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Versions: 00 01 02 03 04 05 06 07 08 09 10 11
12 13 14 15 16 17 18 19 20 21 22 RFC 5061
Network Working Group R. Stewart
Internet-Draft M. Ramalho
Expires: December 2, 2006 Cisco Systems, Inc.
Q. Xie
Motorola, Inc.
M. Tuexen
Univ. of Applied Sciences Muenster
P. Conrad
University of Delaware
May 31, 2006
Stream Control Transmission Protocol (SCTP) Dynamic Address
Reconfiguration
draft-ietf-tsvwg-addip-sctp-15.txt
Status of this Memo
By submitting this Internet-Draft, each author represents that any
applicable patent or other IPR claims of which he or she is aware
have been or will be disclosed, and any of which he or she becomes
aware will be disclosed, in accordance with Section 6 of BCP 79.
Internet-Drafts are working documents of the Internet Engineering
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other groups may also distribute working documents as Internet-
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material or to cite them other than as "work in progress."
The list of current Internet-Drafts can be accessed at
http://www.ietf.org/ietf/1id-abstracts.txt.
The list of Internet-Draft Shadow Directories can be accessed at
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This Internet-Draft will expire on December 2, 2006.
Copyright Notice
Copyright (C) The Internet Society (2006).
Abstract
This document describes extensions to the Stream Control Transmission
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Protocol (SCTP) [RFC2960] that provides a method to reconfigure IP
address information on an existing association.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
2. Conventions . . . . . . . . . . . . . . . . . . . . . . . . . 4
3. Additional Chunks and Parameters . . . . . . . . . . . . . . . 4
3.1. New Chunk Types . . . . . . . . . . . . . . . . . . . . . 5
3.1.1. Address Configuration Change Chunk (ASCONF) . . . . . 5
3.1.2. Address Configuration Acknowledgment Chunk
(ASCONF-ACK) . . . . . . . . . . . . . . . . . . . . . 6
3.2. New Parameter Types . . . . . . . . . . . . . . . . . . . 7
3.2.1. Add IP Address . . . . . . . . . . . . . . . . . . . . 8
3.2.2. Delete IP Address . . . . . . . . . . . . . . . . . . 9
3.2.3. Error Cause Indication . . . . . . . . . . . . . . . . 10
3.2.4. Set Primary IP Address . . . . . . . . . . . . . . . . 11
3.2.5. Success Indication . . . . . . . . . . . . . . . . . . 12
3.2.6. Adaptation Layer Indication . . . . . . . . . . . . . 13
3.2.7. Supported Extensions Parameter . . . . . . . . . . . . 13
3.3. New Error Causes . . . . . . . . . . . . . . . . . . . . . 14
3.3.1. Error Cause: Request to Delete Last Remaining IP
Address . . . . . . . . . . . . . . . . . . . . . . . 14
3.3.2. Error Cause: Operation Refused Due to Resource
Shortage . . . . . . . . . . . . . . . . . . . . . . . 15
3.3.3. Error Cause: Request to Delete Source IP Address . . . 16
3.3.4. Error Cause: Association Aborted due to illegal
ASCONF-ACK . . . . . . . . . . . . . . . . . . . . . . 17
3.3.5. Error Cause: Request refused - no authorization. . . . 17
4. Procedures . . . . . . . . . . . . . . . . . . . . . . . . . . 18
4.1. ASCONF Chunk Procedures . . . . . . . . . . . . . . . . . 18
4.1.1. Congestion Control of ASCONF Chunks . . . . . . . . . 19
4.2. Upon reception of an ASCONF Chunk. . . . . . . . . . . . . 20
4.3. General rules for address manipulation . . . . . . . . . . 22
4.3.1. A special case for OOTB ABORT chunks . . . . . . . . . 25
4.3.2. A special case for changing an address. . . . . . . . 26
4.4. Setting of the primary address . . . . . . . . . . . . . . 26
5. Security Considerations . . . . . . . . . . . . . . . . . . . 27
6. IANA considerations . . . . . . . . . . . . . . . . . . . . . 28
7. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 28
8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 29
Appendix A. Abstract Address Handling . . . . . . . . . . . . . . 29
A.1. General remarks . . . . . . . . . . . . . . . . . . . . . 29
A.2. Generalized endpoints . . . . . . . . . . . . . . . . . . 29
A.3. Associations . . . . . . . . . . . . . . . . . . . . . . . 30
A.4. Relationship with RFC 2960 . . . . . . . . . . . . . . . . 31
A.5. Rules for address manipulation . . . . . . . . . . . . . . 31
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Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 33
Intellectual Property and Copyright Statements . . . . . . . . . . 35
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1. Introduction
To extend the utility and application scenarios of SCTP, this
document introduces optional extensions that provide SCTP with the
ability to:
1. reconfigure IP address information on an existing association.
2. set the remote primary path.
3. exchange adaptation layer information during association setup.
These extensions enable SCTP to be utilized in the following
applications:
1. For computational or networking platforms that allow addition/
removal of physical interface cards this feature can provide a
graceful method to add to the interfaces of an existing
association. For IPv6 this feature allows renumbering of
existing associations.
2. This provides a method for an endpoint to request that its peer
set its primary destination address. This can be useful when an
address is about to be deleted, or when an endpoint has some
predetermined knowledge about which is the preferred address to
receive SCTP packets upon.
3. This feature can be used to extend the usability of SCTP without
modifying it by allowing endpoints to exchange some information
during association setup.
2. Conventions
The keywords MUST, MUST NOT, REQUIRED, SHALL, SHALL NOT, SHOULD,
SHOULD NOT, RECOMMENDED, NOT RECOMMENDED, MAY, and OPTIONAL, when
they appear in this document, are to be interpreted as described in
RFC2119 [RFC2119].
3. Additional Chunks and Parameters
This section describes the addition of two new chunks and, seven new
parameters to allow:
o Dynamic addition of IP Addresses to an association.
o Dynamic deletion of IP Addresses from an association.
o A request to set the primary address the peer will use when
sending to an endpoint.
