UDP Encapsulation of Stream Control Transmission Protocol (SCTP) Packets for End-Host to End-Host Communication
draft-tuexen-tsvwg-rfc6951-bis-03
The information below is for an old version of the document.
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| Authors | Michael Tüxen , Randall R. Stewart | ||
| Last updated | 2023-03-13 | ||
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draft-tuexen-tsvwg-rfc6951-bis-03
Network Working Group M. Tüxen
Internet-Draft Münster Univ. of Appl. Sciences
Obsoletes: 6951 (if approved) R. Stewart
Intended status: Standards Track Netflix, Inc.
Expires: 14 September 2023 13 March 2023
UDP Encapsulation of Stream Control Transmission Protocol (SCTP) Packets
for End-Host to End-Host Communication
draft-tuexen-tsvwg-rfc6951-bis-03
Abstract
This document describes a simple method of encapsulating Stream
Control Transmission Protocol (SCTP) packets into UDP packets and its
limitations. This allows the usage of SCTP in networks with legacy
NATs that do not support SCTP. It can also be used to implement SCTP
on hosts without directly accessing the IP layer, for example,
implementing it as part of the application without requiring special
privileges.
Please note that this document only describes the functionality
needed within an SCTP stack to add on UDP encapsulation, providing
only those mechanisms for two end-hosts to communicate with each
other over UDP ports. In particular, it does not provide mechanisms
to determine whether UDP encapsulation is being used by the peer, nor
the mechanisms for determining which remote UDP port number can be
used. These functions are out of scope for this document.
This document covers only end-hosts and not tunneling (egress or
ingress) endpoints.
Status of This Memo
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 14 September 2023.
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Copyright Notice
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.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Conventions . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Use Cases . . . . . . . . . . . . . . . . . . . . . . . . . . 3
3.1. Portable SCTP Implementations . . . . . . . . . . . . . . 3
3.2. Legacy NAT Traversal . . . . . . . . . . . . . . . . . . 4
4. Unilateral Self-Address Fixing (UNSAF) Considerations . . . . 4
5. SCTP over UDP . . . . . . . . . . . . . . . . . . . . . . . . 4
5.1. Architectural Considerations . . . . . . . . . . . . . . 4
5.2. Packet Format . . . . . . . . . . . . . . . . . . . . . . 5
5.2.1. SCTP/UDP/IPv4 Packet Format . . . . . . . . . . . . . 5
5.2.2. SCTP/UDP/IPv6 Packet Format . . . . . . . . . . . . . 6
5.2.3. A New Error Cause . . . . . . . . . . . . . . . . . . 7
5.3. Sending Packets . . . . . . . . . . . . . . . . . . . . . 7
5.4. Receiving Packets . . . . . . . . . . . . . . . . . . . . 8
5.5. Handling of SCTP Packets Containing an INIT Chunk Matching
an Existing Associations . . . . . . . . . . . . . . . . 8
5.6. Handling of Out of the Blue Packets . . . . . . . . . . . 10
5.7. ICMP Considerations . . . . . . . . . . . . . . . . . . . 10
5.8. Path MTU Considerations . . . . . . . . . . . . . . . . . 11
5.9. Handling of Embedded IP Addresses . . . . . . . . . . . . 11
5.10. Explicit Congestion Notification (ECN) Considerations . . 11
6. Socket API Considerations . . . . . . . . . . . . . . . . . . 11
6.1. Get or Set the Remote UDP Encapsulation Port Number
(SCTP_REMOTE_UDP_ENCAPS_PORT) . . . . . . . . . . . . . . 12
7. Middlebox Considerations . . . . . . . . . . . . . . . . . . 12
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 12
9. Security Considerations . . . . . . . . . . . . . . . . . . . 13
10. References . . . . . . . . . . . . . . . . . . . . . . . . . 13
10.1. Normative References . . . . . . . . . . . . . . . . . . 13
10.2. Informative References . . . . . . . . . . . . . . . . . 14
Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . 15
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 15
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1. Introduction
This document describes a simple method of encapsulating SCTP packets
into UDP packets. SCTP, as defined in [RFC9260], runs directly over
IPv4 or IPv6. There are two main reasons for encapsulating SCTP
packets:
* To allow SCTP traffic to pass through NATs, which do not provide
native SCTP support.
* To allow SCTP to be implemented on hosts that do not provide
direct access to the IP layer. In particular, applications can
use their own SCTP implementation if the operating system does not
provide one.
