Network Working Group R. Stewart
Internet-Draft Researcher
Intended status: Standards Track P. Lei
Expires: January 6, 2010 Cisco Systems, Inc.
M. Tuexen
Muenster Univ. of Applied Sciences
July 5, 2009
Stream Control Transmission Protocol (SCTP) Stream Reconfiguration
draft-ietf-tsvwg-sctp-strrst-00.txt
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Abstract
Many applications that desire to use SCTP have requested the ability
to "reset" a stream. The intention of resetting a stream is to start
the numbering sequence of the stream back at 'zero' with a
corresponding notification to the upper layer that this act as been
performed. The applications that have requested this feature
normally desire it so that they can "re-use" streams for different
purposes but still utilize the stream sequence number for the
application to track the message flows. Thus, without this feature,
a new use on an old stream would result in message numbers larger
than expected without a protocol mechanism to "start the streams back
at zero". This documents presents also a method for resetting the
transport sequence numbers and all stream sequence numbers.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
2. Conventions . . . . . . . . . . . . . . . . . . . . . . . . . 4
3. Data Formats . . . . . . . . . . . . . . . . . . . . . . . . . 4
3.1. STREAM RESET Chunk . . . . . . . . . . . . . . . . . . . . 4
3.2. New Parameters . . . . . . . . . . . . . . . . . . . . . . 5
3.2.1. Outgoing SSN Reset Request Parameter . . . . . . . . . 5
3.2.2. Incoming SSN Reset Request Parameter . . . . . . . . . 7
3.2.3. SSN/TSN Reset Request Parameter . . . . . . . . . . . 7
3.2.4. Stream Reset Response Parameter . . . . . . . . . . . 8
3.2.5. Add Streams . . . . . . . . . . . . . . . . . . . . . 9
4. Procedures . . . . . . . . . . . . . . . . . . . . . . . . . . 10
4.1. Sender side procedures . . . . . . . . . . . . . . . . . . 10
4.1.1. Sender side procedures for the Stream Reset Chunk . . 11
4.1.2. Sender side procedures for the Outgoing SSN Reset
Request Parameter . . . . . . . . . . . . . . . . . . 11
4.1.3. Sender side procedures for the Incoming SSN Reset
Request Parameter . . . . . . . . . . . . . . . . . . 12
4.1.4. Sender side procedures for the SSN/TSN Reset
Request Parameter . . . . . . . . . . . . . . . . . . 13
4.1.5. Sender side procedures for the Stream Reset
Response Parameter . . . . . . . . . . . . . . . . . . 13
4.1.6. Sender side procedures for addition of streams . . . . 14
4.2. Receiver side procedures . . . . . . . . . . . . . . . . . 14
4.2.1. Receiver side procedures for the Stream Reset Chunk . 14
4.2.2. Receiver side procedures for the Outgoing SSN
Reset Request Parameter . . . . . . . . . . . . . . . 14
4.2.3. Receiver side procedures for the Incoming SSN
Reset Request Parameter . . . . . . . . . . . . . . . 15
4.2.4. Receiver side procedures for the SSN/TSN Reset
Request Parameter . . . . . . . . . . . . . . . . . . 16
4.2.5. Receiver side procedures for addition of streams . . . 17
4.2.6. Receiver side procedures for the Stream Reset
Response Parameter . . . . . . . . . . . . . . . . . . 17
4.3. Various Examples of the Stream Reset procedures . . . . . 17
5. Socket API considerations . . . . . . . . . . . . . . . . . . 18
5.1. Stream Reset event . . . . . . . . . . . . . . . . . . . . 19
5.2. Steam Reset socket options . . . . . . . . . . . . . . . . 19
6. Security Considerations . . . . . . . . . . . . . . . . . . . 19
7. Iana Considerations . . . . . . . . . . . . . . . . . . . . . 19
8. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 19
9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 19
9.1. Normative References . . . . . . . . . . . . . . . . . . . 19
9.2. Informative References . . . . . . . . . . . . . . . . . . 20
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 20
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1. Introduction
Many applications that desire to use [RFC4960] have requested the
ability to "reset" a stream. The intention of resetting a stream is
to start the numbering sequence of the stream back at 'zero' with a
corresponding notification to the upper layer that this act as been
performed. The applications that have requested this feature
normally desire it so that they can "re-use" streams for different
purposes but still utilize the stream sequence number for the
application to track the message flows. Thus, without this feature,
a new use of an old stream would result in message numbers larger
than expected without a protocol mechanism to "start the streams back
at zero". This documents presents also a method for resetting the
transport sequence numbers and all stream sequence numbers.
