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Network Working Group R. Stewart
Internet-Draft Cisco Systems, Inc.
Intended status: Standards Track Q. Xie
Expires: December 21, 2007 Motorola, Inc.
M. Tuexen
Univ. of Applied Sciences Muenster
S. Maruyama
M. Kozuka
Kyoto University
June 19, 2007
Stream Control Transmission Protocol (SCTP) Dynamic Address
Reconfiguration
draft-ietf-tsvwg-addip-sctp-22.txt
Status of this Memo
By submitting this Internet-Draft, each author represents that any
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This Internet-Draft will expire on December 21, 2007.
Copyright Notice
Copyright (C) The IETF Trust (2007).
Abstract
A local host may have multiple points of attachment to the Internet,
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giving it a degree of fault tolerance from hardware failures. Stream
Control Transmission Protocol (SCTP) [I-D.ietf-tsvwg-2960bis] was
developed to take full advantage of such a multi-homed host to
provide a fast failover and association survivability in the face of
such hardware failures. This document describes an extension to SCTP
that will allow an SCTP stack to dynamically add an IP Addresses to
an SCTP association, dynamically delete an IP addresses from an SCTP
association, and to request to set the primary address the peer will
use when sending to an endpoint.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 5
2. Conventions . . . . . . . . . . . . . . . . . . . . . . . . . 5
3. Serial Number Arithmetic . . . . . . . . . . . . . . . . . . . 6
4. Additional Chunks and Parameters . . . . . . . . . . . . . . . 6
4.1. New Chunk Types . . . . . . . . . . . . . . . . . . . . . 6
4.1.1. Address Configuration Change Chunk (ASCONF) . . . . . 7
4.1.2. Address Configuration Acknowledgment Chunk
(ASCONF-ACK) . . . . . . . . . . . . . . . . . . . . . 8
4.2. New Parameter Types . . . . . . . . . . . . . . . . . . . 9
4.2.1. Add IP Address . . . . . . . . . . . . . . . . . . . . 10
4.2.2. Delete IP Address . . . . . . . . . . . . . . . . . . 11
4.2.3. Error Cause Indication . . . . . . . . . . . . . . . . 12
4.2.4. Set Primary IP Address . . . . . . . . . . . . . . . . 13
4.2.5. Success Indication . . . . . . . . . . . . . . . . . . 14
4.2.6. Adaptation Layer Indication . . . . . . . . . . . . . 15
4.2.7. Supported Extensions Parameter . . . . . . . . . . . . 15
4.3. New Error Causes . . . . . . . . . . . . . . . . . . . . . 16
4.3.1. Error Cause: Request to Delete Last Remaining IP
Address . . . . . . . . . . . . . . . . . . . . . . . 17
4.3.2. Error Cause: Operation Refused Due to Resource
Shortage . . . . . . . . . . . . . . . . . . . . . . . 17
4.3.3. Error Cause: Request to Delete Source IP Address . . . 18
4.3.4. Error Cause: Association Aborted due to illegal
ASCONF-ACK . . . . . . . . . . . . . . . . . . . . . . 19
4.3.5. Error Cause: Request refused - no authorization. . . . 19
5. Procedures . . . . . . . . . . . . . . . . . . . . . . . . . . 20
5.1. ASCONF Chunk Procedures . . . . . . . . . . . . . . . . . 20
5.1.1. Congestion Control of ASCONF Chunks . . . . . . . . . 22
5.2. Upon reception of an ASCONF Chunk. . . . . . . . . . . . . 23
5.3. General rules for address manipulation . . . . . . . . . . 26
5.3.1. A special case for OOTB ABORT Chunks . . . . . . . . . 29
5.3.2. A special case for changing an address. . . . . . . . 30
5.4. Setting of the primary address . . . . . . . . . . . . . . 30
5.5. Bundling of multiple ASCONFs . . . . . . . . . . . . . . . 31
6. Security Considerations . . . . . . . . . . . . . . . . . . . 31
7. IANA considerations . . . . . . . . . . . . . . . . . . . . . 34
8. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 35
9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 36
9.1. Normative References . . . . . . . . . . . . . . . . . . . 36
9.2. Informative References . . . . . . . . . . . . . . . . . . 36
Appendix A. Abstract Address Handling . . . . . . . . . . . . . . 37
A.1. General remarks . . . . . . . . . . . . . . . . . . . . . 37
A.2. Generalized endpoints . . . . . . . . . . . . . . . . . . 37
A.3. Associations . . . . . . . . . . . . . . . . . . . . . . . 38
A.4. Relationship with RFC 4960 . . . . . . . . . . . . . . . . 38
A.5. Rules for address manipulation . . . . . . . . . . . . . . 39
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Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 39
Intellectual Property and Copyright Statements . . . . . . . . . . 41
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1. Introduction
A local host may have multiple points of attachment to the Internet,
giving it a degree of fault tolerance from hardware failures. SCTP