SCTP provides the necessary congestion control and reliability
service that UDP does not perform.
2. Conventions
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.
3. Use Cases
This section discusses two important use cases for encapsulating SCTP
into UDP.
3.1. Portable SCTP Implementations
Some operating systems support SCTP natively. For other operating
systems, implementations are available but require special privileges
to install and/or use them. In some cases, a kernel implementation
might not be available at all. When providing an SCTP implementation
as part of a user process, most operating systems require special
privileges to access the IP layer directly.
Using UDP encapsulation makes it possible to provide an SCTP
implementation as part of a user process that does not require any
special privileges.
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A crucial point for implementing SCTP in user space is that the
source address of outgoing packets needs to be controlled. This is
not an issue if the SCTP stack can use all addresses configured at
the IP layer as source addresses. However, it is an issue when also
using the address management needed for NAT traversal, described in
Section 5.9.
3.2. Legacy NAT Traversal
Using UDP encapsulation allows SCTP communication when traversing
NATs not supporting SCTP. For single-homed associations, IP
addresses MUST NOT be listed in the INIT and INIT-ACK chunks. To use
multiple addresses, the dynamic address reconfiguration extension
described in [RFC5061] MUST be used only with wildcard addresses in
the ASCONF chunks (Address Configuration Change Chunks) in
combination with [RFC4895].
For multihomed SCTP associations, the address management as described
in Section 5.9 MUST be performed.
SCTP sends periodic HEARTBEAT chunks on all idle paths. These can
keep the NAT state alive.
If multiple SCTP endpoints are operating be a NAT, the local SCTP
port numbers used by the SCTP endpoints MUST all be different.
4. Unilateral Self-Address Fixing (UNSAF) Considerations
As [RFC3424] requires a limited scope, this document only covers SCTP
endpoints dealing with legacy constraints as described in Section 3.
It doesn't cover generic tunneling endpoints.
Obviously, the exit strategy is to use hosts supporting SCTP natively
and middleboxes supporting SCTP.
5. SCTP over UDP
5.1. Architectural Considerations
UDP-encapsulated SCTP is normally communicated between SCTP stacks
using the IANA-assigned UDP port number 9899 (sctp-tunneling) on both
ends. There are circumstances where other ports MAY be used on
either end: As stated earlier, implementations in the application
space might be need to use ports other than the registered port.
Since NAT boxes might change UDP port numbers, the receiver might
observe other UDP port numbers than were used by the sender.
Discovery of alternate ports is outside of the scope of this
document, but this section describes considerations for SCTP stack
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design in light of their potential use.
Each SCTP stack uses a single local UDP encapsulation port number as
the destination port for all its incoming SCTP packets. While the
uniqueness of the local UDP encapsulation port number is not
necessarily needed for the protocol, this greatly simplifies
implementation design, since different ports for each address would
require a sender implementation to choose the appropriate port while
doing source address selection. Using a single local UDP
encapsulation port number per host is not possible if the SCTP stack
is implemented as part of each application, there are multiple
applications, and some of the applications want to use the same IP
address.
An SCTP implementation supporting UDP encapsulation MUST maintain a
remote UDP encapsulation port number per destination address for each
SCTP association. Again, because the remote stack MAY be using ports
other than the well-known port, each port MAY be different from each
stack. However, because of remapping of ports by NATs, the remote
ports associated with different remote IP addresses MAY not be
identical, even if they are associated with the same stack.
Implementation note: Because the well-known port might not be used,
implementations need to allow other port numbers to be specified as a
local or remote UDP encapsulation port number through APIs.
5.2. Packet Format
5.2.1. SCTP/UDP/IPv4 Packet Format
To encapsulate an SCTP packet, a UDP header as defined in [RFC0768]
is inserted between the IP header as defined in [RFC0791] and the
SCTP common header as defined in [RFC9260].
Figure 1 shows the packet format of an encapsulated SCTP packet when
IPv4 is used.
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0 1 2 3
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IPv4 Header |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| UDP Header |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| SCTP Common Header |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| SCTP Chunk #1 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| SCTP Chunk #n |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 1: An SCTP/UDP/IPv4 Packet
5.2.2. SCTP/UDP/IPv6 Packet Format
The packet format for an encapsulated SCTP packet when using IPv6 as
defined in [RFC8200] is shown in Figure 2. Please note that the
number m of IPv6 extension headers can be 0.
