INTERNET DRAFT V. Kashyap IBM Expiration Date: August 2003 February 2003 IP over InfiniBand: Connected Mode Status of this memo This document is an Internet-Draft and is in full conformance with all provisions of Section 10 of RFC 2026. 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 This memo provides information for the Internet community. This memo does not specify an Internet standard of any kind. Distribution of this memo is unlimited. Copyright Notice Copyright (C) The Internet Society (2001). All Rights Reserved. Abstract The InfiniBand Architecture(IBA) defines a high speed, channel based interconnect between systems and devices. IBA provides multiple modes of transport services with differing characteristics. This document describes IP over IBA's Connected transport modes. Kashyap [Page 1] INTERNET-DRAFT Connected mode IPoIB February 2003 Table of Contents 1.0 Introduction 2.0 IPoIB-connected mode 2.1 Outline of Address Resolution 2.2 Outline of Connection Setup 3.0 Address Resolution 4.0 Connection setup 4.1 Service ID 4.2 MTU 5.0 IP Encapsulation 6.0 Security Considerations 7.0 References 1.0 Introduction IBA defines two connected modes: 1. Reliable Connected(RC) 2. Unreliable Connected(UC) The two modes differ mainly, as is clear from the names, in providing reliability of data delivery across the connection. However, both these modes will be considered together in this document since all the discussion applies equally to both the modes - the two modes are referred to as IPoIB-CM (connected mode) in this document. IPoIB over reliable connected mode is referred to as IPoIB-RC whereas IPoIB over unreliable connected mode is referred to as IPoIB-UC. The connected modes offer link MTUs of upto 2^31 bytes in length. Thus the use of connected modes can offer significant benefits by supporting reasonably large MTUs. The datagram modes are limited to 4096 bytes. Reliability is also enhanced if the underlying feature of 'automatic path migration' supported by the connected modes is utilised [IBARCH]. This document presents a method of address resolution and transmission of IP packets over connected modes of IBA. 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. Kashyap [Page 2] INTERNET-DRAFT Connected mode IPoIB February 2003 2.0 IPoIB-connected mode The connected modes of IBA do not support multicasting though every node is capable of communicating i.e. setting a connection, to every other node in the InfiniBand(IB) network. This implies that intrinsically one cannot rely on native broadcast or multicast to send out the address resolution query. But an ARP server is not an efficient solution. Fortunately in the case of IPoIB-CM there is a way out. 2.1 Outline of Address Resolution IBA requires that all Host Channel Adapters(HCAs) support the reliable and unreliable connected modes. It is optional for Target Channel Adapters (TCAs) to supported the connected modes. At the same time IBA requires all HCAs and TCAs to support unreliable datagram mode. The unreliable datagram mode does support multicasting. IPoIB over unreliable datagram(IPoIB-UD) as presented in [IPoIB_MCAST]/[IPoIB_ENCAP] requires the IB subnet to support IB level multicast. The above makes it possible to use a multicast query for IPoIB-CM address resolution. The address resolution in IPoIB-CM networks uses an unreliable datagram(UD) queue pair(QP). IPoIB_ENCAP 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_ENCAP]. This document extends the requirement of joining the 'broadcast-GID' to IPoIB-CM too by associating an unreliable datagram with it. A broadcast-GID is formed with the knowledge of the scope bits, IP version and 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_MCAST]. An implementation MAY use the same unreliable datagram(UD) queue pair(QP) as used by the IPoIB-UD implementation if the latter mode is supported in the same partition and scope. Therefore during address resolution, the query is sent out on the broadcast GID. A unicast reply is received on the UD QP associated with IPoIB-CM. Kashyap [Page 3] INTERNET-DRAFT Connected mode IPoIB February 2003 2.2 Outline of Connection setup Address resolution is but the first step. Once the link address of the remote node is known a 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 [IBARCH]. It must also supply the queue pair to the remote node. The peer replies with its queue pair. Note that every connection is peer to peer and does not use shared queue pairs(QPs). Every connection uses a pair of unique (on the node) QPs. Though the address resolution occurs at an individual address level the connection between the nodes is at the IB layer and so, every individual address resolution does not imply a new connection between the peers. 3.0 Address Resolution Every IPoIB-CM node MUST join the broadcast-GID associated with the subnet. The address resolution query is always sent out on the broadcast-GID. IPoIB encapsulation [IPoIB_ENCAP] describes the link-layer address as follows: <1 octet reserved>:QP: GID This document extends the link-layer address as follows: :QP-cookie:GID QP-cookie: An IB connection, as noted above, uses a pair of QPs; one on each node. An implementation therefore cannot advertise the QP it intends to use as part of the address resolution query since such a message is seen by all members of the subnet. Instead an implementation specific, 3-octet long, QP-cookie is used. Kashyap [Page 4] INTERNET-DRAFT Connected mode IPoIB February 2003 The QP-cookie is used by the peer for two purposes: a. The QP-cookie is used to form the service-ID that is used in the IB connection messages. The receiver can, depending on the service-ID and thereby the QP-cookie make a decision on the QPN to create (or deny). b. The QP-cookie is used to determine if a connection already exists to the peer. In such a case the node can avoid an attempt at connection setup. Note that the GID cannot be used for this purpose since a GID can always be shared by multiple interfaces. Flags: This is a single octet field. If bit 0 is set then it implies that in the sender's view, the subnet is built over IB's 'reliable connected' i.e. RC mode. If bit 1 is set then it implies that the subnet is built over IB's 'unreliable connected' i.e. UC mode. All other bits in the octet are reserved and MUST be set to 0. Both the RC and UC flags MUST not be set at the same time. They are mutually exclusive. The receiver replies with its own link-address and the set of flags. If the flags do not match then there is a misconfiguration since the members of the same expect different link characteristics (IB modes). In such a case a suitable error indication SHOULD be provided to the administrator. The receiver's reply is unicast back to the sender after the receiver has, as in the case of IPoIB over unreliable datagram(IPoIB_UD), after it resolves the GID to the LID. Once the address resolution is completed the connection may be setup. 