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iSER on SCTP & IB

This document generalizes the iSER specification to allow its usage with various RDMA capable protocols such as iWARP/SCTP, InfiniBand, etc. It aims to make the iSCSI-based protocol applicable across different networks and eliminate unnecessary management and discovery protocols. Examples of proposed changes are provided, including terminology clarification and adjustments for better applicability to different protocols.

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iSER on SCTP & IB

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  1. iSER on SCTP & IB draft-hufferd-ips-iser-sctp-ib-00.txt Generalizations to iSER specification John Hufferd Mike Ko Yaron Haviv

  2. Abstract • The iSCSI Extensions for RDMA document currently specifies the RDMA data transfer capability for iSCSI over iWARP/TCP • This new document generalizes the iSER document to permit it to be used with other RDMA capable protocols such as • iWARP/SCTP • InfiniBand • etc. • It also describes what should be defined in the InfiniBand Trade Association and what things are appropriate for specification in the IETF

  3. Motivation • Current wordage in iSER is only applicable to iSER on iWARP/TCP • It was felt that the protocol should be made generic for RDMA LLPs, and that includes: • iWARP/SCTP • InfiniBand • Etc. • Makes an iSCSI based protocol apply across more Networks, and eliminates some of the management and discovery protocols that would otherwise be needed • For example, would not have to fix the short comings of SRP (SCSI RDMA Protocol) on IB

  4. Goals • To specify changes/adjustments that should be considered to the wordage in the iSER document to make it more General • These changes should not modify the basic operation of iSCSI/iSER when operating on iWARP/TCP • Some of the terminology needed to be clarified as to the applicability of the terms to the actual LLP used

  5. Examples of changes (1) • The term “iWARP protocol suite” is replaced by “RDMA-Capable Protocol” • The term “iWARP layer” will be replaced by “RDMA-capable protocol layer” • Wherever the “iWARP” term is specific to the TCP implementation, it will be replaced with “iWARP/TCP” • The term “RNIC” will be replaced with “RDMA-Capable Controller” • The clause “such as an RNIC” will be added as needed

  6. Examples of changes (2) • The Steering Tag (STag) term will have its definition extended such at the IB “Local Steering Tag (L-Key)” and the “Remote Steering Tag (R-Key)” are included in the STag definition by way of example • The Definitions for IRD and ORD terms will have their definition extended such that the IB “Responder Resources”, and Initiator Depth” are included in the definitions by way of example • The Term RDMA-capable protocol (RCP) will be defined and used when ever any RDMA wire protocol or RDMA protocol stack is applicable • RDMAP should be used only when it explicitly refers the iWARP protocol (TCP or SCTP)

  7. Examples of changes (3) • The Term “RDMAP Stream” will be replaced by the term “RCP Stream” and defined as: • RCP Stream - A single bidirectional association between the peer RDMA-capable protocol layers on two Nodes over a single transport-level stream. • For TCP or SCTP, an RCP Stream is also known as an RDMAP Stream. • For iSER/TCP, the association is created when the connection transitions to iSER-assisted mode following a successful Login Phase during which iSER support is negotiated. • Needed since SCTP and IB start their RCP stream mode at connection time

  8. Examples of changes (4) • The term “RCP Message” should be defined and used as a replacement for the term “RDMAP Message” the definition will be: • RCP Message – The sequence of packets of the RDMA-capable protocol which represent a single RDMA operation or a part of RDMA Read Operation. For TCP or SCTP, an RCP Message is also known as an RDMAP Message • When discussing the iSER Hello and HelloReply Messages the term "iSER Message" will be used • Instead of “RDMAP Message” • This distinction is needed in order to accommodate LLPs that have native message delivery capability, such as SCTP or IB

  9. Example of Changes (5) • We permit the iSCSI layer (if appropriate) to use the RCP message mode capability immediately after connection establishment before enabling iSER-assisted mode • Appropriate for SCTP or IB • In this case the iSER Hello and HelloReply Messages are not the first RCP Messages, but they are the first iSER Messages • Added a discussion of connection establishment along with the use of the “RCP messaging protocol”, for exchanging Login Request and Login Response Messages • Examples are discussed that are appropriate for SCTP and IB, along with the transitioning of the connection to iSER mode

  10. Examples of changes (6) • The discussion of Security specifies that all non IP protocols will define their own requirements for IPsec • However the iSCSI requirements for IPsec are still required: • Wherever an iSER Message enters an IP environment from a non IP one (such as IB) • The iSCSI/iSER requirement for IPsec on IP based protocols such as TCP and SCTP • Will continue to require IPsec as a must implement

  11. Generic example of iSCSI/iSER layering in Full Feature Mode

  12. IB Informative Section • Information on how iSER would be used in an IB network is included in the Draft • Not intended to be included in the iSER draft unless included in an informational Appendix • Various Network topologies are shown • Host Side IB Network, including Gateways • Storage Side that includes iSER/IB • IB iSER discovery process is described • Use of IP over IB (IPoIB) • SendTargets • SLP • iSNS • Conversion of IP address into IB GID via ARP processes • Discussion of what the IBTA needs to define

  13. Host Side iSER/IB Topology

  14. Storage Side with iSER/IB

  15. Info: What the IBTA needs to define • Means for permitting a Host to establish an iSCSI/iSER connection with a peer InfiniBand end-node • Indicating when that end node does not support iSER • So the Host would be able to fall back to iSCSI/TCP over IPoIB • Means for permitting the Host to establish connections with • IB iSER connections on Storage Controllers or • IB iSER connected Gateways in preference to IPoIB connected Gateways/Bridges or • Connections to Target Storage Controllers that accept iSCSI via IPoIB • How to operate in an environment where ZBTO, and SendInvSE are optional • iSER ServiceID • How the ServiceID can be added to the IP port number during the connection process

  16. Info: Key Implementation areas that do NOT require IBTA specification • How implementations determine which iSCSI/iSER portal group to use • Basing the decision on new information that may be placed in the iSCSI discovery information is Not required • Simple trial selection is acceptable • How implementations determine how to best handle the concept of MC/S as it deals with multiple IB Addresses:Ports per Portal Group

  17. Preferred Change to Discovery Data • Useful to have a connection type associated with the Portal Group Tag • Will permit the most appropriate connections to be made without needless connection tries and failures • Useful for iSER/iWARP/TCP • Useful for iSER/iWARP/SCTP • Useful for iSER/IB • Proposed Syntax • IP Address:Port[, PG#[, Type#]] Portal Group Type IANA Portal Group Type Value iSCSI 0, or blank iSER/iWARP/TCP 1 iSER/iWARP/SCTP 2 iSER/iWARP/IB 3

  18. Recommendations • Have Mike Ko update the iSER wordage as indicated by this draft • Include the IB sections as Informational Appendices in iSER draft • Send Discovery Data changes to the authors of iSCSI, iSNS, & SLP for iSCSI

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