draft-ietf-nfsv4-rpcrdma-cm-pvt-data-08.txt   rfc8797.txt 
Network File System Version 4 C. Lever Internet Engineering Task Force (IETF) C. Lever
Internet-Draft Oracle Request for Comments: 8797 Oracle
Updates: 8166 (if approved) February 21, 2020 Updates: 8166 June 2020
Intended status: Standards Track Category: Standards Track
Expires: August 24, 2020 ISSN: 2070-1721
RDMA Connection Manager Private Data For RPC-Over-RDMA Version 1 Remote Direct Memory Access - Connection Manager (RDMA-CM) Private Data
draft-ietf-nfsv4-rpcrdma-cm-pvt-data-08 for RPC-over-RDMA Version 1
Abstract Abstract
This document specifies the format of Remote Direct Memory Access - This document specifies the format of Remote Direct Memory Access -
Connection Manager (RDMA-CM) Private Data exchanged between RPC-over- Connection Manager (RDMA-CM) Private Data exchanged between RPC-over-
RDMA version 1 peers as part of establishing a connection. The RDMA version 1 peers as part of establishing a connection. The
addition of the private data payload specified in this document is an addition of the Private Data payload specified in this document is an
optional extension that does not alter the RPC-over-RDMA version 1 optional extension that does not alter the RPC-over-RDMA version 1
protocol. This document updates RFC 8166. protocol. This document updates RFC 8166.
Status of This Memo Status of This Memo
This Internet-Draft is submitted in full conformance with the This is an Internet Standards Track document.
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at https://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months This document is a product of the Internet Engineering Task Force
and may be updated, replaced, or obsoleted by other documents at any (IETF). It represents the consensus of the IETF community. It has
time. It is inappropriate to use Internet-Drafts as reference received public review and has been approved for publication by the
material or to cite them other than as "work in progress." Internet Engineering Steering Group (IESG). Further information on
Internet Standards is available in Section 2 of RFC 7841.
This Internet-Draft will expire on August 24, 2020. Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
https://www.rfc-editor.org/info/rfc8797.
Copyright Notice Copyright Notice
Copyright (c) 2020 IETF Trust and the persons identified as the Copyright (c) 2020 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
(https://trustee.ietf.org/license-info) in effect on the date of (https://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
carefully, as they describe your rights and restrictions with respect carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of include Simplified BSD License text as described in Section 4.e of
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. Requirements Language . . . . . . . . . . . . . . . . . . . . 3 2. Requirements Language
3. Advertised Transport Properties . . . . . . . . . . . . . . . 3 3. Advertised Transport Properties
3.1. Inline Threshold Size . . . . . . . . . . . . . . . . . . 4 3.1. Inline Threshold Size
3.2. Remote Invalidation . . . . . . . . . . . . . . . . . . . 4 3.2. Remote Invalidation
4. Private Data Message Format . . . . . . . . . . . . . . . . . 5 4. Private Data Message Format
4.1. Using the R Field . . . . . . . . . . . . . . . . . . . . 7 4.1. Using the R Field
4.2. Send and Receive Size Values . . . . . . . . . . . . . . 7 4.2. Send and Receive Size Values
5. Interoperability Considerations . . . . . . . . . . . . . . . 7 5. Interoperability Considerations
5.1. Interoperability with RPC-over-RDMA Version 1 5.1. Interoperability with RPC-over-RDMA Version 1
Implementations . . . . . . . . . . . . . . . . . . . . . 8 Implementations
5.2. Interoperability Amongst RDMA Transports . . . . . . . . 8 5.2. Interoperability amongst RDMA Transports
6. Updating the Message Format . . . . . . . . . . . . . . . . . 8 6. Updating the Message Format
7. Security Considerations . . . . . . . . . . . . . . . . . . . 9 7. Security Considerations
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10 8. IANA Considerations
8.1. Guidance for Designated Experts . . . . . . . . . . . . . 10 8.1. Guidance for Designated Experts
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 11 9. References
9.1. Normative References . . . . . . . . . . . . . . . . . . 11 9.1. Normative References
9.2. Informative References . . . . . . . . . . . . . . . . . 12 9.2. Informative References
Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . 12 Acknowledgments
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 13 Author's Address
1. Introduction 1. Introduction
The RPC-over-RDMA version 1 transport protocol [RFC8166] enables The RPC-over-RDMA version 1 transport protocol [RFC8166] enables
payload data transfer using Remote Direct Memory Access (RDMA) for payload data transfer using Remote Direct Memory Access (RDMA) for
upper-layer protocols based on Remote Procedure Calls (RPC) upper-layer protocols based on Remote Procedure Calls (RPCs)
[RFC5531]. The terms "Remote Direct Memory Access" (RDMA) and [RFC5531]. The terms "Remote Direct Memory Access" (RDMA) and
"Direct Data Placement" (DDP) are introduced in [RFC5040]. "Direct Data Placement" (DDP) are introduced in [RFC5040].
