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Checking references for intended status: Proposed Standard ---------------------------------------------------------------------------- (See RFCs 3967 and 4897 for information about using normative references to lower-maturity documents in RFCs) No issues found here. Summary: 3 errors (**), 0 flaws (~~), 4 warnings (==), 2 comments (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 1 Network Working Group A.K. Vijayabhaskar 2 Internet-Draft B. Senthil Kumar 3 Expires: May 12, 2004 Hewlett-Packard 4 11 Nov 2003 6 The Extended Remote Boot Option for DHCPv4 7 draft-vijay-dhc-opt-extrboot-00.txt 9 Status of this Memo 11 This document is an Internet-Draft and is in full conformance with 12 all provisions of Section 10 of RFC2026. 14 Internet-Drafts are working documents of the Internet Engineering 15 Task Force (IETF), its areas, and its working groups. Note that 16 other groups may also distribute working documents as Internet- 17 Drafts. 19 Internet-Drafts are draft documents valid for a maximum of six months 20 and may be updated, replaced, or obsoleted by other documents at any 21 time. It is inappropriate to use Internet-Drafts as reference 22 material or to cite them other 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 at 28 http://www.ietf.org/shadow.html. 30 This Internet-Draft will expire on May 12, 2004. 32 Copyright Notice 34 Copyright (C) The Internet Society (2003). All Rights Reserved. 36 Abstract 38 Single TFTP [2] server for huge number of diskless clients is prone 39 to single point of failure. So, Multiple TFTP servers are needed for 40 high availability. Moreover, some of the clients need multiple 41 bootfiles for boot up. This document provides a new DHCPv4 option 42 for clients to obtain information about multiple TFTP [2] servers and 43 bootfiles. 45 1. Introduction 47 DHCPv4 (Dynamic Host Configuration Protocol Version for IPv4) 48 provides a framework for passing configuration information to hosts 49 on an IPv4 network. However, DHCPv4 does not provide a way to send 50 more than one TFTP server address and bootfile names. This document 51 defines a new option to provide more than one TFTP server and 52 bootfile names. This option is required for clients, which are 53 booting over a network and require more than one file to be 54 downloaded and executed. The multiple TFTP servers are needed for 55 high availability. Network booting is widely used mechanism for 56 booting up of the clients, because of their advantages; softwares 57 will be in central server and requires maintenance at only one 58 location rather than maintaining individual systems separately. 59 Also, switching between different operating systems becomes easy when 60 network booting is being used. The additional boot files may be used 61 as supporting software for the boot image. Different Operating 62 System vendors use different way of handling this. 64 2. Requirements 66 The keywords MUST, MUST NOT, REQUIRED, SHALL, SHALL NOT, SHOULD, 67 SHOULD NOT, RECOMMENDED, MAY, and OPTIONAL, when they appear in this 68 document, are to be interpreted as described in RFC 2119 [7] 70 3. Terminology 72 This document uses terminology specific to DHCPv4 as defined in 73 "Terminology" section of the DHCPv4 specification [1]. 75 4. Extended Remote Boot Option 77 The Extended Remote Boot Option is used to carry the parameters 78 needed for remote boot of the DHCPv4 [1] clients. Using the 79 information provided by this option, the clients will be able to 80 bootp up. 82 The format of the Remote Boot Option is as shown below: 84 Code Len Extended Remote Boot Information Field 85 +-------+------+------+------+------+------+--...-+------+ 86 | TBD | N | r1 | r2 | r3 | r4 | | rN | 87 +-------+------+------+------+------+------+--...-+------+ 89 The length N gives the total number of octets in the Extended Remote 90 Boot Information Field. The length N should be at least 4 bytes. 92 r1, r2 .. rN are Remote Boot Information suboptions which contain 93 information needed for boot up of the clients. They should be 94 listed in the increasing order of preferences. 96 The Remote Boot Information suboption is explained in the Section 5. 98 5. Remote Boot Information suboption 100 The DHCP server uses the Remote Boot Information suboption to convey the 101 client about the TFTP Server [3] names and list of boot files needed for 102 booting of the clients. The clients are supposed to contact the TFTP 103 Server, obtain the boot files one by one and boot up using these files. 105 The format of the Remote Boot Information suboption is as shown below: 107 Code Len Remote Boot Information Field 108 +-------+------+------+------+------+------+--...-+------+ 109 | 1 | N | ts | f1 | f2 | f3 | | fN | 110 +-------+------+------+------+------+------+--...-+------+ 112 The length N gives the total number of octets in the Remote 113 Boot Information Field. The length N should be at least 2 bytes. 