draft-ietf-tsvwg-sctp-failover-15.txt   draft-ietf-tsvwg-sctp-failover-16.txt 
Network Working Group Y. Nishida Network Working Group Y. Nishida
Internet-Draft GE Global Research Internet-Draft GE Global Research
Intended status: Standards Track P. Natarajan Intended status: Standards Track P. Natarajan
Expires: July 28, 2016 Cisco Systems Expires: August 20, 2016 Cisco Systems
A. Caro A. Caro
BBN Technologies BBN Technologies
P. Amer P. Amer
University of Delaware University of Delaware
K. Nielsen K. Nielsen
Ericsson Ericsson
January 25, 2016 February 17, 2016
SCTP-PF: Quick Failover Algorithm in SCTP SCTP-PF: Quick Failover Algorithm in SCTP
draft-ietf-tsvwg-sctp-failover-15.txt draft-ietf-tsvwg-sctp-failover-16.txt
Abstract Abstract
SCTP supports multi-homing. However, when the failover operation SCTP supports multi-homing. However, when the failover operation
specified in RFC4960 is followed, there can be significant delay and specified in RFC4960 is followed, there can be significant delay and
performance degradation in the data transfer path failover. To performance degradation in the data transfer path failover. To
overcome this problem this document specifies a quick failover overcome this problem this document specifies a quick failover
algorithm (SCTP-PF) based on the introduction of a Potentially Failed algorithm (SCTP-PF) based on the introduction of a Potentially Failed
(PF) state in SCTP Path Management. (PF) state in SCTP Path Management.
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Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/. Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on July 28, 2016. This Internet-Draft will expire on August 20, 2016.
Copyright Notice Copyright Notice
Copyright (c) 2016 IETF Trust and the persons identified as the Copyright (c) 2016 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of (http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents publication of this document. Please review these documents
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Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Conventions and Terminology . . . . . . . . . . . . . . . . . 4 2. Conventions and Terminology . . . . . . . . . . . . . . . . . 4
3. SCTP with Potentially Failed Destination State (SCTP-PF) . . 4 3. SCTP with Potentially Failed Destination State (SCTP-PF) . . 4
3.1. Overview . . . . . . . . . . . . . . . . . . . . . . . . 4 3.1. Overview . . . . . . . . . . . . . . . . . . . . . . . . 4
3.2. Specification of the SCTP-PF Procedures . . . . . . . . . 5 3.2. Specification of the SCTP-PF Procedures . . . . . . . . . 5
4. Dormant State Operation . . . . . . . . . . . . . . . . . . . 9 4. Dormant State Operation . . . . . . . . . . . . . . . . . . . 9
4.1. SCTP Dormant State Procedure . . . . . . . . . . . . . . 10 4.1. SCTP Dormant State Procedure . . . . . . . . . . . . . . 10
5. Primary Path Switchover . . . . . . . . . . . . . . . . . . . 10 5. Primary Path Switchover . . . . . . . . . . . . . . . . . . . 11
6. Suggested SCTP Protocol Parameter Values . . . . . . . . . . 12 6. Suggested SCTP Protocol Parameter Values . . . . . . . . . . 12
7. Socket API Considerations . . . . . . . . . . . . . . . . . . 12 7. Socket API Considerations . . . . . . . . . . . . . . . . . . 12
7.1. Support for the Potentially Failed Path State . . . . . . 13 7.1. Support for the Potentially Failed Path State . . . . . . 13
7.2. Peer Address Thresholds (SCTP_PEER_ADDR_THLDS) Socket 7.2. Peer Address Thresholds (SCTP_PEER_ADDR_THLDS) Socket
Option . . . . . . . . . . . . . . . . . . . . . . . . . 14 Option . . . . . . . . . . . . . . . . . . . . . . . . . 14
7.3. Exposing the Potentially Failed Path State 7.3. Exposing the Potentially Failed Path State
(SCTP_EXPOSE_POTENTIALLY_FAILED_STATE) Socket Option . . 15 (SCTP_EXPOSE_POTENTIALLY_FAILED_STATE) Socket Option . . 15
8. Security Considerations . . . . . . . . . . . . . . . . . . . 15 8. Security Considerations . . . . . . . . . . . . . . . . . . . 15
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 16 9. MIB Considerations . . . . . . . . . . . . . . . . . . . . . 16
10. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 16 10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 16
11. Proposed Change of Status (to be Deleted before Publication) 16 11. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 16
