draft-ietf-tsvwg-sctp-prpolicies-04.txt   draft-ietf-tsvwg-sctp-prpolicies-05.txt 
Network Working Group M. Tuexen Network Working Group M. Tuexen
Internet-Draft Muenster Univ. of Appl. Sciences Internet-Draft Muenster Univ. of Appl. Sciences
Intended status: Standards Track R. Seggelmann Intended status: Standards Track R. Seggelmann
Expires: April 1, 2015 T-Systems International GmbH Expires: May 13, 2015 T-Systems International GmbH
R. Stewart R. Stewart
Netflix, Inc. Netflix, Inc.
S. Loreto S. Loreto
Ericsson Ericsson
September 28, 2014 November 9, 2014
Additional Policies for the Partial Reliability Extension of the Stream Additional Policies for the Partial Reliability Extension of the Stream
Control Transmission Protocol Control Transmission Protocol
draft-ietf-tsvwg-sctp-prpolicies-04.txt draft-ietf-tsvwg-sctp-prpolicies-05.txt
Abstract Abstract
This document defines two additional policies for the Partial This document defines two additional policies for the Partial
Reliability Extension of the Stream Control Transmission Protocol Reliability Extension of the Stream Control Transmission Protocol
(PR-SCTP) allowing to limit the number of retransmissions or to (PR-SCTP) allowing to limit the number of retransmissions or to
prioritize user messages for more efficient send buffer usage. prioritize user messages for more efficient send buffer usage.
Status of This Memo Status of This Memo
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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-
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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 April 1, 2015. This Internet-Draft will expire on May 13, 2015.
Copyright Notice Copyright Notice
Copyright (c) 2014 IETF Trust and the persons identified as the Copyright (c) 2014 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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policies are OPTIONAL when implementing [RFC3758]. policies are OPTIONAL when implementing [RFC3758].
3.1. Limited Retransmissions Policy 3.1. Limited Retransmissions Policy
Using the Limited Retransmission Policy allows the sender of a user Using the Limited Retransmission Policy allows the sender of a user
message to specify an upper limit for the number of retransmissions message to specify an upper limit for the number of retransmissions
for each DATA chunk of the given user messages. The sender MUST for each DATA chunk of the given user messages. The sender MUST
abandon a user message if the number of retransmissions of any of the abandon a user message if the number of retransmissions of any of the
DATA chunks of the user message would exceed the provided limit. The DATA chunks of the user message would exceed the provided limit. The
sender MUST perform all other actions required for processing the sender MUST perform all other actions required for processing the
retransmission event, like possibly adopting the congestion window retransmission event, such as adapting the congestion window and the
and the retransmission timeout. Please note that the number of retransmission timeout. Please note that the number of
retransmissions includes both fast and timer based retransmissions. retransmissions includes both fast and timer-based retransmissions.
The sender MAY limit the number of retransmissions to 0. This will The sender MAY limit the number of retransmissions to 0. This will
result in abandoning the message when it would get retransmitted for result in abandoning the message when it would get retransmitted for
the first time. The use of this setting provides a service similar the first time. The use of this setting provides a service similar
to UDP, which also does not perform any retransmissions. to UDP, which also does not perform any retransmissions.
The Limited Retransmissions Policy is used for data channels in the The Limited Retransmissions Policy can be used with data channels in
WebRTC protocol stack. See [I-D.ietf-rtcweb-data-channel] for more the WebRTC protocol stack. See [I-D.ietf-rtcweb-data-channel] for
information. more information.
3.2. Priority Policy 3.2. Priority Policy
Using the Priority Policy allows the sender of a user message to Using the Priority Policy allows the sender of a user message to
specify a priority. When storing a user message in the send buffer specify a priority. When storing a user message in the send buffer
while there is not enough available space, the SCTP stack at the while there is not enough available space, the SCTP stack at the
sender side MAY abandon other user messages of the same SCTP sender side MAY abandon other user messages of the same SCTP
association with a priority lower than the provided one. The association with a priority lower than the provided one. The
algorithm for selecting the message being abandoned is implementation algorithm for selecting the message being abandoned is implementation
specific. specific.
