One document matched: draft-tuexen-tsvwg-sctp-prpolicies-01.txt
Differences from draft-tuexen-tsvwg-sctp-prpolicies-00.txt
Network Working Group S. Loreto
Internet-Draft Ericsson
Intended status: Informational R. Seggelmann
Expires: January 10, 2014 T-Systems International GmbH
R. Stewart
Adara Networks
M. Tuexen
Muenster Univ. of Appl. Sciences
July 09, 2013
Additional Policies for the Partial Delivery Extension of the Stream
Control Transmission Protocol
draft-tuexen-tsvwg-sctp-prpolicies-01.txt
Abstract
This document defines policies for the Partial Reliability Extension
of the Stream Control Transmission Protocol (PR-SCTP) allowing to
limit the number of retransmissions or to prioritize user messages
for more efficient send buffer usage.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on January 10, 2014.
Copyright Notice
Copyright (c) 2013 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
(http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
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Internet-Draft Additional PR-SCTP Policies July 2013
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 . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Overview . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Additional PR-SCTP Policies . . . . . . . . . . . . . . . . . 2
2.1. Limited Retransmissions Policy . . . . . . . . . . . . . 3
2.2. Priority Policy . . . . . . . . . . . . . . . . . . . . . 3
3. Socket API Considerations . . . . . . . . . . . . . . . . . . 3
3.1. Support for Added PR-SCTP Policies . . . . . . . . . . . 3
3.2. Socket Option for Getting the PR-SCTP Status
(SCTP_GET_PR_STATUS) . . . . . . . . . . . . . . . . . . 4
4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5
5. Security Considerations . . . . . . . . . . . . . . . . . . . 5
6. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 5
7. References . . . . . . . . . . . . . . . . . . . . . . . . . 5
7.1. Normative References . . . . . . . . . . . . . . . . . . 5
7.2. Informative References . . . . . . . . . . . . . . . . . 5
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 6
1. Introduction
1.1. Overview
The SCTP Partial Reliability Extension (PR-SCTP) defined in [RFC3758]
provides a generic method for senders to abandon user messages. The
decision to abandon a user message is sender side only and the exact
condition is called a PR-SCTP policy. [RFC3758] also defines one
particular PR-SCTP policy, called Timed Reliability. This allows the
sender to specify a timeout for a user message after which the SCTP
stack abandons the user message.
This document specifies two additional PR-SCTP policies:
Limited Retransmission Policy: Allows to limit the number of
retransmissions.
Priority Policy: Allows to discard lower priority messages if space
for higher priority messages is needed in the send buffer.
2. Additional PR-SCTP Policies
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2.1. Limited Retransmissions Policy
Using the Limited Retransmission Policy allows the sender of a user
message to specify an upper limit for the number retransmissions for
each DATA chunk of the given user messages. The sender must abandon
a user message if the number of retransmission of any of the DATA
chunks of the user message would exceed the provided limit. Please
note that the number of retransmissions includes the fast and the
timer based retransmissions.
Limiting the number of retransmissions to 0 is allowed. This
provides a service similar to UDP, which also doesn't do any
retransmissions.
The Limited Retransmissions Policy is used for data channels in the
RTCWeb protocol stack. See [I-D.ietf-rtcweb-data-channel] for more
information.
2.2. Priority Policy
Using the Priority Policy allows the sender of a user message to
specify a priority. When storing a user message in the send buffer
and there is not enough available space, the SCTP stack may abandon
other user messages with a priority lower than the provided one.
This allows to transfer message with high priority without blocking
the send() call, if it is acceptable to abandon lower priority
messages.
The Priority Policy can be used in the IPFIX protocol stack. See
[RFC5101] for more information.
3. Socket API Considerations
This section describes how the socket API defined in [RFC6458] is
extended to support the newly defined PR-SCTP policies and to provide
some statistical information.
Please note that this section is informational only.
3.1. Support for Added PR-SCTP Policies
As defined in [RFC6458], the PR-SCTP policy is specified and
configured by using the following sctp_prinfo structure:
struct sctp_prinfo {
uint16_t pr_policy;
uint32_t pr_value;
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};
When the Limited Retransmission Policy described in Section 2.1 is
used, pr_policy has the value SCTP_PR_SCTP_RTX and the number of
retransmissions is given in pr_value.
