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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) ** Obsolete normative reference: RFC 2460 (Obsoleted by RFC 8200) ** Obsolete normative reference: RFC 4941 (Obsoleted by RFC 8981) == Outdated reference: A later version (-02) exists of draft-gont-opsec-ipv6-host-scanning-01 Summary: 2 errors (**), 0 flaws (~~), 2 warnings (==), 1 comment (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 IPv6 maintenance Working Group (6man) F. Gont 3 Internet-Draft SI6 Networks / UTN-FRH 4 Intended status: Standards Track October 8, 2012 5 Expires: April 11, 2013 7 A method for Generating Stable Privacy-Enhanced Addresses with IPv6 8 Stateless Address Autoconfiguration (SLAAC) 9 draft-ietf-6man-stable-privacy-addresses-01 11 Abstract 13 This document specifies a method for generating IPv6 Interface 14 Identifiers to be used with IPv6 Stateless Address Autoconfiguration 15 (SLAAC), such that addresses configured using this method are stable 16 within each subnet, but the Interface Identifier changes when hosts 17 move from one network to another. The aforementioned method is meant 18 to be an alternative to generating Interface Identifiers based on 19 IEEE identifiers, such that the benefits of stable addresses can be 20 achieved without sacrificing the privacy of users. 22 Status of this Memo 24 This Internet-Draft is submitted in full conformance with the 25 provisions of BCP 78 and BCP 79. 27 Internet-Drafts are working documents of the Internet Engineering 28 Task Force (IETF). Note that other groups may also distribute 29 working documents as Internet-Drafts. The list of current Internet- 30 Drafts is at http://datatracker.ietf.org/drafts/current/. 32 Internet-Drafts are draft documents valid for a maximum of six months 33 and may be updated, replaced, or obsoleted by other documents at any 34 time. It is inappropriate to use Internet-Drafts as reference 35 material or to cite them other than as "work in progress." 37 This Internet-Draft will expire on April 11, 2013. 39 Copyright Notice 41 Copyright (c) 2012 IETF Trust and the persons identified as the 42 document authors. All rights reserved. 44 This document is subject to BCP 78 and the IETF Trust's Legal 45 Provisions Relating to IETF Documents 46 (http://trustee.ietf.org/license-info) in effect on the date of 47 publication of this document. Please review these documents 48 carefully, as they describe your rights and restrictions with respect 49 to this document. Code Components extracted from this document must 50 include Simplified BSD License text as described in Section 4.e of 51 the Trust Legal Provisions and are provided without warranty as 52 described in the Simplified BSD License. 54 Table of Contents 56 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 57 2. Design goals . . . . . . . . . . . . . . . . . . . . . . . . . 5 58 3. Algorithm specification . . . . . . . . . . . . . . . . . . . 6 59 4. Resolving Duplicate Address Detection (DAD) conflicts . . . . 9 60 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10 61 6. Security Considerations . . . . . . . . . . . . . . . . . . . 11 62 7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 12 63 8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 13 64 8.1. Normative References . . . . . . . . . . . . . . . . . . . 13 65 8.2. Informative References . . . . . . . . . . . . . . . . . . 13 66 Appendix A. Privacy issues still present with RFC 4941 . . . . . 15 67 A.1. Host tracking . . . . . . . . . . . . . . . . . . . . . . 15 68 A.1.1. Tracking hosts across networks #1 . . . . . . . . . . 15 69 A.1.2. Tracking hosts across networks #2 . . . . . . . . . . 15 70 A.1.3. Revealing the identity of devices performing 71 server-like functions . . . . . . . . . . . . . . . . 16 72 A.2. Address scanning attacks . . . . . . . . . . . . . . . . . 16 73 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 17 75 1. Introduction 77 [RFC4862] specifies the Stateless Address Autoconfiguration (SLAAC) 78 for IPv6 [RFC2460], which typically results in hosts configuring one 79 or more "stable" addresses composed of a network prefix advertised by 80 a local router, and an Interface Identifier (IID) that typically 81 embeds a hardware address (e.g., using IEEE identifiers) [RFC4291]. 83 Generally, static addresses are thought to simplify network 84 management, since they simplify Access Control Lists (ACLs) and 85 logging. However, since IEEE identifiers are typically globally 86 unique, the resulting IPv6 addresses can be leveraged to track and 87 correlate the activity of a node over time and across multiple 88 subnets and networks, thus negatively affecting the privacy of users. 