draft-ietf-tsvwg-addip-sctp-02.txt   draft-ietf-tsvwg-addip-sctp-03.txt 
skipping to change at page 1, line 15 skipping to change at page 1, line 15
Cisco Systems Cisco Systems
Q. Xie Q. Xie
Motorola Motorola
M. Tuexen M. Tuexen
Siemens AG Siemens AG
I. Rytina I. Rytina
Ericsson Ericsson
P. Conrad P. Conrad
Temple University Temple University
expires in six months June 29, 2001 expires in six months Novmeber 19, 2001
SCTP Extensions for Dynamic Reconfiguration of IP Addresses SCTP Extensions for Dynamic Reconfiguration of IP Addresses
and Enforcement of Flow and Message Limits
<draft-ietf-tsvwg-addip-sctp-02.txt> <draft-ietf-tsvwg-addip-sctp-03.txt>
Status of This Memo Status of This Memo
This document is an Internet-Draft and is in full conformance with This document is an Internet-Draft and is in full conformance with
all provisions of Section 10 of RFC 2026 [RFC2026]. Internet-Drafts all provisions of Section 10 of RFC 2026 [RFC2026]. Internet-Drafts
are working documents of the Internet Engineering Task Force (IETF), are working documents of the Internet Engineering Task Force (IETF),
its areas, and its working groups. Note that other groups may also its areas, and its working groups. Note that other groups may also
distribute working documents as Internet-Drafts. distribute working documents as Internet-Drafts.
The list of current Internet-Drafts can be accessed at The list of current Internet-Drafts can be accessed at
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Abstract Abstract
This document describes extensions to the Stream Control This document describes extensions to the Stream Control
Transmission Protocol (SCTP) [RFC2960] that provide methods to (1) Transmission Protocol (SCTP) [RFC2960] that provide methods to (1)
reconfigure IP address information on an existing association and reconfigure IP address information on an existing association and
(2) request that a peer set flow limits in units of bytes or (2) request that a peer set flow limits in units of bytes or
messages, either on a per-stream or per-association basis. messages, either on a per-stream or per-association basis.
TABLE OF CONTENTS TABLE OF CONTENTS
1. Introduction............................................... 2 1. Introduction............................................... 2
2. Conventions................................................ 3 2. Conventions................................................ 2
3. Additional Chunks and Parameters........................... 3 3. Additional Chunks and Parameters........................... 3
3.1 New Chunk Types........................................... 4 3.1 New Chunk Types........................................... 3
3.1.1 Address/Stream Configuration Change Chunk (ASCONF)...... 4 3.1.1 Address/Stream Configuration Change Chunk (ASCONF)...... 3
3.1.2 Address/Stream Configuration Acknowledgment Chunk 3.1.2 Address/Stream Configuration Acknowledgment Chunk
(ASCONF-ACK)............................................ 5 (ASCONF-ACK)............................................ 5
3.2 New Parameter Types....................................... 6 3.2 New Parameter Types....................................... 6
3.2.1 Add IP Address.......................................... 7 3.2.1 Add IP Address.......................................... 6
3.2.2 Delete IP Address....................................... 7 3.2.2 Delete IP Address....................................... 7
3.2.3 Stream Flow Limit Change................................ 8 3.2.3 Error Cause Indication.................................. 7
3.2.4 Error Cause Indication.................................. 9 3.2.4 Set Primary IP Address.................................. 8
3.2.5 Set Primary IP Address.................................. 9 3.2.5 Success Indication...................................... 8
3.2.6 Success Indication......................................10 3.2.6 Adaption Layer Indication............................... 9
3.2.7 Stream Message Limit Change.............................10 3.3 New Error Causes.......................................... 9
3.2.8 Association Message Limit Change........................11 3.3.1 Error Cause: Request to Delete Last Remaining IP Address 9
3.3 New Error Causes..........................................11 3.3.2 Error Cause: Operation Refused Due to Resource Shortage.10
3.3.1 Error Cause: Request to Delete Last Remaining IP 3.3.3 Error Cause: Request to Delete Source IP Address........11
Address.................................................12 4. Procedures.................................................11
3.3.2 Error Cause: Operation Refused Due to Resource Shortage.12 4.1 ASCONF Chunk Procedures...................................11
3.3.3 Error Cause: Request to Delete Source IP Address........13 4.1.1 Congestion Control of ASCONF Chunks.....................13
4. Procedures.................................................13 4.2 Upon reception of an ASCONF Chunk.........................14
4.1 ASCONF Chunk Procedures...................................14 4.3 General rules for address manipulation....................15
4.1.1 Congestion Control of ASCONF Chunks.....................15 4.3.1 A special case for OOTB ABORT chunks....................18
4.2 Upon reception of an ASCONF Chunk.........................16 4.3.2 A special case for changing an address..................19
4.3 General rules for address manipulation....................18 4.4 Setting of the primary address............................19
4.3.1 A special case for OOTB ABORT chunks....................20 5. Security Considerations....................................19
4.3.2 A special case for changing an address..................21 6. IANA considerations........................................20
4.4 Setting of the primary address............................21 7. Authors' Addresses.........................................20
4.5 Stream Flow/Message Limit Procedures......................22 8. References.................................................21
4.5.1 Stream receiver side procedures.........................22
4.5.2 Stream sender side procedures...........................23
4.5.3 ULP considerations on the use of SCTP flow limit
facility................................................24
4.6 Association Message Limit Procedures......................25
4.6.1 Receiver side procedures................................25
4.6.2 Sender side procedures..................................25
5. Security Considerations....................................26
6. IANA considerations........................................26
7. Authors' Addresses.........................................26
8. References.................................................27
1. Introduction 1. Introduction
To extend the utility and application scenarios of SCTP, this To extend the utility and application scenarios of SCTP, this
document introduces optional extensions that provide SCTP with the document introduces optional extensions that provide SCTP with the
ability to reconfigure IP address information on an existing ability to reconfigure IP address information on an existing
association or to request that the peer set flow limits in units association.
of bytes or messages, either on a per-stream or per-association
basis.
