draft-ietf-tsvwg-sctp-sack-immediately-03.txt   draft-ietf-tsvwg-sctp-sack-immediately-04.txt 
Network Working Group M. Tuexen Network Working Group M. Tuexen
Internet-Draft I. Ruengeler Internet-Draft I. Ruengeler
Updates: 4960 (if approved) Muenster Univ. of Appl. Sciences Updates: 4960 (if approved) Muenster Univ. of Appl. Sciences
Intended status: Standards Track R. R. Stewart Intended status: Standards Track R. Stewart
Expires: October 10, 2013 Adara Networks Expires: March 01, 2014 Adara Networks
April 08, 2013 August 28, 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-03.txt draft-ietf-tsvwg-sctp-sack-immediately-04.txt
Abstract Abstract
This document updates RFC 4960 by defining a method for the sender of This document updates RFC 4960 by defining a method for the sender of
a DATA chunk to indicate that the corresponding SACK chunk should be a DATA chunk to indicate that the corresponding SACK chunk should be
sent back immediately and not be delayed. It is done by specifying a sent back immediately and not be delayed. It is done by specifying a
bit in the DATA chunk header, called the I-bit, which can get set bit in the DATA chunk header, called the I-bit, which can get set
either by the SCTP implementation or by the application using an SCTP either by the SCTP implementation or by the application using an SCTP
stack. Since unknown flags in chunk headers are ignored by SCTP stack. Since unknown flags in chunk headers are ignored by SCTP
implementations, this extension does not introduce any implementations, this extension does not introduce any
skipping to change at page 1, line 39 skipping to change at page 1, line 39
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
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This Internet-Draft will expire on October 10, 2013. This Internet-Draft will expire on March 01, 2014.
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
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the Trust Legal Provisions and are provided without warranty as the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License. described in the Simplified BSD License.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Conventions . . . . . . . . . . . . . . . . . . . . . . . . . 2 2. Conventions . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. The I-bit in the DATA Chunk Header . . . . . . . . . . . . . 3 3. The I-bit in the DATA Chunk Header . . . . . . . . . . . . . 3
4. Use Cases . . . . . . . . . . . . . . . . . . . . . . . . . . 3 4. Use Cases . . . . . . . . . . . . . . . . . . . . . . . . . . 4
4.1. Triggering at the Application Level . . . . . . . . . . . 3 4.1. Triggering at the Application Level . . . . . . . . . . . 4
4.2. Triggering at the SCTP Level . . . . . . . . . . . . . . 4 4.2. Triggering at the SCTP Level . . . . . . . . . . . . . . 4
5. Procedures . . . . . . . . . . . . . . . . . . . . . . . . . 4 5. Procedures . . . . . . . . . . . . . . . . . . . . . . . . . 4
5.1. Sender Side Considerations . . . . . . . . . . . . . . . 4 5.1. Sender Side Considerations . . . . . . . . . . . . . . . 5
5.2. Receiver Side Considerations . . . . . . . . . . . . . . 5 5.2. Receiver Side Considerations . . . . . . . . . . . . . . 5
6. Interoperability Considerations . . . . . . . . . . . . . . . 5 6. Interoperability Considerations . . . . . . . . . . . . . . . 5
7. Socket API Considerations . . . . . . . . . . . . . . . . . . 5 7. Socket API Considerations . . . . . . . . . . . . . . . . . . 5
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6
9. Security Considerations . . . . . . . . . . . . . . . . . . . 6 9. Security Considerations . . . . . . . . . . . . . . . . . . . 7
10. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 6 10. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 7
11. References . . . . . . . . . . . . . . . . . . . . . . . . . 6 11. References . . . . . . . . . . . . . . . . . . . . . . . . . 7
11.1. Normative References . . . . . . . . . . . . . . . . . . 6 11.1. Normative References . . . . . . . . . . . . . . . . . . 7
11.2. Informative References . . . . . . . . . . . . . . . . . 7 11.2. Informative References . . . . . . . . . . . . . . . . . 7
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 7 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 7
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 default behavior. receiver of the DATA chunk and remains the default 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:
the receiver, the corresponding SACK can be sent immediately. For
example, [RFC4960] recommends the immediate sending if the receiver
has detected message loss or message duplication. However, if the
situation can only be detected by the sender of the DATA chunk,
[RFC4960] provides no method of avoiding a delay in sending the SACK.
This document describes a simple extension of the SCTP DATA chunk by 1. If such a situation can be detected by the receiver, the
corresponding SACK can be sent immediately. For example,
[RFC4960] recommends the immediate sending if the receiver has
detected message loss or message duplication.
2. However, if the situation can only be detected by the sender of
the DATA chunk, [RFC4960] provides no method of avoiding a delay
in sending the SACK. Examples of these situations include ones
which require interaction with the application (e.g. applications
using the SCTP_SENDER_DRY_EVENT, see Section 4.1) and ones which
can be detected by the SCTP stack itself (e.g. closing the
association, hitting window limits or resetting streams, see
Section 4.2).
To overcome the limitation described in the second case, this
document describes a simple extension of the SCTP DATA chunk by
defining a new flag, the I-bit. The sender of a DATA chunk indicates defining a new flag, the I-bit. The sender of a DATA chunk indicates
by setting this bit that the corresponding SACK chunk should not be by setting this bit that the corresponding SACK chunk should not be
delayed. Use-cases are described in Section 4. delayed.
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.
0 1 2 3 0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
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See [RFC4960] for general security considerations for SCTP. In See [RFC4960] for general security considerations for SCTP. In
addition, a malicious sender can force its peer to send packets addition, a malicious sender can force its peer to send packets
containing a SACK chunk for each received packet containing DATA containing a SACK chunk for each received packet containing DATA
chunks instead of every other. This could impact the network, chunks instead of every other. This could impact the network,
resulting in more packets sent on the network, or the peer because resulting in more packets sent on the network, or the peer because
the generating and sending of the packets has some processing cost. the generating and sending of the packets has some processing cost.
However, the additional packets can only contain the most simplest However, the additional packets can only contain the most simplest
SACK chunk (no gap reports, no duplicate TSNs), since in case of 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 packet drop or reordering in the network a SACK chunk would be sent
immediately anyway. Therefore this does neither introduce a immediately anyway. Therefore this does neither introduce a
significant additional processing cost on the receiver side nor does significant additional processing cost on the receiver side. This
it cause congestion on the network. does not result in more traffic in the network than a receiver that
sends a SACK for every packet, which is already permitted.
10. Acknowledgments 10. Acknowledgments
The authors wish to thank Mark Allmann, Brian Bidulock, David Black, The authors wish to thank Mark Allmann, Brian Bidulock, David Black,
Anna Brunstrom, Gorry Fairhurst, Janardhan Iyengar, Kacheong Poon, Anna Brunstrom, Gorry Fairhurst, Janardhan Iyengar, Kacheong Poon,
and Michael Welzl for their invaluable comments. and Michael Welzl for their invaluable comments.
11. References 11. References
11.1. Normative References 11.1. Normative References
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