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Versions: (draft-tuexen-tsvwg-rfc4960-errata) 00 01 02 03 04 05 06 07 08

Network Working Group                                         R. Stewart
Internet-Draft                                             Netflix, Inc.
Intended status: Informational                                 M. Tuexen
Expires: April 25, 2019                 Muenster Univ. of Appl. Sciences
                                                              M. Proshin
                                                                Ericsson
                                                        October 22, 2018


                       RFC 4960 Errata and Issues
                 draft-ietf-tsvwg-rfc4960-errata-08.txt

Abstract

   This document is a compilation of issues found since the publication
   of RFC4960 in September 2007 based on experience with implementing,
   testing, and using SCTP along with the suggested fixes.  This
   document provides deltas to RFC4960 and is organized in a time
   ordered way.  The issues are listed in the order they were brought
   up.  Because some text is changed several times the last delta in the
   text is the one which should be applied.  In addition to the delta a
   description of the problem and the details of the solution are also
   provided.

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at https://datatracker.ietf.org/drafts/current/.

   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."

   This Internet-Draft will expire on April 25, 2019.

Copyright Notice

   Copyright (c) 2018 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents



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   (https://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   3
   2.  Conventions . . . . . . . . . . . . . . . . . . . . . . . . .   4
   3.  Corrections to RFC 4960 . . . . . . . . . . . . . . . . . . .   4
     3.1.  Path Error Counter Threshold Handling . . . . . . . . . .   4
     3.2.  Upper Layer Protocol Shutdown Request Handling  . . . . .   5
     3.3.  Registration of New Chunk Types . . . . . . . . . . . . .   6
     3.4.  Variable Parameters for INIT Chunks . . . . . . . . . . .   7
     3.5.  CRC32c Sample Code on 64-bit Platforms  . . . . . . . . .   8
     3.6.  Endpoint Failure Detection  . . . . . . . . . . . . . . .   9
     3.7.  Data Transmission Rules . . . . . . . . . . . . . . . . .  10
     3.8.  T1-Cookie Timer . . . . . . . . . . . . . . . . . . . . .  11
     3.9.  Miscellaneous Typos . . . . . . . . . . . . . . . . . . .  12
     3.10. CRC32c Sample Code  . . . . . . . . . . . . . . . . . . .  19
     3.11. partial_bytes_acked after T3-rtx Expiration . . . . . . .  20
     3.12. Order of Adjustments of partial_bytes_acked and cwnd  . .  21
     3.13. HEARTBEAT ACK and the association error counter . . . . .  22
     3.14. Path for Fast Retransmission  . . . . . . . . . . . . . .  23
     3.15. Transmittal in Fast Recovery  . . . . . . . . . . . . . .  24
     3.16. Initial Value of ssthresh . . . . . . . . . . . . . . . .  25
     3.17. Automatically Confirmed Addresses . . . . . . . . . . . .  26
     3.18. Only One Packet after Retransmission Timeout  . . . . . .  27
     3.19. INIT ACK Path for INIT in COOKIE-WAIT State . . . . . . .  28
     3.20. Zero Window Probing and Unreachable Primary Path  . . . .  29
     3.21. Normative Language in Section 10  . . . . . . . . . . . .  30
     3.22. Increase of partial_bytes_acked in Congestion Avoidance .  33
     3.23. Inconsistency in Notifications Handling . . . . . . . . .  34
     3.24. SACK.Delay Not Listed as a Protocol Parameter . . . . . .  40
     3.25. Processing of Chunks in an Incoming SCTP Packet . . . . .  42
     3.26. CWND Increase in Congestion Avoidance Phase . . . . . . .  43
     3.27. Refresh of cwnd and ssthresh after Idle Period  . . . . .  46
     3.28. Window Updates After Receiver Window Opens Up . . . . . .  47
     3.29. Path of DATA and Reply Chunks . . . . . . . . . . . . . .  48
     3.30. Outstanding Data, Flightsize and Data In Flight Key Terms  50
     3.31. CWND Degradation due to Max.Burst . . . . . . . . . . . .  52
     3.32. Reduction of RTO.Initial  . . . . . . . . . . . . . . . .  53
     3.33. Ordering of Bundled SACK and ERROR Chunks . . . . . . . .  55
     3.34. Undefined Parameter Returned by RECEIVE Primitive . . . .  56
     3.35. DSCP Changes  . . . . . . . . . . . . . . . . . . . . . .  57



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     3.36. Inconsistent Handling of ICMPv4 and ICMPv6 Messages . . .  58
     3.37. Handling of Soft Errors . . . . . . . . . . . . . . . . .  60
     3.38. Honoring CWND . . . . . . . . . . . . . . . . . . . . . .  60
     3.39. Zero Window Probing . . . . . . . . . . . . . . . . . . .  62
     3.40. Updating References Regarding ECN . . . . . . . . . . . .  64
     3.41. Host Name Address Parameter Deprecated  . . . . . . . . .  66
     3.42. Conflicting Text Regarding the Supported Address Types
           Parameter . . . . . . . . . . . . . . . . . . . . . . . .  70
     3.43. Integration of RFC 6096 . . . . . . . . . . . . . . . . .  71
     3.44. Integration of RFC 6335 . . . . . . . . . . . . . . . . .  73
     3.45. Integration of RFC 7053 . . . . . . . . . . . . . . . . .  75
     3.46. CRC32c Code Improvements  . . . . . . . . . . . . . . . .  79
     3.47. Clarification of Gap Ack Blocks in SACK Chunks  . . . . .  89
     3.48. Handling of SSN Wrap Arounds  . . . . . . . . . . . . . .  91
     3.49. Update RFC 2119 Boilerplate . . . . . . . . . . . . . . .  92
     3.50. Missed Text Removal . . . . . . . . . . . . . . . . . . .  93
   4.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  94
   5.  Security Considerations . . . . . . . . . . . . . . . . . . .  94
   6.  Acknowledgments . . . . . . . . . . . . . . . . . . . . . . .  94
   7.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  95
     7.1.  Normative References  . . . . . . . . . . . . . . . . . .  95
     7.2.  Informative References  . . . . . . . . . . . . . . . . .  95
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  96

1.  Introduction

   This document contains a compilation of all defects found up until
   the publication of this document for [RFC4960] specifying the Stream
   Control Transmission Protocol (SCTP).  These defects may be of an
   editorial or technical nature.  This document may be thought of as a
   companion document to be used in the implementation of SCTP to
   clarify errors in the original SCTP document.

   This document provides a history of the changes that will be compiled
   into a BIS document for [RFC4960].  It is structured similar to
   [RFC4460].

   Each error will be detailed within this document in the form of:

   o  The problem description,
   o  The text quoted from [RFC4960],
   o  The replacement text that should be placed into an upcoming BIS
      document,
   o  A description of the solution.

   Note that when reading this document one must use care to assure that
   a field or item is not updated further on within the document.  Since
   this document is a historical record of the sequential changes that



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   have been found necessary at various inter-op events and through
   discussion on the list, the last delta in the text is the one which
   should be applied.

2.  Conventions

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
   "OPTIONAL" in this document are to be interpreted as described in
   BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all
   capitals, as shown here.

3.  Corrections to RFC 4960

   [NOTE to RFC-Editor:

      References to obsoleted RFCs are in OLD TEXT sections and have the
      corresponding references to the obsoleting RFCs in the NEW TEXT
      sections.  In addition to this, there are some references to the
      obsoleted [RFC2960], which are intended.

   ]

3.1.  Path Error Counter Threshold Handling

3.1.1.  Description of the Problem

   The handling of the 'Path.Max.Retrans' parameter is described in
   Section 8.2 and Section 8.3 of [RFC4960] in an inconsistent way.
   Whereas Section 8.2 describes that a path is marked inactive when the
   path error counter exceeds the threshold, Section 8.3 says the path
   is marked inactive when the path error counter reaches the threshold.

   This issue was reported as an Errata for [RFC4960] with Errata ID
   1440.

3.1.2.  Text Changes to the Document














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   ---------
   Old text: (Section 8.3)
   ---------

   When the value of this counter reaches the protocol parameter
   'Path.Max.Retrans', the endpoint should mark the corresponding
   destination address as inactive if it is not so marked, and may also
   optionally report to the upper layer the change of reachability of
   this destination address.  After this, the endpoint should continue
   HEARTBEAT on this destination address but should stop increasing the
   counter.

   ---------
   New text: (Section 8.3)
   ---------

   When the value of this counter exceeds the protocol parameter
   'Path.Max.Retrans', the endpoint SHOULD mark the corresponding
   destination address as inactive if it is not so marked, and MAY also
   optionally report to the upper layer the change of reachability of
   this destination address.  After this, the endpoint SHOULD continue
   HEARTBEAT on this destination address but SHOULD stop increasing the
   counter.

   This text has been modified by multiple errata.  It is further
   updated in Section 3.23.

3.1.3.  Solution Description

   The intended state change should happen when the threshold is
   exceeded.

3.2.  Upper Layer Protocol Shutdown Request Handling

3.2.1.  Description of the Problem

   Section 9.2 of [RFC4960] describes the handling of received SHUTDOWN
   chunks in the SHUTDOWN-RECEIVED state instead of the handling of
   shutdown requests from its upper layer in this state.

   This issue was reported as an Errata for [RFC4960] with Errata ID
   1574.

3.2.2.  Text Changes to the Document







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   ---------
   Old text: (Section 9.2)
   ---------

   Once an endpoint has reached the SHUTDOWN-RECEIVED state, it MUST NOT
   send a SHUTDOWN in response to a ULP request, and should discard
   subsequent SHUTDOWN chunks.

   ---------
   New text: (Section 9.2)
   ---------

   Once an endpoint has reached the SHUTDOWN-RECEIVED state, it MUST
   ignore ULP shutdown requests, but MUST continue responding
   to SHUTDOWN chunks from its peer.

   This text is in final form, and is not further updated in this
   document.

3.2.3.  Solution Description

   The text never intended the SCTP endpoint to ignore SHUTDOWN chunks
   from its peer.  If it did, the endpoints could never gracefully
   terminate associations in some cases.

3.3.  Registration of New Chunk Types

3.3.1.  Description of the Problem

   Section 14.1 of [RFC4960] should deal with new chunk types, however,
   the text refers to parameter types.

   This issue was reported as an Errata for [RFC4960] with Errata ID
   2592.

3.3.2.  Text Changes to the Document















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   ---------
   Old text: (Section 14.1)
   ---------

   The assignment of new chunk parameter type codes is done through an
   IETF Consensus action, as defined in [RFC2434].  Documentation of the
   chunk parameter MUST contain the following information:

   ---------
   New text: (Section 14.1)
   ---------

   The assignment of new chunk type codes is done through an
   IETF Consensus action, as defined in [RFC8126].  Documentation of the
   chunk type MUST contain the following information:

   This text has been modified by multiple errata.  It is further
   updated in Section 3.43.

3.3.3.  Solution Description

   Refer to chunk types as intended and change reference to [RFC8126].

3.4.  Variable Parameters for INIT Chunks

3.4.1.  Description of the Problem

   Newlines in wrong places break the layout of the table of variable
   parameters for the INIT chunk in Section 3.3.2 of [RFC4960].

   This issue was reported as an Errata for [RFC4960] with Errata ID
   3291 and Errata ID 3804.

3.4.2.  Text Changes to the Document

















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   ---------
   Old text: (Section 3.3.2)
   ---------

   Variable Parameters                  Status     Type Value
   -------------------------------------------------------------
   IPv4 Address (Note 1)               Optional    5 IPv6 Address
   (Note 1)               Optional    6 Cookie Preservative
   Optional    9 Reserved for ECN Capable (Note 2)   Optional
   32768 (0x8000) Host Name Address (Note 3)          Optional
   11 Supported Address Types (Note 4)    Optional    12

   ---------
   New text: (Section 3.3.2)
   ---------

   Variable Parameters                  Status     Type Value
   -------------------------------------------------------------
   IPv4 Address (Note 1)               Optional    5
   IPv6 Address (Note 1)               Optional    6
   Cookie Preservative                 Optional    9
   Reserved for ECN Capable (Note 2)   Optional    32768 (0x8000)
   Host Name Address (Note 3)          Optional    11
   Supported Address Types (Note 4)    Optional    12

   This text is in final form, and is not further updated in this
   document.

3.4.3.  Solution Description

   Fix the formatting of the table.

3.5.  CRC32c Sample Code on 64-bit Platforms

3.5.1.  Description of the Problem

   The sample code for computing the CRC32c provided in [RFC4960]
   assumes that a variable of type unsigned long uses 32 bits.  This is
   not true on some 64-bit platforms (for example the ones using LP64).

   This issue was reported as an Errata for [RFC4960] with Errata ID
   3423.

3.5.2.  Text Changes to the Document







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   ---------
   Old text: (Appendix C)
   ---------

   unsigned long
   generate_crc32c(unsigned char *buffer, unsigned int length)
   {
     unsigned int i;
     unsigned long crc32 = ~0L;

   ---------
   New text: (Appendix C)
   ---------

   unsigned long
   generate_crc32c(unsigned char *buffer, unsigned int length)
   {
     unsigned int i;
     unsigned long crc32 = 0xffffffffL;

   This text has been modified by multiple errata.  It is further
   updated in Section 3.10 and in Section 3.46.

3.5.3.  Solution Description

   Use 0xffffffffL instead of ~0L which gives the same value on
   platforms using 32 bits or 64 bits for variables of type unsigned
   long.

3.6.  Endpoint Failure Detection

3.6.1.  Description of the Problem

   The handling of the association error counter defined in Section 8.1
   of [RFC4960] can result in an association failure even if the path
   used for data transmission is available, but idle.

   This issue was reported as an Errata for [RFC4960] with Errata ID
   3788.

3.6.2.  Text Changes to the Document










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   ---------
   Old text: (Section 8.1)
   ---------

   An endpoint shall keep a counter on the total number of consecutive
   retransmissions to its peer (this includes retransmissions to all the
   destination transport addresses of the peer if it is multi-homed),
   including unacknowledged HEARTBEAT chunks.

   ---------
   New text: (Section 8.1)
   ---------

   An endpoint SHOULD keep a counter on the total number of consecutive
   retransmissions to its peer (this includes data retransmissions
   to all the destination transport addresses of the peer if it is
   multi-homed), including the number of unacknowledged HEARTBEAT
   chunks observed on the path which is currently used for data
   transfer. Unacknowledged HEARTBEAT chunks observed on paths
   different from the path currently used for data transfer SHOULD
   NOT increment the association error counter, as this could lead
   to association closure even if the path which is currently used for
   data transfer is available (but idle).

   This text has been modified by multiple errata.  It is further
   updated in Section 3.23.

3.6.3.  Solution Description

   A more refined handling for the association error counter is defined.

3.7.  Data Transmission Rules

3.7.1.  Description of the Problem

   When integrating the changes to Section 6.1 A) of [RFC2960] as
   described in Section 2.15.2 of [RFC4460] some text was duplicated and
   became the final paragraph of Section 6.1 A) of [RFC4960].

   This issue was reported as an Errata for [RFC4960] with Errata ID
   4071.

3.7.2.  Text Changes to the Document








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   ---------
   Old text: (Section 6.1 A))
   ---------

   The sender MUST also have an algorithm for sending new DATA chunks
   to avoid silly window syndrome (SWS) as described in [RFC0813].
   The algorithm can be similar to the one described in Section
   4.2.3.4 of [RFC1122].

   However, regardless of the value of rwnd (including if it is 0),
   the data sender can always have one DATA chunk in flight to the
   receiver if allowed by cwnd (see rule B below).  This rule allows
   the sender to probe for a change in rwnd that the sender missed
   due to the SACK having been lost in transit from the data receiver
   to the data sender.

   ---------
   New text: (Section 6.1 A))
   ---------

   The sender MUST also have an algorithm for sending new DATA chunks
   to avoid silly window syndrome (SWS) as described in [RFC1122].
   The algorithm can be similar to the one described in Section
   4.2.3.4 of [RFC1122].

   This text is in final form, and is not further updated in this
   document.

3.7.3.  Solution Description

   Last paragraph of Section 6.1 A) removed as intended in
   Section 2.15.2 of [RFC4460].

3.8.  T1-Cookie Timer

3.8.1.  Description of the Problem

   Figure 4 of [RFC4960] illustrates the SCTP association setup.
   However, it incorrectly shows that the T1-init timer is used in the
   COOKIE-ECHOED state whereas the T1-cookie timer should have been used
   instead.

   This issue was reported as an Errata for [RFC4960] with Errata ID
   4400.







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3.8.2.  Text Changes to the Document

   ---------
   Old text: (Section 5.1.6, Figure 4)
   ---------

   COOKIE ECHO [Cookie_Z] ------\
   (Start T1-init timer)         \
   (Enter COOKIE-ECHOED state)    \---> (build TCB enter ESTABLISHED
                                         state)
                                  /---- COOKIE-ACK
                                 /
   (Cancel T1-init timer, <-----/
    Enter ESTABLISHED state)

   ---------
   New text: (Section 5.1.6, Figure 4)
   ---------

   COOKIE ECHO [Cookie_Z] ------\
   (Start T1-cookie timer)       \
   (Enter COOKIE-ECHOED state)    \---> (build TCB enter ESTABLISHED
                                         state)
                                  /---- COOKIE-ACK
                                 /
   (Cancel T1-cookie timer, <---/
    Enter ESTABLISHED state)

   This text has been modified by multiple errata.  It is further
   updated in Section 3.9.

3.8.3.  Solution Description

   Change the figure such that the T1-cookie timer is used instead of
   the T1-init timer.

3.9.  Miscellaneous Typos

3.9.1.  Description of the Problem

   While processing [RFC4960] some typos were not caught.

   One typo was reported as an Errata for [RFC4960] with Errata ID 5003.