0 1 2 3
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IPv6 Base Header |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IPv6 Extension Header #1 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IPv6 Extension Header #m |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| UDP Header |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| SCTP Common Header |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| SCTP Chunk #1 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| SCTP Chunk #n |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 2: An SCTP/UDP/IPv6 Packet
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5.2.3. A New Error Cause
The error cause indicating an "Restart of an Association with New
Encapsulation Port" 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Cause Code = 14 (suggested) | Cause Length = 8 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Current Encapsulation Port | New Encapsulation Port |
+-------------------------------+-------------------------------+
Figure 3: Restart of an Association with New Encapsulation Port
Error Cause
Cause Code: 2 bytes (unsigned integer)
This field holds the IANA defined cause code for the "Restart of
an Association with New Encapsulation Port" error cause. IANA is
requested to assign the value 14 (suggested) for this cause code.
Cause Length: 2 bytes (unsigned integer)
This field holds the length in bytes of the error cause; the value
MUST be 8.
Current Encapsulation Port: 2 bytes (unsigned integer)
This field holds the remote encapsulation port currently being
used for the destination address the received packet containing
the INIT chunk was sent from. If the UDP encapsulation for
destination address is currently disabled, 0 is used.
New Encapsulation Port: 2 bytes (unsigned integer)
If the received SCTP packet containing the INIT chunk is
encapsulated in UDP, this field holds the UDP source port number
of the UDP packet. If the received SCTP packet is not
encapsulated in UDP, this field is 0.
All transported integer numbers are in "network byte order" a.k.a.,
Big Endian.
5.3. Sending Packets
Within the UDP header, the source port MUST be the local UDP
encapsulation port number of the SCTP stack, and the destination port
MUST be the remote UDP encapsulation port number maintained for the
association and the destination address to which the packet is sent
(see Section 5.1).
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Because the SCTP packet is the UDP payload, the length of the UDP
packet MUST be the length of the SCTP packet plus the size of the UDP
header.
The SCTP checksum MUST be computed for IPv4 and IPv6, and the UDP
checksum SHOULD be computed for IPv4 and IPv6. (See [RFC0768]
regarding IPv4; see [RFC8200] and [RFC6936] regarding IPv6.)
Although UDP with a zero checksum over IPv6 is allowed under certain
constraints [RFC6936], this document does not specify mechanisms for
this mode. Deployed support might be limited; also, at the time of
writing, the use of a zero UDP checksum would be counter to the goal
of legacy NAT traversal.
5.4. Receiving Packets
When an encapsulated packet is received, the UDP header is removed.
Then, the generic lookup is performed, as done by an SCTP stack
whenever a packet is received, to find the association for the
received SCTP packet. After finding the SCTP association (which
includes checking the verification tag), the UDP source port MUST be
stored as the encapsulation port for the destination address the SCTP
packet is received from (see Section 5.1).
When a non-encapsulated SCTP packet is received by the SCTP stack,
the encapsulation of outgoing packets belonging to the same
association and the corresponding destination address MUST be
disabled.
If the verification tag can't be checked, the procedures described in
one of the following sections MUST be followed.
5.5. Handling of SCTP Packets Containing an INIT Chunk Matching an
Existing Associations
SCTP packets containing an INIT chunk have the verification tag 0 in
the common header. Therefore the verification tag can't be checked.
The following rules apply when processing the received packet:
1. The remote UDP encapsulation port for the source address of the
received SCTP packet MUST NOT be updated if the encapsulation of
outgoing packets is enabled and the received SCTP packet is
encapsulated.
2. The UDP encapsulation for outgoing packets towards the source
address of the received SCTP packet MUST NOT be enabled, if it is
disabled and the received SCTP packet is encapsulated.
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3. The UDP encapsulation for outgoing packets towards the source
address of the received SCTP packet MUST NOT be disabled, if it
is enabled and the received SCTP packet is not encapsulated.
4. If the UDP encapsulation for outgoing packets towards the source
address of the received SCTP packet is disabled and the received
SCTP packet is encapsulated, an SCTP packet containing an ABORT
chunk MUST be sent. The ABORT chunk MAY include the error cause
defined below indicating an "Restart of an Association with New
Encapsulation Port". This packet containing the ABORT chunk MUST
be encapsulated in UDP. The UDP source port and UDP destination
port used for sending the packet containing the ABORT chunk are
the UDP destination port and UDP source port of the received
packet containing the INIT chunk.
