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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) == Missing Reference: 'Appendix A' is mentioned on line 142, but not defined ** Obsolete normative reference: RFC 3736 (Obsoleted by RFC 8415) ** Obsolete normative reference: RFC 3315 (Obsoleted by RFC 8415) Summary: 3 errors (**), 0 flaws (~~), 3 warnings (==), 4 comments (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Network Working Group S. Krishnan 3 Internet-Draft Ericsson 4 Updates: 4861 (if approved) G. Daley 5 Intended status: Standards Track NetStar Networks 6 Expires: March 20, 2010 September 16, 2009 8 Simple procedures for Detecting Network Attachment in IPv6 9 draft-ietf-dna-simple-09 11 Status of this Memo 13 This Internet-Draft is submitted to IETF in full conformance with the 14 provisions of BCP 78 and BCP 79. 16 Internet-Drafts are working documents of the Internet Engineering 17 Task Force (IETF), its areas, and its working groups. Note that 18 other groups may also distribute working documents as Internet- 19 Drafts. 21 Internet-Drafts are draft documents valid for a maximum of six months 22 and may be updated, replaced, or obsoleted by other documents at any 23 time. It is inappropriate to use Internet-Drafts as reference 24 material or to cite them other than as "work in progress." 26 The list of current Internet-Drafts can be accessed at 27 http://www.ietf.org/ietf/1id-abstracts.txt. 29 The list of Internet-Draft Shadow Directories can be accessed at 30 http://www.ietf.org/shadow.html. 32 This Internet-Draft will expire on March 20, 2010. 34 Copyright Notice 36 Copyright (c) 2009 IETF Trust and the persons identified as the 37 document authors. All rights reserved. 39 This document is subject to BCP 78 and the IETF Trust's Legal 40 Provisions Relating to IETF Documents in effect on the date of 41 publication of this document (http://trustee.ietf.org/license-info). 42 Please review these documents carefully, as they describe your rights 43 and restrictions with respect to this document. 45 Abstract 47 Detecting Network Attachment allows hosts to assess if its existing 48 addressing or routing configuration is valid for a newly connected 49 network. 51 This document provides simple procedures for detecting network 52 attachment in IPv6 hosts, and procedures for routers to support such 53 services. 55 Table of Contents 57 1. Requirements notation . . . . . . . . . . . . . . . . . . . . 3 58 2. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 59 2.1. Goals . . . . . . . . . . . . . . . . . . . . . . . . . . 3 60 2.2. Applicability . . . . . . . . . . . . . . . . . . . . . . 4 61 2.3. Link Identification model . . . . . . . . . . . . . . . . 4 62 2.4. DNA Roles . . . . . . . . . . . . . . . . . . . . . . . . 4 63 2.5. Working Assumptions . . . . . . . . . . . . . . . . . . . 5 64 3. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 5 65 4. Host Operations . . . . . . . . . . . . . . . . . . . . . . . 6 66 4.1. Host data structures . . . . . . . . . . . . . . . . . . . 6 67 4.2. Steps involved in detecting link change . . . . . . . . . 6 68 4.3. Link-Layer Indication . . . . . . . . . . . . . . . . . . 7 69 4.4. Sending Neighbor Discovery probes . . . . . . . . . . . . 7 70 4.5. Contents of the Neighbor Discovery messages . . . . . . . 8 71 4.5.1. Neighbor Solicitation messages . . . . . . . . . . . . 8 72 4.5.2. Router Solicitation messages . . . . . . . . . . . . . 8 73 4.6. Sending DHCPv6 probes . . . . . . . . . . . . . . . . . . 9 74 4.7. Response Gathering . . . . . . . . . . . . . . . . . . . . 9 75 4.7.1. Conflicting results . . . . . . . . . . . . . . . . . 10 76 4.8. Further Host Operations . . . . . . . . . . . . . . . . . 10 77 4.9. Recommended retransmission behavior . . . . . . . . . . . 11 78 5. Pseudocode for Simple DNA . . . . . . . . . . . . . . . . . . 12 79 6. Constants . . . . . . . . . . . . . . . . . . . . . . . . . . 14 80 7. Relationship to DNAv4 . . . . . . . . . . . . . . . . . . . . 14 81 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 14 82 9. Security Considerations . . . . . . . . . . . . . . . . . . . 14 83 10. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 15 84 11. References . . . . . . . . . . . . . . . . . . . . . . . . . . 15 85 11.1. Normative References . . . . . . . . . . . . . . . . . . . 15 86 11.2. Informative References . . . . . . . . . . . . . . . . . . 