Network Working Group R. Stewart
Internet-Draft Huawei
Intended status: Standards Track P. Lei
Expires: June 2, 2011 Cisco Systems, Inc.
M. Tuexen
Muenster Univ. of Applied Sciences
November 29, 2010
Stream Control Transmission Protocol (SCTP) Stream Reconfiguration
draft-ietf-tsvwg-sctp-strrst-08.txt
Abstract
Many applications that use SCTP want the ability to "reset" a stream.
The intention of resetting a stream is to set the numbering sequence
of the stream back to 'zero' with a corresponding notification to the
upper layer that this has been performed. The applications that want
this feature want it so that they can "re-use" streams for different
purposes but still utilize the stream sequence number so that the
application can track the message flows. Thus, without this feature,
a new use of an old stream would result in message numbers greater
than expected unless there is a protocol mechanism to "reset the
streams back to zero". This document also includes methods for
resetting the transport sequence numbers, adding additional streams
and resetting all stream sequence numbers.
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 http://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 June 2, 2011.
Copyright Notice
Copyright (c) 2010 IETF Trust and the persons identified as the
document authors. All rights reserved.
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This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(http://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 Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
2. Conventions . . . . . . . . . . . . . . . . . . . . . . . . . 4
3. New Chunk Type . . . . . . . . . . . . . . . . . . . . . . . . 4
3.1. STREAM RESET Chunk . . . . . . . . . . . . . . . . . . . . 5
4. New Parameter Types . . . . . . . . . . . . . . . . . . . . . 6
4.1. Outgoing SSN Reset Request Parameter . . . . . . . . . . . 6
4.2. Incoming SSN Reset Request Parameter . . . . . . . . . . . 8
4.3. SSN/TSN Reset Request Parameter . . . . . . . . . . . . . 9
4.4. Stream Reset Response Parameter . . . . . . . . . . . . . 9
4.5. Add Outgoing Streams Request Parameter . . . . . . . . . . 11
5. Procedures . . . . . . . . . . . . . . . . . . . . . . . . . . 12
5.1. Sender Side Procedures . . . . . . . . . . . . . . . . . . 12
5.1.1. Sender Side Procedures for the Stream Reset Chunk . . 12
5.1.2. Sender Side Procedures for the Outgoing SSN Reset
Request Parameter . . . . . . . . . . . . . . . . . . 13
5.1.3. Sender Side Procedures for the Incoming SSN Reset
Request Parameter . . . . . . . . . . . . . . . . . . 14
5.1.4. Sender Side Procedures for the SSN/TSN Reset
Request Parameter . . . . . . . . . . . . . . . . . . 14
5.1.5. Sender Side Procedures for the Stream Reset
Response Parameter . . . . . . . . . . . . . . . . . . 15
5.1.6. Sender Side Procedures for the Add Outgoing
Streams Request Parameter . . . . . . . . . . . . . . 16
5.2. Receiver Side Procedures . . . . . . . . . . . . . . . . . 16
5.2.1. Receiver Side Procedures for the Stream Reset Chunk . 16
5.2.2. Receiver Side Procedures for the Outgoing SSN
Reset Request Parameter . . . . . . . . . . . . . . . 16
5.2.3. Receiver Side Procedures for the Incoming SSN
Reset Request Parameter . . . . . . . . . . . . . . . 17
5.2.4. Receiver Side Procedures for the SSN/TSN Reset
Request Parameter . . . . . . . . . . . . . . . . . . 18
5.2.5. Receiver Side Procedures for the Add Outgoing
Streams Request Parameter . . . . . . . . . . . . . . 19
5.2.6. Receiver Side Procedures for the Stream Reset
Response Parameter . . . . . . . . . . . . . . . . . . 19
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6. Socket API Considerations . . . . . . . . . . . . . . . . . . 20
6.1. Events . . . . . . . . . . . . . . . . . . . . . . . . . . 20
6.1.1. Stream Reset Event . . . . . . . . . . . . . . . . . . 21
6.1.2. Association Reset Event . . . . . . . . . . . . . . . 22
6.1.3. Stream Change Event . . . . . . . . . . . . . . . . . 23
6.2. Event Subscription . . . . . . . . . . . . . . . . . . . . 24
6.3. Socket Options . . . . . . . . . . . . . . . . . . . . . . 25
6.3.1. Enable/Disable Stream Reset
(SCTP_ENABLE_STREAM_RESET) . . . . . . . . . . . . . . 25
6.3.2. Reset Incoming and/or Outgoing Streams
(SCTP_RESET_STREAMS) . . . . . . . . . . . . . . . . . 26
6.3.3. Reset SSN/TSN (SCTP_RESET_ASSOC) . . . . . . . . . . . 27
6.3.4. Add Outgoing Streams (SCTP_ADD_OUT_STREAMS) . . . . . 27
7. Security Considerations . . . . . . . . . . . . . . . . . . . 27
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 28
8.1. A New Chunk Type . . . . . . . . . . . . . . . . . . . . . 28
8.2. Five New Parameter Types . . . . . . . . . . . . . . . . . 29
9. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 29
Appendix A. Examples of the Stream Reset procedures . . . . . . . 29
10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 30
10.1. Normative References . . . . . . . . . . . . . . . . . . . 30
10.2. Informative References . . . . . . . . . . . . . . . . . . 31
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 31
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1. Introduction
Many applications that use SCTP want the ability to "reset" a stream.
The intention of resetting a stream is to set the numbering sequence
of the stream back to 'zero' with a corresponding notification to the
upper layer that this has been performed. The applications that want
this feature want to "re-use" streams for different purposes but
still utilize the stream sequence number so that the application can
track the message flows. Thus, without this feature, a new use of an
old stream would result in message numbers greater than expected
unless there is a protocol mechanism to "reset the streams back to
zero". This document also includes methods for resetting the
transport sequence numbers, adding additional streams and resetting
all stream sequence numbers.
The socket API for SCTP defined in [I-D.ietf-tsvwg-sctpsocket]
exposes the sequence numbers used by SCTP for user message transfer.
Therefore, resetting them can be used by application writers. Please
note that the corresponding sequence number for TCP is not exposed
via the socket API for TCP.
2. Conventions
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119].
