1.        Introduction                                             3
1.1.      Requirements Terminology                                 4
2.        Usage Model                                              4
3.        Overview of DTLS                                         5
3.1.      Loss-Insensitive Messaging                               5
3.2.      Providing Reliability for Handshake                      5
3.2.1.    Packet Loss                                              6
3.2.2.    Reordering                                               6
3.2.3.    Message Size                                             7
3.3.      Replay Detection                                         7
4.        Differences from TLS                                     7
4.1.      Record Layer                                             7
4.1.1.    Transport Layer Mapping                                  9
4.1.1.1.  PMTU Issues                                              10
4.1.2.    Record Payload Protection                                12
4.1.2.1.  MAC                                                      12
4.1.2.2.  Null or Standard Stream Cipher                           12
4.1.2.3.  Block Cipher                                             12
4.1.2.3.  AEAD Ciphers                                             13
4.1.2.5.  New Cipher Suites                                        13
4.1.2.6.  Anti-replay                                              13
4.1.2.7.  Handling Invalid Records                                 14
4.2.      The DTLS Handshake Protocol                              14
4.2.1.    Denial of Service Countermeasures                        14
4.2.2.    Handshake Message Format                                 17
4.2.3.    Handshake Message Fragmentation and Reassembly           19
4.2.4.    Timeout and Retransmission                               19
4.2.4.1.  Timer Values                                             24
4.2.5.    ChangeCipherSpec                                         24
4.2.6.    CertificateVerify and Finished Messages                  25
4.2.7.    Alert Messages                                           25
4.2.8.    Establishing New Associations With Existing Parameters   25
4.3.      Summary of new syntax                                    26
4.3.1.    Record Layer                                             27
4.3.2.    Handshake Protocol                                       27
5.        Security Considerations                                  28
6.        Acknowledgements                                         30
7.        IANA Considerations                                      30
8.        Changes Since DTLS 1.0                                   30
9.        References                                               31
9.1.      Normative References                                     31
9.2.      Informative References                                   32