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

ITU-T Q3/16 works on support for the TLS and DTLS protocols in decomposed
gateways using ITU-T H.248 as gateway control protocol. Initial support of
these protocols is available, see published Recommendations ITU-T H.248.90
(10/2014) for TLS and ITU-T H.248.93 (10/2014) for DTLS. Initial support means
that the (D)TLS protocols were modelled by so-called H.248 bearer connections
(termed as "TLS bearer session" / "DTLS bearer session" in the
Recommendations). These are abstractions, not necessarily equivalent to real
(D)TLS sessions or (D)TLS connections, but sufficient for basic support by
H.248 gateways.

However, additional support in the area of security and multiplexed protocol
stacks ("WebRTC") imply a more precise model of TLS and DTLS protocol objects.

ITU-T Q3/16 would appreciate if you could provide clarifications particularly
with respect to:

1.      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) 2.      the DTLS association concept, e.g., is it
equivalent to a DTLS session or DTLS connection or something in addition? 3.   
  the TLS renegotiation procedure: what is the definition and at which level
(TLS session or TLS connection level) does this procedure occur? 4.      the
TLS resumption procedure: what is the definition and relation to TLS
renegotiation?

The location of TLS or DTLS endpoints in terminal and gateway equipment is
slightly different due to the decomposition approach of H.248 gateways and
their internal, hierarchical model of H.248 terminations and H.248 stream
endpoints. Support of (D)TLS procedures (beyond the pure establishment and
release) demand for the unambiguous detection of events (such as the
differentiation between TLS renegotiation and TLS resumption from TLS
establishment). As part of the support of (D)TLS endpoints, the H.248 media
gateways are able to determine the TLS profile and protocol capabilities via so
called auditing capabilities procedures. However it is unclear which protocol
capabilities are related to a (D)TLS session and (D)TLS connection and thus the
MGC and MG may have different interpretations. The results of auditing TLS
protocol capabilities and parameter values should be based on a common object
model between the H.248 media gateway and its controller.

ITU-T Q3/16 is appreciative for your cooperation.