12. References . . . . . . . . . . . . . . . . . . . . . . . . . 17 12. Proposed Change of Status (to be Deleted before Publication) 17
12.1. Normative References . . . . . . . . . . . . . . . . . . 17 13. References . . . . . . . . . . . . . . . . . . . . . . . . . 17
12.2. Informative References . . . . . . . . . . . . . . . . . 17 13.1. Normative References . . . . . . . . . . . . . . . . . . 17
13.2. Informative References . . . . . . . . . . . . . . . . . 17
Appendix A. Discussions of Alternative Approaches . . . . . . . 18 Appendix A. Discussions of Alternative Approaches . . . . . . . 18
A.1. Reduce Path.Max.Retrans (PMR) . . . . . . . . . . . . . . 18 A.1. Reduce Path.Max.Retrans (PMR) . . . . . . . . . . . . . . 18
A.2. Adjust RTO related parameters . . . . . . . . . . . . . . 19 A.2. Adjust RTO related parameters . . . . . . . . . . . . . . 19
Appendix B. Discussions for Path Bouncing Effect . . . . . . . . 19 Appendix B. Discussions for Path Bouncing Effect . . . . . . . . 20
Appendix C. SCTP-PF for SCTP Single-homed Operation . . . . . . 20 Appendix C. SCTP-PF for SCTP Single-homed Operation . . . . . . 20
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 20 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 21
1. Introduction 1. Introduction
The Stream Control Transmission Protocol (SCTP) specified in The Stream Control Transmission Protocol (SCTP) specified in
[RFC4960] supports multi-homing at the transport layer. SCTP's [RFC4960] supports multi-homing at the transport layer. SCTP's
multi-homing features include failure detection and failover multi-homing features include failure detection and failover
procedures to provide network interface redundancy and improved end- procedures to provide network interface redundancy and improved end-
to-end fault tolerance. In SCTP's current failure detection to-end fault tolerance. In SCTP's current failure detection
procedure, the sender must experience Path.Max.Retrans (PMR) number procedure, the sender must experience Path.Max.Retrans (PMR) number
of consecutive failed timer-based retransmissions on a destination of consecutive failed timer-based retransmissions on a destination
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3.2. Specification of the SCTP-PF Procedures 3.2. Specification of the SCTP-PF Procedures
The SCTP-PF operation is specified as follows: The SCTP-PF operation is specified as follows:
1. The sender maintains a new tunable SCTP Protocol Parameter 1. The sender maintains a new tunable SCTP Protocol Parameter
called PotentiallyFailed.Max.Retrans (PFMR). The PFMR defines called PotentiallyFailed.Max.Retrans (PFMR). The PFMR defines
the new intermediate PF threshold on the destination address the new intermediate PF threshold on the destination address
error counter. When this threshold is exceeded the destination error counter. When this threshold is exceeded the destination
address is classified as PF. The RECOMMENDED value of PFMR is address is classified as PF. The RECOMMENDED value of PFMR is
0, but other values MAY be used. If PFMR is set to be greater 0. If PFMR is set to be greater than or equal to
than or equal to Path.Max.Retrans (PMR), the resulting PF Path.Max.Retrans (PMR), the resulting PF threshold will be so
threshold will be so high that the destination address will high that the destination address will reach the inactive state
reach the inactive state before it can be classified as PF. before it can be classified as PF.
2. The error counter of an active destination address is 2. The error counter of an active destination address is
incremented as specified in [RFC4960]. This means that the incremented or cleared as specified in [RFC4960]. This means
error counter of the destination address will be incremented that the error counter of the destination address in active
each time the T3-rtx timer expires, or each time a HEARTBEAT state will be incremented each time the T3-rtx timer expires, or
chunk is sent when idle and not acknowledged within an RTO. each time a HEARTBEAT chunk is sent when idle and not
When the value in the destination address error counter exceeds acknowledged within an RTO. When the value in the destination
PFMR, the endpoint MUST mark the destination address as in the address error counter exceeds PFMR, the endpoint MUST mark the
PF state. destination address as in the PF state.