15 87 Appendix A. Issues with confirming manually assigned addresses . 16 88 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 16 90 1. Requirements notation 92 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 93 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 94 document are to be interpreted as described in [RFC2119]. 96 2. Introduction 98 Hosts require procedures to simply and reliably identify if they have 99 moved to a different IP network to the one which they have been 100 recently connected. In order to detect change, router and neighbor 101 discovery messages are used to collect reachability and configuration 102 information. This information is used to detect whether the existing 103 router and address prefixes are likely to be present. 105 This document incorporates feedback from host and router operating 106 systems implementors, which seeks to make implementation and adoption 107 of IPv6 change detection procedures simple for general use. 109 2.1. Goals 111 The goal of this document is to specify a simple procedure for 112 detecting network attachment (Simple DNA) that has the following 113 characteristics. 115 o Routers do not have to be modified to support this scheme. 117 o Handle only the simplest and most likely use cases. 119 o Work at least as quickly as standard neighbor discovery. 121 o False positives are not acceptable. A host should not conclude 122 that there is no link change when there is one. 124 o False negatives are acceptable. A host can conclude that there is 125 a link change when there is none. 127 2.2. Applicability 129 The Simple DNA protocol provides substantial benefits in some 130 scenarios and does not provide any benefit at all in certain other 131 scenarios. This is intentional as Simple DNA was designed for 132 simplicity rather than completeness. In particular, the Simple DNA 133 protocol provides maximum benefits when a host moves between a small 134 set of known links. When a host moves to a completely new link that 135 is previously unknown, the performance of the Simple DNA protocol 136 will be identical to that using standard neighbor discovery 137 procedures [RFC4861]. The Simple DNA procedure provides support for 138 addresses configured using either IPv6 Stateless Address 139 Autoconfiguration [RFC4862] or DHCPv6 [RFC3315]. It does not support 140 manually configured addresses since they are not widely used and can 141 cause unpredictable results and/or aggressive probing behavior 142 [Appendix A]. 144 2.3. Link Identification model 146 Earlier methods of detecting network attachment, e.g. the procedure 147 defined in [I-D.ietf-dna-protocol], relied on detecting whether the 148 host was still connected to the same link. If the host was attached 149 to the same link, all information related to the link such as the 150 routers, prefixes and configuration parameters was considered to be 151 valid. The Simple DNA protocol follows an alternate approach where 152 it relies on probing each previously known router to determine 153 whether to use information learnt from THAT router. This allows 154 simple DNA to probe routers learnt from multiple earlier attachments 155 to optimize movement between a known set of links. 157 2.4. DNA Roles 159 Detecting Network Attachment is performed by hosts by sending IPv6 160 neighbor discovery and router discovery messages to routers after 161 connecting to a network. 163 It is desirable that routers adopt procedures which allow for fast 164 unicast Router Advertisement (RA) messages. Routers that follow the 165 standard neighbor discovery procedure described in [RFC4861] will 166 delay the router advertisement by a random period between 0 and 167 MAX_RA_DELAY_TIME (defined to be 500ms) as described in Section 6.2.6 168 of [RFC4861]. This delay can be significant and may result in 169 service disruption. Please note that support for fast unicast RAs is 170 not necessary since the simple dna procedure can continue to work 171 using the NS/NA exchange, which will complete earlier than the RA 172 arrives. 174 The host detects that the link-layer may have changed, and then 175 simultaneously probes the network with Router Solicitations (RSs) and 176 Neighbor Solicitations (NSs). The host uses advertisements to 177 determine if the routers it currently has configured are still 178 available. 