5. If the UDP encapsulation for outgoing packets towards the source
address of the received SCTP packet is disabled and the received
SCTP packet is not encapsulated, the processing defined in
[RFC9260] MUST be performed. If a packet is sent in response, it
MUST NOT be encapsulated.
6. If the UDP encapsulation for outgoing packets towards the source
address of the received SCTP packet is enabled and the received
SCTP packet is not encapsulated, an SCTP packet containing an
ABORT chunk MUST be sent. The ABORT chunk MAY include the error
cause defined in Section 5.2.3 indicating an "Restart of an
Association with New Encapsulation Port". This packet containing
the ABORT chunk MUST NOT be encapsulated in UDP.
7. If the UDP encapsulation for outgoing packets towards the source
address of the received SCTP packet is enabled and the received
SCTP packet is encapsulated, but the UDP source port of the
received SCTP packet is not equal to the remote UDP encapsulation
port for the source address of the received SCTP packet, an SCTP
packet containing an ABORT chunk MUST be sent. The ABORT chunk
MAY include the error cause defined in Section 5.2.3 indicating
an "Restart of an Association with New Encapsulation Port". This
packet containing the ABORT chunk MUST be encapsulated in UDP.
The UDP source port and UDP destination port used for sending the
packet containing the ABORT chunk are the UDP destination port
and UDP source port of the received packet containing the INIT
chunk.
8. If the UDP encapsulation for outgoing packets towards the source
address of the received SCTP packet is enabled and the received
SCTP packet is encapsulated and the UDP source port of the
received SCTP packet is equal to the remote UDP encapsulation
port for the source address of the received SCTP packet, the
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processing defined in [RFC9260] MUST be performed. If a packet
is sent in response, it MUST be encapsulated. The UDP source
port and UDP destination port used for sending the packet
containing the ABORT chunk are the UDP destination port and UDP
source port of the received packet containing the INIT chunk.
5.6. Handling of Out of the Blue Packets
If the processing of an out of the blue packet requires the sending
of a packet in response according to the rules specified in
Section 8.4 of [RFC9260], the following rules apply:
1. If the received packet was encapsulated in UDP, the response
packets MUST also be encapsulated in UDP. The UDP source port
and UDP destination port used for sending the response packet are
the UDP destination port and UDP source port of the received
packet.
2. If the received packet was not encapsulated in UDP, the response
packet MUST NOT be encapsulated in UDP.
Please note that in these cases a check of the verification tag is
not possible.
5.7. ICMP Considerations
When receiving ICMP or ICMPv6 response packets, there might not be
enough bytes in the payload to identify the SCTP association that the
SCTP packet triggering the ICMP or ICMPv6 packet belongs to. If a
received ICMP or ICMPv6 packet cannot be related to a specific SCTP
association or the verification tag cannot be verified, it MUST be
discarded silently. In particular, this means that the SCTP stack
MUST NOT rely on receiving ICMP or ICMPv6 messages. Implementation
constraints could prevent processing received ICMP or ICMPv6
messages.
If received ICMP or ICMPv6 messages are processed, the following
mapping SHOULD apply:
1. ICMP messages with type 'Destination Unreachable' and code 'Port
Unreachable' SHOULD be treated as ICMP messages with type
'Destination Unreachable' and code 'Protocol Unreachable'. See
[RFC0792] for more details.
2. ICMPv6 messages with type 'Destination Unreachable' and code
'Port Unreachable' SHOULD be treated as ICMPv6 messages with type
'Parameter Problem' and code 'unrecognized Next Header type
encountered'. See [RFC4443] for more details.
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5.8. Path MTU Considerations
If an SCTP endpoint starts to encapsulate the packets of a path, it
MUST decrease the Path MTU of that path by the size of the UDP
header. If it stops encapsulating them, the Path MTU SHOULD be
increased by the size of the UDP header.
Since one cannot rely on the feedback provided by ICMP or ICMPv6 due
to the limitation laid out in Section 5.7, [RFC8899] MUST be
followed, when performing Path MTU discovery.
If the implementation does not allow control of the Don't Fragment
(DF) bit contained in the IPv4 header, then Path MTU discovery can't
be used. In this case, an implementation-specific value SHOULD be
used instead.