These extensions enable SCTP to be utilized in the following This extension enable SCTP to be utilized in the following
applications: applications:
- Dynamic IP address reconfiguration extension: For - Dynamic IP address reconfiguration extension: For
computational or networking platforms that allow addition/removal of computational or networking platforms that allow addition/removal of
physical interface cards this feature can provide: physical interface cards this feature can provide:
A) a graceful method to add to the interfaces of an existing A) a graceful method to add to the interfaces of an existing
association. For IPv6 this feature allows renumbering association. For IPv6 this feature allows renumbering
of existing associations. of existing associations.
B) a method for an endpoint to request that its peer set B) a method for an endpoint to request that its peer set
its primary destination address. This can be useful its primary destination address. This can be useful
when an address is about to be deleted, or when an endpoint when an address is about to be deleted, or when an endpoint
has some predetermined knowledge about which is the has some predetermined knowledge about which is the
preferred address to receive SCTP packets upon. preferred address to receive SCTP packets upon.
- The SCTP flow limit extension: This extension enables
a receiver to request that a sender impose a byte limit on the
outstanding data present on a per-stream basis.
The SCTP flow limit extension provides:
A) The ability to minimize the occurrence of a single stream
monopolizing all transport level resources (e.g. a_rwnd
"deadlock").
B) The ability to dynamically change the stream buffering
limits as the application deems appropriate at any particular
instant.
- The SCTP message limit extension: This extension enables a
receiver to request that a sender impose a limit on the number
of outstanding messages present on:
A) each stream, and/or
B) the whole association.
The SCTP message limit extension provides a method for minimizing
the occurrence of a lack of resources needed for messages even
when resources for payload data are still available. This can
become important when handling a large number of short messages.
2. Conventions 2. Conventions
The keywords MUST, MUST NOT, REQUIRED, SHALL, SHALL NOT, SHOULD, The keywords MUST, MUST NOT, REQUIRED, SHALL, SHALL NOT, SHOULD,
SHOULD NOT, RECOMMENDED, NOT RECOMMENDED, MAY, and OPTIONAL, when SHOULD NOT, RECOMMENDED, NOT RECOMMENDED, MAY, and OPTIONAL, when
they appear in this document, are to be interpreted as described in they appear in this document, are to be interpreted as described in
RFC 2119 [RFC2119]. RFC 2119 [RFC2119].
3. Additional Chunks and Parameters 3. Additional Chunks and Parameters
This section describes the addition of two new chunks and, eight This section describes the addition of two new chunks and, eight
new parameters to allow: new parameters to allow:
- Dynamic addition of IP Addresses to an association. - Dynamic addition of IP Addresses to an association.
- Dynamic deletion of IP Addresses to an association. - Dynamic deletion of IP Addresses to an association.
- A request to set the primary address the peer will - A request to set the primary address the peer will
use when sending to an endpoint. use when sending to an endpoint.
- The setting of stream byte limits.
- The setting of stream message limits.
- The setting of association message limits.
Additionally, this section describes three new error causes that Additionally, this section describes three new error causes that
support these new chunks and parameters. support these new chunks and parameters.
3.1 New Chunk Types 3.1 New Chunk Types
This section defines two new chunk types that will be used to This section defines two new chunk types that will be used to
transfer the control information reliably. Table 1 illustrates the transfer the control information reliably. Table 1 illustrates the
two new chunk types. two new chunk types.
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This value determines the type of address found in the This value determines the type of address found in the
Address Bytes field. If the value is 5 then the first Address Bytes field. If the value is 5 then the first
4 bytes of the Address Bytes field contain an IPv4 address, 4 bytes of the Address Bytes field contain an IPv4 address,
in network byte order. If the value is 6 then the first in network byte order. If the value is 6 then the first
16 bytes of the Address Bytes field contain an IPv6 address, 16 bytes of the Address Bytes field contain an IPv6 address,
in network byte order. in network byte order.
Address Bytes: 16 bytes (unsigned chars) Address Bytes: 16 bytes (unsigned chars)
This field contains an address which is part of the association. This field contains an IP address of the sender of the ASCONF
chunk, the address MUST be considered part of the association
by the peer endpoint (the receiver of the ASCONF chunk).
This field may be used by the receiver of the ASCONF to help This field may be used by the receiver of the ASCONF to help
in finding the association. in finding the association.
ASCONF-Request Correlation ID: 32 bits (unsigned integer) ASCONF-Request Correlation ID: 32 bits (unsigned integer)
This is an opaque integer assigned by the sender to identify each This is an opaque integer assigned by the sender to identify each
request parameter. It is in host byte order and is only meaningful request parameter. It is in host byte order and is only meaningful
to the sender. The receiver of the ASCONF Chunk will copy this 32 to the sender. The receiver of the ASCONF Chunk will copy this 32
bit value into the ASCONF Correlation ID field of the bit value into the ASCONF Correlation ID field of the
ASCONF-ACK. The sender of the ASCONF can use this same value in the ASCONF-ACK. The sender of the ASCONF can use this same value in the
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3.2 New Parameter Types 3.2 New Parameter Types
The eight new parameters added follow the format defined in section The eight new parameters added follow the format defined in section
3.2.1 of [RFC2960]. Table 2 describes the parameters. 3.2.1 of [RFC2960]. Table 2 describes the parameters.
Address Configuration Parameters Parameter Type Address Configuration Parameters Parameter Type
------------------------------------------------- -------------------------------------------------
Add IP Address 0xC001 Add IP Address 0xC001
Delete IP Address 0xC002 Delete IP Address 0xC002
Stream Byte Limit Request 0xC003
Error Cause Indication 0xC004 Error Cause Indication 0xC004
Set Primary Address 0xC005 Set Primary Address 0xC005
Success report 0xC006 Success report 0xC006
Stream Message Limit Request 0xC007
Association Message Limit Request 0xC008
Table 2: Address Configuration Parameters Table 2: Address Configuration Parameters
3.2.1 Add IP Address 3.2.1 Add IP Address
0 1 2 3 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 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 = 0xC001 | Length = Variable | | Type = 0xC001 | Length = Variable |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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| Type=5 | Length = 8 | | Type=5 | Length = 8 |
+----------------+---------------+ +----------------+---------------+
| Value=0x0a010101 | | Value=0x0a010101 |
+----------------+---------------+ +----------------+---------------+
Valid Chunk Appearance Valid Chunk Appearance
The Delete IP Address parameter may only appear in the ASCONF Chunk The Delete IP Address parameter may only appear in the ASCONF Chunk
type. type.