The two most immediate shortcomings of RPC-over-RDMA version 1 are: The two most immediate shortcomings of RPC-over-RDMA version 1 are as
follows:
o Setting up an RDMA data transfer (via RDMA Read or Write) can be 1. Setting up an RDMA data transfer (via RDMA Read or Write) can be
costly. The small default size of messages transmitted using RDMA costly. The small default size of messages transmitted using
Send forces the use of RDMA Read or Write operations even for RDMA Send forces the use of RDMA Read or Write operations even
relatively small messages and data payloads. for relatively small messages and data payloads.
The original specification of RPC-over-RDMA version 1 provided an
out-of-band protocol for passing inline threshold values between
connected peers [RFC5666]. However, [RFC8166] eliminated support
for this protocol making it unavailable for this purpose.
o Unlike most other contemporary RDMA-enabled storage protocols, The original specification of RPC-over-RDMA version 1 provided an
there is no facility in RPC-over-RDMA version 1 that enables the out-of-band protocol for passing inline threshold values between
use of remote invalidation [RFC5042]. connected peers [RFC5666]. However, [RFC8166] eliminated support
for this protocol, making it unavailable for this purpose.
Each RPC-over-RDMA version 1 transport header follows the External 2. Unlike most other contemporary RDMA-enabled storage protocols,
Data Representation (XDR) [RFC4506] definition specified in there is no facility in RPC-over-RDMA version 1 that enables the
use of remote invalidation [RFC5042].
Each RPC-over-RDMA version 1 Transport Header follows the External
Data Representation (XDR) definition [RFC4506] specified in
[RFC8166]. However, RPC-over-RDMA version 1 has no means of [RFC8166]. However, RPC-over-RDMA version 1 has no means of
extending this definition in such a way that interoperability with extending this definition in such a way that interoperability with
existing implementations is preserved. As a result, an out-of-band existing implementations is preserved. As a result, an out-of-band
mechanism is needed to help relieve these constraints for existing mechanism is needed to help relieve these constraints for existing
RPC-over-RDMA version 1 implementations. RPC-over-RDMA version 1 implementations.
This document specifies a simple, non-XDR-based message format This document specifies a simple, non-XDR-based message format
designed to be passed between RPC-over-RDMA version 1 peers at the designed to be passed between RPC-over-RDMA version 1 peers at the
time each RDMA transport connection is first established. The time each RDMA transport connection is first established. The
mechanism assumes that the underlying RDMA transport has a private mechanism assumes that the underlying RDMA transport has a Private
data field that is passed between peers at connection time, such as Data field that is passed between peers at connection time, such as
is present in the iWARP protocol (described in Section 7.1 of is present in the Marker PDU Aligned Framing (MPA) protocol
[RFC5044]) or the InfiniBand Connection Manager [IBA]. (described in Section 7.1 of [RFC5044] and extended in [RFC6581]) or
the InfiniBand Connection Manager [IBA].
To enable current RPC-over-RDMA version 1 implementations to To enable current RPC-over-RDMA version 1 implementations to
interoperate with implementations that support the private message interoperate with implementations that support the message format
format described in this document, implementation of the private data described in this document, implementation of the Private Data
message is OPTIONAL. When the private data message has been exchange is OPTIONAL. When Private Data has been successfully
successfully exchanged, peers may choose to perform extended RDMA exchanged, peers may choose to perform extended RDMA semantics.
semantics. However, the private message format does not alter the However, this exchange does not alter the XDR definition specified in
XDR definition specified in [RFC8166]. [RFC8166].
The message format is intended to be further extensible within the The message format is intended to be further extensible within the
normal scope of such IETF work (see Section 6 for further details). normal scope of such IETF work (see Section 6 for further details).
Section 8 of this document defines an IANA registry for this purpose. Section 8 of this document defines an IANA registry for this purpose.
In addition, interoperation between implementations of RPC-over-RDMA In addition, interoperation between implementations of RPC-over-RDMA
version 1 that present this message format to peers and those that do version 1 that present this message format to peers and those that do
not recognize this message format is guaranteed. not recognize this message format is guaranteed.
2. Requirements Language 2. Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in BCP "OPTIONAL" in this document are to be interpreted as described in
14 [RFC2119] [RFC8174] when, and only when, they appear in all BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here. capitals, as shown here.
3. Advertised Transport Properties 3. Advertised Transport Properties
3.1. Inline Threshold Size 3.1. Inline Threshold Size
Section 3.3.2 of [RFC8166] defines the term "inline threshold." An Section 3.3.2 of [RFC8166] defines the term "inline threshold". An
inline threshold is the maximum number of bytes that can be inline threshold is the maximum number of bytes that can be
transmitted using one RDMA Send and one RDMA Receive. There are a transmitted using one RDMA Send and one RDMA Receive. There are a
pair of inline thresholds for a connection: a client-to-server pair of inline thresholds for a connection: a client-to-server
threshold and a server-to-client threshold. threshold and a server-to-client threshold.
If an incoming RDMA message exceeds the size of a receiver's inline If an incoming RDMA message exceeds the size of a receiver's inline
threshold, the receive operation fails and the RDMA provider threshold, the Receive operation fails and the RDMA provider
typically terminates the connection. To convey an RPC message larger typically terminates the connection. To convey an RPC message larger
than the receiver's inline threshold without risking receive failure, than the receiver's inline threshold without risking receive failure,
a sender must use explicit RDMA data transfer operations, which are a sender must use explicit RDMA data transfer operations, which are
more expensive than an RDMA Send. See Sections 3.3 and 3.5 of more expensive than an RDMA Send. See Sections 3.3 and 3.5 of
[RFC8166] for a complete discussion. [RFC8166] for a complete discussion.