Additionally, this section describes three new error causes that
support these new chunks and parameters.
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3.1. New Chunk Types
This section defines two new chunk types that will be used to
transfer the control information reliably. Table 1 illustrates the
two new chunk types.
Chunk Type Chunk Name
--------------------------------------------------------------
0xC1 Address Configuration Change Chunk (ASCONF)
0x80 Address Configuration Acknowledgment (ASCONF-ACK)
Table 1: Address Configuration Chunks
It should be noted that the ASCONF Chunk format requires the receiver
to report to the sender if it does not understand the ASCONF Chunk.
This is accomplished by setting the upper bits in the chunk type as
described in RFC2960 [RFC2960] section 3.2. Note that the upper two
bits in the ASCONF Chunk are set to one. As defined in RFC2960
[RFC2960] section 3.2, setting these upper bits in this manner will
cause the receiver that does not understand this chunk to skip the
chunk and continue processing, but report in an Operation Error Chunk
using the 'Unrecognized Chunk Type' cause of error.
3.1.1. Address Configuration Change Chunk (ASCONF)
This chunk is used to communicate to the remote endpoint one of the
configuration change requests that MUST be acknowledged. The
information carried in the ASCONF Chunk uses the form of a Type-
Length-Value (TLV), as described in "3.2.1 Optional/Variable-length
Parameter Format" in RFC2960 [RFC2960], for all variable parameters.
This chunk MUST be sent in an authenticated way by using the
mechanism defined in SCTP-AUTH [I-D.ietf-tsvwg-sctp-auth]. If this
chunk is received unauthenticated it MUST be silently discarded as
described in SCTP-AUTH [I-D.ietf-tsvwg-sctp-auth].
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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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type = 0xC1 | Chunk Flags | Chunk Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Serial Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Address Parameter |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ASCONF Parameter #1 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
\ \
/ .... /
\ \
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ASCONF Parameter #N |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Serial Number : 32 bits (unsigned integer)
This value represents a Serial Number for the ASCONF Chunk. The
valid range of Serial Number is from 0 to 4294967295 (2**32 - 1).
Serial Numbers wrap back to 0 after reaching 4294967295.
Address Parameter : 8 or 20 bytes (depending on type)
This field contains an address parameter, either IPv6 or IPv4, from
RFC2960 [RFC2960]. The address is an 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 in finding the
association. If the address 0.0.0.0 or ::0 is provided the receiver
MAY lookup the association by other information provided in the
packet. This parameter MUST be present in every ASCONF message i.e.
it is a mandatory TLV parameter.
Note the host name address parameter is NOT allowed and MUST be
ignored if received in any ASCONF message.
ASCONF Parameter: TLV format
Each Address configuration change is represented by a TLV parameter
as defined in Section 3.2. One or more requests may be present in an
ASCONF Chunk.
3.1.2. Address Configuration Acknowledgment Chunk (ASCONF-ACK)
This chunk is used by the receiver of an ASCONF Chunk to acknowledge
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the reception. It carries zero or more results for any ASCONF
Parameters that were processed by the receiver. This chunk MUST be
sent in an authenticated way by using the mechanism defined in SCTP-
AUTH [I-D.ietf-tsvwg-sctp-auth]. If this chunk is received
unauthenticated it MUST be silently discarded as described in SCTP-
AUTH [I-D.ietf-tsvwg-sctp-auth].
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 = 0x80 | Chunk Flags | Chunk Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Serial Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ASCONF Parameter Response#1 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
\ \
/ .... /
\ \
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ASCONF Parameter Response#N |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Serial Number : 32 bits (unsigned integer)
This value represents the Serial Number for the received ASCONF Chunk
that is acknowledged by this chunk. This value is copied from the
received ASCONF Chunk.
ASCONF Parameter Response : TLV format
The ASCONF Parameter Response is used in the ASCONF-ACK to report
status of ASCONF processing. By default, if a responding endpoint
does not include any Error Cause, a success is indicated. Thus a
sender of an 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) and the Serial Number.
3.2. New Parameter Types
The seven new parameters added follow the format defined in section
3.2.1 of RFC2960 [RFC2960]. Table 2, 3 and 4 describes the
parameters.
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Address Configuration Parameters Parameter Type
-------------------------------------------------
Set Primary Address 0xC004
Adaptation Layer Indication 0xC006
Supported Extensions 0x8008
Table 2: Parameters that can be used in INIT/INIT-ACK chunk
Address Configuration Parameters Parameter Type
-------------------------------------------------
Add IP Address 0xC001
Delete IP Address 0xC002
Set Primary Address 0xC004
Table 3: Parameters used in ASCONF Parameter
Address Configuration Parameters Parameter Type
-------------------------------------------------
Error Cause Indication 0xC003
Success Indication 0xC005
Table 4: Parameters used in ASCONF Parameter Response
Any parameter that appears where it is not allowed (for example a
0xC002 parameter appearing within an INIT or INIT-ACK) MAY be
responded to with an ABORT by the receiver of the invalid parameter.
3.2.1. Add IP Address
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 = 0xC001 | Length = Variable |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ASCONF-Request Correlation ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Address Parameter |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
ASCONF-Request Correlation ID: 32 bits
This is an opaque integer assigned by the sender to identify each
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
bit value into the ASCONF Response Correlation ID field of the
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ASCONF-ACK response parameter. The sender of the ASCONF can use this
same value in the ASCONF-ACK to find which request the response is
for.
Address Parameter: TLV
This field contains an IPv4 or IPv6 address parameter as described in
3.3.2.1 of RFC2960 [RFC2960]. The complete TLV is wrapped within
this parameter. It informs the receiver that the address specified
is to be added to the existing association. This parameter MUST NOT
contain a broadcast or multicast address. If the address 0.0.0.0 or
::0 is provided, the source address of the packet MUST be added.
An example TLV requesting that the IPv4 address 10.1.1.1 be added to
the association would look as follows:
+--------------------------------+
| Type=0xC001 | Length = 16 |
+--------------------------------+
| C-ID = 0x01023474 |
+--------------------------------+
| Type=5 | Length = 8 |
+----------------+---------------+
| Value=0x0a010101 |
+----------------+---------------+
Valid Chunk Appearance
The Add IP Address parameter may only appear in the ASCONF Chunk
type.