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3.9.2.  Text Changes to the Document

   ---------
   Old text: (Section 1.6)
   ---------

   Transmission Sequence Numbers wrap around when they reach 2**32 - 1.
   That is, the next TSN a DATA chunk MUST use after transmitting TSN =
   2*32 - 1 is TSN = 0.

   ---------
   New text: (Section 1.6)
   ---------

   Transmission Sequence Numbers wrap around when they reach 2**32 - 1.
   That is, the next TSN a DATA chunk MUST use after transmitting TSN =
   2**32 - 1 is TSN = 0.

   This text is in final form, and is not further updated in this
   document.

   ---------
   Old text: (Section 3.3.10.9)
   ---------

   No User Data: This error cause is returned to the originator of a

   DATA chunk if a received DATA chunk has no user data.

   ---------
   New text: (Section 3.3.10.9)
   ---------

   No User Data: This error cause is returned to the originator of a
   DATA chunk if a received DATA chunk has no user data.

   This text is in final form, and is not further updated in this
   document.













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   ---------
   Old text: (Section 6.7, Figure 9)
   ---------

   Endpoint A                                    Endpoint Z {App
   sends 3 messages; strm 0} DATA [TSN=6,Strm=0,Seq=2] ----------
   -----> (ack delayed) (Start T3-rtx timer)

   DATA [TSN=7,Strm=0,Seq=3] --------> X (lost)

   DATA [TSN=8,Strm=0,Seq=4] ---------------> (gap detected,
                                               immediately send ack)
                                   /----- SACK [TSN Ack=6,Block=1,
                                  /             Start=2,End=2]
                           <-----/ (remove 6 from out-queue,
    and mark 7 as "1" missing report)

   ---------
   New text: (Section 6.7, Figure 9)
   ---------

   Endpoint A                                    Endpoint Z
   {App sends 3 messages; strm 0}
   DATA [TSN=6,Strm=0,Seq=2] ---------------> (ack delayed)
   (Start T3-rtx timer)

   DATA [TSN=7,Strm=0,Seq=3] --------> X (lost)

   DATA [TSN=8,Strm=0,Seq=4] ---------------> (gap detected,
                                               immediately send ack)
                                   /----- SACK [TSN Ack=6,Block=1,
                                  /             Start=2,End=2]
                           <-----/
   (remove 6 from out-queue,
    and mark 7 as "1" missing report)

   This text is in final form, and is not further updated in this
   document.













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   ---------
   Old text: (Section 6.10)
   ---------

   An endpoint bundles chunks by simply including multiple chunks in one
   outbound SCTP packet.  The total size of the resultant IP datagram,

   including the SCTP packet and IP headers, MUST be less that or equal
   to the current Path MTU.

   ---------
   New text: (Section 6.10)
   ---------

   An endpoint bundles chunks by simply including multiple chunks in one
   outbound SCTP packet.  The total size of the resultant IP datagram,
   including the SCTP packet and IP headers, MUST be less than or equal
   to the current PMTU.

   This text is in final form, and is not further updated in this
   document.

   ---------
   Old text: (Section 10.1 O))
   ---------

   o  Receive Unacknowledged Message

      Format: RECEIVE_UNACKED(data retrieval id, buffer address, buffer
              size, [,stream id] [, stream sequence number] [,partial
              flag] [,payload protocol-id])

   ---------
   New text: (Section 10.1 O))
   ---------

   O) Receive Unacknowledged Message

      Format: RECEIVE_UNACKED(data retrieval id, buffer address, buffer
              size [,stream id] [,stream sequence number] [,partial
              flag] [,payload protocol-id])

   This text is in final form, and is not further updated in this
   document.







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   ---------
   Old text: (Section 10.1 M))
   ---------

   M) Set Protocol Parameters

      Format: SETPROTOCOLPARAMETERS(association id,
              [,destination transport address,]
              protocol parameter list)

   ---------
   New text: (Section 10.1 M))
   ---------

   M) Set Protocol Parameters

      Format: SETPROTOCOLPARAMETERS(association id,
              [destination transport address,]
              protocol parameter list)

   This text is in final form, and is not further updated in this
   document.

   ---------
   Old text: (Appendix C)
   ---------

   ICMP2) An implementation MAY ignore all ICMPv6 messages where the
          type field is not "Destination Unreachable", "Parameter
          Problem",, or "Packet Too Big".

   ---------
   New text: (Appendix C)
   ---------

   ICMP2) An implementation MAY ignore all ICMPv6 messages where the
          type field is not "Destination Unreachable", "Parameter
          Problem", or "Packet Too Big".

   This text is in final form, and is not further updated in this
   document.










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   ---------
   Old text: (Appendix C)
   ---------

   ICMP7) If the ICMP message is either a v6 "Packet Too Big" or a v4
          "Fragmentation Needed", an implementation MAY process this
          information as defined for PATH MTU discovery.

   ---------
   New text: (Appendix C)
   ---------

   ICMP7) If the ICMP message is either a v6 "Packet Too Big" or a v4
          "Fragmentation Needed", an implementation MAY process this
          information as defined for PMTU discovery.

   This text is in final form, and is not further updated in this
   document.

   ---------
   Old text: (Section 5.4)
   ---------

   2)  For the receiver of the COOKIE ECHO, the only CONFIRMED address
      is the one to which the INIT-ACK was sent.

   ---------
   New text: (Section 5.4)
   ---------

   2)  For the receiver of the COOKIE ECHO, the only CONFIRMED address
      is the one to which the INIT ACK was sent.

   This text is in final form, and is not further updated in this
   document.
















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   ---------
   Old text: (Section 5.1.6, Figure 4)
   ---------

   COOKIE ECHO [Cookie_Z] ------\
   (Start T1-init timer)         \
   (Enter COOKIE-ECHOED state)    \---> (build TCB enter ESTABLISHED
                                         state)
                                  /---- COOKIE-ACK
                                 /
   (Cancel T1-init timer, <-----/
    Enter ESTABLISHED state)

   ---------
   New text: (Section 5.1.6, Figure 4)
   ---------

   COOKIE ECHO [Cookie_Z] ------\
   (Start T1-cookie timer)       \
   (Enter COOKIE-ECHOED state)    \---> (build TCB enter ESTABLISHED
                                         state)
                                  /---- COOKIE ACK
                                 /
   (Cancel T1-cookie timer, <---/
    Enter ESTABLISHED state)

   This text has been modified by multiple errata.  It includes
   modifications from Section 3.8.  It is in final form, and is not
   further updated in this document.

   ---------
   Old text: (Section 5.2.5)
   ---------

   5.2.5.  Handle Duplicate COOKIE-ACK.

   ---------
   New text: (Section 5.2.5)
   ---------

   5.2.5.  Handle Duplicate COOKIE ACK.

   This text is in final form, and is not further updated in this
   document.







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   ---------
   Old text: (Section 8.3)
   ---------

   By default, an SCTP endpoint SHOULD monitor the reachability of the
   idle destination transport address(es) of its peer by sending a
   HEARTBEAT chunk periodically to the destination transport
   address(es).  HEARTBEAT sending MAY begin upon reaching the
   ESTABLISHED state and is discontinued after sending either SHUTDOWN
   or SHUTDOWN-ACK.  A receiver of a HEARTBEAT MUST respond to a
   HEARTBEAT with a HEARTBEAT-ACK after entering the COOKIE-ECHOED state
   (INIT sender) or the ESTABLISHED state (INIT receiver), up until
   reaching the SHUTDOWN-SENT state (SHUTDOWN sender) or the SHUTDOWN-
   ACK-SENT state (SHUTDOWN receiver).

   ---------
   New text: (Section 8.3)
   ---------
   By default, an SCTP endpoint SHOULD monitor the reachability of the
   idle destination transport address(es) of its peer by sending a
   HEARTBEAT chunk periodically to the destination transport
   address(es).  HEARTBEAT sending MAY begin upon reaching the
   ESTABLISHED state and is discontinued after sending either SHUTDOWN
   or SHUTDOWN ACK.  A receiver of a HEARTBEAT MUST respond to a
   HEARTBEAT with a HEARTBEAT ACK after entering the COOKIE-ECHOED state
   (INIT sender) or the ESTABLISHED state (INIT receiver), up until
   reaching the SHUTDOWN-SENT state (SHUTDOWN sender) or the SHUTDOWN-
   ACK-SENT state (SHUTDOWN receiver).

   This text is in final form, and is not further updated in this
   document.

3.9.3.  Solution Description

   Typos fixed.

3.10.  CRC32c Sample Code

3.10.1.  Description of the Problem

   The CRC32c computation is described in Appendix B of [RFC4960].
   However, the corresponding sample code and its explanation appears at
   the end of Appendix C, which deals with ICMP handling.








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3.10.2.  Text Changes to the Document

   Move all of Appendix C starting with the following sentence to the
   end of Appendix B.

   The following non-normative sample code is taken from an open-source
   CRC generator [WILLIAMS93], using the "mirroring" technique and
   yielding a lookup table for SCTP CRC32c with 256 entries, each 32
   bits wide.

   This text has been modified by multiple errata.  It includes
   modifications from Section 3.5.  It is further updated in
   Section 3.46.

3.10.3.  Solution Description

   Text moved to the appropriate location.

3.11.  partial_bytes_acked after T3-rtx Expiration

3.11.1.  Description of the Problem

   Section 7.2.3 of [RFC4960] explicitly states that partial_bytes_acked
   should be reset to 0 after packet loss detection from SACK but the
   same is missed for T3-rtx timer expiration.

3.11.2.  Text Changes to the Document

   ---------
   Old text: (Section 7.2.3)
   ---------

   When the T3-rtx timer expires on an address, SCTP should perform slow
   start by:

   ssthresh = max(cwnd/2, 4*MTU)
   cwnd = 1*MTU

   ---------
   New text: (Section 7.2.3)
   ---------

   When the T3-rtx timer expires on an address, SCTP SHOULD perform slow
   start by:

   ssthresh = max(cwnd/2, 4*MTU)
   cwnd = 1*MTU
   partial_bytes_acked = 0



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   This text is in final form, and is not further updated in this
   document.

3.11.3.  Solution Description

   Specify that partial_bytes_acked should be reset to 0 after T3-rtx
   timer expiration.

3.12.  Order of Adjustments of partial_bytes_acked and cwnd

3.12.1.  Description of the Problem

   Section 7.2.2 of [RFC4960] likely implies the wrong order of
   adjustments applied to partial_bytes_acked and cwnd in the congestion
   avoidance phase.

3.12.2.  Text Changes to the Document

   ---------
   Old text: (Section 7.2.2)
   ---------

   o  When partial_bytes_acked is equal to or greater than cwnd and
      before the arrival of the SACK the sender had cwnd or more bytes
      of data outstanding (i.e., before arrival of the SACK, flightsize
      was greater than or equal to cwnd), increase cwnd by MTU, and
      reset partial_bytes_acked to (partial_bytes_acked - cwnd).

   ---------
   New text: (Section 7.2.2)
   ---------

   o  When partial_bytes_acked is equal to or greater than cwnd and
      before the arrival of the SACK the sender had cwnd or more bytes
      of data outstanding (i.e., before arrival of the SACK, flightsize
      was greater than or equal to cwnd), partial_bytes_acked is reset
      to (partial_bytes_acked - cwnd). Next, cwnd is increased by 1*MTU.

   This text has been modified by multiple errata.  It is further
   updated in Section 3.26.

3.12.3.  Solution Description

   The new text defines the exact order of adjustments of
   partial_bytes_acked and cwnd in the congestion avoidance phase.






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3.13.  HEARTBEAT ACK and the association error counter

3.13.1.  Description of the Problem

   Section 8.1 and Section 8.3 of [RFC4960] prescribe that the receiver
   of a HEARTBEAT ACK must reset the association overall error counter.
   In some circumstances, e.g.  when a router discards DATA chunks but
   not HEARTBEAT chunks due to the larger size of the DATA chunk, it
   might be better to not clear the association error counter on
   reception of the HEARTBEAT ACK and reset it only on reception of the
   SACK to avoid stalling the association.

3.13.2.  Text Changes to the Document

   ---------
   Old text: (Section 8.1)
   ---------

   The counter shall be reset each time a DATA chunk sent to that peer
   endpoint is acknowledged (by the reception of a SACK) or a HEARTBEAT
   ACK is received from the peer endpoint.

   ---------
   New text: (Section 8.1)
   ---------

   The counter MUST be reset each time a DATA chunk sent to that peer
   endpoint is acknowledged (by the reception of a SACK). When a
   HEARTBEAT ACK is received from the peer endpoint, the counter SHOULD
   also be reset. The receiver of the HEARTBEAT ACK MAY choose not to
   clear the counter if there is outstanding data on the association.
   This allows for handling the possible difference in reachability
   based on DATA chunks and HEARTBEAT chunks.

   This text is in final form, and is not further updated in this
   document.















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   ---------
   Old text: (Section 8.3)
   ---------

   Upon the receipt of the HEARTBEAT ACK, the sender of the HEARTBEAT
   should clear the error counter of the destination transport address
   to which the HEARTBEAT was sent, and mark the destination transport
   address as active if it is not so marked.  The endpoint may
   optionally report to the upper layer when an inactive destination
   address is marked as active due to the reception of the latest
   HEARTBEAT ACK.  The receiver of the HEARTBEAT ACK must also clear the
   association overall error count as well (as defined in Section 8.1).

   ---------
   New text: (Section 8.3)
   ---------

   Upon the receipt of the HEARTBEAT ACK, the sender of the HEARTBEAT
   MUST clear the error counter of the destination transport address
   to which the HEARTBEAT was sent, and mark the destination transport
   address as active if it is not so marked. The endpoint MAY
   optionally report to the upper layer when an inactive destination
   address is marked as active due to the reception of the latest
   HEARTBEAT ACK. The receiver of the HEARTBEAT ACK SHOULD also clear
   the association overall error counter (as defined in Section 8.1).

   This text has been modified by multiple errata.  It is further
   updated in Section 3.23.

3.13.3.  Solution Description

   The new text provides a possibility to not reset the association
   overall error counter when a HEARTBEAT ACK is received if there are
   valid reasons for it.

3.14.  Path for Fast Retransmission

3.14.1.  Description of the Problem

   [RFC4960] clearly describes where to retransmit data that is timed
   out when the peer is multi-homed but the same is not stated for fast
   retransmissions.

3.14.2.  Text Changes to the Document







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 ---------
 Old text: (Section 6.4)
 ---------

 Furthermore, when its peer is multi-homed, an endpoint SHOULD try to
 retransmit a chunk that timed out to an active destination transport
 address that is different from the last destination address to which
 the DATA chunk was sent.

 ---------
 New text: (Section 6.4)
 ---------

 Furthermore, when its peer is multi-homed, an endpoint SHOULD try to
 retransmit a chunk that timed out to an active destination transport
 address that is different from the last destination address to which
 the DATA chunk was sent.

 When its peer is multi-homed, an endpoint SHOULD send fast
 retransmissions to the same destination transport address where the
 original data was sent to. If the primary path has been changed and the
 original data was sent to the old primary path before the fast
 retransmit, the implementation MAY send it to the new primary path.

   This text is in final form, and is not further updated in this
   document.

3.14.3.  Solution Description

   The new text clarifies where to send fast retransmissions.

3.15.  Transmittal in Fast Recovery

3.15.1.  Description of the Problem

   The Fast Retransmit on Gap Reports algorithm intends that only the
   very first packet may be sent regardless of cwnd in the Fast Recovery
   phase but rule 3) of [RFC4960], Section 7.2.4, misses this
   clarification.

3.15.2.  Text Changes to the Document










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   ---------
   Old text: (Section 7.2.4)
   ---------

   3)  Determine how many of the earliest (i.e., lowest TSN) DATA chunks
       marked for retransmission will fit into a single packet, subject
       to constraint of the path MTU of the destination transport
       address to which the packet is being sent.  Call this value K.
       Retransmit those K DATA chunks in a single packet.  When a Fast
       Retransmit is being performed, the sender SHOULD ignore the value
       of cwnd and SHOULD NOT delay retransmission for this single
       packet.

   ---------
   New text: (Section 7.2.4)
   ---------

   3)  If not in Fast Recovery, determine how many of the earliest
       (i.e., lowest TSN) DATA chunks marked for retransmission will fit
       into a single packet, subject to constraint of the PMTU of
       the destination transport address to which the packet is being
       sent. Call this value K. Retransmit those K DATA chunks in a
       single packet. When a Fast Retransmit is being performed, the
       sender SHOULD ignore the value of cwnd and SHOULD NOT delay
       retransmission for this single packet.

   This text is in final form, and is not further updated in this
   document.

3.15.3.  Solution Description

   The new text explicitly specifies to send only the first packet in
   the Fast Recovery phase disregarding cwnd limitations.

3.16.  Initial Value of ssthresh

3.16.1.  Description of the Problem

   The initial value of ssthresh should be set arbitrarily high.  Using
   the advertised receiver window of the peer is inappropriate if the
   peer increases its window after the handshake.  Furthermore, use a
   higher requirements level, since not following the advice may result
   in performance problems.








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3.16.2.  Text Changes to the Document

   ---------
   Old text: (Section 7.2.1)
   ---------

   o  The initial value of ssthresh MAY be arbitrarily high (for
      example, implementations MAY use the size of the receiver
      advertised window).

   ---------
   New text: (Section 7.2.1)
   ---------

   o  The initial value of ssthresh SHOULD be arbitrarily high (e.g.,
      the size of the largest possible advertised window).

   This text is in final form, and is not further updated in this
   document.

3.16.3.  Solution Description

   Use the same value as suggested in [RFC5681], Section 3.1, as an
   appropriate initial value.  Furthermore, use the same requirements
   level.

