Internet DRAFT - draft-ietf-storm-rdmap-ext
draft-ietf-storm-rdmap-ext
Storage Maintenance (storm) Working Group Hemal Shah
Internet Draft Broadcom Corporation
Intended status: Standards Track Felix Marti
Expires: October 2014 Wael Noureddine
Asgeir Eiriksson
Chelsio Communications, Inc.
Robert Sharp
Intel Corporation
April 16, 2014
RDMA Protocol Extensions
draft-ietf-storm-rdmap-ext-10.txt
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Abstract
This document specifies extensions to the IETF Remote Direct Memory
Access Protocol (RDMAP RFC5040). RDMAP provides read and write
services directly to applications and enables data to be transferred
directly into Upper Layer Protocol (ULP) Buffers without
intermediate data copies. The extensions specified in this document
provide the following capabilities and/or improvements: Atomic
Operations and Immediate Data.
Table of Contents
1. Introduction...................................................3
1.1. Discovery of RDMAP Extensions.............................4
2. Requirements Language..........................................5
3. Glossary.......................................................5
4. Header Format Extensions.......................................7
4.1. RDMAP Control and Invalidate STag Fields..................7
4.2. RDMA Message Definitions..................................9
5. Atomic Operations..............................................9
5.1. Atomic Operation Details.................................11
5.1.1. FetchAdd............................................11
5.1.2. CmpSwap.............................................12
5.2. Atomic Operations........................................14
5.2.1. Atomic Operation Request Message....................14
5.2.2. Atomic Operation Response Message...................18
5.3. Atomicity Guarantees.....................................19
5.4. Atomic Operations Ordering and Completion Rules..........19
6. Immediate Data................................................21
6.1. RDMAP Interactions with ULP for Immediate Data...........21
6.2. Immediate Data Header Format.............................22
6.3. Immediate Data or Immediate Data with SE Message.........22
6.4. Ordering and Completions.................................23
7. Ordering and Completions Table................................23
8. Error Processing..............................................26
8.1. Errors Detected at the Local Peer........................26
8.2. Errors Detected at the Remote Peer.......................27
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9. Security Considerations.......................................28
10. IANA Considerations..........................................28
10.1. RDMAP Message Atomic Operation Subcodes.................28
10.2. RDMAP Queue Numbers.....................................29
11. References...................................................30
11.1. Normative References....................................30
11.2. Informative References..................................31
12. Acknowledgments..............................................32
Appendix A. DDP Segment Formats for RDMA Messages................33
A.1. DDP Segment for Atomic Operation Request.................33
A.2. DDP Segment for Atomic Response..........................35
A.3. DDP Segment for Immediate Data and Immediate Data with SE35
1. Introduction
The RDMA Protocol [RFC5040] provides capabilities for zero copy data
communications that preserve memory protection semantics, enabling
more efficient network protocol implementations. The RDMA Protocol
is part of the iWARP family of specifications which also include RFC
5041 [RFC5041], RFC 5044 [RFC5044], and RFC 6581 [RFC6581]. This
document specifies the following extensions to the RDMA Protocol
(RDMAP):
o Atomic operations on remote memory locations. Support for atomic
operation enhances the usability of RDMAP in distributed shared
memory environments.
o Immediate Data messages allow the ULP at the sender to provide a
small amount of data. When an Immediate Data message is sent
following an RDMA Write Message, the combination of the two
messages is an implementation of RDMA Write with Immediate
message that is found in other RDMA transport protocols.
Other RDMA transport protocols define the functionality added by
these extensions leading to differences in RDMA applications and/or
Upper Layer Protocols. Removing these differences in the transport
protocols simplifies these applications and ULPs and that is the
main motivation for the extensions specified in this document.
RSockets [RSOCKETS] is an example of RDMA enabled middleware that
provides a socket interface as the upper edge interface and utilizes
RDMA to provide more efficient networking for sockets based
applications. RSockets is aware of Immediate Data support in
InfiniBand [IB]. RSockets cannot utilize the RDMA Write with
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Immediate Data operation from InfiniBand . The addition of the
Immediate Data operation specified in this draft will alleviate this
difference in RSockets when running on InfiniBand and iWARP.
Structured high performance computing applications based on the MPI
interface [MPI] may use Atomic Operations defined in this
specification. DAT Atomics [DAT_ATOMICS] is an example of RDMA
enabled middleware that provides a portable RDMA programming
interface for various RDMA transport protocols. DAT Atomics
includes a primitive for InfiniBand that is not supported by iWARP
RDMA Network Interface Controllers or RNICs. The addition of Atomic
Operations as specified in this draft will allow atomic operations
in DAT Atomics to work for both InfiniBand and RNICs
interchangeably.
For more background on RDMA Protocol applicability, see
Applicability of Remote Direct Memory Access Protocol (RDMA) and
Direct Data Placement Protocol (DDP) [RFC5045].
1.1. Discovery of RDMAP Extensions
Today there are RDMA applications and/or ULPs that are aware of the
existence of Atomic and Immediate data operations for RDMA
transports such as InfiniBand and application programming interfaces
such as Open Fabrics Verbs [OFAVERBS]. Today, these applications
need to be aware that RDMAP does not support certain of these
operations. Typically the availability of these capabilities is
exposed to the applications through adapter query interfaces in
software. Applications then have to decide to use or not to use
Immediate Data or Atomic Operations based on the results of the
query interfaces. Such query interfaces typically return the scope
of atomicity guarantees, not the individual Atomic Operations
supported. Therefore, this specification requires all Atomic
Operations defined within to be supported if an RNIC supports any
Atomic Operations.
In cases where heterogeneous hardware, with differing support for
Atomic Operations and Immediate Data Operations, is deployed for use
by RDMA applications and/or ULPs, applications are either statically
configured to use or not use optional features or use application
specific negotiation mechanisms. For the extensions covered by this
document, it is RECOMMENDED that RDMA applications and/or ULPs
negotiate at the application or ULP level the usage of these
extensions. The definition of such application specific mechanism
is outside the scope of this specification. For backward
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compatibility, existing applications and/or ULPs should not assume
that these extensions are supported.