For using the Priority Policy described in Section 2.2, pr_policy has
the value SCTP_PR_SCTP_PRIO. The priority is given in pr_value. The
value of zero is the highest priority and larger numbers in pr_value
denote lower priorities.
The following table summarizes the possible parameter settings
defined in [RFC6458] and this document:
+-------------------+---------------------------+---------------+
| pr_policy | pr_value | Specification |
+-------------------+---------------------------+---------------+
| SCTP_PR_SCTP_NONE | Ignored | [RFC6458] |
| SCTP_PR_SCTP_TTL | Lifetime in ms | [RFC6458] |
| SCTP_PR_SCTP_RTX | Number of retransmissions | Section 2.1 |
| SCTP_PR_SCTP_PRIO | Priority | Section 2.2 |
+-------------------+---------------------------+---------------+
3.2. Socket Option for Getting the PR-SCTP Status (SCTP_GET_PR_STATUS)
This socket option uses IPPROTO_SCTP as its level, SCTP_GET_PR_STATUS
as its name and can only be used with getsockopt(). The socket
option value uses the following structure:
struct sctp_prstatus {
sctp_assoc_t sprstat_assoc_id;
uint32_t sprstat_abandoned_unsent;
uint32_t sprstat_abandoned_sent;
};
sprstat_assoc_id: This parameter is ignored for one-to-one style
sockets. For one-to-many style sockets this parameter indicates
for which association the user wants the information. It is an
error to use SCTP_{CURRENT|ALL|FUTURE}_ASSOC in sprstat_assoc_id
sprstat_abandoned_unsent: The number of user messages which are
abandoned, but no part of it has been sent.
sprstat_abandoned_sent: The number of user messages which are
abandoned, but at least part of it has been sent.
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If more detailed information about abandoned user messages is
required, the subscription to the SCTP_SEND_FAILED_EVENT is
recommended.
Please note that sctp_opt_info() needs to be extended to support
SCTP_GET_PR_STATUS.
4. IANA Considerations
This document requires no actions from IANA.
5. Security Considerations
This document does not add any additional security considerations in
addition to the ones given in [RFC4960], [RFC3758], and [RFC6458].
6. Acknowledgments
The authors wish to thank Jamal Hadi Salim, and Vlad Yasevich for
there invaluable comments.
7. References
7.1. Normative References
[RFC3758] Stewart, R., Ramalho, M., Xie, Q., Tuexen, M., and P.
Conrad, "Stream Control Transmission Protocol (SCTP)
Partial Reliability Extension", RFC 3758, May 2004.
[RFC4960] Stewart, R., "Stream Control Transmission Protocol", RFC
4960, September 2007.
7.2. Informative References
[RFC5101] Claise, B., "Specification of the IP Flow Information
Export (IPFIX) Protocol for the Exchange of IP Traffic
Flow Information", RFC 5101, January 2008.
[RFC6458] Stewart, R., Tuexen, M., Poon, K., Lei, P., and V.
Yasevich, "Sockets API Extensions for the Stream Control
Transmission Protocol (SCTP)", RFC 6458, December 2011.
[I-D.ietf-rtcweb-data-channel]
Jesup, R., Loreto, S., and M. Tuexen, "RTCWeb Data
Channels", draft-ietf-rtcweb-data-channel-04 (work in
progress), February 2013.
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Authors' Addresses
Salvatore Loreto
Ericsson
Hirsalantie 11
Jorvas 02420
FI
Email: Salvatore.Loreto@ericsson.com
Robin Seggelmann
T-Systems International GmbH
Fasanenweg 5
70771 Leinfelden-Echterdingen
DE
Email: robin.seggelmann@t-systems.com
Randall R. Stewart
Adara Networks
Chapin, SC 29036
US
Email: randall@lakerest.net
Michael Tuexen
Muenster University of Applied Sciences
Stegerwaldstrasse 39
48565 Steinfurt
DE
Email: tuexen@fh-muenster.de
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