was developed to take full advantage of such a multi-homed host to
provide a fast failover and association survivability in the face of
such hardware failures. However, many modern computers allow for the
dynamic addition and deletion of network cards (sometimes termed a
hot-pluggable interface). Complicate this with the ability of a
provider, in IPv6, to dynamically renumber a network, and there still
is a gap between full fault tolerance and the currently defined SCTP
protocol. No matter if a card is added or an interface is
renumbered, in order to take advantage of this new configuration, the
transport association must be restarted. For many fault tolerant
applications this restart is considered an outage and is undesirable.
This document describes an extension to SCTP to attempt to correct
this problem for the more demanding fault tolerant application. This
extension will allow an SCTP stack to:
o Dynamically add an IP Addresses to an association.
o Dynamically delete an IP Addresses from an association.
o Request to set the primary address the peer will use when sending
to an endpoint.
The dynamic addition and subtraction of IP addresses allows an SCTP
association to continue to function through host and network
reconfigurations. These changes, brought on by provider or user
action, may mean that the peer would be better served by using the
newly added address, however this information may only be known by
the endpoint that had the reconfiguration occur. In such a case this
extension allows the local endpoint to advise the peer as to what it
thinks is the better primary address that the peer should be using.
One last thing this extension adds is a small 32 bit integer, called
an adaptation indication, that can be exchanged at startup. This is
useful for applications where there is one or more specific layers
below the application, yet still above SCTP. In such a case the
exchange of this indication can allow the proper layer to be enabled
below the application.
2. Conventions
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119].
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3. Serial Number Arithmetic
It is essential to remember that the actual ASCONF Sequence Number
space is finite, though very large. This space ranges from 0 to
2**32 - 1. Since the space is finite, all arithmetic dealing with
ASCONF Sequence Numbers MUST be performed modulo 2**32. This
unsigned arithmetic preserves the relationship of sequence numbers as
they cycle from 2**32 - 1 to 0 again. There are some subtleties to
computer modulo arithmetic, so great care should be taken in
programming the comparison of such values. When referring to ASCONF
Sequence Numbers, the symbol "=<" means "less than or equal"(modulo
2**32).
Comparisons and arithmetic on ASCONF sequence numbers in this
document SHOULD use Serial Number Arithmetic as defined in [RFC1982]
where SERIAL_BITS = 32.
ASCONF Sequence Numbers wrap around when they reach 2**32 - 1. That
is, the next ASCONF Sequence Number an ASCONF chunk MUST use after
transmitting ASCONF Sequence Number = 2**32 - 1 is 0.
Any arithmetic done on Stream Sequence Numbers SHOULD use Serial
Number Arithmetic as defined in [RFC1982] where SERIAL_BITS = 16.
All other arithmetic and comparisons in this document uses normal
arithmetic.
4. 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.
4.1. 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.
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Chunk Type Chunk Name
--------------------------------------------------------------
0xC1 Address Configuration Change Chunk (ASCONF)
0x80 Address Configuration Acknowledgment (ASCONF-ACK)
Table 1: Address Configuration Chunks
4.1.1. 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 [I-D.ietf-tsvwg-2960bis] for all variable
parameters. This chunk MUST be sent in an authenticated way by using
the mechanism defined in [I-D.ietf-tsvwg-sctp-auth]. If this chunk
is received unauthenticated it MUST be silently discarded as
described in [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 = 0xC1 | Chunk Flags | Chunk Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sequence Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Address Parameter |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ASCONF Parameter #1 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
\ \
/ .... /
\ \
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ASCONF Parameter #N |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Sequence Number : 32 bits (unsigned integer)
This value represents a Sequence Number for the ASCONF Chunk. The
valid range of Sequence Number is from 0 to 4294967295 (2**32 - 1).