[ Editors note: We probably need to add more text here ]
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. Data Formats
This section examines all new data formats defined by this document.
All transported integer numbers are in "network byte order" a.k.a.,
Big Endian, unless otherwise noted.
3.1. STREAM RESET Chunk
This document adds one new chunk type to SCTP. The suggested value
for this chunk is 0x82 hex or 130 decimal. The range selected by
IANA must have the upper bit (or ignore bit) set and the next to
highest bit (or the report bit) cleared. 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) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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Chunk Type: 1 byte (unsigned integer)
This field holds the IANA defined chunk type for the STREAM RESET
chunk.
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, 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 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. Stream Reset Response Parameter.
6. Stream Reset Response Parameter, Outgoing SSN Reset Request
Parameter.
7. Stream Reset Response Parameter, Stream Reset Response Parameter.
3.2. New Parameters
This section identifies four new parameters, their formats, and in
what chunk type these parameters may appear.
3.2.1. Outgoing SSN Reset Request Parameter
This parameter is used by the sender to request some outgoing streams
to be reset.
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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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Stream Reset Request Sequence Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Stream Reset Response Sequence Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Senders 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 of the parameter.
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.
Stream Reset Response Sequence Number: 4 bytes (unsigned integer)
In case that 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 the other case it holds the next expected
Stream Reset Request Sequence Number - 1.
Senders 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.
Stream Number N: 2 bytes (unsigned integer)
This optional field, if included, is used to indicates specific
streams that are to be reset. If no streams are listed, then ALL
streams are to be reset.
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This parameter can appear in a STREAM RESET chunk. This parameter
MUST NOT appear in any other chunk type.
3.2.2. Incoming SSN Reset Request Parameter
This parameter is used by the sender to request that the peer
requests some of its outgoing streams to be reset.
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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 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 of the parameter.
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.
Stream Number 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.
3.2.3. SSN/TSN Reset Request Parameter
This parameter is used by the sender to request to reset the TSN and
SSN numbering of all 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 = 0x000f | Parameter Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 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 of the parameter.
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.
This parameter can appear in a STREAM RESET chunk. This parameter
MUST NOT appear in any other chunk type.
3.2.4. Stream Reset Response Parameter
This parameter is used by the receiver of a stream reset request
parameter to respond to the stream reset request.
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.
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Parameter Type Length: 2 bytes (unsigned integer)
This field holds the length of the parameter.
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 | Nothing to do |
| 1 | Performed |
| 2 | Denied |
| 3 | Error - Wrong SSN |
| 4 | Error - Request already in progress |
| 5 | Error - Bad Sequence Number |
+--------+-------------------------------------+
Table 1
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.
This parameter can appear in a STREAM RESET chunk. This parameter
MUST NOT appear in any other chunk type.
3.2.5. Add Streams
This parameter is used by the sender to request that the peer add the
requested number of streams to the association.
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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 = 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 of the parameter, a fixed value of 12
MUST be found in this field.
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.
Number of new streams: 2 bytes (unsigned integer) This value holds
the number of additional streams the sender would like added to
the association. Streams are added in order and are consecutive,
e.g. if an association has four 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 can appear in a STREAM RESET chunk. This parameter
MUST NOT appear in any other chunk type.
