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Listed below is the contents of file draft-ietf-tsvwg-addip-sctp-06.txt.
Network Working Group R. Stewart
Internet-Draft M. Ramalho
Expires: March 2, 2003 Cisco Systems, Inc.
Q. Xie
Motorola, Inc.
M. Tuexen
Siemens AG
I. Rytina
M. Belinchon
Ericsson
P. Conrad
Temple University
September 2002
Stream Control Transmission Protocol (SCTP) Dynamic Address
Reconfiguration
draft-ietf-tsvwg-addip-sctp-06.txt
Status of this Memo
This document is an Internet-Draft and is in full conformance with
all provisions of Section 10 of RFC2026.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF), its areas, and its working groups. Note that
other groups may also distribute working documents as Internet-
Drafts.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
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
http://www.ietf.org/shadow.html.
This Internet-Draft will expire on March 2, 2003.
Copyright Notice
Copyright (C) The Internet Society (2002). All Rights Reserved.
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 . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Conventions . . . . . . . . . . . . . . . . . . . . . . . . 4
3. Additional Chunks and Parameters . . . . . . . . . . . . . . 5
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
3.3 Error Cause Indication . . . . . . . . . . . . . . . . . . . 10
3.4 Set Primary IP Address . . . . . . . . . . . . . . . . . . . 11
3.5 Success Indication . . . . . . . . . . . . . . . . . . . . . 12
3.5.1 Adaptation Layer Indication . . . . . . . . . . . . . . . . 12
3.6 New Error Causes . . . . . . . . . . . . . . . . . . . . . . 13
3.6.1 Error Cause: Request to Delete Last Remaining IP Address . . 13
3.6.2 Error Cause: Operation Refused Due to Resource Shortage . . 14
3.6.3 Error Cause: Request to Delete Source IP Address . . . . . . 15
3.6.4 Error Cause: Association Aborted due to illegal ASCONF-ACK . 16
4. Procedures . . . . . . . . . . . . . . . . . . . . . . . . . 17
4.1 ASCONF Chunk Procedures . . . . . . . . . . . . . . . . . . 17
4.1.1 Congestion Control of ASCONF Chunks . . . . . . . . . . . . 18
4.2 Upon reception of an ASCONF Chunk. . . . . . . . . . . . . . 19
4.3 General rules for address manipulation . . . . . . . . . . . 21
4.3.1 A special case for OOTB ABORT chunks . . . . . . . . . . . . 25
4.3.2 A special case for changing an address. . . . . . . . . . . 25
4.4 Setting of the primary address . . . . . . . . . . . . . . . 26
5. Security Considerations . . . . . . . . . . . . . . . . . . 27
6. IANA considerations . . . . . . . . . . . . . . . . . . . . 28
7. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . 29
References . . . . . . . . . . . . . . . . . . . . . . . . . 30
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . 30
A. Abstract Address Handling . . . . . . . . . . . . . . . . . 33
A.1 General remarks . . . . . . . . . . . . . . . . . . . . . . 33
A.2 Generalized endpoints . . . . . . . . . . . . . . . . . . . 33
A.3 Associations . . . . . . . . . . . . . . . . . . . . . . . . 34
A.4 Relationship with RFC 2960 . . . . . . . . . . . . . . . . . 35
A.5 Rules for address manipulation . . . . . . . . . . . . . . . 35
Full Copyright Statement . . . . . . . . . . . . . . . . . . 36
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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.
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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 [2].
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3. Additional Chunks and Parameters
This section describes the addition of two new chunks and, six 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.
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 [5] section 3.2. Note that the upper two bits
in the ASCONF Chunk are set to one. As defined in RFC2960 [5]
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 [5], forall variable 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 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 [5]. 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. 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
the reception. It carries zero or more results for any ASCONF
Parameters that were processed by the receiver.
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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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 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 six new parameters added follow the format defined in section
3.2.1 of RFC2960 [5]. Table 2 and 3 describes the parameters.
Address Configuration Parameters Parameter Type
-------------------------------------------------
Add IP Address 0xC001
Delete IP Address 0xC002
Set Primary Address 0xC004
Adaption Layer Indication 0xC006
Table 2: Parameters used in ASCONF Parameter
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Address Configuration Parameters Parameter Type
-------------------------------------------------
Error Cause Indication 0xC003
Success Indication 0xC005
Table 3: Parameters used in ASCONF Parameter Response
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
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 [5]. The complete TLV is wrapped within this
parameter. It informs the receiver that the address specified is to
be added to the existing association.
An example TLV requesting that the IPv4 address 10.1.1.1 be added to
the association would look as follows:
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+--------------------------------+
| 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.
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
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 [5]. The complete TLV is wrapped within this
parameter. It informs the receiver that the address specified is to
be removed from the existing association.
An example TLV deleting the IPv4 address 10.1.1.1 from an existing
association would look as follows:
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+--------------------------------+
| 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.
3.3 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
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 [5]). The
Error Cause(s) follow the format defined in section 3.3.10 of RFC2960
[5].
Valid Chunk Appearance
The Error Cause Indication parameter may only appear in the ASCONF-
ACK chunk type.
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3.4 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 [5]. 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
[5]). The receiver MAY mark this as its primary upon receiving this
request.
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 = 18 |
+--------------------------------+
| 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
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parameter in the INIT or INIT-ACK can be used to indicate an initial
preference of primary address.
3.5 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
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.
3.5.1 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 = Variable |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Adaption 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
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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 adaption 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.
3.6 New Error Causes
Four 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
Table 4: New Error Causes
3.6.1 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:
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+--------------------------------+
| Type = 0xC003 | Length = 24 |
+--------------------------------+
| C-ID = 0x01023476 |
+--------------------------------+
| Cause=0x0100 | Length = 16 |
+----------------+---------------+
| Type= 0xC002 | Length = 12 |
+----------------+---------------+
| Type=0x0005 | Length = 8 |
+----------------+---------------+
| Value=0x0A010101 |
+----------------+---------------+
3.6.2 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.
