draft-ietf-tsvwg-prsctp-01.txt   draft-ietf-tsvwg-prsctp-02.txt 
Network Working Group R. Stewart Network Working Group R. Stewart
Internet-Draft M. Ramalho Internet-Draft M. Ramalho
Expires: February 20, 2004 Cisco Systems, Inc. Expires: May 26, 2004 Cisco Systems, Inc.
Q. Xie Q. Xie
Motorola, Inc. Motorola, Inc.
M. Tuexen M. Tuexen
Univ. of Applied Sciences Muenster Univ. of Applied Sciences Muenster
P. Conrad P. Conrad
Temple University University of Delaware
August 22, 2003 November 26, 2003
SCTP Partial Reliability Extension SCTP Partial Reliability Extension
draft-ietf-tsvwg-prsctp-01.txt draft-ietf-tsvwg-prsctp-02.txt
Status of this Memo Status of this Memo
This document is an Internet-Draft and is in full conformance with This document is an Internet-Draft and is in full conformance with
all provisions of Section 10 of RFC2026. all provisions of Section 10 of RFC2026.
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF), its areas, and its working groups. Note that other Task Force (IETF), its areas, and its working groups. Note that other
groups may also distribute working documents as Internet-Drafts. groups may also distribute working documents as Internet-Drafts.
skipping to change at page 1, line 37 skipping to change at page 1, line 37
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
The list of current Internet-Drafts can be accessed at http:// The list of current Internet-Drafts can be accessed at http://
www.ietf.org/ietf/1id-abstracts.txt. www.ietf.org/ietf/1id-abstracts.txt.
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This Internet-Draft will expire on February 20, 2004. This Internet-Draft will expire on May 26, 2004.
Copyright Notice Copyright Notice
Copyright (C) The Internet Society (2003). All Rights Reserved. Copyright (C) The Internet Society (2003). All Rights Reserved.
Abstract Abstract
This memo describes an extension to the Stream Control Transmission This memo describes an extension to the Stream Control Transmission
Protocol (SCTP) RFC2960 [5] that allows an SCTP endpoint to signal to Protocol (SCTP) RFC2960 [3] that allows an SCTP endpoint to signal to
its peer that it should move the cumulative ack point forward. When its peer that it should move the cumulative ack point forward. When
both sides of an SCTP association support this extension, it can be both sides of an SCTP association support this extension, it can be
used by an SCTP implementation to provide partially reliable data used by an SCTP implementation to provide partially reliable data
transmission service to an upper layer protocol. This memo describes transmission service to an upper layer protocol. This memo describes
(1) the protocol extensions, which consist of a new parameter for (1) the protocol extensions, which consist of a new parameter for
INIT and INIT ACK, and a new FORWARD TSN chunk type (2) one example INIT and INIT ACK, and a new FORWARD TSN chunk type (2) one example
partially reliable service that can be provided to the upper layer partially reliable service that can be provided to the upper layer
via this mechanism. via this mechanism.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1 Overview of Protocol Extensions . . . . . . . . . . . . . . 3 1.1 Overview of Protocol Extensions . . . . . . . . . . . . . . 3
1.2 Overview of New Services Provided to the Upper Layer . . . . 3 1.2 Overview of New Services Provided to the Upper Layer . . . . 3
1.3 Benefits of PR-SCTP . . . . . . . . . . . . . . . . . . . . 4 1.3 Benefits of PR-SCTP . . . . . . . . . . . . . . . . . . . . 4
2. Conventions . . . . . . . . . . . . . . . . . . . . . . . . 6 2. Conventions . . . . . . . . . . . . . . . . . . . . . . . . 5
3. Protocol Changes to support PR-SCTP . . . . . . . . . . . . 7 3. Protocol Changes to support PR-SCTP . . . . . . . . . . . . 5
3.1 Forward-TSN-Supported Parameter For INIT and INIT ACK . . . 7 3.1 Forward-TSN-Supported Parameter For INIT and INIT ACK . . . 5
3.2 Forward Cumulative TSN Chunk Definition (FORWARD TSN) . . . 7 3.2 Forward Cumulative TSN Chunk Definition (FORWARD TSN) . . . 6
3.3 Negotiation of Forward-TSN-Supported parameter . . . . . . . 8 3.3 Negotiation of Forward-TSN-Supported parameter . . . . . . . 7
3.3.1 Sending Forward-TSN-Supported param in INIT . . . . . . . . 8 3.3.1 Sending Forward-TSN-Supported param in INIT . . . . . . . . 7
3.3.2 Receipt of Forward-TSN-Supported param in INIT or 3.3.2 Receipt of Forward-TSN-Supported parameter in INIT or
INIT-ACK . . . . . . . . . . . . . . . . . . . . . . . . . . 9 INIT-ACK . . . . . . . . . . . . . . . . . . . . . . . . . . 7
3.3.3 Receipt of Op. Error for Forward-TSN-Supported Param . . . . 9 3.3.3 Receipt of Op. Error for Forward-TSN-Supported Param . . . . 8
3.4 Definition of "abandoned" in the context of PR-SCTP . . . . 10 3.4 Definition of "abandoned" in the context of PR-SCTP . . . . 8
3.5 Sender Side Implementation of PR-SCTP . . . . . . . . . . . 10 3.5 Sender Side Implementation of PR-SCTP . . . . . . . . . . . 9
3.6 Receiver Side Implementation of PR-SCTP . . . . . . . . . . 13 3.6 Receiver Side Implementation of PR-SCTP . . . . . . . . . . 12
4. Services provided by PR-SCTP to the upper layer . . . . . . 16 4. Services provided by PR-SCTP to the upper layer . . . . . . 14
4.1 PR-SCTP Service Definition for "timed reliability" . . . . . 16 4.1 PR-SCTP Service Definition for "timed reliability" . . . . . 15
4.2 PR-SCTP Association Establishment . . . . . . . . . . . . . 18 4.2 PR-SCTP Association Establishment . . . . . . . . . . . . . 16
4.3 Guidelines for defining other PR-SCTP Services . . . . . . . 19 4.3 Guidelines for defining other PR-SCTP Services . . . . . . . 17
4.4 Usage Notes . . . . . . . . . . . . . . . . . . . . . . . . 20 4.4 Usage Notes . . . . . . . . . . . . . . . . . . . . . . . . 18
5. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . 21 5. Variables . . . . . . . . . . . . . . . . . . . . . . . . . 19
6. Security Considerations . . . . . . . . . . . . . . . . . . 22 6. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . 19
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . 23 7. Security Considerations . . . . . . . . . . . . . . . . . . 19
References . . . . . . . . . . . . . . . . . . . . . . . . . 24 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . 19
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . 24 Normative references . . . . . . . . . . . . . . . . . . . . 19
Intellectual Property and Copyright Statements . . . . . . . 26 Informational References . . . . . . . . . . . . . . . . . . 19
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . 20
Intellectual Property and Copyright Statements . . . . . . . 22
1. Introduction 1. Introduction
This memo describes an extension to the Stream Control Transmission This memo describes an extension to the Stream Control Transmission
Protocol (SCTP) RFC2960 [5] that allows an SCTP sender to signal to Protocol (SCTP) RFC2960 [3] that allows an SCTP sender to signal to
its peer that it should no longer expect to receive one or more DATA its peer that it should no longer expect to receive one or more DATA
chunks. chunks.
