GENWiki

Premier IT Outsourcing and Support Services within the UK

User Tools

Site Tools


rfc:rfc8540

Internet Engineering Task Force (IETF) R. Stewart Request for Comments: 8540 Netflix, Inc. Category: Informational M. Tuexen ISSN: 2070-1721 Muenster Univ. of Appl. Sciences

                                                            M. Proshin
                                                              Ericsson
                                                         February 2019
               Stream Control Transmission Protocol:
                   Errata and Issues in RFC 4960

Abstract

 This document is a compilation of issues found since the publication
 of RFC 4960 in September 2007, based on experience with implementing,
 testing, and using the Stream Control Transmission Protocol (SCTP)
 along with the suggested fixes.  This document provides deltas to RFC
 4960 and is organized in a time-ordered way.  The issues are listed
 in the order in which they were brought up.  Because some text is
 changed several times, the last delta in the text is the one that
 should be applied.  In addition to the deltas, a description of each
 problem and the details of the solution for each are also provided.

Status of This Memo

 This document is not an Internet Standards Track specification; it is
 published for informational purposes.
 This document is a product of the Internet Engineering Task Force
 (IETF).  It represents the consensus of the IETF community.  It has
 received public review and has been approved for publication by the
 Internet Engineering Steering Group (IESG).  Not all documents
 approved by the IESG are candidates for any level of Internet
 Standard; see Section 2 of RFC 7841.
 Information about the current status of this document, any errata,
 and how to provide feedback on it may be obtained at
 https://www.rfc-editor.org/info/rfc8540.

Stewart, et al. Informational [Page 1] RFC 8540 SCTP: Errata and Issues in RFC 4960 February 2019

Copyright Notice

 Copyright (c) 2019 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
 (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 . . . . . . .  19
   3.12. Order of Adjustments of partial_bytes_acked and cwnd  . .  20
   3.13. HEARTBEAT ACK and the Association Error Counter . . . . .  21
   3.14. Path for Fast Retransmission  . . . . . . . . . . . . . .  22
   3.15. Transmittal in Fast Recovery  . . . . . . . . . . . . . .  23
   3.16. Initial Value of ssthresh . . . . . . . . . . . . . . . .  24
   3.17. Automatically CONFIRMED Addresses . . . . . . . . . . . .  25
   3.18. Only One Packet after Retransmission Timeout  . . . . . .  26
   3.19. INIT ACK Path for INIT in COOKIE-WAIT State . . . . . . .  27
   3.20. Zero Window Probing and Unreachable Primary Path  . . . .  28
   3.21. Normative Language in Section 10 of RFC 4960  . . . . . .  29
   3.22. Increase of partial_bytes_acked in Congestion Avoidance .  32
   3.23. Inconsistent Handling of Notifications  . . . . . . . . .  33
   3.24. SACK.Delay Not Listed as a Protocol Parameter . . . . . .  37
   3.25. Processing of Chunks in an Incoming SCTP Packet . . . . .  39
   3.26. Increasing the cwnd in the Congestion Avoidance Phase . .  41
   3.27. Refresh of cwnd and ssthresh after Idle Period  . . . . .  43
   3.28. Window Updates after Receiver Window Opens Up . . . . . .  45

Stewart, et al. Informational [Page 2] RFC 8540 SCTP: Errata and Issues in RFC 4960 February 2019

   3.29. Path of DATA and Reply Chunks . . . . . . . . . . . . . .  46
   3.30. "Outstanding Data", "Flightsize", and "Data in Flight"
         Key Terms . . . . . . . . . . . . . . . . . . . . . . . .  47
   3.31. Degradation of cwnd due to Max.Burst  . . . . . . . . . .  49
   3.32. Reduction of RTO.Initial  . . . . . . . . . . . . . . . .  50
   3.33. Ordering of Bundled SACK and ERROR Chunks . . . . . . . .  51
   3.34. Undefined Parameter Returned by RECEIVE Primitive . . . .  52
   3.35. DSCP Changes  . . . . . . . . . . . . . . . . . . . . . .  53
   3.36. Inconsistent Handling of ICMPv4 and ICMPv6 Messages . . .  55
   3.37. Handling of Soft Errors . . . . . . . . . . . . . . . . .  56
   3.38. Honoring cwnd . . . . . . . . . . . . . . . . . . . . . .  57
   3.39. Zero Window Probing . . . . . . . . . . . . . . . . . . .  58
   3.40. Updating References regarding ECN . . . . . . . . . . . .  60
   3.41. Host Name Address Parameter Deprecated  . . . . . . . . .  62
   3.42. Conflicting Text regarding the 'Supported Address Types'
         Parameter . . . . . . . . . . . . . . . . . . . . . . . .  66
   3.43. Integration of RFC 6096 . . . . . . . . . . . . . . . . .  67
   3.44. Integration of RFC 6335 . . . . . . . . . . . . . . . . .  70
   3.45. Integration of RFC 7053 . . . . . . . . . . . . . . . . .  72
   3.46. CRC32c Code Improvements  . . . . . . . . . . . . . . . .  76
   3.47. Clarification of Gap Ack Blocks in SACK Chunks  . . . . .  87
   3.48. Handling of SSN Wraparounds . . . . . . . . . . . . . . .  89
   3.49. Update to RFC 2119 Boilerplate Text . . . . . . . . . . .  90
   3.50. Removal of Text (Previously Missed in RFC 4960) . . . . .  91
 4.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  91
 5.  Security Considerations . . . . . . . . . . . . . . . . . . .  92
 6.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  92
   6.1.  Normative References  . . . . . . . . . . . . . . . . . .  92
   6.2.  Informative References  . . . . . . . . . . . . . . . . .  92
 Acknowledgements  . . . . . . . . . . . . . . . . . . . . . . . .  94
 Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  94

1. Introduction

 This document contains a compilation of all defects for [RFC4960]
 ("Stream Control Transmission Protocol") that were found up until the
 publication of this document.  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 the Stream Control
 Transmission Protocol (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 similarly to
 [RFC4460].

Stewart, et al. Informational [Page 3] RFC 8540 SCTP: Errata and Issues in RFC 4960 February 2019

 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, and
 o  A description of the solution.
 Note that when reading this document one must use care to ensure that
 a field or item is not updated later on within the document.  Since
 this document is a historical record of the sequential changes that
 have been found necessary at various interop events and through
 discussion on the Transport Area Working Group mailing list, the last
 delta in the text is the one that 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

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
 Sections 8.2 and 8.3 of [RFC4960] in an inconsistent way.  Whereas
 Section 8.2 of [RFC4960] says that a path is marked inactive when the
 path error counter exceeds the threshold, Section 8.3 of [RFC4960]
 says that 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.

