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Plonka 3 Internet-Draft University of Wisconsin 4 Expires: December 7, 2004 June 8, 2004 6 Embedding Globally Routable Internet Addresses Considered Harmful 7 draft-ietf-grow-embed-addr-03 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 17 Internet-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 December 7, 2004. 32 Copyright Notice 34 Copyright (C) The Internet Society (2004). All Rights Reserved. 36 Abstract 38 This document means to clarify best current practices in the Internet 39 community. Internet hosts should not contain globally routable 40 Internet Protocol addresses embedded within firmware or elsewhere as 41 part of their default configuration such that it influences run-time 42 behavior. 44 Revision History 46 RFC-EDITOR: PLEASE REMOVE REVISION HISTORY BEFORE PUBLICATION. The 47 following is the revision history of this document 49 $Log: draft-ietf-grow-embed-addr.xml,v $ 50 Revision 1.17 2004/06/08 20:27:02 plonka 51 minor edits 53 renamed from "-02" to "-03" 55 Revision 1.16 2004/06/08 20:15:03 plonka 56 minor edits, fixed some typos 58 Revision 1.15 2004/06/08 14:16:45 plonka 59 revised conclusion based on input from Geoff Huston 61 added netgear-sntp technical report to list of informative references 63 Revision 1.14 2004/06/07 18:16:27 plonka 64 split references into normative and informative sections 66 Revision 1.13 2004/06/07 16:32:10 plonka 67 Set category to BCP. 69 Rewrote/resized abstract and introduction as suggested by Pekka Savola. 71 Improved section about using DNS names, re; hard-coding caveats, as 72 suggested by Pekka Savola. 74 Encouraged use of IPv4 documentation/example prefix 192.0.2.0/24 rather 75 than private addresses, as noted by Pekka Savola. 77 Mentioned IPv6 2001:DB8::/32 documentation prefix, as noted by Tom Petch. 79 Added note for RFC-editor requesting that revision history be removed. 81 Reworded various portions. 83 Renamed from "-00" to "-01" and updated date. 85 Revision 1.12 2003/12/05 15:51:23 plonka 86 typo fixes and updates from Michael Patton 88 Revision 1.11 2003/12/02 22:28:04 plonka 89 renamed from draft-plonka-embed-addr to draft-ietf-grow-embed-addr 91 integrated suggestions from Paul Barford 92 reordered references to match the text 94 added quote from RFC2101 re: use of IPv4 addresses as identifiers 95 as mentioned by Brian Carpenter 97 Revision 1.10 2003/11/03 17:06:54 plonka 98 added background information in appendix 100 Revision 1.9 2003/11/03 16:39:30 plonka 101 various updates based on input from Mike O'Connor: 102 - indicated that DNS server(s) should be configurable 103 - clarified DNS round-robin behavior 104 - clarified "unsolicited traffic" by saying "IP traffic" 106 added revision history and appendix A 108 Figure 1 110 1. Introduction 112 Vendors of consumer electronics and network gear have produced and 113 sold hundreds of thousands of Internet hosts with globally routable 114 Internet Protocol addresses embedded within their products' firmware. 115 These products are now in operation world-wide and primarily include, 116 but are not necessarily limited to, low-cost routers and middleboxes 117 for personal or residential use. 119 This "hard-coding" of globally routable IP addresses as identifiers 120 within the host's firmware presents significant problems to the 121 operation of the Internet and to the management of its address space. 123 Ostensibly, this practice arose as an attempt to simplify 124 configuration of IP hosts by preloading them with IP addresses as 125 service identifiers. Products that rely on such embedded IP 126 addresses initially may appear convenient to both the product's 127 designer and its operator or user, but this dubious benefit comes at 128 the expense of others in the Internet community. 130 This document denounces the practice of embedding references to 131 unique, globally routable IP addresses in Internet hosts, describes 132 some of the resulting problems, and considers selected alternatives. 133 It also reminds the Internet community of the ephemeral nature of 134 unique, globally routable IP addresses and that the assignment and 135 use of IP addresses as identifiers is temporary and therefore should 136 not be used in fixed configurations. 138 2. Problems 140 In a number cases, the embedding of IP addresses has caused Internet 141 products to rely on a single central Internet service. This can 142 result in a service outage when the aggregate workload overwhelms 143 that service. When fixed addresses are embedded in an 144 ever-increasing number of client IP hosts, this practice runs 145 directly counter to the design intent of hierarchically deployed 146 services that would otherwise be robust solutions. 148 The reliability, scalability, and performance of many Internet 149 services require that the pool of users not directly access a service 150 by IP address. Instead they typically rely on a level of indirection 151 provided by the Domain Name System, RFC 2219 [6]. DNS permits the 152 service operator to reconfigure the resources for maintenance and to 153 load-balance without the participation of the users. For instance, 154 one common load-balancing technique employs multiple DNS records with 155 the same name that are then rotated in a round-robin fashion in the 156 set of answers returned by many DNS server implementations. Upon 157 receiving such a response to a query, resolvers typically will try 158 the answers in order, until one succeeds, thus enabling the operator 159 to distribute the user request load across a set of servers with 160 discrete IP addresses that generally remain unknown to the user. 162 Embedding globally unique IP addresses taints the IP address blocks 163 in which they reside, lessening the usefulness and portability of 164 those IP address blocks and increasing the cost of operation. 