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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(See RFCs 3967 and 4897 for information about using normative references to lower-maturity documents in RFCs) == Outdated reference: A later version (-15) exists of draft-ietf-svrloc-protocol-v2-11 ** Obsolete normative reference: RFC 2279 (ref. '4') (Obsoleted by RFC 3629) Summary: 10 errors (**), 0 flaws (~~), 3 warnings (==), 2 comments (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 1 Internet Engineering Task Force C. Perkins 2 INTERNET DRAFT E. Guttman 3 Sun Microsystems 4 16 December 1998 6 DHCP Options for Service Location Protocol 7 draft-ietf-dhc-slp-06.txt 9 Status of This Memo 11 This document is a submission by the Dynamic Host Configuration 12 Working Group of the Internet Engineering Task Force (IETF). 13 Comments should be submitted to the dhcp-v4@bucknell.edu mailing 14 list. 16 Distribution of this memo is unlimited. 18 This document is an Internet-Draft. Internet-Drafts are working 19 documents of the Internet Engineering Task Force (IETF), its areas, 20 and its working groups. Note that other groups may also distribute 21 working documents as Internet-Drafts. 23 Internet-Drafts are draft documents valid for a maximum of six months 24 and may be updated, replaced, or obsoleted by other documents at 25 any time. It is inappropriate to use Internet- Drafts as reference 26 material or to cite them other than as ``work in progress.'' 28 To view the entire list of current Internet-Drafts, please check 29 the ``1id-abstracts.txt'' listing contained in the Internet-Drafts 30 Shadow Directories on ftp.is.co.za (Africa), ftp.nordu.net (Northern 31 Europe), ftp.nis.garr.it (Southern Europe), munnari.oz.au (Pacific 32 Rim), ftp.ietf.org (US East Coast), or ftp.isi.edu (US West Coast). 34 Abstract 36 The Dynamic Host Configuration Protocol provides a framework for 37 passing configuration information to hosts on a TCP/IP network. 38 Entities using the Service Location Protocol need to find out the 39 address of Directory Agents in order to transact messages. Another 40 option provides an assignment of scope for configuration of SLP User 41 and Service Agents. 43 1. Introduction 45 The Dynamic Host Configuration Protocol [2] provides a framework 46 for passing configuration information to hosts on a TCP/IP network. 47 Entities using the Service Location Protocol, Version 2 [3] need to 48 obtain the address of Directory Agents and Scope configuration. The 49 Service Location Protocol (SLP) provides a default configuration 50 for Scopes and Directory Agents may be discovered using multicast 51 or broadcast. It is useful in a larger deployment to be able 52 to configure SLP Agents using DHCP, so as to centralize the 53 administration and to deploy SLP in networks where multicast routing 54 is not available. 56 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 57 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 58 document are to be interpreted as described in [1]. 60 2. Introduction 62 The DHCP options described below are used to configure Agents using 63 the Service Location Protocol, Version 2 [3]. 65 The SLP Directory Agent option is used to configure User Agents and 66 Service Agents with the location of Directory Agents in the network. 68 The SLP Scope Option takes precedence over both default and static 69 scope configuration of SLP agents. 71 3. SLP Directory Agent Option 73 This option specifies the location of one or more SLP Directory 74 Agents. 76 0 1 2 3 77 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 78 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 79 | Code = 78 | Length | a1 | a2 | 80 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 81 | a3 | a4 | a1 | ... 82 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 84 The SLP Directory Agent Option specifies a list of IP addresses 85 for Directory Agents. Directory Agents MUST be listed in order of 86 preference, if there is an order of preference. 88 The address of the Directory Agent is given in network byte order. 89 The length of the option MUST always be divisible by 4 and has a 90 minimum length of 4. 92 The Directory Agents listed in this option MUST be configured with 93 the a non-empty subset of the scope list that the Agent receiving the 94 Directory Agent Option is configured with. See the notes below. 96 The SLPv2 specification [3] defines how to use this option. 98 4. SLP Service Scope Option 100 The scope list is a comma delimited list which indicates the scopes 101 that a SLP Agent is configured to use. 103 0 1 2 3 104 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 1 105 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 106 | Code = 79 | Length | MANDATORY | ... 