The default value of inline thresholds for RPC-over-RDMA version 1 The default value of inline thresholds for RPC-over-RDMA version 1
connections is 1024 bytes (as defined in Section 3.3.3 of [RFC8166]). connections is 1024 bytes (as defined in Section 3.3.3 of [RFC8166]).
This value is adequate for nearly all NFS version 3 procedures. This value is adequate for nearly all NFS version 3 procedures.
NFS version 4 COMPOUND operations [RFC7530] are larger on average NFS version 4 COMPOUND operations [RFC7530] are larger on average
than NFS version 3 procedures [RFC1813], forcing clients to use than NFS version 3 procedures [RFC1813], forcing clients to use
explicit RDMA operations for frequently-issued requests such as explicit RDMA operations for frequently issued requests such as
LOOKUP and GETATTR. The use of RPCSEC_GSS security also increases LOOKUP and GETATTR. The use of RPCSEC_GSS security also increases
the average size of RPC messages, due to the larger size of the average size of RPC messages, due to the larger size of
RPCSEC_GSS credential material included in RPC headers [RFC7861]. RPCSEC_GSS credential material included in RPC headers [RFC7861].
If a sender and receiver could somehow agree on larger inline If a sender and receiver could somehow agree on larger inline
thresholds, frequently-used RPC transactions avoid the cost of thresholds, frequently used RPC transactions avoid the cost of
explicit RDMA operations. explicit RDMA operations.
3.2. Remote Invalidation 3.2. Remote Invalidation
After an RDMA data transfer operation completes, an RDMA consumer can After an RDMA data transfer operation completes, an RDMA consumer can
request that its peer's RDMA network interface card (RNIC) invalidate request that its peer's RDMA Network Interface Card (RNIC) invalidate
the Steering Tag (STag) associated with the data transfer [RFC5042]. the Steering Tag (STag) associated with the data transfer [RFC5042].
An RDMA consumer requests remote invalidation by posting an RDMA Send An RDMA consumer requests remote invalidation by posting an RDMA Send
With Invalidate Work Request in place of an RDMA Send Work Request. with Invalidate operation in place of an RDMA Send operation. Each
Each RDMA Send With Invalidate carries one STag to invalidate. The RDMA Send with Invalidate carries one STag to invalidate. The
receiver of an RDMA Send With Invalidate performs the requested receiver of an RDMA Send with Invalidate performs the requested
invalidation and then reports that invalidation as part of the invalidation and then reports that invalidation as part of the
completion of a waiting Receive Work Request. completion of a waiting Receive operation.
If both peers support remote invalidation, an RPC-over-RDMA responder If both peers support remote invalidation, an RPC-over-RDMA responder
might use remote invalidation when replying to an RPC request that might use remote invalidation when replying to an RPC request that
provided chunks. Because one of the chunks has already been provided chunks. Because one of the chunks has already been
invalidated, finalizing the results of the RPC is made simpler and invalidated, finalizing the results of the RPC is made simpler and
faster. faster.
However, there are some important caveats which contraindicate the However, there are some important caveats that contraindicate the
blanket use of remote invalidation: blanket use of remote invalidation:
o Remote invalidation is not supported by all RNICs. * Remote invalidation is not supported by all RNICs.
o Not all RPC-over-RDMA responder implementations can generate RDMA * Not all RPC-over-RDMA responder implementations can generate RDMA
Send With Invalidate Work Requests. Send with Invalidate operations.
o Not all RPC-over-RDMA requester implementations can recognize when * Not all RPC-over-RDMA requester implementations can recognize when
remote invalidation has occurred. remote invalidation has occurred.
o On one connection in different RPC-over-RDMA transactions, or in a * On one connection in different RPC-over-RDMA transactions, or in a
single RPC-over-RDMA transaction, an RPC-over-RDMA requester can single RPC-over-RDMA transaction, an RPC-over-RDMA requester can
expose a mixture of STags that may be invalidated remotely and expose a mixture of STags that may be invalidated remotely and
some that must not be. No indication is provided at the RDMA some that must not be. No indication is provided at the RDMA
layer as to which is which. layer as to which is which.
A responder therefore must not employ remote invalidation unless it A responder therefore must not employ remote invalidation unless it
is aware of support for it in its own RDMA stack, and on the is aware of support for it in its own RDMA stack, and on the
requester. And, without altering the XDR structure of RPC-over-RDMA requester. And, without altering the XDR structure of RPC-over-RDMA
version 1 messages, it is not possible to support remote invalidation version 1 messages, it is not possible to support remote invalidation
with requesters that mix STags that may and must not be invalidated with requesters that include an STag that must not be invalidated
remotely in a single RPC or on the same connection. remotely in an RPC with STags that may be invalidated. Likewise, it
is not possible to support remote invalidation with requesters that
mix RPCs with STags that may be invalidated with RPCs with STags that
must not be invalidated on the same connection.
