Liaison statement
Response to LS on TLS and DTLS terminology [to 3GPPA SA3, IETF WG TLS, 3GPP CT4]

State Posted
Posted Date 2015-02-02
From Group tls
From Contact Sean Turner
To Group ITU-T-SG-16-Q3
To Contacts Rosa De Vivero
CcJoseph Salowey
Stephen Farrell
Kathleen Moriarty
Transport Layer Security Discussion List
Scott mansfield
Response Contact Christian Groves
Purpose In response
Attachments (None)
Liaisons referred by this one LS on TLS and DTLS terminology [to 3GPPA SA3, IETF WG TLS, 3GPP CT4]
Thanks for your questions about (D)TLS.  What follows is a response to your questions; questions proceeded by Q# and answers by A#.  If you have additional question please let us know.


[What is] the distinction between (D)TLS session and (D)TLS connection (which implies a definition for each term, beyond the available descriptions / glossary from RFC side)


A TLS session is shared cryptographic state established by a full TLS handshake between two peers.  The session’s cryptographic state is used to establish the cryptographic key material for a TLS connection.  A TLS connection is a transport relationship established between two peers that contains the cryptographic state to cryptographically protect data sent and received on the connection established through a full or abbreviated (session resumption) TLS handshake.  A TLS session may span one or more TLS connections.  Every TLS connection is associated with one TLS session.  If session resumption (abbreviated handshake) is not used then the TLS session and TLS connection will essentially be the same.  A TLS session is identified by a Session ID in the client and server hellos.  A TLS connection is usually identified by a host addresses and port numbers.


The DTLS association concept, e.g., is it equivalent to a DTLS session or DTLS connection or something in addition?


The DTLS association is the same as a DTLS connection


The TLS renegotiation procedure: what is the definition and at which level (TLS session or TLS connection level) does this procedure occur?


The TLS resumption procedure: what is the definition and relation to TLS renegotiation?

A3 and A4:

Resumption refers to the use of the state from an existing TLS session to establish a new TLS connection using an abbreviated handshake.  During resumption the cryptographic parameters (algorithms etc.) remain the same.  TLS renegotiation is the process of executing a new TLS handshake to establish new cryptographic parameters for a TLS connection (effectively a new TLS connection using the same host addresses and ports as the previous one). If the handshake is a full handshake then both a new session and a new connection are established and the renegotiated session may have different parameters.

Please note that session resumption and renegotiation are optional features; though TLS 1.2 recommended support for renegotiation; renegotiation was also updated by RFC 5746.  Please note that TLS 1.3 is currently under development and these features are being reviewed.