3.2.3 Stream Flow Limit Change 3.2.3 Error Cause Indication
0 1 2 3 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 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 =0xC003 | Length = Variable | | Type =0xC003 | Length = Variable |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Stream Number 1 | Byte Limit 1 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
\ /
/ \
\ /
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Stream Number N | Byte Limit N |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Stream Number n : 16 bits (unsigned integer)
This is the stream number for which a limit is to be enforced.
Byte Limit n : 16 bits (unsigned integer)
This is the limit (in bytes) that the receiver (sending the chunk)
is requesting that the sender (receiver of the chunk) enforce as
the maximum amount of outstanding data permitted at any time on
this stream, as per the rules in Section 4.5. Note that the value
'0' holds a special meaning described in Section 4.5.1
Valid Chunk Appearance
The Stream Flow Limit Change parameter may appear in the ASCONF
chunk, the INIT, or the INIT-ACK chunk type. The inclusion of this
parameter in the INIT or INIT-ACK can be used to indicate initial
byte limits.
3.2.4 Error Cause Indication
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 = 0xC004 | Length = Variable |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Error Cause(s) or Return Info on Success | | Error Cause(s) or Return Info on Success |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
When reporting an error this response parameter is used to wrap When reporting an error this response parameter is used to wrap
one or more standard error causes normally found within an SCTP one or more standard error causes normally found within an SCTP
Operational Error or SCTP Abort (as defined in [RFC2960]). The Operational Error or SCTP Abort (as defined in [RFC2960]). The
Error Cause(s) follow the format defined in section 3.3.10 of Error Cause(s) follow the format defined in section 3.3.10 of
[RFC2960]. [RFC2960].
Valid Chunk Appearance Valid Chunk Appearance
The Error Cause Indication parameter may only appear in the The Error Cause Indication parameter may only appear in the
ASCONF-ACK chunk type. ASCONF-ACK chunk type.
3.2.5 Set Primary IP Address 3.2.4 Set Primary IP Address
0 1 2 3 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 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 =0xC005 | Length = Variable | | Type =0xC004 | Length = Variable |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Address Parameter | | Address Parameter |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Address Parameter: TLV Address Parameter: TLV
This field contains an IPv4 or IPv6 address parameter as described in This field contains an IPv4 or IPv6 address parameter as described in
3.3.2.1 of [RFC2960]. The complete TLV is wrapped within this 3.3.2.1 of [RFC2960]. The complete TLV is wrapped within this
parameter. It requests the receiver to mark the specified address parameter. It requests the receiver to mark the specified address
as the primary address to send data to (see section 5.1.2 of as the primary address to send data to (see section 5.1.2 of
[RFC2960]). The receiver MAY mark this as its primary upon [RFC2960]). The receiver MAY mark this as its primary upon
receiving this request. receiving this request.
An example TLV requesting that the IPv4 address 10.1.1.1 be made the An example TLV requesting that the IPv4 address 10.1.1.1 be made the
primary destination address would look as follows: primary destination address would look as follows:
+--------------------------------+ +--------------------------------+
| Type=0xC005 | Length = 12 | | Type=0xC004 | Length = 12 |
+--------------------------------+ +--------------------------------+
| Type=5 | Length = 8 | | Type=5 | Length = 8 |
+----------------+---------------+ +----------------+---------------+
| Value=0x0a010101 | | Value=0x0a010101 |
+----------------+---------------+ +----------------+---------------+
Valid Chunk Appearance Valid Chunk Appearance
The Set Primary IP Address parameter may appear in the ASCONF Chunk, The Set Primary IP Address parameter may appear in the ASCONF Chunk,
the INIT, or the INIT-ACK chunk type. The inclusion of this parameter the INIT, or the INIT-ACK chunk type. The inclusion of this parameter
in the INIT or INIT-ACK can be used to indicate an initial preference in the INIT or INIT-ACK can be used to indicate an initial preference
of primary address. of primary address.
3.2.6 Success Indication 3.2.5 Success Indication
0 1 2 3 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 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 = 0xC006 | Length = 4 | | Type = 0xC005 | Length = 4 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
By default if a responding endpoint does not report an error for any By default if a responding endpoint does not report an error for any
requested TLV, a success is implicitly indicated. Thus a sender of a requested TLV, a success is implicitly indicated. Thus a sender of a
ASCONF-ACK MAY indicate complete success of all TLVs in an ASCONF by ASCONF-ACK MAY indicate complete success of all TLVs in an ASCONF by
returning only the Chunk Type, Chunk Flags, Chunk Length (set to 8) returning only the Chunk Type, Chunk Flags, Chunk Length (set to 8)
and the Serial Number. and the Serial Number.
The responding endpoint MAY also choose to explicitly report a The responding endpoint MAY also choose to explicitly report an
success for a requested TLV, by returning a success report ASCONF success for a requested TLV, by returning a success report ASCONF
Parameter Response. Parameter Response.
Valid Chunk Appearance Valid Chunk Appearance
The Success Indication parameter may only appear in the ASCONF-ACK The Success Indication parameter may only appear in the ASCONF-ACK
chunk type. chunk type.
3.2.7 Stream Message Limit Change 3.2.6 Adaption Layer Indication
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 =0xC007 | Length = Variable |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Stream Number 1 | Message Limit 1 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
\ /
/ \
\ /
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Stream Number N | Message Limit N |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Stream Number n : 16 bits (unsigned integer)
This is the stream number for which a limit is to be enforced.
Message Limit n : 16 bits (unsigned integer)
This is the limit (in messages) that the receiver (sending the
chunk) is requesting that the sender (receiver of the chunk)
enforce as the maximum number of outstanding messages permitted at
any time on this stream, as per the rules in Section 4.5. Note
that the value '0' holds a special meaning described in Section
4.5.1.
Valid Chunk Appearance
The Stream Message Limit Change parameter may appear in the ASCONF
chunk, the INIT, or the INIT-ACK chunk type. The inclusion of this
parameter in the INIT or INIT-ACK can be used to indicate initial
stream message limits.