There are some NFS/RDMA client implementations whose STags are always There are some NFS/RDMA client implementations whose STags are always
safe to invalidate remotely. For such clients, indicating to the safe to invalidate remotely. For such clients, indicating to the
responder that remote invalidation is always safe can enable such responder that remote invalidation is always safe can enable such
invalidation without the need for additional protocol elements to be invalidation without the need for additional protocol elements to be
defined. defined.
4. Private Data Message Format 4. Private Data Message Format
With an InfiniBand lower layer, for example, RDMA connection setup With an InfiniBand lower layer, for example, RDMA connection setup
uses a Connection Manager when establishing a Reliable Connection uses a Connection Manager (CM) when establishing a Reliable
[IBA]. When an RPC-over-RDMA version 1 transport connection is Connection [IBA]. When an RPC-over-RDMA version 1 transport
established, the client (which actively establishes connections) and connection is established, the client (which actively establishes
the server (which passively accepts connections) populate the CM connections) and the server (which passively accepts connections)
Private Data field exchanged as part of CM connection establishment. populate the CM Private Data field exchanged as part of CM connection
establishment.
The transport properties exchanged via this mechanism are fixed for The transport properties exchanged via this mechanism are fixed for
the life of the connection. Each new connection presents an the life of the connection. Each new connection presents an
opportunity for a fresh exchange. An implementation of the extension opportunity for a fresh exchange. An implementation of the extension
described in this document MUST be prepared for the settings to described in this document MUST be prepared for the settings to
change upon a reconnection. change upon a reconnection.
For RPC-over-RDMA version 1, the CM Private Data field is formatted For RPC-over-RDMA version 1, the CM Private Data field is formatted
as described in the following subsection. RPC clients and servers as described below. RPC clients and servers use the same format. If
use the same format. If the capacity of the Private Data field is the capacity of the Private Data field is too small to contain this
too small to contain this message format or the underlying RDMA message format or the underlying RDMA transport is not managed by a
transport is not managed by a Connection Manager, the CM Private Data CM, the CM Private Data field cannot be used on behalf of RPC-over-
field cannot be used on behalf of RPC-over-RDMA version 1. RDMA version 1.
The first 8 octets of the CM Private Data field is to be formatted as The first eight octets of the CM Private Data field are to be
follows: formatted as follows:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Format Identifier | | Format Identifier |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Version | Reserved |R| Send Size | Receive Size | | Version | Reserved |R| Send Size | Receive Size |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Format Identifier: This field contains a fixed 32-bit value that Format Identifier: This field contains a fixed 32-bit value that
identifies the content of the Private Data field as an RPC-over- identifies the content of the Private Data field as an RPC-over-
RDMA version 1 CM Private Data message. In RPC-over-RDMA version RDMA version 1 CM Private Data message. In RPC-over-RDMA
1 Private Data, the value of this field is always 0xf6ab0e18, in version 1 Private Data, the value of this field is always
network byte order. The use of this field is further expanded 0xf6ab0e18, in network byte order. The use of this field is
upon in Section 5.2. further expanded upon in Section 5.2.
Version: This 8-bit field contains a message format version number. Version: This 8-bit field contains a message format version number.
The value "1" in this field indicates that exactly eight octets The value "1" in this field indicates that exactly eight octets
are present, that they appear in the order described in this are present, that they appear in the order described in this
section, and that each has the meaning defined in this section. section, and that each has the meaning defined in this section.
Further considerations about the use of this field are discussed Further considerations about the use of this field are discussed
in Section 6. in Section 6.
Reserved: This 7-bit field is unused. Senders MUST set these bits Reserved: This 7-bit field is unused. Senders MUST set these bits
to zero and receivers MUST ignore their value. to zero, and receivers MUST ignore their value.
R: This 1-bit field indicates that the sender supports remote R: This 1-bit field indicates that the sender supports remote
invalidation. The field is set and interpreted as described in invalidation. The field is set and interpreted as described in
Section 4.1. Section 4.1.
Send Size: This 8-bit field contains an encoded value corresponding Send Size: This 8-bit field contains an encoded value corresponding
to the maximum number of bytes this peer is prepared to transmit to the maximum number of bytes this peer is prepared to transmit
in a single RDMA Send on this connection. The value is encoded as in a single RDMA Send on this connection. The value is encoded as
described in Section 4.2. described in Section 4.2.
Receive Size: This 8-bit field contains an encoded value Receive Size: This 8-bit field contains an encoded value
corresponding to the maximum number of bytes this peer is prepared corresponding to the maximum number of bytes this peer is prepared
to receive with a single RDMA Receive on this connection. The to receive with a single RDMA Receive on this connection. The
value is encoded as described in Section 4.2. value is encoded as described in Section 4.2.