3. New Chunk Type
This section defines the new chunk type that will be used to reset
streams. Table 1 illustrates the new chunk type.
+------------+-----------------------------------+
| Chunk Type | Chunk Name |
+------------+-----------------------------------+
| 0x82 | Stream Reset Chunk (STREAM_RESET) |
+------------+-----------------------------------+
Table 1
It should be noted that the format of the STREAM_RESET chunk requires
the receiver to ignore the chunk if it is not understood and continue
processing all chunks that follow. This is accomplished by the use
of the upper bits of the chunk type as described in section 3.2 of
[RFC4960].
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All transported integer numbers are in "network byte order" a.k.a.,
Big Endian.
3.1. STREAM RESET Chunk
This document adds one new chunk type to SCTP. The chunk has the
following format:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type = 0x82 | Chunk Flags | Chunk Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Stream Reset Parameter |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Stream Reset Parameter (optional) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Chunk Type: 1 byte (unsigned integer)
This field holds the IANA defined chunk type for the STREAM RESET
chunk. The suggested value of this field for IANA is 0x82.
Chunk Flags: 1 byte (unsigned integer)
This field is set to 0 by the sender and ignored by the receiver.
Chunk Length: 2 bytes (unsigned integer)
This field holds the length of the chunk in bytes, including the
Chunk Type, Chunk Flags and Chunk Length.
Stream Reset Parameter
This field holds a Stream Reset Request Parameter or a Stream
Reset Response Parameter.
Note that each STREAM RESET chunk holds at least one parameter and at
most two parameters. Only the following combinations are allowed:
1. Outgoing SSN Reset Request Parameter.
2. Incoming SSN Reset Request Parameter.
3. Outgoing SSN Reset Request Parameter, Incoming SSN Reset Request
Parameter.
4. SSN/TSN Reset Request Parameter.
5. Add Outgoing Streams Request Parameter.
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6. Stream Reset Response Parameter.
7. Stream Reset Response Parameter, Outgoing SSN Reset Request
Parameter.
8. Stream Reset Response Parameter, Stream Reset Response Parameter.
If a sender transmits an unsupported combination, the receiver SHOULD
send an ERROR chunk with a Protocol Violation cause as defined in
section 3.3.10.13 of [RFC4960]).
4. New Parameter Types
This section defines the new parameter types that will be used in the
STREAM_RESET chunk. Table 2 illustrates the new parameter types.
+----------------+----------------------------------------+
| Parameter Type | Parameter Name |
+----------------+----------------------------------------+
| 0x000d | Outgoing SSN Reset Request Parameter |
| 0x000e | Incoming SSN Reset Request Parameter |
| 0x000f | SSN/TSN Reset Request Parameter |
| 0x0010 | Stream Reset Response Parameter |
| 0x0011 | Add Outgoing Streams Request Parameter |
+----------------+----------------------------------------+
Table 2
It should be noted that the parameter format requires the receiver to
stop processing the parameter and not to process any further
parameters within the chunk if the parameter type is not recognized.
This is accomplished by the use of the upper bits of the parameter
type as described in section 3.2.1 of [RFC4960].
All transported integer numbers are in "network byte order" a.k.a.,
Big Endian.
4.1. Outgoing SSN Reset Request Parameter
This parameter is used by the sender to request the reset of some or
all outgoing streams.
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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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Parameter Type = 0x000d | Parameter Length = 16 + 2 * N |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Stream Reset Request Sequence Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Stream Reset Response Sequence Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sender's Last Assigned TSN |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Stream Number 1 (optional) | Stream Number 2 (optional) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
/ ...... /
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Stream Number N-1 (optional) | Stream Number N (optional) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Parameter Type: 2 bytes (unsigned integer)
This field holds the IANA defined parameter type for Stream Reset
Request Parameter. The suggested value of this field for IANA is
0x000d.
Parameter Length: 2 bytes (unsigned integer)
This field holds the length in bytes of the parameter; the value
MUST be 16 + 2 * N.
Stream Reset Request Sequence Number: 4 bytes (unsigned integer)
This field is used to identify the request. It is a monotonically
increasing number that is initialized to the same value as the
Initial TSN number. It is increased by 1 whenever sending a new
Stream Reset Request parameter.
Stream Reset Response Sequence Number: 4 bytes (unsigned integer)
When this Outgoing SSN Reset Request Parameter is sent in response
to an Incoming SSN Reset Request Parameter this parameter is also
an implicit response to the incoming request. Then this field
holds the Stream Reset Request Sequence Number of the incoming
request. In other cases it holds the next expected Stream Reset
Request Sequence Number minus 1.
Sender's last assigned TSN: 4 bytes (unsigned integer)
This value holds the next TSN minus 1, in other words the last TSN
that this sender assigned.
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Stream Number 1..N: 2 bytes (unsigned integer)
This optional field, if included, is used to indicate specific
streams that are to be reset. If no streams are listed, then all
streams are to be reset.
This parameter can appear in a STREAM RESET chunk. This parameter
MUST NOT appear in any other chunk type.
4.2. Incoming SSN Reset Request Parameter
This parameter is used by the sender to request that the peer resets
some or all of its outgoing streams.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Parameter Type = 0x000e | Parameter Length = 8 + 2 * N |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Stream Reset Request Sequence Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Stream Number 1 (optional) | Stream Number 2 (optional) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
/ ...... /
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Stream Number N-1 (optional) | Stream Number N (optional) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Parameter Type: 2 bytes (unsigned integer)
This field holds the IANA defined parameter type for Stream Reset
Request Parameter. The suggested value of this field for IANA is
0x000e.
Parameter Length: 2 bytes (unsigned integer)
This field holds the length in bytes of the parameter; the value
MUST be 8 + 2 * N.
Stream Reset Request Sequence Number: 4 bytes (unsigned integer)
This field is used to identify the request. It is a monotonically
increasing number that is initialized to the same value as the
Initial TSN number. It is increased by 1 whenever sending a new
Stream Reset Request parameter.
Stream Number 1..N: 2 bytes (unsigned integer)
This optional field, if included, is used to indicate specific
streams that are to be reset. If no streams are listed, then all
streams are to be reset.
This parameter can appear in a STREAM RESET chunk. This parameter
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MUST NOT appear in any other chunk type.