4.0 Connection Setup The 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 Kashyap [Page 5] INTERNET-DRAFT Connected mode IPoIB February 2003 connection setup. The service ID used when setting up the connection is derived from the QP cookie received during the address resolution process. A node MAY return the same cookie for multiple addresses. For example, the node might support multiple subnets over the same GID and prefer to make only one IB level connection. This includes supporting the same IB connection for both IPv4 and IPv6 to a peer node. The choice of the QP-cookie is implementation dependent. Therefore, the end initiating the connection needs to defer to the peer's choice. If the peer has returned the same QP-cookie as a result of multiple address resolution requests then, for those addresses, a connection attempt SHOULD not be made. This is true even if the requestor itself presented different QP-cookies, and would have created separate QPs if it had received the request instead. If a node does receive a connection request for the same service-ID from the same peer then it is upto the implementation to honour or reject it. 4.1 Service ID The InfiniBand specification defines a block of service IDs for IETF use. The InfiniBand specification has left the definition and management of this block to the IETF. The 64-bit block is: +--------+--------+--------+--------+--------+--------+--------+--------+ |00000001|<-------------------IETF use--------------------------------->| +--------+--------+--------+--------+--------+--------+--------+--------+ The ServiceIDs used by IPoIB will use the following format: +--------+--------+--------+--------+--------+--------+--------+--------+ |00000001|Reserved| 3-octet QP cookie |Reserved|Reserved|Reserved| +--------+--------+--------+--------+--------+--------+--------+--------+ The Reserved fields MUST be transmitted as zeroes. They are ignored on reception. 4.2 MTU The IB connection 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. If the connection is used for both IPv4 and IPv6, the link MTU MUST be able to support the minimum MTU Kashyap [Page 6] INTERNET-DRAFT Connected mode IPoIB February 2003 required by both IPv4 and IPv6. Every connection setup message includes a 'private data' field [IBARCH]. The private data field MUST carry the following information: 0 15 +----------------+ | Desired MTU | +----------------+ | Minimum MTU | +----------------+ The connection setup message (CM REQ) MUST insert the requested MTU in the 'Desired MTU' field and the minimum acceptable MTU. If it is not acceptable to the peer then it MUST indicate the preferred value in the 'desired MTU' when rejecting (CM REJ) the request. If the 'desired MTU' is lower than the minimum MTU that can be supported, the connection MUST be rejected (CM REJ message) with the minimum acceptable MTU in both the desired and minimum MTU fields. 5.0 IP encapsulation The IP encapsulation will be done as defined in the IPoIB encapsulation standard[IPoIB_ENCAP]. IP multicast cannot be done over the IPoIB-CM modes. 6.0 Security Considerations A node may be returned a false set of flags by an imposter. This may cause unnecessary attempts and some delay/disruption in IPoIB communication. The same is the case if wrong/spurious QP-cookie values are provided. Kashyap [Page 7] INTERNET-DRAFT Connected mode IPoIB February 2003 7.0 References [IB_ARCH] InfiniBand Architecture Specification, version 1.1 www.infinibandta.org [IPoIB_ARCH] draft-ietf-ipoib-architecture-01.txt, V. Kashyap [IPoIB_ENCAP] draft-ietf-ipoib-ip-over-infiniband-01.txt, V. Kashyap, H.K. Jerry Chu [IPoIB_MCAST] draft-ietf-ipoib-link-multicast-02.txt, H.K. Jerry Chu, V. Kashyap 7.0 Author's Address Vivek Kashyap 15450, SW Koll Parkway Beaverton, OR 97006 Phone: +1 503 578 3422 Email: vivk@us.ibm.com Full Copyright Statement Copyright (C) The Internet Society (2001). All Rights Reserved. This document and translations of it may be copied and furnished to others, and derivative works that comment on or otherwise explain it or assist in its implementation may be prepared, copied, published and distributed, in whole or in part, without restriction of any kind, provided that the above copyright notice and this paragraph are included on all such copies and derivative works. However, this document itself may not be modified in any way, such as by removing the copyright notice or references to the Internet Society or other Internet organizations, except as needed for the purpose of developing Internet standards in which case the procedures for copyrights defined in the Internet Standards process must be followed, or as required to translate it into languages other than English. The limited permissions granted above are perpetual and will not be revoked by the Internet Society or its successors or assigns. This document and the information contained herein is provided on an "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET Kashyap [Page 8] INTERNET-DRAFT Connected mode IPoIB February 2003 ENGINEERING TASK FORCE DISCLAIMS 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. 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