90 The "Privacy Extensions for Stateless Address Autoconfiguration in 91 IPv6" [RFC4941] were introduced to complicate the task of 92 eavesdroppers and other information collectors to correlate the 93 activities of a node, and basically result in temporary (and random) 94 Interface Identifiers that are typically more difficult to leverage 95 than those based on IEEE identifiers. When privacy extensions are 96 enabled, "privacy addresses" are employed for "outgoing 97 communications", while the traditional IPv6 addresses based on IEEE 98 identifiers are still used for "server" functions (i.e., receiving 99 incoming connections). 101 As noted in [RFC4941], "anytime a fixed identifier is used in 102 multiple contexts, it becomes possible to correlate seemingly 103 unrelated activity using this identifier". Therefore, since 104 "privacy addresses" [RFC4941] do not eliminate the use of fixed 105 identifiers for server-like functions, they only *partially* 106 mitigate the correlation of host activities (see Appendix A for 107 some example attacks that are still possible with privacy 108 addresses). Therefore, it is vital that the privacy 109 characteristics of "stable" addresses are improved such that the 110 ability of an attacker correlating host activities across networks 111 is reduced. 113 Another important aspect not mitigated by "Privacy Addresses" 114 [RFC4941] is that of host scanning. Since IPv6 addresses that 115 embed IEEE identifiers have specific patterns, an attacker could 116 leverage such patterns to greatly reduce the search space for 117 "live" hosts. Since "privacy addresses" do not eliminate the use 118 of IPv6 addresses that embed IEEE identifiers, host scanning 119 attacks are still feasible even if "privacy extensions" are 120 employed [Gont-DEEPSEC2011] [CPNI-IPv6]. This is yet another 121 motivation to improve the privacy characteristics of "stable" 122 addresses (currently embedding IEEE identifiers). 124 Privacy/temporary addresses can be challenging in a number of areas. 125 For example, from a network-management point of view, they tend to 126 increase the complexity of event logging, trouble-shooting, and 127 enforcing access controls and quality of service, etc. As a result, 128 some organizations disable the use of privacy addresses even at the 129 expense of reduced privacy [Broersma]. Also, they result in 130 increased complexity, which might not be possible or desirable in 131 some implementations (e.g., some embedded devices). 133 In scenarios in which "Privacy Extensions" are deliberately not used 134 (possibly for any of the aforementioned reasons), all a host is left 135 with is the addresses that have been generated using e.g. IEEE 136 identifiers, and this is yet another case in which it is also vital 137 that the privacy characteristics of these stable addresses are 138 improved. 140 We note that in most (if not all) of those scenarios in which 141 "Privacy Extensions" are disabled, there is usually no actual desire 142 to negatively affect user privacy, but rather a desire to simplify 143 operation of the network (simplify the use of ACLs, logging, etc.). 145 This document specifies a method to generate interface identifiers 146 that are stable/constant within each subnet, but that change as hosts 147 move from one network to another, thus keeping the "stability" 148 properties of the interface identifiers specified in [RFC4291], while 149 still mitigating host-scanning attacks and preventing correlation of 150 the activities of a node as it moves from one network to another. 152 For nodes that currently disable "Privacy extensions" [RFC4941] for 153 some of the reasons stated above, this mechanism provides stable 154 privacy-enhanced addresses which may already address most of the 155 privacy concerns related to addresses that embed IEEE identifiers 156 [RFC4291]. On the other hand, in scenarios in which "Privacy 157 Extensions" are employed, implementation of the mechanism described 158 in this document would mitigate host-scanning attacks and also 159 mitigate correlation of host activities. 161 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 162 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 163 document are to be interpreted as described in RFC 2119 [RFC2119]. 