3.17.  Automatically Confirmed Addresses

3.17.1.  Description of the Problem

   The Path Verification procedure of [RFC4960] prescribes that any
   address passed to the sender of the INIT by its upper layer is
   automatically CONFIRMED.  This, however, is unclear if only addresses
   in the request to initiate association establishment are considered
   or any addresses provided by the upper layer in any requests (e.g. in
   'Set Primary').

3.17.2.  Text Changes to the Document













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   ---------
   Old text: (Section 5.4)
   ---------

   1)  Any address passed to the sender of the INIT by its upper layer
      is automatically considered to be CONFIRMED.

   ---------
   New text: (Section 5.4)
   ---------

   1)  Any addresses passed to the sender of the INIT by its upper
      layer in the request to initialize an association are
      automatically considered to be CONFIRMED.

   This text is in final form, and is not further updated in this
   document.

3.17.3.  Solution Description

   The new text clarifies that only addresses provided by the upper
   layer in the request to initialize an association are automatically
   confirmed.

3.18.  Only One Packet after Retransmission Timeout

3.18.1.  Description of the Problem

   [RFC4960] is not completely clear when it describes data transmission
   after T3-rtx timer expiration.  Section 7.2.1 does not specify how
   many packets are allowed to be sent after T3-rtx timer expiration if
   more than one packet fit into cwnd.  At the same time, Section 7.2.3
   has the text without normative language saying that SCTP should
   ensure that no more than one packet will be in flight after T3-rtx
   timer expiration until successful acknowledgment.  It makes the text
   inconsistent.

3.18.2.  Text Changes to the Document













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   ---------
   Old text: (Section 7.2.1)
   ---------

   o  The initial cwnd after a retransmission timeout MUST be no more
      than 1*MTU.

   ---------
   New text: (Section 7.2.1)
   ---------

   o  The initial cwnd after a retransmission timeout MUST be no more
      than 1*MTU and only one packet is allowed to be in flight
      until successful acknowledgement.

   This text is in final form, and is not further updated in this
   document.

3.18.3.  Solution Description

   The new text clearly specifies that only one packet is allowed to be
   sent after T3-rtx timer expiration until successful acknowledgement.

3.19.  INIT ACK Path for INIT in COOKIE-WAIT State

3.19.1.  Description of the Problem

   In case of an INIT received in the COOKIE-WAIT state [RFC4960]
   prescribes to send an INIT ACK to the same destination address to
   which the original INIT has been sent.  This text does not address
   the possibility of the upper layer to provide multiple remote IP
   addresses while requesting the association establishment.  If the
   upper layer has provided multiple IP addresses and only a subset of
   these addresses are supported by the peer then the destination
   address of the original INIT may be absent in the incoming INIT and
   sending INIT ACK to that address is useless.

3.19.2.  Text Changes to the Document













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   ---------
   Old text: (Section 5.2.1)
   ---------

   Upon receipt of an INIT in the COOKIE-WAIT state, an endpoint MUST
   respond with an INIT ACK using the same parameters it sent in its
   original INIT chunk (including its Initiate Tag, unchanged).  When
   responding, the endpoint MUST send the INIT ACK back to the same
   address that the original INIT (sent by this endpoint) was sent.

   ---------
   New text: (Section 5.2.1)
   ---------

   Upon receipt of an INIT in the COOKIE-WAIT state, an endpoint MUST
   respond with an INIT ACK using the same parameters it sent in its
   original INIT chunk (including its Initiate Tag, unchanged). When
   responding, the following rules MUST be applied:

   1)  The INIT ACK MUST only be sent to an address passed by the upper
       layer in the request to initialize the association.

   2)  The INIT ACK MUST only be sent to an address reported in the
       incoming INIT.

   3)  The INIT ACK SHOULD be sent to the source address of the
       received INIT.

   This text is in final form, and is not further updated in this
   document.

3.19.3.  Solution Description

   The new text requires sending INIT ACK to a destination address that
   is passed by the upper layer and reported in the incoming INIT.  If
   the source address of the INIT meets these conditions, sending the
   INIT ACK to the source address of the INIT is the preferred behavior.

3.20.  Zero Window Probing and Unreachable Primary Path

3.20.1.  Description of the Problem

   Section 6.1 of [RFC4960] states that when sending zero window probes,
   SCTP should neither increment the association counter nor increment
   the destination address error counter if it continues to receive new
   packets from the peer.  However, the reception of new packets from
   the peer does not guarantee the peer's reachability and, if the
   destination address becomes unreachable during zero window probing,



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   SCTP cannot get an updated rwnd until it switches the destination
   address for probes.

3.20.2.  Text Changes to the Document

   ---------
   Old text: (Section 6.1)
   ---------

   If the sender continues to receive new packets from the receiver
   while doing zero window probing, the unacknowledged window probes
   should not increment the error counter for the association or any
   destination transport address.  This is because the receiver MAY
   keep its window closed for an indefinite time.  Refer to Section
   6.2 on the receiver behavior when it advertises a zero window.

   ---------
   New text: (Section 6.1)
   ---------

   If the sender continues to receive SACKs from the peer
   while doing zero window probing, the unacknowledged window probes
   SHOULD NOT increment the error counter for the association or any
   destination transport address.  This is because the receiver could
   keep its window closed for an indefinite time.  Section 6.2 describes
   the receiver behavior when it advertises a zero window.

   This text is in final form, and is not further updated in this
   document.

3.20.3.  Solution Description

   The new text clarifies that if the receiver continues to send SACKs,
   the sender of probes should not increment the error counter of the
   association and the destination address even if the SACKs do not
   acknowledge the probes.

3.21.  Normative Language in Section 10

3.21.1.  Description of the Problem

   Section 10 of [RFC4960] is informative and, therefore, normative
   language such as MUST and MAY cannot be used there.  However, there
   are several places in Section 10 where MUST and MAY are used.







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3.21.2.  Text Changes to the Document

   ---------
   Old text: (Section 10.1 E))
   ---------

   o  no-bundle flag - instructs SCTP not to bundle this user data with
      other outbound DATA chunks.  SCTP MAY still bundle even when this
      flag is present, when faced with network congestion.

   ---------
   New text: (Section 10.1 E))
   ---------

   o  no-bundle flag - instructs SCTP not to bundle this user data with
      other outbound DATA chunks.  SCTP may still bundle even when this
      flag is present, when faced with network congestion.

   This text is in final form, and is not further updated in this
   document.

  ---------
  Old text: (Section 10.1 G))
  ---------

  o  Stream Sequence Number - the Stream Sequence Number assigned by
     the sending SCTP peer.

  o  partial flag - if this returned flag is set to 1, then this
     Receive contains a partial delivery of the whole message.  When
     this flag is set, the stream id and Stream Sequence Number MUST
     accompany this receive.  When this flag is set to 0, it indicates
     that no more deliveries will be received for this Stream Sequence
     Number.

  ---------
  New text: (Section 10.1 G))
  ---------

  o  stream sequence number - the Stream Sequence Number assigned by
     the sending SCTP peer.

  o  partial flag - if this returned flag is set to 1, then this
     primitive contains a partial delivery of the whole message.  When
     this flag is set, the stream id and stream sequence number must
     accompany this primitive.  When this flag is set to 0, it indicates
     that no more deliveries will be received for this stream sequence
     number.



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   This text is in final form, and is not further updated in this
   document.

  ---------
  Old text: (Section 10.1 N))
  ---------

  o  Stream Sequence Number - this value is returned indicating the
     Stream Sequence Number that was associated with the message.

  o  partial flag - if this returned flag is set to 1, then this
     message is a partial delivery of the whole message.  When this
     flag is set, the stream id and Stream Sequence Number MUST
     accompany this receive.  When this flag is set to 0, it indicates
     that no more deliveries will be received for this Stream Sequence
     Number.

  ---------
  New text: (Section 10.1 N))
  ---------

  o  stream sequence number - this value is returned indicating the
     Stream Sequence Number that was associated with the message.

  o  partial flag - if this returned flag is set to 1, then this
     message is a partial delivery of the whole message.  When this
     flag is set, the stream id and stream sequence number must
     accompany this primitive.  When this flag is set to 0, it indicates
     that no more deliveries will be received for this stream sequence
     number.

   This text is in final form, and is not further updated in this
   document.


















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  ---------
  Old text: (Section 10.1 O))
  ---------

  o  Stream Sequence Number - this value is returned indicating the
     Stream Sequence Number that was associated with the message.

  o  partial flag - if this returned flag is set to 1, then this
     message is a partial delivery of the whole message.  When this
     flag is set, the stream id and Stream Sequence Number MUST
     accompany this receive.  When this flag is set to 0, it indicates
     that no more deliveries will be received for this Stream Sequence
     Number.

  ---------
  New text: (Section 10.1 O))
  ---------

  o  stream sequence number - this value is returned indicating the
     Stream Sequence Number that was associated with the message.

  o  partial flag - if this returned flag is set to 1, then this
     message is a partial delivery of the whole message.  When this
     flag is set, the stream id and stream sequence number must
     accompany this primitive.  When this flag is set to 0, it indicates
     that no more deliveries will be received for this stream sequence
     number.

   This text is in final form, and is not further updated in this
   document.

3.21.3.  Solution Description

   The normative language is removed from Section 10.  In addition, the
   consistency of the text has been improved.

3.22.  Increase of partial_bytes_acked in Congestion Avoidance

3.22.1.  Description of the Problem

   Two issues have been discovered with the partial_bytes_acked handling
   described in Section 7.2.2 of [RFC4960]:

   o  If the Cumulative TSN Ack Point is not advanced but the SACK chunk
      acknowledges new TSNs in the Gap Ack Blocks, these newly
      acknowledged TSNs are not considered for partial_bytes_acked
      although these TSNs were successfully received by the peer.




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   o  Duplicate TSNs are not considered in partial_bytes_acked although
      they confirm that the DATA chunks were successfully received by
      the peer.

3.22.2.  Text Changes to the Document

   ---------
   Old text: (Section 7.2.2)
   ---------

   o  Whenever cwnd is greater than ssthresh, upon each SACK arrival
      that advances the Cumulative TSN Ack Point, increase
      partial_bytes_acked by the total number of bytes of all new chunks
      acknowledged in that SACK including chunks acknowledged by the new
      Cumulative TSN Ack and by Gap Ack Blocks.

   ---------
   New text: (Section 7.2.2)
   ---------

   o  Whenever cwnd is greater than ssthresh, upon each SACK arrival,
      increase partial_bytes_acked by the total number of bytes of all
      new chunks acknowledged in that SACK including chunks acknowledged
      by the new Cumulative TSN Ack, by Gap Ack Blocks and by the number
      of bytes of duplicated chunks reported in Duplicate TSNs.

   This text has been modified by multiple errata.  It is further
   updated in Section 3.26.

3.22.3.  Solution Description

   Now partial_bytes_acked is increased by TSNs reported as duplicated
   as well as TSNs newly acknowledged in Gap Ack Blocks even if the
   Cumulative TSN Ack Point is not advanced.

3.23.  Inconsistency in Notifications Handling

3.23.1.  Description of the Problem

   [RFC4960] uses inconsistent normative and non-normative language when
   describing rules for sending notifications to the upper layer.  E.g.
   Section 8.2 of [RFC4960] says that when a destination address becomes
   inactive due to an unacknowledged DATA chunk or HEARTBEAT chunk, SCTP
   SHOULD send a notification to the upper layer while Section 8.3 of
   [RFC4960] says that when a destination address becomes inactive due
   to an unacknowledged HEARTBEAT chunk, SCTP may send a notification to
   the upper layer.




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   This makes the text inconsistent.

3.23.2.  Text Changes to the Document

   ---------
   Old text: (Section 8.1)
   ---------

   An endpoint shall keep a counter on the total number of consecutive
   retransmissions to its peer (this includes retransmissions to all the
   destination transport addresses of the peer if it is multi-homed),
   including unacknowledged HEARTBEAT chunks.

   ---------
   New text: (Section 8.1)
   ---------

   An endpoint SHOULD keep a counter on the total number of consecutive
   retransmissions to its peer (this includes data retransmissions
   to all the destination transport addresses of the peer if it is
   multi-homed), including the number of unacknowledged HEARTBEAT
   chunks observed on the path which currently is used for data
   transfer. Unacknowledged HEARTBEAT chunks observed on paths
   different from the path currently used for data transfer SHOULD
   NOT increment the association error counter, as this could lead
   to association closure even if the path which currently is used for
   data transfer is available (but idle). If the value of this
   counter exceeds the limit indicated in the protocol parameter
   'Association.Max.Retrans', the endpoint SHOULD consider the peer
   endpoint unreachable and SHALL stop transmitting any more data to it
   (and thus the association enters the CLOSED state).  In addition, the
   endpoint SHOULD report the failure to the upper layer and optionally
   report back all outstanding user data remaining in its outbound
   queue.  The association is automatically closed when the peer
   endpoint becomes unreachable.

   This text has been modified by multiple errata.  It includes
   modifications from Section 3.6.  It is in final form, and is not
   further updated in this document.












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   ---------
   Old text: (Section 8.2)
   ---------

   When an outstanding TSN is acknowledged or a HEARTBEAT sent to that
   address is acknowledged with a HEARTBEAT ACK, the endpoint shall
   clear the error counter of the destination transport address to which
   the DATA chunk was last sent (or HEARTBEAT was sent).  When the peer
   endpoint is multi-homed and the last chunk sent to it was a
   retransmission to an alternate address, there exists an ambiguity as
   to whether or not the acknowledgement should be credited to the
   address of the last chunk sent.  However, this ambiguity does not
   seem to bear any significant consequence to SCTP behavior.  If this
   ambiguity is undesirable, the transmitter may choose not to clear the
   error counter if the last chunk sent was a retransmission.

   ---------
   New text: (Section 8.2)
   ---------

   When an outstanding TSN is acknowledged or a HEARTBEAT sent to that
   address is acknowledged with a HEARTBEAT ACK, the endpoint SHOULD
   clear the error counter of the destination transport address to which
   the DATA chunk was last sent (or HEARTBEAT was sent), and SHOULD
   also report to the upper layer when an inactive destination address
   is marked as active. When the peer endpoint is multi-homed and the
   last chunk sent to it was a retransmission to an alternate address,
   there exists an ambiguity as to whether or not the acknowledgement
   could be credited to the address of the last chunk sent. However,
   this ambiguity does not seem to bear any significant consequence to
   SCTP behavior. If this ambiguity is undesirable, the transmitter MAY
   choose not to clear the error counter if the last chunk sent was a
   retransmission.

   This text is in final form, and is not further updated in this
   document.















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   ---------
   Old text: (Section 8.3)
   ---------

   When the value of this counter reaches the protocol parameter
   'Path.Max.Retrans', the endpoint should mark the corresponding
   destination address as inactive if it is not so marked, and may also
   optionally report to the upper layer the change of reachability of
   this destination address.  After this, the endpoint should continue
   HEARTBEAT on this destination address but should stop increasing the
   counter.

   ---------
   New text: (Section 8.3)
   ---------

   When the value of this counter exceeds the protocol parameter
   'Path.Max.Retrans', the endpoint SHOULD mark the corresponding
   destination address as inactive if it is not so marked, and SHOULD
   also report to the upper layer the change of reachability of this
   destination address.  After this, the endpoint SHOULD continue
   HEARTBEAT on this destination address but SHOULD stop increasing the
   counter.

   This text has been modified by multiple errata.  It includes
   modifications from Section 3.1.  It is in final form, and is not
   further updated in this document.
























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   ---------
   Old text: (Section 8.3)
   ---------

   Upon the receipt of the HEARTBEAT ACK, the sender of the HEARTBEAT
   should clear the error counter of the destination transport address
   to which the HEARTBEAT was sent, and mark the destination transport
   address as active if it is not so marked.  The endpoint may
   optionally report to the upper layer when an inactive destination
   address is marked as active due to the reception of the latest
   HEARTBEAT ACK.  The receiver of the HEARTBEAT ACK must also clear the
   association overall error count as well (as defined in Section 8.1).

   ---------
   New text: (Section 8.3)
   ---------

   Upon the receipt of the HEARTBEAT ACK, the sender of the HEARTBEAT
   SHOULD clear the error counter of the destination transport address
   to which the HEARTBEAT was sent, and mark the destination transport
   address as active if it is not so marked. The endpoint SHOULD
   report to the upper layer when an inactive destination address
   is marked as active due to the reception of the latest
   HEARTBEAT ACK. The receiver of the HEARTBEAT ACK SHOULD also clear
   the association overall error counter (as defined in Section 8.1).

   This text has been modified by multiple errata.  It includes
   modifications from Section 3.13.  It is in final form, and is not
   further updated in this document.






















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   ---------
   Old text: (Section 9.2)
   ---------

   An endpoint should limit the number of retransmissions of the
   SHUTDOWN chunk to the protocol parameter 'Association.Max.Retrans'.
   If this threshold is exceeded, the endpoint should destroy the TCB
   and MUST report the peer endpoint unreachable to the upper layer (and
   thus the association enters the CLOSED state).

   ---------
   New text: (Section 9.2)
   ---------

   An endpoint SHOULD limit the number of retransmissions of the
   SHUTDOWN chunk to the protocol parameter 'Association.Max.Retrans'.
   If this threshold is exceeded, the endpoint SHOULD destroy the TCB
   and SHOULD report the peer endpoint unreachable to the upper layer
   (and thus the association enters the CLOSED state).

   This text is in final form, and is not further updated in this
   document.

   ---------
   Old text: (Section 9.2)
   ---------

   The sender of the SHUTDOWN ACK should limit the number of
   retransmissions of the SHUTDOWN ACK chunk to the protocol parameter
   'Association.Max.Retrans'.  If this threshold is exceeded, the
   endpoint should destroy the TCB and may report the peer endpoint
   unreachable to the upper layer (and thus the association enters the
   CLOSED state).