3. A SCTP-PF sender SHOULD NOT send data to destination addresses 3. A SCTP-PF sender SHOULD NOT send data to destination addresses
in PF state when alternative destination addresses in active in PF state when alternative destination addresses in active
state are available. Specifically this means that: state are available. Specifically this means that:
i When there is outbound data to send and the destination i When there is outbound data to send and the destination
address presently used for data transmission is in PF state, address presently used for data transmission is in PF state,
the sender SHOULD choose a destination address in active the sender SHOULD choose a destination address in active
state, if one exists, and use this destination address for state, if one exists, and use this destination address for
data transmission. data transmission.
ii When retransmitting data that has timed out and the sender ii As specified in [RFC4960] section 6.4.1, when the sender
thus by [RFC4960], section 6.4.1, should attempt to pick a retransmits data that has timed out, it should attempt to
new destination address for data retransmission, the sender pick a new destination address for data retransmission. In
SHOULD choose an alternate destination transport address in this case, the sender SHOULD choose an alternate destination
active state if one exists. transport address in active state if one exists.
iii When there is outbound data to send and the SCTP user iii When there is outbound data to send and the SCTP user
explicitly requests to send data to a destination address in explicitly requests to send data to a destination address in
PF state, the sender SHOULD send the data to an alternate PF state, the sender SHOULD send the data to an alternate
destination address in active state if one exists. destination address in active state if one exists.
When choosing among multiple destination addresses in active When choosing among multiple destination addresses in active
state an SCTP sender will follow the guiding principles of state an SCTP sender will follow the guiding principles of
section 6.4.1 of [RFC4960] of choosing most divergent source- section 6.4.1 of [RFC4960] of choosing most divergent source-
destination pairs compared with, for i.: the destination address destination pairs compared with, for i.: the destination address
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document. document.
In all cases, the sender MUST NOT change the state of chosen In all cases, the sender MUST NOT change the state of chosen
destination address, whether this state be active or PF, and it destination address, whether this state be active or PF, and it
MUST NOT clear the error counter of the destination address as a MUST NOT clear the error counter of the destination address as a
result of choosing the destination address for data result of choosing the destination address for data
transmission. transmission.
4. When the destination addresses are all in PF state or some in PF 4. When the destination addresses are all in PF state or some in PF
state and some in inactive state, the sender MUST choose one state and some in inactive state, the sender MUST choose one
destination address in PF state and transmit or retransmit data destination address in PF state and SHOULD transmit or
to this destination address using the following rules: retransmit data to this destination address using the following
rules:
A. The sender SHOULD choose the destination in PF state with A. The sender SHOULD choose the destination in PF state with
the lowest error count (fewest consecutive timeouts) for the lowest error count (fewest consecutive timeouts) for
data transmission and transmit or retransmit data to this data transmission and transmit or retransmit data to this
destination. destination.
B. When there are multiple destination addresses in PF state B. When there are multiple destination addresses in PF state
with same error count, the sender should let the choice with same error count, the sender should let the choice
among the multiple destination addresses in PF state with among the multiple destination addresses in PF state with
equal error count be based on the [RFC4960], section 6.4.1, equal error count be based on the [RFC4960], section 6.4.1,
principles of choosing most divergent source-destination principles of choosing most divergent source-destination
pairs when executing (potentially consecutive) pairs when executing (potentially consecutive)
retransmission. Rules for picking the most divergent retransmission. Rules for picking the most divergent
source-destination pair are an implementation decision and source-destination pair are an implementation decision and
are not specified within this document. are not specified within this document.
The sender MUST NOT change the state and the error counter of The sender MUST NOT change the state and the error counter of
any destination address regardless of whether it has been chosen any destination addresses as the result of the selection.
for transmission or not.