Stewart, et al. Informational [Page 4] RFC 8540 SCTP: Errata and Issues in RFC 4960 February 2019

3.1.2. Text Changes to the Document

  1. ——–

Old text: (Section 8.3)

  1. ——–
 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.
  1. ——–

New text: (Section 8.3)

  1. ——–
 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 in 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.

Stewart, et al. Informational [Page 5] RFC 8540 SCTP: Errata and Issues in RFC 4960 February 2019

3.2.2. Text Changes to the Document

  1. ——–

Old text: (Section 9.2)

  1. ——–
 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.
  1. ——–

New text: (Section 9.2)

  1. ——–
 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 that the SCTP endpoint 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 only 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

  1. ——–

Old text: (Section 14.1)

  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:

Stewart, et al. Informational [Page 6] RFC 8540 SCTP: Errata and Issues in RFC 4960 February 2019

  1. ——–

New text: (Section 14.1)

  1. ——–
 The assignment of new chunk type codes is done through an IETF
 Consensus action, as defined in [RFC8126].  Documentation for 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

 The new text refers to chunk types as intended and changes the
 reference to [RFC8126].

3.4. Variable Parameters for INIT Chunks

3.4.1. Description of the Problem

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

  1. ——–

Old text: (Section 3.3.2)

  1. ——–
 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

Stewart, et al. Informational [Page 7] RFC 8540 SCTP: Errata and Issues in RFC 4960 February 2019

  1. ——–

New text: (Section 3.3.2)

  1. ——–
 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

 The formatting of the table is corrected.

3.5. CRC32c Sample Code on 64-Bit Platforms

3.5.1. Description of the Problem

 The sample code for CRC32c computation, as 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, platforms that
 use LP64).
 This issue was reported as an errata for [RFC4960] with
 Errata ID 3423.

3.5.2. Text Changes to the Document

  1. ——–

Old text: (Appendix C)

  1. ——–
 unsigned long
 generate_crc32c(unsigned char *buffer, unsigned int length)
 {
   unsigned int i;
   unsigned long crc32 = ~0L;

Stewart, et al. Informational [Page 8] RFC 8540 SCTP: Errata and Issues in RFC 4960 February 2019

  1. ——–

New text: (Appendix C)

  1. ——–
 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 again in Section 3.46.

3.5.3. Solution Description

 The new text uses 0xffffffffL instead of ~0L; this 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

  1. ——–

Old text: (Section 8.1)

  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.
  1. ——–

New text: (Section 8.1)

  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

Stewart, et al. Informational [Page 9] RFC 8540 SCTP: Errata and Issues in RFC 4960 February 2019

 multi-homed), including the number of unacknowledged HEARTBEAT chunks
 observed on the path that 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 that 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 of 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

  1. ——–

Old text: (Section 6.1 A))

  1. ——–
 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.

Stewart, et al. Informational [Page 10] RFC 8540 SCTP: Errata and Issues in RFC 4960 February 2019

  1. ——–

New text: (Section 6.1 A))

  1. ——–
 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 algorithm 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

 The last paragraph of Section 6.1 A) is removed, as had been 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.

3.8.2. Text Changes to the Document

  1. ——–

Old text: (Section 5.1.6, Figure 4)

  1. ——–
 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)

Stewart, et al. Informational [Page 11] RFC 8540 SCTP: Errata and Issues in RFC 4960 February 2019

  1. ——–

New text: (Section 5.1.6, Figure 4)

  1. ——–
 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

 The figure is changed 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.

3.9.2. Text Changes to the Document

  1. ——–

Old text: (Section 1.6)

  1. ——–
 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.

Stewart, et al. Informational [Page 12] RFC 8540 SCTP: Errata and Issues in RFC 4960 February 2019

  1. ——–

New text: (Section 1.6)

  1. ——–
 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.
  1. ——–

Old text: (Section 3.3.10.9)

  1. ——–
 No User Data: This error cause is returned to the originator of a
 DATA chunk if a received DATA chunk has no user data.
  1. ——–

New text: (Section 3.3.10.9)

  1. ——–
 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.
  1. ——–

Old text: (Section 6.7, Figure 9)

  1. ——–
 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)

Stewart, et al. Informational [Page 13] RFC 8540 SCTP: Errata and Issues in RFC 4960 February 2019

  1. ——–

New text: (Section 6.7, Figure 9)

  1. ——–
 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.
  1. ——–

Old text: (Section 6.10)

  1. ——–
 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.
  1. ——–

New text: (Section 6.10)

  1. ——–
 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 Path MTU (PMTU).
 This text is in final form and is not further updated in this
 document.

Stewart, et al. Informational [Page 14] RFC 8540 SCTP: Errata and Issues in RFC 4960 February 2019

  1. ——–

Old text: (Section 10.1 O))

  1. ——–
 o  Receive Unacknowledged Message
    Format: RECEIVE_UNACKED(data retrieval id, buffer address, buffer
            size, [,stream id] [, stream sequence number] [,partial
            flag] [,payload protocol-id])
  1. ——–

New text: (Section 10.1 O))

  1. ——–
 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.
  1. ——–

Old text: (Section 10.1 M))

  1. ——–
 M) Set Protocol Parameters
    Format: SETPROTOCOLPARAMETERS(association id,
            [,destination transport address,]
            protocol parameter list)
  1. ——–

New text: (Section 10.1 M))

  1. ——–
 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.

Stewart, et al. Informational [Page 15] RFC 8540 SCTP: Errata and Issues in RFC 4960 February 2019

  1. ——–

Old text: (Appendix C)

  1. ——–
 ICMP2) An implementation MAY ignore all ICMPv6 messages where the
        type field is not "Destination Unreachable", "Parameter
        Problem",, or "Packet Too Big".
  1. ——–

New text: (Appendix C)

  1. ——–
 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.
  1. ——–

Old text: (Appendix C)

  1. ——–
 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.
  1. ——–

New text: (Appendix C)

  1. ——–
 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.
  1. ——–

Old text: (Section 5.4)

  1. ——–
 2)  For the receiver of the COOKIE ECHO, the only CONFIRMED address
    is the one to which the INIT-ACK was sent.