After lower priority messages have been abandoned high priority After lower priority messages have been abandoned high priority
messages can be transferred without blocking the send call (if used messages can be transferred without the send call blocking (if used
in blocking mode) or the send call fails (if used in non-blocking in blocking mode) or the send call failing (if used in non-blocking
mode). mode).
The Priority Policy can be used in the IPFIX protocol stack. See The Priority Policy can be used in the IPFIX protocol stack. See
[RFC7011] for more information. [RFC7011] for more information.
4. Socket API Considerations 4. 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 support the newly defined PR-SCTP policies, to provide extended to support the newly defined PR-SCTP policies, to provide
some statistical information and to control the negotiation of the some statistical information and to control the negotiation of the
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struct sctp_prinfo { struct sctp_prinfo {
uint16_t pr_policy; uint16_t pr_policy;
uint32_t pr_value; uint32_t pr_value;
}; };
When the Limited Retransmission Policy described in Section 3.1 is When the Limited Retransmission Policy described in Section 3.1 is
used, pr_policy has the value SCTP_PR_SCTP_RTX and the number of used, pr_policy has the value SCTP_PR_SCTP_RTX and the number of
retransmissions is given in pr_value. retransmissions is given in pr_value.
For using the Priority Policy described in Section 3.2, pr_policy has When using the Priority Policy described in Section 3.2, pr_policy
the value SCTP_PR_SCTP_PRIO. The priority is given in pr_value. The has the value SCTP_PR_SCTP_PRIO. The priority is given in pr_value.
value of zero is the highest priority and larger numbers in pr_value The value of zero is the highest priority and larger numbers in
denote lower priorities. pr_value denote lower priorities.
The following table summarizes the possible parameter settings The following table summarizes the possible parameter settings
defined in [RFC6458] and this document: defined in [RFC6458] and this document:
+-------------------+---------------------------+---------------+ +-------------------+---------------------------+---------------+
| pr_policy | pr_value | Specification | | pr_policy | pr_value | Specification |
+-------------------+---------------------------+---------------+ +-------------------+---------------------------+---------------+
| SCTP_PR_SCTP_NONE | Ignored | [RFC6458] | | SCTP_PR_SCTP_NONE | Ignored | [RFC6458] |
| SCTP_PR_SCTP_TTL | Lifetime in ms | [RFC6458] | | SCTP_PR_SCTP_TTL | Lifetime in ms | [RFC6458] |
| SCTP_PR_SCTP_RTX | Number of retransmissions | Section 3.1 | | SCTP_PR_SCTP_RTX | Number of retransmissions | Section 3.1 |
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There are separate counters for unsent and sent user messages because There are separate counters for unsent and sent user messages because
the SCTP_SEND_FAILED_EVENT supports a similar differentiation. the SCTP_SEND_FAILED_EVENT supports a similar differentiation.
Please note that an abandoned large user message requiring an SCTP Please note that an abandoned large user message requiring an SCTP
level fragmentation is reported in the sprstat_abandoned_sent counter level fragmentation is reported in the sprstat_abandoned_sent counter
as soon as at least one fragment of it has been sent. Therefore each as soon as at least one fragment of it has been sent. Therefore each
abandoned user message is either counted in sprstat_abandoned_unsent abandoned user message is either counted in sprstat_abandoned_unsent
or sprstat_abandoned_sent. or sprstat_abandoned_sent.
If more detailed information about abandoned user messages is If more detailed information about abandoned user messages is
required, the subscription to the SCTP_SEND_FAILED_EVENT is required, the subscription to the SCTP_SEND_FAILED_EVENT is
recommended. Please note that some implementations might not support recommended. Please note that some implementations might choose not
this option on purpose, since it increases the resources needed for to support this option, since it increases the resources needed for
an outgoing SCTP stream. For the same reasons, some implementations an outgoing SCTP stream. For the same reasons, some implementations
might only support using SCTP_PR_SCTP_ALL in sprstat_policy. might only support using SCTP_PR_SCTP_ALL in sprstat_policy.
sctp_opt_info() needs to be extended to support sctp_opt_info() needs to be extended to support
SCTP_PR_STREAM_STATUS. SCTP_PR_STREAM_STATUS.
