INTERNET DRAFT V. Kashyap IBM Expiration Date: December 2004 June 2004 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 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 June 2004 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 Security Considerations 7.0 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_ENCAP]. 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_ENCAP] 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 optional for Target Channel Adapters (TCAs) to support the connected modes. Kashyap [Page 2] INTERNET-DRAFT Connected mode IPoIB June 2004 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 by 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 This document extensively refers to [IPoIB_ENCAP] and extends IPoIB description given in [IPoIB_ENCAP] 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_ENCAP]. 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 IBA requires all channel adapters to support the UD mode, every implementation supporting IPoIB-CM will also be able to utilize UD QPs. Multicast mapping, transmission and reception of multicast packets and multicast routing is over the UD QP associated with the IPoIB-CM interface in accordance with the document [IPoIB_ENCAP]. 2.2 Outline of Address Resolution Every IPoIB-CM interface MUST have two QPs associated with it: Kashyap [Page 3] INTERNET-DRAFT Connected mode IPoIB June 2004 1) A connected mode QP 2) An unreliable datagram mode 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 requiring every IPoIB-CM interface to "FullMember" join the broadcast-GID using the associated UD QP. 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_ENCAP]. 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 UD QP associated with the IPoIB-CM interface. A unicast reply is received on the UD QP associated with the IPoIB-CM interface. An IPoIB-CM implementation MAY use the same UD QP as used by the IPoIB-UD implementation if the latter mode is supported in the same partition and scope. Kashyap [Page 4] INTERNET-DRAFT Connected mode IPoIB June 2004 3.1 Link-layer Address 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: :QPN: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. If IPoIB-CM is not supported i.e. if the implementation only supports IPoIB-UD, then the implementation MUST ignore the on reception. It MUST set the octet to all zeroes as specified in [IPoIB_ENCAP]. Both the RC and UC flags MUST not be set at the same time. They are mutually exclusive. 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 of the InfiniBand modes at any time. 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 to be used Kashyap [Page 5] INTERNET-DRAFT Connected mode IPoIB June 2004 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. 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. 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 SHOULD NOT attempt another connection to the remote peer using the same Service-ID as used for an existing IB connection. Kashyap [Page 6] INTERNET-DRAFT Connected mode IPoIB June 2004 3.3 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 UD QP exchanged during address resolution. The Type MUST be set to 0. The service-ID formed using the UD QPN used for address resolution MUST be supported by the associated interface. 4.0 Frame Format All IP and ARP datagrams transported over InfiniBand are prefixed by a 4-octet encapsulation header as described in [IPoIB_ENCAP]. 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 | | | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Kashyap [Page 7] INTERNET-DRAFT Connected mode IPoIB June 2004 The type field SHALL indicate the encapsulated protocol as per 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. The 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. At the same time 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 request/accept MTUs across an IB connection. 5.1 Per-Connection MTU Every IB connection setup message includes a "private data" Kashyap [Page 8] INTERNET-DRAFT Connected mode IPoIB June 2004 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. The "Minimum MTU" value SHOULD NOT be less than the MTU set for multicast communication i.e. the MTU received on "FullMember" join of the broadcast-GID on the associated UD QP. The "Desired" and "Minimum" MTUs may be set to the same value. If the "Desired MTU" is not acceptable to the peer then it MUST indicate it's 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. 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 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. 7.0 References [IB_ARCH] InfiniBand Architecture Specification, version 1.1 www.infinibandta.org [IPoIB_ARCH] draft-ietf-ipoib-architecture-04.txt, V. Kashyap [IPoIB_ENCAP] draft-ietf-ipoib-ip-over-infiniband-06.txt, H.K. Jerry Chu, V. Kashyap Kashyap [Page 9] INTERNET-DRAFT Connected mode IPoIB June 2004 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 (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 10]