4.3. SSN/TSN Reset Request Parameter
This parameter is used by the sender to request a reset of the TSN
and SSN numbering of all streams.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Parameter Type = 0x000f | Parameter Length = 8 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Stream Reset Request Sequence Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Parameter Type: 2 bytes (unsigned integer)
This field holds the IANA defined parameter type for Stream Reset
Request Parameter. The suggested value of this field for IANA is
0x000f.
Parameter Length: 2 bytes (unsigned integer)
This field holds the length in bytes of the parameter; the value
MUST be 8.
Stream Reset Request Sequence Number: 4 bytes (unsigned integer)
This field is used to identify the request. It is a monotonically
increasing number that is initialized to the same value as the
Initial TSN number. It is increased by 1 whenever sending a new
Stream Reset Request parameter.
This parameter can appear in a STREAM RESET chunk. This parameter
MUST NOT appear in any other chunk type.
4.4. Stream Reset Response Parameter
This parameter is used by the receiver of a stream reset request
parameter to respond to the stream reset request.
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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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Parameter Type = 0x0010 | Parameter Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Stream Reset Response Sequence Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Result |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sender's next TSN (optional) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Receiver's next TSN (optional) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Parameter Type: 2 bytes (unsigned integer)
This field holds the IANA defined parameter type for Stream Reset
Response Parameter. The suggested value of this field for IANA is
0x0010.
Parameter Type Length: 2 bytes (unsigned integer)
This field holds the length in bytes of the parameter; the value
MUST be 12 if the optional fields are not present and 20
otherwise.
Stream Reset Response Sequence Number: 4 bytes (unsigned integer)
This value is copied from the request parameter and is used by the
receiver of the Stream Reset Response Parameter to tie the
response to the request.
Result: 4 bytes (unsigned integer)
This value describes the result of the processing of the request.
It is encoded as given by the following table
+--------+-------------------------------------+
| Result | Description |
+--------+-------------------------------------+
| 0 | Success - Nothing to do |
| 1 | Success - Performed |
| 2 | Denied |
| 3 | Error - Wrong SSN |
| 4 | Error - Request already in progress |
| 5 | Error - Bad Sequence Number |
| 6 | In progress |
+--------+-------------------------------------+
Table 3
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Sender's next TSN: 4 bytes (unsigned integer)
This field holds the TSN the sender of the Response will use to
send the next DATA chunk. The field is only applicable in
responses to SSN/TSN reset requests.
Receiver's next TSN: 4 bytes (unsigned integer)
This field holds the TSN the receiver of the response must use to
send the next DATA chunk. The field is only applicable in
responses to SSN/TSN reset requests.
Either both optional fields (Sender's next TSN and Receiver's next
TSN) MUST be present or none.
This parameter can appear in a STREAM RESET chunk. This parameter
MUST NOT appear in any other chunk type.
4.5. Add Outgoing Streams Request Parameter
This parameter is used by the sender to request that an additional
number of outgoing streams (i.e. the receiver's incoming streams) be
added to the association.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Parameter Type = 0x0011 | Parameter Length = 12 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Stream Reset Request Sequence Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Number of new streams | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Parameter Type: 2 bytes (unsigned integer)
This field holds the IANA defined parameter type for the Add
Streams Parameter. The suggested value of this field for IANA is
0x0011.
Parameter Length: 2 bytes (unsigned integer)
This field holds the length in bytes of the parameter; the value
MUST be 12.
Stream Reset Request Sequence Number: 4 bytes (unsigned integer)
This field is used to identify the request. It is a monotonically
increasing number that is initialized to the same value as the
Initial TSN number. It is increased by 1 whenever sending a new
Stream Reset Request parameter.
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Number of new streams: 2 bytes (unsigned integer)
This value holds the number of additional outgoing streams the
sender requests to be added to the association. Streams are added
in order and are consecutive, e.g. if an association has four
outgoing streams (0-3) and a requested is made to add 3 streams
then the new streams will be 4, 5 and 6.
Reserved: 2 bytes (unsigned integer)
This field is reserved. It SHOULD be set to 0 by the sender and
ignored by the receiver.
This parameter MAY appear in a STREAM RESET chunk. This parameter
MUST NOT appear in any other chunk type.
5. Procedures
This section defines the procedures used by both the sender and
receiver of a stream reset. We also give various example stream
reset scenarios.
5.1. Sender Side Procedures
This section describes the procedures related to the sending of
Stream Reset Chunks. A Stream Reset Chunk is composed of one or two
Type Length Value (TLV) parameters.
5.1.1. Sender Side Procedures for the Stream Reset Chunk
This SCTP extension uses the Supported Extensions Parameter defined
in [RFC5061] for negotiating the support for it.
An SCTP endpoint supporting this extension MUST include the chunk
type of the STREAM_RESET chunk in the Supported Extensions Parameter
in either the INIT or INIT-ACK. Before sending a Stream Reset Chunk
the sender MUST ensure that the peer advertised support for the
stream reset extension. If the chunk type of the STREAM_RESET chunk
does not appear in the supported extensions list of chunks, then the
sender MUST NOT send any stream reset request to the peer, and any
request by the application for such service SHOULD be responded to
with an appropriate error indicating the peer SCTP stack does not
support the stream reset extension.
After packaging the Stream Reset Chunk and sending it to the peer the
sender MUST start a 'Stream Reset Timer' if the STREAM RESET chunk
contains at least one request parameter. If it contains no request
parameter, the Stream Reset Timer MUST NOT be started. This timer
MUST use the same value as SCTP's Data transmission timer (i.e. the
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RTO timer) and MUST use exponential backoff doubling the value at
every expiration. If the timer expires, besides doubling the value,
the sender MUST retransmit the Stream Reset Chunk, increment the
appropriate error counts (both for the association and the
destination), and perform threshold management possibly destroying
the association if SCTP retransmission thresholds are exceeded.
5.1.2. Sender Side Procedures for the Outgoing SSN Reset Request
Parameter
When an SCTP sender wants to reset the SSNs of some or all outgoing
streams it can send an Outgoing SSN Reset Request Parameter provided
that the Stream Reset Timer is not running. The following steps must
be followed:
A1: The sender MUST stop assigning new SSNs to new user data
provided by the upper layer for the affected streams and queue
it. This is because it is not known whether the receiver of the
request will accept or deny it and moreover, a lost request
might cause an out-of-sequence error in a stream that the
receiver is not yet prepared to handle.