165 Unsolicited traffic may continue to be delivered to the embedded 166 address well after the IP address or block has been reassigned and no 167 longer hosts the service for which that traffic was intended. Circa 168 1997, the authors of RFC 2101 [5] made this observation: 169 Due to dynamic address allocation and increasingly frequent 170 network renumbering, temporal uniqueness of IPv4 addresses is no 171 longer globally guaranteed, which puts their use as identifiers 172 into severe question. 173 When IP addresses are used as service identifiers in the 174 configuration of many Internet hosts, the IP address blocks become 175 encumbered by their historical use. This may interfere with the 176 ability of the Internet Assigned Numbers Authority (IANA) and the 177 Internet Registry (IR) hierarchy to usefully reallocate IP address 178 blocks. Likewise, to facilitate IP address reuse, RFC 2050 [1], 179 encourages Internet Service Providers (ISPs) to treat address 180 assignments as "loans". 182 Because consumers are not necessarily experienced in the operation of 183 Internet hosts, they are not able to be relied upon to fix problems 184 if and when they arise. As such, a significant responsibility lies 185 with the manufacturer or vendor of the Internet host to avoid 186 embedding IP addresses in ways which cause the aforementioned 187 problems. 189 3. Recommendations 191 Internet host and router designers, including network product 192 manufacturers, should not assume that their products will be deployed 193 and used in only a single global Internet that they happen to observe 194 today. A myriad of private or future internets in which these 195 products will be used may not allow those hosts to establish 196 end-to-end communications with arbitrary hosts on the global 197 Internet. Since the product failure modes resulting from unknown 198 future states cannot be fully explored, one should avoid assumptions 199 regarding the longevity of our current Internet. 201 Vendors should, by default, disable unnecessary features in their 202 products. This is especially true of features that generate 203 unsolicited IP traffic. In this way these hosts will be conservative 204 regarding the unsolicited Internet traffic they produce. For 205 instance, one of the most common uses of embedded IP addresses has 206 been the hard-coding of addresses of well know public Simple Network 207 Time Protocol (SNTP RFC 2030 [7]) servers, even though only a small 208 fraction of the users benefits from these products even having some 209 notion of the current date and time. 211 Vendors should provide an operator interface for every feature that 212 generates unsolicited IP traffic. A prime example of this is that 213 the Domain Name System resolver should have an interface enabling the 214 operator to either explicitly set the servers of his choosing or to 215 enable the use of a standard automated configuration protocol such as 216 DHCP, defined by RFC 2132 [8]. Within the operator interface, these 217 features should originally be disabled so that one consequence of 218 subsequently enabling these features is that the operator becomes 219 aware that the feature exists. This will mean that it is more likely 220 that the product's owner or operator can participate in problem 221 determination and mitigation when problems arise. 223 Internet hosts should use the Domain Name System to determine the IP 224 addresses associated with the Internet services they require. 225 However, simply hard-coding DNS names rather than IP addresses is not 226 a panacea. Entries in the domain name space are also ephemeral and 227 can change owners for various reasons including acquisitions and 228 litigation. A given vendor ought not assume that anyone will retain 229 control of a given zone indefinitely. RFC 2606 [2] defines the 230 IANA-reserved "example.com", "example.net", and "example.org" domains 231 for use in example configurations and documentation. 233 Default configurations, documentation, and example configurations for 234 Internet hosts should use Internet addresses that reside within 235 special blocks that have been reserved for these purposes, rather 236 than unique, globally routable IP addresses. For IPv4, RFC 3330 [3] 237 states that the 192.0.2.0/24 block has been assigned for use in 238 documentation and example code. The IPv6 global unicast address 239 prefix 2001:DB8::/32 has been similarly reserved for documentation 240 purposes. Private Internet Addresses, as defined by RFC 1918 [4], 241 should not be used for such purposes. 243 Service providers and enterprise network operators should advertise 244 the identities of suitable local services, such as NTP. For 245 instance, the DHCP protocol, as defined by RFC 2132 [8], enables one 246 to configure a server to answer queries for service identitifiers to 247 clients that ask for them. When local services including NTP are 248 available but not pervasively advertised using such common protocols, 249 designers are more likely deploy ad hoc initialization mechanisms 250 that unnecessarily rely on central services. 252 Operators that provide public services on the global Internet, such 253 as the NTP community, should deprecate the explicit advertisement of 254 the IP addresses of public services. These addresses are ephemeral. 