4. 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.
4.1. Sender side procedures
This section describes the procedures related to the sending of
Stream Reset Chunks. A Stream Reset Chunk is a composition of a Type
Length Value (TLV) parameters.
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4.1.1. Sender side procedures for the Stream Reset Chunk
Note that before sending a Stream Reset Chunk the sender MUST ensure
that the peer advertised support for the stream reset extension. The
indication for support of the extensions MUST be determined using the
Supported Extensions Parameter in either the INIT or INIT-ACK. This
parameter is defined in [RFC5061]. If the chunk value '0x82' 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' when 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
RTO timer) and MUST use exponential backoff doubling the value at
every expiration. If the timer does expire, 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 do threshold management possibly destroying the
association if SCTP retransmission thresholds are surpassed.
4.1.2. 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 if 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. This is because it is unknown as
to if the receiver of the request will accept or deny it and
more so, 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 put it into the Stream Reset Request Sequence Number
field of the Outgoing SSN Reset Request Parameter. After
assigning it the next stream reset request sequence number MUST
be incremented by '1'.
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A3: If this Outgoing SSN Reset Request Parameter is sent in response
to an Incoming SSN Request Parameter the Stream Reset Request
Sequence Number of the Incoming SSN Request Parameter is copied
into the Stream Reset Response Sequence Number field of the
Outgoing SSN Reset Request Parameter. If the Outgoing SSN Reset
Request Parameter is sent on request of the upper layer the
Stream Reset Response Sequence Number is the next expected
Stream Reset Request Sequence Number of the peer - 3.
A4: The sender fills in the TSN it has assigned last.
A5: If this Outgoing SSN Reset Request Parameter is sent in response
to an Incoming SSN Request Parameter the Stream Numbers are
copied from the Incoming SSN Request Parameter to the Outgoing
SSN Reset Request Parameter. If this Outgoing SSN Reset Request
Parameter is sent on request of the upper layer and the sender
wants all outgoing streams to be reset no Stream Numbers MUST be
put into the Outgoing SSN Reset Request Parameter. If the
sender wants only some outgoing streams to be reset these Stream
Numbers MUST be filled in the Outgoing SSN Reset Request
Parameter.
A6: The Outgoing SSN Reset Request Parameter is put into a STREAM
RESET Chunk. It MAY be put together with an Incoming SSN Reset
Request Parameter or an Stream Reset Response Parameter and MUST
NOT be put together with any other parameter.
A7: The STREAM RESET Chunk is sent following the rules given in
Section 4.1.1
4.1.3. 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 if 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 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 MUST 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
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Reset Request Parameter.
B3: The Incoming SSN Reset Request Parameter is put into a STREAM
RESET Chunk. It MAY be put together with an Outgoing SSN Reset
Request Parameter and MUST NOT be put together with any other
parameter.
B4: The STREAM RESET Chunk is sent following the rules given in
Section 4.1.1
4.1.4. Sender side procedures for the SSN/TSN Reset Request Parameter
When an SCTP sender wants to reset the SSNs and TSNs it can send a
SSN/TSN Reset Request Parameter if the Stream Reset Timer is not
running. The following steps MUST be followed:
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.
C3: The SSN/TSN Reset Request Parameter is put into a STREAM RESET
Chunk. There MUST NOT be any other parameter in this chunk.
C4: The STREAM RESET Chunk is sent following the rules given in
Section 4.1.1
4.1.5. Sender side procedures for the Stream Reset Response Parameter
When an implementation receives a 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
is 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 is filled in
the Result field of the Stream Reset Response Parameter
D3 If the incoming request is a SSN/TSN reset requests, the Sender's
next TSN field is filled with the next TSN the sender of this
Stream Reset Response Parameter will assign. For other requests
the Sender's next TSN field is not filled.
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D4 If the incoming request is a SSN/TSN reset request, the
Receiver's next TSN field is 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. A good value for
this is the highest TSN it has seen plus some delta. For other
requests the Sender's next TSN field is not filled.