107 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 109 The Length indicates the number of bytes which follow. Since the 110 Scope-List String is encoded using UTF-8 [4] characters, it may be 111 the cast that the Length is not the same as the number of characters 112 in the Scope-List String. The Length value must include one for the 113 'MANDATORY' byte. 115 The 'MANDATORY' byte determines whether SLP Agents override their 116 static configuration for scopes with the string 117 provided by the option. This allows DHCP administrators to 118 implement a policy of assigning a set of scopes to Agents for service 119 provision. If the MANDATORY byte is zero, static configuration takes 120 precedence over the DHCP provided scope list. If the MANDATORY byte 121 is nonzero, the provided in this option MUST be used by 122 the SLP Agent. 124 The Scope List String syntax and usage are defined in the SLPv2 125 specification [3]. 127 4.1. Zero Length Scope-List String Configuration 129 A SLP Service Scope Option which indicates a Length of 1 (in other 130 words, omitting the string entirely) validly configures 131 the SLP User Agent to use "User Selectable Scopes." 132 The SLP Agent will use the aggregated list of scopes of all known 133 DAs. If no DAs are known, the UA will use SA discovery to determine 134 the list of scopes on the network, as defined in [3]. 136 Note that this configuration is tantamount to removing all 137 centralized control of the scope configuration of hosts on the 138 network. This makes it possible for every User Agent to see every 139 service. This may not be desirable as users may not be able to or 140 desire to decide which services are appropriate for them. 142 5. Security Considerations 144 If a malicious host is able to insert fraudulent information in 145 DHCPOFFER packets sent to a prospective SLP Agent then the SLP Agent 146 will be unable to obtain service, or may unwittingly be directed to 147 use the incorrect services. 149 Many opportunities for denial of service exist. A service agent 150 could find that it might rely on fraudulent or otherwise malicious 151 directory agents to advertise its services. DHCPOFFERs could prevent 152 the regular SLP framework from functioning by directing clients to 153 not use multicast, to use nonexistent directory agents and so on. 155 These difficulties are inherited from the much larger and more 156 serious problem, viz. securing or authenticating any information 157 whatsoever from a DHCP server (or client!) is not possible in common 158 DHCP deployments. 160 6. Full Copyright Statement 162 Copyright (C) The Internet Society (1997). All Rights Reserved. 164 This document and translations of it may be copied and furnished to 165 others, and derivative works that comment on or otherwise explain it 166 or assist in its implementation may be prepared, copied, published 167 and distributed, in whole or in part, without restriction of any 168 kind, provided that the above copyright notice and this paragraph 169 are included on all such copies and derivative works. However, 170 this document itself may not be modified in any way, such as by 171 removing the copyright notice or references to the Internet Society 172 or other Internet organizations, except as needed for the purpose 173 of developing Internet standards in which case the procedures 174 for copyrights defined in the Internet Standards process must be 175 followed, or as required to translate it into languages other than 176 English. 178 The limited permissions granted above are perpetual and will not be 179 revoked by the Internet Society or its successors or assigns. 181 This document and the information contained herein is provided on an 182 "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING 183 TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING 184 BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION 185 HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF 186 MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE." 188 References 190 [1] S. Bradner. Key words for use in RFCs to Indicate Requirement 191 Levels. RFC 2119, March 1997. 193 [2] R. Droms. Dynamic Host Configuration Protocol. RFC 2131, March 194 1997. 196 [3] E. Guttman, C. Perkins, J. Veizades, and M. Day. Service 197 Location Protocol version 2. draft-ietf-svrloc-protocol-v2-11.txt, 198 October 1998. (work in progress). 200 [4] F. Yergeau. UTF-8, a transformation format of unicode and ISO 201 10646. RFC 2279, October 1998. 203 Author's Address 205 Questions about this memo can be directed to: 207 Charles E. Perkins Erik Guttman 208 Technology Development Group Technology Development Group 209 Mail Stop MPK15-214 Mail Stop UFRA02 210 Sun Microsystems, Inc. Sun Microsystems, Inc. 211 15 Network Circle Bahnstr. 2 212 Menlo Park, CA 94025 74915 Waibstadt, Germany 213 phone: +1 650-786-6464 phone: +49 7263 911 701 214 fax: +1 650-786-6445 or: +1 650 786 5992 215 email: Charles.Perkins@Sun.Com Erik.Guttman@Sun.Com 216 Web: http://www.svrloc.org/~charliep