1.1 Overview of Protocol Extensions 1.1 Overview of Protocol Extensions
The protocol extension described in this document consists of two new The protocol extension described in this document consists of two new
elements: elements:
1. a single new parameter in the INIT/INIT-ACK exchange that 1. a single new parameter in the INIT/INIT-ACK exchange that
indicates whether the endpoint supports the extension indicates whether the endpoint supports the extension
2. a single new chunk type, FORWARD TSN, that indicates that the 2. a single new chunk type, FORWARD TSN, that indicates that the
receiver should move its cumulative ack point forward (possibly receiver should move its cumulative ack point forward (possibly
skipping past one or more Data chunks that may not yet have been skipping past one or more DATA chunks that may not yet have been
received and/or acknowledged.) received and/or acknowledged.)
1.2 Overview of New Services Provided to the Upper Layer 1.2 Overview of New Services Provided to the Upper Layer
When this extension is supported by both sides of an SCTP When this extension is supported by both sides of an SCTP
association, it can be used to provide partially reliable transport association, it can be used to provide partially reliable transport
service over an SCTP association. We define partially reliable service over an SCTP association. We define partially reliable
transport service as a service that allows the user to specify, on a transport service as a service that allows the user to specify, on a
per message basis, the rules governing how persistent the transport per message basis, the rules governing how persistent the transport
service should be in attempting to send the message to the receiver. service should be in attempting to send the message to the receiver.
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reliable services in a particular SCTP implementation without reliable services in a particular SCTP implementation without
changing the on-the-wire protocol. Also, the SCTP receiver does not changing the on-the-wire protocol. Also, the SCTP receiver does not
necessarily need to know which semantics of partially reliable necessarily need to know which semantics of partially reliable
service are being used by the sender, since the receiver's only role service are being used by the sender, since the receiver's only role
is to correctly interpret FORWARD TSN chunks, thereby skipping past is to correctly interpret FORWARD TSN chunks, thereby skipping past
messages that the sender has decided to no longer transmit (or messages that the sender has decided to no longer transmit (or
retransmit). retransmit).
Nevertheless, it is recommended that a limited number of standard Nevertheless, it is recommended that a limited number of standard
definitions of partially reliable services be standardized by the definitions of partially reliable services be standardized by the
IETF so that that the designers of IETF application layer protocols IETF so that the designers of IETF application layer protocols can
can match the requirements of their upper layer protocols to standard match the requirements of their upper layer protocols to standard
service definitions provided by a particular SCTP implementation. service definitions provided by a particular SCTP implementation.
One such definition, "timed reliability" is included in this One such definition, "timed reliability" is included in this
document. Given the extensions proposed in this document, other document. Given the extensions proposed in this document, other
definitions may be standardized as the need arises without further definitions may be standardized as the need arises without further
changes to the on-the-wire protocol. changes to the on-the-wire protocol.
1.3 Benefits of PR-SCTP 1.3 Benefits of PR-SCTP
Hereafter, we use the notation "PR-SCTP" to refer to the SCTP Hereafter, we use the notation "PR-SCTP" to refer to the SCTP
protocol extended as defined in this document. protocol extended as defined in this document.
The following are some of the advantages for integrating partially The following are some of the advantages for integrating partially
reliable data service into SCTP, i.e., benefits of PR-SCTP: reliable data service into SCTP, i.e., benefits of PR-SCTP:
1. Some application layer protocols may benefit from being able to 1. Some application layer protocols may benefit from being able to
use a single SCTP association to carry both reliable content, -- use a single SCTP association to carry both reliable content, --
such as text pages, billing and accounting information, setup such as text pages, billing and accounting information, setup
signaling -- and unreliable content, e.g. state that is highly signaling -- and unreliable content, e.g. state that is highly
sensitive to timeliness, where generating a new packet is more sensitive to timeliness, where generating a new packet is more
advantageous than transmitting an old one [1]. advantageous than transmitting an old one [4].
2. Partially reliable data traffic carried by PR-SCTP will enjoy the 2. Partially reliable data traffic carried by PR-SCTP will enjoy the
same communication failure detection and protection capabilities same communication failure detection and protection capabilities
as the normal reliable SCTP data traffic does. This includes the as the normal reliable SCTP data traffic does. This includes the
ability to: - quickly detect a failed destination address; - ability to: - quickly detect a failed destination address; -
fail-over to an alternate destination address, and; - be notified fail-over to an alternate destination address, and; - be notified
if the data receiver becomes unreachable. if the data receiver becomes unreachable.
3. In addition to providing unordered unreliable data transfer as 3. In addition to providing unordered unreliable data transfer as
UDP does, PR-SCTP can provide ordered unreliable data transfer UDP does, PR-SCTP can provide ordered unreliable data transfer
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the network overhead) can be reduced versus having to send these the network overhead) can be reduced versus having to send these
different types of data using separate protocols. Additionally, different types of data using separate protocols. Additionally,
this multiplexing allows for port savings versus using different this multiplexing allows for port savings versus using different
ports for reliable and unreliable connections. ports for reliable and unreliable connections.
2. Conventions 2. Conventions
The keywords MUST, MUST NOT, REQUIRED, SHALL, SHALL NOT, SHOULD, The keywords MUST, MUST NOT, REQUIRED, SHALL, SHALL NOT, SHOULD,
SHOULD NOT, RECOMMENDED, NOT RECOMMENDED, MAY, and OPTIONAL, when SHOULD NOT, RECOMMENDED, NOT RECOMMENDED, MAY, and OPTIONAL, when
they appear in this document, are to be interpreted as described in they appear in this document, are to be interpreted as described in
RFC2119 [3]. RFC2119 [2].
Comparisons and arithmetic on TSNs are governed by the rules in Comparisons and arithmetic on TSNs are governed by the rules in
Section 1.6 of RFC2960 [5]. Section 1.6 of RFC2960 [3].