A2: The sender MUST assign the next stream reset request sequence
number and MUST put it into the Stream Reset Request Sequence
Number field of the Outgoing SSN Reset Request Parameter. The
next stream reset request sequence number MUST then be
incremented by 1.
A3: The Sender's Last Assigned TSN MUST be set to the next TSN the
sender assigns minus 1.
A4: If this Outgoing SSN Reset Request Parameter is sent in response
to an Incoming SSN Reset Request Parameter the Stream Numbers
MUST be copied from the Incoming SSN Reset Request Parameter to
the Outgoing SSN Reset Request Parameter. The Stream Reset
Response Sequence Number of the Outgoing SSN Reset Request
Parameter MUST be the Stream Reset Request Sequence Number of
the Incoming SSN Reset Request Parameter. If this Outgoing SSN
Reset Request Parameter is sent at the request of the upper
layer and the sender requests all outgoing streams to be reset
Stream Numbers SHOULD NOT be put into the Outgoing SSN Reset
Request Parameter. If the sender requests only some outgoing
streams to be reset these Stream Numbers MUST be placed in the
Outgoing SSN Reset Request Parameter. Stream Reset Response
Sequence Number is the next expected Stream Reset Request
Sequence Number of the peer minus 1.
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A5: The Outgoing SSN Reset Request Parameter MUST be put into a
STREAM RESET Chunk. The Outgoing SSN Reset Request Parameter
MAY be put together with either an Incoming SSN Reset Request
Parameter or an Stream Reset Response Parameter but not both.
It MUST NOT be put together with any other parameter as
described in Section 3.1.
A6: The STREAM RESET Chunk MUST be sent following the rules given in
Section 5.1.1.
5.1.3. Sender Side Procedures for the Incoming SSN Reset Request
Parameter
When an SCTP sender wants to reset the SSNs of some or all incoming
streams it can send an Incoming SSN Reset Request Parameter provided
that the Stream Reset Timer is not running. The following steps must
be followed:
B1: The sender MUST assign the next stream reset request sequence
number and MUST put it into the Stream Reset Request Sequence
Number field of the Incoming SSN Reset Request Parameter. After
assigning it the next stream reset request sequence number MUST
be incremented by 1.
B2: If the sender wants all incoming streams to be reset no Stream
Numbers SHOULD be put into the Incoming SSN Reset Request
Parameter. If the sender wants only some incoming streams to be
reset these Stream Numbers MUST be filled in the Incoming SSN
Reset Request Parameter.
B3: The Incoming SSN Reset Request Parameter MUST be put into a
STREAM RESET Chunk. It MAY be put together with an Outgoing SSN
Reset Request Parameter but MUST NOT be put together with any
other parameter.
B4: The STREAM RESET Chunk MUST be sent following the rules given in
Section 5.1.1.
When sending a Incoming SSN Reset Request their is a potential that
the peer has just reset or is in the process of resetting the same
streams via an Outgoing SSN Reset Request. This collision scenario
is discussed in Section 5.2.3.
5.1.4. Sender Side Procedures for the SSN/TSN Reset Request Parameter
When an SCTP sender wants to reset the SSNs and TSNs it can send an
SSN/TSN Reset Request Parameter provided that the Stream Reset Timer
is not running. The following steps must be followed:
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C1: The sender MUST assign the next stream reset request sequence
number and put it into the Stream Reset Request Sequence Number
field of the SSN/TSN Reset Request Parameter. After assigning
it the next stream reset request sequence number MUST be
incremented by 1.
C2: The sender MUST queue any user data suspending any new
transmissions and TSN assignment until the reset procedure is
finished by the peer either acknowledging or denying the
request.
C3: The SSN/TSN Reset Request Parameter MUST be put into a STREAM
RESET Chunk. There MUST NOT be any other parameter in this
chunk.
C4: The STREAM RESET Chunk MUST be sent following the rules given in
Section 5.1.1.
Only one SSN/TSN Reset Request SHOULD be sent within 30 seconds,
which is considered a maximum segment lifetime, the IP MSL.
5.1.5. Sender Side Procedures for the Stream Reset Response Parameter
When an implementation receives a reset request parameter it must
respond with a Stream Reset Response Parameter in the following
manner:
D1: The Stream Reset Request Sequence number of the incoming request
MUST be copied to the Stream Reset Response Sequence Number
field of the Stream Reset Response Parameter.
D2: The result of the processing of the incoming request according
to Table 3 MUST be placed in the Result field of the Stream
Reset Response Parameter.
D3: If the incoming request is an SSN/TSN reset request, the
Sender's next TSN field MUST be filled with the next TSN the
sender of this Stream Reset Response Parameter will assign. For
other requests the Sender's next TSN field, which is optional,
MUST NOT be used.
D4: If the incoming request is an SSN/TSN reset request, the
Receiver's next TSN field MUST be filled with a TSN such that
the sender of the Stream Reset Response Parameter can be sure it
can discard received DATA chunks with smaller TSNs. The value
SHOULD be the smallest TSN not acknowledged by the receiver of
the request plus 2^31. For other requests the Receiver's next
TSN field, which is optional, MUST NOT be used.
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5.1.6. Sender Side Procedures for the Add Outgoing Streams Request
Parameter
When an SCTP sender wants to increase the number of outbound streams
to which it is able to send, it may add an Add Outgoing Streams
Request parameter to the STREAM RESET chunk. Upon sending the
request the sender MUST await a positive acknowledgment (Success)
before using any additional stream added by this request. Note that
new streams are added adjacent to the previous streams with no gaps.
This means that if a request is made to add 2 streams to an
association that has already 5 (0-4) then the new streams, upon
successful completion, are streams 5 and 6. A new stream MUST use
the stream sequence number 0 for its first ordered message.
5.2. Receiver Side Procedures
5.2.1. Receiver Side Procedures for the Stream Reset Chunk
Upon reception of a Stream Reset Chunk each parameter within it
SHOULD be processed. If multiple parameters have to be returned,
they MUST be put into one STREAM RESET chunk. If the received STREAM
RESET chunk contains at least one request parameter, a SACK chunk
SHOULD be sent back and MAY be bundled with the STREAM RESET chunk.