Stewart, et al. Informational [Page 16] RFC 8540 SCTP: Errata and Issues in RFC 4960 February 2019

  1. ——–

New text: (Section 5.4)

  1. ——–
 2)  For the receiver of the COOKIE ECHO, the only CONFIRMED address
     is the address to which the INIT ACK was sent.
 This text is in final form and is not further updated in this
 document.
  1. ——–

Old text: (Section 5.1.6, Figure 4)

  1. ——–
 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)
  1. ——–

New text: (Section 5.1.6, Figure 4)

  1. ——–
 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.
  1. ——–

Old text: (Section 5.2.5)

  1. ——–
 5.2.5.  Handle Duplicate COOKIE-ACK.

Stewart, et al. Informational [Page 17] RFC 8540 SCTP: Errata and Issues in RFC 4960 February 2019

  1. ——–

New text: (Section 5.2.5)

  1. ——–
 5.2.5.  Handle Duplicate COOKIE ACK.
 This text is in final form and is not further updated in this
 document.
  1. ——–

Old text: (Section 8.3)

  1. ——–
 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).
  1. ——–

New text: (Section 8.3)

  1. ——–
 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

 Several typos have been fixed.

Stewart, et al. Informational [Page 18] RFC 8540 SCTP: Errata and Issues in RFC 4960 February 2019

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 appear at
 the end of Appendix C of [RFC4960], which deals with ICMP handling.

3.10.2. Text Changes to the Document

 The text in Appendix C of [RFC4960], starting with the following
 sentence, needs to be moved 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

 The text is 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 selective
 acknowledgment (SACK), but this information is not accounted for in
 the case of T3-rtx timer expiration.

3.11.2. Text Changes to the Document

  1. ——–

Old text: (Section 7.2.3)

  1. ——–
 When the T3-rtx timer expires on an address, SCTP should perform slow
 start by:
 ssthresh = max(cwnd/2, 4*MTU)
 cwnd = 1*MTU

Stewart, et al. Informational [Page 19] RFC 8540 SCTP: Errata and Issues in RFC 4960 February 2019

  1. ——–

New text: (Section 7.2.3)

  1. ——–
 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
 This text is in final form and is not further updated in this
 document.

3.11.3. Solution Description

 The new text specifies 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

  1. ——–

Old text: (Section 7.2.2)

  1. ——–
 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).
  1. ——–

New text: (Section 7.2.2)

  1. ——–
 o  (1) when partial_bytes_acked is equal to or greater than cwnd and
    (2) before the arrival of the SACK the sender had cwnd or more
    bytes of data outstanding (i.e., before the arrival of the SACK,

Stewart, et al. Informational [Page 20] RFC 8540 SCTP: Errata and Issues in RFC 4960 February 2019

    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.

3.13. HEARTBEAT ACK and the Association Error Counter

3.13.1. Description of the Problem

 Sections 8.1 and 8.3 of [RFC4960] prescribe that the receiver of a
 HEARTBEAT ACK must reset the association overall error count.  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

  1. ——–

Old text: (Section 8.1)

  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.
  1. ——–

New text: (Section 8.1)

  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.

Stewart, et al. Informational [Page 21] RFC 8540 SCTP: Errata and Issues in RFC 4960 February 2019

  1. ——–

Old text: (Section 8.3)

  1. ——–
 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).
  1. ——–

New text: (Section 8.3)

  1. ——–
 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 count (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 the possibility of not resetting the
 association overall error count when a HEARTBEAT ACK is received if
 there are valid reasons for not doing so.

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.

Stewart, et al. Informational [Page 22] RFC 8540 SCTP: Errata and Issues in RFC 4960 February 2019

3.14.2. Text Changes to the Document

  1. ——–

Old text: (Section 6.4)

  1. ——–
 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.
  1. ——–

New text: (Section 6.4)

  1. ——–
 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 to which
 the original data was sent.  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) in Section 7.2.4 of [RFC4960] misses this
 clarification.

Stewart, et al. Informational [Page 23] RFC 8540 SCTP: Errata and Issues in RFC 4960 February 2019

3.15.2. Text Changes to the Document

  1. ——–

Old text: (Section 7.2.4)

  1. ——–
 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.
  1. ——–

New text: (Section 7.2.4)

  1. ——–
 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 that only the first packet in the
 Fast Recovery phase be sent and that the cwnd limitations be
 disregarded.

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, a higher
 requirement level needs to be used, since not following the advice
 may result in performance problems.

Stewart, et al. Informational [Page 24] RFC 8540 SCTP: Errata and Issues in RFC 4960 February 2019

3.16.2. Text Changes to the Document

  1. ——–

Old text: (Section 7.2.1)

  1. ——–
 o  The initial value of ssthresh MAY be arbitrarily high (for
    example, implementations MAY use the size of the receiver
    advertised window).
  1. ——–

New text: (Section 7.2.1)

  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

 The same value as the value suggested in [RFC5681], Section 3.1, is
 now used as an appropriate initial value.  Also, the same requirement
 level is used.

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 be
 automatically CONFIRMED.  This, however, is unclear if (1) only
 addresses in the request to initiate association establishment or
 (2) any addresses provided by the upper layer in any requests (e.g.,
 in 'Set Primary') are considered.

3.17.2. Text Changes to the Document

  1. ——–

Old text: (Section 5.4)

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

Stewart, et al. Informational [Page 25] RFC 8540 SCTP: Errata and Issues in RFC 4960 February 2019

  1. ——–

New text: (Section 5.4)

  1. ——–
 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 of [RFC4960] does not
 specify how many packets are allowed to be sent after T3-rtx timer
 expiration if more than one packet fits into cwnd.  At the same time,
 Section 7.2.3 of [RFC4960] has 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
 acknowledgement.  The text is therefore inconsistent.

3.18.2. Text Changes to the Document

  1. ——–

Old text: (Section 7.2.1)

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

New text: (Section 7.2.1)

  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.

Stewart, et al. Informational [Page 26] RFC 8540 SCTP: Errata and Issues in RFC 4960 February 2019

 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 the case of an INIT received in the COOKIE-WAIT state, [RFC4960]
 prescribes that an INIT ACK be sent to the same destination address
 to which the original INIT has been sent.  [RFC4960] does not address
 the possibility of the upper layer providing 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 an INIT ACK to that address is useless.

3.19.2. Text Changes to the Document

  1. ——–

Old text: (Section 5.2.1)

  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.
  1. ——–

New text: (Section 5.2.1)

  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.