4.1. Using the R Field 4.1. Using the R Field
The R field indicates limited support for remote invalidate as The R field indicates limited support for remote invalidation as
described in Section 3.2. When both connection peers have set this described in Section 3.2. When both connection peers have set this
bit flag in their CM Private Data, the responder MAY use RDMA Send bit flag in their CM Private Data, the responder MAY use RDMA Send
With Invalidate when transmitting RPC Replies. Each RDMA Send With with Invalidate operations when transmitting RPC Replies. Each RDMA
Invalidate MUST invalidate an STag associated only with the XID in Send with Invalidate MUST invalidate an STag associated only with the
the rdma_xid field of the RPC-over-RDMA Transport Header it carries. Transaction ID (XID) in the rdma_xid field of the RPC-over-RDMA
Transport Header it carries.
When either peer on a connection clears this flag, the responder MUST When either peer on a connection clears this flag, the responder MUST
use only RDMA Send when transmitting RPC Replies. use only RDMA Send when transmitting RPC Replies.
4.2. Send and Receive Size Values 4.2. Send and Receive Size Values
Inline threshold sizes from 1024 to 262144 octets can be represented Inline threshold sizes from 1024 to 262144 octets can be represented
in the Send Size and Receive Size fields. The inline threshold in the Send Size and Receive Size fields. The inline threshold
values provide a pair of 1024-octet-aligned maximum message lengths values provide a pair of 1024-octet-aligned maximum message lengths
that guarantee Send and Receive operations do not fail due to length that guarantee that Send and Receive operations do not fail due to
errors. length errors.
The minimum inline threshold for RPC-over-RDMA version 1 is 1024 The minimum inline threshold for RPC-over-RDMA version 1 is 1024
octets (see Section 3.3.3 of [RFC8166]). The values in the Send Size octets (see Section 3.3.3 of [RFC8166]). The values in the Send Size
and Receive Size fields represent the unsigned number of additional and Receive Size fields represent the unsigned number of additional
kilo-octets of length beyond the first 1024 octets. Thus, a sender kilo-octets of length beyond the first 1024 octets. Thus, a sender
computes the encoded value by dividing its actual buffer size, in computes the encoded value by dividing its actual buffer size, in
octets, by 1024 and subtracting one from the result. A receiver octets, by 1024 and subtracting one from the result. A receiver
decodes an incoming Size value by performing the inverse set of decodes an incoming Size value by performing the inverse set of
operations: it adds one to the encoded value and then multiplies that operations: it adds one to the encoded value and then multiplies that
result by 1024. result by 1024.
The client uses the smaller of its own send size and the server's The client uses the smaller of its own send size and the server's
reported receive size as the client-to-server inline threshold. The reported receive size as the client-to-server inline threshold. The
server uses the smaller of its own send size and the clients's server uses the smaller of its own send size and the client's
reported receive size as the server-to-client inline threshold. reported receive size as the server-to-client inline threshold.
5. Interoperability Considerations 5. Interoperability Considerations
The extension described in this document is designed to allow RPC- The extension described in this document is designed to allow RPC-
over-RDMA version implementations that use CM Private Data to over-RDMA version implementations that use CM Private Data to
interoperate fully with RPC-over-RDMA version 1 implementations that interoperate fully with RPC-over-RDMA version 1 implementations that
do not exchange this information. Implementations that use this do not exchange this information. Implementations that use this
extension must also interoperate fully with RDMA implementations that extension must also interoperate fully with RDMA implementations that
use CM Private Data for other purposes. Realizing these goals use CM Private Data for other purposes. Realizing these goals
requires that implementations of this extension follow the practices requires that implementations of this extension follow the practices
described in the rest of this section. described in the rest of this section.
5.1. Interoperability with RPC-over-RDMA Version 1 Implementations 5.1. Interoperability with RPC-over-RDMA Version 1 Implementations
When a peer does not receive a CM Private Data message which conforms When a peer does not receive a CM Private Data message that conforms
to Section 4, it needs to act as if the remote peer supports only the to Section 4, it needs to act as if the remote peer supports only the
default RPC-over-RDMA version 1 settings, as defined in [RFC8166]. default RPC-over-RDMA version 1 settings, as defined in [RFC8166].
In other words, the peer MUST behave as if a Private Data message was In other words, the peer MUST behave as if a Private Data message was
received in which bit 15 of the Flags field is zero, and both Size received in which (1) bit 15 of the Flags field is zero and (2) both
fields contain the value zero. Size fields contain the value zero.
5.2. Interoperability Amongst RDMA Transports 5.2. Interoperability amongst RDMA Transports
The Format Identifier field defined in Section 4 is provided to The Format Identifier field defined in Section 4 is provided to
enable implementations to distinguish RPC-over-RDMA version 1 Private enable implementations to distinguish the Private Data defined in
Data from private data inserted at other layers, such as the private this document from Private Data inserted at other layers, such as the
data inserted by the iWARP MPAv2 enhancement described in [RFC6581]. additional Private Data defined by the MPAv2 protocol described in
[RFC6581], and others.
As part of connection establishment, the received private data buffer As part of connection establishment, the buffer containing the
is searched for the Format Identifier word. The offset of the Format received Private Data is searched for the Format Identifier word.
