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Is this intentional? Checking references for intended status: Proposed Standard ---------------------------------------------------------------------------- (See RFCs 3967 and 4897 for information about using normative references to lower-maturity documents in RFCs) == Unused Reference: 'RFC4861' is defined on line 197, but no explicit reference was found in the text ** Obsolete normative reference: RFC 3315 (Obsoleted by RFC 8415) ** Obsolete normative reference: RFC 3633 (Obsoleted by RFC 8415) Summary: 2 errors (**), 0 flaws (~~), 2 warnings (==), 2 comments (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Network Working Group R. Droms 3 Internet-Draft Cisco Systems 4 Intended status: Standards Track January 17, 2012 5 Expires: July 20, 2012 7 Modification to Default Value of SOL_MAX_RT 8 draft-droms-dhc-dhcpv6-solmaxrt-update-02 10 Abstract 12 This document updates RFC 3315 by redefining the default value for 13 SOL_MAX_RT and defining an option through which a DHCPv6 server can 14 override the client's default value for SOL_MAX_RT with a new value. 16 Status of this Memo 18 This Internet-Draft is submitted in full conformance with the 19 provisions of BCP 78 and BCP 79. 21 Internet-Drafts are working documents of the Internet Engineering 22 Task Force (IETF). Note that other groups may also distribute 23 working documents as Internet-Drafts. The list of current Internet- 24 Drafts is at http://datatracker.ietf.org/drafts/current/. 26 Internet-Drafts are draft documents valid for a maximum of six months 27 and may be updated, replaced, or obsoleted by other documents at any 28 time. It is inappropriate to use Internet-Drafts as reference 29 material or to cite them other than as "work in progress." 31 This Internet-Draft will expire on July 20, 2012. 33 Copyright Notice 35 Copyright (c) 2012 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. Code Components extracted from this document must 44 include Simplified BSD License text as described in Section 4.e of 45 the Trust Legal Provisions and are provided without warranty as 46 described in the Simplified BSD License. 48 1. Introduction 50 Section 5.5 of the DHCPv6 specification [RFC3315] defines the default 51 value of SOL_MAX_RT to be 120 seconds. In some circumstances, this 52 default will lead to an unacceptably high volume of aggregated 53 traffic at a DHCPv6 server. 55 The change to SOL_MAX_RT is in response to DHCPv6 message rates 56 observed at a DHCPv6 server in a deployment in which many DHCPv6 57 clients are sending Solicit messages but the DHCPv6 server has been 58 configured not to respond to those Solicit messages. 60 1.1. Requirements Language 62 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 63 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 64 document are to be interpreted as described in RFC 2119 [RFC2119]. 66 2. Update to RFC 3315 68 This document changes section 5.5 of RFC 3315 [RFC3315] as follows: 70 OLD: 71 SOL_MAX_RT 120 secs Max Solicit timeout value 73 NEW: 74 SOL_MAX_RT 3600 secs Max Solicit timeout value 76 With this change, a DHCPv6 client that does not receive a 77 satisfactory response will send Solicit messages with the same 78 initial frequency and exponential backoff as specified in section 79 17.1.2 of RFC 3315 [RFC3315]. However, the long term behavior of 80 these DHCPv6 clients will be to send a Solicit message every 3600 81 seconds rather than every 120 seconds, significantly reducing the 82 aggregated traffic at the DHCPv6 server. 84 3. SOL_MAX_RT option 86 A DHCPv6 server sends the SOL_MAX_RT option to a client to override 87 the default value of SOL_MAX_RT. The value of SOL_MAX_RT in the 88 option replaces the default value defined in RFC 3315 [RFC3315]. One 89 use for the SOL_MAX_RT option is to set a longer value for 90 SOL_MAX_RT, which reduces the Solicit traffic from a client that has 91 not received a response to its Solicit messages. 