Stewart, et al. Informational [Page 27] RFC 8540 SCTP: Errata and Issues in RFC 4960 February 2019

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

3.20.2. Text Changes to the Document

  1. ——–

Old text: (Section 6.1 A))

  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.
  1. ——–

New text: (Section 6.1 A))

  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

Stewart, et al. Informational [Page 28] RFC 8540 SCTP: Errata and Issues in RFC 4960 February 2019

 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 of RFC 4960

3.21.1. Description of the Problem

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

3.21.2. Text Changes to the Document

  1. ——–

Old text: (Section 10.1 E))

  1. ——–
 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.
  1. ——–

New text: (Section 10.1 E))

  1. ——–
 o  no-bundle flag - instructs SCTP not to bundle this user data with
    other outbound DATA chunks.  When faced with network congestion,
    SCTP may still bundle the data, even when this flag is present.
 This text is in final form and is not further updated in this
 document.

Stewart, et al. Informational [Page 29] RFC 8540 SCTP: Errata and Issues in RFC 4960 February 2019

  1. ——–

Old text: (Section 10.1 G))

  1. ——–
 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.
  1. ——–

New text: (Section 10.1 G))

  1. ——–
 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.
 This text is in final form and is not further updated in this
 document.
  1. ——–

Old text: (Section 10.1 N))

  1. ——–
 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.

Stewart, et al. Informational [Page 30] RFC 8540 SCTP: Errata and Issues in RFC 4960 February 2019

  1. ——–

New text: (Section 10.1 N))

  1. ——–
 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.
  1. ——–

Old text: (Section 10.1 O))

  1. ——–
 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.
  1. ——–

New text: (Section 10.1 O))

  1. ——–
 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.

Stewart, et al. Informational [Page 31] RFC 8540 SCTP: Errata and Issues in RFC 4960 February 2019

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 in the text in Section 7.2.2 of
 [RFC4960] regarding partial_bytes_acked handling:
 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 even
    though these TSNs were successfully received by the peer.
 o  Duplicate TSNs are not considered in partial_bytes_acked even
    though they confirm that the DATA chunks were successfully
    received by the peer.

3.22.2. Text Changes to the Document

  1. ——–

Old text: (Section 7.2.2)

  1. ——–
 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.
  1. ——–

New text: (Section 7.2.2)

  1. ——–
 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.

Stewart, et al. Informational [Page 32] RFC 8540 SCTP: Errata and Issues in RFC 4960 February 2019

3.22.3. Solution Description

 In the new text, 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. Inconsistent Handling of Notifications

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.  For
 example, 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;
 however, 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.
 These inconsistent descriptions need to be corrected.

3.23.2. Text Changes to the Document

  1. ——–

Old text: (Section 8.1)

  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.
  1. ——–

New text: (Section 8.1)

  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 that 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 that is currently 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

Stewart, et al. Informational [Page 33] RFC 8540 SCTP: Errata and Issues in RFC 4960 February 2019

 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.
  1. ——–

Old text: (Section 8.2)

  1. ——–
 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.
  1. ——–

New text: (Section 8.2)

  1. ——–
 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 have significant consequences for 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.

Stewart, et al. Informational [Page 34] RFC 8540 SCTP: Errata and Issues in RFC 4960 February 2019

  1. ——–

Old text: (Section 8.3)

  1. ——–
 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.
  1. ——–

New text: (Section 8.3)

  1. ——–
 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 in 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.
  1. ——–

Old text: (Section 8.3)

  1. ——–
 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).
  1. ——–

New text: (Section 8.3)

  1. ——–
 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

Stewart, et al. Informational [Page 35] RFC 8540 SCTP: Errata and Issues in RFC 4960 February 2019

 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 count (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.
  1. ——–

Old text: (Section 9.2)

  1. ——–
 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).
  1. ——–

New text: (Section 9.2)

  1. ——–
 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.
  1. ——–

Old text: (Section 9.2)

  1. ——–
 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).

Stewart, et al. Informational [Page 36] RFC 8540 SCTP: Errata and Issues in RFC 4960 February 2019

  1. ——–

New text: (Section 9.2)

  1. ——–
 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.

3.23.3. Solution Description

 The inconsistencies are removed by consistently using 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, (1) defining a name for
 this parameter and (2) listing it in the table of protocol parameters
 in Section 15 of [RFC4960] are missing.
 This issue was reported as an errata for [RFC4960] with
 Errata ID 4656.

3.24.2. Text Changes to the Document

  1. ——–

Old text: (Section 6.2)

  1. ——–
 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.

Stewart, et al. Informational [Page 37] RFC 8540 SCTP: Errata and Issues in RFC 4960 February 2019

  1. ——–

New text: (Section 6.2)

  1. ——–
 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.
  1. ——–

Old text: (Section 15)

  1. ——–
 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

Stewart, et al. Informational [Page 38] RFC 8540 SCTP: Errata and Issues in RFC 4960 February 2019

  1. ——–

New text: (Section 15)

  1. ——–
 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 is given the name 'SACK.Delay' and added to the list of
 protocol parameters.

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 text specifies that the
 receiver of a packet must discard it while processing the chunks of
 the packet.  Whether or not the receiver has to roll back state
 changes already performed while processing the packet is unclear.
 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 the
 discarding of all further chunks.

Stewart, et al. Informational [Page 39] RFC 8540 SCTP: Errata and Issues in RFC 4960 February 2019

3.25.2. Text Changes to the Document

  1. ——–

Old text: (Section 3.2)

  1. ——–
 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'.
  1. ——–

New text: (Section 3.2)

  1. ——–
 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.
  1. ——–

Old text: (Section 11.3)

  1. ——–
 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.

Stewart, et al. Informational [Page 40] RFC 8540 SCTP: Errata and Issues in RFC 4960 February 2019

  1. ——–

New text: (Section 11.3)

  1. ——–
 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,
 as 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 that no rollback or prescreening is
 required.

3.26. Increasing the cwnd in the Congestion Avoidance Phase

3.26.1. Description of the Problem

 Section 7.2.2 of [RFC4960] prescribes that cwnd be increased 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 of [RFC4960] includes an algorithm that specifies how
 an implementation can achieve 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

  1. ——–

Old text: (Section 7.2.2)

  1. ——–
 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.