If the received STREAM RESET chunk contains at least one request and
based on the analysis of the Stream Reset Request Sequence Numbers
this is the last received STREAM RESET chunk (i.e. a retransmission),
the same STREAM RESET chunk MUST to be sent back in response as was
earlier.
The decision to deny a stream reset request is an administrative
decision and may be user configurable even after the association has
formed. If for whatever reason the endpoint does not wish to process
a received request parameter it MUST send a corresponding response
parameter as described in Section 5.1.5 with an appropriate Result
field.
Implementation Note: A SACK is recommended to be bundled with any
stream reset response so that any retransmission processing that
needs to occur can be expedited. A SACK chunk is not required for
this feature to work, but it will in effect help minimize the delay
in completing a stream reset operation in the face of any data loss.
5.2.2. Receiver Side Procedures for the Outgoing SSN Reset Request
Parameter
In the case that the endpoint is willing to perform a stream reset
the following steps must be followed:
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E1: If the Stream Reset Timer is running for the Stream Reset
Request Sequence Number indicated in the Stream Reset Response
Sequence Number field, the Stream Reset Request Sequence Number
MUST be marked as acknowledged. If all Stream Reset Request
Sequence Numbers the Stream Reset Timer is running for are
acknowledged, the Stream Reset Timer MUST be stopped.
E2: If the Sender's Last Assigned TSN number is greater than the
cumulative acknowledgment point, then the endpoint MUST enter
"deferred reset processing". In this mode, any data arriving
with a TSN number larger than the 'senders last assigned TSN'
for the affected stream(s) MUST be queued locally and held until
the Cumulative Acknowledgment point reaches the 'senders last
assigned TSN number'. When the Cumulative Acknowledgment point
reaches the last assigned TSN number then proceed to the next
step. If the endpoint enters "deferred reset processing", it
MUST put a Stream Reset Response Parameter into a STREAM RESET
chunk indicating 'In progress' and MUST send the STREAM RESET
chunk.
E3: If no Stream Numbers are listed in the parameter, then all
incoming streams MUST be reset to 0 as the next expected stream
sequence number. If specific Stream Numbers are listed, then
only these specific streams MUST be reset to 0 and all other
non-listed stream sequence numbers remain unchanged.
E4: Any queued TSN's (queued at step E1) MUST now be released and
processed normally.
E5: A Stream Reset Response Parameter MUST be put into a STREAM
RESET chunk indicating successful processing.
E6: The STREAM RESET chunk MUST be sent after the incoming STREAM
RESET chunk is processed completely.
5.2.3. Receiver Side Procedures for the Incoming SSN Reset Request
Parameter
In the case that the endpoint is willing to perform a stream reset
the following steps must be followed:
F1: An Outgoing SSN Reset Request Parameter MUST be put into an
STREAM RESET chunk according to Section 5.1.2.
F2: The STREAM RESET chunk MUST be sent after the incoming STREAM
RESET chunk is processed completely.
If the endpoint is un-willing to perform the stream reset it MUST
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send a Stream Reset Response Parameter with the appropriate error set
to "Denied".
When a peer endpoint requests a Incoming SSN Reset Request it is
possible that the local endpoint has just sent an Outgoing SSN Reset
Request on the same stream and has not yet received a response. In
such a case the local endpoint SHOULD silently discard the request
and continue processing any other request found in the Stream Reset
Chunk.
It is also possible that the Incoming request will arrive after the
Outgoing SSN Reset Request just completed. In such a case all of the
streams being requested will be already set to 0. If so, the local
endpoint SHOULD send back a Stream Reset Response with the success
code "Nothing to do".
Note that in either race condition the local endpoint could
optionally also perform the reset. This would result in streams that
are already at sequence 0 being reset again to 0 which would cause no
harm to the application but will add an extra message to the network.
5.2.4. Receiver Side Procedures for the SSN/TSN Reset Request Parameter
In the case that the endpoint is willing to perform an SSN/TSN reset
the following steps must be followed:
G1: Compute an appropriate value for the Receiver's next TSN, the
TSN the peer should use to send the next DATA chunk. The value
SHOULD be the smallest TSN not acknowledged by the receiver of
the request plus 2^31.
G2: Compute an appropriate value for the local endpoint's next TSN,
i.e. the receiver of the SSN/TSN reset chunk next TSN to be
assigned. The value SHOULD be the highest TSN sent by the
receiver of the request plus 1.
G3: The same processing as if a SACK chunk with no gap report and a
cumulative TSN ACK of Sender's next TSN minus 1 was received
MUST be performed.
G4: The same processing as if a FWD-TSN chunk as defined in
[RFC3758] with all streams affected and a new cumulative TSN ACK
of Receiver's next TSN minus 1 was received MUST be performed.
G5: The next expected and outgoing stream sequence numbers MUST be
reset to 0 for all incoming and outgoing streams.
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G6: A Stream Reset Response Parameter MUST be put into a STREAM
RESET chunk indicating successful processing.
G7: The STREAM RESET chunk MUST be sent after the incoming STREAM
RESET chunk is processed completely.
5.2.5. Receiver Side Procedures for the Add Outgoing Streams Request
Parameter
When an SCTP endpoint receives a stream reset request adding
additional streams, it MUST send a response parameter either
acknowledging or denying the request. If the response is successful
the receiver MUST add the requested number of inbound streams to the
association, initializing the next expected stream sequence number to
be 0.
5.2.6. Receiver Side Procedures for the Stream Reset Response Parameter
On receipt of a Stream Reset Response Parameter the following must be
performed:
H1: If the Stream Reset Timer is running for the Stream Reset
Request Sequence Number indicated in the Stream Reset Response
Sequence Number field, the Stream Reset Request Sequence Number
MUST be marked as acknowledged. If all Stream Reset Request
Sequence Numbers the Stream Reset Timer is running for are
acknowledged, the Stream Reset Timer MUST be stopped. If the
timer was not running for the Stream Reset Request Sequence
Number, the processing of the Stream Reset Response Parameter is
complete.
