draft-ietf-tsvwg-sctp-sack-immediately-01.txt   draft-ietf-tsvwg-sctp-sack-immediately-02.txt 
Network Working Group M. Tuexen Network Working Group M. Tuexen
Internet-Draft I. Ruengeler Internet-Draft I. Ruengeler
Intended status: Standards Track Muenster Univ. of Appl. Sciences Updates: 4960 (if approved) Muenster Univ. of Appl. Sciences
Expires: September 15, 2013 R. R. Stewart Intended status: Standards Track R. R. Stewart
Adara Networks Expires: September 17, 2013 Adara Networks
March 14, 2013 March 16, 2013
SACK-IMMEDIATELY Extension for the Stream Control Transmission Protocol SACK-IMMEDIATELY Extension for the Stream Control Transmission Protocol
draft-ietf-tsvwg-sctp-sack-immediately-01.txt draft-ietf-tsvwg-sctp-sack-immediately-02.txt
Abstract Abstract
This document defines a method for the sender of a DATA chunk to This document updates RFC 4960 by defining a method for the sender of
indicate that the corresponding SACK chunk should be sent back a DATA chunk to indicate that the corresponding SACK chunk should be
immediately and not be delayed. It is done by specifying a bit in sent back immediately and not be delayed. It is done by specifying a
the DATA chunk header, called the I-bit, which can get set either by bit in the DATA chunk header, called the I-bit, which can get set
the SCTP implementation or by the application using an SCTP stack. either by the SCTP implementation or by the application using an SCTP
stack. Since unknown flags in chunk headers are ignored by SCTP
implementations, this extension does not introduce any
interoperability problems.
Status of This Memo Status of This Memo
This Internet-Draft is submitted in full conformance with the This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79. provisions of BCP 78 and BCP 79.
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-
Drafts is at http://datatracker.ietf.org/drafts/current/. Drafts is at http://datatracker.ietf.org/drafts/current/.
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 September 15, 2013. This Internet-Draft will expire on September 17, 2013.
Copyright Notice Copyright Notice
Copyright (c) 2013 IETF Trust and the persons identified as the Copyright (c) 2013 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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10. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 6 10. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 6
11. References . . . . . . . . . . . . . . . . . . . . . . . . . 6 11. References . . . . . . . . . . . . . . . . . . . . . . . . . 6
11.1. Normative References . . . . . . . . . . . . . . . . . . 6 11.1. Normative References . . . . . . . . . . . . . . . . . . 6
11.2. Informative References . . . . . . . . . . . . . . . . . 6 11.2. Informative References . . . . . . . . . . . . . . . . . 6
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 6 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 6
1. Introduction 1. Introduction
According to [RFC4960] the receiver of a DATA chunk should use According to [RFC4960] the receiver of a DATA chunk should use
delayed SACKs. This delaying is completely controlled by the delayed SACKs. This delaying is completely controlled by the
receiver of the DATA chunk and remains the to be the default receiver of the DATA chunk and remains the default behavior.
behavior.
In specific situations the delaying of SACKs results in reduced In specific situations the delaying of SACKs results in reduced
performance of the protocol. If such a situation can be detected by performance of the protocol. If such a situation can be detected by
the receiver, the corresponding SACK can be sent immediately. For the receiver, the corresponding SACK can be sent immediately. For
example, [RFC4960] recommends the immediate sending if the receiver example, [RFC4960] recommends the immediate sending if the receiver
has detected message loss or message duplication. However, if the has detected message loss or message duplication. However, if the
situation can only be detected by the sender of the DATA chunk, situation can only be detected by the sender of the DATA chunk,
[RFC4960] provides no method of avoiding the delaying of the SACK. [RFC4960] provides no method of avoiding a delay in sending the SACK.
Thus the protocol performance might be reduced.
This document overcomes this limitation and describes a simple This document describes a simple extension of the SCTP DATA chunk by
extension of the SCTP DATA chunk by defining a new flag, the I-bit. defining a new flag, the I-bit. The sender of a DATA chunk indicates
The sender of a DATA chunk indicates by setting this bit that the by setting this bit that the corresponding SACK chunk should not be
corresponding SACK chunk should not be delayed. Use-cases are delayed. Use-cases are described in Section 4.
described in Section 4.