4.1.6. Sender side procedures for addition of streams
When an SCTP sender wants to increase the number of outbound streams
it is able to send to, it may add a Add Streams 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 steams 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.
Any new stream MUST number its first message to be stream sequence 0.
4.2. Receiver side procedures
4.2.1. Receiver side procedures for the Stream Reset Chunk
Upon reception of a Stream Reset Chunk each parameter within it
should be processed. If some parameters have to be sent back, they
MUST all be put into one STREAM RESET chunk. If the received STREAM
RESET chunk contains at least one request parameter, a SACK chunk
MUST 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, the same STREAM RESET
chunk has to be sent back in response as earlier.
4.2.2. Receiver side procedures for the Outgoing SSN Reset Request
Parameter
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 reset
any streams it MUST send a stream reset response as described in
Section 4.1.5 with an appropriate Result field.
In the case that the endpoint is willing to perform a stream reset
the following steps SHOULD be followed:
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E1 If the Senders 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 effected 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. Note that the receiver of a stream reset that causes it to
entered deferred reset processing does NOT withhold the stream
reset acknowledgment from the peer. This also means that the
receiver will need to queue up any additional stream reset
requests received including the one that caused the receiver to
enter deferred reset processing.
E2 If the Stream Reset Timer is running for the Stream Reset Request
Sequence Number indicated in the Stream Reset Response Sequence
Number field, mark the Stream Reset Request Sequence Number as
acknowledged. If all Stream Reset Request Sequence Numbers the
Stream Reset Timer is running for are acknowledged, stop the
Stream Reset Timer.
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 Optionally an Upper Layer Notification SHOULD be sent to inform
the local endpoint that the inbound streams have been reset.
E5 Any queued TSN's (queued at step D3) should now be released and
processed normally.
E6 A Stream Reset Response Parameter is put into a STREAM RESET
chunk indicating successful processing.
E7 The STREAM RESET chunk is sent after the incoming STREAM RESET
chunk is processed completely.
4.2.3. Receiver side procedures for the Incoming SSN Reset Request
Parameter
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 reset
any streams it MUST send a stream reset response as described in
Section 4.1.5 with an appropriate Result field.
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In the case that the endpoint is willing to perform a stream reset
the following steps SHOULD be followed:
F1 An Outgoing Stream Reset Request Parameter MUST be put into an
STREAM RESET chunk according to Section 4.1.2.
F2 The STREAM RESET chunk is sent after the incoming STREAM RESET
chunk is processed completely.
4.2.4. Receiver side procedures for the SSN/TSN Reset Request Parameter
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 reset
any streams it MUST send a stream reset response as described in
Section 4.1.5 with an appropriate Result field.
In the case that the endpoint is willing to perform a SSN/TSN reset
the following steps SHOULD 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. Note that an
appropriate value should be larger than the highest TSN last
received plus a delta of at least 500 additional TSN's.
G2 Compute an appropriate value for the local endpoints next TSN,
i.e. the receiver of the SSN/TSN reset chunks next TSN to be
assigned. Note that an appropriate value should be larger than
the endpoints current next TSN to send by at least one TSN.
G3 Do the same processing as if a SACK chunk with no gap report and
a cumulative TSN ACK of Sender's next TSN - 1 was received.
G4 Do the same processing as if an FWD-TSN chunk with all streams
affected and a new cumulative TSN ACK of Receiver's next TSN - 1
was received.
G5 All incoming and outgoing streams MUST be reset to '0' as the
next expected and outgoing stream sequence numbers, respectively.
G6 A Stream Reset Response Parameter is put into a STREAM RESET
chunk indicating successful processing.
G7 The STREAM RESET chunk is sent after the incoming STREAM RESET
chunk is processed completely.
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4.2.5. Receiver side procedures for addition of streams
When an SCTP endpoint receives a stream reset request adding
additional streams, it MUST send a response parameter either
acknowledging or rejecting 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.