3.2.2. Delete IP Address
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 =0xC002 | Length = Variable |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ASCONF-Request Correlation ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Address Parameter |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
ASCONF-Request Correlation ID: 32 bits
This is an opaque integer assigned by the sender to identify each
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
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bit value into the ASCONF Response Correlation ID field of the
ASCONF-ACK response parameter. The sender of the ASCONF can use this
same value in the ASCONF-ACK to find which request the response is
for.
Address Parameter: TLV
This field contains an IPv4 or IPv6 address parameter as described in
3.3.2.1 of RFC2960 [RFC2960]. The complete TLV is wrapped within
this parameter. It informs the receiver that the address specified
is to be removed from the existing association. This parameter MUST
NOT contain a broadcast or multicast address. If the address 0.0.0.0
or ::0 is provided, all addresses of the peer except the source
address of the packet MUST be deleted.
An example TLV deleting the IPv4 address 10.1.1.1 from an existing
association would look as follows:
+--------------------------------+
| Type=0xC002 | Length = 16 |
+--------------------------------+
| C-ID = 0x01023476 |
+--------------------------------+
| Type=5 | Length = 8 |
+----------------+---------------+
| Value=0x0a010101 |
+----------------+---------------+
Valid Chunk Appearance
The Delete IP Address parameter may only appear in the ASCONF Chunk
type.
3.2.3. 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 = 0xC003 | Length = Variable |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ASCONF-Response Correlation ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Error Cause(s) or Return Info on Success |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
ASCONF-Response Correlation ID: 32 bits
This is an opaque integer assigned by the sender to identify each
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request parameter. The receiver of the ASCONF Chunk will copy this
32 bit value from the ASCONF-Request Correlation ID into the ASCONF
Response Correlation ID field so the peer can easily correlate the
request to this response.
Error Cause(s): TLV(s)
When reporting an error this response parameter is used to wrap one
or more standard error causes normally found within an SCTP
Operational Error or SCTP Abort (as defined in RFC2960 [RFC2960]).
The Error Cause(s) follow the format defined in section 3.3.10 of
RFC2960 [RFC2960].
Valid Chunk Appearance
The Error Cause Indication parameter may only appear in the ASCONF-
ACK chunk type.
3.2.4. Set Primary IP Address
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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ASCONF-Request Correlation ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Address Parameter |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
ASCONF-Request Correlation ID: 32 bits
This is an opaque integer assigned by the sender to identify each
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
bit value into the ASCONF Response Correlation ID field of the
ASCONF-ACK response parameter. The sender of the ASCONF can use this
same value in the ASCONF-ACK to find which request the response is
for.
Address Parameter: TLV
This field contains an IPv4 or IPv6 address parameter as described in
3.3.2.1 of RFC2960 [RFC2960]. The complete TLV is wrapped within
this parameter. It requests the receiver to mark the specified
address as the primary address to send data to (see section 5.1.2 of
RFC2960 [RFC2960]). The receiver MAY mark this as its primary upon
receiving this request. If the address 0.0.0.0 or ::0 is provided,
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the receiver MAY mark the source address of the packet as its
primary.
An example TLV requesting that the IPv4 address 10.1.1.1 be made the
primary destination address would look as follows:
+--------------------------------+
| Type=0xC004 | Length = 16 |
+--------------------------------+
| C-ID = 0x01023479 |
+--------------------------------+
| Type=5 | Length = 8 |
+----------------+---------------+
| Value=0x0a010101 |
+----------------+---------------+
Valid Chunk Appearance
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 in the INIT or INIT-ACK can be used to indicate an initial
preference of primary address.
3.2.5. Success 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 = 0xC005 | Length = 8 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ASCONF-Response Correlation ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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
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)
and the Serial Number.
The responding endpoint MAY also choose to explicitly report a
success for a requested TLV, by returning a success report ASCONF
Parameter Response.
ASCONF-Response Correlation ID: 32 bits
This is an opaque integer assigned by the sender to identify each
request parameter. The receiver of the ASCONF Chunk will copy this
32 bit value from the ASCONF-Request Correlation ID into the ASCONF
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Response Correlation ID field so the peer can easily correlate the
request to this response.
Valid Chunk Appearance
The Success Indication parameter may only appear in the ASCONF-ACK
chunk type.
3.2.6. Adaptation 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 =0xC006 | Length = 8 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Adaptation Code point |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
This parameter is specified for the communication of peer upper layer
protocols. It is envisioned to be used for flow control and other
adaptation layers that require an indication to be carried in the
INIT and INIT-ACK. Each adaptation layer that is defined that wishes
to use this parameter MUST specify a an adaptation code point in an
appropriate RFC defining its use and meaning. This parameter SHOULD
NOT be examined by the receiving SCTP implementation and should be
passed opaquely to the upper layer protocol.
Valid Chunk Appearance
The Adaptation Layer Indication parameter may appear in INIT or INIT-
ACK chunk and SHOULD be passed to the receivers upper layer protocol.
This parameter MUST NOT appear in a ASCONF chunk.
3.2.7. Supported Extensions Parameter
This parameter is used at startup to identify any additional
extensions that the sender supports. The sender MUST support both
the sending and the receiving of any chunk types listed within the
Supported Extensions Parameter.
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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 = 0x8008 | Parameter Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| CHUNK TYPE 1 | CHUNK TYPE 2 | CHUNK TYPE 3 | CHUNK TYPE 4 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| .... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| CHUNK TYPE N | PAD | PAD | PAD |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Parameter Type This field holds the IANA defined parameter type for
Supported Extensions Parameter. The suggested value of this field
for IANA is 0x8008.
Parameter Type Length This field holds the length of the parameter,
including the Parameter Type, Parameter Length and any addition
supported extensions. Note the length MUST NOT include any
padding.
CHUNK TYPE X This field(s) hold the chunk type of any SCTP
extension(s) that are currently supported by the sending SCTP.
