RFC 9260

Q: What does the Introduction section cover in RFC 9260 — SCTP?

The Introduction section provides detailed technical specifications, security considerations, and implementation guidance as documented in RFC 9260 — SCTP. This content is part of the BLACKLABS RFC Reference Library.

Q: What does the Key Features for 3GPP section cover in RFC 9260 — SCTP?

The Key Features for 3GPP section provides detailed technical specifications, security considerations, and implementation guidance as documented in RFC 9260 — SCTP. This content is part of the BLACKLABS RFC Reference Library.

Q: What does the Association Setup section cover in RFC 9260 — SCTP?

The Association Setup section provides detailed technical specifications, security considerations, and implementation guidance as documented in RFC 9260 — SCTP. This content is part of the BLACKLABS RFC Reference Library.

Q: What does the 3GPP Interface Mapping section cover in RFC 9260 — SCTP?

The 3GPP Interface Mapping section provides detailed technical specifications, security considerations, and implementation guidance as documented in RFC 9260 — SCTP. This content is part of the BLACKLABS RFC Reference Library.

Q: What does the Security Considerations section cover in RFC 9260 — SCTP?

The Security Considerations section provides detailed technical specifications, security considerations, and implementation guidance as documented in RFC 9260 — SCTP. This content is part of the BLACKLABS RFC Reference Library.

BLACKLABS

Stream Control Transmission Protocol

Standards Track Obsoletes: RFC 4960

June 2022

Abstract: SCTP is a reliable transport protocol that supports multi-homing and multi-streaming. In 3GPP, SCTP is the transport for Diameter signaling (S6a, Gx, Gy), S1AP/NGAP interfaces, and X2AP/Xn interfaces.

Canonical source: https://www.rfc-editor.org/rfc/rfc9260 | IETF Datatracker

1. Introduction

▶

SCTP provides reliable, message-oriented transport with support for multi-homing (multiple IP addresses per endpoint) and multi-streaming (multiple independent message streams within an association). It was originally designed for signaling transport (SIGTRAN) and is widely used in telecom.

In 3GPP, SCTP carries Diameter messages (AAA signaling), NGAP (5G NR control plane between gNB and AMF), S1AP (LTE control plane), and X2AP/XnAP (inter-base-station handover signaling).

2. Key Features for 3GPP

▶

Feature	Description	3GPP Benefit
Multi-homing	Multiple IP addresses per endpoint	Network resilience — automatic failover between paths
Multi-streaming	Independent ordered streams within association	No head-of-line blocking across streams
Message boundaries	Preserves application message boundaries	Diameter message framing without length headers
4-way handshake	INIT → INIT-ACK → COOKIE-ECHO → COOKIE-ACK	DoS protection via stateless cookies
Heartbeat	PATH MTU discovery and path monitoring	Detect path failures for multi-homed endpoints
Ordered/unordered delivery	Per-stream ordering control	Flexibility for different message priorities

3. Association Setup

▶

The 4-way handshake protects against SYN flood attacks — the server does not allocate state until the COOKIE-ECHO is received with a valid cookie.

  Client (gNB)                       Server (AMF)
|                                  |
|  INIT                            |
|  [Initiate Tag, A-RWND,          |
|   Number of Outbound Streams,    |
|   Number of Inbound Streams,     |
|   Initial TSN]                   |
|--------------------------------->|
|                                  |
|          INIT-ACK                |
|          [Initiate Tag, A-RWND,  |
|           State Cookie,          |
|           Supported Extensions]  |
|<---------------------------------|
|                                  |
|  COOKIE-ECHO                     |
|  [State Cookie]                  |
|--------------------------------->|
|                                  |
|          COOKIE-ACK              |
|<---------------------------------|
|                                  |
|  [SCTP Association Established]  |

4. 3GPP Interface Mapping

▶

Interface	Application Protocol	Transport	Network Segment
NG-C (N2)	NGAP	SCTP	gNB ↔ AMF
Xn-C	XnAP	SCTP	gNB ↔ gNB
S6a/S6d	Diameter	SCTP	MME ↔ HSS
Gx	Diameter	SCTP	PCEF ↔ PCRF
S1-MME	S1AP	SCTP	eNB ↔ MME
X2-C	X2AP	SCTP	eNB ↔ eNB

5. Security Considerations

▶

SCTP itself provides no encryption — relies on IPsec (RFC 4301) or DTLS (RFC 6083) for security
The cookie mechanism in INIT protects against blind connection flooding
SCTP multi-homing improves availability but increases attack surface — all addresses must be secured
Implementations must handle ABORT chunks carefully to prevent association hijacking