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Stapp 3 Internet-Draft Cisco Systems, Inc. 4 Intended status: Standards Track December 18, 2008 5 Expires: June 21, 2009 7 The DHCPv4 Relay Agent Identifier Suboption 8 draft-ietf-dhc-relay-id-suboption-06.txt 10 Status of this Memo 12 This Internet-Draft is submitted to IETF in full conformance with the 13 provisions of BCP 78 and BCP 79. 15 Internet-Drafts are working documents of the Internet Engineering 16 Task Force (IETF), its areas, and its working groups. Note that 17 other groups may also distribute working documents as Internet- 18 Drafts. 20 Internet-Drafts are draft documents valid for a maximum of six months 21 and may be updated, replaced, or obsoleted by other documents at any 22 time. It is inappropriate to use Internet-Drafts as reference 23 material or to cite them other than as "work in progress." 25 The list of current Internet-Drafts can be accessed at 26 http://www.ietf.org/ietf/1id-abstracts.txt. 28 The list of Internet-Draft Shadow Directories can be accessed at 29 http://www.ietf.org/shadow.html. 31 This Internet-Draft will expire on June 21, 2009. 33 Copyright Notice 35 Copyright (c) 2008 IETF Trust and the persons identified as the 36 document authors. All rights reserved. 38 This document is subject to BCP 78 and the IETF Trust's Legal 39 Provisions Relating to IETF Documents 40 (http://trustee.ietf.org/license-info) in effect on the date of 41 publication of this document. Please review these documents 42 carefully, as they describe your rights and restrictions with respect 43 to this document. 45 Abstract 47 This memo defines a new Relay Agent Identifier suboption for the 48 Dynamic Host Configuration Protocol's (DHCP) Relay Agent Information 49 option. The suboption carries a value that uniquely identifies the 50 relay agent device. The value may be administratively-configured or 51 may be generated by the relay agent. The suboption allows a DHCP 52 relay agent to include the identifier in the DHCP messages it sends. 54 Table of Contents 56 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 57 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . . 3 58 3. Example Use-Cases . . . . . . . . . . . . . . . . . . . . . . . 3 59 3.1. Industrial Ethernet . . . . . . . . . . . . . . . . . . . . 3 60 3.2. Bulk Leasequery . . . . . . . . . . . . . . . . . . . . . . 4 61 4. Suboption Format . . . . . . . . . . . . . . . . . . . . . . . 4 62 5. Relay Identifier Types . . . . . . . . . . . . . . . . . . . . 5 63 6. Generating a Relay Identifier . . . . . . . . . . . . . . . . . 5 64 7. Identifier Stability . . . . . . . . . . . . . . . . . . . . . 5 65 8. Security Considerations . . . . . . . . . . . . . . . . . . . . 6 66 9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 6 67 10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 6 68 10.1. Normative References . . . . . . . . . . . . . . . . . . . 6 69 10.2. Informative References . . . . . . . . . . . . . . . . . . 7 70 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 7 72 1. Introduction 74 The Dynamic Host Configuration Protocol for IPv4 (DHCPv4) [RFC2131] 75 provides IP addresses and configuration information for IPv4 clients. 76 It includes a relay agent capability, in which network elements 77 receive broadcast messages from clients and forward them to DHCP 78 servers as unicast messages. In many network environments, relay 79 agents add information to the DHCP messages before forwarding them, 80 using the Relay Agent Information option [RFC3046]. Servers that 81 recognize the relay information option echo it back in their replies. 83 This specification introduces a Relay Agent Identifier suboption for 84 the Relay Information option. The Relay-Id suboption carries a 85 sequence of octets that is intended to identify the relay agent 86 uniquely within the administrative domain. The identifier may be 87 administratively configured: in some networks it may be adequate to 88 assign ASCII strings such as "switch1" and "switch2". Alternatively, 89 the identifier may be generated by the relay agent itself, and we 90 specify use of DUIDs [RFC3315] for this purpose. 92 2. Terminology 94 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 95 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 96 document are to be interpreted as described in [RFC2119]. 98 DHCPv4 terminology is defined in [RFC2131], and the DHCPv4 Relay 99 Agent Information Option in [RFC3046]. DUID terminology is in 100 [RFC3315]. 102 3. Example Use-Cases 104 3.1. Industrial Ethernet 106 DHCP typically identifies clients based on information in their DHCP 107 messages - such as the Client-Identifier option, or the value of the 108 chaddr field. In some networks, however, the location of a client - 109 its point of attachment to the network - is a more useful identifier. 110 In factory-floor networks (commonly called 'Industrial' networks), 111 for example, the role a device plays is often fixed and based on its 112 location. Using manual address configuration is possible (and is 113 common) but it would be beneficial if DHCP configuration could be 114 applied to these networks. 116 One way to provide connection-based identifiers for industrial 117 networks is to have the network elements acting as DHCP relay agents 118 supply information that a DHCP server could use as a client 119 identifier. A straightforward way to form identifier information is 120 to combine something that is unique within the scope of the network 121 element, such as a port/slot value, with something that uniquely 122 identifies that network element, such as a Relay Agent Identifier. 124 3.2. Bulk Leasequery 126 There has been quite a bit of recent interest in extending the DHCP 127 Leasequery protocol [RFC4388] to accommodate some additional 128 situations. There is a recent draft ([draft-kinnear]) proposing a 129 variety of enhancements to the existing Leasequery protocol. The 130 draft describes a use-case where a relay agent queries DHCP servers 131 using the Relay Identifier to retrieve all the leases allocated 132 through the relay device. 