Multiple chunk types may be defined listing each additional
feature that the sender supports. The sender MUST NOT include
multiple Supported Extensions Parameter within any chunk.
Parameter Appearance This parameter may appear in the INIT or INIT-
ACK chunk. This parameter MUST NOT appear in any other chunk.
3.3. New Error Causes
Five new Error Causes are added to the SCTP Operational Errors,
primarily for use in the ASCONF-ACK chunk.
Cause Code
Value Cause Code
--------- ----------------
0x0100 Request to Delete Last Remaining IP Address.
0x0101 Operation Refused Due to Resource Shortage.
0x0102 Request to Delete Source IP Address.
0x0103 Association Aborted due to illegal ASCONF-ACK
0x0104 Request refused - no authorization.
Table 5: New Error Causes
3.3.1. Error Cause: Request to Delete Last Remaining IP Address
Cause of error
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Request to Delete Last Remaining IP address: The receiver of this
error sent a request to delete the last IP address from its
association with its peer. This error indicates that the request is
rejected.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Cause Code=0x0100 | Cause Length=Variable |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
\ TLV-Copied-From-ASCONF /
/ \
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
An example of a failed delete in an Error Cause TLV would look as
follows in the response ASCONF-ACK message:
+--------------------------------+
| Type = 0xC003 | Length = 28 |
+----------------+---------------+
| C-ID = 0x01023476 |
+--------------------------------+
| Cause=0x0100 | Length = 20 |
+----------------+---------------+
| Type= 0xC002 | Length = 16 |
+----------------+---------------+
| C-ID = 0x01023476 |
+--------------------------------+
| Type=0x0005 | Length = 8 |
+----------------+---------------+
| Value=0x0A010101 |
+----------------+---------------+
3.3.2. Error Cause: Operation Refused Due to Resource Shortage
Cause of error
This error cause is used to report a failure by the receiver to
perform the requested operation due to a lack of resources. The
entire TLV that is refused is copied from the ASCONF into the error
cause.
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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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Cause Code=0x0101 | Cause Length=Variable |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
\ TLV-Copied-From-ASCONF /
/ \
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
An example of a failed addition in an Error Cause TLV would look as
follows in the response ASCONF-ACK message:
+--------------------------------+
| Type = 0xC003 | Length = 28 |
+--------------------------------+
| C-ID = 0x01023474 |
+--------------------------------+
| Cause=0x0101 | Length = 20 |
+----------------+---------------+
| Type=0xC001 | Length = 16 |
+--------------------------------+
| C-ID = 0x01023474 |
+--------------------------------+
| Type=0x0005 | Length = 8 |
+----------------+---------------+
| Value=0x0A010101 |
+----------------+---------------+
3.3.3. Error Cause: Request to Delete Source IP Address
Cause of error
Request to Delete Source IP Address: The receiver of this error sent
a request to delete the source IP address of the ASCONF message.
This error indicates that the request is rejected.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Cause Code=0x0102 | Cause Length=Variable |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
\ TLV-Copied-From-ASCONF /
/ \
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
An example of a failed delete in an Error Cause TLV would look as
follows in the response ASCONF-ACK message:
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+--------------------------------+
| Type = 0xC003 | Length = 28 |
+--------------------------------+
| C-ID = 0x01023476 |
+--------------------------------+
| Cause=0x0102 | Length = 20 |
+----------------+---------------+
| Type=0xC002 | Length = 16 |
+----------------+---------------+
| C-ID = 0x01023476 |
+--------------------------------+
| Type=0x0005 | Length = 8 |
+----------------+---------------+
| Value=0x0A010101 |
+----------------+---------------+
IMPLEMENTATION NOTE: It is unlikely that an endpoint would source a
packet from the address being deleted, unless the endpoint does not
do proper source address selection.
3.3.4. Error Cause: Association Aborted due to illegal ASCONF-ACK
This error is to be included in an ABORT that is generated due to the
reception of an ASCONF-ACK that was not expected but is larger than
the current sequence number (see Section 4.3 Rule D0 ). Note that a
sequence number is larger than the last acked sequence number if it
is either the next sequence or no more than 2^^31-1 greater than the
current sequence number.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Cause Code=0x0103 | Cause Length=4 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
3.3.5. Error Cause: Request refused - no authorization.
Cause of error
This error cause may be included to reject a request based on local
security policies.
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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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Cause Code=0x0104 | Cause Length=Variable |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
\ TLV-Copied-From-ASCONF /
/ \
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
4. Procedures
This section will lay out the specific procedures for address
configuration change chunk type and its processing.
4.1. ASCONF Chunk Procedures
When an endpoint has an ASCONF signaled change to be sent to the
remote endpoint it should do the following:
A1) Create an ASCONF Chunk as defined in Section 3.1.1. The chunk
should contain all of the TLV(s) of information necessary to be
sent to the remote endpoint, and unique correlation identities for
each request.
A2) A serial number should be assigned to the Chunk. The serial
number should be a monotonically increasing number. The serial
number MUST be initialized at the start of the association to the
same value as the Initial TSN and every time a new ASCONF chunk is
created it is incremented by one after assigning the serial number
to the newly created chunk .
A3) If no ASCONF Chunk is outstanding (un-acknowledged) with the
remote peer, send the chunk.
A4) Start a T-4 RTO timer, using the RTO value of the selected
destination address (normally the primary path; see RFC2960
[RFC2960] section 6.4 for details).
A5) When the ASCONF-ACK that acknowledges the serial number last sent
arrives, stop the T-4 RTO timer, and clear the appropriate
association and destination error counters as defined in RFC2960
[RFC2960] section 8.1 and 8.2.
A6) Process all of the TLVs within the ASCONF-ACK to find out
particular status information returned to the various requests
that were sent. Use the Correlation IDs to correlate the request
and the responses.
A7) If an error response is received for a TLV parameter, all TLVs
with no response before the failed TLV are considered successful
if not reported. All TLVs after the failed response are
considered unsuccessful unless a specific success indication is
present for the parameter.