3. Protocol Changes to support PR-SCTP 3. Protocol Changes to support PR-SCTP
3.1 Forward-TSN-Supported Parameter For INIT and INIT ACK 3.1 Forward-TSN-Supported Parameter For INIT and INIT ACK
The following new OPTIONAL parameter is added to the INIT and INIT The following new OPTIONAL parameter is added to the INIT and INIT
ACK chunks. ACK chunks.
Parameter Name Status Type Value Parameter Name Status Type Value
------------------------------------------------------------- -------------------------------------------------------------
Forward-TSN-Supported OPTIONAL 0xC000 Forward-TSN-Suppored OPTIONAL 49152 (0xC000)
At the initialization of the association, the sender of the INIT or At the initialization of the association, the sender of the INIT or
INIT ACK chunk shall include this OPTIONAL parameter to inform its INIT ACK chunk shall include this OPTIONAL parameter to inform its
peer that it is able to support the Forward TSN chunk. The format of peer that it is able to support the Forward TSN chunk. The format of
this parameter is defined as follows: this parameter is defined as follows:
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Parameter Type = 0xC000 | Parameter Length = 4 | | Parameter Type = 49152 | Parameter Length = 4 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type: 16 bit u_int Type: 16 bit u_int
0xC000, indicating Forward-TSN-Supported parameter 49152, indicating Forward-TSN-Supported parameter
Length: 16 bit u_int Length: 16 bit u_int
Indicate the size of the parameter i.e., 4. Indicates the size of the parameter i.e., 4.
3.2 Forward Cumulative TSN Chunk Definition (FORWARD TSN) 3.2 Forward Cumulative TSN Chunk Definition (FORWARD TSN)
The following new chunk type is defined: The following new chunk type is defined:
Chunk Type Chunk Name Chunk Type Chunk Name
------------------------------------------------------ ------------------------------------------------------
0xC0 Forward Cumulative TSN (FORWARD TSN) 192 (0xC0) Forward Cumulative TSN (FORWARD TSN)
This chunk shall be used by the data sender to inform the data This chunk shall be used by the data sender to inform the data
receiver to adjust its cumulative received TSN point forward because receiver to adjust its cumulative received TSN point forward because
some missing TSNs are associated with data chunks that SHOULD NOT be some missing TSNs are associated with data chunks that SHOULD NOT be
transmitted or retransmitted by the sender. transmitted or retransmitted by the sender.
Forward Cumulative TSN chunk has the following format: Forward Cumulative TSN chunk has the following format:
0 1 2 3 0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type = 0xC0 | Flags = 0x00 | Length = Variable | | Type = 192 | Flags = 0x00 | Length = Variable |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| New Cumulative TSN | | New Cumulative TSN |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Stream-1 | Stream Sequence-1 | | Stream-1 | Stream Sequence-1 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
\ / \ /
/ \ / \
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Stream-N | Stream Sequence-N | | Stream-N | Stream Sequence-N |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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This field holds a stream number that was skipped by this This field holds a stream number that was skipped by this
FWD-TSN. FWD-TSN.
Stream Sequence-N: 16 bit u_int Stream Sequence-N: 16 bit u_int
This field holds the sequence number associated with the stream This field holds the sequence number associated with the stream
that was skipped. The stream sequence field holds the largest stream that was skipped. The stream sequence field holds the largest stream
sequence number in this stream being skipped. The receiver of sequence number in this stream being skipped. The receiver of
the FWD-TSN's can use the Stream-N and Stream Sequence-N fields the FWD-TSN's can use the Stream-N and Stream Sequence-N fields
to enable delivery of any stranded TSN's that remain on the stream to enable delivery of any stranded TSN's that remain on the stream
re-ordering queues. This field MUST NOT report TSN's cooresponding re-ordering queues. This field MUST NOT report TSN's corresponding
to DATA chunk that are marked as unordered. For ordered DATA to DATA chunk that are marked as unordered. For ordered DATA
chunks this field MUST be filled in. chunks this field MUST be filled in.
3.3 Negotiation of Forward-TSN-Supported parameter 3.3 Negotiation of Forward-TSN-Supported parameter
3.3.1 Sending Forward-TSN-Supported param in INIT 3.3.1 Sending Forward-TSN-Supported param in INIT
If an SCTP endpoint supports the FORWARD TSN chunk, then any time it If an SCTP endpoint supports the FORWARD TSN chunk, then any time it
sends an INIT during association establishment, it SHOULD include the sends an INIT during association establishment, it SHOULD include the
Forward-TSN-supported parameter in the INIT chunk to indicate this Forward-TSN-supported parameter in the INIT chunk to indicate this
fact to its peer. fact to its peer.
3.3.2 Receipt of Forward-TSN-Supported param in INIT or INIT-ACK 3.3.2 Receipt of Forward-TSN-Supported parameter in INIT or INIT-ACK
When a receiver of an INIT detects a Forward-TSN-Supported parameter, When a receiver of an INIT detects a Forward-TSN-Supported parameter,
and does not support the Forward-TSN chunk type, the receiver SHOULD and does not support the Forward-TSN chunk type, the receiver SHOULD
treat this parameter as an invalid or unrecognized parameter and treat this parameter as an invalid or unrecognized parameter and
respond to the data sender with an unrecognized parameter in the respond to the data sender with an unrecognized parameter in the
INIT-ACK, following the rules defined in Section 3.3.3 of RFC2960 INIT-ACK, following the rules defined in Section 3.3.3 of RFC2960
[5]. [3].
When a receiver of an INIT-ACK detects a Forward-TSN-Supported When a receiver of an INIT-ACK detects a Forward-TSN-Supported
parameter, and does not support the Forward-TSN chunk type, the parameter, and does not support the Forward-TSN chunk type, the
receiver SHOULD treat this parameter as an invalid or unrecognized receiver SHOULD treat this parameter as an invalid or unrecognized
parameter and respond to the data sender with an unrecognized parameter and respond to the data sender with an unrecognized
parameter error, following the rules defined in Section 3.3.3 of parameter error, following the rules defined in Section 3.3.3 of
RFC2960 [4]. This error SHOULD be reported in an ERROR chunk bundled RFC2960 [3]. This error SHOULD be reported in an ERROR chunk bundled
with the COOKIE-ECHO. with the COOKIE-ECHO.