In the absence of application specific negotiation of the features
defined within this specification, the new operations can be
attempted and reported errors can be used to determine a remote
peer's capabilities. In the case of Atomics, a FetchAdd operation
with Add Data set to 0 can safely be used to determine the existence
of Atomic Operations without modifying the content of a remote
peer's memory. A Remote Operation Error / Unexpected OpCode error
will be reported by the remote peer in the case of an Immediate Data
or Atomic Operation as described if not supported by the remote
peer.
2. Requirements Language
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 RFC-2119 [RFC2119].
3. Glossary
This document is an extension of RFC 5040 and key words are defined
in the glossary of the referenced document.
Atomic Operation - is an operation that results in an execution of a
memory operation at a specific ULP Buffer address on a remote node
using the Tagged Buffer data transfer model. The consumer can use
Atomic Operations to read, modify and write memory at the
destination ULP Buffer address while at the same time guaranteeing
that no other Atomic Operation read or write accesses to the ULP
Buffer address targeted by the Atomic Operation will occur across
any other RDMAP Streams on an RNIC at the Responder.
Atomic Operation Request - An RDMA Message used by the Data Source
to perform an Atomic Operation at the Responder.
Atomic Operation Response - An RDMA Message used by the Responder to
describe the completion of an Atomic Operation at the Responder.
CmpSwap - is an Atomic Operation that is used to compare and swap a
value at a specific address on a remote node.
FetchAdd - is an Atomic Operation that is used to atomically
increment a value at a specific ULP Buffer address on a remote node.
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Immediate Data - a small fixed size portion of data sent from the
Data Source to a Data Sink
Immediate Data Message - An RDMA Message used by the Data Source to
send Immediate Data to the Data Sink
Immediate Data with Solicited Event (SE) Message - An RDMA Message
used by the Data Source to send Immediate Data with Solicited Event
to the Data Sink
iWARP - A suite of wire protocols comprised of RFC 5040, RFC 5041,
RFC 5044, and RFC 6581.
Requester - the sender of an RDMA Atomic Operation request.
Responder - the receiver of an RDMA Atomic Operation request.
RNIC - RDMA Network Interface Controller. In this context, this
would be a network I/O adapter or embedded controller with iWARP
functionality.
ULP - Upper Layer Protocol. The protocol layer above the one
currently being referenced. The ULP for RFC 5040 / RFC 5041 is
expected to be an OS, Application, adaptation layer, or proprietary
device. The RFC 5040 / RFC 5041 documents do not specify a ULP --
they provide a set of semantics that allow a ULP to be designed to
utilize RFC 5040 / RFC 5041.
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4. Header Format Extensions
The control information of RDMA Messages is included in DDP protocol
RFC 5041 defined header fields. RFC 5040 defines the RDMAP header
formats layered on the DDP header definition. This specification
extends RFC 5040 with the following new formats:
. Four new RDMA Messages carry additional RDMAP headers. The
Immediate Data operation and Immediate Data with Solicited Event
operation include 8 bytes of data following the RDMAP header.
Atomic Operations include Atomic Request or Atomic Response
headers following the RDMAP header. The RDMAP header for Atomic
Request messages is 52 bytes long as specified in Figure 4. The
RDMAP header for Atomic Response Messages is 32 bytes long as
specified in Figure 5.
. Introduction of a new queue for untagged buffers (QN=3) used for
Atomic Response tracking.
4.1. RDMAP Control and Invalidate STag Fields
For reference, Figure 1 depicts the format of the DDP Control and
RDMAP Control fields, in the style and convention of RFC 5040:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|T|L| Resrv | DV| RV|Rsv| Opcode|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Invalidate STag |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 1 DDP Control and RDMAP Control Fields
The DDP Control Field consists of the T,L, Resrv and DV fields RFC
5041. The RDMAP Control Field consists of the RV, Rsv and Opcode
fields RFC 5040.
This specification adds additional values for the RDMA Opcode field
to those specified in RFC 5040. Figure 2 defines the new values of
RDMA Opcode field that are used for the RDMA Messages defined in
this specification.
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Figure 2As shown in Figure 2, STag and Tagged Offset are not
applicable for the RDMA Messages defined in this specification.
Figure 2 also shows the appropriate Queue Number for each Opcode.
All RDMA Messages defined in this specification MUST have:
The RDMA Version (RV) field: 01b.
Opcode field: Set to one of the values in Figure 2.
Invalidate STag: Set to zero by the sender, ignored by the receiver.
-------+-----------+-------+------+-------+---------+-------------
RDMA | Message | Tagged| STag | Queue | In- | Message
Opcode | Type | Flag | and | Number| validate| Length
| | | TO | | STag | Communicated
| | | | | | between DDP
| | | | | | and RDMAP
-------+-----------+-------+------+-------+---------+-------------
1000b | Immediate | 0 | N/A | 0 | N/A | Yes
| Data | | | | |
-------+-----------+----------------------------------------------
1001b | Immediate | 0 | N/A | 0 | N/A | Yes
| Data with | | | | |
| SE | | | | |
-------+-----------+----------------------------------------------
1010b | Atomic | 0 | N/A | 1 | N/A | Yes
| Request | | | | |
-------+-----------+----------------------------------------------
1011b | Atomic | 0 | N/A | 3 | N/A | Yes
| Response | | | | |
-------+-----------+----------------------------------------------
Figure 2 Additional RDMA Usage of DDP Fields
Note: N/A means Not Applicable.
This extension defines RDMAP use of Queue Number 3 for Untagged
Buffers for Atomic Responses. This queue is used for tracking
outstanding Atomic Requests.
All other DDP and RDMAP control fields are set as described in RFC
5040.