Stewart, et al. Informational [Page 41] RFC 8540 SCTP: Errata and Issues in RFC 4960 February 2019

  1. ——–

New text: (Section 7.2.2)

  1. ——–
 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 as
 follows:
 o  SCTP MAY increment cwnd by 1*MTU.
 o  SCTP SHOULD increment cwnd by 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.
  1. ——–

Old text: (Section 7.2.2)

  1. ——–
 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).
  1. ——–

New text: (Section 7.2.2)

  1. ——–
 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.

Stewart, et al. Informational [Page 42] RFC 8540 SCTP: Errata and Issues in RFC 4960 February 2019

 o  (1) when partial_bytes_acked is greater than cwnd and (2) before
    the arrival of the SACK the sender had less than cwnd bytes of
    data outstanding (i.e., before the arrival of the SACK, flightsize
    was less than cwnd), reset partial_bytes_acked to cwnd.
 o  (1) when partial_bytes_acked is equal to or greater than cwnd and
    (2) before the arrival of the SACK the sender had cwnd or more
    bytes of data outstanding (i.e., before the 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 Sections 3.12 and 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].
 The algorithm from Section 7.2.2 is improved and now does 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 that cwnd per RTO be adjusted if the endpoint
 does not transmit data on a given transport address.  In addition to
 that, it prescribes that cwnd be set to the initial value after a
 sufficiently long idle period.  The latter is excessive.  Moreover,
 what is considered a sufficiently long idle period is unclear.
 [RFC4960] doesn't specify the handling of ssthresh in the idle case.
 If ssthresh is reduced due to 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: 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.

Stewart, et al. Informational [Page 43] RFC 8540 SCTP: Errata and Issues in RFC 4960 February 2019

3.27.2. Text Changes to the Document

  1. ——–

Old text: (Section 7.2.1)

  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)).
  1. ——–

New text: (Section 7.2.1)

  1. ——–
 o  The initial cwnd before data transmission MUST be set to
    min(4*MTU, max (2*MTU, 4380 bytes)).
  1. ——–

Old text: (Section 7.2.1)

  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.
  1. ——–

New text: (Section 7.2.1)

  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 handling of ssthresh.  When the
 idle period is detected, the cwnd value is copied to ssthresh.

Stewart, et al. Informational [Page 44] RFC 8540 SCTP: Errata and Issues in RFC 4960 February 2019

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 Section 6.2 of [RFC4960], which states that an SCTP
 receiver must not generate more than one SACK for every incoming
 packet, other than to update the offered window.
 However, to avoid performance problems, it is necessary to send the
 window updates when the receiver window opens up.

3.28.2. Text Changes to the Document

  1. ——–

Old text: (Section 6.2)

  1. ——–
 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.
  1. ——–

New text: (Section 6.2)

  1. ——–
 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 it clear that additional SACK chunks for window
 updates should be sent as long as excessive bursts are avoided.

Stewart, et al. Informational [Page 45] RFC 8540 SCTP: Errata and Issues in RFC 4960 February 2019

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, this policy has the following
 issues:
 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., always sending SACKs to the primary path) may be more
    beneficial in some situations.
 o  Also, it initially states that an endpoint should always transmit
    DATA chunks to the primary path but then states that the rule for
    the transmittal of reply chunks should also be followed if the
    endpoint is bundling DATA chunks together with the reply chunk.
    The second statement contradicts the first statement.  Some
    implementations were having problems with it and sent DATA chunks
    bundled with reply chunks to a different destination address than
    the primary path, causing many gaps.

3.29.2. Text Changes to the Document

  1. ——–

Old text: (Section 6.4)

  1. ——–
 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.
  1. ——–

New text: (Section 6.4)

  1. ——–
 An endpoint SHOULD transmit reply chunks (e.g., INIT ACK, COOKIE ACK,
 HEARTBEAT ACK) in response to control chunks to the same destination
 transport address from which it received the control chunk to which
 it is replying.

Stewart, et al. Informational [Page 46] RFC 8540 SCTP: Errata and Issues in RFC 4960 February 2019

 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.

3.29.3. Solution Description

 The SACK transmission policy is left implementation dependent, but
 the new text now specifies that the policy not vary the destination
 address of a packet containing a SACK chunk unless there are reasons
 for not doing so, as varying the destination address may negatively
 impact RTT measurement.
 New text removes a confusing statement that prescribes following the
 rule for transmittal of reply chunks when the endpoint is bundling
 DATA chunks together with the reply chunk.

3.30. "Outstanding Data", "Flightsize", and "Data in Flight" Key Terms

3.30.1. Description of the Problem

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

3.30.2. Text Changes to the Document

  1. ——–

Old text: (Section 1.3)

  1. ——–
 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.
 ...

Stewart, et al. Informational [Page 47] RFC 8540 SCTP: Errata and Issues in RFC 4960 February 2019

 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.
  1. ——–

New text: (Section 1.3)

  1. ——–
 o  Congestion window (cwnd): An SCTP variable that limits outstanding
    data, in number of bytes, that a sender can send to a particular
    destination transport address before receiving an acknowledgement.
 ...
 o  Flightsize: The amount of bytes of outstanding data to a
    particular destination transport address at any given time.
 ...
 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 that is classified as lost but that has not yet been
    retransmitted is not in outstanding data.
 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.
 This text is in final form and is not further updated in this
 document.
  1. ——–

Old text: (Section 6.1)

  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).
  1. ——–

New text: (Section 6.1)

  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).

Stewart, et al. Informational [Page 48] RFC 8540 SCTP: Errata and Issues in RFC 4960 February 2019

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

3.30.3. Solution Description

 Section 1.3 is corrected to include explanations of the key terms
 "outstanding data", "data in flight", and "flightsize".  Section 6.1
 is corrected to now use "any DATA chunks" instead of "any outstanding
 DATA chunks".

3.31. Degradation of cwnd 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 Section 6.1 of [RFC4960] regarding how to use the
 Max.Burst parameter when calculating the number of packets to
 transmit.

3.31.2. Text Changes to the Document

  1. ——–

Old text: (Section 6.1)

  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.
  1. ——–

New text: (Section 6.1)

  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

Stewart, et al. Informational [Page 49] RFC 8540 SCTP: Errata and Issues in RFC 4960 February 2019

    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 when 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

3.32.1. Description of the Problem

 [RFC4960] uses 3 seconds as the default value for RTO.Initial in
 accordance with Section 4.2.3.1 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

  1. ——–

Old text: (Section 15)

  1. ——–
 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

Stewart, et al. Informational [Page 50] RFC 8540 SCTP: Errata and Issues in RFC 4960 February 2019

  1. ——–

New text: (Section 15)

  1. ——–
 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
 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 default value for 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, in the case of
 bundling, [RFC4960] requires that the ERROR chunk follow the SACK
 chunk.  This restriction regarding the ordering of the chunks is not
 necessary and might limit interoperability.