When a receiver of an INIT detects a Forward-TSN-Supported parameter, When a receiver of an INIT detects a Forward-TSN-Supported parameter,
and does support the Forward-TSN chunk type, the receiver SHOULD and does support the Forward-TSN chunk type, the receiver SHOULD
respond with a Forward-TSN-supported parameter in the INIT-ACK chunk. respond with a Forward-TSN-supported parameter in the INIT-ACK chunk.
When an endpoint that supports the FORWARD TSN chunk receives an INIT When an endpoint that supports the FORWARD TSN chunk receives an INIT
that does not contain the Forward-TSN-Supported Parameter, that that does not contain the Forward-TSN-Supported Parameter, that
endpoint: endpoint:
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associations life, associations life,
o SHOULD inform the upper layer, if the upper layer has requested o SHOULD inform the upper layer, if the upper layer has requested
such notification. such notification.
3.3.3 Receipt of Op. Error for Forward-TSN-Supported Param 3.3.3 Receipt of Op. Error for Forward-TSN-Supported Param
When an SCTP endpoint that desires to use the FORWARD TSN chunk When an SCTP endpoint that desires to use the FORWARD TSN chunk
feature for partially reliable data transfer receives an operational feature for partially reliable data transfer receives an operational
error from the remote endpoint (either bundled with the COOKIE or as error from the remote endpoint (either bundled with the COOKIE or as
a unrecognized parameter in the INIT-ACK), indicating that the remote an unrecognized parameter in the INIT-ACK), indicating that the
endpoint does not recognize the Forward-TSN-Supported parameter, the remote endpoint does not recognize the Forward-TSN-Supported
local endpoint SHOULD inform its upper layer of the remote endpoint's parameter, the local endpoint SHOULD inform its upper layer of the
inability to support partially reliable data transfer. remote endpoint's inability to support partially reliable data
transfer.
The local endpoint may then choose to either: The local endpoint may then choose to either:
1) end the initiation process (in cases where the initiation 1) end the initiation process (in cases where the initiation
process has already ended the endpoint may need to send an ABORT), process has already ended the endpoint may need to send an ABORT),
in consideration of the peer's inability to supply the requested in consideration of the peer's inability to supply the requested
features for the new association, or features for the new association, or
2) continue the initiation process (in cases where the initiation 2) continue the initiation process (in cases where the initiation
process has already completed the endpoint MUST just mark the process has already completed the endpoint MUST just mark the
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receipt of SACK receipt of SACK
o rules governing generation of FORWARD TSN chunks. o rules governing generation of FORWARD TSN chunks.
In detail, these exceptions are as follows: In detail, these exceptions are as follows:
A1) The sender maintains an "Advanced.Peer.Ack.Point" for each peer A1) The sender maintains an "Advanced.Peer.Ack.Point" for each peer
to track a theoretical cumulative TSN point of the peer (Note, to track a theoretical cumulative TSN point of the peer (Note,
this is a _new_ protocol variable and its value is NOT necessarily this is a _new_ protocol variable and its value is NOT necessarily
the same as the SCTP "Cumulative TSN Ack Point" as defined in the same as the SCTP "Cumulative TSN Ack Point" as defined in
Section 1.4 of RFC2960 [5]) and discussed throughout that Section 1.4 of RFC2960 [3]) and discussed throughout that
document. document.
A2) From time to time, as governed by the rules of a particular A2) From time to time, as governed by the rules of a particular
PR-SCTP service definition (see Section 4), the SCTP data sender PR-SCTP service definition (see Section 4), the SCTP data sender
may make a determination that a particular data chunk that has may make a determination that a particular data chunk that has
already been assigned a TSN SHOULD be "abandoned". already been assigned a TSN SHOULD be "abandoned".
When a data chunk is "abandoned", the sender MUST treat the data When a data chunk is "abandoned", the sender MUST treat the data
chunk as being finally acked and no longer outstanding. chunk as being finally acked and no longer outstanding.
The sender MUST NOT credit an "abandoned" data chunk to the The sender MUST NOT credit an "abandoned" data chunk to the
partial_bytes_acked as defined in Section 7.2.2 of RFC2960 [5], partial_bytes_acked as defined in Section 7.2.2 of RFC2960 [3],
and MUST NOT advance the cwnd based on this "abandoned" data and MUST NOT advance the cwnd based on this "abandoned" data
chunk. chunk.
A3) When a TSN is "abandoned", if it is part of a fragmented message, A3) When a TSN is "abandoned", if it is part of a fragmented message,
all other TSN's within that fragmented message MUST be abandoned all other TSN's within that fragmented message MUST be abandoned
at the same time. at the same time.
A4) Whenever the data sender receives a SACK from the data receiver, A4) Whenever the data sender receives a SACK from the data receiver,
it MUST first process the SACK using the normal procedures as it MUST first process the SACK using the normal procedures as
defined in Section 6.2.1 of RFC2960 [5]. defined in Section 6.2.1 of RFC2960 [3].
The data sender MUST then perform the following additional steps : The data sender MUST then perform the following additional steps :
C1) Let SackCumAck be the Cumulative TSN ACK carried in the C1) Let SackCumAck be the Cumulative TSN ACK carried in the
received SACK. received SACK.
If (Advanced.Peer.Ack.Point < SackCumAck), then update If (Advanced.Peer.Ack.Point < SackCumAck), then update
Advanced.Peer.Ack.Point to be equal to SackCumAck. Advanced.Peer.Ack.Point to be equal to SackCumAck.
C2) Try to further advance the "Advanced.Peer.Ack.Point" locally, C2) Try to further advance the "Advanced.Peer.Ack.Point" locally,
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In this example, the data sender successfully advanced the In this example, the data sender successfully advanced the
"Advanced.Peer.Ack.Point" from 102 to 104 locally. "Advanced.Peer.Ack.Point" from 102 to 104 locally.
C3) If, after step C1 and C2, the "Advanced.Peer.Ack.Point" is C3) If, after step C1 and C2, the "Advanced.Peer.Ack.Point" is
greater than the Cumulative TSN ACK carried in the received greater than the Cumulative TSN ACK carried in the received
SACK, the data sender MUST send the data receiver a FORWARD TSN SACK, the data sender MUST send the data receiver a FORWARD TSN
chunk containing the latest value of the chunk containing the latest value of the
"Advanced.Peer.Ack.Point". "Advanced.Peer.Ack.Point".
IMPLEMENTATION NOTE: It is an implemenation decision as to
which destination address is to be sent to, the only
restriction being that the address MUST be one that is
CONFIRMED.