Sequence Numbers wrap back to 0 after reaching 4294967295.
Address Parameter : 8 or 20 bytes (depending on the address type)
This field contains an address parameter, either IPv6 or IPv4, from
[I-D.ietf-tsvwg-2960bis]. The address is an address of the sender of
the ASCONF Chunk, the address MUST be considered part of the
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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 MUST NOT be sent and MUST be ignored if
received in any ASCONF message.
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 [I-D.ietf-tsvwg-2960bis]. section 3.2. Note that the
upper two bits in the ASCONF Chunk are set to one. As defined in
[I-D.ietf-tsvwg-2960bis] section 3.2, when setting these upper bits
in this manner the receiver that does not understand this chunk MUST
skip the chunk and continue processing, and report in an Operation
Error Chunk using the 'Unrecognized Chunk Type' cause of error. This
will NOT abort the association but indicates to the sender that it
MUST not send any further ASCONF chunks.
ASCONF Parameter: TLV format
Each Address configuration change is represented by a TLV parameter
as defined in Section 4.2. One or more requests may be present in an
ASCONF Chunk.
4.1.2. Address Configuration Acknowledgment Chunk (ASCONF-ACK)
This chunk is used by the receiver of an ASCONF Chunk to acknowledge
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
[I-D.ietf-tsvwg-sctp-auth]. If this chunk is received
unauthenticated it MUST be silently discarded as described in
[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 = 0x80 | Chunk Flags | Chunk Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sequence Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ASCONF Parameter Response#1 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
\ \
/ .... /
\ \
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ASCONF Parameter Response#N |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Sequence Number : 32 bits (unsigned integer)
This value represents the Sequence 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 Sequence Number.
4.2. New Parameter Types
The seven new parameters added follow the format defined in section
3.2.1 of [I-D.ietf-tsvwg-2960bis]. Tables 2, 3 and 4 describe the
parameters.
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
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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.
If the receiver chooses NOT to abort, the parameter MUST be ignored.
A robust implementation SHOULD ignore the parameter and leave the
association intact.
4.2.1. 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. 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. Note that the receiver MUST NOT change this 32 bit value.
Address Parameter: TLV
This field contains an IPv4 or IPv6 address parameter as described in
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3.3.2.1 of [I-D.ietf-tsvwg-2960bis]. 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 192.0.2.1 be added to
the association would look as follows:
+--------------------------------+
| Type=0xC001 | Length = 16 |
+--------------------------------+
| C-ID = 0x01023474 |
+--------------------------------+
| Type=5 | Length = 8 |
+----------------+---------------+
| Value=0xC0000201 |
+----------------+---------------+
Valid Chunk Appearance
The Add IP Address parameter may only appear in the ASCONF Chunk
type.
4.2.2. 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. 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. Note that the receiver MUST NOT change this 32 bit value.
Address Parameter: TLV
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This field contains an IPv4 or IPv6 address parameter as described in
3.3.2.1 of [I-D.ietf-tsvwg-2960bis]. 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 192.0.2.1 from an existing
association would look as follows:
+--------------------------------+
| Type=0xC002 | Length = 16 |
+--------------------------------+
| C-ID = 0x01023476 |
+--------------------------------+
| Type=5 | Length = 8 |
+----------------+---------------+
| Value=0xC0000201 |
+----------------+---------------+
Valid Chunk Appearance
The Delete IP Address parameter may only appear in the ASCONF Chunk
type.
4.2.3. 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 Success Indication |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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
Response Correlation ID field so the peer can easily correlate the
request to this response. Note that the receiver MUST NOT change
this 32 bit value.
Error Cause(s): TLV(s)
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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
[I-D.ietf-tsvwg-2960bis]). The Error Cause(s) follow the format
defined in section 3.3.10 of [I-D.ietf-tsvwg-2960bis].
Valid Chunk Appearance
The Error Cause Indication parameter may only appear in the ASCONF-
ACK Chunk type.