3.2.8 Association Message Limit Change
0 1 2 3 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 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 =0xC008 | Length = 8 | | Type =0xC006 | Length = Variable |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Association Message Limit | | Reserved Bit Fields |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Association Message Limit n : 32 bits (unsigned integer) This parameter is specified for the communication of peer upper
layer protocols. It is envisioned to be used for flow control
This is the limit (in messages) that the receiver (sending the and other adaption layers that require an indication to be
chunk) is requesting that the sender (receiver of the chunk) carried in the INITand INIT-ACK. Each adaption layer that
enforce as the maximum number of outstanding messages permitted at is defined that wishes to use this parameter MUST specify
any time on the association, as per the rules in Section 4.6. a bit int the reserved bit field in an appropriate RFC. This
Note that the value 0 holds a special meaning described in Section parameter SHOULD NOT be examined by the receiving SCTP
4.5.1 implementation and should be passed opaquely to the upper
layer protocol.
Valid Chunk Appearance Valid Chunk Appearance
The Association Message Limit Change parameter may appear in the The Adaption Layer Indication parameter may appear in INIT or
ASCONF Chunk, the INIT, or the INIT-ACK chunk type. The inclusion INIT-ACK chunk and SHOULD be passed to the receivers upper layer
of this parameter in the INIT or INIT-ACK can be used to indicate protocol.
an initial association message limit.
3.3 New Error Causes 3.3 New Error Causes
Three new Error Causes are added to the SCTP Operational Errors, Three new Error Causes are added to the SCTP Operational Errors,
primarily for use in the ASCONF-ACK chunk. primarily for use in the ASCONF-ACK chunk.
Cause Code Cause Code
Value Cause Code Value Cause Code
--------- ---------------- --------- ----------------
0xC Request to Delete Last Remaining IP Address. 0xC Request to Delete Last Remaining IP Address.
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present for the parameter. present for the parameter.
A8) If there is no response(s) to specific TLV parameter(s), and no A8) If there is no response(s) to specific TLV parameter(s), and no
failures are indicated, then all request(s) are considered failures are indicated, then all request(s) are considered
successful. successful.
If the T-4 RTO timer expires the endpoint should do the following: If the T-4 RTO timer expires the endpoint should do the following:
B1) Increment the error counters and perform path failure detection B1) Increment the error counters and perform path failure detection
on the appropriate destination address as defined in [RFC2960] on the appropriate destination address as defined in [RFC2960]
section 8.1 and 8.2. Note error counters include the per destination section 8.1 and 8.2.
error counter as well as the overall association error counter.
B2) Increment the association error counters and perform endpoint B2) Increment the association error counters and perform endpoint
failure detection on the association as defined in [RFC2960] section failure detection on the association as defined in [RFC2960] section
8.1 and 8.2. Note error counters include the per destination 8.1 and 8.2.
error counter as well as the overall association error counter.
B3) Back-off the destination address RTO timer to which the ASCONF B3) Back-off the destination address RTO value to which the ASCONF
chunk was sent by doubling the RTO timer value. chunk was sent by doubling the RTO timer value.
Note: The RTO value is used in the setting of all timer types
for SCTP. Each destination address a single RTO estimate.
B4) Re-transmit the ASCONF Chunk last sent and if possible choose an B4) Re-transmit the ASCONF Chunk last sent and if possible choose an
alternate destination address (please refer to [RFC2960] section alternate destination address (please refer to [RFC2960] section
6.4.1). An endpoint MUST NOT add new parameters to this chunk, it 6.4.1). An endpoint MUST NOT add new parameters to this chunk, it
MUST be the same (including its serial number) as the last ASCONF MUST be the same (including its serial number) as the last ASCONF
sent. sent.
B5) Restart the T-4 RTO timer. Note that if a different destination is B5) Restart the T-4 RTO timer. Note that if a different destination is
selected, then the RTO used will be that of the new destination selected, then the RTO used will be that of the new destination
address. address.
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wait until the ASCONF-ACK Chunk returns from the previous ASCONF wait until the ASCONF-ACK Chunk returns from the previous ASCONF
Chunk before sending a subsequent ASCONF. Note this restriction Chunk before sending a subsequent ASCONF. Note this restriction
binds each side, so at any time two ASCONF may be in-transit on any binds each side, so at any time two ASCONF may be in-transit on any
given association (one sent from each endpoint). given association (one sent from each endpoint).
R2) A ASCONF MUST NOT be sent if there is no room in the current R2) A ASCONF MUST NOT be sent if there is no room in the current
cwnd. If there is room in the cwnd of the destination network, the cwnd. If there is room in the cwnd of the destination network, the
Chunk may be sent regardless of the value of rwnd. Chunk may be sent regardless of the value of rwnd.
R3) A ASCONF may be bundled with any other chunk type (except other R3) A ASCONF may be bundled with any other chunk type (except other
ASCONF Chunks) as long as the source address in the IP header of ASCONF Chunks).
the packet is already a part of the association. If the ASCONF
chunk is using an alternate source address as the source in
the IP header, then NO other chunks may be bundled with the ASCONF
chunk.
R4) A ASCONF-ACK may be bundled with any other chunk type except R4) A ASCONF-ACK may be bundled with any other chunk type except
other ASCONF-ACKs. other ASCONF-ACKs.
R5) Both ASCONF and ASCONF-ACK chunks MUST NOT be sent in any SCTP R5) Both ASCONF and ASCONF-ACK chunks MUST NOT be sent in any SCTP
state except ESTABLISHED. state except ESTABLISHED.
R6) An ASCONF MUST NOT be larger than the path MTU of the destination. R6) An ASCONF MUST NOT be larger than the path MTU of the destination.
R7) An ASCONF-ACK SHOULD not be larger than the path MTU. In some R7) An ASCONF-ACK SHOULD not be larger than the path MTU. In some
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4.2 Upon reception of an ASCONF Chunk. 4.2 Upon reception of an ASCONF Chunk.
When an endpoint receives an ASCONF Chunk from the remote peer When an endpoint receives an ASCONF Chunk from the remote peer
special procedures MAY be needed to identify the association special procedures MAY be needed to identify the association
the ASCONF Chunk is associated with. To properly find the the ASCONF Chunk is associated with. To properly find the
association the following procedures should be followed: association the following procedures should be followed:
L1) Use the source address and port number of the sender to L1) Use the source address and port number of the sender to
attempt to identify the association (i.e. use the same method attempt to identify the association (i.e. use the same method
defined in [RFC2960] used for all other SCTP chunks ). If found defined in [RFC2960] used for all other SCTP chunks ). If found
proceed to rule L5. proceed to rule L4.