Identifier is not restricted to any alignment. If the RPC-over-RDMA The offset of the Format Identifier is not restricted to any
version 1 CM Private Data Format Identifier is not present, an RPC- alignment. If the RPC-over-RDMA version 1 CM Private Data Format
over-RDMA version 1 receiver MUST behave as if no RPC-over-RDMA Identifier is not present, an RPC-over-RDMA version 1 receiver MUST
version 1 CM Private Data has been provided. behave as if no RPC-over-RDMA version 1 CM Private Data has been
provided.
Once the RPC-over-RDMA version 1 CM Private Data Format Identifier is Once the RPC-over-RDMA version 1 CM Private Data Format Identifier is
found, the receiver parses the subsequent octets as RPC-over-RDMA found, the receiver parses the subsequent octets as RPC-over-RDMA
version 1 CM Private Data. As additional assurance that the private version 1 CM Private Data. As additional assurance that the content
data content is valid RPC-over-RDMA version 1 CM Private Data, the is valid RPC-over-RDMA version 1 CM Private Data, the receiver should
receiver should check that the format version number field contains a check that the format version number field contains a valid and
valid and recognized version number and the size of the private data recognized version number and the size of the content does not
does not overrun the length of the buffer. overrun the length of the buffer.
6. Updating the Message Format 6. Updating the Message Format
Although the message format described in this document provides the Although the message format described in this document provides the
ability for the client and server to exchange particular information ability for the client and server to exchange particular information
about the local RPC-over-RDMA implementation, it is possible that about the local RPC-over-RDMA implementation, it is possible that
there will be a future need to exchange additional properties. This there will be a future need to exchange additional properties. This
would make it necessary to extend or otherwise modify the format would make it necessary to extend or otherwise modify the format
described in this document. described in this document.
Any modification faces the problem of interoperating properly with Any modification faces the problem of interoperating properly with
implementations of RPC-over-RDMA version 1 that are unaware of the implementations of RPC-over-RDMA version 1 that are unaware of the
existence of the new format. These include implementations that that existence of the new format. These include implementations that do
do not recognize the exchange of CM Private Data as well as those not recognize the exchange of CM Private Data as well as those that
that recognize only the format described in this document. recognize only the format described in this document.
Given the message format described in this document, these Given the message format described in this document, these
interoperability constraints could be met by the following sorts of interoperability constraints could be met by the following sorts of
new message formats: new message formats:
o A format which uses a different value for the first four bytes of * A format that uses a different value for the first four bytes of
the format, as provided for in the registry described in the format, as provided for in the registry described in
Section 8. Section 8.
o A format which uses the same value for the Format Identifier field * A format that uses the same value for the Format Identifier field
and a value other than one (1) in the Version field. and a value other than one (1) in the Version field.
Although it is possible to reorganize the last three of the eight Although it is possible to reorganize the last three of the
bytes in the existing format, extended formats are unlikely to do so. eight bytes in the existing format, extended formats are unlikely to
New formats would take the form of extensions of the format described do so. New formats would take the form of extensions of the format
in this document with added fields starting at byte eight of the described in this document with added fields starting at byte eight
format or changes to the definition of bits in the Reserved field. of the format or changes to the definition of bits in the Reserved
field.
7. Security Considerations 7. Security Considerations
The reader is directed to the Security Considerations section of The reader is directed to the Security Considerations section of
[RFC8166] for background and further discussion. [RFC8166] for background and further discussion.
The RPC-over-RDMA version 1 protocol framework depends on the The RPC-over-RDMA version 1 protocol framework depends on the
semantics of the Reliable Connected (RC) queue pair (QP) type, as semantics of the Reliable Connected (RC) queue pair (QP) type, as
defined in Section 9.7.7 of [IBA]. The integrity of CM Private Data defined in Section 9.7.7 of [IBA]. The integrity of CM Private Data
and the authenticity of its source are ensured by the exclusive use and the authenticity of its source are ensured by the exclusive use
of RC queue pairs. Any attempt to interfere with or hijack data in of RC QPs. Any attempt to interfere with or hijack data in transit
transit on an RC connection results in the RDMA provider terminating on an RC connection results in the RDMA provider terminating the
the connection. connection.
The Security Considerations section of [RFC5042] refers the reader to The Security Considerations section of [RFC5042] refers the reader to
further relevant discussion of generic RDMA transport security. That further relevant discussion of generic RDMA transport security. That
document recommends IPsec as the default transport layer security document recommends IPsec as the default transport-layer security
solution. When deployed with iWARP, IPsec establishes a protected solution. When deployed with the Remote Direct Memory Access
channel before any iWARP operations are exchanged, thus it protects Protocol (RDMAP) [RFC5040], DDP [RFC5041], and MPA [RFC5044], IPsec
the exchange of Private Data that occurs as each QP is established. establishes a protected channel before any operations are exchanged;
However, IPsec is not available for InfiniBand or RoCE deployments. thus, it protects the exchange of Private Data. However, IPsec is
Those fabrics rely on physical security and cyclic redundancy checks not available for InfiniBand or RDMA over Converged Ethernet (RoCE)
to protect network traffic. deployments. Those fabrics rely on physical security and cyclic
redundancy checks to protect network traffic.