4.2.6. 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, mark the Stream Reset Request Sequence Number as
acknowledged. If all Stream Reset Request Sequence Numbers the
Stream Reset Timer is running for are acknowledged, stop the
Stream Reset Timer. 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 does not indicate successful processing an
Upper Layer Notification SHOULD be sent to inform the local
endpoint of the failure to reset its outbound streams.
Afterwards processing of this response is complete.
H3 If the request was an Outgoing Stream Reset Request the affected
streams should now be reset and all queued data should be
processed now and assigning of stream sequence numbers is allowed
again. Optionally an Upper Layer Notification SHOULD be sent to
inform the local endpoint that the outbound streams have been
reset.
H4 If the request was a SSN/TSN Reset Request new DATA should be
sent from Receiver's next TSN and beginning with stream sequence
number '0' for all outgoing streams. All incoming streams are
also reset to '0' as the next expected stream sequence number.
The peer will send DATA chunks starting with Sender's next TSN.
4.3. Various Examples of the Stream Reset procedures
The following example illustrates an Endpoint A resetting all streams
in both directions.
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E-A E-Z
----------[STR_RESET(IN-REQ:X|OUT-REQ:X+1,Y-3)]------->
<-[STR_RESET(RESP:Y|OUT-REQ:Y+1,X+1))]---------
-------[STR_RESET(RESP:Y)]----------------->
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/1,2)]------------
The following example illustrates an Endpoint A resetting stream 1
and 2 for just its incoming streams.
E-A E-Z
------[STR_RESET(IN-REQ:X/1,2]----------->
<---[STR_RESET(RESP:X/1,2]-------
The following example illustrates an Endpoint A requesting the
streams and TSN's 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]-------
5. Socket API considerations
This section is incomplete and will describe how the socket API
defined in [I-D.ietf-tsvwg-sctpsocket] SHOULD be extended to make the
features of SCTP stream reset available to the application.
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5.1. Stream Reset event
We need a constant for subscribing to the event and the event
structure.
5.2. Steam Reset socket options
We need socket options to reset the SSNs, TSNs, combinations of it
and to add streams.
6. Security Considerations
Having the ability to reset a stream should not pose any additional
security risk to SCTP. An attacker that can successfully inject a
stream reset would also be able to inject data or other malicious
information into an association such as an ABORT.
7. Iana Considerations
This document defines one new chunk type and four new parameter
types. This document recommends the values of 0x82 for the chunk
type and 0x000d, 0x000e, 0x000f, 0x0010 and 0x0011 for the new
parameter types. However IANA may assign any free chunk or parameter
type as long it is from the same chunk or parameter pool. In the
case of the chunk, it MUST be from the pool of chunks with the upper
two bits set to '10'. In the case of the parameters, it MUST be from
the pool whose upper bits are set to '00'.
8. Acknowledgments
The authors wish to thank Paul Aitken and Irene Ruengeler for there
invaluable comments.
9. References
9.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC4960] Stewart, R., "Stream Control Transmission Protocol",
RFC 4960, September 2007.
[RFC5061] Stewart, R., Xie, Q., Tuexen, M., Maruyama, S., and M.
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Kozuka, "Stream Control Transmission Protocol (SCTP)
Dynamic Address Reconfiguration", RFC 5061,
September 2007.
9.2. 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-19 (work in progress),
February 2009.
Authors' Addresses
Randall R. Stewart
Researcher
Chapin, SC 29036
USA
Phone:
Email: randall@lakerest.net
Peter Lei
Cisco Systems, Inc.
8735 West Higgins Road
Suite 300
Chicago, IL 60631
USA
Phone:
Email: peterlei@cisco.com
Michael Tuexen
Muenster Univ. of Applied Sciences
Stegerwaldstr. 39
48565 Steinfurt
Germany
Email: tuexen@fh-muenster.de
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