INTERNET DRAFT V. Kashyap <draft-ietf-ipoib-connected-mode-00.txt> IBM Expiration Date: February 2005 August 2005 IP over InfiniBand: Connected Mode Status of this memo By submitting this Internet-Draft, I certify that any applicable patent or other IPR claims of which I am aware have been disclosed, or will be disclosed, and any of which I become aware will be disclosed, in accordance with RFC 3668. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet- Drafts. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." The list of current Internet-Drafts can be accessed at http://www.ietf.org/ietf/1id-abstracts.txt. The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html. Copyright Notice Copyright (C) The Internet Society (2001). All Rights Reserved. Abstract This document specifies a method for transmitting IPv4/IPv6 packets and address resolution over the connectd modes of InfiniBand. Kashyap [Page 1]
INTERNET-DRAFT Connected mode IPoIB February 2005 Table of Contents 1.0 Introduction 2.0 IPoIB-connected mode 2.1 Multicasting 2.2 Outline of Address Resolution 2.3 Outline of Connection Setup 3.0 Address Resolution 3.1 Link-layer Address 3.2 IB Connection Setup 3.3 Service-ID 4.0 Frame Format 5.0 Maximum Transmission Unit 5.1 Per-Connection MTU 6.0 IPoIB-CM Considerations 6.1 A Cautionary Note on IPoIB-RC 7.0 Security Considerations 8.0 IANA Considerations 9.0 References 1.0 Introduction The InfiniBand specification [IB_ARCH] can be found at www.infinibandta.org. The document [IPoIB_ARCH] provides a short overview of InfiniBand architecture along with consideration for specifying IP over InfiniBand networks. The InfiniBand architecture (IBA) defines multiple modes of transports. Of these the unreliable datagram (UD) transport method best matches the needs of IP. IP over InfiniBand (IPoIB) over UD is described in [IPoIB_UD]. This document describes IP transmission over the connected modes of IBA. IBA defines two connected modes: 1. Reliable Connected (RC) 2. Unreliable Connected (UC) As is evident from the nomenclature, the two modes differ mainly in providing reliability of data delivery across the connection. This document applies equally to both the connected modes. IPoIB over these two modes is referred to as IPoIB-CM (connected mode) in this document. For clarity IPoIB over the unreliable datagram mode, as described in [IPoIB_UD] is referred to as IPoIB-UD. IBA requires that all Host Channel Adapters (HCAs) support the reliable and unreliable connected modes [IB_ARCH]. It is Kashyap [Page 2]
INTERNET-DRAFT Connected mode IPoIB February 2005 optional for Target Channel Adapters (TCAs) to support the connected modes. The connected modes offer link MTUs of up to 2^31 octets in length. Thus the use of connected modes can offer significant benefits by supporting reasonably large MTUs. The datagram modes of InfiniBand Architecture (IBA) are limited to 4096 octets. Reliability is also enhanced if the underlying feature of "automatic path migration" supported by the connected modes is utilized. 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. 2.0 IPoIB-connected mode Every IPoIB implementation MUST support IPoIB-UD. The IPoIB-CM support is OPTIONAL. This document extensively refers to [IPoIB_UD] and extends IPoIB description given in [IPoIB_UD] to IPoIB-CM. Therefore, only additional requirements or enhancements needed to enable IPoIB- CM are described. The IP encapsulation, default MTU, link layer address format and the IPv6 stateless autoconfiguration mechanism apply to IPoIB-CM exactly as described in [IPoIB_UD]. 2.1 Multicasting The connected modes of IBA define a non-broadcast, multiple access network. The connected modes of IBA do not support multicasting though every node can communicate with every other node if desired. This requires that multicasting be emulated in some form by the network. However, in the case of an InfiniBand network, instead of an emulation, an unreliable datagram (UD) queue pair (QP) can be used to support multicasting while the connected mode QP is used for unicast traffic. Since every IPoIB implementation is required to support the UD mode, every implementation supporting IPoIB-CM will be able to utilize coexisting IPoIB-UD QP for all broadcast/multicast communications. Multicast mapping, transmission and reception of multicast Kashyap [Page 3]
INTERNET-DRAFT Connected mode IPoIB February 2005 packets and multicast routing MUST use the IPoIB-UD QP associated with the IPoIB-CM interface. 2.2 Outline of Address Resolution Every IPoIB-CM interface MUST have two QPs associated with it: 1) A connected mode QP 2) An unreliable datagram mode QP [IPoIB_UD] proposes that the address resolution query is multicast over an IB multicast address that is joined by every member of the IPoIB subnet. This IB multicast address is referred to as the "broadcast-GID" [IPoIB_UD]. The "broadcsat- GID" is "FullMember" joined by every IPoIB-UD implementation on the associated QP [IPoIB-UD]. A broadcast-GID is formed with the knowledge of the scope bits, IP version, the partition key (P_Key) associated with the subnet. Thus these three parameters must be known to the node before an IPoIB interface can be brought up. The exact format and rules to setup the broadcast-GID are defined in [IPoIB_UD]. In response to the query the response is received on the IPoIB- UD QP [IPoIB_UD]. 2.3 Outline of Connection setup Once the link address of the remote node is known an IB connection must be setup between the nodes before any IP communication may occur. To make a connection, the sender must know the service-ID to use in the request to make a connection [IB_ARCH]. It must also supply the "connection mode" queue pair to the remote node. The peer replies with its queue pair. Each IB connection is peer to peer and uses one connected mode QP at each end. Though the address resolution occurs at an individual IP address level the connection between the nodes is at the IB layer. Therefore every individual address resolution does not imply a new connection between the peers. 3.0 Address Resolution Address resolution queries are sent out on the "broadcast-GID" over the IPoIB-UD QP associated with the IPoIB-CM interface. A unicast reply is received on the UD QP. Kashyap [Page 4]