H2: If the Result field indicates 'In progress', the timer for the
Stream Reset Request Sequence Number is started again. If the
timer runs off, the Stream Reset Chunk MUST be retransmitted but
the corresponding error counters MUST NOT be incremented.
H3: If the Result field does not indicate successful processing the
processing of this response is complete.
H4: If the request was an Outgoing SSN Reset Request the affected
streams MUST now be reset and all queued data should be
processed now and assigning of stream sequence numbers is
allowed again.
H5: If the request was an SSN/TSN Reset Request new data MUST be
sent from Receiver's next TSN and beginning with stream sequence
number 0 for all outgoing streams. All incoming streams MUST be
reset to 0 as the next expected stream sequence number. The
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peer will send DATA chunks starting with Sender's next TSN.
H6: If the request was to add outgoing streams, the endpoint MUST
add the additional streams to the association. Note that an
implementation may allocate the memory at the time of the
request, but it MUST NOT use the streams until the peer has
responded with a positive acknowledgment.
6. Socket API Considerations
This section describes how the socket API defined in
[I-D.ietf-tsvwg-sctpsocket] needs to be extended to make the features
of SCTP stream reset available to the application.
Please note that this section is informational only.
6.1. Events
When the SCTP_ASSOC_CHANGE notification is delivered and both peers
support the extension described in this document,
SCTP_ASSOC_SUPPORTS_STREAM_RESET should be listed in the sac_info
field.
The union sctp_notification {} is extended to contain three new
fields: sn_strreset_event, sn_assocreset_event, and
sn_strchange_event:
union sctp_notification {
struct {
uint16_t sn_type;
uint16_t sn_flags;
uint32_t sn_length;
} sn_header;
...
struct sctp_stream_reset_event sn_strreset_event;
struct sctp_assoc_reset_event sn_assocreset_event;
struct sctp_stream_change_event sn_strchange_event;
...
}
The corresponding sn_type values are given in Table 4.
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+--------------------------+----------------------------------------+
| sn_type | valid field in union sctp_notification |
+--------------------------+----------------------------------------+
| SCTP_STREAM_RESET_EVENT | sn_strreset_event |
| SCTP_ASSOC_RESET_EVENT | sn_assocreset_event |
| SCTP_STREAM_CHANGE_EVENT | sn_strchange_event |
+--------------------------+----------------------------------------+
Table 4
These events are delivered when an incoming request was processed
successfully or the processing of an outgoing request has been
finished.
6.1.1. Stream Reset Event
The event delivered has the following structure:
struct sctp_stream_reset_event {
uint16_t strreset_type;
uint16_t strreset_flags;
uint32_t strreset_length;
sctp_assoc_t strreset_assoc_id;
uint16_t strreset_stream_list[];
};
strreset_type: It should be SCTP_STREAM_RESET_EVENT.
strreset_flags: This field is formed from the bitwise OR of one or
more of the following currently defined flags:
SCTP_STREAM_RESET_INCOMING_SSN: The stream identifiers given in
strreset_stream_list[] refer to incoming streams of the
endpoint.
SCTP_STREAM_RESET_OUTGOING_SSN: The stream identifiers given in
strreset_stream_list[] refer to outgoing streams of the
endpoint.
SCTP_STREAM_RESET_DENIED: The corresponding request was denied by
the peer.
SCTP_STREAM_RESET_FAILED: The corresponding request failed.
At least one of SCTP_STREAM_RESET_INCOMING_SSN and
SCTP_STREAM_RESET_OUTGOING_SSN is set. SCTP_STREAM_RESET_DENIED
and SCTP_STREAM_RESET_FAILED are mutually exclusive. If the
request was successful, none of these are set.
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strreset_length: This field is the total length in bytes of the
delivered event, including the header.
strreset_assoc_id: The association id field, holds the identifier
for the association. All notifications for a given association
have the same association identifier. For one-to-one style
sockets, this field is ignored.
strreset_stream_list: The list of stream identifiers this event
refers to. An empty list identifies all streams as being reset.
Depending on strreset_flags the identifiers refer to incoming or
outgoing streams or both.
6.1.2. Association Reset Event
The event delivered has the following structure:
struct sctp_assoc_reset_event {
uint16_t assocreset_type;
uint16_t assocreset_flags;
uint32_t assocreset_length;
sctp_assoc_t assocreset_assoc_id;
uint32_t assocreset_local_tsn;
uint32_t assocreset_remote_tsn;
};
assocreset_type: It should be SCTP_ASSOC_RESET_EVENT.
assocreset_flags: This field is formed from the bitwise OR of one or
more of the following currently defined flags:
SCTP_ASSOC_RESET_DENIED: The corresponding outgoing request was
denied by the peer.
SCTP_ASSOC_RESET_FAILED: The corresponding outgoing request
failed.
SCTP_ASSOC_RESET_DENIED and SCTP_ASSOC_RESET_FAILED are mutual
exclusive. If the request was successful, none of these are set.
assocreset_length: This field is the total length in bytes of the
delivered event, including the header.
assocreset_assoc_id: The association id field, holds the identifier
for the association. All notifications for a given association
have the same association identifier. For one-to-one style
sockets, this field is ignored.
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assocreset_local_tsn: The next TSN used by the endpoint.
assocreset_remote_tsn: The next TSN used by the peer.
6.1.3. Stream Change Event
The event delivered has the following structure:
struct sctp_stream_change_event {
uint16_t strchange_type;
uint16_t strchange_flags;
uint32_t strchange_length;
sctp_assoc_t strchange_assoc_id;
uint16_t strchange_instrms;
uint16_t strchange_outstrms;
};
strchange_type: It should be SCTP_STREAM_CHANGE_EVENT.
strchange_flags: This field is formed from the bitwise OR of one or
more of the following currently defined flags:
SCTP_STREAM_CHANGE_DENIED: The corresponding request was denied
by the peer.
SCTP_STREAM_CHANGE_FAILED: The corresponding request failed.
SCTP_STREAM_CHANGE_DENIED and SCTP_STREAM_CHANGE_FAILED are mutual
exclusive. If the request was successful, none of these are set.
strchange_length: This field is the total length in bytes of the
delivered event, including the header.
strchange_assoc_id: The association id field, holds the identifier
for the association. All notifications for a given association
have the same association identifier. For one-to-one style
sockets, this field is ignored.
strchange_instrms: The number of streams that the peer is allowed to
use outbound.
strchange_outstrms: The number of streams that the endpoint is
allowed to use outbound.