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A8) If there is no response(s) to specific TLV parameter(s), and no
failures are indicated, then all request(s) are considered
successful.
A9) If the peer responds to an ASCONF with an ERROR chunk reporting
that it did not recognize the ASCONF chunk type, the sender of the
ASCONF MUST NOT send any further ASCONF chunks and MUST stop its
T-4 timer.
If the T-4 RTO timer expires the endpoint should do the following:
B1) Increment the error counters and perform path failure detection
on the appropriate destination address as defined in RFC2960
[RFC2960] section 8.1 and 8.2.
B2) Increment the association error counters and perform endpoint
failure detection on the association as defined in RFC2960
[RFC2960] section 8.1 and 8.2.
B3) Back-off the destination address RTO value to which the ASCONF
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 has a single RTO estimate.
B4) Re-transmit the ASCONF Chunk last sent and if possible choose an
alternate destination address (please refer to RFC2960 [RFC2960]
section 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 sent.
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
address.
Note: the total number of re-transmissions is limited by B2 above.
If the maximum is reached, the association will fail and enter into
the CLOSED state (see RFC2960 [RFC2960] section 6.4.1 for details).
4.1.1. Congestion Control of ASCONF Chunks
In defining the ASCONF Chunk transfer procedures, it is essential
that these transfers MUST NOT cause congestion within the network.
To achieve this, we place these restrictions on the transfer of
ASCONF Chunks:
R1) One and only one ASCONF Chunk MAY be in transit and
unacknowledged at any one time. If a sender, after sending an
ASCONF chunk, decides it needs to transfer another ASCONF Chunk,
it MUST wait until the ASCONF-ACK Chunk returns from the previous
ASCONF Chunk before sending a subsequent ASCONF. Note this
restriction binds each side, so at any time two ASCONF may be in-
transit on any given association (one sent from each endpoint).
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R2) An ASCONF may be bundled with any other chunk type (except other
ASCONF Chunks).
R3) An ASCONF-ACK may be bundled with any other chunk type except
other ASCONF-ACKs.
R4) Both ASCONF and ASCONF-ACK chunks MUST NOT be sent in any SCTP
state except ESTABLISHED, SHUTDOWN-PENDING, SHUTDOWN-RECEIVED and
SHUTDOWN-SENT.
R5) An ASCONF MUST NOT be larger than the path MTU of the
destination.
R6) An ASCONF-ACK SHOULD not be larger than the path MTU. In some
circumstances an ASCONF-ACK may exceed the path MTU and in such a
case IP fragmentation should be used to transmit the chunk.
If the sender of an ASCONF Chunk receives an Operational Error
indicating that the ASCONF chunk type is not understood, then the
sender MUST NOT send subsequent ASCONF Chunks to the peer. The
endpoint should also inform the upper layer application that the peer
endpoint does not support any of the extensions detailed in this
document.
4.2. Upon reception of an ASCONF Chunk.
When an endpoint receives an ASCONF Chunk from the remote peer
special procedures MAY be needed to identify the association the
ASCONF Chunk is associated with. To properly find the association
the following procedures should be followed:
L1) Use the source address and port number of the sender to attempt
to identify the association (i.e. use the same method defined in
RFC2960 [RFC2960] used for all other SCTP chunks). If found
proceed to rule L4.
L2) If the association is not found, use the address found in the
Address Parameter TLV combined with the port number found in the
SCTP common header. If found proceed to rule L4.
L3) If neither L1 or L2 locates the association, treat the chunk as
an Out Of The Blue chunk as defined in RFC2960 [RFC2960].
L4) Follow the normal rules to validate the SCTP verification tag
found in RFC2960 [RFC2960].
After identification and verification of the association, the
following should be performed to properly process the ASCONF Chunk:
C1) Compare the value of the serial number to the value the endpoint
stored in a new association variable 'Peer-Serial-Number'. This
value MUST be initialized to the Initial TSN value minus 1.
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C2) If the value found in the serial number is equal to the ('Peer-
Serial-Number' + 1), the endpoint MUST:
V1) Process the TLVs contained within the Chunk performing the
appropriate actions as indicated by each TLV type. The TLVs
MUST 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 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 last TLV in the Chunk MUST be
processed last. If the association was found via L2, the first
parameter MUST be an Add IP address parameter for the source
address of the packet. If it is not the case the ASCONF is
silently discarded. Please note that this new address can not
be deleted by a later parameter in the chunk because it is the
source address of the packet.
V2) In processing the chunk, the receiver should build a response
message with the appropriate error TLVs, as specified in the
Parameter type bits for any ASCONF Parameter it does not
understand. To indicate an unrecognized parameter, cause type
8 as defined in the ERROR in 3.3.10.8 of RFC2960 [RFC2960]
should be used. The endpoint may also use the response to
carry rejections for other reasons such as resource shortages
etc, using the Error Cause TLV and an appropriate error
condition.
Note: a positive response is implied if no error is indicated
by the sender.
V3) All responses MUST copy the ASCONF-Request Correlation ID
field received in the ASCONF parameter, from the TLV being
responded to, into the ASCONF-Request Correlation ID field in
the response parameter.
V4) After processing the entire Chunk, the receiver of the ASCONF
MUST send all TLVs for both unrecognized parameters and any
other status TLVs inside the ASCONF-ACK chunk that acknowledges
the arrival and processing of the ASCONF Chunk.
V5) Update the 'Peer-Serial-Number' to the value found in the
serial number field.
C3) If the value found in the serial number is equal to the value
stored in the 'Peer-Serial-Number', the endpoint should:
X1) Parse the ASCONF Chunk TLVs but the endpoint MUST NOT take any
action on the TLVs parsed (since it has already performed these
actions).
X2) Build a response message with the appropriate response TLVs as
specified in the ASCONF Parameter type bits, for any parameter
it does not understand or could not process.
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X3) After parsing the entire Chunk, it MUST send any response TLV
errors and status with an ASCONF-ACK chunk acknowledging the
arrival and processing of the ASCONF Chunk.
X4) The endpoint MUST NOT update its 'Peer-Serial-Number'.