INTERNET-DRAFT Connected mode IPoIB February 2005 3.1 Link-layer Address IPoIB encapsulation [IPoIB_UD] describes the link-layer address as follows: <1 octet reserved>:QP: GID This document extends the link-layer address as follows: <Flags>:QPN:GID Flags: This is a single octet field. The bits indicate the connected modes supported by the interface. Bit 0 specifies the support for the "reliable connected" (RC) mode. Bit 1 indicates the support for the "unreliable connected" (UC) mode. All other bits in the octet are reserved and MUST be set to 0 on transmits and ignored on receives. The format of the flags is: +--+--+--+--+--+--+--+--+ |RC|UC| 0| 0| 0| 0| 0| 0| +--+--+--+--+--+--+--+--+ Both the RC and UC MAY be set at the same time if the interface supports both the modes. Since the IPoIB-UD mode is always supported there are no flags to indicate IPoIB-UD support. If IPoIB-CM is not supported i.e. if the implementation only supports IPoIB-UD, then the implementation MUST ignore the <Flags> on reception. It MUST set the <Flags> octet to all zeroes on transmission as specified in [IPoIB_UD]. QPN: The queue-pair number (QPN) on which the unicast address resolution reply will be received. This allows the IPoIB-UD address resolution code and method to be used for IPoIB-CM address resolution. The QPN also serves another purpose. It is used to form the Service-ID that is used to setup the IB connection. On receiving the multicast/broadcast address resolution request Kashyap [Page 5]
INTERNET-DRAFT Connected mode IPoIB February 2005 the receiver replies with its own link-address, including the associated UD QPN and the appropriate flags. The receiver's reply is unicast back to the sender after the receiver has, as in the case of IPoIB-UD, resolved the GID to the LID and determined other required parameters [IPoIB_UD]. Once the address resolution is completed the underlying IB connection on the supported connection modes can be set up. An implementation is NOT REQUIRED to setup a connection merely because the peer indicates the capability. The decision to make such a connection is left to the implementation. 3.2 IB Connection Setup The IB reliable/unreliable mode connection may be setup by any of the peers though it is more likely that the one that initiated the address resolution phase, probably as a result of the need to send IP data, will initiate the connection setup. IBA allows passive-active and active-active connection setup [IB_ARCH]. To setup a connection IB Management Datagrams (MADs) are directed to the peer's communication manager (CM). The connection request always contains a Service-ID for the peer to associate the request with the appropriate entity. If the request is accepted the peer returns the relevant connected mode QPN in the response MAD. The format of the CM connection messages and the IB connection setup process is described in [IB_ARCH]. The CM messages include, among other parameters, the Service-ID, Local QPN, and the payload size to use over the connection. Note: The IB connection is setup using the Service-ID as defined above. The node MUST keep a record of IB connections it is participating in. The node MAY attempt another connection to the remote peer using the same Service-ID as used for an existing IB connection. Similarly, the receiver of such a connection MAY drop the request with a suitable error indication in the CM response. The decision to accept or initiate multiple connections from or to an IPoIB interface is left to the implementation. 3.3 Service-ID The InfiniBand specification defines a block of service IDs for Kashyap [Page 6]
INTERNET-DRAFT Connected mode IPoIB February 2005 IETF use. The InfiniBand specification has left the definition and management of this block to the IETF [IB_ARCH]. The 64-bit block is: +--------+--------+--------+--------+-------+--------+--------+------+ |00000001|<-------------------IETF use------------------------------>| +--------+--------+--------+--------+-------+--------+--------+------+ The Service-IDs used by IPoIB will be in the format: +--------+--------+--------+--------+-------+-------+--------+-------+ |00000001| Type | Reserved | QPN | +--------+--------+--------+--------+-------+-------+--------+-------+ The Reserved fields MUST be transmitted as zeroes. They are ignored on reception. The QPN MUST be the UD QP exchanged during address resolution. The Type MUST be set to 0. 4.0 Frame Format All IP and ARP datagrams transported over InfiniBand are prefixed by a 4-octet encapsulation header as described in [IPoIB_UD]. 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | | | Type | Reserved | | | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ The type field SHALL indicate the encapsulated protocol as per Kashyap [Page 7]