C4) For each "abandoned" TSN the sender of the FORWARD TSN MUST C4) For each "abandoned" TSN the sender of the FORWARD TSN MUST
determine if the chunk has a valid stream and sequence number determine if the chunk has a valid stream and sequence number
(i.e., it was ordered). If the chunk has a valid stream and (i.e., it was ordered). If the chunk has a valid stream and
sequence number the sender MUST include the stream and sequence sequence number the sender MUST include the stream and sequence
number in the FORWARD TSN. This information will enable the number in the FORWARD TSN. This information will enable the
receiver to easily find any stranded TSN's waiting on stream receiver to easily find any stranded TSN's waiting on stream
reorder queues. Each stream SHOULD only be reported once; this reorder queues. Each stream SHOULD only be reported once; this
means that if multiple abandoned messages occur in the same means that if multiple abandoned messages occur in the same
stream then only the highest abandoned stream sequence number stream then only the highest abandoned stream sequence number
is reported. If the total size of the FORWARD TSN does NOT fit is reported. If the total size of the FORWARD TSN does NOT fit
in a single MTU then the sender of the FORWARD TSN SHOULD lower in a single MTU then the sender of the FORWARD TSN SHOULD lower
the Advanced.Peer.Ack.Point to the last TSN that will fit in a the Advanced.Peer.Ack.Point to the last TSN that will fit in a
single MTU. single MTU.
C5) If a FORWARD TSN is sent, the sender MUST assure that at least C5) If a FORWARD TSN is sent, the sender MUST assure that at least
one T3-rtx timer is running. one T3-rtx timer is running.
IMPLEMENTATION NOTE: Any destination's timer may be used for
the purposes of rule C5.
A5) Any time the T3-rtx timer expires, on any destination, the sender A5) Any time the T3-rtx timer expires, on any destination, the sender
SHOULD try to advance the "Advanced.Peer.Ack.Point" by following SHOULD try to advance the "Advanced.Peer.Ack.Point" by following
the procedures outlined in C1 - C5. the procedures outlined in C2 - C5.
The following additional rules govern the generation of FORWARD TSN The following additional rules govern the generation of FORWARD TSN
chunks: chunks:
F1) An endpoint MUST NOT use the FORWARD TSN for any purposes other F1) An endpoint MUST NOT use the FORWARD TSN for any purposes other
than circumstances described in this document. than circumstances described in this document.
F2) The data sender SHOULD always attempt to bundle an outgoing F2) The data sender SHOULD always attempt to bundle an outgoing
FORWARD TSN with outbound DATA chunks for efficiency. FORWARD TSN with outbound DATA chunks for efficiency.
skipping to change at page 13, line 31 skipping to change at page 12, line 20
dynamically in order to meet the specific timing requirements of dynamically in order to meet the specific timing requirements of
the protocol being carried, but see the next rule: the protocol being carried, but see the next rule:
F3) Any delay applied to the sending of FORWARD TSN chunk SHOULD NOT F3) Any delay applied to the sending of FORWARD TSN chunk SHOULD NOT
exceed 200ms and MUST NOT exceed 500ms. In other words an exceed 200ms and MUST NOT exceed 500ms. In other words an
implementation MAY lower this value below 500ms but MUST NOT raise implementation MAY lower this value below 500ms but MUST NOT raise
it above 500ms. it above 500ms.
NOTE: Delaying the sending of FORWARD TSN chunks may cause delays NOTE: Delaying the sending of FORWARD TSN chunks may cause delays
in the receiver's ability to deliver other data being held at the in the receiver's ability to deliver other data being held at the
receiver for re-ordering. receiver for re-ordering. The values of 200ms and 500ms match the
required values for the delayed acknowledgement in RFC2960 [3]
since delaying a FORWARD TSN has the same consequences but in the
reverse direction.
F4) The detection criterion for out-of-order SACKs MUST remain the F4) The detection criterion for out-of-order SACKs MUST remain the
same as stated in RFC2960, that is, a SACK is only considered same as stated in RFC2960, that is, a SACK is only considered
out-of-order if the Cumulative TSN ACK carried in the SACK is out-of-order if the Cumulative TSN ACK carried in the SACK is
earlier than that of the previous received SACK (i.e., the earlier than that of the previous received SACK (i.e., the
comparison MUST NOT be made against "Advanced.Peer.Ack.Point"). comparison MUST NOT be made against "Advanced.Peer.Ack.Point").
F5) If the decision to "abandon" a chunk is made, no matter how such F5) If the decision to "abandon" a chunk is made, no matter how such
a decision is made, the appropriate congestion adjustment MUST be a decision is made, the appropriate congestion adjustment MUST be
made as specified in RFC2960 if the chunk would have been marked made as specified in RFC2960 if the chunk would have been marked
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supported by the sending side functionality of host A. All that is supported by the sending side functionality of host A. All that is
necessary is that the receiving side correctly handle the necessary is that the receiving side correctly handle the
Forward-TSN-Supported parameter as specified in Section 3.3, and Forward-TSN-Supported parameter as specified in Section 3.3, and
correctly handle the receipt of FORWARD TSN chunks as specified correctly handle the receipt of FORWARD TSN chunks as specified
below. below.
DATA chunk arrival at a PR-SCTP receiver proceeds exactly as for DATA DATA chunk arrival at a PR-SCTP receiver proceeds exactly as for DATA
chunk arrival at a base protocol SCTP receiver---that is, the chunk arrival at a base protocol SCTP receiver---that is, the
receiver MUST perform the same TSN handling including duplicate receiver MUST perform the same TSN handling including duplicate
detection, gap detection, SACK generation, cumulative TSN detection, gap detection, SACK generation, cumulative TSN
advancement, etc. as defined in RFC2960 [5]---with the following advancement, etc. as defined in RFC2960 [3]---with the following
exceptions and additions. exceptions and additions.
When a FORWARD TSN chunk arrives, the data receiver MUST first update When a FORWARD TSN chunk arrives, the data receiver MUST first update
its cumulative TSN point to the value carried in the FORWARD TSN its cumulative TSN point to the value carried in the FORWARD TSN
chunk, and then MUST further advance its cumulative TSN point locally chunk, and then MUST further advance its cumulative TSN point locally
if possible, as shown by the following example: if possible, as shown by the following example:
Assuming that the new cumulative TSN carried in the arrived Assuming that the new cumulative TSN carried in the arrived
FORWARD TSN is 103: FORWARD TSN is 103:
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FORWARD TSN chunk is found to be behind or at the current cumulative FORWARD TSN chunk is found to be behind or at the current cumulative
TSN point, the data receiver MUST treat this FORWARD TSN as TSN point, the data receiver MUST treat this FORWARD TSN as
out-of-date and MUST NOT update its Cumulative TSN. The receiver out-of-date and MUST NOT update its Cumulative TSN. The receiver
SHOULD send a SACK to its peer (the sender of the FORWARD TSN) since SHOULD send a SACK to its peer (the sender of the FORWARD TSN) since
such a duplicate may indicate the previous SACK was lost in the such a duplicate may indicate the previous SACK was lost in the
network. network.