2. Conventions 2. Conventions
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119]. document are to be interpreted as described in [RFC2119].
3. The I-bit in the DATA Chunk Header 3. The I-bit in the DATA Chunk Header
The following Figure 1 shows the extended DATA chunk. The following Figure 1 shows the extended DATA chunk.
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able to handle this case, there is no requirement for negotiating the able to handle this case, there is no requirement for negotiating the
support of the feature described in this document. support of the feature described in this document.
7. Socket API Considerations 7. 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 provide a way for the application to set the I-bit. extended to provide a way for the application to set the I-bit.
Please note that this section is informational only. Please note that this section is informational only.
A socket API implementation based on [RFC6458] is extended to allow A socket API implementation based on [RFC6458] needs to be extended
the application to set the I-bit of the last DATA chunk for each to allow the application to set the I-bit of the last DATA chunk when
provided user message. sending each user message.
This can be done by setting a flag called SCTP_SACK_IMMEDIATELY in This can be done by setting a flag called SCTP_SACK_IMMEDIATELY in
the snd_flags field of the struct sctp_sndinfo structure when using the snd_flags field of the struct sctp_sndinfo structure when using
sctp_sendv() or sendmsg(). If the deprecated struct sctp_sndrcvinfo sctp_sendv() or sendmsg(). If the deprecated struct sctp_sndrcvinfo
structure is used instead when calling sctp_send(), sctp_sendx(), or structure is used instead when calling sctp_send(), sctp_sendx(), or
sendmsg(), the SCTP_SACK_IMMEDIATELY flags can be set in the sendmsg(), the SCTP_SACK_IMMEDIATELY flags can be set in the
sinfo_flags field. When using the deprecated function sctp_sendmsg() sinfo_flags field. When using the deprecated function sctp_sendmsg()
the SCTP_SACK_IMMEDIATELY flag can be in the flags parameter. the SCTP_SACK_IMMEDIATELY flag can be in the flags parameter.
8. IANA Considerations 8. IANA Considerations
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] ]
Following the chunk flag registration procedure defined in [RFC6096] Following the chunk flag registration procedure defined in [RFC6096]
IANA should register a new bit, the I-bit, for the DATA chunk. The IANA should register a new bit, the I-bit, for the DATA chunk. The
suggested value is 0x08. The reference for the new chunk flag in the suggested value is 0x08. The reference for the new chunk flag in the
chunk flags table for the DATA chunk should be RFCXXXX. chunk flags table for the DATA chunk should be RFCXXXX.
9. Security Considerations 9. 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] and [RFC6458]. It should be addition to the ones given in [RFC4960]. It should be noted that a
noted that an malicious sender can force its peer to send packets malicious sender can force its peer to send packets containing a SACK
containing SACK chunks for each received packet containing DATA chunk for each received packet containing DATA chunks instead of
chunks instead of every other. However, every receiver has to be every other. This could impact the network, resulting in more
able to do this anyway. It might be configured to do so or has to do packets sent on the network, or the peer because the generating and
this because of packet loss or reordering in the network. sending of the packets has some processing cost. However, the
additional packets can only contain the most simplest SACK chunk (no
gap reports, no duplicate TSNs), since in case of packet drop or
reordering in the network a SACK chunk would be sent immediately
anyway. Therefore this does neither introduce a significant
additional processing cost on the receiver side nor does it cause
congestion on the network.
10. Acknowledgments 10. Acknowledgments
The authors wish to thank Mark Allmann, Brian Bidulock, Gorry The authors wish to thank Mark Allmann, Brian Bidulock, Gorry
Fairhurst, Janardhan Iyengar, and Kacheong Poon for their invaluable Fairhurst, Janardhan Iyengar, and Kacheong Poon for their invaluable
comments. comments.
11. References 11. References
11.1. Normative References 11.1. Normative References
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