   ---------
   New text: (Section 9.2)
   ---------

   The sender of the SHUTDOWN ACK SHOULD limit the number of
   retransmissions of the SHUTDOWN ACK chunk to the protocol parameter
   'Association.Max.Retrans'. If this threshold is exceeded, the
   endpoint SHOULD destroy the TCB and SHOULD report the peer endpoint
   unreachable to the upper layer (and thus the association enters the
   CLOSED state).

   This text is in final form, and is not further updated in this
   document.




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3.23.3.  Solution Description

   The inconsistencies are removed by using consistently SHOULD.

3.24.  SACK.Delay Not Listed as a Protocol Parameter

3.24.1.  Description of the Problem

   SCTP as specified in [RFC4960] supports delaying SACKs.  The timer
   value for this is a parameter and Section 6.2 of [RFC4960] specifies
   a default and maximum value for it.  However, defining a name for
   this parameter and listing it in the table of protocol parameters in
   Section 15 of [RFC4960] is missing.

   This issue was reported as an Errata for [RFC4960] with Errata ID
   4656.

3.24.2.  Text Changes to the Document

   ---------
   Old text: (Section 6.2)
   ---------

   An implementation MUST NOT allow the maximum delay to be configured
   to be more than 500 ms.  In other words, an implementation MAY lower
   this value below 500 ms but MUST NOT raise it above 500 ms.

   ---------
   New text: (Section 6.2)
   ---------

   An implementation MUST NOT allow the maximum delay (protocol
   parameter 'SACK.Delay') to be configured to be more than 500 ms.
   In other words, an implementation MAY lower the value of
   SACK.Delay below 500 ms but MUST NOT raise it above 500 ms.

   This text is in final form, and is not further updated in this
   document.













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   ---------
   Old text: (Section 15)
   ---------

   The following protocol parameters are RECOMMENDED:

      RTO.Initial - 3 seconds
      RTO.Min - 1 second
      RTO.Max - 60 seconds
      Max.Burst - 4
      RTO.Alpha - 1/8
      RTO.Beta - 1/4
      Valid.Cookie.Life - 60 seconds
      Association.Max.Retrans - 10 attempts
      Path.Max.Retrans - 5 attempts (per destination address)
      Max.Init.Retransmits - 8 attempts
      HB.interval - 30 seconds
      HB.Max.Burst - 1

   ---------
   New text: (Section 15)
   ---------

   The following protocol parameters are RECOMMENDED:

      RTO.Initial - 3 seconds
      RTO.Min - 1 second
      RTO.Max - 60 seconds
      Max.Burst - 4
      RTO.Alpha - 1/8
      RTO.Beta - 1/4
      Valid.Cookie.Life - 60 seconds
      Association.Max.Retrans - 10 attempts
      Path.Max.Retrans - 5 attempts (per destination address)
      Max.Init.Retransmits - 8 attempts
      HB.interval - 30 seconds
      HB.Max.Burst - 1
      SACK.Delay - 200 milliseconds

   This text has been modified by multiple errata.  It is further
   updated in Section 3.32.

3.24.3.  Solution Description

   The parameter was given a name and added to the list of protocol
   parameters.





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3.25.  Processing of Chunks in an Incoming SCTP Packet

3.25.1.  Description of the Problem

   There are a few places in [RFC4960] where the receiver of a packet
   must discard it while processing the chunks of the packet.  It is
   unclear whether the receiver has to rollback state changes already
   performed while processing the packet or not.

   The intention of [RFC4960] is to process an incoming packet chunk by
   chunk and not to perform any prescreening of chunks in the received
   packet.  Thus, by discarding one chunk the receiver also causes
   discarding of all further chunks.

3.25.2.  Text Changes to the Document

   ---------
   Old text: (Section 3.2)
   ---------

   00 -  Stop processing this SCTP packet and discard it, do not
         process any further chunks within it.

   01 -  Stop processing this SCTP packet and discard it, do not
         process any further chunks within it, and report the
         unrecognized chunk in an 'Unrecognized Chunk Type'.

   ---------
   New text: (Section 3.2)
   ---------

   00 -  Stop processing this SCTP packet, discard the unrecognized
         chunk and all further chunks.

   01 -  Stop processing this SCTP packet, discard the unrecognized
         chunk and all further chunks, and report the unrecognized
         chunk in an 'Unrecognized Chunk Type'.

   This text is in final form, and is not further updated in this
   document.











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  ---------
  Old text: (Section 11.3)
  ---------

  It is helpful for some firewalls if they can inspect just the first
  fragment of a fragmented SCTP packet and unambiguously determine
  whether it corresponds to an INIT chunk (for further information,
  please refer to [RFC1858]).  Accordingly, we stress the requirements,
  stated in Section 3.1, that (1) an INIT chunk MUST NOT be bundled
  with any other chunk in a packet, and (2) a packet containing an INIT
  chunk MUST have a zero Verification Tag.  Furthermore, we require
  that the receiver of an INIT chunk MUST enforce these rules by
  silently discarding an arriving packet with an INIT chunk that is
  bundled with other chunks or has a non-zero verification tag and
  contains an INIT-chunk.

  ---------
  New text: (Section 11.3)
  ---------

  It is helpful for some firewalls if they can inspect just the first
  fragment of a fragmented SCTP packet and unambiguously determine
  whether it corresponds to an INIT chunk (for further information,
  please refer to [RFC1858]).  Accordingly, we stress the requirements,
  stated in Section 3.1, that (1) an INIT chunk MUST NOT be bundled
  with any other chunk in a packet, and (2) a packet containing an INIT
  chunk MUST have a zero Verification Tag.
  The receiver of an INIT chunk MUST silently discard the INIT chunk and
  all further chunks if the INIT chunk is bundled with other chunks or
  the packet has a non-zero verification tag.

   This text is in final form, and is not further updated in this
   document.

3.25.3.  Solution Description

   The new text makes it clear that chunks can be processed from the
   beginning to the end and no rollback or pre-screening is required.

3.26.  CWND Increase in Congestion Avoidance Phase

3.26.1.  Description of the Problem

   [RFC4960] in Section 7.2.2 prescribes to increase cwnd by 1*MTU per
   RTT if the sender has cwnd or more bytes of data outstanding to the
   corresponding address in the Congestion Avoidance phase.  However,
   this is described without normative language.  Moreover,
   Section 7.2.2 includes an algorithm how an implementation can achieve



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   this but this algorithm is underspecified and actually allows
   increasing cwnd by more than 1*MTU per RTT.

3.26.2.  Text Changes to the Document

   ---------
   Old text: (Section 7.2.2)
   ---------

   When cwnd is greater than ssthresh, cwnd should be incremented by
   1*MTU per RTT if the sender has cwnd or more bytes of data
   outstanding for the corresponding transport address.

   ---------
   New text: (Section 7.2.2)
   ---------

   When cwnd is greater than ssthresh, cwnd SHOULD be incremented by
   1*MTU per RTT if the sender has cwnd or more bytes of data
   outstanding for the corresponding transport address. The basic
   guidelines for incrementing cwnd during congestion avoidance are:

   o  SCTP MAY increment cwnd by 1*MTU.

   o  SCTP SHOULD increment cwnd by one 1*MTU once per RTT when
      the sender has cwnd or more bytes of data outstanding for
      the corresponding transport address.

   o  SCTP MUST NOT increment cwnd by more than 1*MTU per RTT.

   This text is in final form, and is not further updated in this
   document.



















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   ---------
   Old text: (Section 7.2.2)
   ---------

   o  Whenever cwnd is greater than ssthresh, upon each SACK arrival
      that advances the Cumulative TSN Ack Point, increase
      partial_bytes_acked by the total number of bytes of all new chunks
      acknowledged in that SACK including chunks acknowledged by the new
      Cumulative TSN Ack and by Gap Ack Blocks.

   o  When partial_bytes_acked is equal to or greater than cwnd and
      before the arrival of the SACK the sender had cwnd or more bytes
      of data outstanding (i.e., before arrival of the SACK, flightsize
      was greater than or equal to cwnd), increase cwnd by MTU, and
      reset partial_bytes_acked to (partial_bytes_acked - cwnd).

   ---------
   New text: (Section 7.2.2)
   ---------

   o  Whenever cwnd is greater than ssthresh, upon each SACK arrival,
      increase partial_bytes_acked by the total number of bytes of all
      new chunks acknowledged in that SACK including chunks acknowledged
      by the new Cumulative TSN Ack, by Gap Ack Blocks and by the number
      of bytes of duplicated chunks reported in Duplicate TSNs.

   o  When partial_bytes_acked is greater than cwnd and before the
      arrival of the SACK the sender had less than cwnd bytes of data
      outstanding (i.e., before arrival of the SACK, flightsize was less
      than cwnd), reset partial_bytes_acked to cwnd.

   o  When partial_bytes_acked is equal to or greater than cwnd and
      before the arrival of the SACK the sender had cwnd or more bytes
      of data outstanding (i.e., before arrival of the SACK, flightsize
      was greater than or equal to cwnd), partial_bytes_acked is reset
      to (partial_bytes_acked - cwnd). Next, cwnd is increased by 1*MTU.

   This text has been modified by multiple errata.  It includes
   modifications from Section 3.12 and Section 3.22.  It is in final
   form, and is not further updated in this document.

3.26.3.  Solution Description

   The basic guidelines for incrementing cwnd during the congestion
   avoidance phase are added into Section 7.2.2.  The guidelines include
   the normative language and are aligned with [RFC5681].





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   The algorithm from Section 7.2.2 is improved to not allow increasing
   cwnd by more than 1*MTU per RTT.

3.27.  Refresh of cwnd and ssthresh after Idle Period

3.27.1.  Description of the Problem

   [RFC4960] prescribes to adjust cwnd per RTO if the endpoint does not
   transmit data on a given transport address.  In addition to that, it
   prescribes to set cwnd to the initial value after a sufficiently long
   idle period.  The latter is excessive.  Moreover, it is unclear what
   is a sufficiently long idle period.

   [RFC4960] doesn't specify the handling of ssthresh in the idle case.
   If ssthresh is reduced due to a packet loss, ssthresh is never
   recovered.  So traffic can end up in Congestion Avoidance all the
   time, resulting in a low sending rate and bad performance.  The
   problem is even more serious for SCTP because in a multi-homed SCTP
   association traffic that switches back to the previously failed
   primary path will also lead to the situation where traffic ends up in
   Congestion Avoidance.

3.27.2.  Text Changes to the Document

   ---------
   Old text: (Section 7.2.1)
   ---------

   o  The initial cwnd before DATA transmission or after a sufficiently
      long idle period MUST be set to min(4*MTU, max (2*MTU, 4380
      bytes)).

   ---------
   New text: (Section 7.2.1)
   ---------

   o  The initial cwnd before DATA transmission MUST be set to
      min(4*MTU, max (2*MTU, 4380 bytes)).













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   ---------
   Old text: (Section 7.2.1)
   ---------

   o  When the endpoint does not transmit data on a given transport
      address, the cwnd of the transport address should be adjusted to
      max(cwnd/2, 4*MTU) per RTO.

   ---------
   New text: (Section 7.2.1)
   ---------
   o  While the endpoint does not transmit data on a given transport
      address, the cwnd of the transport address SHOULD be adjusted to
      max(cwnd/2, 4*MTU) once per RTO. Before the first cwnd adjustment,
      the ssthresh of the transport address SHOULD be set to the cwnd.

   This text is in final form, and is not further updated in this
   document.

3.27.3.  Solution Description

   A rule about cwnd adjustment after a sufficiently long idle period is
   removed.

   The text is updated to describe the ssthresh handling.  When the idle
   period is detected, the cwnd value is stored to the ssthresh value.

3.28.  Window Updates After Receiver Window Opens Up

3.28.1.  Description of the Problem

   The sending of SACK chunks for window updates is only indirectly
   referenced in [RFC4960], Section 6.2, where it is stated that an SCTP
   receiver must not generate more than one SACK for every incoming
   packet, other than to update the offered window.

   However, the sending of window updates when the receiver window opens
   up is necessary to avoid performance problems.

3.28.2.  Text Changes to the Document











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   ---------
   Old text: (Section 6.2)
   ---------

   An SCTP receiver MUST NOT generate more than one SACK for every
   incoming packet, other than to update the offered window as the
   receiving application consumes new data.

   ---------
   New text: (Section 6.2)
   ---------

   An SCTP receiver MUST NOT generate more than one SACK for every
   incoming packet, other than to update the offered window as the
   receiving application consumes new data. When the window opens
   up, an SCTP receiver SHOULD send additional SACK chunks to update
   the window even if no new data is received.
   The receiver MUST avoid sending a large number of window updates,
   in particular large bursts of them.
   One way to achieve this is to send a window update only if the
   window can be increased by at least a quarter of the receive
   buffer size of the association.

   This text is in final form, and is not further updated in this
   document.

3.28.3.  Solution Description

   The new text makes clear that additional SACK chunks for window
   updates should be sent as long as excessive bursts are avoided.

3.29.  Path of DATA and Reply Chunks

3.29.1.  Description of the Problem

   Section 6.4 of [RFC4960] describes the transmission policy for multi-
   homed SCTP endpoints.  However, there are the following issues with
   it:

   o  It states that a SACK should be sent to the source address of an
      incoming DATA.  However, it is known that other SACK policies
      (e.g. sending SACKs always to the primary path) may be more
      beneficial in some situations.
   o  Initially it states that an endpoint should always transmit DATA
      chunks to the primary path.  Then it states that the rule for
      transmittal of reply chunks should also be followed if the
      endpoint is bundling DATA chunks together with the reply chunk
      which contradicts with the first statement to always transmit DATA



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      chunks to the primary path.  Some implementations were having
      problems with it and sent DATA chunks bundled with reply chunks to
      a different destination address than the primary path that caused
      many gaps.

3.29.2.  Text Changes to the Document

---------
Old text: (Section 6.4)
---------

An endpoint SHOULD transmit reply chunks (e.g., SACK, HEARTBEAT ACK,
etc.) to the same destination transport address from which it
received the DATA or control chunk to which it is replying.  This
rule should also be followed if the endpoint is bundling DATA chunks
together with the reply chunk.

However, when acknowledging multiple DATA chunks received in packets
from different source addresses in a single SACK, the SACK chunk may
be transmitted to one of the destination transport addresses from
which the DATA or control chunks being acknowledged were received.

---------
New text: (Section 6.4)
---------

An endpoint SHOULD transmit reply chunks (e.g., INIT ACK, COOKIE ACK,
HEARTBEAT ACK, etc.) in response to control chunks to the same
destination transport address from which it received the control
chunk to which it is replying.

The selection of the destination transport address for packets
containing SACK chunks is implementation dependent. However, an endpoint
SHOULD NOT vary the destination transport address of a SACK when it
receives DATA chunks coming from the same source address.

When acknowledging multiple DATA chunks received in packets
from different source addresses in a single SACK, the SACK chunk MAY
be transmitted to one of the destination transport addresses from
which the DATA or control chunks being acknowledged were received.

   This text is in final form, and is not further updated in this
   document.








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3.29.3.  Solution Description

   The SACK transmission policy is left implementation dependent but it
   is specified to not vary the destination address of a packet
   containing a SACK chunk unless there are reasons for it as it may
   negatively impact RTT measurement.

   A confusing statement that prescribes to follow the rule for
   transmittal of reply chunks when the endpoint is bundling DATA chunks
   together with the reply chunk is removed.

3.30.  Outstanding Data, Flightsize and Data In Flight Key Terms

3.30.1.  Description of the Problem

   [RFC4960] uses outstanding data, flightsize and data in flight key
   terms in formulas and statements but their definitions are not
   provided in Section 1.3.  Furthermore, outstanding data does not
   include DATA chunks which are classified as lost but which have not
   been retransmitted yet and there is a paragraph in Section 6.1 of
   [RFC4960] where this statement is broken.

3.30.2.  Text Changes to the Document




























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   ---------
   Old text: (Section 1.3)
   ---------

   o  Congestion window (cwnd): An SCTP variable that limits the data,
      in number of bytes, a sender can send to a particular destination
      transport address before receiving an acknowledgement.

   ...

   o  Outstanding TSN (at an SCTP endpoint): A TSN (and the associated
      DATA chunk) that has been sent by the endpoint but for which it
      has not yet received an acknowledgement.

   ---------
   New text: (Section 1.3)
   ---------

   o  Outstanding TSN (at an SCTP endpoint): A TSN (and the associated
      DATA chunk) that has been sent by the endpoint but for which it
      has not yet received an acknowledgement.

   o  Outstanding data (or Data outstanding or Data in flight): The
      total amount of the DATA chunks associated with outstanding TSNs.
      A retransmitted DATA chunk is counted once in outstanding data.
      A DATA chunk which is classified as lost but which has not been
      retransmitted yet is not in outstanding data.

   o  Flightsize: The amount of bytes of outstanding data to a
      particular destination transport address at any given time.

   o  Congestion window (cwnd): An SCTP variable that limits outstanding
      data, in number of bytes, a sender can send to a particular
      destination transport address before receiving an acknowledgement.

   This text is in final form, and is not further updated in this
   document.














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   ---------
   Old text: (Section 6.1)
   ---------

   C) When the time comes for the sender to transmit, before sending new
      DATA chunks, the sender MUST first transmit any outstanding DATA
      chunks that are marked for retransmission (limited by the current
      cwnd).

   ---------
   New text: (Section 6.1)
   ---------

   C) When the time comes for the sender to transmit, before sending new
      DATA chunks, the sender MUST first transmit any DATA chunks that
      are marked for retransmission (limited by the current cwnd).

   This text is in final form, and is not further updated in this
   document.

3.30.3.  Solution Description

   Now Section 1.3, Key Terms, includes explanations of outstanding
   data, data in flight and flightsize key terms.  Section 6.1 is
   corrected to properly use the outstanding data term.

