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Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 INTERNET DRAFT Vivek Kashyap 3 IBM 4 Expiration Date: May 2003 November 2002 6 DHCP over InfiniBand 8 Status of this memo 10 This document is an Internet-Draft and is in full conformance 11 with all provisions of Section 10 of RFC 2026. 13 Internet-Drafts are working documents of the Internet 14 Engineering Task Force (IETF), its areas, and its working 15 groups. Note that other groups may also distribute working 16 documents as Internet- Drafts. 18 Internet-Drafts are draft documents valid for a maximum of six 19 months and may be updated, replaced, or obsoleted by other 20 documents at any time. It is inappropriate to use 21 Internet-Drafts as Reference material or to cite them other 22 than as ``work in progress''. 24 The list of current Internet-Drafts can be accessed at 25 http://www.ietf.org/ietf/1id-abstracts.txt 27 The list of Internet-Draft Shadow Directories can be accessed 28 at http://www.ietf.org/shadow.html 30 This memo provides information for the Internet community. 31 This memo does not specify an Internet standard of any kind. 32 Distribution of this memo is unlimited. 34 Copyright Notice 36 Copyright (C) The Internet Society (2001). All Rights Reserved. 38 Abstract 40 An InfiniBand network uses a link-layer addressing scheme that 41 is 20-octets long. This is larger than the 16-octets reserved 42 for the hardware address in DHCP/BOOTP message. The above 43 inequality imposes restrictions on the use of the DHCP message 44 fields when used over an IP over InfiniBand(IPoIB) network. 45 This document describes the use of DHCP message fields when 46 implementing DHCP over IPoIB. 48 1. Introduction 50 The Dynamic Host Configuration Protocol(DHCP) provides a 51 framework for passing configuration information to hosts on a 52 TCP/IP network [RFC2131]. DHCP is based on the Bootstrap 53 Protocol (BOOTP) [RFC951] adding the capability of automatic 54 allocation of reusable network addresses and additional 55 configuration options [RFC2131,RFC2132]. 57 The DHCP server receives a broadcast request from the DHCP 58 client. The DHCP server uses the client interface's 59 hardware-address to unicast a reply back when the client 60 doesn't yet have an IP address assigned to it. The 'chaddr' 61 field in the DHCP message carries the client's hardware 62 address. 64 The 'chaddr' field is 16-octets in length. The IPoIB link-layer 65 address is 20-octets in length. Therefore the IPoIB link-layer 66 address will not fit in the 'chaddr' field making it 67 impossible for the DHCP server to unicast a reply back to the 68 client. 70 To ensure interoperability the usage of the fields and the 71 method for DHCP interaction must be clarified. This document 72 describes the IPoIB specific usage of some fields of DHCP. See 73 [RFC2131] for the mechanism of DHCP and the explanations of 74 each field. 76 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL 77 NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and 78 "OPTIONAL" in this document are to be interpreted as described 79 in RFC 2119 [RFC2119]. 81 2. The DHCP over IPoIB mechanism 83 As noted above, because of the link-layer address length being 84 larger than the 'chaddr' field length, the link-layer address 85 is unavailable to the DHCP server. Therefore, a DHCP client 86 MUST request that the server sends a broadcast reply by 87 setting the BROADCAST flag when IPoIB ARP is not possible, 88 i.e. in situations where the client does not know its IP 89 address. 91 RFC1542 notes that the use of a broadcast reply is 92 discouraged. But in the case of IPoIB this is a necessity. 93 There is no option but to broadcast back to the client since 94 it is not possible to reply the client's unicast address. To 95 desynchronise broadcasts at subnet startup, RFC2131 suggests 96 that a client wait a random time (1 to 10 seconds) before 97 initiating server discovery. The same timeout will equally 98 spread out the DHCP server broadcast responses generated due 99 to the use of the use of the BROADCAST bit. 101 The client hardware address, 'chaddr', is unique in the subnet 102 and hence can be used to identify the client interface. But in 103 the absence of a unique chaddr the client-identifier must be 104 used. 106 The DHCP protocol states that the 'client identifier' option 107 may be used as the unique identifying value for the client. 108 This value must be unique within the subnet the client is a 109 member of. 111 The client identifier option includes a type and identifier 112 pair. The identifier included in the client-identifier option 113 may consist of a hardware address or any other unique value 114 such as the DNS name of the client. When a hardware address is 115 used, the type field should be one of the ARP hardware types 116 listed in [ARPPARAM]. 118 2.1 IPoIB specific usage of DHCP message fields 120 A DHCP client, when working over an IPoIB interface, MUST 121 follow the following rules: 123 'htype' (hardware address type) MUST be 32 [ARPPARAM] 125 'hlen' (hardware address length) MUST be 0. 127 'chaddr' (client hardware address) field MUST be zeroed. 129 'client identifier' option MUST be used in DHCP messages. 