L2) If the association is not found, use the address found L2) If the association is not found, use the address found
in the Address Bytes field combined with the port number in the Address Bytes field combined with the port number
found in the SCTP common header. If found proceed to rule found in the SCTP common header. If found proceed to rule
L4. L4.
L3) If neither L1 or L2 locates the association, treat L3) If neither L1 or L2 locates the association, treat
the chunk as an Out Of The Blue chunk as defined in the chunk as an Out Of The Blue chunk as defined in
[RFC2960]. [RFC2960].
L4) Verify that no other chunk is bundled with the ASCONF L4) Follow the normal rules to validate the SCTP verification
chunk. If other chunks are bundled with the ASCONF Chunk
then the receiver MUST silently discard the ASCONF chunk.
L5) Follow the normal rules to validate the SCTP verification
tag found in [RFC2960]. tag found in [RFC2960].
After identification and verification of the association, After identification and verification of the association,
the following should be performed to properly process the ASCONF Chunk: the following should be performed to properly process the ASCONF Chunk:
C1) Compare the value of the serial number to the value the endpoint C1) Compare the value of the serial number to the value the endpoint
stored in a new association variable 'Peer-Serial-Number'. This stored in a new association variable 'Peer-Serial-Number'. This
value MUST be initialized to the Initial TSN value minus 1. value MUST be initialized to the Initial TSN value minus 1.
C2) If the value found in the serial number is equal to the the C2) If the value found in the serial number is equal to the
('Peer-Serial-Number' + 1), the endpoint should: ('Peer-Serial-Number' + 1), the endpoint MUST:
V1) Process the TLVs contained within the Chunk performing the V1) Process the TLVs contained within the Chunk performing the
appropriate actions as indicated by each TLV type. The TLVs MUST appropriate actions as indicated by each TLV type. The TLVs MUST
be processed in order within the Chunk. For example, if the sender be processed in order within the Chunk. For example, if the sender
puts 3 TLVs in one chunk, the first TLV (the one closest to the puts 3 TLVs in one chunk, the first TLV (the one closest to the
Chunk Header) in the Chunk MUST be processed first. The next TLV in Chunk Header) in the Chunk MUST be processed first. The next TLV in
the chunk (the middle one) MUST be processed second and finally the the chunk (the middle one) MUST be processed second and finally the
last TLV in the Chunk MUST be processed last. last TLV in the Chunk MUST be processed last.
V2) In processing the chunk, the receiver should build a response V2) In processing the chunk, the receiver should build a response
message with the appropriate error TLVs, as specified in the message with the appropriate error TLVs, as specified in the
Parameter type bits for any ASCONF Parameter it does not understand. Parameter type bits for any ASCONF Parameter it does not understand.
To indicate an unrecognized parameter, parameter type 8 as defined To indicate an unrecognized parameter, cause type 8 as defined
in in the INIT-ACK in 3.3.3 of [RFC2960] should be used. The in in the INIT-ACK in 3.3.10.8 of [RFC2960] should be used. The
endpoint may also use the response to carry rejections for other endpoint may also use the response to carry rejections for other
reasons such as resource shortages etc using the Error Cause TLV and reasons such as resource shortages etc using the Error Cause TLV and
an appropriate error condition. an appropriate error condition.
Note: a positive response is implied if no error is indicated by the Note: a positive response is implied if no error is indicated by the
sender. sender.
V3) All error responses MUST copy the ASCONF-Request Correlation ID V3) All error responses MUST copy the ASCONF-Request Correlation ID
field received in the ASCONF, from the TLV being responded to, into field received in the ASCONF, from the TLV being responded to, into
the ASCONF-Request Correlation ID field. The ASCONF-Request the ASCONF-Request Correlation ID field. The ASCONF-Request
skipping to change at page 18, line 15 skipping to change at page 16, line 5
C5) In both cases C2 and C3 the ASCONF-ACK MUST be sent back to the C5) In both cases C2 and C3 the ASCONF-ACK MUST be sent back to the
source address contained in the IP header of the ASCONF being source address contained in the IP header of the ASCONF being
responded to. responded to.
4.3 General rules for address manipulation 4.3 General rules for address manipulation
When building TLV parameters for the ASCONF Chunk that When building TLV parameters for the ASCONF Chunk that
will add or delete IP addresses the following rules should be will add or delete IP addresses the following rules should be
applied: applied:
D0) If an endpoint receives an ASCONF-ACK but no ASCONF chunk
is outstanding AND the sequence number of the ASCONF-ACK matches
what WOULD be the next sequence number sent by the endpoint
the endpoint MUST abort the association.
D1) When adding an IP address to an association, the IP address is D1) When adding an IP address to an association, the IP address is
NOT considered fully added to the association until the ASCONF-ACK NOT considered fully added to the association until the ASCONF-ACK
arrives. This means that until such time as the ASCONF containing arrives. This means that until such time as the ASCONF containing
the add is acknowledged the sender MUST NOT use the new IP address the add is acknowledged the sender MUST NOT use the new IP address
as a source for ANY SCTP chunks besides an ASCONF Chunk. as a source for ANY SCTP packet except on carrying an ASCONF chunk.
The receiver of the add IP address request may use the The receiver of the add IP address request may use the
address as a destination immediately. address as a destination immediately.
D2) After the ASCONF-ACK of an IP address add arrives, the D2) After the ASCONF-ACK of an IP address add arrives, the
endpoint MAY begin using the added IP address as a source endpoint MAY begin using the added IP address as a source
address for any type of SCTP chunk. address for any type of SCTP chunk.