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4.2. RDMA Message Definitions
The following figure defines which RDMA Headers are used on each new
RDMA Message and which new RDMA Messages are allowed to carry ULP
payload:
-------+-----------+-------------------+-------------------------
RDMA | Message | RDMA Header Used | ULP Message allowed in
Message| Type | | the RDMA Message
OpCode | | |
| | |
-------+-----------+-------------------+-------------------------
1000b | Immediate | Immediate Data | No
| Data | Header |
-------+-----------+-------------------+-------------------------
1001b | Immediate | Immediate Data | No
| Data with | Header |
| SE | |
-------+-----------+-------------------+-------------------------
1010b | Atomic | Atomic Request | No
| Request | Header |
-------+-----------+-------------------+-------------------------
1011b | Atomic | Atomic Response | No
| Response | Header |
-------+-----------+-------------------+-------------------------
Figure 3 RDMA Message Definitions
5. Atomic Operations
The RDMA Protocol Specification in RFC 5040 does not include support
for Atomic Operations which are an important building block for
implementing distributed shared memory.
This document extends the RDMA Protocol specification with a set of
basic Atomic Operations, and specifies their resource and ordering
rules. The Atomic Operations specified in this document provide
equivalent functionality to the InfiniBand RDMA transport as well as
extended Atomic Operations defined in Open Fabrics Verbs, to allow
applications that use these primitives to work interchangeably over
iWARP. Other operations are left for future consideration.
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Atomic operations as specified in this document execute a 64-bit
memory operation at a specified destination ULP Buffer address on a
Responder node using the Tagged Buffer data transfer model. The
operations atomically read, modify and write back the contents of
the destination ULP Buffer address and guarantee that Atomic
Operations on this ULP Buffer address by other RDMAP Streams on the
same RNIC do not occur between the read and the write caused by the
Atomic Operation. Therefore, the Responder RNIC MUST implement
mechanisms to prevent Atomic Operations to a memory registered for
Atomic Operations while an Atomic Operation targeting the memory is
in progress. The Requester of an atomic operation cannot rely on
atomic operation behavior at the Responder across multiple RNICs or
with respect to other applications/ULPs running at the Responder
that can access the ULP Buffer. It is OPTIONAL for an RNIC to
provide such behavior when implementing the atomic operations
specified in this document. An RNIC that supports Atomic Operations
as specified in this document MUST implement both the FetchAdd
operation as specified in section 5.1.1 and CmpSwap operation as
specified in section 5.1.2. The advertisement of Tagged Buffer
information for Atomic Operations is outside the scope of this
specification and is handled by the ULPs.
Implementation note: It is RECOMMENDED that the applications do not
use the ULP Buffer addresses used for Atomic Operations for other
RDMA operations due to the lack of atomicity guarantees between
operations other than Atomic Operations.
Implementation note: Errors related to the alignment in the
following sections cover Atomic Operations targeted at a ULP Buffer
address that is not aligned to a 64-bit boundary.
Atomic Operation Request Messages use the same remote addressing
mechanism as RDMA Reads and Writes. The ULP Buffer address specified
in the request is in the address space of the Remote Peer to which
the Atomic Operation is targeted.
Atomic Operation Response Messages MUST use the Untagged Buffer
model with QN=3. Queue number 3 will be used to track outstanding
Atomic Operation Request messages at the Requestor. When the Atomic
Operation Response message is received, the MSN will be used to
locate the corresponding Atomic Operation request in order to
complete the Atomic Operation request.
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5.1. Atomic Operation Details
The following sub-sections describe the Atomic Operations in more
details.
5.1.1. FetchAdd
The FetchAdd Atomic Operation requests the Responder to read a 64-
bit Original Remote Data Value at a 64-bit aligned ULP Buffer
address in the Responder's memory, to perform FetchAdd operation on
multiple fields of selectable length specified by 64-bit "Add Mask",
and write the result back to the same ULP Buffer address. The Atomic
addition is performed independently on each one of these fields. A
bit set in the Add Mask field specifies the field boundary; for each
field, a bit is set at the most significant bit position for each
field, causing any carry out of that bit position to be discarded
when the addition is performed.
FetchAdd Atomic Operations MUST target ULP Buffer addresses that are
64-bit aligned. FetchAdd Atomic Operations that target ULP Buffer
addresses that are not 64-bit aligned MUST be surfaced as errors and
the Responder's memory MUST NOT be modified in such cases.
Additionally an error MUST be surfaced and a terminate message MUST
be generated. The setting of "Add Mask" field to 0x0000000000000000
results in Atomic Add of 64-bit Original Remote Data Value and 64-
bit "Add Data".
The pseudo code below describes masked FetchAdd Atomic Operation.
bit_location = 1
carry = 0
Remote Data Value = 0
for bit = 0 to 63
{
if (bit != 0 ) bit_location = bit_location << 1
val1 = (Original Remote Data Value & bit_location) >> bit
val2 = (Add Data & bit_location) >> bit
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sum = carry + val1 + val2
carry = (sum & 2) >> 1
sum = sum & 1
if (sum)
Remote Data Value |= bit_location
carry = ((carry) && (!(Add Mask & bit_location)))
}
The FetchAdd operation is performed in the endian format of the
target memory. The "Original Remote Data Value" is converted from
the endian format of the target memory for return and returned to
the Requester. The fields are in big-endian format on the wire.
The Requester specifies:
o Remote STag
o Remote Tagged Offset
o Add Data
o Add Mask
The Responder returns:
o Original Remote Data
5.1.2. CmpSwap
The CmpSwap Atomic Operation requires the Responder to read a 64-bit
value at a 64-bit aligned ULP Buffer address in the Responder's
memory, to perform an AND logical operation using the 64 bit
"Compare Mask" field in the Atomic Operation Request header, then to
compare it with the result of a logical AND operation of the
"Compare Mask" and the "Compare Data" fields in the header, and, if
the two values are equal, to swap masked bits in the same ULP Buffer
address with the masked Swap Data. If the two masked compare values
are not equal, the contents of the Responder's memory are not
changed. In either case, the original value read from the ULP Buffer
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address is converted from the endian format of the target memory for
return and returned to the Requester. The fields are in big-endian
format on the wire.
The Requester specifies:
o Remote STag
o Remote Tagged Offset
o Swap Data
o Swap Mask
o Compare Data
o Compare Mask
The Responder returns:
o Original Remote Data Value
The following pseudo code describes the masked CmpSwap operation
result.
if (!((Compare Data ^ Original Remote Data Value) &
Compare Mask))
then
Remote Data Value =
(Original Remote Data Value & ~(Swap Mask))
| (Swap Data & Swap Mask)
else
Remote Data Value = Original Remote Data Value
After the operation, the remote data buffer MUST contain the
"Original Remote Data Value" (if comparison did not match) or the
masked "Swap Data" (if the comparison did match). CmpSwap Atomic
Operations MUST target ULP Buffer addresses that are 64-bit aligned.