INTERNET-DRAFT Connected mode IPoIB February 2005 the following table. +----------+-------------+ | Type | Protocol | |------------------------| | 0x800 | IPv4 | |------------------------| | 0x806 | ARP | |------------------------| | 0x8035 | RARP | |------------------------| | 0x86DD | IPv6 | +------------------------+ These values are taken from the "ETHER TYPE" numbers assigned by Internet Assigned Numbers Authority (IANA). Other network protocols, identified by different values of "ETHER TYPE", may use the encapsulation format defined herein but such use is outside of the scope of this document. 5.0 Maximum Transmission Unit The IB connection setup might be used for both IPv4 and IPv6 or it could be used for only one of them while a different connection is used for the other. The link MTU MUST be able to support the minimum MTU required by the protocols. The default MTU of the IPoIB-CM interface is 2044 octets i.e. 2048 octet IPoIB-link MTU minus the 4 octet encapsulation header. However, connected modes of InfiniBand allow message sizes up to 2^31 octets. Therefore, IPoIB-CM can use a much larger MTU for unicast communication between any two endpoints. The maximum and/or optimal payload that can be received or sent over an InfiniBand connection is dependent on the implementation, HCA and the resources configured. An implementation MAY utilise the following mechanism to exchange the optimal message size across the IB connection. 5.1 Per-Connection MTU Every IB connection setup message includes a "private data" field [IB_ARCH]. The private data field MUST carry the following Kashyap [Page 8]
INTERNET-DRAFT Connected mode IPoIB February 2005 information: 0 15 +----------------+ | Receive MTU | +----------------+ The connection setup message (CM REQ) MUST insert the requested MTU in the "Receive MTU" field. This indicates the maximum packet sze the requester can accept. The requester MUST be able to accept smaller MTU sizes as well. It is up to the implementation to utilize this mechanism for setting the per IB connection MTU. The IPoIB interface must account for the 4-octet encapsulation header and so the IPoIB MTU over the connection will be smaller by that amount. 6.0 IPoIB-CM Considerations Every IPoIB interface supports IPoIB-UD. It may additionally support one or both of IPoIB-CM modes. Therefore, there can be multiple methods of communicating between any two peers. This implies that an interface MAY transmit/receive a packet over any of the RC, UC or UD modes depending on the modes supported between it and the peer. It further follows that every IPoIB implementation compliant with this document MUST accept all unicast transmissions over any fo the IPoIB modes it supports. Multicast and broadcast packets by their nature will always be transmitted and received over the IPoIB-UD QP. 6.1 A Cautionary Note on IPoIB-RC The RC mode of InfiniBand guarantees in-order delivery of packets. Every message transmitted over the RC connection is broken into physical MTU sized packets by the RC connection. If any packet is lost, it is retransmitted until the complete message is exchanged. Therefore there is a possibility of a reliable transport layer, such as TCP, retransmitting due to a shorter timeout while the RC layer is still in the process of transferring the complete message. A retransmission at the upper layer will add to the already existing congestion. Therefore, the RC timers as well as the maximum message size supported at the IPoIB-RC connection must be set judiciously. 7.0 Security Considerations A node may be returned a false set of flags by an impostor. This Kashyap [Page 9]
INTERNET-DRAFT Connected mode IPoIB February 2005 may cause unnecessary attempts and some delay/disruption in IPoIB communication. The same is the case if wrong/spurious QPN values are provided during address resolution broadcast/multicast. 8.0 IANA Considerations This document requires that the reserved bits and octets be set to zero on sends and ignored on receives. Proposed uses of the reserved bits MUST be published as RFCs. 9.0 References Normative [IB_ARCH] InfiniBand Architecture Specification, version 1.1 www.infinibandta.org [IPoIB_ARCH] draft-ietf-ipoib-architecture-04.txt, V. Kashyap [IPoIB_UD] draft-ietf-ipoib-ip-over-infiniband-06.txt, H.K. Jerry Chu, V. Kashyap Author's Address Vivek Kashyap 15350, SW Koll Parkway Beaverton, OR 97006 Phone: +1 503 578 3422 Email: vivk@us.ibm.com Full Copyright Statement Copyright (C) The Internet Society (2004). This document is subject to the rights, licenses and restrictions contained in BCP 78 and except as set forth therein, the authors retain all their rights. This document and the information contained herein are provided on an "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. Kashyap [Page 10]
INTERNET-DRAFT Connected mode IPoIB February 2005 Intellectual Property The IETF takes no position regarding the validity or scope of any Intellectual Property Rights or other rights that might be claimed to pertain to the implementation or use of the technology described in this document or the extent to which any license under such rights might or might not be available; nor does it represent that it has made any independent effort to identify any such rights. Information on the procedures with respect to rights in RFC documents can be found in BCP 78 and BCP 79. Copies of IPR disclosures made to the IETF Secretariat and any assurances of licenses to be made available, or the result of an attempt made to obtain a general license or permission for the use of such proprietary rights by implementers or users of this specification can be obtained from the IETF on-line IPR repository at http://www.ietf.org/ipr. The IETF invites any interested party to bring to its attention any copyrights, patents or patent applications, or other proprietary rights that may cover technology that may be required to implement this standard. Please address the information to the IETF at ietf-ipr@ietf.org. Acknowledgement Funding for the RFC Editor function is currently provided by the Internet Society. Kashyap [Page 11]