Exchanging the information contained in the Private Message format Exchanging the information contained in the message format defined in
defined in this document does not expose upper-layer payloads to an this document does not expose upper-layer payloads to an attacker.
attacker. Furthermore, the behavior changes that occur as a result Furthermore, the behavior changes that occur as a result of
of processing the CM Private Data format described in the current exchanging the Private Data described in the current document do not
document do not introduce any new risk of exposure of upper-layer introduce any new risk of exposure of upper-layer payload data.
payload data.
Improperly setting one of the fields in a version 1 Private Message Improperly setting one of the fields in version 1 Private Data can
can result in an increased risk of disconnection (i.e., self-imposed result in an increased risk of disconnection (i.e., self-imposed
Denial of Service). A similar risk can arise if non-RPC-over-RDMA CM Denial of Service). A similar risk can arise if non-RPC-over-RDMA CM
Private Data inadvertently contains the Format Identifier that Private Data inadvertently contains the Format Identifier that
identifies this protocol's data structure. Additional checking of identifies this protocol's data structure. Additional checking of
incoming Private Data, as described in Section 5.2, can help reduce incoming Private Data, as described in Section 5.2, can help reduce
this risk. this risk.
In addition to describing the structure of a new format version, any In addition to describing the structure of a new format version, any
document that extends the Private Data format described in the document that extends the Private Data format described in the
current document must discuss security considerations of new data current document must discuss security considerations of new data
items exchanged between connection peers. Such documents should also items exchanged between connection peers. Such documents should also
explore the risks of erroneously identifying non-RPC-over-RDMA CM explore the risks of erroneously identifying non-RPC-over-RDMA CM
Private Data as the new format. Private Data as the new format.
8. IANA Considerations 8. IANA Considerations
In accordance with [RFC8126], the author requests that IANA create a IANA has created the "RDMA-CM Private Data Identifiers" subregistry
new registry in the "Remote Direct Data Placement" Protocol Category within the "Remote Direct Data Placement" protocol category group.
Group. The new registry is to be called the "RDMA-CM Private Data This is a subregistry of 32-bit numbers that identify the upper-layer
Identifier Registry". This is a registry of 32-bit numbers that protocol associated with data that appears in the application-
identify the upper-layer protocol associated with data that appears specific RDMA-CM Private Data area. The fields in this subregistry
in the application-specific RDMA-CM Private Data area. The fields in include the following: Format Identifier, Length (format length, in
this registry include: Format Identifier, Format Length (in octets), octets), Description, and Reference.
Description, and Reference.
The initial contents of this registry are a single entry: The initial contents of this registry are a single entry:
+---------------+--------+------------------------------+-----------+ +===================+========+=======================+===========+
| Format | Length | Description | Reference | | Format Identifier | Length | Description | Reference |
| Identifier | | | | +===================+========+=======================+===========+
+---------------+--------+------------------------------+-----------+ | 0xf6ab0e18 | 8 | RPC-over-RDMA version | RFC 8797 |
| 0xf6ab0e18 | 8 | RPC-over-RDMA version 1 CM | [RFC-TBD] | | | | 1 CM Private Data | |
| | | Private Data | | +-------------------+--------+-----------------------+-----------+
+---------------+--------+------------------------------+-----------+
Table 1: RDMA-CM Private Data Identifier Registry Table 1: New "RDMA-CM Private Data Identifiers" Registry
IANA is to assign subsequent new entries in this registry using the IANA is to assign subsequent new entries in this registry using the
Specification Required policy as defined in Section 4.6 of [RFC8126]. Specification Required policy as defined in Section 4.6 of [RFC8126].
8.1. Guidance for Designated Experts 8.1. Guidance for Designated Experts
The Designated Expert (DE), appointed by the IESG, should ascertain The Designated Expert (DE), appointed by the IESG, should ascertain
the existence of suitable documentation that defines the semantics the existence of suitable documentation that defines the semantics
and format of the private data, and verify that the document is and format of the Private Data, and verify that the document is
permanently and publicly available. Documentation produced outside permanently and publicly available. Documentation produced outside
the IETF must not conflict with work that is active or already the IETF must not conflict with work that is active or already
published within the IETF. The new Reference field should contain a published within the IETF. The new Reference field should contain a
reference to that documentation. reference to that documentation.
The Description field should contain the name of the upper-layer The Description field should contain the name of the upper-layer
protocol that generates and uses the private data. protocol that generates and uses the Private Data.
The DE should assign a new Format Identifier so that it does not The DE should assign a new Format Identifier so that it does not
conflict with existing entries in this registry, and so that it is conflict with existing entries in this registry and so that it is not
not likely to be mistaken as part of the payload of other registered likely to be mistaken as part of the payload of other registered
formats. formats.
The DE shall post the request to the nfsv4 WG mailing list (or a The DE shall post the request to the NFSV4 Working Group mailing list
successor to that list, if such a list exists), for comment and (or a successor to that list, if such a list exists) for comment and
review. The DE shall approve or deny the request and publish notice review. The DE shall approve or deny the request and publish notice
of the decision within 30 days. of the decision within 30 days.
9. References 9. References
9.1. Normative References 9.1. Normative References
[IBA] InfiniBand Trade Association, "InfiniBand Architecture [IBA] InfiniBand Trade Association, "InfiniBand Architecture
Specification Volume 1", Release 1.3, March 2015. Specification Volume 1", Release 1.3, March 2015,
<https://www.infinibandta.org/>.