165 2. Design goals 167 This document specifies a method for selecting interface identifiers 168 to be used with IPv6 SLAAC, with the following goals: 170 o The resulting interface identifiers remain constant/stable for 171 each prefix used with SLAAC within each subnet. That is, the 172 algorithm generates the same interface identifier when configuring 173 an address belonging to the same prefix within the same subnet. 175 o The resulting interface identifiers do not depend on the 176 underlying hardware (e.g. link-layer address). This means that 177 e.g. replacing a Network Interface Card (NIC) will not have the 178 (generally undesirable) effect of changing the IPv6 addresses used 179 for that network interface. 181 o The resulting interface identifiers do change when addresses are 182 configured for different prefixes. That is, if different 183 autoconfiguration prefixes are used to configure addresses for the 184 same network interface card, the resulting interface identifiers 185 must be (statistically) different. 187 o It must be difficult for an outsider to predict the interface 188 identifiers that will be generated by the algorithm, even with 189 knowledge of the interface identifiers generated for configuring 190 other addresses. 192 o The aforementioned interface identifiers are meant to be an 193 alternative to those based on e.g. IEEE identifiers, such as 194 those specified in [RFC2464]. 196 We note that of use of the algorithm specified in this document is 197 (to a large extent) orthogonal to the use of "Privacy Extensions" 198 [RFC4941]. Hosts that do not implement/use "Privacy Extensions" 199 would have the benefit that they would not be subject to the host- 200 tracking and host scanning issues discussed in the previous section. 201 On the other hand, in the case of hosts employing "Privacy 202 Extensions", the method specified in this document would prevent host 203 scanning attacks and correlation of node activities across networks 204 (see Appendix A). 206 3. Algorithm specification 208 IPv6 implementations conforming to this specification MUST generate 209 interface identifiers using the algorithm specified in this section 210 in replacement of any other algorithms used for generating "stable" 211 addresses (such as that specified in [RFC2464]). The aforementioned 212 algorithm MUST be employed for generating the interface identifiers 213 for all of the IPv6 addresses configured with SLAAC for a given 214 interface, including IPv6 link-local addresses. Implementations 215 conforming to this specification SHOULD provide the means for a 216 system administrator to enable or disable the use of this algorithm 217 for generating Interface Identifiers. Implementations conforming to 218 this specification MAY employ the algorithm specified in [RFC4941] to 219 generate temporary addresses in addition to the addresses generated 220 with the algorithm specified in this document. 222 Unless otherwise noted, all of the parameters included in the 223 expression below MUST be included when generating an Interface ID. 225 1. Compute a random (but stable) identifier with the expression: 227 RID = F(Prefix, Interface_Index, Network_ID, DAD_Counter, 228 secret_key) 230 Where: 232 RID: 233 Random (but stable) identifier 235 F(): 236 A pseudorandom function (PRF) that is not computable from the 237 outside (without knowledge of the secret key). The PRF could 238 be implemented as a cryptographic hash of the concatenation of 239 each of the function parameters. 241 Prefix: 242 The prefix to be used for SLAAC, as learned from an ICMPv6 243 Router Advertisement message. 245 Interface_Index: 246 The interface index [RFC3493] [RFC3542] corresponding to this 247 network interface. 249 Network_ID: 250 Some network specific data that identifies the subnet to which 251 this interface is attached. For example the IEEE 802.11 252 Service Set Identifier (SSID) corresponding to the network to 253 which this interface is associated. This parameter is 254 OPTIONAL. 256 DAD_Counter: 257 A counter that is employed to resolve Duplicate Address 258 Detection (DAD) conflicts. It MUST be initialized to 0, and 259 incremented by 1 for each new tentative address that is 260 configured as a result of a DAD conflict. See Section 4 for 261 additional details. 