3.31.  CWND Degradation due to Max.Burst

3.31.1.  Description of the Problem

   Some implementations were experiencing a degradation of cwnd because
   of the Max.Burst limit.  This was due to misinterpretation of the
   suggestion in [RFC4960], Section 6.1, on how to use the Max.Burst
   parameter when calculating the number of packets to transmit.

3.31.2.  Text Changes to the Document















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   ---------
   Old text: (Section 6.1)
   ---------

   D) When the time comes for the sender to transmit new DATA chunks,
      the protocol parameter Max.Burst SHOULD be used to limit the
      number of packets sent.  The limit MAY be applied by adjusting
      cwnd as follows:

      if((flightsize + Max.Burst*MTU) < cwnd) cwnd = flightsize +
      Max.Burst*MTU

      Or it MAY be applied by strictly limiting the number of packets
      emitted by the output routine.

   ---------
   New text: (Section 6.1)
   ---------

   D) When the time comes for the sender to transmit new DATA chunks,
      the protocol parameter Max.Burst SHOULD be used to limit the
      number of packets sent.  The limit MAY be applied by adjusting
      cwnd temporarily as follows:

      if ((flightsize + Max.Burst*MTU) < cwnd)
          cwnd = flightsize + Max.Burst*MTU

      Or it MAY be applied by strictly limiting the number of packets
      emitted by the output routine. When calculating the number of
      packets to transmit and particularly using the formula above,
      cwnd SHOULD NOT be changed permanently.

   This text is in final form, and is not further updated in this
   document.

3.31.3.  Solution Description

   The new text clarifies that cwnd should not be changed when applying
   the Max.Burst limit.  This mitigates packet bursts related to the
   reception of SACK chunks, but not bursts related to an application
   sending a burst of user messages.

3.32.  Reduction of RTO.Initial








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3.32.1.  Description of the Problem

   [RFC4960] uses 3 seconds as the default value for RTO.Initial in
   accordance with Section 4.3.2.1 of [RFC1122].  [RFC6298] updates
   [RFC1122] and lowers the initial value of the retransmission timer
   from 3 seconds to 1 second.

3.32.2.  Text Changes to the Document

   ---------
   Old text: (Section 15)
   ---------

   The following protocol parameters are RECOMMENDED:

      RTO.Initial - 3 seconds
      RTO.Min - 1 second
      RTO.Max - 60 seconds
      Max.Burst - 4
      RTO.Alpha - 1/8
      RTO.Beta - 1/4
      Valid.Cookie.Life - 60 seconds
      Association.Max.Retrans - 10 attempts
      Path.Max.Retrans - 5 attempts (per destination address)
      Max.Init.Retransmits - 8 attempts
      HB.interval - 30 seconds
      HB.Max.Burst - 1

   ---------
   New text: (Section 15)
   ---------

   The following protocol parameters are RECOMMENDED:

      RTO.Initial - 1 second
      RTO.Min - 1 second
      RTO.Max - 60 seconds
      Max.Burst - 4
      RTO.Alpha - 1/8
      RTO.Beta - 1/4
      Valid.Cookie.Life - 60 seconds
      Association.Max.Retrans - 10 attempts
      Path.Max.Retrans - 5 attempts (per destination address)
      Max.Init.Retransmits - 8 attempts
      HB.interval - 30 seconds
      HB.Max.Burst - 1
      SACK.Delay - 200 milliseconds




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   This text has been modified by multiple errata.  It includes
   modifications from Section 3.24.  It is in final form, and is not
   further updated in this document.

3.32.3.  Solution Description

   The value RTO.Initial has been lowered to 1 second to be in tune with
   [RFC6298].

3.33.  Ordering of Bundled SACK and ERROR Chunks

3.33.1.  Description of the Problem

   When an SCTP endpoint receives a DATA chunk with an invalid stream
   identifier it shall acknowledge it by sending a SACK chunk and
   indicate that the stream identifier was invalid by sending an ERROR
   chunk.  These two chunks may be bundled.  However, [RFC4960] requires
   in case of bundling that the ERROR chunk follows the SACK chunk.
   This restriction of the ordering is not necessary and might only
   limit interoperability.

3.33.2.  Text Changes to the Document

 ---------
 Old text: (Section 6.5)
 ---------

 Every DATA chunk MUST carry a valid stream identifier.  If an
 endpoint receives a DATA chunk with an invalid stream identifier, it
 shall acknowledge the reception of the DATA chunk following the
 normal procedure, immediately send an ERROR chunk with cause set to
 "Invalid Stream Identifier" (see Section 3.3.10), and discard the
 DATA chunk.  The endpoint may bundle the ERROR chunk in the same
 packet as the SACK as long as the ERROR follows the SACK.

 ---------
 New text: (Section 6.5)
 ---------

 Every DATA chunk MUST carry a valid stream identifier.  If an
 endpoint receives a DATA chunk with an invalid stream identifier, it
 SHOULD acknowledge the reception of the DATA chunk following the
 normal procedure, immediately send an ERROR chunk with cause set to
 "Invalid Stream Identifier" (see Section 3.3.10), and discard the
 DATA chunk.  The endpoint MAY bundle the ERROR chunk and the SACK Chunk
 in the same packet.





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   This text is in final form, and is not further updated in this
   document.

3.33.3.  Solution Description

   The unnecessary restriction regarding the ordering of the SACK and
   ERROR chunk has been removed.

3.34.  Undefined Parameter Returned by RECEIVE Primitive

3.34.1.  Description of the Problem

   [RFC4960] provides a description of an abstract API.  In the
   definition of the RECEIVE primitive an optional parameter with name
   "delivery number" is mentioned.  However, no definition of this
   parameter is given in [RFC4960] and the parameter is unnecessary.

3.34.2.  Text Changes to the Document

   ---------
   Old text: (Section 10.1 G))
   ---------

   G) Receive

   Format: RECEIVE(association id, buffer address, buffer size
           [,stream id])
   -> byte count [,transport address] [,stream id] [,stream sequence
      number] [,partial flag] [,delivery number] [,payload protocol-id]

   ---------
   New text: (Section 10.1 G))
   ---------

   G) Receive

   Format: RECEIVE(association id, buffer address, buffer size
           [,stream id])
   -> byte count [,transport address] [,stream id] [,stream sequence
      number] [,partial flag] [,payload protocol-id]

   This text is in final form, and is not further updated in this
   document.








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3.34.3.  Solution Description

   The undefined parameter has been removed.

3.35.  DSCP Changes

3.35.1.  Description of the Problem

   The upper layer can change the Differentiated Services Code Point
   (DSCP) used for packets being sent.  A change of the DSCP can result
   in packets hitting different queues on the path and, therefore, the
   congestion control should be initialized when the DSCP is changed by
   the upper layer.  This is not described in [RFC4960].

3.35.2.  Text Changes to the Document

 ---------
 New text: (Section 7.2.5)
 ---------
 7.2.5.  Change of Differentiated Services Code Points

    SCTP implementations MAY allow an application to configure the
    Differentiated Services Code Point (DSCP) used for sending packets.
    If a DSCP change might result in outgoing packets being queued in
    different queues, the congestion control parameters for all affected
    destination addresses MUST be reset to their initial values.

   This text is in final form, and is not further updated in this
   document.






















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   ---------
   Old text: (Section 10.1 M))
   ---------

   Mandatory attributes:

   o  association id - local handle to the SCTP association.

   o  protocol parameter list - the specific names and values of the
      protocol parameters (e.g., Association.Max.Retrans; see Section
      15) that the SCTP user wishes to customize.

   ---------
   New text: (Section 10.1 M))
   ---------

   Mandatory attributes:

   o  association id - local handle to the SCTP association.

   o  protocol parameter list - the specific names and values of the
      protocol parameters (e.g., Association.Max.Retrans; see Section
      15, or other parameters like the DSCP) that the SCTP user wishes
      to customize.

   This text is in final form, and is not further updated in this
   document.

3.35.3.  Solution Description

   Text describing the required action on DSCP changes has been added.

3.36.  Inconsistent Handling of ICMPv4 and ICMPv6 Messages

3.36.1.  Description of the Problem

   Appendix C of [RFC4960] describes the handling of ICMPv4 and ICMPv6
   messages.  The handling of ICMP messages indicating that the port
   number is unreachable described in the enumeration is not consistent
   with the description given in [RFC4960] after the enumeration.
   Furthermore, the text explicitly describes the handling of ICMPv6
   packets indicating reachability problems, but does not do the same
   for the corresponding ICMPv4 packets.








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3.36.2.  Text Changes to the Document

   ---------
   Old text: (Appendix C)
   ---------

   ICMP3) An implementation MAY ignore any ICMPv4 messages where the
          code does not indicate "Protocol Unreachable" or
          "Fragmentation Needed".

   ---------
   New text: (Appendix C)
   ---------

   ICMP3) An implementation SHOULD ignore any ICMP messages where the
          code indicates "Port Unreachable".

   This text is in final form, and is not further updated in this
   document.

   ---------
   Old text: (Appendix C)
   ---------

   ICMP9) If the ICMPv6 code is "Destination Unreachable", the
          implementation MAY mark the destination into the unreachable
          state or alternatively increment the path error counter.

   ---------
   New text: (Appendix C)
   ---------

   ICMP9) If the ICMP type is "Destination Unreachable", the
          implementation MAY mark the destination into the unreachable
          state or alternatively increment the path error counter.

   This text has been modified by multiple errata.  It is further
   updated in Section 3.37.

3.36.3.  Solution Description

   The text has been changed to describe the intended handling of ICMP
   messages indicating that the port number is unreachable by replacing
   the third rule.  Furthermore, remove the limitation to ICMPv6 in the
   ninth rule.






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3.37.  Handling of Soft Errors

3.37.1.  Description of the Problem

   [RFC1122] defines the handling of soft errors and hard errors for
   TCP.  Appendix C of [RFC4960] only deals with hard errors.

3.37.2.  Text Changes to the Document

   ---------
   Old text: (Appendix C)
   ---------

   ICMP9) If the ICMPv6 code is "Destination Unreachable", the
          implementation MAY mark the destination into the unreachable
          state or alternatively increment the path error counter.

   ---------
   New text: (Appendix C)
   ---------

   ICMP9) If the ICMP type is "Destination Unreachable", the
          implementation MAY mark the destination into the unreachable
          state or alternatively increment the path error counter.
          SCTP MAY provide information to the upper layer indicating
          the reception of ICMP messages when reporting a network status
          change.

   This text has been modified by multiple errata.  It includes
   modifications from Section 3.36.  It is in final form, and is not
   further updated in this document.

3.37.3.  Solution Description

   Text has been added allowing SCTP to notify the application in case
   of soft errors.

3.38.  Honoring CWND

3.38.1.  Description of the Problem

   When using the slow start algorithm, SCTP increases the congestion
   window only when it is being fully utilized.  Since SCTP uses DATA
   chunks and does not use the congestion window to fragment user
   messages, this requires that some overbooking of the congestion
   window is allowed.





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3.38.2.  Text Changes to the Document

   ---------
   Old text: (Section 6.1)
   ---------

   B) At any given time, the sender MUST NOT transmit new data to a
      given transport address if it has cwnd or more bytes of data
      outstanding to that transport address.

   ---------
   New text: (Section 6.1)
   ---------

   B) At any given time, the sender MUST NOT transmit new data to a
      given transport address if it has cwnd + (PMTU - 1) or more bytes
      of data outstanding to that transport address.  If data is
      available the sender SHOULD exceed cwnd by up to (PMTU-1) bytes on
      a new data transmission if the flightsize does not currently reach
      cwnd. The breach of cwnd MUST constitute one packet only.

   This text is in final form, and is not further updated in this
   document.

   ---------
   Old text: (Section 7.2.1)
   ---------

   o  Whenever cwnd is greater than zero, the endpoint is allowed to
      have cwnd bytes of data outstanding on that transport address.

   ---------
   New text: (Section 7.2.1)
   ---------
   o  Whenever cwnd is greater than zero, the endpoint is allowed to
      have cwnd bytes of data outstanding on that transport address.
      A limited overbooking as described in B) of Section 6.1 SHOULD
      be supported.

   This text is in final form, and is not further updated in this
   document.

3.38.3.  Solution Description

   Text was added to clarify how the cwnd limit should be handled.






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3.39.  Zero Window Probing

3.39.1.  Description of the Problem

   The text describing zero window probing was not clearly handling the
   case where the window was not zero, but too small for the next DATA
   chunk to be transmitted.  Even in this case, zero window probing has
   to be performed to avoid deadlocks.

3.39.2.  Text Changes to the Document









































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   ---------
   Old text: (Section 6.1)
   ---------

   A) At any given time, the data sender MUST NOT transmit new data to
      any destination transport address if its peer's rwnd indicates
      that the peer has no buffer space (i.e., rwnd is 0; see Section
      6.2.1).  However, regardless of the value of rwnd (including if it
      is 0), the data sender can always have one DATA chunk in flight to
      the receiver if allowed by cwnd (see rule B, below).  This rule
      allows the sender to probe for a change in rwnd that the sender
      missed due to the SACK's having been lost in transit from the data
      receiver to the data sender.

      When the receiver's advertised window is zero, this probe is
      called a zero window probe.  Note that a zero window probe SHOULD
      only be sent when all outstanding DATA chunks have been
      cumulatively acknowledged and no DATA chunks are in flight.  Zero
      window probing MUST be supported.

   ---------
   New text: (Section 6.1)
   ---------

   A) At any given time, the data sender MUST NOT transmit new data to
      any destination transport address if its peer's rwnd indicates
      that the peer has no buffer space (i.e., rwnd is smaller than the
      size of the next DATA chunk; see Section 6.2.1).
      However, regardless of the value of rwnd (including if it is 0),
      the data sender can always have one DATA chunk in flight to
      the receiver if allowed by cwnd (see rule B, below).  This rule
      allows the sender to probe for a change in rwnd that the sender
      missed due to the SACK's having been lost in transit from the data
      receiver to the data sender.

      When the receiver has no buffer space, this probe is
      called a zero window probe.  Note that a zero window probe SHOULD
      only be sent when all outstanding DATA chunks have been
      cumulatively acknowledged and no DATA chunks are in flight.  Zero
      window probing MUST be supported.

   This text is in final form, and is not further updated in this
   document.








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3.39.3.  Solution Description

   The terminology is used in a cleaner way.

3.40.  Updating References Regarding ECN

3.40.1.  Description of the Problem

   [RFC4960] refers for ECN only to [RFC3168], which will be updated by
   [RFC8311].  This needs to be reflected when referring to ECN.

3.40.2.  Text Changes to the Document

   ---------
   Old text: (Appendix A)
   ---------

   ECN [RFC3168] describes a proposed extension to IP that details a
   method to become aware of congestion outside of datagram loss.

   ---------
   New text: (Appendix A)
   ---------

   ECN as specified in [RFC3168] updated by [RFC8311] describes an
   extension to IP that details a method to become aware of congestion
   outside of datagram loss.

   This text is in final form, and is not further updated in this
   document.

  ---------
  Old text: (Appendix A)
  ---------

  In general, [RFC3168] should be followed with the following
  exceptions.

  ---------
  New text: (Appendix A)
  ---------

  In general, [RFC3168] updated by [RFC8311] SHOULD be followed with the
  following exceptions.

   This text is in final form, and is not further updated in this
   document.




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   ---------
   Old text: (Appendix A)
   ---------

   [RFC3168] details negotiation of ECN during the SYN and SYN-ACK
   stages of a TCP connection.

   ---------
   New text: (Appendix A)
   ---------

   [RFC3168] updated by [RFC8311] details negotiation of ECN during the
   SYN and SYN-ACK stages of a TCP connection.

   This text is in final form, and is not further updated in this
   document.

   ---------
   Old text: (Appendix A)
   ---------

   [RFC3168] details a specific bit for a receiver to send back in its
   TCP acknowledgements to notify the sender of the Congestion
   Experienced (CE) bit having arrived from the network.

   ---------
   New text: (Appendix A)
   ---------

   [RFC3168] updated by [RFC8311] details a specific bit for a receiver
   to send back in its TCP acknowledgements to notify the sender of the
   Congestion Experienced (CE) bit having arrived from the network.

   This text is in final form, and is not further updated in this
   document.
















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   ---------
   Old text: (Appendix A)
   ---------

   [RFC3168] details a specific bit for a sender to send in the header
   of its next outbound TCP segment to indicate to its peer that it has
   reduced its congestion window.
   ---------
   New text: (Appendix A)
   ---------

   [RFC3168] updated by [RFC8311] details a specific bit for a sender
   to send in the header of its next outbound TCP segment to indicate to
   its peer that it has reduced its congestion window.

   This text is in final form, and is not further updated in this
   document.

3.40.3.  Solution Description

   References to [RFC8311] have been added.  While there, some
   wordsmithing has been performed.

3.41.  Host Name Address Parameter Deprecated

3.41.1.  Description of the Problem

   [RFC4960] defines three types of address parameters to be used with
   INIT and INIT ACK chunks:

   1.  IPv4 Address parameters.
   2.  IPv6 Address parameters.
   3.  Host Name Address parameters.

   The first two are supported by the SCTP kernel implementations of
   FreeBSD, Linux and Solaris, but the third one is not.  In addition,
   the first two where successfully tested in all nine interoperability
   tests for SCTP, but the third one has never been successfully tested.
   Therefore, the Host Name Address parameter should be deprecated.

3.41.2.  Text Changes to the Document










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   ---------
   Old text: (Section 3.3.2)
   ---------

   Note 3: An INIT chunk MUST NOT contain more than one Host Name
   Address parameter.  Moreover, the sender of the INIT MUST NOT combine
   any other address types with the Host Name Address in the INIT.  The
   receiver of INIT MUST ignore any other address types if the Host Name
   Address parameter is present in the received INIT chunk.