4.2.4. 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. 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. Note that the receiver MUST NOT change this 32 bit value.
Address Parameter: TLV
This field contains an IPv4 or IPv6 address parameter as described in
3.3.2.1 of [I-D.ietf-tsvwg-2960bis]. 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 [I-D.ietf-tsvwg-2960bis]). The receiver MAY mark this as
its primary upon receiving this request. If the address 0.0.0.0 or
::0 is provided, the receiver MAY mark the source address of the
packet as its primary.
An example TLV requesting that the IPv4 address 192.0.2.1 be made the
primary destination address would look as follows:
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+--------------------------------+
| Type=0xC004 | Length = 16 |
+--------------------------------+
| C-ID = 0x01023479 |
+--------------------------------+
| Type=5 | Length = 8 |
+----------------+---------------+
| Value=0xC0000201 |
+----------------+---------------+
Valid Chunk Appearance
The Set Primary IP Address parameter may appear in the ASCONF, 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.
4.2.5. 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 Sequence 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
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
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chunk type.
4.2.6. 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 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.
Note: this parameter is not used in either the addition or deletion
of addresses but is for the convenience of the upper layer. This
document includes this parameter to minimize the number of SCTP
documents.
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
based upon the upper layer protocol configuration of the SCTP stack.
This parameter MUST NOT be sent in any other chunks and if it is
received in another chunk it MUST be ignored.
4.2.7. 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. An implementation supporting this
extension MUST list the ASCONF,the ASCONF-ACK, and the AUTH chunks in
its INIT and INIT-ACK parameters.
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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.
4.3. 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
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4.3.1. Error Cause: Request to Delete Last Remaining IP Address
Cause of error
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=0xC0000201 |
+----------------+---------------+
4.3.2. 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=0xC0000201 |
+----------------+---------------+
4.3.3. 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=0xC0000201 |
+----------------+---------------+
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.
4.3.4. 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 5.3 Rule F0 ). 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. Sequence numbers smaller than the last
acked sequence number are silently ignored.
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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
4.3.5. 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 /
/ \
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
5. Procedures
This section will lay out the specific procedures for address
configuration change chunk type and its processing.
5.1. ASCONF Chunk Procedures
When an endpoint has an ASCONF signaled change to be sent to the
remote endpoint it MUST do the following:
A1) Create an ASCONF Chunk as defined in Section 4.1.1. The chunk
MUST 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 sequence number MUST be assigned to the Chunk. The sequence
number MUST be larger by one. The sequence 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
MUST be incremented by one after assigning the sequence number to
the newly created chunk .
A3) If no SCTP packet with one or more ASCONF Chunk(s) is
outstanding (un-acknowledged) with the remote peer, send the chunk
and proceed to step A4. If an ASCONF chunk is outstanding, then
the ASCONF chunk should be queued for later transmission and no
further action should be taken until the previous ASCONF is
acknowledged or a time out occurs.
A4) The sender MUST Start a T-4 RTO timer, using the RTO value of
the selected destination address (normally the primary path; see
[I-D.ietf-tsvwg-2960bis] section 6.4 for details).
A5) When the ASCONF-ACK that acknowledges the sequence number last
sent arrives, the sender MUST stop the T-4 RTO timer, and clear
the appropriate association and destination error counters as
defined in [I-D.ietf-tsvwg-2960bis] section 8.1 and 8.2.
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A6) The endpoint MUST process all of the TLVs within the ASCONF-
ACK(s) 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.
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 MUST do the following:
B1) Increment the error counters and perform path failure detection
on the appropriate destination address as defined in
[I-D.ietf-tsvwg-2960bis] section 8.1 and 8.2.
B2) Increment the association error counters and perform endpoint
failure detection on the association as defined in
[I-D.ietf-tsvwg-2960bis] 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
[I-D.ietf-tsvwg-2960bis] section 6.4.1). An endpoint MUST NOT add
new parameters to this chunk, it MUST be the same (including its
sequence number) as the last ASCONF sent. An endpoint MAY,
however, bundle an additional ASCONF with new ASCONF parameters
with the next sequence number. For details see Section 5.5
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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 [I-D.ietf-tsvwg-2960bis] section 6.4.1 for
details).