134 4. Suboption Format 136 Format of the Relay Agent Identifier suboption: 138 0 1 2 3 139 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 1 140 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 141 |SUBOPT_RELAY_ID| length | type | | 142 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | 143 . . 144 . identifier (variable) . 145 . . 146 +---------------------------------------------------------------+ 148 Where: 150 SUBOPT_RELAY_ID [TBA] 152 length the number of octets in the suboption 153 (excluding the suboption ID and length fields); 154 the minimum length is two. 156 type a single octet describing the type of 157 identifier that is present. 159 identifier the identifying data. 161 5. Relay Identifier Types 163 For clarity, the suboption specified here includes a type octet that 164 describes the data used in the identifier field. The type value zero 165 is reserved and MUST NOT be used. Two type values are defined here: 166 RELAY_IDENTIFIER_DUID and RELAY_IDENTIFIER_ASCII. 167 RELAY_IDENTIFIER_DUID is used when the identifier field contains a 168 DUID [RFC3315]. Administrators may want to assign human-friendly 169 ASCII identifiers: RELAY_IDENTIFIER_ASCII is used when the identifier 170 field contains an ASCII string. 172 6. Generating a Relay Identifier 174 As described in Section 1, in some situations it may be useful for 175 network devices to generate identifiers themselves. Relay agents who 176 send the Relay Agent Identifier suboption using identifiers that are 177 not administratively-configured MUST be generated following the 178 procedures in the DUID section of [RFC3315]. Relay agents who use 179 generated identifiers SHOULD make the generated value visible to 180 their administrators via their user interface, through a log entry, 181 or through some other mechanism. 183 7. Identifier Stability 185 If the relay identifier is to be meaningful it has to be stable. A 186 relay agent SHOULD use a single identifier type and value 187 consistently. The identifier used by a relay device SHOULD be 188 committed to stable storage, unless the relay device can regenerate 189 the value upon reboot. 191 Implementors should note that the identifier needs to be present in 192 all DHCP message types where its value is being used by the DHCP 193 server. The relay agent may not be able to add the Relay Agent 194 Information option to all messages - such as RENEW messages sent as 195 IP unicasts. In some deployments that might mean that the server has 196 to be willing to continue to associate the relay identifier it has 197 last seen with a lease that is being RENEWed. Other deployments may 198 prefer to use the Server Identifier Override suboption [RFC5107] to 199 permit the relay device to insert the Information option into all 200 relayed messages. 202 Handling situations where a relay agent device is replaced is another 203 aspect of "stability". One of the use-cases for the relay identifier 204 is to permit a server to associate clients' lease bindings with the 205 relay device connected to the clients. If the relay device is 206 replaced, because it has failed or been upgraded, it may be desirable 207 for the new device to continue to provide the same relay identifier 208 as the old device. Implementors should be aware of this possibility, 209 and consider making it possible for administrators to configure the 210 identifier. 212 8. Security Considerations 214 Security issues with the Relay Agent Information option and its use 215 by servers in address assignment are discussed in [RFC3046] and 216 [RFC4030]. Relay agents who send the Relay Agent Identifier 217 suboption SHOULD use the Relay Agent Authentication suboption 218 [RFC4030] to provide integrity protection. 220 9. IANA Considerations 222 We request that IANA assign a new suboption code from the registry of 223 DHCP Agent Sub-Option Codes maintained in 224 http://www.iana.org/assignments/bootp-dhcp-parameters. 226 Relay Agent Identifier Suboption [TBA] 228 We request that IANA establish a new registry of DHCP Relay Agent 229 Identifier Sub-Option Types, to be maintained in 230 http://www.iana.org/assignments/bootp-dhcp-parameters. The 231 Identifier Type is a single octet. The initial values assigned in 232 this document are: 234 Reserved 0 235 RELAY_IDENTIFIER_DUID 1 236 RELAY_IDENTIFIER_ASCII 2 238 Additional Identifier Type values will be allocated and assigned 239 through IETF Review, as defined in [RFC5226]. 241 10. References 243 10.1. Normative References 245 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 246 Requirement Levels", BCP 14, RFC 2119, March 1997. 248 [RFC2131] Droms, R., "Dynamic Host Configuration Protocol", 249 RFC 2131, March 1997. 251 [RFC3046] Patrick, M., "DHCP Relay Agent Information Option", 252 RFC 3046, January 2001. 254 [RFC3315] Droms, R., Bound, J., Volz, B., Lemon, T., Perkins, C., 255 and M. Carney, "Dynamic Host Configuration Protocol for 256 IPv6 (DHCPv6)", RFC 3315, July 2003. 258 [RFC4030] Stapp, M. and T. Lemon, "The Authentication Suboption for 259 the Dynamic Host Configuration Protocol (DHCP) Relay Agent 260 Option", RFC 4030, March 2005. 262 [RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an 263 IANA Considerations Section in RFCs", BCP 26, RFC 5226, 264 May 2008. 266 10.2. Informative References 268 [RFC4388] Woundy, R. and K. Kinnear, "Dynamic Host Configuration 269 Protocol (DHCP) Leasequery", RFC 4388, February 2006. 271 [RFC5107] Johnson, R., Kumarasamy, J., Kinnear, K., and M. Stapp, 272 "DHCP Server Identifier Override Suboption", RFC 5107, 273 February 2008. 275 [draft-kinnear] 276 Kinnear, K., Volz, B., Russell, N., and M. Stapp, "Bulk 277 DHCPv4 Lease Query 278 (draft-kinnear-dhc-dhcpv4-bulk-leasequery-*)", July 2008. 280 Author's Address 282 Mark Stapp 283 Cisco Systems, Inc. 284 1414 Massachusetts Ave. 285 Boxborough, MA 01719 286 USA 288 Phone: +1 978 936 0000 289 Email: mjs@cisco.com