draft-ietf-tsvwg-sctp-prpolicies-02.txt   draft-ietf-tsvwg-sctp-prpolicies-03.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: Informational R. Seggelmann Intended status: Standards Track R. Seggelmann
Expires: October 10, 2014 T-Systems International GmbH Expires: November 30, 2014 T-Systems International GmbH
R. Stewart R. Stewart
Adara Networks Adara Networks
S. Loreto S. Loreto
Ericsson Ericsson
April 8, 2014 May 29, 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-02.txt draft-ietf-tsvwg-sctp-prpolicies-03.txt
Abstract Abstract
This document defines policies for the Partial Reliability Extension This document defines two additional policies for the Partial
of the Stream Control Transmission Protocol (PR-SCTP) allowing to Reliability Extension of the Stream Control Transmission Protocol
limit the number of retransmissions or to prioritize user messages (PR-SCTP) allowing to limit the number of retransmissions or to
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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Copyright Notice Copyright Notice
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Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Additional PR-SCTP Policies . . . . . . . . . . . . . . . . . 3 2. Conventions . . . . . . . . . . . . . . . . . . . . . . . . . 3
2.1. Limited Retransmissions Policy . . . . . . . . . . . . . 3 3. Additional PR-SCTP Policies . . . . . . . . . . . . . . . . . 3
2.2. Priority Policy . . . . . . . . . . . . . . . . . . . . . 3 3.1. Limited Retransmissions Policy . . . . . . . . . . . . . 3
3. Socket API Considerations . . . . . . . . . . . . . . . . . . 3 3.2. Priority Policy . . . . . . . . . . . . . . . . . . . . . 3
3.1. Data Types . . . . . . . . . . . . . . . . . . . . . . . 4 4. Socket API Considerations . . . . . . . . . . . . . . . . . . 4
3.2. Support for Added PR-SCTP Policies . . . . . . . . . . . 4 4.1. Data Types . . . . . . . . . . . . . . . . . . . . . . . 4
3.3. Socket Option for Getting the PR-SCTP Status 4.2. Support for Added PR-SCTP Policies . . . . . . . . . . . 4
(SCTP_PR_STATUS) . . . . . . . . . . . . . . . . . . . . 4 4.3. Socket Option for Getting the PR-SCTP Status
3.4. Socket Option for Getting and Setting the PR-SCTP Support (SCTP_PR_STATUS) . . . . . . . . . . . . . . . . . . . . 5
(SCTP_PR_SUPPORTED) . . . . . . . . . . . . . . . . . . . 5 4.4. Socket Option for Getting and Setting the PR-SCTP Support
4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6 (SCTP_PR_SUPPORTED) . . . . . . . . . . . . . . . . . . . 6
5. Security Considerations . . . . . . . . . . . . . . . . . . . 6 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6
6. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 6 6. Security Considerations . . . . . . . . . . . . . . . . . . . 6
7. References . . . . . . . . . . . . . . . . . . . . . . . . . 6 7. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 7
7.1. Normative References . . . . . . . . . . . . . . . . . . 6 8. References . . . . . . . . . . . . . . . . . . . . . . . . . 7
7.2. Informative References . . . . . . . . . . . . . . . . . 6 8.1. Normative References . . . . . . . . . . . . . . . . . . 7
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 7 8.2. Informative References . . . . . . . . . . . . . . . . . 7
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 8
1. Introduction 1. Introduction
The SCTP Partial Reliability Extension (PR-SCTP) defined in [RFC3758] The SCTP Partial Reliability Extension (PR-SCTP) defined in [RFC3758]
provides a generic method for senders to abandon user messages. The provides a generic method for senders to abandon user messages. The
decision to abandon a user message is sender side only and the exact decision to abandon a user message is sender side only and the exact
condition is called a PR-SCTP policy. [RFC3758] also defines one condition is called a PR-SCTP policy. [RFC3758] also defines one
particular PR-SCTP policy, called Timed Reliability. This allows the particular PR-SCTP policy, called Timed Reliability. This allows the
sender to specify a timeout for a user message after which the SCTP sender to specify a timeout for a user message after which the SCTP
stack abandons the user message. stack abandons the user message.
