| Internet-Draft | INIT forwarding for SCTP | October 2023 |
| Tüxen & Völker | Expires 10 April 2024 | [Page] |
The Stream Control Transmission Protocol (SCTP) extension described in this document allows the support of a simple mechanism to distribute association requests between a cluster of SCTP end points providing the same service. In particular, this allows the use of anycast addresses in combination with SCTP.¶
This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79.¶
Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet-Drafts is at https://datatracker.ietf.org/drafts/current/.¶
Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress."¶
This Internet-Draft will expire on 10 April 2024.¶
Copyright (c) 2023 IETF Trust and the persons identified as the document authors. All rights reserved.¶
This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (https://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Revised BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Revised BSD License.¶
The protocol extension described in this document allows an initiation of an SCTP association to deal with an address change of the peer during the handshake. The extension enables the peer to respond from another address than the one used as destination address in the received packet containing the INIT chunk. The SCTP Dynamic Address Reconfiguration extension described in [RFC5061] can not be used, since it does not apply to the handshake.¶
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all capitals, as shown here.¶
The INIT Forwarding Chunk Parameter is defined by the following figure.¶
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type = 0x8006 | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ \ \ / Parameter / \ \ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
This field holds the IANA defined parameter type for the "INIT Forwarding" chunk parameter. IANA is requested to assign the value 32774 (0x8006) for this parameter type.¶
This field holds the length in bytes of the chunk parameter; the value MUST be the length of the parameter included plus 4.¶
The parameter MUST be one of:¶
All transported integer numbers are in "network byte order" a.k.a., Big Endian.¶
The INIT Forwarding Chunk Parameter MAY appear in INIT and INIT ACK chunks and MUST NOT appear in any other chunk. If an INIT or INIT ACK chunk contains an INIT Forwarding Chunk Parameter, the INIT Forwarding Chunk Parameter MUST be the first optional/variable-length parameter.¶
If an end point not supporting the extension described in this document receives this parameter in an INIT or INIT ACK chunk, it skips this parameter and continues to process further parameters in the chunk. This behaviour is REQUIRED by [RFC9260] because the highest-order 2 bits of the Type are 10.¶
If an end point that sends an SCTP packet containing an INIT chunk wants to allow the peer to respond from an address different from the destination address of the packet, MUST use the INIT Forwarding Chunk parameter as the first optional/variable-length parameter. The parameter in the INIT Forwarding Chunk parameter MUST be a Padding parameter. If the SCTP packet containing the INIT chunk is sent over IPV4, the length of the padding parameter MUST be the length of an IPv4 Address parameter, which is 8 bytes. Otherwise, if the SCTP packet containing the INIT chunk is sent over IPV6, the length of the padding parameter MUST be the length of an IPv6 Address parameter, which is 20 bytes.¶
If a middlebox receives an SCTP packet containing an INIT chunk with INIT Forwarding Chunk parameter as its first optional/variable-length parameter and wants to change the destination address of the packet, it MUST replace the Padding parameter in the INIT Forwarding Chunk parameter with an IPv4 or IPv6 Address parameter containing the original destination address of the SCTP packet containing the INIT chunk. If the INIT Forwarding Chunk parameter does not contain a Padding parameter, but an IPv4 or IPv6 Address parameter, the INIT Forwarding Chunk parameter MUST NOT be modified at all.¶
If an end point receives an SCTP packet containing an INIT chunk and the INIT chunk contains an INIT Forwarding Chunk parameter including an Address parameter as its first optional/variable-length parameter, the end point MUST include this INIT Forwarding Chunk parameter as the first optional/variable-length parameter in the INIT ACK chunk, which is sent in response. If the INIT Forwarding Chunk parameter contains a Padding parameter and the end-point does not want to use the destination address, it MUST put an INIT Forwarding Chunk parameter containing this address in the INIT ACK chunk sent in response. If the end point wants to use the destination address in the association and the INIT Forwarding Chunk parameter contains a Padding parameter, the INIT Forwarding Chunk parameter MUST NOT be included in the INIT ACK chunk.¶
If an end point receives an SCTP packet containing an INIT ACK chunk and it cannot find the association for this packet using the IP addresses and port numbers, and the INIT ACK chunk contains an INIT Forwarding Chunk parameter as its first optional/variable-length parameter, it SHOULD use the IP address contained in the Address parameter of the INIT Forwarding Chunk parameter instead of the source address of the received packet for the association lookup. If an association is then found, the address in the INIT Forwarding Chunk parameter MUST be removed as a remote address and the source address of the packet containing the INIT ACK chunk MUST be added as an unconfirmed remote address.¶
This section describes how the socket API defined in [RFC6458] needs to be extended to provide a way for the application to control the UDP encapsulation.¶
Please note that this section is informational only.¶
A socket API implementation based on [RFC6458] is extended by supporting one new read/write IPPROTO_SCTP level socket option.¶
This socket option can be used to control the support of INIT forwarding. It applies only to future SCTP associations on the socket.¶
This option expects an integer boolean flag, where a non-zero value turns on the option, and a zero value turns off the option.¶
This option is off by default.¶
[NOTE to RFC-Editor: "RFCXXXX" is to be replaced by the RFC number you assign this document.]¶
[NOTE to RFC-Editor: The requested value for the parameter type is tentative and to be confirmed by IANA.]¶
This document (RFCXXXX) is the reference for the registration described in this section.¶
A new chunk parameter type has to be assigned by IANA. This requires an additional line in the "Chunk Parameter Types" registry for SCTP:¶
| ID Value | Chunk Parameter Type | Reference |
|---|---|---|
| 32774 | INIT Forwarding (0x8006) | [RFCXXXX] |
This document does not change the considerations given in [RFC9260].¶