5. The HB.interval of the Path Heartbeat function of [RFC4960] MUST 5. The HB.interval of the Path Heartbeat function of [RFC4960] MUST
be ignored for destination addresses in PF state. Instead be ignored for destination addresses in PF state. Instead
HEARTBEAT chunks are sent to destination addresses in PF state HEARTBEAT chunks are sent to destination addresses in PF state
once per RTO. HEARTBEAT chunks SHOULD be sent to destination once per RTO. HEARTBEAT chunks SHOULD be sent to destination
addresses in PF state, but the sending of HEARTBEATS MUST honor addresses in PF state, but the sending of HEARTBEATS MUST honor
whether the Path Heartbeat function (Section 8.3 of [RFC4960]) whether the Path Heartbeat function (Section 8.3 of [RFC4960])
is enabled for the destination address or not. I.e., if the is enabled for the destination address or not. I.e., if the
Path Heartbeat function is disabled for the destination address Path Heartbeat function is disabled for the destination address
in question, HEARTBEATS MUST NOT be sent. Note that when in question, HEARTBEATS MUST NOT be sent. Note that when
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MAY be omitted in case where the receipt of a SACK of the data MAY be omitted in case where the receipt of a SACK of the data
or a T3-rtx timer expiration on the data can provide equivalent or a T3-rtx timer expiration on the data can provide equivalent
information, such as the case where the data chunk has been information, such as the case where the data chunk has been
transmitted to a single destination address only. Likewise, the transmitted to a single destination address only. Likewise, the
timeout of a HEARTBEAT chunk MAY be ignored if data is timeout of a HEARTBEAT chunk MAY be ignored if data is
outstanding towards the destination address. outstanding towards the destination address.
7. When the sender receives a HEARTBEAT ACK from a HEARTBEAT sent 7. When the sender receives a HEARTBEAT ACK from a HEARTBEAT sent
to a destination address in PF state, the sender SHOULD clear to a destination address in PF state, the sender SHOULD clear
the error counter of the destination address and transition the the error counter of the destination address and transition the
destination address back to active state. When the sender destination address back to active state. However, there may be
resumes data transmission on a destination address after a a situation where HEARTBEAT chunks can go through while DATA
transition of the destination address from PF to active state, chunks cannot. Hence, in a situation where a HEARTBEAT ACK
arrives while there is data outstanding towards the destination
address to which the HEARTBEAT was sent, then an implementation
MAY choose to not have the HEARTBEAT ACK reset the error
counter, but have the error counter reset await the fate of the
outstanding data transmission. This situation can happen when
data is sent to a destination address in PF state. When the
sender resumes data transmission on a destination address after
a transition of the destination address from PF to active state,
it MUST do this following the prescriptions of Section 7.2 of it MUST do this following the prescriptions of Section 7.2 of
[RFC4960]. In a situation where a HEARTBEAT ACK arrives while [RFC4960].
there is data outstanding towards the destination address to
which the HEARTBEAT was sent, then an implementation MAY choose
to not have the HEARTBEAT ACK reset the error counter, but have
the error counter reset await the fate of the outstanding data
transmission. This situation can happen when data is sent to a
destination address in PF state.
8. Additional (PMR - PFMR) consecutive timeouts on a destination 8. Additional (PMR - PFMR) consecutive timeouts on a destination
address in PF state confirm the path failure, upon which the address in PF state confirm the path failure, upon which the
destination address transitions to the inactive state. As destination address transitions to the inactive state. As
described in [RFC4960], the sender (i) SHOULD notify the ULP described in [RFC4960], the sender (i) SHOULD notify the ULP
about this state transition, and (ii) transmit HEARTBEAT chunks about this state transition, and (ii) transmit HEARTBEAT chunks
to the inactive destination address at a lower HB.interval to the inactive destination address at a lower HB.interval
frequency as described in Section 8.3 of [RFC4960] (when the frequency as described in Section 8.3 of [RFC4960] (when the
Path Heartbeat function is enabled for the destination address). Path Heartbeat function is enabled for the destination address).
9. Acknowledgments for chunks that have been transmitted to 9. Acknowledgments for chunks that have been transmitted to
multiple destinations (i.e., a chunk which has been multiple destinations (i.e., a chunk which has been
retransmitted to a different destination address than the retransmitted to a different destination address than the
destination address to which the chunk was first transmitted) destination address to which the chunk was first transmitted)
SHOULD NOT clear the error count for an inactive destination SHOULD NOT clear the error count for an inactive destination
address and SHOULD NOT move a destination address in PF state address and SHOULD NOT move a destination address in PF state
back to active state, since a sender cannot disambiguate whether back to active state, since a sender cannot disambiguate whether
the ACK was for the original transmission or the the ACK was for the original transmission or the
retransmission(s). A SCTP sender MAY clear the error counter retransmission(s). A SCTP sender MAY clear the error counter
and move a destination address back to active state if it has and move a destination address back to active state by
other information, than the acknowledgment, that uniquely information other than acknowledgments, when it can uniquely
determines which destination, among multiple destination determine which destination, among multiple destination
addresses, the chunk reached. This document makes no reference addresses, the chunk reached. This document makes no reference
to what such information could consist of, nor how such to what such information could consist of, nor how such
information could be obtained. information could be obtained.