This document specifies two additional PR-SCTP policies: This document specifies the following two additional PR-SCTP
policies:
Limited Retransmission Policy: Allows to limit the number of Limited Retransmission Policy: Allows to limit the number of
retransmissions. retransmissions.
Priority Policy: Allows to discard lower priority messages if space Priority Policy: Allows to discard lower priority messages if space
for higher priority messages is needed in the send buffer. for higher priority messages is needed in the send buffer.
2. Additional PR-SCTP Policies 2. Conventions
This section defined two new PR-SCTP policies, one in each 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].
3. Additional PR-SCTP Policies
This section defines two new PR-SCTP policies, one in each
subsection. subsection.
2.1. Limited Retransmissions Policy Please note that it is REQUIRED to implement [RFC3758], if you want
to implement these additional policies. However, these additional
policies are OPTIONAL when implementing [RFC3758].
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. DATA chunks of the user message would exceed the provided limit. The
Please note that the number of retransmissions includes the fast and sender MUST perform all other actions required for processing the
the timer based retransmissions. retransmission event, like possibly adopting the congestion window
and the retransmission timeout. Please note that the number of
retransmissions includes both fast and timer based retransmissions.
Limiting the number of retransmissions to 0 is allowed. 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 send any retransmissions either. to UDP, which also does not perform any retransmissions.
The Limited Retransmissions Policy is used for data channels in the The Limited Retransmissions Policy is used for data channels in the
WebRTC protocol stack. WebRTC protocol stack. See [I-D.ietf-rtcweb-data-channel] for more
information.
2.2. 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 may abandon while there is not enough available space, the SCTP stack at the
other user messages with a priority lower than the provided one. The sender side MAY abandon other user messages of the same SCTP
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 blocking the send call (if used
in blocking mode) or failing the send call (if used in non-blocking in blocking mode) or the send call fails (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.
3. 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 and to provide extended to support the newly defined PR-SCTP policies, to provide
some statistical information. some statistical information and to control the negotiation of the
PR-SCTP extension during the SCTP association setup.
3.1. Data Types Please note that this section is informational only.
4.1. Data Types
This section uses data types from [IEEE.1003-1G.1997]: uintN_t means This section uses data types from [IEEE.1003-1G.1997]: uintN_t means
an unsigned integer of exactly N bits (e.g. uint16_t). This is the an unsigned integer of exactly N bits (e.g. uint16_t). This is the
same as in [RFC6458] same as in [RFC6458].
3.2. Support for Added PR-SCTP Policies 4.2. Support for Added PR-SCTP Policies
As defined in [RFC6458], the PR-SCTP policy is specified and As defined in [RFC6458], the PR-SCTP policy is specified and
configured by using the following sctp_prinfo structure: configured by using the following sctp_prinfo structure:
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 2.1 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 2.2, pr_policy has For using the Priority Policy described in Section 3.2, pr_policy has
the value SCTP_PR_SCTP_PRIO. The priority is given in pr_value. The 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 value of zero is the highest priority and larger numbers in pr_value
denote lower priorities. 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 2.1 | | SCTP_PR_SCTP_RTX | Number of retransmissions | Section 3.1 |
| SCTP_PR_SCTP_PRIO | Priority | Section 2.2 | | SCTP_PR_SCTP_PRIO | Priority | Section 3.2 |
+-------------------+---------------------------+---------------+ +-------------------+---------------------------+---------------+
3.3. Socket Option for Getting the PR-SCTP Status (SCTP_PR_STATUS) 4.3. Socket Option for Getting the PR-SCTP Status (SCTP_PR_STATUS)
This socket option uses IPPROTO_SCTP as its level and SCTP_PR_STATUS This socket option uses IPPROTO_SCTP as its level and SCTP_PR_STATUS
as its name. It can only be used with getsockopt(), but not with as its name. It can only be used with getsockopt(), but not with
setsockopt(). The socket option value uses the following structure: setsockopt(). The socket option value uses the following structure:
struct sctp_prstatus { struct sctp_prstatus {
sctp_assoc_t sprstat_assoc_id; sctp_assoc_t sprstat_assoc_id;
uint64_t sprstat_abandoned_unsent; uint64_t sprstat_abandoned_unsent;
uint64_t sprstat_abandoned_sent; uint64_t sprstat_abandoned_sent;
}; };
skipping to change at page 5, line 29 skipping to change at page 6, line 5
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. recommended.
sctp_opt_info() needs to be extended to support SCTP_PR_STATUS. sctp_opt_info() needs to be extended to support SCTP_PR_STATUS.