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If a CmpSwap Atomic Operation is attempted on a target ULP Buffer
address that is not 64-bit aligned:
o The operation MUST NOT be performed,
o The Responder's memory MUST NOT be modified,
o The result MUST be surfaced as an error, and
o A terminate message MUST be generated (see Section 8.2. for the
terminate message contents)
5.2. Atomic Operations
The Atomic Operation Request and Response are RDMA Messages. An
Atomic Operation makes use of the DDP Untagged Buffer Model. Atomic
Operation Request messages MUST use the same Queue Number as RDMA
Read Requests (QN=1). Reusing the same Queue Number for Atomic
Request messages allows the Atomic Operations to reuse the same
infrastructure (e.g. ORD/IRD flow control) as defined for RDMA Read
Requests. Atomic Operation Response messages MUST set Queue Number
(QN) to 3 in the DDP header.
The RDMA Message OpCode for an Atomic Request Message is 1010b. The
RDMA Message OpCode for an Atomic Response Message is 1011b.
5.2.1. Atomic Operation Request Message
The Atomic Operation Request Message carries an Atomic Operation
Header that describes the ULP Buffer address in the Responder's
memory. The Atomic Operation Request header immediately follows the
DDP header. The RDMAP layer passes to the DDP layer a RDMAP Control
Field. The following figure depicts the Atomic Operation Request
Header that is used for all Atomic Operation Request Messages:
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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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved (Not Used) |AOpCode|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Request Identifier |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Remote STag |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Remote Tagged Offset |
+ +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Add or Swap Data |
+ +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Add or Swap Mask |
+ +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Compare Data |
+ +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Compare Mask |
+ +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 4 Atomic Operation Request Header
Reserved (Not Used): 28 bits
This field is set to zero on transmit, ignored on receive.
Atomic Operation Code (AOpCode): 4 bits.
See Figure 5. All Atomic Operation Codes from Figure 5 MUST
be implemented by an RNIC that supports Atomic Operations.
Request Identifier: 32 bits.
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The Request Identifier specifies a number that is used to
identify Atomic Operation Request Message. The value used in
this field is selected by the RNIC that sends the message, and
is reflected back to the Local Peer in the Atomic Operation
Response message.
Remote STag: 32 bits.
The Remote STag identifies the Remote Peer's Tagged Buffer
targeted by the Atomic Operation. The Remote STag is
associated with the RDMAP Stream through a mechanism that is
outside the scope of the RDMAP specification.
Remote Tagged Offset: 64 bits.
The Remote Tagged Offset specifies the starting offset, in
octets, from the base of the Remote Peer's Tagged Buffer
targeted by the Atomic Operation. The Remote Tagged Offset MAY
start at an arbitrary offset but MUST represent a 64-bit
aligned ULP Buffer address.
Add or Swap Data: 64 bits.
The Add or Swap Data field specifies the 64-bit "Add Data"
value in an Atomic FetchAdd Operation or the 64-bit "Swap
Data" value in an Atomic Swap or CmpSwap Operation.
Add or Swap Mask: 64 bits
This field is used in masked Atomic Operations (FetchAdd and
CmpSwap) to perform a bitwise logical AND operation as
specified in the definition of these operations. For non-
masked Atomic Operations (Swap), this field is set to
ffffffffffffffffh on transmit and ignored by the receiver.
Compare Data: 64 bits.
The Compare Data field specifies the 64-bit "Compare Data"
value in an Atomic CmpSwap Operation. For Atomic FetchAdd and
Atomic Swap operation, the Compare Data field is set to zero
on transmit and ignored by the receiver.
Compare Mask: 64 bits
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This field is used in masked Atomic Operation CmpSwap to
perform a bitwise logical AND operation as specified in the
definition of these operations. For Atomic Operations FetchAdd
and Swap, this field is set to ffffffffffffffffh on transmit
and ignored by the receiver.
---------+-----------+----------+----------+---------+---------
Atomic | Atomic | Add or | Add or | Compare | Compare
Operation| Operation | Swap | Swap | Data | Mask
Code | | Data | Mask | |
---------+-----------+----------+----------+---------+---------
0000b | FetchAdd | Add Data | Add Mask | N/A | N/A
---------+-----------+----------+----------+---------+---------
0010b | CmpSwap | Swap Data| Swap Mask| Valid | Valid
---------+-----------+-----------------------------------------
Figure 5 Atomic Operation Message Definitions
The Atomic Operation Request Message has the following semantics:
1. An Atomic Operation Request Message MUST reference an Untagged
Buffer. That is, the Local Peer's RDMAP layer MUST request that
the DDP mark the Message as Untagged.
2. One Atomic Operation Request Message MUST consume one Untagged
Buffer.
3. The Responder's RDMAP layer MUST process an Atomic Operation
Request Message. A valid Atomic Operation Request Message MUST
NOT be delivered to the Responder's ULP (i.e., it is processed by
the RDMAP layer).
4. At the Responder, an error MUST be surfaced in response to
delivery to the Remote Peer's RDMAP layer of an Atomic Operation
Request Message with an Atomic Operation Code that the RNIC does
not support.
5. An Atomic Operation Request Message MUST reference the RDMA Read
Request Queue. That is, the Requester's RDMAP layer MUST request
that the DDP layer set the Queue Number field to one.
6. The Requester MUST pass to the DDP layer Atomic Operation Request
Messages in the order they were submitted by the ULP.
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7. The Responder MUST process the Atomic Operation Request Messages
in the order they were sent.
8. If the Responder receives a valid Atomic Operation Request
Message, it MUST respond with a valid Atomic Operation Response
Message.