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6.2. Event Subscription
There are two methods defined in the SCTP socket API to subscribe to
events. The original method defined was an events structure with the
socket option SCTP_EVENTS. Some implementations may have already
expanded their data structure for this API to include the stream
reset subscriptions. The new API is to use a setsockopt() call with
the SCTP_SET_EVENT socket option. This option takes a structure that
defines the association, the event type (using the same value found
in the event type field) and an on/off boolean. This newer API is
the preferred method but we define both methods for compatibility.
For some implementations the structure now takes on the form:
struct sctp_event_subscribe {
uint8_t sctp_data_io_event;
uint8_t sctp_association_event;
uint8_t sctp_address_event;
uint8_t sctp_send_failure_event;
uint8_t sctp_peer_error_event;
uint8_t sctp_shutdown_event;
uint8_t sctp_partial_delivery_event;
uint8_t sctp_adaptation_layer_event;
uint8_t sctp_authentication_event;
uint8_t sctp_sender_dry_event;
uint8_t sctp_stream_reset_event;
uint8_t sctp_assoc_reset_event;
uint8_t sctp_stream_change_event;
};
For those implementations that support this method simply putting a 1
or 0 in the sctp_stream_reset_event and setting the SCTP_EVENTS
socket option will work. However not all implementations support
this method.
The preferred method is to use the SCTP_SET_EVENT socket option and
fill in the structure sctp_set_event structure.
struct sctp_set_event {
sctp_assoc_t se_assoc_id;
uint16_t se_type;
uint8_t se_on;
};
Using this method, the user fills in the se_type with the same value
found in strreset_type field i.e. SCTP_STREAM_RESET_EVENT. The user
will also fill in the se_assoc_id field with either the association
to set this event on (this field is ignored for one-to-one style
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sockets) or one of the reserved constant values defined in the socket
API document. Finally the se_on field is set with a 1 to enable the
event or a 0 to disable the event.
6.3. Socket Options
The following table describes the new socket options which make the
SCTP stream reset features accessible to the user. They all use
IPPROTO_SCTP as their level.
+--------------------------+---------------------------+-----+-----+
| option name | data type | get | set |
+--------------------------+---------------------------+-----+-----+
| SCTP_ENABLE_STREAM_RESET | struct sctp_assoc_value | X | X |
| SCTP_RESET_STREAMS | struct sctp_reset_streams | | X |
| SCTP_RESET_ASSOC | sctp_assoc_t | | X |
| SCTP_ADD_OUT_STREAMS | struct sctp_assoc_value | | X |
+--------------------------+---------------------------+-----+-----+
Table 5
6.3.1. Enable/Disable Stream Reset (SCTP_ENABLE_STREAM_RESET)
This option allows a user to control whether the SCTP implementation
processes or denies incoming requests in STREAM_RESET chunks.
The default is to deny incoming requests.
To set or get this option the user fills in the following structure:
struct sctp_assoc_value {
sctp_assoc_t assoc_id;
uint32_t assoc_value;
};
assoc_id: This parameter is ignored for one-to-one style sockets.
For one-to-many style sockets this parameter indicates which
association the user is performing an action upon.
assoc_value: It is formed from the bitwise OR of one or more of the
following currently defined flags:
SCTP_DENY_RESET_IN_STREAM_REQ: Deny received Incoming SSN Reset
Requests if this flag is set, process it if not.
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SCTP_DENY_RESET_OUT_STREAM_REQ: Deny received Outgoing SSN Reset
Requests if this flag is set, process it if not.
SCTP_DENY_RESET_ASSOC_REQ: Deny received SSN/TSN Reset Requests
if this flag is set, process it if not.
SCTP_DENY_CHANGE_ASSOC_REQ: Deny received Add Outgoing Streams
Requests if this flag is set, process it if not.
The default value is SCTP_DENY_IN_STREAM_RESET|
SCTP_DENY_OUT_STREAM_RESET|SCTP_DENY_ASSOC_RESET|
SCTP_DENY_ASSOC_CHANGE.
Please note that using the option does not have any impact on
subscribing to any related events.
6.3.2. Reset Incoming and/or Outgoing Streams (SCTP_RESET_STREAMS)
This option allows the user to request the reset of incoming and/or
outgoing streams.
To set or get this option the user fills in the following structure:
struct sctp_reset_streams {
sctp_assoc_t srs_assoc_id;
uint16_t srs_flags;
uint16_t srs_number_streams;
uint16_t srs_stream_list[];
};
srs_assoc_id: This parameter is ignored for one-to-one style
sockets. For one-to-many style sockets this parameter indicates
which association the user is performing an action upon.
srs_flags: This parameter describes which class of streams is reset.
It is formed from the bitwise OR of one or more of the following
currently defined flags:
* SCTP_STREAM_RESET_INCOMING
* SCTP_STREAM_RESET_OUTGOING
srs_number_streams: This parameter is the number of elements in the
srs_stream_list. If it is zero, the operation is performed on all
streams.
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srs_stream_list: This parameter contains a list of stream
identifiers the operation is performed upon. It contains
srs_number_streams elements. If it is empty, the operation is
performed on all streams. Depending on srs_flags the identifiers
refer to incoming or outgoing streams or both.
6.3.3. Reset SSN/TSN (SCTP_RESET_ASSOC)
This option allows a user to request the reset of the SSN/TSN.
To set this option the user provides an option_value of type
sctp_assoc_t.
On one-to-one style sockets the option_value is ignored. For one-to-
many style sockets the option_value is the association identifier of
the association the action is to be performed upon.
6.3.4. Add Outgoing Streams (SCTP_ADD_OUT_STREAMS)
This option allows a user to request the addition of a number of
outgoing streams.
To set this option the user fills in the following structure:
struct sctp_assoc_value {
sctp_assoc_t assoc_id;
uint32_t assoc_value;
};
assoc_id: This parameter is ignored for one-to-one style sockets.
For one-to-many style sockets this parameter indicates which
association the user is performing an action upon.
assoc_value: This parameter is the number of outgoing streams to
add.