263 secret_key: 264 A secret key that is not known by the attacker. The secret 265 key MUST be initialized at system installation time to a 266 pseudo-random number (see [RFC4086] for randomness 267 requirements for security). An implementation MAY provide the 268 means for the user to change the secret key. 270 2. The Interface Identifier is finally obtained by taking the 271 leftmost 64 bits of the RID value computed in the previous step, 272 and and setting bit 6 (the leftmost bit is numbered 0) to zero. 273 This creates an interface identifier with the universal/local bit 274 indicating local significance only. 276 Note that the result of F() in the algorithm above is no more secure 277 than the secret key. If an attacker is aware of the PRF that is 278 being used by the victim (which we should expect), and the attacker 279 can obtain enough material (i.e. addresses configured by the victim), 280 the attacker may simply search the entire secret-key space to find 281 matches. To protect against this, the secret key should be of a 282 reasonable length. Key lengths of at least 128 bits should be 283 adequate. The secret key is initialized at system installation time 284 to a pseudo-random number, thus allowing this mechanism to be 285 enabled/used automatically, without user intervention. 287 Including the SLAAC prefix in the PRF computation causes the 288 Interface ID to vary across networks that employ different prefixes, 289 thus mitigating host-tracking attacks and any other attacks that 290 benefit from predictable Interface IDs (such as host scanning). 292 Including the optional Network_ID parameter when computing the RID 293 value above would cause the algorithm to produce a different 294 Interface Identifier when connecting to different networks, even when 295 configuring addresses belonging to the same prefix. This means that 296 a host would employ a different Interface ID as it moves from one 297 network to another even for IPv6 link-local addresses or Unique Local 298 Addresses (ULAs). 300 Note that there are a number of ways in which these addresses 301 might leak out. For example, an attacker could use ICMPv6 Node 302 Information queries [RFC4620] to obtain such addresses. 304 4. Resolving Duplicate Address Detection (DAD) conflicts 306 If as a result of performing Duplicate Address Detection (DAD) 307 [RFC4862] a host finds that the tentative address generated with the 308 algorithm specified in Section 3 is a duplicate address, it MAY 309 resolve the address conflict by trying a new tentative address as 310 follows: 312 o DAD_Counter is incremented by 1. 314 o A new Interface ID is generated with the algorithm specified in 315 Section 3, using the incremented DAD_Counter value. 317 This procedure may be repeated a number of times until the address 318 conflict is resolved. However, hosts MUST limit the number of 319 tentative addresses that are tried (rather than indefinitely try a 320 new tentative address until the conflict is resolved). 322 In those (unlikely) scenarios in which duplicate addresses are 323 detected and in which the order in which the conflicting nodes 324 configure their addresses may vary (e.g., because they may be 325 bootstrapped in different order), the algorithm specified in this 326 section for resolving DAD conflicts could lead to addresses that are 327 not stable within the same subnet. In order to mitigate this 328 potential problem, nodes MAY record the DAD_Counter value employed 329 for a specific {Prefix, Interface_Index, Network_ID} tuple in non- 330 volatile memory, such that the same DAD_Counter value is employed 331 when configuring an address for the same Prefix and subnet at any 332 other point in time. 334 In the event that a DAD conflict cannot be solved (possibly after 335 trying a number of different addresses), address configuration would 336 fail. In those scenarios, nodes MUST NOT automatically fall back to 337 employing other algorithms for generating interface identifiers. 339 5. IANA Considerations 341 There are no IANA registries within this document. The RFC-Editor 342 can remove this section before publication of this document as an 343 RFC. 345 6. Security Considerations 347 This document specifies an algorithm for generating interface 348 identifiers to be used with IPv6 Stateless Address Autoconfiguration 349 (SLAAC), in replacement of e.g. interface identifiers that embed IEEE 350 identifiers (such as those specified in [RFC2464]). When compared to 351 such identifiers, the identifiers specified in this document have a 352 number of advantages: 354 o They prevent trivial host-tracking, since when a host moves from 355 one network to another the network prefix used for 356 autoconfiguration and/or the Network ID (e.g., IEEE 802.11 SSID) 357 will typically change, and hence the resulting interface 358 identifier will also change (see Appendix A. 360 o They mitigate host-scanning techniques which leverage predictable 361 interface identifiers (e.g., known Organizational Unique 362 Identifiers). 