Stewart, et al. Informational [Page 51] RFC 8540 SCTP: Errata and Issues in RFC 4960 February 2019

3.33.2. Text Changes to the Document

  1. ——–

Old text: (Section 6.5)

  1. ——–
 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.
  1. ——–

New text: (Section 6.5)

  1. ——–
 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.
 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 chunks 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.

Stewart, et al. Informational [Page 52] RFC 8540 SCTP: Errata and Issues in RFC 4960 February 2019

3.34.2. Text Changes to the Document

  1. ——–

Old text: (Section 10.1 G))

  1. ——–
 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]
  1. ——–

New text: (Section 10.1 G))

  1. ——–
 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.

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.  Changing the DSCP can result in
 packets hitting different queues on the path.  Therefore, congestion
 control should be initialized when the DSCP is changed by the upper
 layer.  This is not described in [RFC4960].

Stewart, et al. Informational [Page 53] RFC 8540 SCTP: Errata and Issues in RFC 4960 February 2019

3.35.2. Text Changes to the Document

  1. ——–

New text: (Section 7.2.5)

  1. ——–
 7.2.5.  Making Changes to 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.
  1. ——–

Old text: (Section 10.1 M))

  1. ——–
 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.
  1. ——–

New text: (Section 10.1 M))

  1. ——–
 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.

Stewart, et al. Informational [Page 54] RFC 8540 SCTP: Errata and Issues in RFC 4960 February 2019

3.35.3. Solution Description

 Text describing the required action for 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, as described in the enumerated procedures, is
 not consistent with the description given in [RFC4960] after the
 procedures.  Furthermore, the text explicitly describes the handling
 of ICMPv6 packets indicating reachability problems but does not do
 the same for the corresponding ICMPv4 packets.

3.36.2. Text Changes to the Document

  1. ——–

Old text: (Appendix C)

  1. ——–
 ICMP3) An implementation MAY ignore any ICMPv4 messages where the
        code does not indicate "Protocol Unreachable" or
        "Fragmentation Needed".
  1. ——–

New text: (Appendix C)

  1. ——–
 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.
  1. ——–

Old text: (Appendix C)

  1. ——–
 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.

Stewart, et al. Informational [Page 55] RFC 8540 SCTP: Errata and Issues in RFC 4960 February 2019

  1. ——–

New text: (Appendix C)

  1. ——–
 ICMP9) If the ICMP type is "Destination Unreachable", the
        implementation MAY move the destination to 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.  Also, the limitation to ICMPv6 in the ninth rule has
 been removed.

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

  1. ——–

Old text: (Appendix C)

  1. ——–
 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.
  1. ——–

New text: (Appendix C)

  1. ——–
 ICMP9) If the ICMP type is "Destination Unreachable", the
        implementation MAY move the destination to 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.

Stewart, et al. Informational [Page 56] RFC 8540 SCTP: Errata and Issues in RFC 4960 February 2019

 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 the
 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 be allowed.

3.38.2. Text Changes to the Document

  1. ——–

Old text: (Section 6.1)

  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.
  1. ——–

New text: (Section 6.1)

  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.

Stewart, et al. Informational [Page 57] RFC 8540 SCTP: Errata and Issues in RFC 4960 February 2019

  1. ——–

Old text: (Section 7.2.1)

  1. ——–
 o  Whenever cwnd is greater than zero, the endpoint is allowed to
    have cwnd bytes of data outstanding on that transport address.
  1. ——–

New text: (Section 7.2.1)

  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 Section 6.1 B) 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.

3.39. Zero Window Probing

3.39.1. Description of the Problem

 The text in Section 6.1 of [RFC4960] that describes zero window
 probing does not clearly address the case where the window is not
 zero but is too small for the next DATA chunk to be transmitted.
 Even in this case, zero window probing has to be performed to avoid
 deadlocks.

Stewart, et al. Informational [Page 58] RFC 8540 SCTP: Errata and Issues in RFC 4960 February 2019

3.39.2. Text Changes to the Document

  1. ——–

Old text: (Section 6.1)

  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.
  1. ——–

New text: (Section 6.1)

  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.

Stewart, et al. Informational [Page 59] RFC 8540 SCTP: Errata and Issues in RFC 4960 February 2019

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

 For Explicit Congestion Notification (ECN), [RFC4960] refers only to
 [RFC3168], which has been updated by [RFC8311].  This needs to be
 reflected in the text when referring to ECN.

3.40.2. Text Changes to the Document

  1. ——–

Old text: (Appendix A)

  1. ——–
 ECN [RFC3168] describes a proposed extension to IP that details a
 method to become aware of congestion outside of datagram loss.
  1. ——–

New text: (Appendix A)

  1. ——–
 ECN as specified in [RFC3168] (updated by [RFC8311]) describes an
 extension to IP that details a method for becoming aware of
 congestion outside of datagram loss.
 This text is in final form and is not further updated in this
 document.
  1. ——–

Old text: (Appendix A)

  1. ——–
 In general, [RFC3168] should be followed with the following
 exceptions.
  1. ——–

New text: (Appendix A)

  1. ——–
 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.

Stewart, et al. Informational [Page 60] RFC 8540 SCTP: Errata and Issues in RFC 4960 February 2019

  1. ——–

Old text: (Appendix A)

  1. ——–
 [RFC3168] details negotiation of ECN during the SYN and SYN-ACK
 stages of a TCP connection.
  1. ——–

New text: (Appendix A)

  1. ——–
 [RFC3168] (updated by [RFC8311]) details the 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.
  1. ——–

Old text: (Appendix A)

  1. ——–
 [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.
  1. ——–

New text: (Appendix A)

  1. ——–
 [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 that the CE bit has
 arrived from the network.
 This text is in final form and is not further updated in this
 document.
  1. ——–

Old text: (Appendix A)

  1. ——–
 [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.

Stewart, et al. Informational [Page 61] RFC 8540 SCTP: Errata and Issues in RFC 4960 February 2019

  1. ——–

New text: (Appendix A)

  1. ——–
 [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.  Some wordsmithing was also
 done while making those updates.

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

3.41.2. Text Changes to the Document

  1. ——–

Old text: (Section 3.3.2)

  1. ——–
 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.