5.1.1. 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:
C1) One and only one SCTP packet holding ASCONF Chunk(s) 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). However when an ASCONF Chunk is retransmitted due to a
time-out, the additional held ASCONF Chunks can be bundled into
the retransmission packet as described in Section 5.5.
C2) An ASCONF Chunk may be bundled with any other chunk type
including other ASCONF Chunks. If bundled with other ASCONF
Chunks, the chunks MUST appear in sequential order with respect to
their Sequence Number.
C3) An ASCONF-ACK Chunk may be bundled with any other chunk type
including other ASCONF-ACK Chunks. If bundled with other ASCONF-
ACK Chunks, the chunks MUST appear in sequential order with
respect to their Sequence Number.
C4) Both ASCONF and ASCONF-ACK Chunks MUST NOT be sent in any SCTP
state except ESTABLISHED, SHUTDOWN-PENDING, SHUTDOWN-RECEIVED and
SHUTDOWN-SENT.
C5) An ASCONF Chunk and an ASCONF-ACK Chunk SHOULD not be larger
than the PMTU. If the PMTU is unknown, then the PMTU should be
set to the minimum PMTU. The minimum PMTU depends on the IP
version used for transmission, and is the lesser of 576 octets and
the first-hop MTU for IPv4 [RFC1122] and 1280 octets for IPv6
[RFC2460].
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An ASCONF sender without these restrictions could possibly flood the
network with a large number of separate address change operations
thus causing network congestion.
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.
5.2. 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:
D1) Use the source address and port number of the sender to attempt
to identify the association (i.e., use the same method defined in
[I-D.ietf-tsvwg-2960bis] used for all other SCTP Chunks). If
found proceed to rule D4.
D2) 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 D4.
D2-ext) If more than one ASCONF Chunks are packed together, use the
address found in the ASCONF Address Parameter TLV of each of the
subsequent ASCONF Chunks. If found, proceed to rule D4.
D3) If neither D1, D2 nor D2-ext locates the association, treat the
chunk as an Out Of The Blue packet as defined in
[I-D.ietf-tsvwg-2960bis].
D4) Follow the normal rules to validate the SCTP verification tag
found in [I-D.ietf-tsvwg-2960bis].
D5) After the verification tag has been validated, normal chunk
processing should occur. Prior to finding the ASCONF chunk the
receiver MUST encounter an AUTH chunk as described in
[I-D.ietf-tsvwg-sctp-auth]. If either authentication fails, or
the AUTH chunk is missing, the receiver MUST silently discard this
chunk and the rest of the packet.
After identification and verification of the association, the
following should be performed to properly process the ASCONF Chunk:
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E1)
If the value found in the sequence number of the ASCONF Chunk is
equal to the ('Peer-Sequence-Number' + 1) and the Sequence Number
of the ASCONF Chunk is the first in the SCTP Packet, the endpoint
MAY clean any old cached ASCONF-ACK up to the 'Peer-Sequence-
Number' and then proceed to rule E4.
E1-ext If the value found in the sequence number of the ASCONF Chunk
is equal to the ('Peer-Sequence-Number' + 1) and the ASCONF chunk
is NOT the first Sequence Number in the SCTP packet proceed to
rule E4 but do NOT clear any cached ASCONF-ACK or state
information.
E2)
If the value found in the sequence number is less than the ('Peer-
Sequence-Number' + 1), simply skip to the next ASCONF, and include
in the outbound response packet any previously cached ASCONF-ACK
response that was sent and saved that matches the sequence number
of the ASCONF. Note: it is possible that no cached ASCONF-ACK
Chunk exists. This will occur when an older ASCONF arrives out of
order. In such a case the receiver should skip the ASCONF Chunk
and not include ASCONF-ACK Chunk for that chunk.
E3)
Then, process each ASCONF one by one as above while the Sequence
Number of the ASCONF is less than the ('Peer-Sequence-Number' +
1).
E4) When the sequence number matches the next one expected, process
the ASCONF as described below and after processing the ASCONF
Chunk, append an ASCONF-ACK Chunk to the response packet and cache
a copy of it (in the event it later needs to be retransmitted).
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.
