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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: October 2002 April 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-bytes long. This is larger than the 16-bytes reserved for 42 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-bytes in length. The IPoIB link-layer 65 address is 20-bytes 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 i.e. 88 in situations where the client does not know its IP address. 90 RFC1542 notes that the use of a broadcast reply is discouraged 91 but in the case of IPoIB this is a necessity. There is no 92 option but to broadcast back to the client since it is not 93 possible to reply the client's unicast address. To 94 desynchronise broadcasts at subnet startup, the RFC2131 95 suggests that a client wait a random time (1 to 10 seconds) 96 before initiating server discovery. The same timeout will 97 equally spread out the DHCP server broadcast responses 98 generated due to the use of the use of the BROADCAST bit. 100 The client hardware address, 'chaddr', is unique in the subnet 101 and hence can be used to identify the client interface. But in 102 the absence of a unique chaddr the client-identifier must be 103 used. 105 The DHCP protocol states that the 'client identifier' option 106 may be used as the unique identifying value for the client. 107 This value must be unique within the subnet the client is a 108 member of. 110 The client identifier option includes a type and identifier 111 pair. The identifier included in the client-identifier option 112 may consist of a hardware address or any other unique value 113 such as the DNS name of the client. When a hardware address is 114 used, the type field should be one of the ARP hardware types 115 listed in [ARPPARAM]. A type of 0 (zero) should be used when 116 the included identifier is other than a hardware address. 117 [RFC2132] 119 The client-identifier itself SHOULD not be interpreted by the 120 server. [RFC2132] 122 2.1 IPoIB specific usage of DHCP message fields 124 A DHCP client, when working over an IPoIB interface, MUST 125 follow the following rules: 127 'htype' (hardware address type) MUST be 32 [ARPPARAM] 129 'hlen' (hardware address length) MUST be 0. 131 The 'chaddr' (client hardware address) field MUST be zeroed. 132 The server and the relay agent MUST ignore 'chaddr' on 133 receipt. 135 The 'client identifier' option MUST be used in DHCP messages. 136 'client identifier' option MAY consist of any data. 138 IPoIB clients SHOULD use the following format for the 139 client-identifier option: 141 Code Len Type Client-Identifier 142 +-----+-----+-----+-----+-----+-----+-----+-------------------....----+ 143 | 61 | 21 | 32 |Interface-id (4 bytes) | GID (16 bytes) | 144 +-----+-----+-----+-----+-----+-----+-----+-------------------....----+ 146 Every IPoIB interface is associated with an identifier 147 referred to as the GID [IPoIB_ARCH]. The GID is unique in the 148 InfiniBand fabric. An invariant GID is formed by appending the 149 port's EUI-64 identifier to the InfiniBand subnet prefix. 151 The GID is associated with a particular hardware port. The GID 152 and a QPN define an IPoIB interface at the port. Therefore an 153 implementation may associate multiple IPoIB interfaces on the 154 same port. It is up to the implementation to ensure a unique 155 client-identifier when multiple IPoIB interfaces are defined 156 over the same port and same GID. A unique, invariant 157 'interface-id' value be included in addition to the GID to 158 achieve this. 160 Note: a port may be associated with multiple GIDs. Therefore, 161 multiple IPoIB interfaces may exist on the same port while 162 using a different GID from among the GIDs associated with the 163 port. 165 A unique interface-id may be formed by including the QPN 166 associated with the relevant IPoIB interface if the 167 implementation is designed to keep this association constant 168 across boots. A timestamp or some other value unique to the 169 implementation may also be used for the same purpose. 171 If there is only one IPoIB interface associated with a 172 particular GID, then use of the GID with the 'interface-id' 173 zeroed is sufficient. By default, an implementation zeroes out 174 the interface-id field in the client identifier described 175 above. 177 This document does not preclude the use of other 'client 178 identifier' type, such as fully qualified domain name(FQDN) or 179 the EUI-64 value associated with the interface. 181 2.2 Use of the BROADCAST flag 183 A DHCP client on IPoIB SHOULD set a BROADCAST flag in 184 DHCPDISCOVER and DHCPREQUEST messages (and set 'ciaddr' to 185 zero) to ensure that the server (or the relay agent) 186 broadcasts its reply to the client. 188 Note: As described in [RFC2131], 'ciaddr' MUST be filled in 189 with client's IP address during BOUND, RENEWING or REBINDING 190 state, therefore, the BROADCAST flag MUST NOT be set. In these 191 cases, the DHCP server unicasts DHCPACK message to the address 192 in 'ciaddr'. The link address will be resolved by IPoIB ARP. 194 3. Security Considerations 196 DHCP currently provides no authentication or security 197 mechanisms. Potential exposures to attack are discussed 198 in section 7 of the DHCP protocol specification [RFC2131]. 200 A malicious client can falsify the client-identifier, 201 thus masquerading as another client. 203 4. Acknowledgement 205 This document borrows extensively from [RFC 2855]. Roy Larsen 206 pointed out the length discrepancy between the IPoIB link 207 address and DHCP's chaddr field. 209 References 211 [RFC2119] Key words for use in RFCs to Indicate Requirement Levels 212 S, Bradner 214 [RFC2131] Dynamic Host Configuration Protocol, R. Droms 216 [RFC2132] DHCP Options and BOOTP Vendor Extensions, 217 S. Alexander, R. Droms 219 [RFC951] Bootstrap Protocol, B. Croft, J. Gilmore 221 [RFC1542] Clarifications and Extensions for the Bootstrap Protocol 222 W. Wimer 224 [ARPPARAM] http://www.iana.org/numbers.html 226 [RFC2855] DHCP for IEEE 1394, K. Fujisawa 228 [IPoIB_ARCH] draft-ietf-ipoib-architecture-01.txt, V. Kashyap 230 [IPoIB_ENCAP] draft-ietf-ipoib-ip-over-infiniband-00.txt, 231 V. Kashyap, H.K. Jerry Chu 233 Author's Address 235 Vivek Kashyap 237 IBM 238 15450, SW Koll Parkway 239 Beaverton 240 OR 97006 242 Phone: +1 503 578 3422 243 EMail: vivk@us.ibm.com 245 Full Copyright Statement 247 Copyright (C) The Internet Society (2000). All Rights Reserved. 249 This document and translations of it may be copied and furnished to 250 others, and derivative works that comment on or otherwise explain it 251 or assist in its implementation may be prepared, copied, published 252 and distributed, in whole or in part, without restriction of any 253 kind, provided that the above copyright notice and this paragraph are 254 included on all such copies and derivative works. However, this 255 document itself may not be modified in any way, such as by removing 256 the copyright notice or references to the Internet Society or other 257 Internet organizations, except as needed for the purpose of 258 developing Internet standards in which case the procedures for 259 copyrights defined in the Internet Standards process must be 260 followed, or as required to translate it into languages other than 261 English. 263 The limited permissions granted above are perpetual and will not be 264 revoked by the Internet Society or its successors or assigns. 266 This document and the information contained herein is provided on an 267 "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING 268 TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING 269 BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION 270 HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF 271 MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.