Any time a FORWARD TSN chunk arrives, for the purposes of sending a Any time a FORWARD TSN chunk arrives, for the purposes of sending a
SACK, the receiver MUST follow the same rules as if a DATA chunk had SACK, the receiver MUST follow the same rules as if a DATA chunk had
been received (i.e., follow the delayed sack rules specified in been received (i.e., follow the delayed sack rules specified in
RFC2960 [5] section 6.2). RFC2960 [3] section 6.2).
Whenever a DATA chunk arrives with the 'U' bit set to '0' (indicating Whenever a DATA chunk arrives with the 'U' bit set to '0' (indicating
ordered delivery) and is out of order, the receiver must hold the ordered delivery) and is out of order, the receiver must hold the
chunk for reordering. Since it is possible with PR-SCTP that a DATA chunk for reordering. Since it is possible with PR-SCTP that a DATA
chunk being waited upon will not be retransmitted, special actions chunk being waited upon will not be retransmitted, special actions
will need to be taken upon the arrival of a FORWARD TSN. will need to be taken upon the arrival of a FORWARD TSN.
In particular, during processing of a FORWARD TSN, the receiver MUST In particular, during processing of a FORWARD TSN, the receiver MUST
use the stream sequence information to examine all of the listed use the stream sequence information to examine all of the listed
stream reordering queues, and immediately make available for delivery stream reordering queues, and immediately make available for delivery
skipping to change at page 16, line 22 skipping to change at page 14, line 40
standardize only the protocol, and leave the service definition as standardize only the protocol, and leave the service definition as
"implementation specific" or leave it to be defined in "implementation specific" or leave it to be defined in
"informational" documents. "informational" documents.
However, for those who may wish to write IETF standards for upper However, for those who may wish to write IETF standards for upper
layer protocols implemented over PR-SCTP, it is important to be able layer protocols implemented over PR-SCTP, it is important to be able
to refer to a standard definition of services provided. Therefore, to refer to a standard definition of services provided. Therefore,
this section provides an example definitions of one such service, this section provides an example definitions of one such service,
while also providing guidelines for the definition of additional while also providing guidelines for the definition of additional
services as required. Each such service may be proposed as a services as required. Each such service may be proposed as a
separate new standard. separate new informational RFC.
Section 4 is organized as follows: Section 4 is organized as follows:
Section 4.1 provides the definition of one specific PR-SCTP Section 4.1 provides the definition of one specific PR-SCTP
service: timed reliability. service: timed reliability.
Section 4.2 describes how a particular PR-SCTP service definition Section 4.2 describes how a particular PR-SCTP service definition
is requested by the upper layer during association establishment, is requested by the upper layer during association establishment,
and how the upper layer is notified if that request cannot be and how the upper layer is notified if that request cannot be
satisfied. satisfied.
skipping to change at page 16, line 47 skipping to change at page 15, line 18
Finally, Section 4.4 describes some additional usage notes that Finally, Section 4.4 describes some additional usage notes that
upper layer protocol designers and implementors may find helpful. upper layer protocol designers and implementors may find helpful.
4.1 PR-SCTP Service Definition for "timed reliability" 4.1 PR-SCTP Service Definition for "timed reliability"
The "timed reliability" service is a natural extension of the The "timed reliability" service is a natural extension of the
"lifetime" concept already present in the base SCTP protocol. "lifetime" concept already present in the base SCTP protocol.
When this service is requested for an SCTP association, it changes When this service is requested for an SCTP association, it changes
the meaning of the lifetime parameter specified in the SEND primitive the meaning of the lifetime parameter specified in the SEND primitive
(see Section 10.1, part (E) of RFC2960 [5]; note that the parameter (see Section 10.1, part (E) of RFC2960 [3]; note that the parameter
is spelled "life time" in that document.) is spelled "life time" in that document.)
In the base SCTP protocol, the lifetime parameter is used to avoid In the base SCTP protocol, the lifetime parameter is used to avoid
sending stale data. When a lifetime value is indicated for a sending stale data. When a lifetime value is indicated for a
particular message, SCTP cancels the sending of this message, and particular message and that lifetime expires, SCTP cancels the
notifies the ULP if the first transmission of the data does not take sending of this message, and notifies the ULP if the first
place (because of rwnd or cwnd limitations, or for any other reason) transmission of the data does not take place (because of rwnd or cwnd
before the lifetime expires. However, in the base protocol, if SCTP limitations, or for any other reason). However, in the base
has sent the first transmission before the lifetime expires, then the protocol, if SCTP has sent the first transmission before the lifetime
message MUST be sent as a normal reliable message. During episodes expires, then the message MUST be sent as a normal reliable message.
of congestion this is particularly unfortunate, as retransmission During episodes of congestion this is particularly unfortunate, as
wastes bandwidth that could have been used for other (non-lifetime retransmission wastes bandwidth that could have been used for other
expired) messages. (non-lifetime expired) messages.
When the "timed reliability" service is invoked, this latter When the "timed reliability" service is invoked, this latter
restriction is removed. Specifically, when the "timed reliability" restriction is removed. Specifically, when the "timed reliability"
service is in effect, the following rules govern all messages that service is in effect, the following rules govern all messages that
are sent with a lifetime parameter: are sent with a lifetime parameter:
TR1) If the lifetime parameter of a message is SCTP_LIFETIME_RELIABLE TR1) If the lifetime parameter of a message is SCTP_LIFETIME_RELIABLE
(or unspecified) that message is treated as a normal reliable SCTP (or unspecified see Section 5) that message is treated as a normal
message, just as in the base SCTP protocol. reliable SCTP message, just as in the base SCTP protocol.
TR2) If the lifetime parameter is not SCTP_LIFETIME_RELIABLE, then TR2) If the lifetime parameter is not SCTP_LIFETIME_RELIABLE (see
the SCTP sender MUST treat the message just as if it were a normal Section 5), then the SCTP sender MUST treat the message just as if
reliable SCTP message as long as the lifetime has not yet expired. it were a normal reliable SCTP message as long as the lifetime has
not yet expired.