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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
[I-D.ietf-tsvwg-2960bis] 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 queue the response ASCONF-ACK Chunk for transmission after
the rest of the SCTP packet has been processed. This allows
the ASCONF-ACK Chunk to be bundled with other ASCONF-ACK Chunks
as well as any additional responses e.g. a SACK Chunk.
V5) Update the 'Peer-Sequence-Number' to the value found in the
sequence number field.
E5) 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.
E6) When all ASCONF Chunks are processed for this SCTP packet, send
back the accumulated single response packet with all of the
ASCONF-ACK Chunks. The destination address of the SCTP packet
containing the ASCONF-ACK Chunks MUST be the source address of the
SCTP packet that held the ASCONF Chunks.
E7) While processing the ASCONF Chunks in the SCTP packet, if the
response packet will exceed the PMTU of the return path, the
receiver MUST stop adding additional ASCONF-ACKs into the response
packet but MUST continue to process all of the ASCONF Chunks,
saving ASCONF-ACK Chunk responses in its cached copy. The sender
of the ASCONF Chunk will later retransmit the ASCONF Chunks that
were not responded to, at which time the cached copies of the
responses that would NOT fit in the PMTU can be sent to the peer.
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Note: These rules have been presented with the assumption that the
implementation is caching old ASCONF-ACKs in case of loss of SCTP
packets in the ACK path. It is allowable for an implementation to
maintain this state in another form it deems appropriate, as long as
that form results in the same ASCONF-ACK sequences being returned to
the peer as outlined above.
5.3. General rules for address manipulation
When building TLV parameters for the ASCONF Chunk that will add or
delete IP addresses the following rules MUST be applied:
F0) If an endpoint receives an ASCONF-ACK that is greater than or
equal to the next sequence 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).
F1) 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.
F2) 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.
F3a) 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.
F3b) 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.
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F4) 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 5.3.1 for further details).
F5) 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.
F6) 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.
F7) 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.
F8) 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 F5
has also been violated, in which case the error code 'Request to
Delete Last Remaining IP Address' is sent).
F9) 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'.
F10) 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.
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F11) 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.
F12) 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.
F13) 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:
F14) All addresses added by the reception of an ASCONF chunk MUST be
put into the unconfirmed state and MUST have path verification
performed on them before the address can be used as described in
[I-D.ietf-tsvwg-2960bis] section 5.4.
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
confirming the add of the address to the association.
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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 [I-D.ietf-tsvwg-2960bis] 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.
5.3.1. 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 F4) /
<---------------------/
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.
5.3.2. 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 Parameter
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).
5.4. 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 MUST 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
requester's 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.
5.5. Bundling of multiple ASCONFs
In the normal case a single ASCONF is sent in a packet and a single
reply ASCONF-ACK is received. However, in the event of the loss of
an SCTP packet containing either an ASCONF or ASCONF-ACK it is
allowable for a sender to bundle additional ASCONFs in the
retransmission. In bundling multiple ASCONFs the following rules
MUST be followed:
1. Previously transmitted ASCONF Chunks MUST be left unchanged.
2. Each SCTP packet containing ASCONF Chunks MUST be bundled
starting with the smallest ASCONF Sequence Number first in the
packet (closest to the Chunk header) and preceding in sequential
order from lowest to highest ASCONF Sequence Number.
3. All ASCONFs within the packet MUST be adjacent to each other
i.e., no other chunk type must separate the ASCONFs.
4. Each new ASCONF lookup address MUST be populated as if the
previous ASCONFs had been processed and accepted.
6. 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
[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 [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
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[I-D.ietf-tsvwg-sctp-auth].
When the address parameter in ASCONF chunks with Add, IP Delete IP,
or Set Primary IP parameters is a wildcard, the source address of the
packet is used. This address is not protected by SCTP-AUTH
[I-D.ietf-tsvwg-sctp-auth] and an attacker can therefore intercept
such a packet and modify the source address. Even if the source
address is not one presently an alternate for the association, the
identification of the association may rely on the other information
in the packet (perhaps the verification tag, for example). An on-
path attacker can therefore modify the source address to its liking.
If the ASCONF includes an Add IP with a wildcard address, the
attacker can add an address of its liking, which provides little
immediate damage but can set up later attacks.