5.2.2. Atomic Operation Response Message
The Atomic Operation Response Message carries an Atomic Operation
Response Header that contains the "Original Request Identifier" and
"Original Remote Data Value". The Atomic Operation Response Header
immediately follows the DDP header. The RDMAP layer passes to the
DDP layer a RDMAP Control Field. The following figure depicts the
Atomic Operation Response header that is used for all Atomic
Operation Response Messages:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Original Request Identifier |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Original Remote Data Value |
+ +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 6 Atomic Operation Response Header
Original Request Identifier: 32 bits.
The Original Request Identifier is set to the value specified
in the Request Identifier field that was originally provided
in the corresponding Atomic Operation Request Message.
Original Remote Data Value: 64 bits.
The Original Remote Value specifies the original 64-bit value
stored at the ULP Buffer address targeted by the Atomic
Operation.
The Atomic Operation Response Message has the following semantics:
1. The Atomic Operation Response Message for the associated Atomic
Operation Request Message travels in the opposite direction.
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2. An Atomic Operation Response Message MUST consume an Untagged
Buffer. That is, the Responder RDMAP layer MUST request that the
DDP mark the Message as Untagged.
3. An Atomic Operation Response Message MUST reference the Queue
Number 3. That is, the Responder's RDMAP layer MUST request that
the DDP layer set the Queue Number field to 3.
4. The Responder MUST ensure that a sufficient number of Untagged
Buffers are available on the RDMA Read Request Queue (Queue with
DDP Queue Number 1) to support the maximum number of Atomic
Operation Requests negotiated by the ULP in addition to the
maximum number of RDMA Read Requests negotiated by the ULP.
5. The Requester MUST ensure that a sufficient number of Untagged
Buffers are available on the RDMA Atomic Response Queue (Queue
with DDP Queue Number 3) to support the maximum number of Atomic
Operation Requests negotiated by the ULP.
6. The RDMAP layer MUST Deliver the Atomic Operation Response
Message to the ULP.
7. At the Requester, when an invalid Atomic Operation Response
Message is delivered to the Remote Peer's RDMAP layer, an error
is surfaced.
8. When the Responder receives Atomic Operation Request messages,
the Responder RDMAP layer MUST pass Atomic Operation Response
Messages to the DDP layer, in the order that the Atomic Operation
Request Messages were received by the RDMAP layer, at the
Responder.
5.3. Atomicity Guarantees
Atomicity of the Read-Modify-Write (RMW) on the Responder's node by
the Atomic Operation MUST be assured in the context of concurrent
atomic accesses by other RDMAP Streams on the same RNIC.
5.4. Atomic Operations Ordering and Completion Rules
In addition to the ordering and completion rules described in RFC
5040, the following rules apply to implementations of the Atomic
operations.
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1. For an Atomic operation, the Requester MUST NOT consider the
contents of the Tagged Buffer at the Responder to be modified by
that specific Atomic Operation until the Atomic Operation
Response Message has been Delivered to RDMAP at the Requester.
2. Atomicity guarantees MUST be provided within the scope of a
single RNIC.
Implementation Note: This requirement for atomicity among
operations is limited to the scope of a single RNIC. Atomicity
guarantees are OPTIONAL with respect to access to the Tagged
Buffer by any other method than an Atomic Operation via the same
RNIC. Examples of such accesses that may not be atomic with
respect to an Atomic Operation include accesses via other RNICs
and local processor memory access to the Tagged Buffer.
3. Atomic Operation Request Messages MUST NOT start processing at
the Responder until they have been Delivered to RDMAP by DDP.
4. Atomic Operation Response Messages MAY be generated at the
Responder after subsequent RDMA Write Messages or Send Messages
have been Placed or Delivered.
5. Atomic Operation Response Message processing at the Responder
MUST be started only after the Atomic Operation Request Message
has been Delivered by the DDP layer (thus, all previous RDMA
Messages on that DDP Stream have been Delivered).
6. Send Messages MAY be Completed at the Responder before prior
incoming Atomic Operation Request Messages have completed their
response processing.
7. An Atomic Operation MUST NOT be Completed at the Requester until
the DDP layer Delivers the associated incoming Atomic Operation
Response Message.
8. If more than one outstanding Atomic Request Messages are
supported by both peers, the Atomic Operation Request Messages
MUST be processed in the order they were delivered by the DDP
layer on the Responder. Atomic Operation Response Messages MUST
be submitted to the DDP layer on the Responder in the order the
Atomic Operation Request Messages were Delivered by DDP.
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6. Immediate Data
The Immediate Data operation is typically used in conjunction with
an RDMA Write Operation to improve ULP processing efficiency. The
efficiency is gained by causing an RDMA Completion to be generated
immediately following the RDMA Write operation. This RDMA Completion
delivers 8 bytes of immediate data at the Remote Peer. The
combination of an RDMA Write Message followed by an Immediate Data
Operation has the same behavior as the RDMA Write with Immediate Data
operation found in InfiniBand. An Immediate Data operation that is
not preceded by an RDMA Write operation causes an RDMA Completion.
6.1. RDMAP Interactions with ULP for Immediate Data
For Immediate Data operations, the following are the interactions
between the RDMAP Layer and the ULP:
. At the Data Source:
. The ULP passes to the RDMAP Layer the following:
. Eight bytes of ULP Immediate Data
. When the Immediate Data operation Completes, an indication
of the Completion results.
. At the Data Sink:
. If the Immediate Data operation is Completed successfully,
the RDMAP Layer passes the following information to the ULP
Layer:
. Eight bytes of Immediate Data
. An Event, if the Data Sink is configured to generate an
Event.
. If the Immediate Data operation is Completed in error, the
Data Sink RDMAP Layer will pass up the corresponding error
information to the Data Sink ULP and send a Terminate
Message to the Data Source RDMAP Layer. The Data Source
RDMAP Layer will then pass up the Terminate Message to the
ULP.
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6.2. Immediate Data Header Format
The Immediate Data and Immediate Data with SE Messages carry
immediate data as shown in Figure 7. The RDMAP layer passes to the
DDP layer an RDMAP Control Field and 8 bytes of Immediate Data. The
first 8 bytes of the data following the DDP header contains the
Immediate Data. See section A.3. for the DDP segment format of an
Immediate Data or Immediate Data with SE Message.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Immediate Data |
+ +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 7 Immediate Data or Immediate Data with SE Message Header
Immediate Data: 64 bits.