   ---------
   New text: (Section 3.3.2)
   ---------

   Note 3: An INIT chunk MUST NOT contain the Host Name Address
   parameter.  The receiver of an INIT chunk containing a Host Name
   Address parameter MUST send an ABORT and MAY include an Error Cause
   indicating an Unresolvable Address.

   This text is in final form, and is not further updated in this
   document.

   ---------
   Old text: (Section 3.3.2.1)
   ---------

   The sender of INIT uses this parameter to pass its Host Name (in
   place of its IP addresses) to its peer.  The peer is responsible for
   resolving the name.  Using this parameter might make it more likely
   for the association to work across a NAT box.

   ---------
   New text: (Section 3.3.2.1)
   ---------

   The sender of an INIT chunk MUST NOT include this parameter. The
   usage of the Host Name Address parameter is deprecated.

   This text is in final form, and is not further updated in this
   document.











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   ---------
   Old text: (Section 3.3.2.1)
   ---------

   Address Type: 16 bits (unsigned integer)

      This is filled with the type value of the corresponding address
      TLV (e.g., IPv4 = 5, IPv6 = 6, Host name = 11).

   ---------
   New text: (Section 3.3.2.1)
   ---------
   Address Type: 16 bits (unsigned integer)

      This is filled with the type value of the corresponding address
      TLV (e.g., IPv4 = 5, IPv6 = 6). The value indicating the Host
      Name Address parameter (Host name = 11) MUST NOT be used.

   This text is in final form, and is not further updated in this
   document.

   ---------
   Old text: (Section 3.3.3)
   ---------

   Note 3: The INIT ACK chunks MUST NOT contain more than one Host Name
   Address parameter.  Moreover, the sender of the INIT ACK MUST NOT
   combine any other address types with the Host Name Address in the
   INIT ACK.  The receiver of the INIT ACK MUST ignore any other address
   types if the Host Name Address parameter is present.

   ---------
   New text: (Section 3.3.3)
   ---------

   Note 3: An INIT ACK chunk MUST NOT contain the Host Name Address
   parameter.  The receiver of INIT ACK chunks containing a Host Name
   Address parameter MUST send an ABORT and MAY include an Error Cause
   indicating an Unresolvable Address.

   This text is in final form, and is not further updated in this
   document.

   ---------
   Old text: (Section 5.1.2)
   ---------

   B) If there is a Host Name parameter present in the received INIT or



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      INIT ACK chunk, the endpoint shall resolve that host name to a
      list of IP address(es) and derive the transport address(es) of
      this peer by combining the resolved IP address(es) with the SCTP
      source port.

      The endpoint MUST ignore any other IP Address parameters if they
      are also present in the received INIT or INIT ACK chunk.

      The time at which the receiver of an INIT resolves the host name
      has potential security implications to SCTP.  If the receiver of
      an INIT resolves the host name upon the reception of the chunk,
      and the mechanism the receiver uses to resolve the host name
      involves potential long delay (e.g., DNS query), the receiver may
      open itself up to resource attacks for the period of time while it
      is waiting for the name resolution results before it can build the
      State Cookie and release local resources.

      Therefore, in cases where the name translation involves potential
      long delay, the receiver of the INIT MUST postpone the name
      resolution till the reception of the COOKIE ECHO chunk from the
      peer.  In such a case, the receiver of the INIT SHOULD build the
      State Cookie using the received Host Name (instead of destination
      transport addresses) and send the INIT ACK to the source IP
      address from which the INIT was received.

      The receiver of an INIT ACK shall always immediately attempt to
      resolve the name upon the reception of the chunk.

      The receiver of the INIT or INIT ACK MUST NOT send user data
      (piggy-backed or stand-alone) to its peer until the host name is
      successfully resolved.

      If the name resolution is not successful, the endpoint MUST
      immediately send an ABORT with "Unresolvable Address" error cause
      to its peer.  The ABORT shall be sent to the source IP address
      from which the last peer packet was received.

   ---------
   New text: (Section 5.1.2)
   ---------

   B) If there is a Host Name parameter present in the received INIT or
      INIT ACK chunk, the endpoint MUST immediately send an ABORT and
      MAY include an Error Cause indicating an Unresolvable Address to
      its peer.  The ABORT SHALL be sent to the source IP address
      from which the last peer packet was received.





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   This text is in final form, and is not further updated in this
   document.

   ---------
   Old text: (Section 11.2.4.1)
   ---------

   The use of the host name feature in the INIT chunk could be used to
   flood a target DNS server.  A large backlog of DNS queries, resolving
   the host name received in the INIT chunk to IP addresses, could be
   accomplished by sending INITs to multiple hosts in a given domain.
   In addition, an attacker could use the host name feature in an
   indirect attack on a third party by sending large numbers of INITs to
   random hosts containing the host name of the target.  In addition to
   the strain on DNS resources, this could also result in large numbers
   of INIT ACKs being sent to the target.  One method to protect against
   this type of attack is to verify that the IP addresses received from
   DNS include the source IP address of the original INIT.  If the list
   of IP addresses received from DNS does not include the source IP
   address of the INIT, the endpoint MAY silently discard the INIT.
   This last option will not protect against the attack against the DNS.

   ---------
   New text: (Section 11.2.4.1)
   ---------

   The support of the Host Name Address parameter has been removed from
   the protocol. Endpoints receiving INIT or INIT ACK chunks containing
   the Host Name Address parameter MUST send an ABORT chunk in response
   and MAY include an Error Cause indicating an Unresolvable Address.

   This text is in final form, and is not further updated in this
   document.

3.41.3.  Solution Description

   The usage of the Host Name Address parameter has been deprecated.

3.42.  Conflicting Text Regarding the Supported Address Types Parameter

3.42.1.  Description of the Problem

   When receiving an SCTP packet containing an INIT chunk sent from an
   address for which the corresponding address type is not listed in the
   Supported Address Types, there is conflicting text in Section 5.1.2
   of [RFC4960].  It is stated that the association MUST be aborted and
   also that the association SHOULD be established and there SHOULD NOT
   be any error indication.



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3.42.2.  Text Changes to the Document

   ---------
   Old text: (Section 5.1.2)
   ---------

   The sender of INIT may include a 'Supported Address Types' parameter
   in the INIT to indicate what types of address are acceptable.  When
   this parameter is present, the receiver of INIT (initiate) MUST
   either use one of the address types indicated in the Supported
   Address Types parameter when responding to the INIT, or abort the
   association with an "Unresolvable Address" error cause if it is
   unwilling or incapable of using any of the address types indicated by
   its peer.

   ---------
   New text: (Section 5.1.2)
   ---------

   The sender of INIT chunks MAY include a 'Supported Address Types'
   parameter in the INIT to indicate what types of addresses are
   acceptable.

   This text is in final form, and is not further updated in this
   document.

3.42.3.  Solution Description

   The conflicting text has been removed.

3.43.  Integration of RFC 6096

3.43.1.  Description of the Problem

   [RFC6096] updates [RFC4960] by adding a Chunk Flags Registry.  This
   should be integrated into the base specification.

3.43.2.  Text Changes to the Document

---------
Old text: (Section 14.1)
---------

14.1.  IETF-Defined Chunk Extension

   The assignment of new chunk parameter type codes is done through an
   IETF Consensus action, as defined in [RFC2434].  Documentation of the
   chunk parameter MUST contain the following information:



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   a) A long and short name for the new chunk type.

   b) A detailed description of the structure of the chunk, which MUST
      conform to the basic structure defined in Section 3.2.

   c) A detailed definition and description of the intended use of each
      field within the chunk, including the chunk flags if any.

   d) A detailed procedural description of the use of the new chunk type
      within the operation of the protocol.

   The last chunk type (255) is reserved for future extension if
   necessary.

---------
New text: (Section 14.1)
---------

14.1.  IETF-Defined Chunk Extension

   The assignment of new chunk type codes is done through an IETF Review
   action, as defined in [RFC8126].  Documentation of a new chunk MUST
   contain the following information:

   a)  A long and short name for the new chunk type;

   b)  A detailed description of the structure of the chunk, which MUST
       conform to the basic structure defined in Section 3.2 of
       [RFC4960];

   c)  A detailed definition and description of the intended use of each
       field within the chunk, including the chunk flags if any.
       Defined chunk flags will be used as initial entries in the chunk
       flags table for the new chunk type;

   d)  A detailed procedural description of the use of the new chunk
       type within the operation of the protocol.

   The last chunk type (255) is reserved for future extension if
   necessary.

   For each new chunk type, IANA creates a registration table for the
   chunk flags of that type.  The procedure for registering particular
   chunk flags is described in the following Section 14.2.

   This text has been modified by multiple errata.  It includes
   modifications from Section 3.3.  It is in final form, and is not
   further updated in this document.



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---------
New text: (Section 14.2)
---------

14.2.  New IETF Chunk Flags Registration

   The assignment of new chunk flags is done through an RFC required
   action, as defined in [RFC8126].  Documentation of the chunk flags
   MUST contain the following information:

   a)  A name for the new chunk flag;

   b)  A detailed procedural description of the use of the new chunk
       flag within the operation of the protocol.  It MUST be considered
       that implementations not supporting the flag will send '0' on
       transmit and just ignore it on receipt.

   IANA selects a chunk flags value.  This MUST be one of 0x01, 0x02,
   0x04, 0x08, 0x10, 0x20, 0x40, or 0x80, which MUST be unique within
   the chunk flag values for the specific chunk type.

   This text is in final form, and is not further updated in this
   document.

   Please note that Sections 14.2, 14.3, 14.4, and 14.5 need to be
   renumbered.

3.43.3.  Solution Description

   [RFC6096] was integrated and the reference updated to [RFC8126].

3.44.  Integration of RFC 6335

3.44.1.  Description of the Problem

   [RFC6335] updates [RFC4960] by updating Procedures for the Port
   Numbers Registry.  This should be integrated into the base
   specification.  While there, update the reference to the RFC giving
   guidelines for writing IANA sections to [RFC8126].

3.44.2.  Text Changes to the Document

   ---------
   Old text: (Section 14.5)
   ---------

   SCTP services may use contact port numbers to provide service to
   unknown callers, as in TCP and UDP.  IANA is therefore requested to



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   open the existing Port Numbers registry for SCTP using the following
   rules, which we intend to mesh well with existing Port Numbers
   registration procedures.  An IESG-appointed Expert Reviewer supports
   IANA in evaluating SCTP port allocation requests, according to the
   procedure defined in [RFC2434].

   Port numbers are divided into three ranges.  The Well Known Ports are
   those from 0 through 1023, the Registered Ports are those from 1024
   through 49151, and the Dynamic and/or Private Ports are those from
   49152 through 65535.  Well Known and Registered Ports are intended
   for use by server applications that desire a default contact point on
   a system.  On most systems, Well Known Ports can only be used by
   system (or root) processes or by programs executed by privileged
   users, while Registered Ports can be used by ordinary user processes
   or programs executed by ordinary users.  Dynamic and/or Private Ports
   are intended for temporary use, including client-side ports, out-of-
   band negotiated ports, and application testing prior to registration
   of a dedicated port; they MUST NOT be registered.

   The Port Numbers registry should accept registrations for SCTP ports
   in the Well Known Ports and Registered Ports ranges.  Well Known and
   Registered Ports SHOULD NOT be used without registration.  Although
   in some cases -- such as porting an application from TCP to SCTP --
   it may seem natural to use an SCTP port before registration
   completes, we emphasize that IANA will not guarantee registration of
   particular Well Known and Registered Ports.  Registrations should be
   requested as early as possible.

   Each port registration SHALL include the following information:

   o  A short port name, consisting entirely of letters (A-Z and a-z),
      digits (0-9), and punctuation characters from "-_+./*" (not
      including the quotes).

   o  The port number that is requested for registration.

   o  A short English phrase describing the port's purpose.

   o  Name and contact information for the person or entity performing
      the registration, and possibly a reference to a document defining
      the port's use.  Registrations coming from IETF working groups
      need only name the working group, but indicating a contact person
      is recommended.

   Registrants are encouraged to follow these guidelines when submitting
   a registration.

   o  A port name SHOULD NOT be registered for more than one SCTP port



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      number.

   o  A port name registered for TCP MAY be registered for SCTP as well.
      Any such registration SHOULD use the same port number as the
      existing TCP registration.

   o  Concrete intent to use a port SHOULD precede port registration.
      For example, existing TCP ports SHOULD NOT be registered in
      advance of any intent to use those ports for SCTP.

   ---------
   New text: (Section 14.5)
   ---------

   SCTP services can use contact port numbers to provide service to
   unknown callers, as in TCP and UDP.  IANA is therefore requested to
   open the existing Port Numbers registry for SCTP using the following
   rules, which we intend to mesh well with existing Port Numbers
   registration procedures.  An IESG-appointed Expert Reviewer supports
   IANA in evaluating SCTP port allocation requests, according to the
   procedure defined in [RFC8126].  The details of this process are
   defined in [RFC6335].

   This text is in final form, and is not further updated in this
   document.

3.44.3.  Solution Description

   [RFC6335] was integrated and the reference was updated to [RFC8126].

3.45.  Integration of RFC 7053

3.45.1.  Description of the Problem

   [RFC7053] updates [RFC4960] by adding the I bit to the DATA chunk.
   This should be integrated into the base specification.

3.45.2.  Text Changes to the Document

---------
Old text: (Section 3.3.1)
---------

The following format MUST be used for the DATA chunk:

     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
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+



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    |   Type = 0    | Reserved|U|B|E|    Length                     |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                              TSN                              |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |      Stream Identifier S      |   Stream Sequence Number n    |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                  Payload Protocol Identifier                  |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    \                                                               \
    /                 User Data (seq n of Stream S)                 /
    \                                                               \
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Reserved: 5 bits

   Should be set to all '0's and ignored by the receiver.

---------
New text: (Section 3.3.1)
---------

     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 = 0    |  Res  |I|U|B|E|    Length                     |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                              TSN                              |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |      Stream Identifier S      |   Stream Sequence Number n    |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                  Payload Protocol Identifier                  |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    \                                                               \
    /                 User Data (seq n of Stream S)                 /
    \                                                               \
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Res: 4 bits

   SHOULD be set to all '0's and ignored by the receiver.

I bit: 1 bit

   The (I)mmediate Bit MAY be set by the sender, whenever the sender of
   a DATA chunk can benefit from the corresponding SACK chunk being sent
   back without delay. See [RFC7053] for a discussion about





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   This text is in final form, and is not further updated in this
   document.

   ---------
   New text: (Append to Section 6.1)
   ---------

   Whenever the sender of a DATA chunk can benefit from the
   corresponding SACK chunk being sent back without delay, the sender
   MAY set the I bit in the DATA chunk header.  Please note that why the
   sender has set the I bit is irrelevant to the receiver.

   Reasons for setting the I bit include, but are not limited to (see
   Section 4 of [RFC7053] for the benefits):

   o  The application requests to set the I bit of the last DATA chunk
      of a user message when providing the user message to the SCTP
      implementation (see Section 7).

   o  The sender is in the SHUTDOWN-PENDING state.

   o  The sending of a DATA chunk fills the congestion or receiver
      window.

   This text is in final form, and is not further updated in this
   document.

   ---------
   Old text: (Section 6.2)
   ---------

   Note: The SHUTDOWN chunk does not contain Gap Ack Block fields.
   Therefore, the endpoint should use a SACK instead of the SHUTDOWN
   chunk to acknowledge DATA chunks received out of order.

   ---------
   New text: (Section 6.2)
   ---------

   Note: The SHUTDOWN chunk does not contain Gap Ack Block fields.
   Therefore, the endpoint SHOULD use a SACK instead of the SHUTDOWN
   chunk to acknowledge DATA chunks received out of order.

   Upon receipt of an SCTP packet containing a DATA chunk with the I bit
   set, the receiver SHOULD NOT delay the sending of the corresponding
   SACK chunk, i.e., the receiver SHOULD immediately respond with the
   corresponding SACK chunk.




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   Please note that this change is only about adding a paragraph.

   This text is in final form, and is not further updated in this
   document.

   ---------
   Old text: (Section 10.1 E))
   ---------

   E) Send

    Format: SEND(association id, buffer address, byte count [,context]
            [,stream id] [,life time] [,destination transport address]
            [,unordered flag] [,no-bundle flag] [,payload protocol-id] )
    -> result

   ---------
   New text: (Section 10.1 E))
   ---------

   E) Send

    Format: SEND(association id, buffer address, byte count [,context]
            [,stream id] [,life time] [,destination transport address]
            [,unordered flag] [,no-bundle flag] [,payload protocol-id]
            [,sack immediately] )
    -> result

   This text is in final form, and is not further updated in this
   document.

   ---------
   New text: (Append optional parameter in Subsection E of Section 10.1)
   ---------

   o  sack immediately - set the I bit on the last DATA chunk used for
      sending buffer.

   This text is in final form, and is not further updated in this
   document.

3.45.3.  Solution Description

   [RFC7053] was integrated.







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3.46.  CRC32c Code Improvements

3.46.1.  Description of the Problem

   The code given for the CRC32c computations uses types like long which
   may have different length on different operating systems or
   processors.  Therefore, the code is changed to use specific types
   like uint32_t.

   While there, fix also some syntax errors and a comment.