D3a) If an endpoint receives an Error Cause TLV indicating that the D3a) If an endpoint receives an Error Cause TLV indicating that the
IP address Add or IP address Deletion parameters was not understood, IP address Add or IP address Deletion parameters was not understood,
the endpoint MUST consider the operation failed and MUST NOT attempt the endpoint MUST consider the operation failed and MUST NOT attempt
skipping to change at page 18, line 49 skipping to change at page 16, line 44
SCTP packets until the ASCONF-ACK arrives and MUST NOT be used as a SCTP packets until the ASCONF-ACK arrives and MUST NOT be used as a
source address for any subsequent packets. This means that any source address for any subsequent packets. This means that any
datagrams that arrive before the ASCONF-ACK destined to the IP address datagrams that arrive before the ASCONF-ACK destined to the IP address
being deleted MUST be considered part of the current being deleted MUST be considered part of the current
association. One special consideration is that ABORT chunks arriving association. One special consideration is that ABORT chunks arriving
destined to the IP address being deleted MUST be ignored (see destined to the IP address being deleted MUST be ignored (see
Section 4.3.1 for further details). Section 4.3.1 for further details).
D5) An endpoint MUST NOT delete its last remaining IP address from an D5) An endpoint MUST NOT delete its last remaining IP address from an
association. In other words if an endpoint is NOT multi-homed it association. In other words if an endpoint is NOT multi-homed it
MUST NOT use the delete IP address. Or if an endpoint sends multiple MUST NOT use the delete IP address without an add IP address preceding
requests to delete IP addresses it MUST NOT delete all of the IP the delete parameter in the ASCONF chunk. Or if an endpoint sends
addresses that the peer has listed for the requester. multiple requests to delete IP addresses it MUST NOT delete all
of the IP addresses that the peer has listed for the requester.
D6) An endpoint MUST NOT set a IP header source address for an SCTP D6) An endpoint MUST NOT set a IP header source address for an SCTP
packet holding the ASCONF Chunk to be the same as an address being packet holding the ASCONF Chunk to be the same as an address being
deleted by the ASCONF Chunk. deleted by the ASCONF Chunk.
D7) If a request is received to delete the last remaining IP address D7) If a request is received to delete the last remaining IP address
of a peer endpoint, the receiver MUST send an Error Cause TLV with of a peer endpoint, the receiver MUST send an Error Cause TLV with
the error cause set to the new error code 'Request to Delete Last the error cause set to the new error code 'Request to Delete Last
Remaining IP Address'. The requested delete MUST NOT be performed or Remaining IP Address'. The requested delete MUST NOT be performed or
acted upon, other than to send the ASCONF-ACK. acted upon, other than to send the ASCONF-ACK.
skipping to change at page 19, line 29 skipping to change at page 17, line 23
D9) If an endpoint receives an ADD IP address request and does not D9) If an endpoint receives an ADD IP address request and does not
have the local resources to add this new address to the association, have the local resources to add this new address to the association,
it MUST return an Error Cause TLV set to the new error code it MUST return an Error Cause TLV set to the new error code
'Operation Refused Due to Resource Shortage'. 'Operation Refused Due to Resource Shortage'.
D10) If an endpoint receives an 'Out of Resource' error in response D10) If an endpoint receives an 'Out of Resource' error in response
to its request to ADD an IP address to an association, it must to its request to ADD an IP address to an association, it must
either ABORT the association or not consider the address part of the either ABORT the association or not consider the address part of the
association. In other words if the endpoint does not ABORT the association. In other words if the endpoint does not ABORT the
association, it must consider the add attempt failed and NOT use association, it must consider the add attempt failed and NOT use
this address and treat SCTP packets destined to the address as Out this address since its peer will treat SCTP packets destined to
Of The Blue packets. the address as Out Of The Blue packets.
D11) When an endpoint receiving an ASCONF to add an IP address sends D11) When an endpoint receiving an ASCONF to add an IP address sends
an 'Out of Resource' in its response, it MUST also fail any an 'Out of Resource' in its response, it MUST also fail any
subsequent add or delete requests bundled in the ASCONF. The subsequent add or delete requests bundled in the ASCONF. The
receiver MUST NOT reject an ADD and then accept a subsequent DELETE receiver MUST NOT reject an ADD and then accept a subsequent DELETE
of an IP address in the same ASCONF Chunk. In other words, once a of an IP address in the same ASCONF Chunk. In other words, once a
receiver begins failing any ADD or DELETE request, it must fail all receiver begins failing any ADD or DELETE request, it must fail all
subsequent ADD or DELETE requests contained in that single ASCONF. subsequent ADD or DELETE requests contained in that single ASCONF.
D12) When an endpoint receives a request to delete an IP address D12) When an endpoint receives a request to delete an IP address
skipping to change at page 21, line 26 skipping to change at page 19, line 20
4.3.2 A special case for changing an address. 4.3.2 A special case for changing an address.
In some instances the sender may only have one IP address in an In some instances the sender may only have one IP address in an
association that is being renumbered. When this occurs, the sender association that is being renumbered. When this occurs, the sender
may not be able to send to the peer the appropriate ADD/DELETE pair may not be able to send to the peer the appropriate ADD/DELETE pair
and use the old address as a source in the IP header. For this and use the old address as a source in the IP header. For this
reason the sender MUST fill in the Address Bytes field with an reason the sender MUST fill in the Address Bytes field with an
address that is part of the association (in this case the one being address that is part of the association (in this case the one being
deleted). This will allow the receiver to locate the association deleted). This will allow the receiver to locate the association
without using the source address found in the IP header. Such without using the source address found in the IP header.
an SCTP packet MUST NOT be bundled with any other chunk.
The receiver of such an ASCONF chunk MUST NOT process the The receiver of such a chunk MUST always first use the source address
SCTP packet if any other chunks are contained inside the SCTP
packet. The receiver MUST always first use the source address
found in the IP header in looking up the association. The found in the IP header in looking up the association. The
receiver should attempt to use the address found in the Address receiver should attempt to use the address found in the Address
Bytes field only if the lookup fails using the source address from Bytes field only if the lookup fails using the source address from
the IP header. The receiver MUST NOT reply to the source address the IP header. The receiver MUST reply to the source address
of the packet in this special case, but to the new address that of the packet in this case which is the new address that
was added by the ASCONF (since the old address is no longer a part was added by the ASCONF (since the old address is no longer a part
of the association after processing). of the association after processing).