10. Acknowledgments for data chunks that has been transmitted to one 10. Acknowledgments for data chunks that has been transmitted to one
destination address only MUST clear the error counter for the destination address only MUST clear the error counter for the
destination address and MUST transition a destination address in destination address and MUST transition a destination address in
PF state back to active state. This situation can happen when PF state back to active state. This situation can happen when
new data is sent to a destination address in the PF state. It new data is sent to a destination address in the PF state. It
can also happen in situations where the destination address is can also happen in situations where the destination address is
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[RFC4960] SCTP implementation with the same Path.Max.Retrans (PMR) [RFC4960] SCTP implementation with the same Path.Max.Retrans (PMR)
and Association.Max.Retrans (AMR) setting, we prescribe for that an and Association.Max.Retrans (AMR) setting, we prescribe for that an
SCTP-PF implementation SHOULD operate as described below in SCTP-PF implementation SHOULD operate as described below in
Section 4.1 during dormant state. Section 4.1 during dormant state.
An SCTP-PF implementation MAY choose a different dormant state An SCTP-PF implementation MAY choose a different dormant state
operation than the one described below in Section 4.1 provided that operation than the one described below in Section 4.1 provided that
the solution chosen does not decrease the fault tolerance of the the solution chosen does not decrease the fault tolerance of the
SCTP-PF operation. SCTP-PF operation.
The below prescription for SCTP-PF dormant state handling SHOULD NOT The below prescription for SCTP-PF dormant state handling MUST NOT be
be coupled to the value of the PFMR, but solely to the activation of coupled to the value of the PFMR, but solely to the activation of
SCTP-PF logic in an SCTP implementation. SCTP-PF logic in an SCTP implementation.
It is noted that the below dormant state operation is considered to It is noted that the below dormant state operation is considered to
provide added disruption tolerance also for an [RFC4960] SCTP provide added disruption tolerance also for an [RFC4960] SCTP
implementation, and that it can be sensible for an [RFC4960] SCTP implementation, and that it can be sensible for an [RFC4960] SCTP
implementation to follow this mode of operation. For an [RFC4960] implementation to follow this mode of operation. For an [RFC4960]
SCTP implementation the continuation of data transmission during SCTP implementation the continuation of data transmission during
dormant state makes the fault tolerance of SCTP be more robust dormant state makes the fault tolerance of SCTP be more robust
towards situations where some, or all, alternative paths of an SCTP towards situations where some, or all, alternative paths of an SCTP
association approach, or reach, inactive state before the primary association approach, or reach, inactive state before the primary
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MAY support also, as alternative behavior, the Primary Path MAY support also, as alternative behavior, the Primary Path
Switchover mode of operation and MAY enable it based on applications' Switchover mode of operation and MAY enable it based on applications'
requests. requests.
For an SCTP implementation that implements the Primary Path For an SCTP implementation that implements the Primary Path
Switchover operation, this specification RECOMMENDS that the standard Switchover operation, this specification RECOMMENDS that the standard
RFC4960 switchback operation is retained as the default operation. RFC4960 switchback operation is retained as the default operation.
6. Suggested SCTP Protocol Parameter Values 6. Suggested SCTP Protocol Parameter Values
This document does not alter the [RFC4960] value RECOMMENDATIONS for This document does not alter the [RFC4960] value recommendation for
the SCTP Protocol Parameters defined in [RFC4960]. the SCTP Protocol Parameters defined in [RFC4960].