Note: the response to the retransmitted ASCONF MUST be the same as
the original response. This MAY mean an implementation must keep
state in order to respond with the same exact answer (including
resource considerations that may have made the implementation
refuse a request).
IMPLEMENTATION NOTE: As an optimization a receiver may wish to
save the last ASCONF-ACK for some predetermined period of time and
instead of re-processing the ASCONF (with the same serial number)
it may just re-transmit the ASCONF-ACK. It may wish to use the
arrival of a new serial number to discard the previously saved
ASCONF-ACK or any other means it may choose to expire the saved
ASCONF-ACK.
C4) Otherwise, the ASCONF Chunk is discarded since it must be either
a stale packet or from an attacker. A receiver of such a packet
MAY log the event for security purposes.
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
responded to.
4.3. General rules for address manipulation
When building TLV parameters for the ASCONF Chunk that will add or
delete IP addresses the following rules should be applied:
D0) If an endpoint receives an ASCONF-ACK that is greater than or
equal to the next serial number to be used but no ASCONF chunk is
outstanding the endpoint MUST ABORT the association. Note that a
sequence number is greater than if it is no more than 2^^31-1
larger than the current sequence number (using serial arithmetic).
D1) When adding an IP address to an association, the IP address is
NOT considered fully added to the association until the ASCONF-ACK
arrives. This means that until such time as the ASCONF containing
the add is acknowledged the sender MUST NOT use the new IP address
as a source for ANY SCTP packet except on carrying an ASCONF
chunk. The receiver of the add IP address request may use the
address as a destination immediately. The receiver MUST use the
path verification procedure for the added address before using
that address. The receiver MUST NOT send packets to the new
address except for the corresponding ASCONF-ACK chunk or HEARTBEAT
chunks for path verification before the new path is verified. If
the ASCONF-ACK is sent to the new address it MAY be bundled with
the HEARTBEAT chunk for path verification.
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D2) After the ASCONF-ACK of an IP address add arrives, the endpoint
MAY begin using the added IP address as a source address for any
type of SCTP chunk.
D3a) If an endpoint receives an Error Cause TLV indicating that the
IP address Add or IP address Deletion parameters was not
understood, the endpoint MUST consider the operation failed and
MUST NOT attempt to send any subsequent Add or Delete requests to
the peer.
D3b) If an endpoint receives an Error Cause TLV indicating that the
IP address Set Primary IP Address parameter was not understood,
the endpoint MUST consider the operation failed and MUST NOT
attempt to send any subsequent Set Primary IP Address requests to
the peer.
D4) When deleting an IP address from an association, the IP address
MUST be considered a valid destination address for the reception
of SCTP packets until the ASCONF-ACK arrives and MUST NOT be used
as a source address for any subsequent packets. This means that
any datagrams that arrive before the ASCONF-ACK destined to the IP
address being deleted MUST be considered part of the current
association. One special consideration is that ABORT chunks
arriving destined to the IP address being deleted MUST be ignored
(see Section 4.3.1 for further details).
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
MUST NOT use the delete IP address without an add IP address
preceding the delete parameter in the ASCONF chunk. Or if an
endpoint sends 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 an IP header source address for an SCTP
packet holding the ASCONF Chunk to be the same as an address being
deleted by the ASCONF Chunk.
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
the error cause set to the new error code 'Request to Delete Last
Remaining IP Address'. The requested delete MUST NOT be performed
or acted upon, other than to send the ASCONF-ACK.
D8) If a request is received to delete an IP address which is also
the source address of the IP packet which contained the ASCONF
chunk, the receiver MUST reject this request. To reject the
request the receiver MUST send an Error Cause TLV set to the new
error code 'Request to Delete Source IP Address' (unless Rule D5
has also been violated, in which case the error code 'Request to
Delete Last Remaining IP Address' is sent).
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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, it MUST return an Error Cause TLV set to the new
error code 'Operation Refused Due to Resource Shortage'.
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
either ABORT the association or not consider the address part of
the association. In other words if the endpoint does not ABORT
the association, it must consider the add attempt failed and NOT
use this address since its peer will treat SCTP packets destined
to the address as Out Of The Blue packets.
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
subsequent add or delete requests bundled in the ASCONF. The
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 receiver begins failing any ADD or DELETE request, it must
fail all subsequent ADD or DELETE requests contained in that
single ASCONF.
D12) When an endpoint receives a request to delete an IP address that
is the current primary address, it is an implementation decision
as to how that endpoint chooses the new primary address.
D13) When an endpoint receives a valid request to DELETE an IP
address the endpoint MUST consider the address no longer as part
of the association. It MUST NOT send SCTP packets for the
association to that address and it MUST treat subsequent packets
received from that address as Out Of The Blue.
During the time interval between sending out the ASCONF and
receiving the ASCONF-ACK it MAY be possible to receive DATA chunks
out of order. The following examples illustrate these problems:
Endpoint-A Endpoint-Z
---------- ----------
ASCONF[Add-IP:X]------------------------------>
/--ASCONF-ACK
/
/--------/---New DATA:
/ / Destination
<-------------------/ / IP:X
/
<--------------------------/
In the above example we see a new IP address (X) being added to the
Endpoint-A. However due to packet re-ordering in the network a new
DATA chunk is sent and arrives at Endpoint-A before the ASCONF-ACK
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confirming the add of the address to the association.
A similar problem exists with the deletion of an IP address as
follows:
Endpoint-A Endpoint-Z
---------- ----------
/------------New DATA:
/ Destination
/ IP:X
ASCONF [DEL-IP:X]---------/---------------->
<-----------------/------------------ASCONF-ACK
/
/
<-------------/
In this example we see a DATA chunk destined to the IP:X (which is
about to be deleted) arriving after the deletion is complete. For
the ADD case an endpoint SHOULD consider the newly adding IP address
valid for the association to receive data from during the interval
when awaiting the ASCONF-ACK. The endpoint MUST NOT source data from
this new address until the ASCONF-ACK arrives but it may receive out
of order data as illustrated and MUST NOT treat this data as an OOTB
datagram (please see RFC2960 [RFC2960] section 8.4). It MAY drop the
data silently or it MAY consider it part of the association but it
MUST NOT respond with an ABORT.
