Network Working Group S. Loreto
Internet-Draft Ericsson
Intended status: Standards Track R. Seggelmann
Expires: August 21, 2013 T-Systems International GmbH
R. Stewart
Adara Networks
M. Tuexen
Muenster Univ. of Appl. Sciences
February 17, 2013
Additional Policies for the Partial Delivery Extension of the Stream
Control Transmission Protocol
draft-tuexen-tsvwg-sctp-prpolicies-00.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
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This Internet-Draft will expire on August 21, 2013.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Overview . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.2. Conventions . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Additional PR-SCTP Policies . . . . . . . . . . . . . . . . . . 3
2.1. Limited Retransmissions Policy . . . . . . . . . . . . . . 3
2.2. Priority Policy . . . . . . . . . . . . . . . . . . . . . . 4
3. Socket API Considerations . . . . . . . . . . . . . . . . . . . 4
4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 4
5. Security Considerations . . . . . . . . . . . . . . . . . . . . 4
6. References . . . . . . . . . . . . . . . . . . . . . . . . . . 5
6.1. Normative References . . . . . . . . . . . . . . . . . . . 5
6.2. Informative References . . . . . . . . . . . . . . . . . . 5
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 5
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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 specified two additional PR-SCTP policies:
Limited Retransmission Policy: Allowing to limit the number of
retransmissions.
Priority Policy: Allowing to discard lower priority messages if
space for higher priority messages is needed in the send buffer.
1.2. Conventions
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 [RFC2119].
2. Additional PR-SCTP Policies
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.
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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.
Please note that this section is informational only.
As specified in [RFC6458], the PR-SCTP policy is configured by using
the following sctp_prinfo structure:
struct sctp_prinfo {
uint16_t pr_policy;
uint32_t pr_value;
};
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.
4. IANA Considerations
This document requires no actions from IANA.
5. Security Considerations
This document does not add any additional security considerations in
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addition to the ones given in [RFC4960], [RFC3758], and [RFC6458].
6. References
6.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[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.
6.2. 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 Datagram
Connection", draft-ietf-rtcweb-data-channel-02 (work in
progress), October 2012.
Authors' Addresses
Salvatore Loreto
Ericsson
Hirsalantie 11
Jorvas 02420
FI
Email: Salvatore.Loreto@ericsson.com
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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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