4.4 Setting of the primary address 4.4 Setting of the primary address
A sender of this option may elect to send this combined with A sender of this option may elect to send this combined with
a deletion or addition of an address. A sender SHOULD only send a deletion or addition of an address. A sender SHOULD only send
a set primary request to an address that is already considered a set primary request to an address that is already considered
part of the association. In other words if a sender combines part of the association. In other words if a sender combines
a set primary with an add of a new IP address the set primary a set primary with an add of a new IP address the set primary
will be discarded unless the add request is to be processed will be discarded unless the add request is to be processed
BEFORE the set primary (i.e. it precedes the set primary). BEFORE the set primary (i.e. it precedes the set primary).
A request to set primary MAY also appear in a INIT or INIT-ACK A request to set primary MAY also appear in a INIT or INIT-ACK
chunk. This can give advice to the peer endpoint as to which chunk. This can give advice to the peer endpoint as to which
of its addresses the sender of the INIT or INIT-ACK would like of its addresses the sender of the INIT or INIT-ACK would prefer
to be used as the primary address. to be used as the primary address.
The request to set an address as the primary path is an option the The request to set an address as the primary path is an option the
receiver SHOULD perform. It is considered advice to the receiver of receiver SHOULD perform. It is considered advice to the receiver of
the best destination address to use in sending SCTP packets (in the the best destination address to use in sending SCTP packets (in the
requester's view). If a request arrives that asks the receiver to requester's view). If a request arrives that asks the receiver to
set an address as primary that does not exist, the receiver should set an address as primary that does not exist, the receiver should
NOT honor the request, leaving its existing primary address NOT honor the request, leaving its existing primary address
unchanged. unchanged.
4.5 Stream Flow Limit and Message Limit Procedures
A stream in SCTP is an uni-directional logical channel established
from one to another associated SCTP endpoint, within which all user
messages are delivered in sequence except for those submitted to the
un-ordered delivery service which may arrive out of sequence. Since
each stream is uni-directional and no feedback mechanism exists to
limit a sender, it is possible for one unique stream to monopolize
all of the transport level receiver window space. The mechanism
defined here attempts to alleviate this problem by allowing the
receiver side to communicate to the sender a limit on how much
outstanding data may be sent within a particular stream.
The procedures defined here are broken down into two sides:
o The stream receiver side or peer requesting the limit. And,
o the stream sender side or peer that MUST honor the limit request.
The receiver's side is mainly involved with sending the request to
the peer. The sender's side is where the actual flow or message
limit will be enforced. Note that the stream receiver is the
endpoint that sends the ASCONF, INIT or INIT-ACK message (see
Section 4.5.1), whereas the stream sender is the endpoint that
receives the ASCONF, INIT or INIT-ACK message (see Section 4.5.2).
4.5.1 Stream receiver side procedures
The receiver side SCTP requests byte or message limits in response
to an upper layer request. An upper layer may request, via an API
interface, that a byte or message limit be imposed on all or a
subset of the active streams that send data to the upper layer
receiver, or that a message limit be imposed on the association.
The basis on which the upper layer determines these limits is
outside the scope of this document.
Any time during an association that limits are requested of the SCTP
endpoint by the upper layer, the receiver side SHOULD create an
ASCONF Chunk and attach to a Stream Flow Limit Change, Stream
Message Limit Change, or Association Message Limit Change parameter
as appropriate. These parameter types MAY also be placed in an INIT
or INIT-ACK chunk at the beginning of an association to request
initial values for the appropriate limits.
The Stream Flow Limit Change and Stream Message Limit Changes
parameters contain a sequence of one or more pairs, each of which
consists of a specific stream number, and a byte or message limit
to be applied to that stream.
If the receiver wishes to remove the flow limit or message limit
for a specific stream, it may do so by placing the special value
'0' in the Flow Limit or Message Limit field. Once acknowledged
by the peer endpoint the receiver should consider the limit in
place.
In the case of flow or message limits contained within an INIT
chunk, any such limit is considered acknowledged with the arrival of
the INIT-ACK, provided that the peer indicates that it understands
the requested limit by NOT placing an 'unrecognized parameter' error
in the INIT-ACK.
Similarly, for flow or message limits contained within an INIT-ACK
chunk, any such limit is considered acknowledged with the arrival of
the cookie, provided that the peer indicates that it understands the
requested limit by NOT placing an 'unrecognized parameter' error in
the cookie.
To send initial limits, ASCONF chunks are NOT bundled with the INIT
or INIT-ACK. Instead the TLV is added to the variable parameters
section of the INIT or INIT-ACK.
Note that the parameter type field upper two bits dictates that any
parameter not understood should be skipped and reported to the
sender with an Operational Error. With this in mind we make the
following rules for the sender of the request:
Z1) If an Operational Error is received that indicates that the
'Stream Byte Limit Request' is not understood, the sender of the
limit request MUST not send subsequent limit requests. The
endpoint SHOULD also inform the upper layer application that
the peer endpoint does not support this feature.
Z2) If an Operational Error is received that indicates that the
'Stream Message Limit Request' is not understood, the sender of
the limit request MUST not send subsequent limit requests. The
endpoint SHOULD also inform the upper layer application that the
peer endpoint does not support this feature.
4.5.2 Stream Sender side procedures
When a 'Stream Byte Limit Request' or 'Stream Message Limit
Request' is received the sender MUST record each limit with its
appropriate stream.
After a limit is set on a stream the sender MUST obey the following
rules when sending to the peer on that stream:
S1) When the upper layer application attempts to send to the peer on
a stream, check
- the number of outstanding bytes sent to that stream
(those TSNs in queue to be sent, which the Cumulative TSN
Acknowledgment has not passed, on this stream) versus the limit set
for that stream (The last received limit for this stream is
henceforth termed the current limit).
- the number of outstanding messages sent on that stream (for which
not all TSNs are passed by the Cumulative TSN Acknowledgment)
versus the limit for this stream.
S2a) If the number of outstanding bytes is greater than or equal to
the current limit, the SCTP endpoint MUST reject the request and NOT
queue the data for transmit. Instead it SHOULD return an error
to the sending application.
S2b) If the number of outstanding messages is greater or equal to
the current limit, the SCTP endpoint MUST reject the request and NOT
queue the data for transmit. Instead it SHOULD return an error
to the sending application.