Available from https://www.infinibandta.org/
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997, DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>. <https://www.rfc-editor.org/info/rfc2119>.
[RFC4506] Eisler, M., Ed., "XDR: External Data Representation [RFC4506] Eisler, M., Ed., "XDR: External Data Representation
Standard", STD 67, RFC 4506, DOI 10.17487/RFC4506, May Standard", STD 67, RFC 4506, DOI 10.17487/RFC4506, May
2006, <https://www.rfc-editor.org/info/rfc4506>. 2006, <https://www.rfc-editor.org/info/rfc4506>.
skipping to change at page 12, line 21 skipping to change at line 541
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>. May 2017, <https://www.rfc-editor.org/info/rfc8174>.
9.2. Informative References 9.2. Informative References
[RFC1813] Callaghan, B., Pawlowski, B., and P. Staubach, "NFS [RFC1813] Callaghan, B., Pawlowski, B., and P. Staubach, "NFS
Version 3 Protocol Specification", RFC 1813, Version 3 Protocol Specification", RFC 1813,
DOI 10.17487/RFC1813, June 1995, DOI 10.17487/RFC1813, June 1995,
<https://www.rfc-editor.org/info/rfc1813>. <https://www.rfc-editor.org/info/rfc1813>.
[RFC5041] Shah, H., Pinkerton, J., Recio, R., and P. Culley, "Direct
Data Placement over Reliable Transports", RFC 5041,
DOI 10.17487/RFC5041, October 2007,
<https://www.rfc-editor.org/info/rfc5041>.
[RFC5044] Culley, P., Elzur, U., Recio, R., Bailey, S., and J. [RFC5044] Culley, P., Elzur, U., Recio, R., Bailey, S., and J.
Carrier, "Marker PDU Aligned Framing for TCP Carrier, "Marker PDU Aligned Framing for TCP
Specification", RFC 5044, DOI 10.17487/RFC5044, October Specification", RFC 5044, DOI 10.17487/RFC5044, October
2007, <https://www.rfc-editor.org/info/rfc5044>. 2007, <https://www.rfc-editor.org/info/rfc5044>.
[RFC5531] Thurlow, R., "RPC: Remote Procedure Call Protocol [RFC5531] Thurlow, R., "RPC: Remote Procedure Call Protocol
Specification Version 2", RFC 5531, DOI 10.17487/RFC5531, Specification Version 2", RFC 5531, DOI 10.17487/RFC5531,
May 2009, <https://www.rfc-editor.org/info/rfc5531>. May 2009, <https://www.rfc-editor.org/info/rfc5531>.
[RFC5666] Talpey, T. and B. Callaghan, "Remote Direct Memory Access [RFC5666] Talpey, T. and B. Callaghan, "Remote Direct Memory Access
skipping to change at page 12, line 51 skipping to change at line 576
(NFS) Version 4 Protocol", RFC 7530, DOI 10.17487/RFC7530, (NFS) Version 4 Protocol", RFC 7530, DOI 10.17487/RFC7530,
March 2015, <https://www.rfc-editor.org/info/rfc7530>. March 2015, <https://www.rfc-editor.org/info/rfc7530>.
[RFC7861] Adamson, A. and N. Williams, "Remote Procedure Call (RPC) [RFC7861] Adamson, A. and N. Williams, "Remote Procedure Call (RPC)
Security Version 3", RFC 7861, DOI 10.17487/RFC7861, Security Version 3", RFC 7861, DOI 10.17487/RFC7861,
November 2016, <https://www.rfc-editor.org/info/rfc7861>. November 2016, <https://www.rfc-editor.org/info/rfc7861>.
Acknowledgments Acknowledgments
Thanks to Christoph Hellwig and Devesh Sharma for suggesting this Thanks to Christoph Hellwig and Devesh Sharma for suggesting this
approach, and to Tom Talpey and Dave Noveck for their expert comments approach, and to Tom Talpey and David Noveck for their expert
and review. The author also wishes to thank Bill Baker and Greg comments and review. The author also wishes to thank Bill Baker and
Marsden for their support of this work. Also, thanks to expert Greg Marsden for their support of this work. Also, thanks to expert
reviewers Sean Hefty and Dave Minturn. reviewers Sean Hefty and Dave Minturn.
Special thanks go to document shepherd Brian Pawlowski, Transport Special thanks go to document shepherd Brian Pawlowski, Transport
Area Director Magnus Westerlund, NFSV4 Working Group Chairs David Area Director Magnus Westerlund, NFSV4 Working Group Chairs David
Noveck and Spencer Shepler, and NFSV4 Working Group Secretary Thomas Noveck and Spencer Shepler, and NFSV4 Working Group Secretary Thomas
Haynes. Haynes.
Author's Address Author's Address
Charles Lever Charles Lever
 End of changes. 65 change blocks. 
190 lines changed or deleted 201 lines changed or added

This html diff was produced by rfcdiff 1.47. The latest version is available from http://tools.ietf.org/tools/rfcdiff/