Stewart, et al. Informational [Page 62] RFC 8540 SCTP: Errata and Issues in RFC 4960 February 2019

  1. ——–

New text: (Section 3.3.2)

  1. ——–
 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 "Unresolvable
 Address" error cause.
 This text is in final form and is not further updated in this
 document.
  1. ——–

Old text: (Section 3.3.2.1)

  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.
  1. ——–

New text: (Section 3.3.2.1)

  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.
  1. ——–

Old text: (Section 3.3.2.1)

  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).

Stewart, et al. Informational [Page 63] RFC 8540 SCTP: Errata and Issues in RFC 4960 February 2019

  1. ——–

New text: (Section 3.3.2.1)

  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.
  1. ——–

Old text: (Section 3.3.3)

  1. ——–
 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.
  1. ——–

New text: (Section 3.3.3)

  1. ——–
 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 "Unresolvable
 Address" error cause.
 This text is in final form and is not further updated in this
 document.
  1. ——–

Old text: (Section 5.1.2)

  1. ——–
 B) If there is a Host Name parameter present in the received INIT or
    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.

Stewart, et al. Informational [Page 64] RFC 8540 SCTP: Errata and Issues in RFC 4960 February 2019

    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.
  1. ——–

New text: (Section 5.1.2)

  1. ——–
 B) If there is a Host Name Address parameter present in the received
    INIT or INIT ACK chunk, the endpoint MUST immediately send an
    ABORT and MAY include an "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.
 This text is in final form and is not further updated in this
 document.

Stewart, et al. Informational [Page 65] RFC 8540 SCTP: Errata and Issues in RFC 4960 February 2019

  1. ——–

Old text: (Section 11.2.4.1)

  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.
  1. ——–

New text: (Section 11.2.4.1)

  1. ——–
 Support for 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 "Unresolvable Address" error cause.
 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

 Section 5.1.2 of [RFC4960] contains conflicting text regarding the
 receipt of 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' parameter.  The text states that the
 association MUST be aborted, but it also states that the association
 SHOULD be established and there SHOULD NOT be any error indication.

Stewart, et al. Informational [Page 66] RFC 8540 SCTP: Errata and Issues in RFC 4960 February 2019

3.42.2. Text Changes to the Document

  1. ——–

Old text: (Section 5.1.2)

  1. ——–
 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.
  1. ——–

New text: (Section 5.1.2)

  1. ——–
 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 the "Chunk Flags" registry.
 This should be integrated into the base specification.

Stewart, et al. Informational [Page 67] RFC 8540 SCTP: Errata and Issues in RFC 4960 February 2019

3.43.2. Text Changes to the Document

  1. ——–

Old text: (Section 14.1)

  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:
    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.
  1. ——–

New text: (Section 14.1)

  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 for 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.
    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.

Stewart, et al. Informational [Page 68] RFC 8540 SCTP: Errata and Issues in RFC 4960 February 2019

    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 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.
  1. ——–

New text: (Section 14.2)

  1. ——–
 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 for 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 as shown in
 [RFC4960] will need to be renumbered when [RFC4960] is updated.

3.43.3. Solution Description

 [RFC6096] has been integrated, and the reference has been updated to
 [RFC8126].

Stewart, et al. Informational [Page 69] RFC 8540 SCTP: Errata and Issues in RFC 4960 February 2019

3.44. Integration of RFC 6335

3.44.1. Description of the Problem

 [RFC6335] updates [RFC4960] by updating procedures for the "Service
 Name and Transport Protocol Port Number Registry".  This should be
 integrated into the base specification.  Also, the "Guidelines for
 Writing an IANA Considerations Section in RFCs" reference needs to be
 changed to [RFC8126].

3.44.2. Text Changes to the Document

  1. ——–

Old text: (Section 14.5)

  1. ——–
 SCTP services may 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 [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.

Stewart, et al. Informational [Page 70] RFC 8540 SCTP: Errata and Issues in RFC 4960 February 2019

 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
    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.
  1. ——–

New text: (Section 14.5)

  1. ——–
 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 "Service Name and Transport Protocol Port Number
 Registry" for SCTP using the following rules, which we intend to mesh
 well with existing port-number 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.

Stewart, et al. Informational [Page 71] RFC 8540 SCTP: Errata and Issues in RFC 4960 February 2019

3.44.3. Solution Description

 [RFC6335] has been integrated, and the reference has been 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

  1. ——–

Old text: (Section 3.3.1)

  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
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |   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.

Stewart, et al. Informational [Page 72] RFC 8540 SCTP: Errata and Issues in RFC 4960 February 2019

  1. ——–

New text: (Section 3.3.1)

  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
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |   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 Section 4 of [RFC7053] for a
    discussion of the benefits.
 This text is in final form and is not further updated in this
 document.

Stewart, et al. Informational [Page 73] RFC 8540 SCTP: Errata and Issues in RFC 4960 February 2019

  1. ——–

New text: (Append to Section 6.1)

  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, the
 following (see Section 4 of [RFC7053] for a discussion of the
 benefits):
 o  The application requests that the I bit of the last DATA chunk of
    a user message be set 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.
  1. ——–

Old text: (Section 6.2)

  1. ——–
 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.
  1. ——–

New text: (Section 6.2)

  1. ——–
 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.
 Please note that this change is only about adding a paragraph.

Stewart, et al. Informational [Page 74] RFC 8540 SCTP: Errata and Issues in RFC 4960 February 2019

 This text is in final form and is not further updated in this
 document.
  1. ——–

Old text: (Section 10.1 E))

  1. ——–
 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
  1. ——–

New text: (Section 10.1 E))

  1. ——–
 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.
  1. ——–

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

  1. ——–
 o  sack-immediately flag - set the I bit on the last DATA chunk used
    for the user message to be transmitted.
 This text is in final form and is not further updated in this
 document.

3.45.3. Solution Description

 [RFC7053] has been integrated.

Stewart, et al. Informational [Page 75] RFC 8540 SCTP: Errata and Issues in RFC 4960 February 2019

3.46. CRC32c Code Improvements

3.46.1. Description of the Problem

 The code given for the CRC32c computations uses types such as "long",
 which may have different lengths on different operating systems or
 processors.  Therefore, the code needs to be changed, so that it uses
 specific types such as uint32_t.
 Some syntax errors and a comment also need to be fixed.
 We remind the reader that per Section 3.10.2 of this document most of
 Appendix C of RFC 4960 will be moved to Appendix B in the bis
 document (thus the "Old text: (Appendix C)" and "New text:
 (Appendix B)" items in this section).