5.9. Handling of Embedded IP Addresses
When using UDP encapsulation for legacy NAT traversal, IP addresses
that might require translation MUST NOT be put into any SCTP packet.
This means that a multihomed SCTP association is set up initially as
a single-homed one, and the protocol extension [RFC5061] in
combination with [RFC4895] is used to add the other addresses. Only
wildcard addresses are put into the SCTP packet.
When addresses are changed during the lifetime of an association, the
protocol extension [RFC5061] MUST be used with wildcard addresses
only. If an SCTP endpoint receives an ABORT with the T-bit set, it
MAY use this as an indication that the addresses seen by the peer
might have changed.
5.10. Explicit Congestion Notification (ECN) Considerations
If the implementation supports the sending and receiving of the ECN
bits for the IP protocols being used by an SCTP association, the ECN
bits MUST NOT be changed during sending and receiving.
6. Socket API Considerations
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 socket option.
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6.1. Get or Set the Remote UDP Encapsulation Port Number
(SCTP_REMOTE_UDP_ENCAPS_PORT)
This socket option can be used to set and retrieve the UDP
encapsulation port number. This allows an endpoint to encapsulate
initial packets.
struct sctp_udpencaps {
sctp_assoc_t sue_assoc_id;
struct sockaddr_storage sue_address;
uint16_t sue_port;
};
sue_assoc_id:
This parameter is ignored for one-to-one style sockets. For one-
to-many style sockets, the application might fill in an
association identifier or SCTP_FUTURE_ASSOC for this query. It is
an error to use SCTP_{CURRENT|ALL}_ASSOC in sue_assoc_id.
sue_address:
This specifies which address is of interest. If a wildcard
address is provided, it applies only to future paths.
sue_port:
The UDP port number in network byte order; used as the destination
port number for UDP encapsulation. Providing a value of 0
disables UDP encapsulation.
7. Middlebox Considerations
Middleboxes often use different timeouts for UDP based flows than for
other flows. Therefore the HEARTBEAT.Interval parameter SHOULD be
lowered to 15 seconds when UDP encapsulation is used.
8. IANA Considerations
[NOTE to RFC-Editor: "RFCXXXX" is to be replaced by the RFC number
you assign this document.]
[NOTE to RFC-Editor: The requested values for the cause code are
tentative and to be confirmed by IANA.]
A new error cause code has to be assigned by IANA. This requires an
additional line in the "Error Cause Codes" registry for SCTP:
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+================+=============================+===========+
| Value | Cause Code | Reference |
+================+=============================+===========+
| 14 (suggested) | Restart of an Association | [RFCXXXX] |
| | with New Encapsulation Port | |
+----------------+-----------------------------+-----------+
Table 1: New Entry in Error Cause Codes Registry
This document refers to the already assigned UDP port 9899 (sctp-
tunneling). IANA is requested to update this assignment to refer to
[RFCXXXX]. As per [RFC6335], the Assignee is [IESG] and the Contact
is [IETF_Chair].
9. Security Considerations
Encapsulating SCTP into UDP does not add any additional security
considerations to the ones given in [RFC9260] and [RFC5061].
Firewalls inspecting SCTP packets need also to be aware of the
encapsulation and apply corresponding rules to the encapsulated
packets.
An attacker might send a malicious UDP packet towards an SCTP
endpoint to change the encapsulation port for a single remote address
of a particular SCTP association. However, as specified in
Section 5.4, this requires the usage of one of the two negotiated
verification tags. This protects against blind attackers the same
way as described in [RFC9260] for SCTP over IPv4 or IPv6. Non-blind
attackers can affect SCTP association using the UDP encapsulation
described in this document in the same way as SCTP associations not
using the UDP encapsulation of SCTP described here.
10. References
10.1. Normative References
[RFC0768] Postel, J., "User Datagram Protocol", STD 6, RFC 768,
DOI 10.17487/RFC0768, August 1980,
<https://www.rfc-editor.org/info/rfc768>.
[RFC0791] Postel, J., "Internet Protocol", STD 5, RFC 791,
DOI 10.17487/RFC0791, September 1981,
<https://www.rfc-editor.org/info/rfc791>.
[RFC0792] Postel, J., "Internet Control Message Protocol", STD 5,
RFC 792, DOI 10.17487/RFC0792, September 1981,
<https://www.rfc-editor.org/info/rfc792>.
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[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>.