364 o They result in IPv6 addresses that are independent of the 365 underlying hardware (i.e. the resulting IPv6 addresses do not 366 change if a network interface card is replaced). 368 We note that this algorithm is meant to replace interface identifiers 369 such as those specified in [RFC2464], but not the temporary-addresses 370 such as those specified in [RFC4941]. Clearly, temporary addresses 371 may help to mitigate the correlation of activities of a node within 372 the same network, and may also reduce the attack exposure window 373 (since the lifetime of privacy/temporary IPv6 address is reduced when 374 compared to that of addresses generated with the method specified in 375 this document). We note that implementation of this algorithm would 376 still benefit those hosts employing "Privacy Addresses", since it 377 would mitigate host-tracking vectors still present when privacy 378 addresses are used (Appendix A, and would also mitigate host-scanning 379 techniques that leverage patterns in IPv6 addresses that embed IEEE 380 identifiers. 382 Finally, we note that the method described in this document may 383 mitigate most of the privacy concerns arising from the use of IPv6 384 addresses that embed IEEE identifiers, without the use of temporary 385 addresses, thus possibly offering an interesting trade-off for those 386 scenarios in which the use of temporary addresses is not feasible. 388 7. Acknowledgements 390 The author would like to thank (in alphabetical order) Karl Auer, 391 Steven Bellovin, Matthias Bethke, Dominik Elsbroek, Bob Hinden, 392 Christian Huitema, Ray Hunter, Jong-Hyouk Lee, and Michael 393 Richardson, for providing valuable comments on earlier versions of 394 this document. 396 This document is based on the technical report "Security Assessment 397 of the Internet Protocol version 6 (IPv6)" [CPNI-IPv6] authored by 398 Fernando Gont on behalf of the UK Centre for the Protection of 399 National Infrastructure (CPNI). 401 Fernando Gont would like to thank CPNI (http://www.cpni.gov.uk) for 402 their continued support. 404 8. References 406 8.1. Normative References 408 [RFC2460] Deering, S. and R. Hinden, "Internet Protocol, Version 6 409 (IPv6) Specification", RFC 2460, December 1998. 411 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 412 Requirement Levels", BCP 14, RFC 2119, March 1997. 414 [RFC4086] Eastlake, D., Schiller, J., and S. Crocker, "Randomness 415 Requirements for Security", BCP 106, RFC 4086, June 2005. 417 [RFC4291] Hinden, R. and S. Deering, "IP Version 6 Addressing 418 Architecture", RFC 4291, February 2006. 420 [RFC4862] Thomson, S., Narten, T., and T. Jinmei, "IPv6 Stateless 421 Address Autoconfiguration", RFC 4862, September 2007. 423 [RFC4941] Narten, T., Draves, R., and S. Krishnan, "Privacy 424 Extensions for Stateless Address Autoconfiguration in 425 IPv6", RFC 4941, September 2007. 427 8.2. Informative References 429 [RFC2464] Crawford, M., "Transmission of IPv6 Packets over Ethernet 430 Networks", RFC 2464, December 1998. 432 [RFC3493] Gilligan, R., Thomson, S., Bound, J., McCann, J., and W. 433 Stevens, "Basic Socket Interface Extensions for IPv6", 434 RFC 3493, February 2003. 436 [RFC3542] Stevens, W., Thomas, M., Nordmark, E., and T. Jinmei, 437 "Advanced Sockets Application Program Interface (API) for 438 IPv6", RFC 3542, May 2003. 440 [RFC4620] Crawford, M. and B. Haberman, "IPv6 Node Information 441 Queries", RFC 4620, August 2006. 443 [I-D.gont-opsec-ipv6-host-scanning] 444 Gont, F., "Network Reconnaissance in IPv6 Networks", 445 draft-gont-opsec-ipv6-host-scanning-01 (work in progress), 446 July 2012. 448 [Gont-DEEPSEC2011] 449 Gont, "Results of a Security Assessment of the Internet 450 Protocol version 6 (IPv6)", DEEPSEC 2011 Conference, 451 Vienna, Austria, November 2011, . 455 [Gont-BRUCON2012] 456 Gont, "Recent Advances in IPv6 Security", BRUCON 2012 457 Conference, Ghent, Belgium, September 2012, . 461 [Broersma] 462 Broersma, R., "IPv6 Everywhere: Living with a Fully IPv6- 463 enabled environment", Australian IPv6 Summit 2010, 464 Melbourne, VIC Australia, October 2010, 465 . 467 [CPNI-IPv6] 468 Gont, F., "Security Assessment of the Internet Protocol 469 version 6 (IPv6)", UK Centre for the Protection of 470 National Infrastructure, (available on request). 