If the ASCONF includes a Delete IP with a wildcard address, the
attacker can cause all addresses but one of its choosing to be
deleted from an association. The address supplied by the attacker
must already belong to the association, which makes this more
difficult for the attacker. However, the sole remaining address
might be one that the attacker controls, for example, or can monitor,
etc. The least result is the sender and the deceived receiver would
have different ideas of what that sole remaining address would be.
This will eventually cause the association to fail, but in the
meantime, the deceived receiver could be transmitting packets to an
address the sender did not intend.
If the ASCONF includes a Set Primary IP with a wildcard address, then
the attacker can cause an address to be used as a primary address.
This is limited to an address that already belongs to the
association, so the damage is limited. At least, the result would be
that the recipient is using a primary address that the sender did not
intend. However, if both a wildcard Add IP and a wildcard Set
Primary IP are used, then the attacker can modify the source address
to both add an address to its liking to the association and make it
the primary address. Such a combination would present the attacker
with opportunity for more damage.
Note that all these attacks are from an on-path attacker. Endpoints
that believe they face a threat from on-path attackers SHOULD NOT use
wildcard addresses in ASCONF Add IP, Delete IP or Set Primary IP
parameters.
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 [I-D.ietf-tsvwg-sctp-auth] extension, the receiver of
such an INIT MUST send an ABORT in response to such an INIT. Note:
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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 [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.
Other types of attacks, e.g. bombing, are discussed in detail in
[I-D.ietf-tsvwg-sctpthreat]. The bombing attack, in particular, is
countered by the use of a random nonce and is required by
[I-D.ietf-tsvwg-2960bis].
An on-path attacker can modify the INIT and INIT-ACK Supported
Extensions parameter (and authentication related parameters) to
produce a denial of service. If the on-path attacker removes the
[I-D.ietf-tsvwg-sctp-auth] related parameters from an INIT that
indicates it supports the ASCONF extension, the association will not
be established. If the on-path attacker adds a Supported Extensions
parameter mentioning the ASCONF type to an INIT or INIT-ACK that does
not carry any AUTH related parameters, the association will not be
established. If the on-path attacker removes the Supported
Extensions parameter (or removes the ASCONF type from that parameter)
from the INIT or the INIT-ACK, then the association will not be able
to use the ADD-IP feature. If the on-path attacker adds the
Supported Extensions parameter listing the ASCONF type to an INIT-ACK
that did not carry one (but did carry AUTH related parameters), then
the INIT sender may use ASCONF where the INIT-ACK sender does not
support it. This would be discovered later if the INIT sender
transmitted an ASCONF, but the INIT sender could have made
configuration choices at that point. As the INIT and INIT-ACK are
not protected by the AUTH feature, there is no way to counter such
attacks. Note however that an on-path attacker capable of modifying
the INIT and INIT-ACK would almost certainly also be able to prevent
the INIT and INIT-ACK from being delivered or modify the verification
tags or checksum to cause the packet to be discarded, so the
Supported Extensions adds little additional vulnerability (with
respect to preventing association formation) to the SCTP protocol.
The ability to prevent the use of this new feature is an additional
vulnerability to SCTP but only for this new feature.
The Adaptation Layer Indication is subject to corruption, insertion
or deletion from the INIT and INIT-ACK chunks by an on-path attacker.
This parameter SHOULD be opaque to the SCTP protocol (see section
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4.2.6), and so changes to the parameter will likely not affect the
SCTP protocol. However, any adaptation layer that is defined SHOULD
consider its own vulnerabilities in the security considerations
section of the RFC that defines its adaptation code point.
The Set Primary IP Address parameter is subject to corruption,
insertion or deletion by an on-path attacker when included in the
INIT and INIT-ACK chunks. The attacker could use this to influence
the receiver to choose an address to its own purposes (one over which
it has control, one that would be less desirable for the sender,
etc.). An on-path attacker would also have the ability to include or
remove addresses for the association from the INIT or INIT-ACK, so it
is not limited in the address it can specify in the Set Primary IP
Address. Endpoints that wish to avoid this possible threat MAY defer
sending the initial Set Primary request and wait until the
association is fully established before sending a fully protected
ASCONF with the Set Primary as its single parameter.