4.4. Socket Option for Getting the Association Specific PR-SCTP Status 4.4. Socket Option for Getting the Association Specific PR-SCTP Status
(SCTP_PR_ASSOC_STATUS) (SCTP_PR_ASSOC_STATUS)
This socket option uses IPPROTO_SCTP as its level and This socket option uses IPPROTO_SCTP as its level and
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6. Security Considerations 6. Security Considerations
This document does not add any additional security considerations in This document does not add any additional security considerations in
addition to the ones given in [RFC4960], [RFC3758], and [RFC6458]. addition to the ones given in [RFC4960], [RFC3758], and [RFC6458].
As indicated in the Security Section of [RFC3758], transport layer As indicated in the Security Section of [RFC3758], transport layer
security in the form of TLS over SCTP (see [RFC3436]) can't be used security in the form of TLS over SCTP (see [RFC3436]) can't be used
for PR-SCTP. However, DTLS over SCTP (see [RFC6083]) could be used for PR-SCTP. However, DTLS over SCTP (see [RFC6083]) could be used
instead. It should also be noted that using PR-SCTP for an SCTP instead. It should also be noted that using PR-SCTP for an SCTP
association doesn't allow that association to behave more association doesn't allow that association to behave more
aggressively congestion-control wise than an SCTP association not aggressively than an SCTP association not using PR-SCTP.
using PR-SCTP.
7. Acknowledgments 7. Acknowledgments
The authors wish to thank Gorry Fairhurst, Karen Egede Nielsen, Ka- The authors wish to thank Spencer Dawkins, Gorry Fairhurst, Karen
Cheong Poon, Irene Ruengeler, Jamal Hadi Salim, and Vlad Yasevich for Egede Nielsen, Ka-Cheong Poon, Irene Ruengeler, Jamal Hadi Salim, and
their invaluable comments. Vlad Yasevich for their invaluable comments.
8. References 8. References
8.1. Normative References 8.1. 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.
[RFC3758] Stewart, R., Ramalho, M., Xie, Q., Tuexen, M., and P. [RFC3758] Stewart, R., Ramalho, M., Xie, Q., Tuexen, M., and P.
Conrad, "Stream Control Transmission Protocol (SCTP) Conrad, "Stream Control Transmission Protocol (SCTP)
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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.
[RFC7011] Claise, B., Trammell, B., and P. Aitken, "Specification of [RFC7011] Claise, B., Trammell, B., and P. Aitken, "Specification of
the IP Flow Information Export (IPFIX) Protocol for the the IP Flow Information Export (IPFIX) Protocol for the
Exchange of Flow Information", STD 77, RFC 7011, September Exchange of Flow Information", STD 77, RFC 7011, September
2013. 2013.
[I-D.ietf-rtcweb-data-channel] [I-D.ietf-rtcweb-data-channel]
Jesup, R., Loreto, S., and M. Tuexen, "WebRTC Data Jesup, R., Loreto, S., and M. Tuexen, "WebRTC Data
Channels", draft-ietf-rtcweb-data-channel-11 (work in Channels", draft-ietf-rtcweb-data-channel-12 (work in
progress), July 2014. progress), September 2014.
[IEEE.1003-1G.1997] [IEEE.1003-1G.1997]
Institute of Electrical and Electronics Engineers, Institute of Electrical and Electronics Engineers,
"Protocol Independent Interfaces", IEEE Standard 1003.1G, "Protocol Independent Interfaces", IEEE Standard 1003.1G,
March 1997. March 1997.
Authors' Addresses Authors' Addresses
Michael Tuexen Michael Tuexen
Muenster University of Applied Sciences Muenster University of Applied Sciences
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DE DE
Email: tuexen@fh-muenster.de Email: tuexen@fh-muenster.de
Robin Seggelmann Robin Seggelmann
T-Systems International GmbH T-Systems International GmbH
Fasanenweg 5 Fasanenweg 5
70771 Leinfelden-Echterdingen 70771 Leinfelden-Echterdingen
DE DE
Email: robin.seggelmann@t-systems.com Email: rfc@robin-seggelmann.com
Randall R. Stewart Randall R. Stewart
Netflix, Inc. Netflix, Inc.
Chapin, SC 29036 Chapin, SC 29036
US US
Email: randall@lakerest.net Email: randall@lakerest.net
Salvatore Loreto Salvatore Loreto
Ericsson Ericsson
Hirsalantie 11 Hirsalantie 11
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