255 As such, their widespread citation in public service indexes 256 interferes with the ability to reconfigure the service as necessary 257 to address unexpected, increased traffic. 259 4. Security Considerations 261 Embedding or "hard-coding" IP addresses within a host's configuration 262 often means that a host-based trust model is being employed, and that 263 the Internet host with the given address is trusted in some way. Due 264 to the ephemeral roles of routable IP addresses, the practice of 265 embedding them within products' firmware or default configurations 266 presents a security risk in that unknown parties may inadvertently be 267 trusted. 269 Internet host designers may be tempted to implement some sort of 270 remote control mechanism within a product, by which its Internet host 271 configuration can be changed without reliance on, interaction with, 272 or even the knowledge of its operator or user. This raises security 273 issues of its own. If such a scheme is implemented, this should be 274 fully disclosed to the customer, operator, and user so that an 275 informed decision can be made, perhaps in accordance with local 276 security or privacy policy. Furthermore, the significant possibility 277 of malicious parties exploiting such a remote control mechanism may 278 completely negate any potential benefit of the remote control scheme. 280 5. IANA Considerations 282 This document creates no new requirements on IANA namespaces. 284 6. Conclusion 286 When large numbers of homogenous Internet hosts are deployed, it is 287 particularly important that both their designers and other members of 288 the Internet community diligently assess host implementation quality 289 and reconfigurability. 291 Implementors of host services should avoid any kind of use of unique 292 globally routable IP addresses within a fixed configuration part of 293 the service implementation. If there is a requirement for 294 pre-configured state then care should be taken to use an appropriate 295 service identifier and use standard resolution mechanisms to 296 dynamically resolve the identifier into an IP address. Also, any 297 such identifiers should be alterable in the field through a 298 conventional command and control interface for the service. 300 7. Acknowledgements 302 The author thanks the following reviewers for their contributions to 303 this document: Paul Barford, Geoff Huston, David Meyer, Mike 304 O'Connor, Michael Patton, Tom Petch, and Pekka Savola. 306 8. References 308 8.1 Normative References 310 [1] Hubbard, K., "INTERNET REGISTRY IP ALLOCATION GUIDELINES", RFC 311 2050, BCP 12, November 1996. 313 [2] Eastlake, D., "Reserved Top Level DNS Names", RFC 2606, BCP 32, 314 June 1999. 316 [3] Internet Assigned Numbers Authority, "Special-Use IPv4 317 Addresses", RFC 3330, September 2002. 319 [4] Rekhter, Y., "Address Allocation for Private Internets", RFC 320 1918, BCP 5, February 1996. 322 8.2 Informative References 324 [5] Carpenter, B., "IPv4 Address Behaviour Today", RFC 2101, 325 February 1997. 327 [6] Hamilton, M., "Use of DNS Aliases for Network Services", RFC 328 2219, BCP 17, October 1997. 330 [7] Mills, D., "Simple Network Time Protocol (SNTP) Version 4 for 331 IPv4, IPv6 and OSI", RFC 2030, October 1996. 333 [8] Alexander, S., "DHCP Options and BOOTP Vendor Extensions", RFC 334 2132, March 1997. 336 [9] Plonka, D., "Flawed Routers Flood University of Wisconsin 337 Internet Time Server", August 2003, 338 . 340 Author's Address 342 David Plonka 343 University of Wisconsin - Madison 345 EMail: plonka AT doit DOT wisc DOT edu 346 URI: http://net.doit.wisc.edu/~plonka/ 348 Appendix A. Background 350 In June 2003, the University of Wisconsin discovered that a network 351 product vendor named NetGear had manufactured and shipped over 352 700,000 routers with firmware containing a hard-coded reference to 353 the IP address of one of the University's NTP servers: 354 128.105.39.11, which was also known as "ntp1.cs.wisc.edu", a public 355 stratum-2 NTP server. 357 Due to that embedded fixed configuration and an unrelated bug in the 358 SNTP client, the affected products occasionally exhibit a failure 359 mode in which each flawed router produces one query per second 360 destined for the IP address 128.105.39.11, and hence produces a 361 large-scale flood of Internet traffic from hundreds-of-thousands of 362 source addresses, destined for the University's network, resulting in 363 significant operational problems. 365 These flawed routers are widely deployed throughout the global 366 Internet and are likely to remain in use for years to come. As such, 367 the University of Wisconsin with the cooperation of NetGear will 368 build a new anycast time service which aims to mitigate the damage 369 caused by the misbehavior of these flawed routers. 371 A technical report regarding the details of this situation is 372 available on the world wide web: Flawed Routers Flood University of 373 Wisconsin Internet Time Server [9]. 375 Intellectual Property Statement 377 The IETF takes no position regarding the validity or scope of any 378 intellectual property or other rights that might be claimed to 379 pertain to the implementation or use of the technology described in 380 this document or the extent to which any license under such rights 381 might or might not be available; neither does it represent that it 382 has made any effort to identify any such rights. Information on the 383 IETF's procedures with respect to rights in standards-track and 384 standards-related documentation can be found in BCP-11. 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