7. IANA considerations
This document defines the following new SCTP parameters, chunks and
errors (http://www.iana.org/assignments/sctp-parameters):
o Two new chunk types,
o Six 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
chunk types with there suggested values are shown below.
Chunk Type Chunk Name
--------------------------------------------------------------
0xC1 Address Configuration Change Chunk (ASCONF)
0x80 Address Configuration Acknowledgment (ASCONF-ACK)
All of the parameter types, with the exception of the supported
parameters extension, must come from the range of types where the
upper two bits are set, we recommend 0xC001 - 0xC006, as shown below.
The supported parameters type extension must come from the range
where only the upper bit is set, we recommend 0x8008. Note: that for
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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 below:
Parameter Type Parameter Name
-------------------------------------------------
0x8008 Supported Extensions
0xC001 Add IP Address
0xC002 Delete IP Address
0xC003 Error Cause Indication
0xC004 Set Primary Address
0xC005 Success Indication
0xC006 Adaptation Layer Indication
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 below:.
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.
This document also defines an 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]. For this new registry
no initial values are being added by this document, however
draft-ietf-rddp-sctp will add the first entry.
8. Acknowledgments
The authors would like to express a special note of thanks to Michael
Ramahlo and Phillip Conrad for their extreme efforts in the early
formation of this draft.
The authors wish to thank Jon Berger, Mark Butler, Lars Eggert,
Janardhan Iyengar, Greg Kendall, Seok Koh, Salvatore Loreto, Peter
Lei, John Loughney, Sandy Murphy, Ivan Arias Rodriguez, Renee Revis,
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Marshall Rose, Ronnie Sellars, 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.
And a special thanks to James Polk, abstract writer to the few but
lucky.
9. References
9.1. Normative References
[RFC1122] Braden, R., "Requirements for Internet Hosts -
Communication Layers", STD 3, RFC 1122, October 1989.
[RFC1982] Elz, R. and R. Bush, "Serial Number Arithmetic", RFC 1982,
August 1996.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC2434] Narten, T. and H. Alvestrand, "Guidelines for Writing an
IANA Considerations Section in RFCs", BCP 26, RFC 2434,
October 1998.
[RFC2460] Deering, S. and R. Hinden, "Internet Protocol, Version 6
(IPv6) Specification", RFC 2460, December 1998.
[I-D.ietf-tsvwg-2960bis]
Stewart, R., "Stream Control Transmission Protocol",
draft-ietf-tsvwg-2960bis-05 (work in progress), June 2007.
[I-D.ietf-tsvwg-sctp-auth]
Tuexen, M., "Authenticated Chunks for Stream Control
Transmission Protocol (SCTP)",
draft-ietf-tsvwg-sctp-auth-08 (work in progress),
February 2007.
9.2. Informative References
[I-D.ietf-tsvwg-sctpthreat]
Stewart, R., "Security Attacks Found Against SCTP and
Current Countermeasures", draft-ietf-tsvwg-sctpthreat-05
(work in progress), June 2007.
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Appendix A. Abstract Address Handling
A.1. General remarks
This appendix is non-normative. It is present to give the reader a
concise mathematical definition of an SCTP endpoint. 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 a 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
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.
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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''.
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 4960
[I-D.ietf-tsvwg-2960bis] defines the notion of an endpoint. This
subsection will show that these endpoints are also (special)
generalized endpoints.
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[I-D.ietf-tsvwg-2960bis] 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.
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.
Authors' Addresses
Randall R. Stewart
Cisco Systems, Inc.
4875 Forest Drive
Suite 200
Columbia, SC 29206
US
Phone:
Email: rrs@cisco.com
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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
Shin Maruyama
Kyoto University
Yoshida-Honmachi
Sakyo-ku
Kyoto, Kyoto 606-8501
JAPAN
Phone: +81-75-753-7468
Email: mail@marushin.gr.jp
Masahiro Kozuka
Kyoto University
Yoshida-Honmachi
Sakyo-ku
Kyoto, Kyoto 606-8501
JAPAN
Phone: +81-75-753-7468
Email: ma-kun@kozuka.jp
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