Eight bytes of data transferred from the Data Source to an
untagged buffer at the Data Sink.
6.3. Immediate Data or Immediate Data with SE Message
The Immediate Data or Immediate Data with SE Message uses the DDP
Untagged Buffer Model to transfer Immediate Data from the Data
Source to the Data Sink.
. An Immediate Data or Immediate Data with SE Message MUST
reference an Untagged Buffer. That is, the Local Peer's RDMAP
Layer MUST request that the DDP layer mark the Message as
Untagged.
. One Immediate Data or Immediate Data with SE Message MUST consume
one Untagged Buffer.
. At the Remote Peer, the Immediate Data or Immediate Data with SE
Message MUST be Delivered to the Remote Peer's ULP in the order
they were sent.
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. For an Immediate Data or Immediate Data with SE Message, the
Local Peer's RDMAP Layer MUST request that the DDP layer set the
Queue Number field to zero.
. For an Immediate Data or Immediate Data with SE Message, the
Local Peer's RDMAP Layer MUST request that the DDP layer transmit
8 bytes of data.
. The Local Peer MUST issue Immediate Data and Immediate Data with
SE Messages in the order they were submitted by the ULP.
. The Remote Peer MUST check that Immediate Data and Immediate Data
with SE Messages include exactly 8 bytes of data from the DDP
layer. The DDP header carries the length field that is reported
by the DDP layer.
6.4. Ordering and Completions
Ordering and completion rules for Immediate Data are the same as
those for a Send operation as described in section 5.5 of RFC 5040.
7. Ordering and Completions Table
The following table summarizes the ordering relationships for Atomic
and Immediate Data operations from the standpoint of Local Peer
issuing the Operations. Note that in the table that follows, Send
includes Send, Send with Invalidate, Send with Solicited Event, and
Send with Solicited Event and Invalidate. Also note that in the
table below, Immediate Data includes Immediate Data and Immediate
Data with Solicited Event.
---------+----------+-------------+-------------+------------------
First | Second | Placement | Placement | Ordering
Operation| Operation| Guarantee at| Guarantee at| Guarantee at
| | Remote Peer | Local Peer | Remote Peer
---------+----------+-------------+-------------+------------------
Immediate| Send | No Placement| Not | Completed in
Data | | Guarantee | Applicable | Order
| | between Send| |
| | Payload and | |
| | Immediate | |
| | Data | |
---------+----------+-------------+-------------+------------------
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Immediate| RDMA | No Placement| Not | Not
Data | Write | Guarantee | Applicable | Applicable
| | between RDMA| |
| | Write | |
| | Payload and | |
| | Immediate | |
| | Data | |
---------+----------+-------------+-------------+------------------
Immediate| RDMA | No Placement| RDMA Read | RDMA Read
Data | Read | Guarantee | Response | Response
| | between | will not be | Message will
| | Immediate | Placed until| not be
| | Data and | Immediate | generated
| | RDMA Read | Data is | until
| | Request | Placed at | Immediate Data
| | | Remote Peer | has been
| | | | Completed
---------+----------+-------------+-------------+------------------
Immediate| Atomic | No Placement| Atomic | Atomic
Data | | Guarantee | Response | Response
| | between | will not be | Message will
| | Immediate | Placed until| not be
| | Data and | Immediate | generated
| | Atomic | Data is | until
| | Request | Placed at | Immediate Data
| | | Remote Peer | has been
| | | | Completed
---------+----------+-------------+-------------+------------------
Immediate| Immediate| No Placement| Not | Completed in
Data or | Data | Guarantee | Applicable | Order
Send | | | |
---------+----------+-------------+-------------+------------------
RDMA | Immediate| No Placement| Not | Immediate Data
Write | Data | Guarantee | Applicable | is Completed
| | | | after RDMA
| | | | Write is Placed
| | | | and Delivered
---------+----------+-------------+-------------+------------------
RDMA Read| Immediate| No Placement| Immediate | Not Applicable
| Data | Guarantee | Data MAY be |
| | between | Placed |
| | Immediate | before |
| | Data and | RDMA Read |
| | RDMA Read | Response is |
| | Request | generated |
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---------+----------+-------------+-------------+------------------
Atomic | Immediate| No Placement| Immediate | Not Applicable
| Data | Guarantee | Data MAY be |
| | between | Placed |
| | Immediate | before |
| | Data and | Atomic |
| | Atomic | Response is |
| | Request | generated |
---------+----------+-------------+-------------+------------------
Atomic | Send | No Placement| Send Payload| Not Applicable
| | Guarantee | MAY be |
| | between Send| Placed |
| | Payload and | before |
| | Atomic | Atomic |
| | Request | Response is |
| | | generated |
---------+----------+-------------+-------------+------------------
Atomic | RDMA | No Placement| RDMA Write | Not
| Write | Guarantee | Payload MAY | Applicable
| | between RDMA| be Placed |
| | Write | before |
| | Payload and | Atomic |
| | Atomic | Response is |
| | Request | generated |
---------+----------+-------------+-------------+------------------
Atomic | RDMA | No Placement| No Placement| RDMA Read
| Read | Guarantee | Guarantee | Response
| | between | between | Message will
| | Atomic | Atomic | not be
| | Request and | Response | generated
| | RDMA Read | and RDMA | until Atomic
| | Request | Read | Response Message
| | | Response | has been
| | | | generated
---------+----------+-------------+-------------+------------------
Atomic | Atomic | Placed in | No Placement| Second Atomic
| | order | Guarantee | Request
| | | between two | Message will
| | | Atomic | not be
| | | Responses | processed
| | | | until first
| | | | Atomic Response
| | | | has been
| | | | generated
---------+----------+-------------+-------------+------------------
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Send | Atomic | No Placement| Atomic | Atomic Response
| | Guarantee | Response | Message will not
| | between Send| will not be | be generated
| | Payload and | Placed at | until Send has
| | Atomic | the Local | been Completed
| | Request | Peer Until |
| | | Send Payload|
| | | is Placed |
| | | at the |
| | | Remote Peer |
---------+----------+-------------+-------------+------------------
RDMA | Atomic | No Placement| Atomic | Not
Write | | Guarantee | Response | Applicable
| | between RDMA| will not be |
| | Write | Placed at |
| | Payload and | the Local |
| | Atomic | Peer Until |
| | Request | RDMA Write |
| | | Payload |
| | | is Placed |
| | | at the |
| | | Remote Peer |
---------+----------+-------------+-------------+------------------
RDMA | Atomic | No Placement| No Placement| Atomic Response
Read | | Guarantee | Guarantee | Message will
| | between | between | not be generated
| | Atomic | Atomic | until RDMA
| | Request and | Response | Read Response
| | RDMA Read | and RDMA | has been
| | Request | Read | generated
| | | Response |
---------+----------+-------------+-------------+------------------
8. Error Processing
In addition to error processing described in section 7 of RFC 5040,
the following rules apply for the new RDMA Messages defined in this
specification.