115 'ts' field consists of either TFTP server name (option 66) [4] 116 or the TFTP Server Address suboption suboption represented in the 117 Opt/Length/Value tuples. The format of the TFTP Server Address 118 suboption is given below: 120 Code Len TFTP Server address 121 +-----+-----+-----+-----+-----+-----+ 122 | 1 | n | a1 | a2 | a3 | a4 | 123 +-----+-----+-----+-----+-----+-----+ 125 The TFTP Server Address suboption gives IPv4 address of the one of 126 the TFTP Server available for the client. a1, a2, a3 and a4 refer 127 the quadrants of the IPv4 address of TFTP Server address in the 128 network byte order. The length of the option will be 4 octets. 130 f1, f2 ... fN are sequence of Bootfile name (option 67) [4] 131 represented in the Opt/Length/Value tuples. 133 If Bootfile name option is not following the TFTP Server name/address 134 suboption, then, bootfiles corresponding to the TFTP server specified 135 in the 'ts' field defaults to the boot file names from the previous 136 Remote Boot Information suboption which has non empty 'fn' fields. 138 Thus, TFTP server name/address and Bootfile name are sent as 139 suboption to Remote Boot Information option here. 141 If multiple boot files are provided by the server, then, they should 142 appear in the order of their execution in the client. The first 143 appearing Bootfile name should be downloaded and executed first for 144 boot up, then the next and so on. 146 6. Precedence of the options 148 This specification recommends the following precedence for the 149 various remote boot options, including the ones specified in [4]. 151 Option name/Field name Precedence 152 ---------------------- ---------- 153 Extended Remote Boot Option Highest 154 options 66 and 67 [4] Medium 155 'sname' and 'fname' [1] Lowest 157 Thus, if Extended Remote Boot Option is received by the client and 158 'sname' and 'file' fields are not overloaded, the client MUST ignore 159 the 'sname' and 'file' fields. If TFTP server name/address and/or 160 Bootfile name are received in the reply the server, along with the 161 Extended Remote Boot Option, then, the client MUST ignore TFTP server 162 name/address and/or Bootfile name options. 164 7. Server behavior 166 If the server receives the request for TFTP server name and/or 167 Bootfile name along with the Extended Remote Boot Option, the server 168 SHOULD ignore the TFTP server name and/or Bootfile name option and 169 reply back with Extended Remote Boot Option. 171 When the DHCP server is replying back with Extended Remote Boot 172 Option, the 'sname' and 'file' field SHOULD be used to overload the 173 options. 175 If the length of any of these options exceed the maximum permissible 176 within a single option (254 octets), then they MUST be represented in 177 the DHCP message as specified in [2]. 179 8. Client behavior 181 The client MUST NOT request for TFTP server name and/or Bootfile name 182 along with the Extended Remote Boot Option. 184 9. Security Considerations 186 The Remote Boot Option may be used by an intruder DHCPv4 server to 187 provide to cause DHCPv4 clients to contact rogue TFTP server (or) to 188 send invalid file names. This will make booting up of DHCP clients 189 to fail. 191 To avoid attacks through this option, the DHCP client SHOULD use 192 authentication mechanism for DHCP [5]. 194 10. IANA Considerations 196 IANA is requested to assign an option code to the following options 197 from the option-code space defined for public DHCP Options in 198 RFC 2939 [6]. 200 Option Name Value Described in 201 Extended Remote Boot Option tbd Section 4 203 11. Normative References 205 [1] Droms, R., "Dynamic Host Configuration Protocol", RFC 2131, March 206 1997. 208 [2] T. Lemon, S. Cheshire, Encoding Long Options in the Dynamic Host 209 Configuration Protocol (DHCPv4), RFC 3396, November 2002. 211 12. Informative References 213 [3] K. Sollins, The TFTP Protocol (Revision 2), RFC 1350, July 1992. 215 [4] Alexander, S. and R. Droms, "DHCP options and BOOTP Vendor 216 Extensions", RFC 2132, March 1997. 218 [5] Droms, R. and W. Arbaugh, "Authentication for DHCP Messages", 219 RFC 3118, June 2001. 221 [6] R. Droms, Procedures and IANA Guidelines for Definition of New 222 DHCP Options and Message Types, RFC 2939, September 2000. 224 [7] Bradner, S., "Key words for use in RFCs to Indicate Requirement 225 Levels", BCP 14, RFC 2119, March 1997. 227 Author's Address 229 Vijayabhaskar A K 230 Hewlett-Packard STSD-I 231 29, Cunningham Road 232 Bangalore - 560052 233 India 235 Phone: +91-80-2053085 236 E-Mail: vijayak@india.hp.com 238 Senthil Kumar B 239 Hewlett-Packard STSD-I 240 29, Cunningham Road 241 Bangalore - 560052 242 India 244 Phone: +91-80-2053103 245 E-Mail: ksenthil@india.hp.com 247 Full Copyright Statement 249 Copyright (C) The Internet Society (2003). 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