Network Working Group R. Stewart
Internet-Draft Cisco Systems, Inc.
Expires: April 1, 2003 October 1, 2002
Stream Control Transmission Protocol (SCTP) Remote Direct Memory
Access (RDMA) Direct Data Placement (DDP) Adaption
draft-stewart-rddp-sctp-00.txt
Status of this Memo
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Copyright Notice
Copyright (C) The Internet Society (2002). All Rights Reserved.
Abstract
This document describes a method to adapt Direct Data Placment (DDP)
and Remote Direct Memory Access (RDMA) to Stream Control Transmission
Protocol (SCTP) RFC2960 [2] using a generic description found in
[RDMA-Draft] [4] and [DDP-Draft] [3] This adaption provides a method
for two peers to know that each side is performing DDP or RDMA thus
enabling hardware acceleration if available.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1 Conventions . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Adaptation Layer Indicator . . . . . . . . . . . . . . . . . . 4
3. Procedures . . . . . . . . . . . . . . . . . . . . . . . . . . 5
3.1 Association Initialization . . . . . . . . . . . . . . . . . . 5
3.2 RDMA and DDP Placement behavior with SCTP . . . . . . . . . . 6
4. IANA considerations . . . . . . . . . . . . . . . . . . . . . 7
5. Security Considerations . . . . . . . . . . . . . . . . . . . 8
6. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 9
References . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Author's Address . . . . . . . . . . . . . . . . . . . . . . . 10
Full Copyright Statement . . . . . . . . . . . . . . . . . . . 11
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1. Introduction
This document describes a method to adapt Direct Data Placment (DDP)
and Remote Direct Memory Access (RDMA) to Stream Control Transmission
Protocol (SCTP) RFC2960 [2] using a generic description found in
[RDMA-Draft] [4] and [DDP-Draft] [3] This adaption provides a method
for two peers to know that each side is performing DDP or RDMA thus
enabling hardware acceleration if available.
Some implementations may include this adaptation layer within their
SCTP implementations to obtain maximum performance but the behavior
of SCTP will be unaffected. In order to accomplish this we specify
the use of the new adaptation layer indication as defined in [ADDIP-
Draft] [6]
1.1 Conventions
The keywords MUST, MUST NOT, REQUIRED, SHALL, SHALL NOT, SHOULD,
SHOULD NOT, RECOMMENDED, NOT RECOMMENDED, MAY, and OPTIONAL, when
they appear in this document, are to be interpreted as described in
RFC2119 [1].
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2. Adaptation Layer Indicator
We define a adaption indication which MUST appear in the INIT or
INIT-ACK with the following format as defined in [ADDIP-Draft] [6]
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type =0xC006 | Length = Variable |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Adaptation Indication |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Adaptation Indication:
The following value is defined for DDP in this document:
RDMA - 0x00000001
RDMA+DDP - 0x00000002
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3. Procedures
3.1 Association Initialization
At the startup of an association, an endpoint wishing to perform DDP,
RDMA, or DDP+RDMA placement MUST include an adaptation layer
indication in its INIT or INIT-ACK (as defined in 2.1). After the
exchange of the first two messages (INIT and INIT-ACK), an endpoint
MUST verify and inspect the adaptation indication and compare it to
the following table to determine proper action.
Indication | Action
type |
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
| This indicates that the peer DOES NOT
NONE | support ANY DDP or RDMA adaption and thus
| RDMA and DDP procedures MUST NOT be
| performed upon this association.
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
| This indicates that the peer DOES support
RDMA | RDMA (but not DDP). Procedures outlined in
| [RDMA-Draft] MUST be followed.
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
| This indicates that the peer supports BOTH
DDP+RDMA | RDMA and DDP. If the receiving endpoint
| indicated the same, then the procedures in
| both [RDMA-Draft] and [DDP-Draft]
| MUST be followed. If the local endpoint only indicated
| RDMA, then ONLY the procedures in
| [RDMA-Draft] MUST be followed.
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
| This indicates that the peer DOES NOT
ANY-OTHER | support ANY DDP or RDMA adaption and thus
Indication | RDMA and DDP procedures MUST NOT be
| performed upon this association.
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Editors Notes/Questions:
1. Do we need to have a control channel, stream 0 for instance?
2. Do we need to dictate control messages that can be sent back to
negotiate different aspects?
3. If we do this do we even need DDP, just have RDMA and then
negotiate things from there?
4. Do we need to better describe how to use unordered data with the
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TSN and the CUM-ACK out of the sockets-api?
If the endpoints agree to use either DDP or RDMA each endpoint MUST
enable the SCTP_DISABLE_FRAGMENTS option as defined in [Sctpsockets-
Draft] [5].
3.2 RDMA and DDP Placement behavior with SCTP
When RDMA or DDP is used in combination with SCTP no further
procedures are needed other than both endpoints knowing that
specialized placement is occurring. SCTP, once the
SCTP_DISABLE_FRAGMENTS option is set, will always assure that EACH
send message fits in one complete SCTP chunk. The receiver will NOT
need to be concerned with message boundaries and loss events since
each SCTP DATA chunk will always have the BE bits set. The placement
algorithm will only need to look into the bytes described in their
respective drafts and follow those procedures to perform RDMA or DDP.
If the sender specifies Unordered delivery (by setting the U bit) the
receiver, after placement, MAY notify the receiving application that
the data has arrived. The cumulative TSN and TSN values defined in
[Sctpsockets-Draft] [5] can be used to determine if data is ready to
be delivered to upper layer protocols.
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4. IANA considerations
This document defines two new Adaptation Layer Indication codepoints:
RDMA - 0x00000001
RDMA+DDP - 0x00000002
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5. Security Considerations
Any direct placement of memory poses a significant security risk,
these threats should be addressed in the appropriate DDP [DDP-Draft]
[3] or RDMA [RDMA-Draft] [4] drafts. This document does not add any
additional security risks over those found in RFC2960 [2].
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6. Acknowledgments
The author would like to thank the following people that have
provided comments and input Stephen Bailey, David Black, Caitlin
Bestler,Douglas Otis, and Allyn Romanow.
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References
[1] Bradner, S., "Key words for use in RFCs to Indicate Requirement
Levels", BCP 14, RFC 2119, March 1997.
[2] Stewart, R., Xie, Q., Morneault, K., Sharp, C., Schwarzbauer,
H., Taylor, T., Rytina, I., Kalla, M., Zhang, L. and V. Paxson,
"Stream Control Transmission Protocol", RFC 2960, October 2000.
[3] Culley, P., "Direct Data Placement over Reliable Transports",
draft-shah-iwarp-ddp-00 (work in progress), September 2002.
[4] Recio, R., Garcia, D. and P. Culley, "An RDMA Protocol
Specification", draft-recio-iwarp-rdma-00 (work in progress),
September 2002.
[5] Stewart, R., "Sockets API Extensions for Stream Control
Transmission Protocol", draft-ietf-tsvwg-sctpsocket-05 (work in
progress), September 2002.
[6] Stewart, R., "Stream Control Transmission Protocol (SCTP)
Dynamic Address Reconfiguration", draft-ietf-tsvwg-addip-sctp-
06 (work in progress), September 2002.
Author's Address
Randall R. Stewart
Cisco Systems, Inc.
8725 West Higgins Road
Suite 300
Chicago, IL 60631
USA
Phone: +1-815-477-2127
EMail: rrs@cisco.com
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