Liaison statement
Remove the user message size limitation for DTLS over SCTP

State Posted
Submitted Date 2021-03-05
From Contact Nianshan shi
To Group tsvwg
To Contacts Gorry Fairhurst
David Black
Wesley Eddy
CcTransport Area Working Group Discussion List
David Black
Wesley Eddy
Martin Duke
Magnus Westerlund
Gorry Fairhurst
Response Contact Susanna Kooistra
Purpose For action
Deadline 2021-05-17 Action Needed
Attachments R3-211274
1. Overall Description:
From the first version of the 5G specification, 3GPP has specified to use DTLS
over SCTP. RAN3 has found an issue related to RFC 6083 DTLS user message size
limitation over SCTP that impacts several of 3GPP RAN application protocols.
The RFC specifies a user message limit of approximate16k Bytes. This should be
compared to the unlimited user message size that exists when SCTP is used
without DTLS.

There are several RAN application messages that can exceed the limit of
approximate 16k Bytes. The same issue may exist for the other 3GPP groups using
the DTLS over SCTP.

A general solution to this issue is desirable rather than changing multiple
different protocols. We understand the limitation in RFC 6083 is due to a lack
of a secure fragmentation mechanism of user messages into multiple DTLS
records. The DTLS over SCTP specification appear to be the right layer to
resolve this issue and achieve feature parity between DTLS over SCTP and
unsecured SCTP.

RAN3 would like to ask the IETF TSVWG to investigate and would greatly
appreciate a solution to the issue related to the size limitation for DTLS over

2. Actions:
To IETF TSVWG group.
ACTION: RAN3 kindly asks IETF TSVWG to investigate the possibility to remove
the size limitation issue in DTLS over SCTP and provide feedback to RAN3.

3. Date of Next RAN3 Meetings:
RAN3#112-e      17th – 28th May 2021 Online