The following protocol parameter is RECOMMENDED: The following protocol parameter is RECOMMENDED:
PotentiallyFailed.Max.Retrans (PFMR) - 0 PotentiallyFailed.Max.Retrans (PFMR) - 0
7. Socket API Considerations 7. Socket API Considerations
This section describes how the socket API defined in [RFC6458] is This section describes how the socket API defined in [RFC6458] is
extended to provide a way for the application to control and observe extended to provide a way for the application to control and observe
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spt_pathcpthld: Each peer address of interest is not considered the spt_pathcpthld: Each peer address of interest is not considered the
primary remote address anymore, if its path error counter exceeds primary remote address anymore, if its path error counter exceeds
spt_pathcpthld. Using a value of 0xffff disables the selection of spt_pathcpthld. Using a value of 0xffff disables the selection of
a new primary peer address. If an implementation does not support a new primary peer address. If an implementation does not support
the automatically selection of a new primary address, it should the automatically selection of a new primary address, it should
indicate an error with errno set to EINVAL if a value different indicate an error with errno set to EINVAL if a value different
from 0xffff is used in spt_pathcpthld. For SCTP-PF, the setting from 0xffff is used in spt_pathcpthld. For SCTP-PF, the setting
of spt_pathcpthld < spt_pathpfthld should be rejected with errno of spt_pathcpthld < spt_pathpfthld should be rejected with errno
set to EINVAL. For [RFC4960] SCTP, the setting of spt_pathcpthld set to EINVAL. For [RFC4960] SCTP, the setting of spt_pathcpthld
< spt_pathmaxrxt should be rejected with errno set to EINVAL. A < spt_pathmaxrxt should be rejected with errno set to EINVAL. A
SCTP-PF implementation MAY support only setting of spt_pathcpthld SCTP-PF implementation may support only setting of spt_pathcpthld
= spt_pathpfthld and spt_pathcpthld = 0xffff and a [RFC4960] SCTP = spt_pathpfthld and spt_pathcpthld = 0xffff and a [RFC4960] SCTP
implementation MAY support only setting of spt_pathcpthld = implementation may support only setting of spt_pathcpthld =
spt_pathmaxrxt and spt_pathcpthld = 0xffff. In these cases SCTP spt_pathmaxrxt and spt_pathcpthld = 0xffff. In these cases SCTP
shall reject setting of other values with errno set to EINVAL. shall reject setting of other values with errno set to EINVAL.
7.3. Exposing the Potentially Failed Path State 7.3. Exposing the Potentially Failed Path State
(SCTP_EXPOSE_POTENTIALLY_FAILED_STATE) Socket Option (SCTP_EXPOSE_POTENTIALLY_FAILED_STATE) Socket Option
Applications can control the exposure of the potentially failed path Applications can control the exposure of the potentially failed path
state in the SCTP_PEER_ADDR_CHANGE event and the state in the SCTP_PEER_ADDR_CHANGE event and the
SCTP_GET_PEER_ADDR_INFO as described in Section 7.1. The default SCTP_GET_PEER_ADDR_INFO as described in Section 7.1. The default
value is implementation specific. value is implementation specific.
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Primary Path Switchover here happens already at the first RTO timeout Primary Path Switchover here happens already at the first RTO timeout
experienced. Users of the Primary Path Switchover mechanism should experienced. Users of the Primary Path Switchover mechanism should
be aware of this fact. be aware of this fact.
The event notification of path state transfer from active to The event notification of path state transfer from active to
potentially failed state and vice versa gives attackers an increased potentially failed state and vice versa gives attackers an increased
possibility to generate more local events. However, it is assumed possibility to generate more local events. However, it is assumed
that event notifications are rate-limited in the implementation to that event notifications are rate-limited in the implementation to
address this threat. address this threat.
9. IANA Considerations 9. MIB Considerations
SCTP-PF introduces new SCTP algorithms for failover and switchback
with associated new state parameters. It is recommended that the
SCTP-MIB defined in [RFC3873] is updated to support the management of
the SCTP-PF implementation. This can be done by extending the
sctpAssocRemAddrActive field of the SCTPAssocRemAddrTable to include
information of the PF state of the destination address and by adding
new fields to the SCTPAssocRemAddrTable supporting
PotentiallyFailed.Max.Retrans (PFMR) and
Primary.Switchover.Max.Retrans (PSMR) parameters.
10. IANA Considerations
This document does not create any new registries or modify the rules This document does not create any new registries or modify the rules
for any existing registries managed by IANA. for any existing registries managed by IANA.
10. Acknowledgements 11. Acknowledgements
The authors wish to thank Michael Tuexen for his many invaluable The authors wish to thank Michael Tuexen for his many invaluable
comments and for his very substantial support with the making of this comments and for his very substantial support with the making of this
document. document.
