RFC 6083

Datagram Transport Layer Security (DTLS) for Stream Control Transmission Protocol (SCTP)
Standards Track
January 2011
RFC Library > SCTP > RFC 6083
Abstract: This document defines the usage of DTLS over SCTP, providing mutual authentication, confidentiality, and integrity protection for SCTP associations. It is an alternative to IPsec for securing Diameter and other SCTP-based signaling in 3GPP networks.
Canonical source: https://www.rfc-editor.org/rfc/rfc6083  |  IETF Datatracker

1. Introduction

▶

DTLS for SCTP provides an alternative to IPsec for securing SCTP-based signaling. It operates above SCTP, providing per-association security with mutual certificate authentication.

In 3GPP, this is an option for securing Diameter interfaces (S6a, Gx) when hop-by-hop IPsec is not deployed. The SCTP association carries DTLS records, which in turn carry the application protocol (Diameter).

2. Architecture

▶

DTLS-over-SCTP places the security layer between SCTP and the application, while IPsec places it below SCTP. Each approach has tradeoffs.

  ┌─────────────────────┐
│   Diameter / NGAP   │  Application
├─────────────────────┤
│        DTLS          │  Security
├─────────────────────┤
│        SCTP          │  Transport
├─────────────────────┤
│         IP           │  Network
└─────────────────────┘
vs. IPsec approach:
┌─────────────────────┐
│   Diameter / NGAP   │  Application
├─────────────────────┤
│        SCTP          │  Transport
├─────────────────────┤
│     ESP (IPsec)      │  Security
├─────────────────────┤
│         IP           │  Network
└─────────────────────┘

3. DTLS-SCTP vs IPsec

▶
Feature DTLS for SCTP IPsec
Granularity Per-association Per-IP-pair or subnet
Certificate auth Native (DTLS handshake) Via IKEv2
Multi-homing Handled by SCTP (below DTLS) Requires SA per address pair
Deployment Application-layer, easier in cloud Kernel-level, complex in containers
Performance User-space overhead Kernel-accelerated
3GPP preference Alternative option Primary (TS 33.210)

4. Security Considerations

▶
  • DTLS handshake must complete before application data is exchanged on the association
  • Renegotiation support allows periodic rekeying without association restart
  • SCTP multi-homing address changes are transparent to DTLS — DTLS sees a reliable stream
  • Both IPsec and DTLS can be used simultaneously for defense-in-depth (rare in practice)