TR3) Before assigning a TSN to any message, the SCTP sender MUST TR3) Before assigning a TSN to any message, the SCTP sender MUST
evaluate the lifetime of that message. If it is expired, the SCTP evaluate the lifetime of that message. If it is expired, the SCTP
sender MUST NOT assign a TSN to that message, but instead, SHOULD sender MUST NOT assign a TSN to that message, but instead, SHOULD
issue a notification to the upper layer and abandon the message. issue a notification to the upper layer and abandon the message.
TR4) Before transmitting or retransmitting a message for which a TSN TR4) Before transmitting or retransmitting a message for which a TSN
is already assigned, the SCTP sender MUST evaluate the lifetime of is already assigned, the SCTP sender MUST evaluate the lifetime of
the message. If the lifetime of the message is expired, the SCTP the message. If the lifetime of the message is expired, the SCTP
sender MUST "abandon" the message, as per the rules specified in sender MUST "abandon" the message, as per the rules specified in
Section 3.5. Section 3.5 marking that TSN as eligible for forward TSN. Note
that this meets the requirement G1 defined in Section 4.3
TR5) The sending SCTP MAY evaluate the lifetime of messages at TR5) The sending SCTP MAY evaluate the lifetime of messages at
anytime. Expired messages that have not been assigned a TSN MAY be anytime. Expired messages that have not been assigned a TSN MAY be
handled as per rule TR3. Expired messages that HAVE been assigned handled as per rule TR3. Expired messages that HAVE been assigned
a TSN MAY be handled as per rule TR4. a TSN MAY be handled as per rule TR4.
TR6) The sending application MUST NOT change the lifetime parameter TR6) The sending application MUST NOT change the lifetime parameter
once the message is passed to the sending SCTP. once the message is passed to the sending SCTP.
Implementation Note: Rules TR1 through TR4 are designed in such as Implementation Note: Rules TR1 through TR4 are designed in such a way
way to avoid requiring the implementer to maintain a separate timer as to avoid requiring the implementer to maintain a separate timer
for each message; instead, the lifetime need only be evaluated at for each message; instead, the lifetime need only be evaluated at
points in the life of the message where actions are already being points in the life of the message where actions are already being
taken, such as TSN assignment, transmission, or expiration of a taken, such as TSN assignment, transmission, or expiration of a
retransmission timeout. Rule TR5 is intended to give the SCTP retransmission timeout. Rule TR5 is intended to give the SCTP
implementor flexibility to evaluate lifetime at any other convenient implementor flexibility to evaluate lifetime at any other convenient
opportunity, WITHOUT requiring that lifetime be evaluated immediately opportunity, WITHOUT requiring that lifetime be evaluated immediately
at the point in time where it expires. at the point in time where it expires.
4.2 PR-SCTP Association Establishment 4.2 PR-SCTP Association Establishment
An upper layer protocol (ULP) that uses PR-SCTP may need to know An upper layer protocol (ULP) that uses PR-SCTP may need to know
whether PR-SCTP can be supported on a given association. Therefore, whether PR-SCTP can be supported on a given association. Therefore,
the ULP needs to have some indication of whether the FORWARD-TSN the ULP needs to have some indication of whether the FORWARD-TSN
chunk is supported by its peer. chunk is supported by its peer.
Section 10.1 of RFC2960 [5] describes abstract primitives for the Section 10.1 of RFC2960 [3] describes abstract primitives for the
ULP-to-SCTP interface, while noting that "individual implementations ULP-to-SCTP interface, while noting that "individual implementations
must define their own exact format, and may provide combinations or must define their own exact format, and may provide combinations or
subsets of the basic functions in single calls." subsets of the basic functions in single calls."
In this section, we describe one additional return value that may be In this section, we describe one additional return value that may be
added to the ASSOCIATE primitive to allow an SCTP service user to added to the ASSOCIATE primitive to allow an SCTP service user to
indicate whether the FORWARD-TSN chunk is supported by its peer. indicate whether the FORWARD-TSN chunk is supported by its peer.
RFC2960 indicates that the associate primitive "allows the upper RFC2960 indicates that the ASSOCIATE primitive "allows the upper
layer to initiate an association to a specific peer endpoint". It is layer to initiate an association to a specific peer endpoint". It is
structured as follows: structured as follows:
Format: ASSOCIATE(local SCTP instance name, destination transport addr, Format: ASSOCIATE(local SCTP instance name, destination transport addr,
outbound stream count) outbound stream count)
-> association id [,destination transport addr list] -> association id [,destination transport addr list]
[,outbound stream count] [,outbound stream count]
This extension adds one new OPTIONAL return value, such that the new This extension adds one new OPTIONAL return value, such that the new
primitive reads as follows: primitive reads as follows:
skipping to change at page 19, line 14 skipping to change at page 17, line 32
(1) true indicates that FORWARD TSN is supported by the peer. (1) true indicates that FORWARD TSN is supported by the peer.
4.3 Guidelines for defining other PR-SCTP Services 4.3 Guidelines for defining other PR-SCTP Services
Other PR-SCTP services may be defined and implemented as dictated by Other PR-SCTP services may be defined and implemented as dictated by
the needs of upper layer protocols. If such upper layer protocols the needs of upper layer protocols. If such upper layer protocols
are to be standardized and require some particular PR-SCTP service are to be standardized and require some particular PR-SCTP service
other than the one defined in this document (i.e., "timed other than the one defined in this document (i.e., "timed
reliability") then those additional PR-SCTP services should also be reliability") then those additional PR-SCTP services should also be
specified and standardized. specified and standardized in an informational RFC.
It is suggested that any such additional service definitions be It is suggested that any such additional service definitions be
modeled after the contents of Section 4.1 . In particular, the modeled after the contents of Section 4.1 . In particular, the
service definition should provide: service definition should provide:
1. A description of how the service user specifies any parameters 1. A description of how the service user specifies any parameters
that need to be associated with a particular message (and/or any that need to be associated with a particular message (and/or any
other communication that takes place between the application and other communication that takes place between the application and
the SCTP transport sender) that provides the SCTP transport the SCTP transport sender) that provides the SCTP transport
sender with the information needed to determine when to give up sender with the information needed to determine when to give up
on transmission of a particular message. on transmission of a particular message.
Preferably this description should reference the primitives in Preferably this description should reference the primitives in
the abstract API provided in Section 10 of RFC2960 [5], the abstract API provided in Section 10 of RFC2960 [3],
indicating any: indicating any:
* changes to the interpretation of the existing parameters of * changes to the interpretation of the existing parameters of
existing primitives, existing primitives,
* additional parameters to be added to existing primitives * additional parameters to be added to existing primitives
(these should be OPTIONAL, and default values should be (these should be OPTIONAL, and default values should be
indicated), indicated),
* additional primitives that may be needed. * additional primitives that may be needed.