11. Proposed Change of Status (to be Deleted before Publication) 12. Proposed Change of Status (to be Deleted before Publication)
Initially this work looked to entail some changes of the Congestion Initially this work looked to entail some changes of the Congestion
Control (CC) operation of SCTP and for this reason the work was Control (CC) operation of SCTP and for this reason the work was
proposed as Experimental. These intended changes of the CC operation proposed as Experimental. These intended changes of the CC operation
have since been judged to be irrelevant and are no longer part of the have since been judged to be irrelevant and are no longer part of the
specification. As the specification entails no other potential specification. As the specification entails no other potential
harmful features, consensus exists in the WG to bring the work harmful features, consensus exists in the WG to bring the work
forward as PS. forward as PS.
Initially concerns have been expressed about the possibility for the Initially concerns have been expressed about the possibility for the
mechanism to introduce path bouncing with potential harmful network mechanism to introduce path bouncing with potential harmful network
impacts. These concerns are believed to be unfounded. This issue is impacts. These concerns are believed to be unfounded. This issue is
addressed in Appendix B. addressed in Appendix B.
It is noted that the feature specified by this document is It is noted that the feature specified by this document is
implemented by multiple SCTP SW implementations and furthermore that implemented by multiple SCTP SW implementations and furthermore that
various variants of the solution have been deployed in telephony various variants of the solution have been deployed in telephony
signaling environments for several years with good results. signaling environments for several years with good results.
12. References 13. References
12.1. Normative References 13.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997. Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC4960] Stewart, R., "Stream Control Transmission Protocol", RFC [RFC4960] Stewart, R., "Stream Control Transmission Protocol", RFC
4960, September 2007. 4960, September 2007.
12.2. Informative References 13.2. Informative References
[CARO02] Caro Jr., A., Iyengar, J., Amer, P., Heinz, G., and R. [CARO02] Caro Jr., A., Iyengar, J., Amer, P., Heinz, G., and R.
Stewart, "A Two-level Threshold Recovery Mechanism for Stewart, "A Two-level Threshold Recovery Mechanism for
SCTP", Tech report, CIS Dept, University of Delaware , 7 SCTP", Tech report, CIS Dept, University of Delaware , 7
2002. 2002.
[CARO04] Caro Jr., A., Amer, P., and R. Stewart, "End-to-End [CARO04] Caro Jr., A., Amer, P., and R. Stewart, "End-to-End
Failover Thresholds for Transport Layer Multi homing", Failover Thresholds for Transport Layer Multi homing",
MILCOM 2004 , 11 2004. MILCOM 2004 , 11 2004.
skipping to change at page 18, line 10 skipping to change at page 18, line 31
[JUNGMAIER02] [JUNGMAIER02]
Jungmaier, A., Rathgeb, E., and M. Tuexen, "On the use of Jungmaier, A., Rathgeb, E., and M. Tuexen, "On the use of
SCTP in failover scenarios", World Multiconference on SCTP in failover scenarios", World Multiconference on
Systemics, Cybernetics and Informatics , 7 2002. Systemics, Cybernetics and Informatics , 7 2002.
[NATARAJAN09] [NATARAJAN09]
Natarajan, P., Ekiz, N., Amer, P., and R. Stewart, Natarajan, P., Ekiz, N., Amer, P., and R. Stewart,
"Concurrent Multipath Transfer during Path Failure", "Concurrent Multipath Transfer during Path Failure",
Computer Communications , 5 2009. Computer Communications , 5 2009.
[RFC3873] Pastor, J. and M. Belinchon, "Stream Control Transmission
Protocol (SCTP) Management Information Base (MIB)", RFC
3873, DOI 10.17487/RFC3873, September 2004,
<http://www.rfc-editor.org/info/rfc3873>.
[RFC6458] Stewart, R., Tuexen, M., Poon, K., Lei, P., and V. [RFC6458] Stewart, R., Tuexen, M., Poon, K., Lei, P., and V.
Yasevich, "Sockets API Extensions for the Stream Control Yasevich, "Sockets API Extensions for the Stream Control
Transmission Protocol (SCTP)", RFC 6458, December 2011. Transmission Protocol (SCTP)", RFC 6458, December 2011.
Appendix A. Discussions of Alternative Approaches Appendix A. Discussions of Alternative Approaches
This section lists alternative approaches for the issues described in This section lists alternative approaches for the issues described in
this document. Although these approaches do not require to update this document. Although these approaches do not require to update
RFC4960, we do not recommend them from the reasons described below. RFC4960, we do not recommend them from the reasons described below.
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