Network Working Group S. Bailey
Request for Comments: 4296 Sandburst
Category: Informational T. Talpey
NetApp
December 2005
The Architecture of Direct Data Placement (DDP)
and Remote Direct Memory Access (RDMA) on Internet Protocols
Status of This Memo
This memo provides information for the Internet community. It does
not specify an Internet standard of any kind. Distribution of this
memo is unlimited.
Copyright Notice
Copyright (C) The Internet Society (2005).
Abstract
This document defines an abstract architecture for Direct Data
Placement (DDP) and Remote Direct Memory Access (RDMA) protocols to
run on Internet Protocol-suite transports. This architecture does
not necessarily reflect the proper way to implement such protocols,
but is, rather, a descriptive tool for defining and understanding the
protocols. DDP allows the efficient placement of data into buffers
designated by Upper Layer Protocols (e.g., RDMA). RDMA provides the
semantics to enable Remote Direct Memory Access between peers in a
way consistent with application requirements.
Bailey & Talpey Informational [Page 1]RFC 4296 DDP and RDMA Architecture December 2005Table of Contents
1. Introduction ....................................................2
1.1. Terminology ................................................2
1.2. DDP and RDMA Protocols .....................................3
2. Architecture ....................................................4
2.1. Direct Data Placement (DDP) Protocol Architecture ..........4
2.1.1. Transport Operations ................................6
2.1.2. DDP Operations ......................................7
2.1.3. Transport Characteristics in DDP ...................10
2.2. Remote Direct Memory Access (RDMA) Protocol Architecture ..12
2.2.1. RDMA Operations ....................................14
2.2.2. Transport Characteristics in RDMA ..................16
3. Security Considerations ........................................17
3.1. Security Services .........................................18
3.2. Error Considerations ......................................19
4. Acknowledgements ...............................................19
5. Informative References .........................................20
1. Introduction
This document defines an abstract architecture for Direct Data
Placement (DDP) and Remote Direct Memory Access (RDMA) protocols to
run on Internet Protocol-suite transports. This architecture does
not necessarily reflect the proper way to implement such protocols,
but is, rather, a descriptive tool for defining and understanding the
protocols. This document uses C language notation as a shorthand to
describe the architectural elements of DDP and RDMA protocols. The
choice of C notation is not intended to describe concrete protocols
or programming interfaces.
The first part of the document describes the architecture of DDP
protocols, including what assumptions are made about the transports
on which DDP is built. The second part describes the architecture of
RDMA protocols layered on top of DDP.
1.1. Terminology
Before introducing the protocols, certain definitions will be useful
to guide discussion:
o Placement - writing to a data buffer.
o Operation - a protocol message, or sequence of messages, which
provide an architectural semantic, such as reading or writing of
a data buffer.
Bailey & Talpey Informational [Page 2]RFC 4296 DDP and RDMA Architecture December 2005
o Delivery - informing any Upper Layer or application that a
particular message is available for use. Therefore, delivery
may be viewed as the "control" signal associated with a unit of
data. Note that the order of delivery is defined more strictly
than it is for placement.
o Completion - informing any Upper Layer or application that a
particular operation has finished. A completion, for instance,
may require the delivery of several messages, or it may also
reflect that some local processing has finished.
o Data Sink - the peer on which any placement occurs.
o Data Source - the peer from which the placed data originates.
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