2. A description of the rules used by the sender side implementation 2. A description of the rules used by the sender side implementation
to determine when to give up on messages that have not yet been to determine when to give up on messages that have not yet been
assigned a TSN. This description should also indicate what assigned a TSN. This description should also indicate what
protocol events trigger the evaluation, and what actions to take protocol events trigger the evaluation, and what actions to take
skipping to change at page 21, line 5 skipping to change at page 19, line 8
4.4 Usage Notes 4.4 Usage Notes
Detecting missing data in a PR-SCTP stream is useful for some Detecting missing data in a PR-SCTP stream is useful for some
applications (e.g. Fiber channel or SCSI over IP). With PR-SCTP this applications (e.g. Fiber channel or SCSI over IP). With PR-SCTP this
becomes possible - the upper layer simply needs to examine the stream becomes possible - the upper layer simply needs to examine the stream
sequence number of the arrived user messages of that stream to detect sequence number of the arrived user messages of that stream to detect
any missing data. Note, this detection only works when all the any missing data. Note, this detection only works when all the
messages on that stream are sent in order, i.e., the "U" bit is not messages on that stream are sent in order, i.e., the "U" bit is not
set. set.
5. Acknowledgments 5. Variables
This section defines variables used throughout this document:
SCTP_LIFETIME_RELIABLE - A user interface indication defined by an
implementation and used to indicate when a message is to be
considered fully reliable.
6. Acknowledgments
The authors would like to thank Brian Bidulock, Scott Bradner, Jon The authors would like to thank Brian Bidulock, Scott Bradner, Jon
Berger, Armando L. Caro Jr., John Loughney, Ivan Arias Rodriguez, Ian Berger, Armando L. Caro Jr., John Loughney, Jon Peterson, Ivan Arias
Rytina, Chip Sharp, and others for their comments. Rodriguez, Ian Rytina, Chip Sharp, and others for their comment.s
6. Security Considerations 7. Security Considerations
This document does not introduce any new security concerns to SCTP This document does not introduce any new security concerns to SCTP
other than the ones already documented in RFC2960 [5]. In particular other than the ones already documented in RFC2960 [3]. In particular
this document shares the same security issues as unordered data this document shares the same security issues as unordered data
within RFC2960 [5]. An application using the PR-SCTP extension should within RFC2960 [3] identified by RFC3436 [5]. An application using
not use transport layer security. Further details can be found in the PR-SCTP extension should not use transport layer security;
RFC3436 [4]. further details can be found in RFC3436 [5].
7. IANA Considerations 8. IANA Considerations
One new chunk type is added to SCTP ('0xC0') by this document. One new chunk type is added to SCTP (192) by this document.
One new parameter type code is defined by this document to be added One new parameter type code is defined by this document to be added
to SCTP ('0xC000'). to SCTP (49152).
References
[1] Clark, D. and D. Tennenhouse, "Architectural Considerations for Normative references
a New Generation of Protocols", SIGCOMM 1990 pp. 200-208,
September 1990.
[2] Bradner, S., "The Internet Standards Process -- Revision 3", BCP [1] Bradner, S., "The Internet Standards Process -- Revision 3", BCP
9, RFC 2026, October 1996. 9, RFC 2026, October 1996.
[3] Bradner, S., "Key words for use in RFCs to Indicate Requirement [2] Bradner, S., "Key words for use in RFCs to Indicate Requirement
Levels", BCP 14, RFC 2119, March 1997. Levels", BCP 14, RFC 2119, March 1997.
[4] Jungmaier, A., Rescorla, E. and M. Tuexen, "TLS over SCTP", RFC [3] Stewart, R., Xie, Q., Morneault, K., Sharp, C., Schwarzbauer,
3436, December 2002.
[5] Stewart, R., Xie, Q., Morneault, K., Sharp, C., Schwarzbauer,
H., Taylor, T., Rytina, I., Kalla, M., Zhang, L. and V. Paxson, H., Taylor, T., Rytina, I., Kalla, M., Zhang, L. and V. Paxson,
"Stream Control Transmission Protocol", RFC 2960, October 2000. "Stream Control Transmission Protocol", RFC 2960, October 2000.
Informational References
[4] Clark, D. and D. Tennenhouse, "Architectural Considerations for
a New Generation of Protocols", SIGCOMM 1990 pp. 200-208,
September 1990.
[5] Jungmaier, A., Rescorla, E. and M. Tuexen, "TLS over SCTP", RFC
3436, December 2002.
Authors' Addresses Authors' Addresses
Randall R. Stewart Randall R. Stewart
Cisco Systems, Inc. Cisco Systems, Inc.
8725 West Higgins Road 8725 West Higgins Road
Suite 300 Suite 300
Chicago, IL 60631 Chicago, IL 60631
USA USA
Phone: +1-815-477-2127 Phone: +1-815-477-2127
skipping to change at page 25, line 20 skipping to change at page 21, line 4
Phone: +1-847-632-3028 Phone: +1-847-632-3028
EMail: qxie1@email.mot.com EMail: qxie1@email.mot.com
Michael Tuexen Michael Tuexen
Univ. of Applied Sciences Muenster Univ. of Applied Sciences Muenster
Stegerwaldstr. 39 Stegerwaldstr. 39
48565 Steinfurt 48565 Steinfurt
Germany Germany
EMail: tuexen@fh-muenster.de EMail: tuexen@fh-muenster.de
Phillip T. Conrad Phillip T. Conrad
Temple University University of Delaware
CIS Department Department of Computer and Information Sciences
Room 303, Computer Building (038-24) Newark, DE 19716
1805 N. Broad St.
Philadelphia, PA 19122
US US
Phone: +1 215 204 7910 Phone: +1 302 831 8622
EMail: conrad@acm.org EMail: conrad@acm.org
URI: http://www.cis.temple.edu/~conrad URI: http://www.cis.udel.edu/~pconrad
Intellectual Property Statement Intellectual Property Statement
The IETF takes no position regarding the validity or scope of any The IETF takes no position regarding the validity or scope of any
intellectual property or other rights that might be claimed to intellectual property or other rights that might be claimed to
pertain to the implementation or use of the technology described in pertain to the implementation or use of the technology described in
this document or the extent to which any license under such rights this document or the extent to which any license under such rights
might or might not be available; neither does it represent that it might or might not be available; neither does it represent that it
has made any effort to identify any such rights. Information on the has made any effort to identify any such rights. Information on the
IETF's procedures with respect to rights in standards-track and IETF's procedures with respect to rights in standards-track and
 End of changes. 

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