8.1. Errors Detected at the Local Peer
The Local Peer MUST send a Terminate Message for each of the
following cases:
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1. For errors detected while creating an Atomic Request, Atomic
Response, Immediate Data, or Immediate Data with SE Message, or
other reasons not directly associated with an incoming Message,
the Terminate Message and Error code are sent instead of the
Message. In this case, the Error Type and Error Code fields are
included in the Terminate Message, but the Terminated DDP Header
and Terminated RDMA Header fields are set to zero.
2. For errors detected on an incoming Atomic Request, Atomic
Response, Immediate Data, or Immediate Data with Solicited Event
(after the Message has been Delivered by DDP), the Terminate
Message is sent at the earliest possible opportunity, preferably
in the next outgoing RDMA Message. In this case, the Error Type,
Error Code, and Terminated DDP Header fields are included in the
Terminate Message, but the Terminated RDMA Header field is set to
zero.
8.2. Errors Detected at the Remote Peer
On incoming Atomic Requests, Atomic Responses, Immediate Data, and
Immediate Data with Solicited Event, the following MUST be
validated:
. The DDP layer MUST validate all DDP Segment fields.
. The RDMA OpCode MUST be valid.
. The RDMA Version MUST be valid.
On incoming Atomic requests the following additional validation MUST
be performed:
. The RDMAP layer MUST validate that the Remote Peer's Tagged ULP
Buffer address references a 64-bit aligned ULP Buffer address. In
the case of an error, the RDMAP layer MUST generate a Terminate
Message indicating RDMA Layer Remote Operation Error with Error
Code Name "Catastrophic Error, Localized to RDMAP Stream" as
described in Section 4.8 of RFC 5040. Implementation Note: A ULP
implementation can avoid this error by having the target ULP
buffer of an atomic operation 64-bit aligned.
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9. Security Considerations
This document specifies extensions to the RDMA Protocol
specification in RFC 5040, and as such the Security Considerations
discussed in Section 8 of RFC 5040 apply. In particular, Atomic
Operations use ULP Buffer addresses for the Remote Peer buffer
addressing used in RFC 5040 as required by the RFC 5042 [RFC5042]
security model.
RDMAP and related protocols may be used by applications that exhibit
distinctive traffic characteristics such as message timing, source,
destination and size patterns. Examples include structured high
performance computing applications based on the MPI interface. For
such applications, analysis of encrypted traffic could reveal
sensitive information, e.g., the nature of the application, size of
data set being used, and information about the application's rate of
progress. Such information can be hidden from passive observation
via use of ESPv3 Traffic Flow Confidentiality [RFC4303] to obfuscate
the encrypted traffic's characteristics. ESPv3 implementation
requirements for RDMAP are specified in [RFC7146].
10. IANA Considerations
IANA is requested to add the following entries to the "RDMAP Message
Operation Codes" registry of "RDDP Registries":
0x8, Immediate Data, [RFCXXXX]
0x9, Immediate Data with Solicited Event, [RFCXXXX]
0xA, Atomic Request, [RFCXXXX]
0xB, Atomic Response, [RFCXXXX]
In addition, the following registry is requested to be added to
"RDDP Registries". The following section specifies the registry, its
initial contents and the administration policy in more detail.
RFC Editor: Please replace XXXX in all instances of [RFCXXXX] above
with the RFC number of this document and remove this note.
10.1. RDMAP Message Atomic Operation Subcodes
Name of the registry: "RDMAP Message Atomic Operation Subcodes"
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Namespace details: RDMAP Message Atomic Operation Subcodes are 4-bit
values [RFCXXXX].
Information that must be provided to assign a new value: An IESG-
approved standards-track specification defining the semantics and
interoperability requirements of the proposed new value and the
fields to be recorded in the registry.
Fields to record in the registry: RDMAP Message Atomic Operation
Subcode, Atomic Operation, RFC Reference.
Initial registry contents:
0x0, FetchAdd, [RFCXXXX]
0x1, Reserved
0x2, CmpSwap, [RFCXXXX]
Note: An experimental RDMAP Message Operation Code has already been
allocated; hence there is no need for an experimental RDMAP Message
Atomic Operation Subcode.
All other values are Unassigned and available to IANA for
assignment. New RDMAP Message Atomic Operation Subcodes should be
assigned sequentially in order to better support implementations
that process RDMAP Message Atomic Operations in hardware.
Allocation Policy: Standards Action ([RFC5226])
RFC Editor: Please replace XXXX in all instances of [RFCXXXX] above
with the RFC number of this document and remove this note.
10.2. RDMAP Queue Numbers
Name of the registry: "RDMAP DDP Untagged Queue Numbers"
Namespace details: RDMAP DDP Untagged Queue numbers are 32-bit
values [RFCXXXX].
Information that must be provided to assign a new value: An IESG-
approved standards-track specification defining the semantics and
interoperability requirements of the proposed new value and the
fields to be recorded in the registry.
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Fields to record in the registry: RDMAP DDP Untagged Queue Numbers,
Queue Usage Description, RFC Reference.
