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 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 August 21, 2013. 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 Loreto, et al. Expires August 21, 2013 [Page 1] Internet-Draft Additional PR-SCTP Policies February 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 . . . . . . . . . . . . . . . . . . . . . . . . . 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 Loreto, et al. Expires August 21, 2013 [Page 2] Internet-Draft Additional PR-SCTP Policies February 2013 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. Loreto, et al. Expires August 21, 2013 [Page 3] Internet-Draft Additional PR-SCTP Policies February 2013 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 Loreto, et al. Expires August 21, 2013 [Page 4] Internet-Draft Additional PR-SCTP Policies February 2013 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 Loreto, et al. Expires August 21, 2013 [Page 5] Internet-Draft Additional PR-SCTP Policies February 2013 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 Loreto, et al. Expires August 21, 2013 [Page 6]