131 According to RFC2132 the 'client identifier' option MAY 132 consist of any data, but IPoIB clients SHOULD use the 133 following format for the client-identifier option: 135 Code Len Type Client-Identifier 136 +-----+-----+-----+-----+-----+-----+-----+-------------------....----+ 137 | 61 | 21 | 32 | Unique-value(4 octets) | GID (16 octets) | 138 +-----+-----+-----+-----+-----+-----+-----+-------------------....----+ 140 Every IPoIB interface is associated with an identifier 141 referred to as the GID [IPoIB_ARCH]. The GID is unique in the 142 InfiniBand fabric. An invariant GID is formed by appending the 143 port's EUI-64 identifier to the InfiniBand subnet prefix. 145 The GID is associated with a particular hardware port. The GID 146 and a QPN define an IPoIB interface at the port[IPOIB_ENCAP]. 147 Therefore an implementation could associate multiple IPoIB 148 interfaces on the same port by utilising a common GID but 149 different QPNs. It is up to the implementation to ensure a 150 unique client-identifier when multiple IPoIB interfaces are 151 defined over the same port and same GID. A unique, invariant 152 value MUST be included in addition to the GID to achieve 153 this. 155 Note: a port may be associated with multiple GIDs. Therefore, 156 multiple IPoIB interfaces may exist on the same port while 157 using a different GID from among the GIDs associated with the 158 port. 160 A unique client-identifier may be formed by including the QPN 161 associated with the relevant IPoIB interface if the 162 implementation is designed to keep this association constant 163 across boots. Some other value unique to the implementation 164 may also be used for the same purpose. If there is only one 165 IPoIB interface associated with a particular GID, then use of 166 the GID is sufficient. 168 This document does not preclude the use of other 'client 169 identifier' type, such as fully qualified domain name(FQDN) or 170 the EUI-64 value associated with the interface. 172 2.2 Use of the BROADCAST flag 174 A DHCP client on IPoIB MUST set a BROADCAST flag in 175 DHCPDISCOVER and DHCPREQUEST messages (and set 'ciaddr' to 176 zero) to ensure that the server (or the relay agent) 177 broadcasts its reply to the client. 179 Note: As described in [RFC2131], 'ciaddr' MUST be filled in 180 with client's IP address during BOUND, RENEWING or REBINDING 181 state, therefore, the BROADCAST flag MUST NOT be set. In these 182 cases, the DHCP server unicasts DHCPACK message to the address 183 in 'ciaddr'. The link address will be resolved by IPoIB ARP. 185 3. Security Considerations 187 RFC2131 describes the security considerations relevant to 188 DHCP. This document does not introduce any new issues. 190 4. Acknowledgement 192 This document borrows extensively from [RFC 2855]. Roy Larsen 193 pointed out the length discrepancy between the IPoIB link 194 address and DHCP's chaddr field. 196 References 198 [RFC2119] Key words for use in RFCs to Indicate 199 Requirement Levels S. Bradner 201 [RFC2131] Dynamic Host Configuration Protocol, R. Droms 203 [RFC2132] DHCP Options and BOOTP Vendor Extensions, 204 S. Alexander, R. Droms 206 [RFC951] Bootstrap Protocol, B. Croft, J. Gilmore 208 [RFC1542] Clarifications and Extensions for the 209 Bootstrap Protocol W. Wimer 211 [ARPPARAM] http://www.iana.org/numbers.html 213 [RFC2855] DHCP for IEEE 1394, K. Fujisawa 215 [IPoIB_ARCH] draft-ietf-ipoib-architecture-01.txt, V. Kashyap 217 [IPoIB_ENCAP] draft-ietf-ipoib-ip-over-infiniband-01.txt, 218 V. Kashyap, H.K. Jerry Chu 220 Author's Address 222 Vivek Kashyap 224 IBM 225 15450, SW Koll Parkway 226 Beaverton 227 OR 97006 229 Phone: +1 503 578 3422 230 EMail: vivk@us.ibm.com 232 Full Copyright Statement 234 Copyright (C) The Internet Society (2000). All Rights Reserved. 236 This document and translations of it may be copied and 237 furnished to others, and derivative works that comment on or 238 otherwise explain it or assist in its implementation may be 239 prepared, copied, published and distributed, in whole or in 240 part, without restriction of any kind, provided that the above 241 copyright notice and this paragraph are included on all such 242 copies and derivative works. However, this document itself may 243 not be modified in any way, such as by removing the copyright 244 notice or references to the Internet Society or other Internet 245 organizations, except as needed for the purpose of developing 246 Internet standards in which case the procedures for copyrights 247 defined in the Internet Standards process must be followed, or 248 as required to translate it into languages other than 249 English. 251 The limited permissions granted above are perpetual and will 252 not be revoked by the Internet Society or its successors or 253 assigns. 255 This document and the information contained herein is provided 256 on an "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET 257 ENGINEERING TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR 258 IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE 259 USE OF THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR 260 ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A 261 PARTICULAR PURPOSE. 263 __ 265 Vivek Kashyap 266 Linux Technology Center, IBM