Initial registry contents:
0x00000000, Queue 0 (Send operation Variants), [RFC5040]
0x00000001, Queue 1 (RDMA Read Request operations), [RFC5040]
0x00000002, Queue 2 (Terminate operations), [RFC5040]
0x00000003, Queue 3 (Atomic Response operations), [RFCXXXX]
Note: An experimental RDMAP Message Operation Code has already been
allocated; hence there is no need for an experimental RDMAP DDP
Untagged Queue Number.
All other values are Unassigned and available to IANA for
assignment. New RDMAP queue numbers should be assigned sequentially
in order to better support implementations that perform RDMAP queue
selection in hardware.
Allocation Policy: Standards Action ([RFC5226])
RFC Editor: Please replace XXXX in all instances of [RFCXXXX] above
with the RFC number of this document and remove this note.
11. References
11.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC4303] S. Kent, "IP Encapsulating Security Payload (ESP)", RFC
4303, December 2005.
[RFC5040] Recio, R. et al., "A Remote Direct Memory Access Protocol
Specification", RFC 5040, October 2007.
[RFC5041] Shah, H. et al., "Direct Data Placement over Reliable
Transports", RFC 5041, October 2007.
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[RFC5042] Pinkerton, J. and E. Deleganes, "Direct Data Placement
Protocol (DDP) / Remote Direct Memory Access Protocol
(RDMAP) Security", October 2007.
[RFC5226] T. Narten and H. Alvestrand, "Guidelines for Writing an
IANA Considerations Section in RFCs", May 2008.
[RFC7146] D. Black and P. Koning, "Securing Block Storage Protocols
over IP: RFC 3723 Requirements Update for IPsec v3", April
2014.
RFC Editor: Please remove reference to RFC5226 if the associated
IANA Considerations reference is also removed before publication.
11.2. Informative References
[IB] InfiniBand Trade Association, "InfiniBand Architecture
Specification Volumes 1 and 2", Release 1.1, November
2002, available from http://www.infinibandta.org/specs.
[RSOCKETS] RSockets, RDMA enabled Sockets library for Open Fabrics,
available from
http://git.openfabrics.org/?p=~shefty/librdmacm.git;a=summ
ary.
[RFC5044] P. Culley, U. Elzur, R. Recio, S. Bailey, J. Carrier,
"Marker PDU Aligned Framing for TCP Specification",
October 2007.
[RFC5045] C. Bestler and L. Coene, "Applicability of Remote Direct
Memory Access Protocol (RDMA and Direct Data Placement
Protocol (DDP)", October 2007.
[RFC6581] A. Kanevsky, C. Bestler, R. Sharp, S. Wise, "Enhanced
Remote Direct Memory Access (RDMA) Connection
Establishment", April 2012.
[OFAVERBS] Open Fabrics Alliance Verbs Enhanced Atomic Operations,
"[PATCH 0/2] Add support for enhanced atomic operations",
available from http://www.spinics.net/lists/linux-
rdma/msg02405.html.
[DAT_ATOMICS] DAT Collaborative, User Direct Access Programming
Library, "Ratified DAT IB extension spec", available from
http://www.datcollaborative.org/DAT_IB_Extensions.pdf.
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[MPI] Message Passing Interface Forum, "MPI: A Message-Passing
Interface Standard, Version 3.0", available from
http://www.mpi-forum.org/docs/mpi-3.0/mpi30-report.pdf,
September 2012.
12. Acknowledgments
The authors would like to acknowledge the following contributors who
provided valuable comments and suggestions.
o David Black
o Arkady Kanevsky
o Bernard Metzler
o Jim Pinkerton
o Tom Talpey
o Steve Wise
o Don Wood
This document was prepared using 2-Word-v2.0.template.dot.
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Appendix A. DDP Segment Formats for RDMA Messages
This appendix is for information only and is NOT part of the
standard. It simply depicts the DDP Segment format for the various
RDMA Messages.
A.1. DDP Segment for Atomic Operation Request
The following figure depicts an Atomic Operation Request, DDP
Segment:
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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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| DDP Control | RDMA Control |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved (Not Used) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| DDP (Atomic Operation Request) Queue Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| DDP (Atomic Operation Request) Message Sequence Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| DDP (Atomic Operation Request) Message Offset |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved (Not Used) |AOpCode|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Request Identifier |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Remote STag |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Remote Tagged Offset |
+ +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Add or Swap Data |
+ +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Add or Swap Mask |
+ +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Compare Data |
+ +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Compare Mask |
+ +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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A.2. DDP Segment for Atomic Response
The following figure depicts an Atomic Operation Response, DDP
Segment:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| DDP Control | RDMA Control |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved (Not Used) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| DDP (Atomic Operation Request) Queue Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| DDP (Atomic Operation Request) Message Sequence Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| DDP (Atomic Operation Request) Message Offset |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Original Request Identifier |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Original Remote Value |
+ +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
A.3. DDP Segment for Immediate Data and Immediate Data with SE
The following figure depicts an Immediate Data or Immediate data
with SE, DDP Segment:
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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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| DDP Control | RDMA Control |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved (Not Used) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| DDP (Send) Queue Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| DDP (Send) Message Sequence Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| DDP Message Offset |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Immediate Data |
+ +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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Authors' Addresses
Hemal Shah
Broadcom Corporation
5300 California Avenue
Irvine, CA 92617
Phone: 1-949-926-6941
Email: hemal@broadcom.com
Felix Marti
Chelsio Communications, Inc.
370 San Aleso Ave.
Sunnyvale, CA 94085
Phone: 1-408-962-3600
Email: felix@chelsio.com
Asgeir Eiriksson
Chelsio Communications, Inc.
370 San Aleso Ave.
Sunnyvale, CA 94085
Phone: 1-408-962-3600
Email: asgeir@chelsio.com
Wael Noureddine
Chelsio Communications, Inc.
370 San Aleso Ave.
Sunnyvale, CA 94085
Phone: 1-408-962-3600
Email: wael@chelsio.com
Robert Sharp
Intel Corporation
1300 South Mopac Expy, Mailstop: AN4-4B
Austin, TX 78746
Phone: 1-512-362-1407
Email: robert.o.sharp@intel.com
Shah et al. Expires October 16, 2014 [Page 37]
