INTERNET DRAFT V. Kashyap IBM Expiration Date: March 2004 September 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 September 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 evident from the nomenclature, 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. IPoIB over reliable connected mode is referred to as IPoIB-RC whereas IPoIB over unreliable connected mode is referred to as IPoIB-UC where applicable. For clarity IPoIB over the unreliable datagram mode, as described in [IPoIB_ENCAP] and [IPoIB_MCAST], is referred to as IPoIB-UD. The connected modes offer link MTUs of up to 2^31 bytes in length. Thus the use of connected modes can offer significant benefits by supporting reasonably large MTUs. The datagram modes of IBA are limited to 4096 bytes. Reliability is also enhanced by the underlying feature of 'automatic path migration' supported by the connected modes is utilised [IB_ARCH]. 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. 2.0 IPoIB-connected mode The connected modes of IBA define a non-broadcast, multiple access Kashyap [Page 2] INTERNET-DRAFT Connected mode IPoIB September 2003 network - the connected modes of IBA do not support multicasting though every node can communicate with every other node if desired. 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 as explained below. 2.1 Outline of Address Resolution IBA requires that all Host Channel Adapters(HCAs) support the reliable and unreliable connected modes[IB_ARCH]. It is optional for Target Channel Adapters (TCAs) to support 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. Therefore it is possible to use a multicast query over IB-UD for IPoIB-CM address resolution. [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 queue-pair with every IPoIB-CM interface. 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_MCAST]. 2.2 Outline of Connection setup Address resolution is but the first step. 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 queue pair to the remote node. The peer replies with its queue pair. Note that each IB connection is peer to peer and uses one Kashyap [Page 3] INTERNET-DRAFT Connected mode IPoIB September 2003 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 Every IPoIB-CM node MUST join the broadcast-GID associated with the subnet [IPoIB_MCAST]. This join is over an UD QP. The address resolution query is always sent out on the broadcast-GID. An IPoIB-CM 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 the address resolution query is sent to the broadcast-GID on the associated UD QP. A unicast reply is received on the UD QP associated with IPoIB-CM. Note: The IPoIB-CM link need not be the same as the link defined by IPoIB-UD. In other words the broadcast-GID used for an IPoIB-CM is independent of other broadcast-GIDs supported over the same IB subnet. It MAY be the same but is not required to be the same. 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:GID 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. Kashyap [Page 4] INTERNET-DRAFT Connected mode IPoIB September 2003 The format of the flags is: +--+--+--+--+--+--+--+--+ |RC|UC| 0| 0| 0| 0| 0| 0| +--+--+--+--+--+--+--+--+ Note: The above implies that a given IP subnet can only be supported on one InfiniBand mode. If the link layer includes no flags then it is part of an IPoIB-UD subnet, if the link layer includes the RC flag then it is part of an IPoIB-RC subnet, if the link layer includes the UC flag then it is part of an IPoIB-UC subnet. 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 can 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 the receiver replies with its own link-address, including the associated UD QPN and the appropriate flag. If the flags do not match then there is a misconfiguration since the underlying IB modes do not match. 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), resolved the GID to the LID and determined other required parameters[IPoIB_ENCAP]. Once the address resolution is completed the underlying IB connection can be setup. 4.0 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. To setup a connection IB Management Datagrams (MADs) are directed Kashyap [Page 5] INTERNET-DRAFT Connected mode IPoIB September 2003 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. This content of the CM connection messages and the IB connection setup 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 SHOULD NOT attempt another connection to the remote peer using the same Service-ID as used for an existing IB connection. 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[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 | Reserved | +--------+--------+--------+--------+--------+--------+--------+--------+ The Reserved fields MUST be transmitted as zeroes. They are ignored on reception. The QPN MUST be the value exchanged during address resolution. The Type MUST be set to 0. Note: The service-ID formed using the UD QPN used for address resolution MUST be supported by the associated interface. 4.2 MTU The IB connection setup might be used for both IPv4 and IPv6 or it Kashyap [Page 6] INTERNET-DRAFT Connected mode IPoIB September 2003 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. Every connection setup message includes a 'private data' field[IB_ARCH]. 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 in the 'Minimum MTU' field. 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 set 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. Multicast traffic MUST be transmitted over the UD QP associated with the IPoIB-CM interface. 6.0 Security Considerations A node may be returned a false set of flags by an impostor. This 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. The same precautions MUST be taken as described in the 'security considerations' section of [IPoIB_MCAST] and [IPoIB_ENCAP] . 7.0 References [IB_ARCH] InfiniBand Architecture Specification, version 1.1 www.infinibandta.org Kashyap [Page 7] INTERNET-DRAFT Connected mode IPoIB September 2003 [IPoIB_ARCH] draft-ietf-ipoib-architecture-02.txt, V. Kashyap [IPoIB_ENCAP] draft-ietf-ipoib-ip-over-infiniband-04.txt, V. Kashyap, H.K. Jerry Chu [IPoIB_MCAST] draft-ietf-ipoib-link-multicast-04.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 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. Kashyap [Page 8] INTERNET-DRAFT Connected mode IPoIB September 2003 Kashyap [Page 9]