Stewart, et al. Informational [Page 76] RFC 8540 SCTP: Errata and Issues in RFC 4960 February 2019

3.46.2. Text Changes to the Document

  1. ——–

Old text: (Appendix C)

  1. ——–
 /*************************************************************/
 /* 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,
 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,

Stewart, et al. Informational [Page 77] RFC 8540 SCTP: Errata and Issues in RFC 4960 February 2019

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

Stewart, et al. Informational [Page 78] RFC 8540 SCTP: Errata and Issues in RFC 4960 February 2019

  1. ——–

New text: (Appendix B)

  1. ——–
 <CODE BEGINS>
 /****************************************************************/
 /* Note: The definitions for Ross Williams's table generator    */
 /* would be TB_WIDTH=4, TB_POLY=0x1EDC6F41, TB_REVER=TRUE.      */
 /* For Mr. Williams's direct calculation code, use the settings */
 /* cm_width=32, cm_poly=0x1EDC6F41, cm_init=0xFFFFFFFF,         */
 /* cm_refin=TRUE, cm_refot=TRUE, cm_xorot=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,
 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,

Stewart, et al. Informational [Page 79] RFC 8540 SCTP: Errata and Issues in RFC 4960 February 2019

 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
 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.

Stewart, et al. Informational [Page 80] RFC 8540 SCTP: Errata and Issues in RFC 4960 February 2019

  1. ——–

Old text: (Appendix C)

  1. ——–
 /* 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));
 }
 main ()
 {
   int i;

Stewart, et al. Informational [Page 81] RFC 8540 SCTP: Errata and Issues in RFC 4960 February 2019

   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);
 }
  1. ——–

New text: (Appendix B)

  1. ——–
 /* 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)
 {
   int i;
   uint32_t rw = 0UL;
   for (i = 0; i < 32; i++) {

Stewart, et al. Informational [Page 82] RFC 8540 SCTP: Errata and Issues in RFC 4960 February 2019

       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 CRC32c 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));
       if ((i & 3) == 3)

Stewart, et al. Informational [Page 83] RFC 8540 SCTP: Errata and Issues in RFC 4960 February 2019

         fprintf(tf, "\n");
       else
         fprintf(tf, " ");
   }
   fprintf(tf, "};\n\n#endif\n");
   if (fclose(tf) != 0)
     printf("Unable to close <%s>.\n", OUTPUT_FILE);
   else
     printf("\nThe CRC32c 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.
  1. ——–

Old text: (Appendix C)

  1. ——–
 /* 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.
    *  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,

Stewart, et al. Informational [Page 84] RFC 8540 SCTP: Errata and Issues in RFC 4960 February 2019

  • 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);
 }

Stewart, et al. Informational [Page 85] RFC 8540 SCTP: Errata and Issues in RFC 4960 February 2019

  1. ——–

New text: (Appendix B)

  1. ——–
 /* 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 are "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, and then did an
    *  end-for-end bit-reversal.
    *  Note that a 32-bit bit-reversal is identical to four in-place
    *  8-bit 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

Stewart, et al. Informational [Page 86] RFC 8540 SCTP: Errata and Issues in RFC 4960 February 2019

 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 Sections 3.5 and 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.

Stewart, et al. Informational [Page 87] RFC 8540 SCTP: Errata and Issues in RFC 4960 February 2019

3.47.2. Text Changes to the Document

  1. ——–

Old text: (Section 3.3.4)

  1. ——–
 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.
  1. ——–

New text: (Section 3.3.4)

  1. ——–
 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 have 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.
  1. ——–

Old text: (Section 3.3.4)

  1. ——–
 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.

Stewart, et al. Informational [Page 88] RFC 8540 SCTP: Errata and Issues in RFC 4960 February 2019

  1. ——–

New text: (Section 3.3.4)

  1. ——–
 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.  This means that
    the DATA chunks with TSNs 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 Wraparounds

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 wraparounds of the SSN might happen
 within the current send window.  To allow the receiver to deliver
 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

  1. ——–

Old text: (Section 6.1)

  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.

Stewart, et al. Informational [Page 89] RFC 8540 SCTP: Errata and Issues in RFC 4960 February 2019

  1. ——–

New text: (Section 6.1)

  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 to RFC 2119 Boilerplate Text

3.49.1. Description of the Problem

 The text to be used to refer to the terms ("key words") defined in
 [RFC2119] has been updated by [RFC8174].  This needs to be integrated
 into the base specification.

3.49.2. Text Changes to the Document

  1. ——–

Old text: (Section 2)

  1. ——–
 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].
  1. ——–

New text: (Section 2)

  1. ——–
 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.

Stewart, et al. Informational [Page 90] RFC 8540 SCTP: Errata and Issues in RFC 4960 February 2019

3.49.3. Solution Description

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

3.50. Removal of Text (Previously Missed in RFC 4960)

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

  1. ——–

Old text: (Section 7.2.4)

  1. ——–
 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.
  1. ——–

New text: (Section 7.2.4)

  1. ——–
 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 suggests new text that would update the
 "Service Name and Transport Protocol Port Number Registry" for SCTP
 to be consistent with [RFC6335].
 IANA has confirmed that it is OK to make the proposed text change in
 an upcoming Standards Track document that will update [RFC4960].
 IANA is not asked to perform any other action, and this document does
 not request that IANA make a change to any registry.

Stewart, et al. Informational [Page 91] RFC 8540 SCTP: Errata and Issues in RFC 4960 February 2019

5. Security Considerations

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

6. References

6.1. 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>.
 [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>.

6.2. 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>.

Stewart, et al. Informational [Page 92] RFC 8540 SCTP: Errata and Issues in RFC 4960 February 2019

 [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>.
 [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>.
 [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>.

Stewart, et al. Informational [Page 93] RFC 8540 SCTP: Errata and Issues in RFC 4960 February 2019

Acknowledgements

 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.

Authors' Addresses

 Randall R. Stewart
 Netflix, Inc.
 Chapin, SC  29036
 United States of America
 Email: randall@lakerest.net
 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

Stewart, et al. Informational [Page 94]

/data/webs/external/dokuwiki/data/pages/rfc/rfc8540.txt · Last modified: 2019/02/20 06:54 by 127.0.0.1

Donate Powered by PHP Valid HTML5 Valid CSS Driven by DokuWiki