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:
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+--------------------------------+
| Type = 0xC003 | Length = 24 |
+--------------------------------+
| C-ID = 0x01023474 |
+--------------------------------+
| Cause=0x0101 | Length = 16 |
+----------------+---------------+
| Type=0xC001 | Length = 12 |
+--------------------------------+
| Type=0x0005 | Length = 8 |
+----------------+---------------+
| Value=0x0A010101 |
+----------------+---------------+
3.6.3 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:
+--------------------------------+
| Type = 0xC003 | Length = 24 |
+--------------------------------+
| C-ID = 0x01023476 |
+--------------------------------+
| Cause=0x0102 | Length = 16 |
+----------------+---------------+
| Type=0xC002 | Length = 12 |
+----------------+---------------+
| Type=0x0005 | Length = 8 |
+----------------+---------------+
| Value=0x0A010101 |
+----------------+---------------+
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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.
3.6.4 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 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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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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 SHOULD 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 [5]
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
[5] 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.
A8) If there is no response(s) to specific TLV parameter(s), and no
failures are indicated, then all request(s) are considered
successful.
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A9) If the peer responds to an ASCONF with an ERROR chunk reporting
that it did not recognized 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 [5]
section 8.1 and 8.2.
B2) Increment the association error counters and perform endpoint
failure detection on the association as defined in RFC2960 [5]
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 [5] 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 [5] 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-
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transit on any given association (one sent from each endpoint).
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.
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 [5] 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 [5].
L4) Follow the normal rules to validate the SCTP verification tag
found in RFC2960 [5].
After identification and verification of the association, the
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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.
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.
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 [5] 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:
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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.
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 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
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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.
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.
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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).
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
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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
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 [5] 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
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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:
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
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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).
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.
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5. Security Considerations
The ADD/DELETE of an IP address to an existing association does
provide an additional mechanism by which existing associations can be
hijacked. Where the attacker is able to intercept and or alter the
packets sent and received in an association, the use of this feature
MAY increase the ease with which an association may be overtaken.
This threat SHOULD be considered when deploying a version of SCTP
that makes use of this feature. The IP Authentication Header RFC2402
[3] SHOULD be used when the threat environment requires stronger
integrity protections, but does not require confidentiality. It
should be noted that in the base SCTP specification RFC2960 [5], if
an attacker is able to intercept and or alter packets, even without
this feature it is possible to hijack an existing association; please
refer to Section 11 of RFC2960 [5].
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6. IANA considerations
This document defines the following new SCTP parameters, chunks and
errors:
o Two new chunk types,
o Six parameter types, and
o Three new SCTP error causes.
This document also defines a Adaption code point. The adaption code
point is a 32 bit interger that is assigned by IANA through an IETF
Consensus action as defined in RFC2434 [4].
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7. Acknowledgments
The authors wish to thank Jon Berger, Peter Lei, John Loughney, Ivan
Arias Rodriguez, Renee Revis, Marshall Rose, and Chip Sharp for their
invaluable comments.
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References
[1] Bradner, S., "The Internet Standards Process -- Revision 3", BCP
9, RFC 2026, October 1996.
[2] Bradner, S., "Key words for use in RFCs to Indicate Requirement
Levels", BCP 14, RFC 2119, March 1997.
[3] Kent, S. and R. Atkinson, "IP Authentication Header", RFC 2402,
November 1998.
[4] Narten, T. and H. Alvestrand, "Guidelines for Writing an IANA
Considerations Section in RFCs", BCP 26, RFC 2434, October 1998.
[5] 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.
Authors' Addresses
Randall R. Stewart
Cisco Systems, Inc.
8725 West Higgins Road
Suite 300
Chicago, IL 60631
USA
Phone: +1-815-477-2127
EMail: [email protected]
Michael A. Ramalho
Cisco Systems, Inc.
1802 Rue de la Porte
Wall Township, NJ 07719-3784
USA
Phone: +1.732.449.5762
EMail: [email protected]
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Qiaobing Xie
Motorola, Inc.
1501 W. Shure Drive, #2309
Arlington Heights, IL 60004
USA
Phone: +1-847-632-3028
EMail: [email protected]
Michael Tuexen
Siemens AG
ICN WN CS SE 5
D-81359 Munich
Germany
Phone: +49 89 722 47210
EMail: [email protected]
Ian Rytina
Ericsson
37/360 Elizabeth Street
Melbourne Victoria
Australia
Phone: +61-3-9301-6164
EMail: [email protected]
Maria-Carmen Belinchon
Ericsson
Spain
Phone:
EMail: [email protected]
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Phillip T. Conrad
Temple University
CIS Department
Room 303, Computer Building (038-24)
1805 N. Broad St.
Philadelphia, PA 19122
US
Phone: +1 215 204 7910
EMail: [email protected]
URI: http://www.cis.temple.edu/~conrad
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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
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.
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A.4 Relationship with RFC 2960
RFC2960 [5] defines the notion of an endpoint. This subsection will
show that these endpoints are also (special) generalized endpoints.
RFC2960 [5] 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.
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Full Copyright Statement
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This document and translations of it may be copied and furnished to
others, and derivative works that comment on or otherwise explain it
or assist in its implementation may be prepared, copied, published
and distributed, in whole or in part, without restriction of any
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The limited permissions granted above are perpetual and will not be
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TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
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MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
Acknowledgement
Funding for the RFC Editor function is currently provided by the
Internet Society.
Stewart, et al. Expires March 2, 2003 [Page 36]
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