3.4. Socket Option for Getting and Setting the PR-SCTP Support 4.4. Socket Option for Getting and Setting the PR-SCTP Support
(SCTP_PR_SUPPORTED) (SCTP_PR_SUPPORTED)
This socket option allows the enabling or disabling of the This socket option allows the enabling or disabling of the
negotiation of PR-SCTP support for future associations. For existing negotiation of PR-SCTP support for future associations. For existing
associations it allows to query whether PR-SCTP support was associations it allows to query whether PR-SCTP support was
negotiated or not on particular associations. negotiated or not on particular associations.
Whether PR-SCTP is enabled or not per default is implementation Whether PR-SCTP is enabled or not per default is implementation
specific. specific.
skipping to change at page 6, line 13 skipping to change at page 6, line 37
For one-to-many style sockets, this parameter indicates upon which For one-to-many style sockets, this parameter indicates upon which
association the user is performing an action. The special association the user is performing an action. The special
sctp_assoc_t SCTP_FUTURE_ASSOC can also be used, it is an error to sctp_assoc_t SCTP_FUTURE_ASSOC can also be used, it is an error to
use SCTP_{CURRENT|ALL}_ASSOC in assoc_id. use SCTP_{CURRENT|ALL}_ASSOC in assoc_id.
assoc_value: A non-zero value encodes the enabling of PR-SCTP assoc_value: A non-zero value encodes the enabling of PR-SCTP
whereas a value of 0 encodes the disabling of PR-SCTP. whereas a value of 0 encodes the disabling of PR-SCTP.
sctp_opt_info() needs to be extended to support SCTP_PR_SUPPORTED. sctp_opt_info() needs to be extended to support SCTP_PR_SUPPORTED.
4. IANA Considerations 5. IANA Considerations
This document requires no actions from IANA. This document requires no actions from IANA.
5. 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
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
instead. It should also be noted that using PR-SCTP for an SCTP
association doesn't allow that association to behave more
aggressively congestion-control wise than an SCTP association not
using PR-SCTP.
6. Acknowledgments 7. Acknowledgments
The authors wish to thank Karen Egede Nielsen, Ka-Cheong Poon, Irene The authors wish to thank Gorry Fairhurst, Karen Egede Nielsen, Ka-
Ruengeler, Jamal Hadi Salim, and Vlad Yasevich for their invaluable Cheong Poon, Irene Ruengeler, Jamal Hadi Salim, and Vlad Yasevich for
comments. their invaluable comments.
7. References 8. References
7.1. Normative References 8.1. 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. [RFC3758] Stewart, R., Ramalho, M., Xie, Q., Tuexen, M., and P.
Conrad, "Stream Control Transmission Protocol (SCTP) Conrad, "Stream Control Transmission Protocol (SCTP)
Partial Reliability Extension", RFC 3758, May 2004. Partial Reliability Extension", RFC 3758, May 2004.
[RFC4960] Stewart, R., "Stream Control Transmission Protocol", RFC [RFC4960] Stewart, R., "Stream Control Transmission Protocol", RFC
4960, September 2007. 4960, September 2007.
7.2. Informative References 8.2. Informative References
[RFC3436] Jungmaier, A., Rescorla, E., and M. Tuexen, "Transport
Layer Security over Stream Control Transmission Protocol",
RFC 3436, December 2002.
[RFC6083] Tuexen, M., Seggelmann, R., and E. Rescorla, "Datagram
Transport Layer Security (DTLS) for Stream Control
Transmission Protocol (SCTP)", RFC 6083, January 2011.
[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.
[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]
Jesup, R., Loreto, S., and M. Tuexen, "WebRTC Data
Channels", draft-ietf-rtcweb-data-channel-09 (work in
progress), May 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
Stegerwaldstrasse 39 Stegerwaldstrasse 39
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