93 The format of the SOL_MAX_RT option is: 95 0 1 2 3 96 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 97 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 98 | option-code | option-len | 99 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 100 | SOL_MAX_RT value | 101 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 103 option-code OPTION_SOL_MAX_RT (TBD). 105 option-len 4. 107 SOL_MAX_RT value Overriding value for SOL_MAX_RT in seconds. 109 Figure 1 111 A DHCPv6 client MUST include the SOL_MAX_RT option code in an Option 112 Request option [RFC3315] in any message it sends. 114 The DHCPv6 server MAY include the SOL_MAX_RT option in any response 115 it sends to a client that has included the SOL_MAX_RT option code in 116 an Option Request option. The SOL_MAX_RT option is sent in the main 117 body of the message to client, not as a sub-option in, e.g., an 118 IA_NA, IA_TA [RFC3315] or IA_PD [RFC3633] option. 120 If a DHCPv6 client receives a message containing a SOL_MAX_RT option, 121 the client MUST set its internal SOL_MAX_RT parameter to the value 122 contained in the SOL_MAX_RT option. As a result of receiving this 123 option, the DHCPv6 client MUST NOT send any Solicit messages more 124 frequently than allowed by the retransmission mechanism defined in 125 sections 17.1.2 and 14 of RFC 3315 [RFC3315]. 127 4. Updates to RFC 3315 129 RFC 3315 [RFC3315], section 17.1.3: 131 OLD: 133 The client MUST ignore any Advertise message that includes a Status 134 Code option containing the value NoAddrsAvail, with the exception 135 that the client MAY display the associated status message to the 136 user. 138 NEW: 140 The client MUST ignore any Advertise message that includes a Status 141 Code option containing the value NoAddrsAvail, with the exception 142 that the client MUST process an included SOL_MAX_RT option and MAY 143 display the associated status message to the user. 145 Figure 2 147 RFC 3315 [RFC3315], section 17.2.2: 149 OLD: 151 If the server will not assign any addresses to any IAs in a 152 subsequent Request from the client, the server MUST send an 153 Advertise message to the client that includes only a Status Code 154 option with code NoAddrsAvail and a status message for the user, a 155 Server Identifier option with the server's DUID, and a Client 156 Identifier option with the client's DUID. 158 NEW: 160 If the server will not assign any addresses to any IAs in a 161 subsequent Request from the client, the server MUST send an 162 Advertise message to the client that includes only a Status Code 163 option with code NoAddrsAvail and a status message for the user, a 164 Server Identifier option with the server's DUID, a Client 165 Identifier option with the client's DUID and (optionally) a 166 SOL_MAX_RT option. 168 Figure 3 170 5. Security Considerations 172 This document introduces one security consideration beyond those 173 described in RFC 3315 [RFC3315]. A malicious DHCPv6 server might 174 cause a client to set its SOL_MAX_RT parameter to an arbitrarily high 175 value with the SOL_MAX_RT option. Assuming the client also receives 176 a response from a valid DHCPv6 server, the large value for SOL_MAX_RT 177 will not have any effect. 179 6. IANA Considerations 181 IANA is requested to assign an option code from the "DHCP Option 182 Codes" Registry for OPTION_SOL_MAX_RT. 184 7. Normative References 186 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 187 Requirement Levels", BCP 14, RFC 2119, March 1997. 189 [RFC3315] Droms, R., Bound, J., Volz, B., Lemon, T., Perkins, C., 190 and M. Carney, "Dynamic Host Configuration Protocol for 191 IPv6 (DHCPv6)", RFC 3315, July 2003. 193 [RFC3633] Troan, O. and R. Droms, "IPv6 Prefix Options for Dynamic 194 Host Configuration Protocol (DHCP) version 6", RFC 3633, 195 December 2003. 197 [RFC4861] Narten, T., Nordmark, E., Simpson, W., and H. Soliman, 198 "Neighbor Discovery for IP version 6 (IPv6)", RFC 4861, 199 September 2007. 201 Author's Address 203 Ralph Droms 204 Cisco Systems 205 1414 Massachusetts Avenue 206 Boxborough, MA 01719 207 USA 209 Phone: +1 978 936 1674 210 Email: rdroms@cisco.com