472 Appendix A. Privacy issues still present with RFC 4941 474 This section aims to clarify the motivation of using the method 475 specified in this document even when privacy/temporary addresses 476 [RFC4941] are employed. It discusses a (non-exaustive) number of 477 scenarios in which host privacy is still sacrificed even when 478 privacy/temporary addresses [RFC4941] are employed, as a result of 479 employing interface identifiers that are constant across networks 480 (e.g., those resulting from embedding IEEE identifiers). 482 A.1. Host tracking 484 This section describes one possible attack scenario that illustrates 485 that host-tracking may still be possible when privacy/temporary 486 addresses [RFC4941] are employed. 488 A.1.1. Tracking hosts across networks #1 490 A host configures its stable addresses with the constant 491 Interface-ID, and runs any application that needs to perform a 492 server-like function (e.g. a peer-to-peer application). As a result 493 of that, an attacker/user participating in the same application 494 (e.g., P2P) would learn the constant Interface-ID used by the host 495 for that network interface. 497 Some time later, the same host moves to a completely different 498 network, and employs the same P2P application, probably even with a 499 different username. The attacker now interacts with the same host 500 again, and hence can learn its newly-configured stable address. 501 Since the interface ID is the same as the one used before, the 502 attacker can infer that it is communicating with the same device as 503 before. 505 This is just *one* possible attack scenario, which should remind us 506 that one should not disclose more than it is really needed for 507 achieving a specific goal (and an Interface-ID that is constant 508 across different networks does exactly that: it discloses more 509 information than is needed for providing a stable address). 511 A.1.2. Tracking hosts across networks #2 513 Once an attacker learns the constant Interface-ID employed by the 514 victim host for its stable address, the attacker is able to "probe" a 515 network for the presence of such host at any given network. 517 See Appendix A.1.1 for just one example of how an attacker could 518 learn such value. Other examples include being able to share the 519 same network segment at some point in time (e.g. a conference 520 network or any public network), etc. 522 For example, if an attacker learns that in one network the victim 523 used the Interface-ID 1111:2222:3333:4444 for its stable addresses, 524 then he could subsequently probe for the presence of such device in 525 the network 2011:db8::/64 by sending a probe packet (ICMPv6 Echo 526 Request, or any other probe packet) to the address 2001:db8::1111: 527 2222:3333:4444. 529 A.1.3. Revealing the identity of devices performing server-like 530 functions 532 Some devices, such as storage devices or printers, may typically 533 perform server-like functions and may be usually moved from one 534 network to another. Such devices are likely to simply disable (or 535 not even implement) privacy/temporary addresses [RFC4941]. If the 536 aforementioned devices employ Interface-IDs that are constant across 537 networks, it would be trivial for an attacker to tell whether the 538 same device is being used across networks by simply looking at the 539 Interface ID. Clearly, performing server-like functions should not 540 imply that a device discloses its identity (i.e., that the attacker 541 can tell whether it is the same device providing some function in two 542 different networks, at two different points in time). 544 The scheme proposed in this document prevents such information 545 leakage by causing nodes to generate different Interface-IDs when 546 moving to one network to another, thus mitigating this kind of 547 privacy attack. 549 A.2. Address scanning attacks 551 While it is usually assumed that address-scanning attacks are 552 unfeasible, an attacker could leverage patterns in IPv6 addresses to 553 greatly reduce the search space [I-D.gont-opsec-ipv6-host-scanning] 554 [Gont-BRUCON2012]. 556 As noted earlier in this document, privacy/temporary addresses do not 557 eliminate the use of IPv6 addresses that embed IEEE identifiers, and 558 hence such hosts would still be vulnerable to address-scanning 559 attacks. The method specified in this document eliminates such 560 patterns and would thus mitigate the aforementioned address-scanning 561 attacks. 563 Author's Address 565 Fernando Gont 566 SI6 Networks / UTN-FRH 567 Evaristo Carriego 2644 568 Haedo, Provincia de Buenos Aires 1706 569 Argentina 571 Phone: +54 11 4650 8472 572 Email: fgont@si6networks.com 573 URI: http://www.si6networks.com