3.46.2.  Text Changes to the Document


   ---------
   Old text: (Appendix C)
   ---------
   /*************************************************************/
   /* Note Definition for Ross Williams table generator would   */
   /* be: TB_WIDTH=4, TB_POLLY=0x1EDC6F41, TB_REVER=TRUE        */
   /* For Mr. Williams direct calculation code use the settings */
   /* cm_width=32, cm_poly=0x1EDC6F41, cm_init=0xFFFFFFFF,      */
   /* cm_refin=TRUE, cm_refot=TRUE, cm_xorort=0x00000000        */
   /*************************************************************/

   /* Example of the crc table file */
   #ifndef __crc32cr_table_h__
   #define __crc32cr_table_h__

   #define CRC32C_POLY 0x1EDC6F41
   #define CRC32C(c,d) (c=(c>>8)^crc_c[(c^(d))&0xFF])

   unsigned long  crc_c[256] =
   {
   0x00000000L, 0xF26B8303L, 0xE13B70F7L, 0x1350F3F4L,
   0xC79A971FL, 0x35F1141CL, 0x26A1E7E8L, 0xD4CA64EBL,
   0x8AD958CFL, 0x78B2DBCCL, 0x6BE22838L, 0x9989AB3BL,
   0x4D43CFD0L, 0xBF284CD3L, 0xAC78BF27L, 0x5E133C24L,
   0x105EC76FL, 0xE235446CL, 0xF165B798L, 0x030E349BL,
   0xD7C45070L, 0x25AFD373L, 0x36FF2087L, 0xC494A384L,
   0x9A879FA0L, 0x68EC1CA3L, 0x7BBCEF57L, 0x89D76C54L,
   0x5D1D08BFL, 0xAF768BBCL, 0xBC267848L, 0x4E4DFB4BL,
   0x20BD8EDEL, 0xD2D60DDDL, 0xC186FE29L, 0x33ED7D2AL,
   0xE72719C1L, 0x154C9AC2L, 0x061C6936L, 0xF477EA35L,
   0xAA64D611L, 0x580F5512L, 0x4B5FA6E6L, 0xB93425E5L,
   0x6DFE410EL, 0x9F95C20DL, 0x8CC531F9L, 0x7EAEB2FAL,
   0x30E349B1L, 0xC288CAB2L, 0xD1D83946L, 0x23B3BA45L,




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   0xF779DEAEL, 0x05125DADL, 0x1642AE59L, 0xE4292D5AL,
   0xBA3A117EL, 0x4851927DL, 0x5B016189L, 0xA96AE28AL,
   0x7DA08661L, 0x8FCB0562L, 0x9C9BF696L, 0x6EF07595L,
   0x417B1DBCL, 0xB3109EBFL, 0xA0406D4BL, 0x522BEE48L,
   0x86E18AA3L, 0x748A09A0L, 0x67DAFA54L, 0x95B17957L,
   0xCBA24573L, 0x39C9C670L, 0x2A993584L, 0xD8F2B687L,
   0x0C38D26CL, 0xFE53516FL, 0xED03A29BL, 0x1F682198L,
   0x5125DAD3L, 0xA34E59D0L, 0xB01EAA24L, 0x42752927L,
   0x96BF4DCCL, 0x64D4CECFL, 0x77843D3BL, 0x85EFBE38L,
   0xDBFC821CL, 0x2997011FL, 0x3AC7F2EBL, 0xC8AC71E8L,
   0x1C661503L, 0xEE0D9600L, 0xFD5D65F4L, 0x0F36E6F7L,
   0x61C69362L, 0x93AD1061L, 0x80FDE395L, 0x72966096L,
   0xA65C047DL, 0x5437877EL, 0x4767748AL, 0xB50CF789L,
   0xEB1FCBADL, 0x197448AEL, 0x0A24BB5AL, 0xF84F3859L,
   0x2C855CB2L, 0xDEEEDFB1L, 0xCDBE2C45L, 0x3FD5AF46L,
   0x7198540DL, 0x83F3D70EL, 0x90A324FAL, 0x62C8A7F9L,
   0xB602C312L, 0x44694011L, 0x5739B3E5L, 0xA55230E6L,
   0xFB410CC2L, 0x092A8FC1L, 0x1A7A7C35L, 0xE811FF36L,
   0x3CDB9BDDL, 0xCEB018DEL, 0xDDE0EB2AL, 0x2F8B6829L,
   0x82F63B78L, 0x709DB87BL, 0x63CD4B8FL, 0x91A6C88CL,
   0x456CAC67L, 0xB7072F64L, 0xA457DC90L, 0x563C5F93L,
   0x082F63B7L, 0xFA44E0B4L, 0xE9141340L, 0x1B7F9043L,
   0xCFB5F4A8L, 0x3DDE77ABL, 0x2E8E845FL, 0xDCE5075CL,
   0x92A8FC17L, 0x60C37F14L, 0x73938CE0L, 0x81F80FE3L,
   0x55326B08L, 0xA759E80BL, 0xB4091BFFL, 0x466298FCL,
   0x1871A4D8L, 0xEA1A27DBL, 0xF94AD42FL, 0x0B21572CL,
   0xDFEB33C7L, 0x2D80B0C4L, 0x3ED04330L, 0xCCBBC033L,
   0xA24BB5A6L, 0x502036A5L, 0x4370C551L, 0xB11B4652L,
   0x65D122B9L, 0x97BAA1BAL, 0x84EA524EL, 0x7681D14DL,
   0x2892ED69L, 0xDAF96E6AL, 0xC9A99D9EL, 0x3BC21E9DL,
   0xEF087A76L, 0x1D63F975L, 0x0E330A81L, 0xFC588982L,
   0xB21572C9L, 0x407EF1CAL, 0x532E023EL, 0xA145813DL,
   0x758FE5D6L, 0x87E466D5L, 0x94B49521L, 0x66DF1622L,
   0x38CC2A06L, 0xCAA7A905L, 0xD9F75AF1L, 0x2B9CD9F2L,
   0xFF56BD19L, 0x0D3D3E1AL, 0x1E6DCDEEL, 0xEC064EEDL,
   0xC38D26C4L, 0x31E6A5C7L, 0x22B65633L, 0xD0DDD530L,
   0x0417B1DBL, 0xF67C32D8L, 0xE52CC12CL, 0x1747422FL,
   0x49547E0BL, 0xBB3FFD08L, 0xA86F0EFCL, 0x5A048DFFL,
   0x8ECEE914L, 0x7CA56A17L, 0x6FF599E3L, 0x9D9E1AE0L,
   0xD3D3E1ABL, 0x21B862A8L, 0x32E8915CL, 0xC083125FL,
   0x144976B4L, 0xE622F5B7L, 0xF5720643L, 0x07198540L,
   0x590AB964L, 0xAB613A67L, 0xB831C993L, 0x4A5A4A90L,
   0x9E902E7BL, 0x6CFBAD78L, 0x7FAB5E8CL, 0x8DC0DD8FL,
   0xE330A81AL, 0x115B2B19L, 0x020BD8EDL, 0xF0605BEEL,
   0x24AA3F05L, 0xD6C1BC06L, 0xC5914FF2L, 0x37FACCF1L,
   0x69E9F0D5L, 0x9B8273D6L, 0x88D28022L, 0x7AB90321L,
   0xAE7367CAL, 0x5C18E4C9L, 0x4F48173DL, 0xBD23943EL,
   0xF36E6F75L, 0x0105EC76L, 0x12551F82L, 0xE03E9C81L,



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   0x34F4F86AL, 0xC69F7B69L, 0xD5CF889DL, 0x27A40B9EL,
   0x79B737BAL, 0x8BDCB4B9L, 0x988C474DL, 0x6AE7C44EL,
   0xBE2DA0A5L, 0x4C4623A6L, 0x5F16D052L, 0xAD7D5351L,
   };

   #endif

   ---------
   New text: (Appendix B)
   ---------

   <CODE BEGINS>
   /*************************************************************/
   /* Note Definition for Ross Williams table generator would   */
   /* be: TB_WIDTH=4, TB_POLLY=0x1EDC6F41, TB_REVER=TRUE        */
   /* For Mr. Williams direct calculation code use the settings */
   /* cm_width=32, cm_poly=0x1EDC6F41, cm_init=0xFFFFFFFF,      */
   /* cm_refin=TRUE, cm_refot=TRUE, cm_xorort=0x00000000        */
   /*************************************************************/

   /* Example of the crc table file */
   #ifndef __crc32cr_h__
   #define __crc32cr_h__

   #define CRC32C_POLY 0x1EDC6F41UL
   #define CRC32C(c,d) (c=(c>>8)^crc_c[(c^(d))&0xFF])

   uint32_t crc_c[256] =
   {
   0x00000000UL, 0xF26B8303UL, 0xE13B70F7UL, 0x1350F3F4UL,
   0xC79A971FUL, 0x35F1141CUL, 0x26A1E7E8UL, 0xD4CA64EBUL,
   0x8AD958CFUL, 0x78B2DBCCUL, 0x6BE22838UL, 0x9989AB3BUL,
   0x4D43CFD0UL, 0xBF284CD3UL, 0xAC78BF27UL, 0x5E133C24UL,
   0x105EC76FUL, 0xE235446CUL, 0xF165B798UL, 0x030E349BUL,
   0xD7C45070UL, 0x25AFD373UL, 0x36FF2087UL, 0xC494A384UL,
   0x9A879FA0UL, 0x68EC1CA3UL, 0x7BBCEF57UL, 0x89D76C54UL,
   0x5D1D08BFUL, 0xAF768BBCUL, 0xBC267848UL, 0x4E4DFB4BUL,
   0x20BD8EDEUL, 0xD2D60DDDUL, 0xC186FE29UL, 0x33ED7D2AUL,
   0xE72719C1UL, 0x154C9AC2UL, 0x061C6936UL, 0xF477EA35UL,
   0xAA64D611UL, 0x580F5512UL, 0x4B5FA6E6UL, 0xB93425E5UL,
   0x6DFE410EUL, 0x9F95C20DUL, 0x8CC531F9UL, 0x7EAEB2FAUL,
   0x30E349B1UL, 0xC288CAB2UL, 0xD1D83946UL, 0x23B3BA45UL,
   0xF779DEAEUL, 0x05125DADUL, 0x1642AE59UL, 0xE4292D5AUL,
   0xBA3A117EUL, 0x4851927DUL, 0x5B016189UL, 0xA96AE28AUL,
   0x7DA08661UL, 0x8FCB0562UL, 0x9C9BF696UL, 0x6EF07595UL,
   0x417B1DBCUL, 0xB3109EBFUL, 0xA0406D4BUL, 0x522BEE48UL,
   0x86E18AA3UL, 0x748A09A0UL, 0x67DAFA54UL, 0x95B17957UL,
   0xCBA24573UL, 0x39C9C670UL, 0x2A993584UL, 0xD8F2B687UL,



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   0x0C38D26CUL, 0xFE53516FUL, 0xED03A29BUL, 0x1F682198UL,
   0x5125DAD3UL, 0xA34E59D0UL, 0xB01EAA24UL, 0x42752927UL,
   0x96BF4DCCUL, 0x64D4CECFUL, 0x77843D3BUL, 0x85EFBE38UL,
   0xDBFC821CUL, 0x2997011FUL, 0x3AC7F2EBUL, 0xC8AC71E8UL,
   0x1C661503UL, 0xEE0D9600UL, 0xFD5D65F4UL, 0x0F36E6F7UL,
   0x61C69362UL, 0x93AD1061UL, 0x80FDE395UL, 0x72966096UL,
   0xA65C047DUL, 0x5437877EUL, 0x4767748AUL, 0xB50CF789UL,
   0xEB1FCBADUL, 0x197448AEUL, 0x0A24BB5AUL, 0xF84F3859UL,
   0x2C855CB2UL, 0xDEEEDFB1UL, 0xCDBE2C45UL, 0x3FD5AF46UL,
   0x7198540DUL, 0x83F3D70EUL, 0x90A324FAUL, 0x62C8A7F9UL,
   0xB602C312UL, 0x44694011UL, 0x5739B3E5UL, 0xA55230E6UL,
   0xFB410CC2UL, 0x092A8FC1UL, 0x1A7A7C35UL, 0xE811FF36UL,
   0x3CDB9BDDUL, 0xCEB018DEUL, 0xDDE0EB2AUL, 0x2F8B6829UL,
   0x82F63B78UL, 0x709DB87BUL, 0x63CD4B8FUL, 0x91A6C88CUL,
   0x456CAC67UL, 0xB7072F64UL, 0xA457DC90UL, 0x563C5F93UL,
   0x082F63B7UL, 0xFA44E0B4UL, 0xE9141340UL, 0x1B7F9043UL,
   0xCFB5F4A8UL, 0x3DDE77ABUL, 0x2E8E845FUL, 0xDCE5075CUL,
   0x92A8FC17UL, 0x60C37F14UL, 0x73938CE0UL, 0x81F80FE3UL,
   0x55326B08UL, 0xA759E80BUL, 0xB4091BFFUL, 0x466298FCUL,
   0x1871A4D8UL, 0xEA1A27DBUL, 0xF94AD42FUL, 0x0B21572CUL,
   0xDFEB33C7UL, 0x2D80B0C4UL, 0x3ED04330UL, 0xCCBBC033UL,
   0xA24BB5A6UL, 0x502036A5UL, 0x4370C551UL, 0xB11B4652UL,
   0x65D122B9UL, 0x97BAA1BAUL, 0x84EA524EUL, 0x7681D14DUL,
   0x2892ED69UL, 0xDAF96E6AUL, 0xC9A99D9EUL, 0x3BC21E9DUL,
   0xEF087A76UL, 0x1D63F975UL, 0x0E330A81UL, 0xFC588982UL,
   0xB21572C9UL, 0x407EF1CAUL, 0x532E023EUL, 0xA145813DUL,
   0x758FE5D6UL, 0x87E466D5UL, 0x94B49521UL, 0x66DF1622UL,
   0x38CC2A06UL, 0xCAA7A905UL, 0xD9F75AF1UL, 0x2B9CD9F2UL,
   0xFF56BD19UL, 0x0D3D3E1AUL, 0x1E6DCDEEUL, 0xEC064EEDUL,
   0xC38D26C4UL, 0x31E6A5C7UL, 0x22B65633UL, 0xD0DDD530UL,
   0x0417B1DBUL, 0xF67C32D8UL, 0xE52CC12CUL, 0x1747422FUL,
   0x49547E0BUL, 0xBB3FFD08UL, 0xA86F0EFCUL, 0x5A048DFFUL,
   0x8ECEE914UL, 0x7CA56A17UL, 0x6FF599E3UL, 0x9D9E1AE0UL,
   0xD3D3E1ABUL, 0x21B862A8UL, 0x32E8915CUL, 0xC083125FUL,
   0x144976B4UL, 0xE622F5B7UL, 0xF5720643UL, 0x07198540UL,
   0x590AB964UL, 0xAB613A67UL, 0xB831C993UL, 0x4A5A4A90UL,
   0x9E902E7BUL, 0x6CFBAD78UL, 0x7FAB5E8CUL, 0x8DC0DD8FUL,
   0xE330A81AUL, 0x115B2B19UL, 0x020BD8EDUL, 0xF0605BEEUL,
   0x24AA3F05UL, 0xD6C1BC06UL, 0xC5914FF2UL, 0x37FACCF1UL,
   0x69E9F0D5UL, 0x9B8273D6UL, 0x88D28022UL, 0x7AB90321UL,
   0xAE7367CAUL, 0x5C18E4C9UL, 0x4F48173DUL, 0xBD23943EUL,
   0xF36E6F75UL, 0x0105EC76UL, 0x12551F82UL, 0xE03E9C81UL,
   0x34F4F86AUL, 0xC69F7B69UL, 0xD5CF889DUL, 0x27A40B9EUL,
   0x79B737BAUL, 0x8BDCB4B9UL, 0x988C474DUL, 0x6AE7C44EUL,
   0xBE2DA0A5UL, 0x4C4623A6UL, 0x5F16D052UL, 0xAD7D5351UL,
   };

   #endif



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   This text has been modified by multiple errata.  It includes
   modifications from Section 3.10.  It is in final form, and is not
   further updated in this document.