S3a) If the number of outstanding bytes is less than the current
limit, validate that the data to be sent plus the number of
outstanding bytes is smaller than or equal to this limit. If the
user data plus the number of outstanding bytes is smaller than or
equal to the current limit accept the data for transmit and queue
the user data (increasing the number of outstanding data bytes on
this stream). If the user data plus the number of outstanding bytes
is larger than the current limit for this stream, the SCTP endpoint
MUST reject the request and NOT queue the data for transmit and
instead SHOULD return an error to the application.
S3b) If the number of outstanding messages is less than the current
limit, accept the data for transmit and queue the user data
(increasing the number of outstanding messages on this stream).
S4) Any time a stream limit is updated to the value of 0, consider
this indication to mean no limit is in effect for this stream.
S5) Any stream number NOT mentioned in a limit request MUST be left
unchanged. In other words failure to mention a stream in a
limit request leaves the un-mentioned stream unchanged.
S6) If a stream limit is reduced and the stream already exceeds
the stream limit, no changes are made with respect to the
outstanding data. New data request MUST be rejected however,
until the streams limit will allow the sending of data (rules
S2 and S3 above).
NOTE: Stream limits do NOT change the underlying SCTP rwnd and
its usage as defined in [RFC2960]. The association MUST still
honor the rwnd when sending to the peer endpoint as defined in
[RFC2960].
4.5.3 ULP considerations on the use of SCTP flow limit facility
A side-effect of rule S3 in section 4.5.2 is that an upper limit
is imposed on the size of messages that may be sent to any stream
where a flow limit is in place. Once a flow limit is in effect,
if the sending Upper Layer Protocol (ULP) wishes to send a message
that is larger than that permitted by the imposed stream limit,
the ULP will need to provide a mechanism for fragmentation and
re-assembly.
This ULP mechanism is in addition to any fragmentation and
re-assembly that may be provided by SCTP. It is the sole
responsibility of the ULP to handle the case of a single user
message being larger than the stream byte limit, if applicable.
4.6 Association Message Limit Procedures
Using the stream flow/message limit functionality described
in 4.5 it is possible for a receiver to limit the sender in
a way the receiver thinks is appropriate. For an overall
(per association) byte based limit the receiver can make use
of the rwnd field in SACK-chunks.
An overall message based limit is provided by the 'Association
Message Limit Request'. This can be useful to make better use of
message oriented pools (e.g. mbufs) and to limit the delivery time
for messages.
The procedures defined here are broken down into two sides:
o The receiver side or peer requesting the limit. And,
o the sender side or peer that MUST honor the limit request.
The receiver's side is mainly involved with sending the request to
the peer. The sender's side is where the actual limitations and flow
message limit will occur. Note in section 4.6.1 the receiver
is the endpoint that sends the ASCONF, INIT or INIT-ACK message, in
section 4.6.2 the sender side is the endpoint that receives
the ASCONF, INIT or INIT-ACK message.
4.6.1 Receiver side procedures
The same rules as given in 4.5.1 for the stream limits apply to the
association limit.
4.6.2 Sender side procedures
When an 'Association Message Limit Request' is received the sender MUST
record this limit for the association.
After a limit is set for the association the sender MUST obey the
following rules when sending to the peer on that stream:
S1) When the upper layer application attempts to send to the peer on
a stream, check the number of outstanding messages sent on the
association (for which not all TSNs are passed by the Cumulative TSN
Acknowledgment) versus the limit for this association.
S2) If the number of outstanding messages is greater or equal to
the current limit, the SCTP endpoint MUST reject the request and NOT
queue the data for transmit. Instead it SHOULD return an error
to the sending application.
S3) If the number of outstanding messages is less than the current
limit, accept the data for transmit and queue the user data
(increasing the number of outstanding messages on this association).
S4) Any time the association limit is updated to the value of 0,
consider this indication to mean no limit is in effect for the
Association.
5. Security Considerations 5. Security Considerations
The ADD/DELETE of an IP address to an existing association does The ADD/DELETE of an IP address to an existing association does
provide an additional mechanism by which existing associations can provide an additional mechanism by which existing associations can
be hijacked. Where the attacker is able to intercept and or alter be hijacked. Where the attacker is able to intercept and or alter
the packets sent and received in an association, the use of this the packets sent and received in an association, the use of this
feature MAY increase the ease with which an association may be feature MAY increase the ease with which an association may be
overtaken. This threat SHOULD be considered when deploying a version overtaken. This threat SHOULD be considered when deploying a version
of SCTP that makes use of this feature. The IP Authentication Header of SCTP that makes use of this feature. The IP Authentication Header
[RFC2402] SHOULD be used when the threat environment requires [RFC2402] SHOULD be used when the threat environment requires
skipping to change at page 26, line 40 skipping to change at page 20, line 23
specification [RFC2960], if an attacker is able to intercept and or specification [RFC2960], if an attacker is able to intercept and or
alter packets, even without this feature it is possible to hijack an alter packets, even without this feature it is possible to hijack an
existing association; please refer to Section 11 of RFC2960. existing association; please refer to Section 11 of RFC2960.
6. IANA considerations 6. IANA considerations
This document defines the following new SCTP parameters, chunks This document defines the following new SCTP parameters, chunks
and errors: and errors:
- Two new chunk types, - Two new chunk types,
- Eight parameter types, and - Six parameter types, and
- Three new SCTP error causes. - Three new SCTP error causes.
7. Acknowledgments 7. Acknowledgments
The authors wish to thank Jon Berger, John Loughney, Ivan Arias The authors wish to thank Maria-Carmen Belinchon, Jon Berger,
Rodriguez, Marshall Rose, and Chip Sharp for their invaluable Peter Lei, John Loughney, Ivan Arias Rodriguez, Renee Revis,
comments. Marshall Rose, and Chip Sharp for their invaluable comments.
8. Authors' Addresses 8. Authors' Addresses
Randall R. Stewart Tel: +1-815-477-2127 Randall R. Stewart Tel: +1-815-477-2127
Cisco Systems, Inc. EMail: rrs@cisco.com Cisco Systems, Inc. EMail: rrs@cisco.com
8745 W. Higgins Road, Suite 200 8745 W. Higgins Road, Suite 200
Chicago, Ill 60631 Chicago, Ill 60631
USA USA
Micheal A. Ramalho Tel: +1-732-809-0188 Micheal A. Ramalho Tel: +1-732-809-0188
 End of changes. 

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