH_AES_256_CBC_SHA (0x0039)
Cipher Suite: TLS_DHE_RSA_WITH_AES_128_CBC_SHA (0x0033)
Cipher Suite: TLS_RSA_WITH_AES_128_CBC_SHA (0x002f)
Cipher Suite: TLS_EMPTY_RENEGOTIATION_INFO_SCSV (0x00ff)
Compression Methods Length: 1
Compression Methods (1 method)
Compression Method: null (0)
Extensions Length: 25
Extension: server_name
Type: server_name (0x0000)
Length: 21
Server Name Indication extension
Server Name list length: 19
Server Name Type: host_name (0)
Server Name length: 16
Server Name: www.google.co.uk
TLSv1.2 Record Layer: Handshake Protocol: Server Hello
Content Type: Handshake (22)
Version: TLS 1.2 (0x0303)
Length: 85
Handshake Protocol: Server Hello
Handshake Type: Server Hello (2)
Length: 81
Version: TLS 1.2 (0x0303)
Random
Session ID Length: 32
Session ID: c702788e7eaea1da30876968caedd785819c304da7e08bde...
Cipher Suite: TLS_RSA_WITH_AES_128_CBC_SHA (0x002f)
Compression Method: null (0)
Extensions Length: 9
Extension: renegotiation_info
Type: renegotiation_info (0xff01)
Length: 1
Renegotiation Info extension
Extension: server_name
Type: server_name (0x0000)
Length: 0
TLSv1.2 Record Layer: Handshake Protocol: Server Hello Done
Content Type: Handshake (22)
Version: TLS 1.2 (0x0303)
Length: 4
Handshake Protocol: Server Hello Done
Handshake Type: Server Hello Done (14)
Length: 0
TLSv1.2 Record Layer: Handshake Protocol: Client Key Exchange
Content Type: Handshake (22)
Version: TLS 1.2 (0x0303)
Length: 262
Handshake Protocol: Client Key Exchange
Handshake Type: Client Key Exchange (16)
Length: 258
RSA Encrypted PreMaster Secret
and then it proceeds to finish handshake successfully.
I'm aware that SNI was introduced later than TLS v.1.0 RFC, but from what I read it shouldn't stop SNI from working on v1.0?
[before anyone suggests just updating to TLS v1.2 - would gladly do that, but constrained by space/memory on older clients atm. For reference, this is .NET compact Framework client running on Windows CE.]