   ---------
   Old text: (Appendix C)
   ---------

   /* Example of table build routine */

   #include <stdio.h>
   #include <stdlib.h>

   #define OUTPUT_FILE   "crc32cr.h"
   #define CRC32C_POLY    0x1EDC6F41L
   FILE *tf;
   unsigned long
   reflect_32 (unsigned long b)
   {
     int i;
     unsigned long rw = 0L;

     for (i = 0; i < 32; i++){
         if (b & 1)
           rw |= 1 << (31 - i);
         b >>= 1;
     }
     return (rw);
   }

   unsigned long
   build_crc_table (int index)
   {
     int i;
     unsigned long rb;

     rb = reflect_32 (index);

     for (i = 0; i < 8; i++){
         if (rb & 0x80000000L)
          rb = (rb << 1) ^ CRC32C_POLY;
         else
          rb <<= 1;
     }
     return (reflect_32 (rb));
   }




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   main ()
   {
     int i;

     printf ("\nGenerating CRC-32c table file <%s>\n",
     OUTPUT_FILE);
     if ((tf = fopen (OUTPUT_FILE, "w")) == NULL){
         printf ("Unable to open %s\n", OUTPUT_FILE);
         exit (1);
     }
     fprintf (tf, "#ifndef __crc32cr_table_h__\n");
     fprintf (tf, "#define __crc32cr_table_h__\n\n");
     fprintf (tf, "#define CRC32C_POLY 0x%08lX\n",
     CRC32C_POLY);
     fprintf (tf,
     "#define CRC32C(c,d) (c=(c>>8)^crc_c[(c^(d))&0xFF])\n");
     fprintf (tf, "\nunsigned long  crc_c[256] =\n{\n");
     for (i = 0; i < 256; i++){
         fprintf (tf, "0x%08lXL, ", build_crc_table (i));
         if ((i & 3) == 3)
           fprintf (tf, "\n");
     }
     fprintf (tf, "};\n\n#endif\n");

     if (fclose (tf) != 0)
       printf ("Unable to close <%s>." OUTPUT_FILE);
     else
       printf ("\nThe CRC-32c table has been written to <%s>.\n",
         OUTPUT_FILE);
   }

   ---------
   New text: (Appendix B)
   ---------

   /* Example of table build routine */

   #include <stdio.h>
   #include <stdlib.h>

   #define OUTPUT_FILE   "crc32cr.h"
   #define CRC32C_POLY    0x1EDC6F41UL

   static FILE *tf;

   static uint32_t
   reflect_32(uint32_t b)
   {



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     int i;
     uint32_t rw = 0UL;

     for (i = 0; i < 32; i++) {
         if (b & 1)
           rw |= 1 << (31 - i);
         b >>= 1;
     }
     return (rw);
   }

   static uint32_t
   build_crc_table(int index)
   {
     int i;
     uint32_t rb;

     rb = reflect_32(index);

     for (i = 0; i < 8; i++) {
         if (rb & 0x80000000UL)
          rb = (rb << 1) ^ (uint32_t)CRC32C_POLY;
         else
          rb <<= 1;
     }
     return (reflect_32(rb));
   }

   int
   main (void)
   {
     int i;

     printf("\nGenerating CRC-32c table file <%s>\n",
     OUTPUT_FILE);
     if ((tf = fopen(OUTPUT_FILE, "w")) == NULL) {
         printf ("Unable to open %s\n", OUTPUT_FILE);
         exit (1);
     }
     fprintf(tf, "#ifndef __crc32cr_h__\n");
     fprintf(tf, "#define __crc32cr_h__\n\n");
     fprintf(tf, "#define CRC32C_POLY 0x%08XUL\n",
       (uint32_t)CRC32C_POLY);
     fprintf(tf,
       "#define CRC32C(c,d) (c=(c>>8)^crc_c[(c^(d))&0xFF])\n");
     fprintf(tf, "\nuint32_t crc_c[256] =\n{\n");
     for (i = 0; i < 256; i++) {
         fprintf(tf, "0x%08XUL,", build_crc_table (i));



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         if ((i & 3) == 3)
           fprintf(tf, "\n");
         else
           fprintf(tf, " ");
     }
     fprintf(tf, "};\n\n#endif\n");

     if (fclose (tf) != 0)
       printf("Unable to close <%s>.", OUTPUT_FILE);
     else
       printf("\nThe CRC-32c table has been written to <%s>.\n",
         OUTPUT_FILE);
   }


   This text has been modified by multiple errata.  It includes
   modifications from Section 3.10.  It is in final form, and is not
   further updated in this document.


   ---------
   Old text: (Appendix C)
   ---------

   /* Example of crc insertion */

   #include "crc32cr.h"

   unsigned long
   generate_crc32c(unsigned char *buffer, unsigned int length)
   {
     unsigned int i;
     unsigned long crc32 = ~0L;
     unsigned long result;
     unsigned char byte0,byte1,byte2,byte3;

     for (i = 0; i < length; i++){
         CRC32C(crc32, buffer[i]);
     }

     result = ~crc32;

     /*  result now holds the negated polynomial remainder;
      *  since the table and algorithm is "reflected" [williams95].
      *  That is, result has the same value as if we mapped the message
      *  to a polynomial, computed the host-bit-order polynomial
      *  remainder, performed final negation, then did an end-for-end
      *  bit-reversal.



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      *  Note that a 32-bit bit-reversal is identical to four inplace
      *  8-bit reversals followed by an end-for-end byteswap.
      *  In other words, the bytes of each bit are in the right order,
      *  but the bytes have been byteswapped.  So we now do an explicit
      *  byteswap.  On a little-endian machine, this byteswap and
      *  the final ntohl cancel out and could be elided.
      */

     byte0 = result & 0xff;
     byte1 = (result>>8) & 0xff;
     byte2 = (result>>16) & 0xff;
     byte3 = (result>>24) & 0xff;
     crc32 = ((byte0 << 24) |
              (byte1 << 16) |
              (byte2 << 8)  |
              byte3);
     return ( crc32 );
   }

   int
   insert_crc32(unsigned char *buffer, unsigned int length)
   {
     SCTP_message *message;
     unsigned long crc32;
     message = (SCTP_message *) buffer;
     message->common_header.checksum = 0L;
     crc32 = generate_crc32c(buffer,length);
     /* and insert it into the message */
     message->common_header.checksum = htonl(crc32);
     return 1;
   }

   int
   validate_crc32(unsigned char *buffer, unsigned int length)
   {
     SCTP_message *message;
     unsigned int i;
     unsigned long original_crc32;
     unsigned long crc32 = ~0L;

     /* save and zero checksum */
     message = (SCTP_message *) buffer;
     original_crc32 = ntohl(message->common_header.checksum);
     message->common_header.checksum = 0L;
     crc32 = generate_crc32c(buffer,length);
     return ((original_crc32 == crc32)? 1 : -1);
   }




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   ---------
   New text: (Appendix B)
   ---------

   /* Example of crc insertion */

   #include "crc32cr.h"

   uint32_t
   generate_crc32c(unsigned char *buffer, unsigned int length)
   {
     unsigned int i;
     uint32_t crc32 = 0xffffffffUL;
     uint32_t result;
     uint8_t byte0, byte1, byte2, byte3;

     for (i = 0; i < length; i++) {
         CRC32C(crc32, buffer[i]);
     }

     result = ~crc32;

     /*  result now holds the negated polynomial remainder;
      *  since the table and algorithm is "reflected" [williams95].
      *  That is, result has the same value as if we mapped the message
      *  to a polynomial, computed the host-bit-order polynomial
      *  remainder, performed final negation, then did an end-for-end
      *  bit-reversal.
      *  Note that a 32-bit bit-reversal is identical to four inplace
      *  8-bit reversals followed by an end-for-end byteswap.
      *  In other words, the bits of each byte are in the right order,
      *  but the bytes have been byteswapped.  So we now do an explicit
      *  byteswap.  On a little-endian machine, this byteswap and
      *  the final ntohl cancel out and could be elided.
      */

     byte0 = result & 0xff;
     byte1 = (result>>8) & 0xff;
     byte2 = (result>>16) & 0xff;
     byte3 = (result>>24) & 0xff;
     crc32 = ((byte0 << 24) |
              (byte1 << 16) |
              (byte2 << 8)  |
              byte3);
     return (crc32);
   }

   int



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   insert_crc32(unsigned char *buffer, unsigned int length)
   {
     SCTP_message *message;
     uint32_t crc32;
     message = (SCTP_message *) buffer;
     message->common_header.checksum = 0UL;
     crc32 = generate_crc32c(buffer,length);
     /* and insert it into the message */
     message->common_header.checksum = htonl(crc32);
     return 1;
   }

   int
   validate_crc32(unsigned char *buffer, unsigned int length)
   {
     SCTP_message *message;
     unsigned int i;
     uint32_t original_crc32;
     uint32_t crc32;

     /* save and zero checksum */
     message = (SCTP_message *)buffer;
     original_crc32 = ntohl(message->common_header.checksum);
     message->common_header.checksum = 0L;
     crc32 = generate_crc32c(buffer, length);
     return ((original_crc32 == crc32)? 1 : -1);
   }
   <CODE ENDS>


   This text has been modified by multiple errata.  It includes
   modifications from Section 3.5 and Section 3.10.  It is in final
   form, and is not further updated in this document.

3.46.3.  Solution Description

   The code was changed to use platform independent types.

3.47.  Clarification of Gap Ack Blocks in SACK Chunks

3.47.1.  Description of the Problem

   The Gap Ack Blocks in the SACK chunk are intended to be isolated.
   However, this is not mentioned with normative text.

   This issue was reported as part of an Errata for [RFC4960] with
   Errata ID 5202.




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3.47.2.  Text Changes to the Document

---------
Old text: (Section 3.3.4)
---------

The SACK also contains zero or more Gap Ack Blocks.  Each Gap Ack
Block acknowledges a subsequence of TSNs received following a break
in the sequence of received TSNs.  By definition, all TSNs
acknowledged by Gap Ack Blocks are greater than the value of the
Cumulative TSN Ack.

---------
New text: (Section 3.3.4)
---------

The SACK also contains zero or more Gap Ack Blocks.  Each Gap Ack
Block acknowledges a subsequence of TSNs received following a break
in the sequence of received TSNs. The Gap Ack Blocks SHOULD be isolated.
This means that the TSN just before each Gap Ack Block and the TSN just
after each Gap Ack Block has not been received.  By definition, all TSNs
acknowledged by Gap Ack Blocks are greater than the value of the
Cumulative TSN Ack.

   This text is in final form, and is not further updated in this
   document.

























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   ---------
   Old text: (Section 3.3.4)
   ---------

   Gap Ack Blocks:

      These fields contain the Gap Ack Blocks.  They are repeated for
      each Gap Ack Block up to the number of Gap Ack Blocks defined in
      the Number of Gap Ack Blocks field.  All DATA chunks with TSNs
      greater than or equal to (Cumulative TSN Ack + Gap Ack Block
      Start) and less than or equal to (Cumulative TSN Ack + Gap Ack
      Block End) of each Gap Ack Block are assumed to have been received
      correctly.

   ---------
   New text: (Section 3.3.4)
   ---------

   Gap Ack Blocks:

      These fields contain the Gap Ack Blocks.  They are repeated for
      each Gap Ack Block up to the number of Gap Ack Blocks defined in
      the Number of Gap Ack Blocks field.  All DATA chunks with TSNs
      greater than or equal to (Cumulative TSN Ack + Gap Ack Block
      Start) and less than or equal to (Cumulative TSN Ack + Gap Ack
      Block End) of each Gap Ack Block are assumed to have been received
      correctly. Gap Ack Blocks SHOULD be isolated.  That means that
      the DATA chunks with TSN equal to (Cumulative TSN Ack + Gap Ack
      Block Start - 1) and (Cumulative TSN Ack + Gap Ack Block End + 1)
      have not been received.

   This text is in final form, and is not further updated in this
   document.

3.47.3.  Solution Description

   Normative text describing the intended usage of Gap Ack Blocks has
   been added.

3.48.  Handling of SSN Wrap Arounds

3.48.1.  Description of the Problem

   The Stream Sequence Number (SSN) is used for preserving the ordering
   of user messages within each SCTP stream.  The SSN is limited to 16
   bits.  Therefore, multiple wrap arounds of the SSN might happen
   within the current send window.  To allow the receiver to deliver




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   ordered user messages in the correct sequence, the sender should
   limit the number of user messages per stream.

3.48.2.  Text Changes to the Document

---------
Old text: (Section 6.1)
---------

Note: The data sender SHOULD NOT use a TSN that is more than 2**31 -
1 above the beginning TSN of the current send window.

---------
New text: (Section 6.1)
---------

Note: The data sender SHOULD NOT use a TSN that is more than 2**31 -
1 above the beginning TSN of the current send window.
Note: For each stream, the data sender SHOULD NOT have more than 2**16-1
ordered user messages in the current send window.

   This text is in final form, and is not further updated in this
   document.

3.48.3.  Solution Description

   The data sender is required to limit the number of ordered user
   messages within the current send window.

3.49.  Update RFC 2119 Boilerplate

3.49.1.  Description of the Problem

   The text to be used to refer to the [RFC2119] terms has been updated
   by [RFC8174].

3.49.2.  Text Changes to the Document














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   ---------
   Old text: (Section 2)
   ---------

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in RFC 2119 [RFC2119].

   ---------
   New text: (Section 2)
   ---------

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
   "OPTIONAL" in this document are to be interpreted as described in
   BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all
   capitals, as shown here.

   This text is in final form, and is not further updated in this
   document.

3.49.3.  Solution Description

   The text has been updated to the one specified in [RFC8174].

3.50.  Missed Text Removal

3.50.1.  Description of the Problem

   When integrating the changes to Section 7.2.4 of [RFC2960] as
   described in Section 2.8.2 of [RFC4460] some text was not removed and
   is therefore still in [RFC4960].

3.50.2.  Text Changes to the Document

















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   ---------
   Old text: (Section 7.2.4)
   ---------

   A straightforward implementation of the above keeps a counter for
   each TSN hole reported by a SACK.  The counter increments for each
   consecutive SACK reporting the TSN hole.  After reaching 3 and
   starting the Fast-Retransmit procedure, the counter resets to 0.
   Because cwnd in SCTP indirectly bounds the number of outstanding
   TSN's, the effect of TCP Fast Recovery is achieved automatically with
   no adjustment to the congestion control window size.

   ---------
   New text: (Section 7.2.4)
   ---------

   This text is in final form, and is not further updated in this
   document.

3.50.3.  Solution Description

   The text has finally been removed.

4.  IANA Considerations

   Section 3.44 of this document updates the port number registry for
   SCTP to be consistent with [RFC6335].  IANA is requested to review
   Section 3.44.

   IANA is only requested to check if it is OK to make the proposed text
   change in an upcoming standards track document that updates
   [RFC4960].  IANA is not asked to perform any other action and this
   document does not request IANA to make a change to any registry.

5.  Security Considerations

   This document does not add any security considerations to those given
   in [RFC4960].

6.  Acknowledgments

   The authors wish to thank Pontus Andersson, Eric W.  Biederman,
   Cedric Bonnet, Spencer Dawkins, Gorry Fairhurst, Benjamin Kaduk,
   Mirja Kuehlewind, Peter Lei, Gyula Marosi, Lionel Morand, Jeff
   Morriss, Karen E.  E.  Nielsen, Tom Petch, Kacheong Poon, Julien
   Pourtet, Irene Ruengeler, Michael Welzl, and Qiaobing Xie for their
   invaluable comments.




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7.  References

7.1.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,
              <https://www.rfc-editor.org/info/rfc2119>.

   [RFC4960]  Stewart, R., Ed., "Stream Control Transmission Protocol",
              RFC 4960, DOI 10.17487/RFC4960, September 2007,
              <https://www.rfc-editor.org/info/rfc4960>.

7.2.  Informative References

   [RFC1122]  Braden, R., Ed., "Requirements for Internet Hosts -
              Communication Layers", STD 3, RFC 1122,
              DOI 10.17487/RFC1122, October 1989,
              <https://www.rfc-editor.org/info/rfc1122>.

   [RFC1858]  Ziemba, G., Reed, D., and P. Traina, "Security
              Considerations for IP Fragment Filtering", RFC 1858,
              DOI 10.17487/RFC1858, October 1995,
              <https://www.rfc-editor.org/info/rfc1858>.

   [RFC2960]  Stewart, R., Xie, Q., Morneault, K., Sharp, C.,
              Schwarzbauer, H., Taylor, T., Rytina, I., Kalla, M.,
              Zhang, L., and V. Paxson, "Stream Control Transmission
              Protocol", RFC 2960, DOI 10.17487/RFC2960, October 2000,
              <https://www.rfc-editor.org/info/rfc2960>.

   [RFC3168]  Ramakrishnan, K., Floyd, S., and D. Black, "The Addition
              of Explicit Congestion Notification (ECN) to IP",
              RFC 3168, DOI 10.17487/RFC3168, September 2001,
              <https://www.rfc-editor.org/info/rfc3168>.

   [RFC4460]  Stewart, R., Arias-Rodriguez, I., Poon, K., Caro, A., and
              M. Tuexen, "Stream Control Transmission Protocol (SCTP)
              Specification Errata and Issues", RFC 4460,
              DOI 10.17487/RFC4460, April 2006,
              <https://www.rfc-editor.org/info/rfc4460>.

   [RFC5681]  Allman, M., Paxson, V., and E. Blanton, "TCP Congestion
              Control", RFC 5681, DOI 10.17487/RFC5681, September 2009,
              <https://www.rfc-editor.org/info/rfc5681>.






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   [RFC6096]  Tuexen, M. and R. Stewart, "Stream Control Transmission
              Protocol (SCTP) Chunk Flags Registration", RFC 6096,
              DOI 10.17487/RFC6096, January 2011,
              <https://www.rfc-editor.org/info/rfc6096>.

   [RFC6298]  Paxson, V., Allman, M., Chu, J., and M. Sargent,
              "Computing TCP's Retransmission Timer", RFC 6298,
              DOI 10.17487/RFC6298, June 2011,
              <https://www.rfc-editor.org/info/rfc6298>.

   [RFC6335]  Cotton, M., Eggert, L., Touch, J., Westerlund, M., and S.
              Cheshire, "Internet Assigned Numbers Authority (IANA)
              Procedures for the Management of the Service Name and
              Transport Protocol Port Number Registry", BCP 165,
              RFC 6335, DOI 10.17487/RFC6335, August 2011,
              <https://www.rfc-editor.org/info/rfc6335>.

   [RFC7053]  Tuexen, M., Ruengeler, I., and R. Stewart, "SACK-
              IMMEDIATELY Extension for the Stream Control Transmission
              Protocol", RFC 7053, DOI 10.17487/RFC7053, November 2013,
              <https://www.rfc-editor.org/info/rfc7053>.

   [RFC8126]  Cotton, M., Leiba, B., and T. Narten, "Guidelines for
              Writing an IANA Considerations Section in RFCs", BCP 26,
              RFC 8126, DOI 10.17487/RFC8126, June 2017,
              <https://www.rfc-editor.org/info/rfc8126>.

   [RFC8174]  Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
              2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
              May 2017, <https://www.rfc-editor.org/info/rfc8174>.

   [RFC8311]  Black, D., "Relaxing Restrictions on Explicit Congestion
              Notification (ECN) Experimentation", RFC 8311,
              DOI 10.17487/RFC8311, January 2018,
              <https://www.rfc-editor.org/info/rfc8311>.

Authors' Addresses

   Randall R. Stewart
   Netflix, Inc.
   Chapin, SC  29036
   United States

   Email: randall@lakerest.net







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   Michael Tuexen
   Muenster University of Applied Sciences
   Stegerwaldstrasse 39
   48565 Steinfurt
   Germany

   Email: tuexen@fh-muenster.de


   Maksim Proshin
   Ericsson
   Kistavaegen 25
   Stockholm  164 80
   Sweden

   Email: mproshin@tieto.mera.ru



































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