INTERNET DRAFT Vivek Kashyap <draft-ietf-ipoib-dhcp-over-infiniband-07.txt> IBM Expiration Date: May 2005 November 2004 DHCP over InfiniBand 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 (C) The Internet Society (2001). All Rights Reserved. Abstract An InfiniBand network uses a link-layer addressing scheme that is 20-octets long. This is larger than the 16-octets reserved for the hardware address in DHCP/BOOTP message. The above inequality imposes restrictions on the use of the DHCP message fields when used over an IP over InfiniBand(IPoIB) network. This document describes the use of DHCP message fields when implementing DHCP over IPoIB. 1. Introduction The Dynamic Host Configuration Protocol(DHCP) provides a framework Kashyap [Page 1]
INTERNET-DRAFT DHCP over InfiniBand November 2004 for passing configuration information to hosts on a TCP/IP network [RFC2131]. DHCP is based on the Bootstrap Protocol (BOOTP) [RFC951] adding the capability of automatic allocation of reusable network addresses and additional configuration options [RFC2131,RFC2132]. The DHCP server receives a broadcast request from the DHCP client. The DHCP server uses the client interface's hardware-address to unicast a reply back when the client doesn't yet have an IP address assigned to it. The "chaddr" field in the DHCP message carries the client's hardware address. The "chaddr" field is 16-octets in length. The IPoIB link-layer address is 20-octets in length. Therefore the IPoIB link-layer address will not fit in the "chaddr" field making it impossible for the DHCP server to unicast a reply back to the client. To ensure interoperability the usage of the fields and the method for DHCP interaction must be clarified. This document describes the IPoIB specific usage of some fields of DHCP. See [RFC2131] for the mechanism of DHCP and the explanations of each field. 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 [RFC2119]. 2. The DHCP over IPoIB mechanism As is noted above, the link-layer address is unavailable to the DHCP server because it is larger than the "chaddr" field length. Therefore, a DHCP client MUST request that the server sends a broadcast reply by setting the BROADCAST flag when IPoIB ARP is not possible, i.e. in situations where the client does not know its IP address. [RFC1542] notes that the use of a broadcast reply is discouraged. But in the case of IPoIB this is a necessity. There is no option but to broadcast back to the client since it is not possible to reply the client's unicast address. To desynchronise broadcasts at subnet startup, [RFC2131] suggests that a client wait a random time (1 to 10 seconds) before initiating server discovery. The same timeout will equally spread out the DHCP server broadcast responses generated due to the use of the use of the BROADCAST bit. The client hardware address, "chaddr", is unique in the subnet and hence can be used to identify the client interface. But in the absence of a unique "chaddr", another unique client identifier must be used. Kashyap [Page 2]
INTERNET-DRAFT DHCP over InfiniBand November 2004 The DHCP protocol states that the "client-identifier" option may be used as the unique identifying value for the client. This value must be unique within the subnet the client is a member of. The "client-identifier" option includes a type and identifier pair. The identifier included in the "client-identifier" option may consist of a hardware address or any other unique value such as the DNS name of the client. When a hardware address is used, the type field should be one of the ARP hardware types listed in [ARPPARAM]. 2.1 IPoIB specific usage of DHCP message fields A DHCP client, when working over an IPoIB interface, MUST follow the following rules: "htype" (hardware address type) MUST be 32 [ARPPARAM] "hlen" (hardware address length) MUST be 0. "chaddr" (client hardware address) field MUST be zeroed. "client-identifier" option MUST be used in DHCP messages. According to [RFC2132] the "client-identifier" option MAY consist of any data, but IPoIB clients SHOULD use the format discussed below for the client-identifier option. Note: This document does not preclude the use of other "client identifier" type, such as fully qualified domain name(FQDN) or the EUI-64 value associated with the interface. 2.1.1 Client-identifier values Every IPoIB interface is associated with an identifier referred to as the GID [IPoIB_ARCH]. A GID is formed by appending the port's EUI-64 identifier to the InfiniBand subnet prefix. An invariant GID is formed when the port's manufacturer assigned EUI-64 value is used to form the GID. A port might have additional EUI-64 values assigned to it by the subnet-manager(SM) [IBARCH]. Therefore a port can have multiple GIDs associated with it. A GID is unique in the InfiniBand fabric. The GID is associated with a particular hardware port. The GID and a QPN define an IPoIB interface at the port[IPOIB_ENCAP]. Therefore an implementation could associate multiple IPoIB interfaces on the same port by utilising a common GID but different QPNs. In such a case the GID is shared between multiple interfaces, and therefore, Kashyap [Page 3]