For the DELETE case, an endpoint MAY respond to the late arriving
DATA packet as an OOTB datagram or it MAY hold the deleting IP
address for a small period of time as still valid. If it treats the
DATA packet as an OOTB the peer will silently discard the ABORT
(since by the time the ABORT is sent the peer will have removed the
IP address from this association). If the endpoint elects to hold
the IP address valid for a period of time, it MUST NOT hold it valid
longer than 2 RTO intervals for the destination being removed.
4.3.1. A special case for OOTB ABORT chunks
Another case worth mentioning is illustrated below:
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Endpoint-A Endpoint-Z
---------- ----------
New DATA:------------\
Source IP:X \
\
ASCONF-REQ[DEL-IP:X]----\------------------>
\ /---------ASCONF-ACK
\ /
\----/-----------> OOTB
(Ignored <---------------------/-------------ABORT
by rule D4) /
<---------------------/
For this case, during the deletion of an IP address, an Abort MUST be
ignored if the destination address of the Abort message is that of a
destination being deleted.
4.3.2. A special case for changing an address.
In some instances the sender may only have one IP address in an
association that is being renumbered. When this occurs, the sender
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
reason the sender MUST fill in the Address Parameter field with an
address that is part of the association (in this case the one being
deleted). This will allow the receiver to locate the association
without using the source address found in the IP header.
The receiver of such a chunk MUST always first use the source address
found in the IP header in looking up the association. The receiver
should attempt to use the address found in the Address Bytes field
only if the lookup fails using the source address from the IP header.
The receiver MUST reply to the source address 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 of the association after processing).
4.4. Setting of the primary address
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 set
primary request to an address that is already considered 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 will be discarded unless
the add request is to be processed BEFORE the set primary (i.e. it
precedes the set primary).
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A request to set primary MAY also appear in an INIT or INIT-ACK
chunk. This can give advice to the peer endpoint as to which of its
addresses the sender of the INIT or INIT-ACK would prefer to be used
as the primary address.
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
the best destination address to use in sending SCTP packets (in the
requesters view). If a request arrives that asks the receiver to set
an address as primary that does not exist, the receiver should NOT
honor the request, leaving its existing primary address unchanged.
5. Security Considerations
The addition and or deletion of an IP address to an existing
association does provide an additional mechanism by which existing
associations can be hijacked. Therefore this document requires the
use of the authentication mechanism defined in SCTP-AUTH [I-D.ietf-
tsvwg-sctp-auth] to limit the ability of an attacker to hijack an
association.
Hijacking an association by using the addition and deletion of an IP
address is only possible for an attacker who is able to intercept the
initial two packets of the association setup when the SCTP-AUTH
extension is used without pre-shared keys.. If such a threat is
considered a possibility, then the SCTP-AUTH [I-D.ietf-tsvwg-sctp-
auth] extension MUST be used with a preconfigured shared end-point
pair key to mitigate this threat. For a more detailed analysis see
SCTP-AUTH [I-D.ietf-tsvwg-sctp-auth].
If an SCTP endpoint that supports this extension receives an INIT
that indicates that the peer supports the ASCONF extension but does
NOT support the SCTP-AUTH [I-D.ietf-tsvwg-sctp-auth] extension, the
receiver of such an INIT MUST send an ABORT in response to such an
INIT. Note that an implementation is allowed to silently discard
such an INIT as an option as well but under NO circumstance is an
implementation allowed to proceed with the association setup by
sending an INIT-ACK in response.
An implementation that receives an INIT-ACK that indicates that the
peer does not support the SCTP-AUTH [I-D.ietf-tsvwg-sctp-auth]
extension MUST NOT send the COOKIE-ECHO to establish the association.
Instead the implementation MUST discard the INIT-ACK and report to
the upper layer user that an association cannot be established
destroying the TCB.
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6. IANA considerations
This document defines the following new SCTP parameters, chunks and
errors:
o Two new chunk types,
o Seven parameter types, and
o Five new SCTP error causes.
One of the two new chunk types must come from the range of chunk
types where the upper two bits are one, we recommend 0xC1 but any
other available code point with the upper bits set is also
acceptable. The second chunk type must come from the range where
only the upper bit is set to one. We recommend 0x80 but any other
available code point with the upper bit set is also acceptable. The
suggested chunk types are listed in Table 1.
All but one of the parameter types must come from the range of types
where the upper two bits are set, we recommend 0xC001 - 0xC006, as
specified in this document. The other parameter type must come from
the 0x8000 range, we recommend 0x8008. Note that for any of these
values a different unique parameter type may be assigned by IANA as
long as the upper bits correspond to the ones specified in this
document. The suggested parameter types are listed in Table 2, Table
3, and Table 4.
The five new error causes can be any value, in this document we have
used 0x0100-0x0104 in an attempt to separate these from the common
ranges of error codes. Any other unassigned values are also
acceptable. The suggested error causes are listed in Table 5.
This document also defines a Adaptation code point. The adaptation
code point is a 32 bit integer that is assigned by IANA through an
IETF Consensus action as defined in RFC2434 [RFC2434].
7. Acknowledgments
The authors wish to thank Jon Berger, Greg Kendall, Seok Koh, Peter
Lei, John Loughney, Ivan Arias Rodriguez, Renee Revis, Marshall Rose,
Chip Sharp, and Irene Ruengeler for their invaluable comments.
The authors would also like to give special mention to Maria-Carmen
Belinchon and Ian Rytina for there early contributions to this
document and their thoughtful comments.
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8. References
[RFC2026] Bradner, S., "The Internet Standards Process -- Revision
3", BCP 9, RFC 2026, October 1996.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC2402] Kent, S. and R. Atkinson, "IP Authentication Header",
RFC 2402, November 1998.
[RFC2434] Narten, T. and H. Alvestrand, "Guidelines for Writing an
IANA Considerations Section in RFCs", BCP 26, RFC 2434,
October 1998.