[RFC4443] Conta, A., Deering, S., and M. Gupta, Ed., "Internet
Control Message Protocol (ICMPv6) for the Internet
Protocol Version 6 (IPv6) Specification", STD 89,
RFC 4443, DOI 10.17487/RFC4443, March 2006,
<https://www.rfc-editor.org/info/rfc4443>.
[RFC4895] Tuexen, M., Stewart, R., Lei, P., and E. Rescorla,
"Authenticated Chunks for the Stream Control Transmission
Protocol (SCTP)", RFC 4895, DOI 10.17487/RFC4895, August
2007, <https://www.rfc-editor.org/info/rfc4895>.
[RFC5061] Stewart, R., Xie, Q., Tuexen, M., Maruyama, S., and M.
Kozuka, "Stream Control Transmission Protocol (SCTP)
Dynamic Address Reconfiguration", RFC 5061,
DOI 10.17487/RFC5061, September 2007,
<https://www.rfc-editor.org/info/rfc5061>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>.
[RFC8200] Deering, S. and R. Hinden, "Internet Protocol, Version 6
(IPv6) Specification", STD 86, RFC 8200,
DOI 10.17487/RFC8200, July 2017,
<https://www.rfc-editor.org/info/rfc8200>.
[RFC8899] Fairhurst, G., Jones, T., Tüxen, M., Rüngeler, I., and T.
Völker, "Packetization Layer Path MTU Discovery for
Datagram Transports", RFC 8899, DOI 10.17487/RFC8899,
September 2020, <https://www.rfc-editor.org/info/rfc8899>.
[RFC9260] Stewart, R., Tüxen, M., and K. Nielsen, "Stream Control
Transmission Protocol", RFC 9260, DOI 10.17487/RFC9260,
June 2022, <https://www.rfc-editor.org/info/rfc9260>.
10.2. Informative References
[RFC3424] Daigle, L., Ed. and IAB, "IAB Considerations for
UNilateral Self-Address Fixing (UNSAF) Across Network
Address Translation", RFC 3424, DOI 10.17487/RFC3424,
November 2002, <https://www.rfc-editor.org/info/rfc3424>.
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[RFC6335] Cotton, M., Eggert, L., Touch, J., Westerlund, M., and S.
Cheshire, "Internet Assigned Numbers Authority (IANA)
Procedures for the Management of the Service Name and
Transport Protocol Port Number Registry", BCP 165,
RFC 6335, DOI 10.17487/RFC6335, August 2011,
<https://www.rfc-editor.org/info/rfc6335>.
[RFC6458] Stewart, R., Tuexen, M., Poon, K., Lei, P., and V.
Yasevich, "Sockets API Extensions for the Stream Control
Transmission Protocol (SCTP)", RFC 6458,
DOI 10.17487/RFC6458, December 2011,
<https://www.rfc-editor.org/info/rfc6458>.
[RFC6936] Fairhurst, G. and M. Westerlund, "Applicability Statement
for the Use of IPv6 UDP Datagrams with Zero Checksums",
RFC 6936, DOI 10.17487/RFC6936, April 2013,
<https://www.rfc-editor.org/info/rfc6936>.
[RFC6951] Tuexen, M. and R. Stewart, "UDP Encapsulation of Stream
Control Transmission Protocol (SCTP) Packets for End-Host
to End-Host Communication", RFC 6951,
DOI 10.17487/RFC6951, May 2013,
<https://www.rfc-editor.org/info/rfc6951>.
Acknowledgments
The authors wish to thank Stewart Bryant, Dave Crocker, Gorry
Fairhurst, Tero Kivinen, Barry Leiba, Pete Resnick, Martin
Stiemerling, Irene Rüngeler, and Dan Wing for their invaluable
comments on [RFC6951].
The authors wish to thank Georgios Papastergiou for the initial
problem report resulting in the work on this document and Irene
Rüngeler and Felix Weinrank for their invaluable comments on this
document.
Part of this work has received funding from the European Union's
Horizon 2020 research and innovation programme under grant agreement
No. 644334 (NEAT). The views expressed are solely those of the
author(s).
Authors' Addresses
Michael Tüxen
Münster University of Applied Sciences
Stegerwaldstrasse 39
48565 Steinfurt
Germany
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Email: tuexen@fh-muenster.de
Randall R. Stewart
Netflix, Inc.
15214 Pendio Drive
Bella Collina, FL 34756
United States of America
Email: randall@lakerest.net
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