Subject: [tsvwg] New Liaison Statement, "Remove the user message size limitation for DTLS over SCTP"

From: Liaison Statement Management Tool <[email-masked]>
Date: Fri, 05 Mar 2021 10:07:49 -0800

Title: Remove the user message size limitation for DTLS over SCTP
Submission Date: 2021-03-05
URL of the IETF Web page: https://datatracker.ietf.org/liaison/1723/
Please reply by 2021-05-17
From: Nianshan shi <[email-masked]>
To: Gorry Fairhurst <[email-masked]>,David Black <[email-masked]>,Wesley Eddy <[email-masked]>
Cc: Transport Area Working Group Discussion List <[email-masked]>,David Black <[email-masked]>,Wesley Eddy <[email-masked]>,Martin Duke <[email-masked]>,Magnus Westerlund <[email-masked]>,Gorry Fairhurst <[email-masked]>
Response Contacts: Susanna Kooistra <[email-masked]>
Technical Contacts: 
Purpose: For action

Body: 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 SCTP.

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
Attachments:

    R3-211274
    https://www.ietf.org/lib/dt/documents/LIAISON/liaison-2021-03-05-o3gpptsgran3-tsvwg-remove-the-user-message-size-limitation-for-dtls-over-sctp-attachment-1.docx