[RFC2629] Rose, M., "Writing I-Ds and RFCs using XML", RFC 2629,
June 1999.
[RFC2960] Stewart, R., Xie, Q., Morneault, K., Sharp, C.,
Schwarzbauer, H., Taylor, T., Rytina, I., Kalla, M.,
Zhang, L., and V. Paxson, "Stream Control Transmission
Protocol", RFC 2960, October 2000.
[I-D.ietf-tsvwg-sctp-auth]
Tuexen, M., "Authenticated Chunks for Stream Control
Transmission Protocol (SCTP)",
draft-ietf-tsvwg-sctp-auth-02 (work in progress),
March 2006.
Appendix A. Abstract Address Handling
A.1. General remarks
The following text provides a working definition of the endpoint
notion to discuss address reconfiguration. It is not intended to
restrict implementations in any way, its goal is to provide as set of
definitions only. Using these definitions should make a discussion
about address issues easier.
A.2. Generalized endpoints
A generalized endpoint is a pair of a set of IP addresses and a port
number at any given point of time. The precise definition is as
follows:
A generalized endpoint gE at time t is given by
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gE(t) = ({IP1, ..., IPn}, Port)
where {IP1, ..., IPn} is a non empty set of IP addresses.
Please note that the dynamic addition and deletion of IP-addresses
described in this document allows the set of IP-addresses of a
generalized endpoint to be changed at some point of time. The port
number can never be changed.
The set of IP addresses of a generalized endpoint gE at a time t is
defined as
Addr(gE)(t) = {IP1, ..., IPn}
if gE(t) = ({IP1, ..., IPn}, Port) holds at time t.
The port number of a generalized endpoint gE is defined as
Port(gE) = Port
if gE(t) = ({IP1, ..., IPn}, Port) holds at time t.
There is one fundamental rule which restricts all generalized
endpoints:
For two different generalized endpoints gE' and gE'' with the same
port number Port(gE') = Port(gE'') the address sets Addr(gE')(t) and
Addr(gE'')(t) must be disjoint at every point of time.
A.3. Associations
Associations consists of two generalized endpoints and the two
address sets known by the peer at any time. The precise definition
is as follows:
An association A between to different generalized endpoints gE' and
gE'' is given by
A = (gE', S', gE'', S'')
where S'(t) and S''(t) are set of addresses at any time t such that
S'(t) is a non-empty subset of Addr(gE')(t) and S''(t) is a non-empty
subset of Addr(gE'')(t).
If A = (gE', S', gE'', S'') is an association between the generalized
endpoints gE' and gE'' the following notion is used:
Addr(A, gE') = S' and Addr(A, gE'') = S''.
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If the dependency on time is important the notion Addr(A, gE')(t) =
S'(t) will be used.
If A is an association between gE' and gE'' then Addr(A, gE') is the
subset of IP addresses of gE' which is known by gE'' and used by gE'.
Association establishment between gE' and gE'' can be seen as:
1. gE' and gE'' do exist before the association.
2. If an INIT has to be send from gE' to gE'' address scoping rules
and other limitations are applied to calculate the subset S' from
Addr(gE'). The addresses of S' are included in the INIT chunk.
3. If an INIT-ACK has to be send from gE'' to gE' address scoping
rules and other limitations are applied to calculate the subset
S'' from Addr(gE''). The addresses of S'' are included in the
INIT-ACK chunk.
4. After the handshake the association A = (gE', S', gE'', S'') has
been established.
5. Right after the association establishment Addr(A, gE') and
Addr(A, gE'') are the addresses which have been seen on the wire
during the handshake.
A.4. Relationship with RFC 2960
RFC2960 [RFC2960] defines the notion of an endpoint. This subsection
will show that these endpoints are also (special) generalized
endpoints.
RFC2960 [RFC2960] has no notion of address scoping or other address
handling limitations and provides no mechanism to change the
addresses of an endpoint.
This means that an endpoint is simply a generalized endpoint which
does not depend on the time. Neither the Port nor the address list
changes.
During association setup no address scoping rules or other
limitations will be applied. This means that for an association A
between two endpoints gE' and gE'' the following is true:
Addr(A, gE') = Addr(gE') and Addr(A, gE'') = Addr(gE'').
A.5. Rules for address manipulation
The rules for address manipulation can now be stated in a simple way:
1. An address can be added to a generalized endpoint gE only if this
address is not an address of a different generalized endpoint
with the same port number.
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2. An address can be added to an association A with generalized
endpoint gE if it has been added to the generalized endpoint gE
first. This means that the address must be an element of
Addr(gE) first and then it can become an element of Addr(A, gE).
But this is not necessary. If the association does not allow the
reconfiguration of the addresses only Addr(gE) can be modified.
3. An address can be deleted from an association A with generalized
endpoint gE as long as Addr(A, gE) stays non-empty.
4. An address can be deleted from an generalized endpoint gE only if
it has been removed from all associations having gE as a
generalized endpoint.
These rules simply make sure that the rules for the endpoints and
associations given above are always fulfilled.
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Authors' Addresses
Randall R. Stewart
Cisco Systems, Inc.
4875 Forest Drive
Suite 200
Columbia, SC 29206
US
Phone:
Email: rrs@cisco.com
Michael A. Ramalho
Cisco Systems, Inc.
1802 Rue de la Porte
Wall Township, NJ 07719-3784
USA
Phone: +1.732.449.5762
Email: mramalho@cisco.com
Qiaobing Xie
Motorola, Inc.
1501 W. Shure Drive, #2309
Arlington Heights, IL 60004
USA
Phone: +1-847-632-3028
Email: qxie1@email.mot.com
Michael Tuexen
Univ. of Applied Sciences Muenster
Stegerwaldstr. 39
48565 Steinfurt
Germany
Email: tuexen@fh-muenster.de
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Phillip T. Conrad
University of Delaware
Department of Computer and Information Sciences
Newark, DE 19716
US
Phone: +1 302 831 8622
Email: conrad@acm.org
URI: http://www.cis.udel.edu/~pconrad
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