An endpoint can limit the number of incoming streams by using the
sinit_max_instreams field in the struct sctp_initmsg{} when issuing
an SCTP_INIT socket option, as defined in
[I-D.ietf-tsvwg-sctpsocket]. An incoming request asking for more
streams than allowed will be denied.
7. Security Considerations
The SCTP socket API as described in [I-D.ietf-tsvwg-sctpsocket]
exposes the sequence numbers of received DATA chunks to the
application. An application might expect them to be monotonically
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increasing. When using the stream reset extension this might no
longer be true. Therefore the application must enable this extension
explicitly before it is used. In addition, application must
subscribe explicitly to notifications related to the stream reset
extension before receiving them.
SCTP associations are protected against blind attackers by using the
verification tags. This is still valid when using the stream reset
extension. Therefore this extension does not add any additional
security risk to SCTP in relation to blind attackers.
When the both sequence numbers are reset, the maximum segment
lifetime is used to avoid the wrap-around for the TSN.
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 suggested values for the chunk type and the chunk parameter
types are tentative and to be confirmed by IANA.
]
This document (RFCXXXX) is the reference for all registrations
described in this section. The suggested changes are described
below.
8.1. A New Chunk Type
A chunk type has to be assigned by IANA. It is suggested to use the
values given in Table 1. IANA should assign this value from the pool
of chunks with the upper two bits set to '10'.
This requires an additional line in the "CHUNK TYPES" table for SCTP:
CHUNK TYPES
ID Value Chunk Type Reference
----- ---------- ---------
130 Stream Reset Chunk (STREAM_RESET) [RFCXXXX]
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The registration table as defined in
[I-D.ietf-tsvwg-sctp-chunk-flags] for the chunk flags of this chunk
type is empty.
8.2. Five New Parameter Types
IANA is requested to create a new sub-registry, "STREAM RESET Chunk
Parameter Types" with the following initial contents, taken from
Table 2 of this document:
--STREAM RESET Chunk Parameter Types
Chunk Parameter Type Value
-------------------- ----------
Outgoing SSN Reset Request Parameter 13 (0x000d)
Incoming SSN Reset Request Parameter 14 (0x000e)
SSN/TSN Reset Request Parameter 15 (0x000f)
Stream Reset Response Parameter 16 (0x0010)
Add Outgoing Streams Request Parameter 17 (0x0011)
9. Acknowledgments
The authors wish to thank Paul Aitken, Gorry Fairhurst, Tom Petch,
Kacheong Poon, Irene Ruengeler, Robin Seggelmann, and Vlad Yasevich
for there invaluable comments.
Appendix A. Examples of the Stream Reset procedures
Please note that this appendix is informational only.
The following message flows between an Endpoint A and an Endpoint Z
illustrate the described procedures. The time progresses in downward
direction.
The following example illustrates an Endpoint A resetting stream 1
and 2 for just its outgoing streams.
E-A E-Z
----------[STR_RESET(OUT-REQ:X/1,2)]---------->
<-------------[STR_RESET(RESP:X)]--------------
The following example illustrates an Endpoint A resetting stream 1
and 2 for just its incoming streams.
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E-A E-Z
-----------[STR_RESET(IN-REQ:X/1,2)]---------->
<--------[STR_RESET(OUT-REQ:Y,X/1,2)]----------
-------------[STR_RESET(RESP:Y)]-------------->
The following example illustrates an Endpoint A resetting all streams
in both directions.
E-A E-Z
-----[STR_RESET(OUT-REQ:X,Y-1)|IN-REQ:X+1]---->
<------[STR_RESET(RESP:X|OUT-REQ:Y,X+1)]-------
-------------[STR_RESET(RESP:Y)]-------------->
The following example illustrates an Endpoint A requesting the
streams and TSNs be reset. At the completion E-A has the new sending
TSN (selected by the peer) of B and E-Z has the new sending TSN of A
(also selected by the peer).
E-A E-Z
------------[STR_RESET(TSN-REQ:X)]------------>
<-----[STR_RESET(RESP:X/S-TSN=A, R-TSN=B)]-----
The following example illustrates an Endpoint A requesting to add 3
additional outgoing streams.
E-A E-Z
--------[STR_RESET(ADD_OUT_STRMS:X/3)]-------->
<-------------[STR_RESET(RESP:X)]--------------
10. References
10.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC3758] Stewart, R., Ramalho, M., Xie, Q., Tuexen, M., and P.
Conrad, "Stream Control Transmission Protocol (SCTP)
Partial Reliability Extension", RFC 3758, May 2004.
[RFC4960] Stewart, R., "Stream Control Transmission Protocol",
RFC 4960, September 2007.
[RFC5061] Stewart, R., Xie, Q., Tuexen, M., Maruyama, S., and M.
Kozuka, "Stream Control Transmission Protocol (SCTP)
Dynamic Address Reconfiguration", RFC 5061,
September 2007.
Stewart, et al. Expires June 2, 2011 [Page 30]
Internet-Draft SCTP Stream Reconfiguration November 2010
[I-D.ietf-tsvwg-sctp-chunk-flags]
Tuexen, M. and R. Stewart, "Stream Control Transmission
Protocol (SCTP) Chunk Flags Registration",
draft-ietf-tsvwg-sctp-chunk-flags-02 (work in progress),
October 2010.
10.2. Informative References
[I-D.ietf-tsvwg-sctpsocket]
Stewart, R., Poon, K., Tuexen, M., Yasevich, V., and P.
Lei, "Sockets API Extensions for Stream Control
Transmission Protocol (SCTP)",
draft-ietf-tsvwg-sctpsocket-24 (work in progress),
October 2010.
Authors' Addresses
Randall R. Stewart
Huawei
Chapin, SC 29036
USA
Email: randall@lakerest.net
Peter Lei
Cisco Systems, Inc.
8735 West Higgins Road
Suite 300
Chicago, IL 60631
USA
Email: peterlei@cisco.com
Michael Tuexen
Muenster University of Applied Sciences
Stegerwaldstr. 39
48565 Steinfurt
Germany
Email: tuexen@fh-muenster.de
Stewart, et al. Expires June 2, 2011 [Page 31]