INTERNET-DRAFT DHCP over InfiniBand November 2004 the client identifier formed from just the GID is no longer unique in the IP subnet. This is not an issue if the interfaces sharing the GID are in different InfiniBand partitions, and thereby on different IPoIB links, since the client identifier need only be unique within a subnet. However, if the GID is shared by interfaces within the same partition the implementation MUST ensure a unique client identifier. For example, a unique client-identifier may be formed by including the QPN associated with the relevant IPoIB interface if the implementation is designed to keep this association constant across boots. Some other value unique to the implementation may also be used for the same purpose. If there is only one IPoIB interface associated with a particular GID within a partition, then use of the GID is sufficient. Since a port may be associated with multiple GIDs, multiple IPoIB interfaces may exist on the same port while using a different GID from among the GIDs associated with the port. In such a case too the GID can form a unique client identifier. Therefore, one of the following formats SHOULD be used for the "client-identifier" option. 1. If the QPN is used to distinguish between interfaces using the same GID. Code Len Type |<---------------- Client-Identifier -------------->| +-----+-----+-----+-----+-----+-----+-----+-------------------....----+ | 61 | 21 | 32 | 20 octets(link-layer address) | +-----+-----+-----+-----+-----+-----+-----+-------------------....----+ 2. A unique value, other than the QPN, may be used to distinguish between interfaces using the same GID. In this case a "type" of 0 MUST be specified since the "client identifier" is not a hardware address [RFC2132]. Code Len Type |<---------------- Client-Identifier -------------->| +-----+-----+-----+-----+-----+-----+-----+-------------------....----+ | 61 | 21 | 00 | Unique-value(4 octets)| 16 octet GID | +-----+-----+-----+-----+-----+-----+-----+-------------------....----+ Kashyap [Page 4]
INTERNET-DRAFT DHCP over InfiniBand November 2004 But if the GID is not shared with another IPoIB interface then there is no need for another "unique-value". In such a case the GID suffices by itself. Code Len Type |<---------------- Client-Identifier -------------->| +-----+-----+-----+-----+-----+-----+-----+-------------------....----+ | 61 | 21 | 00 | 00 (4 octets) | 16 octet GID | +-----+-----+-----+-----+-----+-----+-----+-------------------....----+ 2.2 Use of the BROADCAST flag A DHCP client on IPoIB MUST set the BROADCAST flag in DHCPDISCOVER and DHCPREQUEST messages (and set "ciaddr" to zero) to ensure that the server (or the relay agent) broadcasts its reply to the client. Note: As described in [RFC2131], "ciaddr" MUST be filled in with client's IP address during BOUND, RENEWING or REBINDING state, therefore, the BROADCAST flag MUST NOT be set. In these cases, the DHCP server unicasts DHCPACK message to the address in "ciaddr". The link address will be resolved by ARP. 3. Security Considerations RFC2131 describes the security considerations relevant to DHCP. This document does not introduce any new issues. 4. Acknowledgement This document borrows extensively from [RFC2855]. Roy Larsen pointed out the length discrepancy between the IPoIB link address and DHCP's "chaddr" field. 5. References 5.1 Normative [RFC2119] Key words for use in RFCs to Indicate Requirement Levels, S. Bradner [RFC2131] Dynamic Host Configuration Protocol, R. Droms [RFC2132] DHCP Options and BOOTP Vendor Extensions, S. Alexander, R. Droms [RFC1542] Clarifications and Extensions for the Bootstrap Protocol, Kashyap [Page 5]
INTERNET-DRAFT DHCP over InfiniBand November 2004 W. Wimer [RFC951] Bootstrap Protocol, B. Croft, J. Gilmore [IPoIB_ENCAP] draft-ietf-ipoib-ip-over-infiniband-07.txt, H.K. Jerry Chu, V. Kashyap [ARPPARAM] http://www.iana.org/numbers.html [IBARCH] InfiniBand Architecture Specification, www.infinibandta.org/specs [IPoIB_ARCH] draft-ietf-ipoib-architecture-04.txt, V. Kashyap 5.2 Informative [RFC2855] DHCP for IEEE 1394, K. Fujisawa 6. Author's Address Vivek Kashyap 15350, SW Koll Parkway Beaverton, OR 97006 USA 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. Intellectual Property Statement 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 Kashyap [Page 6]
INTERNET-DRAFT DHCP over InfiniBand November 2004 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. Acknowledgment Funding for the RFC Editor function is currently provided by the Internet Society. Kashyap [Page 7]