180 Additionally, on links with no statelessly configured addresses, the 181 host may make use of DHCPv6 procedures to identify an operable 182 address. 184 2.5. Working Assumptions 186 There are a series of assumptions about the network environment which 187 underpin these procedures. 189 o The combination of the link layer address and the link local IPv6 190 address of a router is unique across links. 192 o Hosts receive indications when a link-layer comes up. Without 193 this, they would not know when to commence the DNA procedure. 195 If these assumptions do not hold, host change detection systems will 196 not function optimally. In that case, they may occasionally detect 197 change spuriously, or experience some delay in detecting network 198 attachment. The delays so experienced will be no longer than those 199 caused by following the standard neighbor discovery procedure 200 described in [RFC4861]. 202 3. Terminology 204 +---------------------+---------------------------------------------+ 205 | Term | Definition | 206 +---------------------+---------------------------------------------+ 207 | Valid IPv6 address | An IPv6 address configured on the node that | 208 | | has a valid lifetime greater than zero. | 209 | | | 210 | Operable IPv6 | An IPv6 address configured on the node that | 211 | address | can be used safely on the current link. | 212 +---------------------+---------------------------------------------+ 214 Table 1: Simple DNA Terminology 216 4. Host Operations 218 When a host has an existing configuration for IP address prefixes and 219 next hop routing, it may be disconnected from its link-layer, and 220 then subsequently reconnect the link-layer on the same interface. 222 When the link-layer becomes available again, it is important to 223 determine whether the existing addressing and routing configuration 224 are still valid. 226 In order to determine this, the host performs the detecting network 227 attachment procedure. 229 4.1. Host data structures 231 In order to correctly perform the procedure described in this 232 document the host needs to maintain a data structure called the 233 Simple DNA address table (SDAT). This data structure is maintained 234 by the host on a per interface basis. Each entry in the SDAT table 235 consists of at least the following parameters. 237 o IPv6 address and its related parameters like valid lifetime. 239 o Prefix from which the address was formed. 241 o Link-local IPv6 address of the router that advertised the prefix. 243 o Link-layer (MAC) address of the router that advertised the prefix. 245 o DHCP Unique IDentifier (DUID) in case DHCPv6 was used to acquire 246 the address [RFC3315]. 248 4.2. Steps involved in detecting link change 250 The steps involved in basic detection of network attachment are: 252 o Link-Layer Indication 254 o Sending of neighbor discovery or DHCPv6 probes 256 o Response gathering and assessment 258 These steps are described below. 260 4.3. Link-Layer Indication 262 In order to start Detection of network attachment procedures, a host 263 typically requires a link-layer indication that the medium has become 264 available [RFC4957]. 266 After the indication is received, the host considers all currently 267 configured (non-tentative) IP addresses to be deprecated until the 268 change detection process completes. It SHOULD also set all Neighbor 269 Cache entries for the routers on its Default Router List to STALE. 270 This is done to speed up the acquisition of a new default router when 271 link change has occurred. 273 4.4. Sending Neighbor Discovery probes 275 When a host receives a link-layer "up" indication, it SHOULD 276 immediately send both a Router Solicitation and if it retains at 277 least one valid IPv6 address, one or more unicast Neighbor 278 Solicitations. The Router Solicitation is sent to the All-routers 279 multicast address using a link-local address as the source address 280 [RFC4861]. Even if the host is in possession of more than one valid 281 IPv6 address, it MUST send only one router solicitation using a valid 282 link-local address as the source address. 284 For the purpose of sending neighbor solicitations to previous 285 routers, the host first identifies the set of operable IPv6 addresses 286 (candidate set) that it wishes to use. If the addresses obtained 287 from a previous router are no longer valid, the host does not include 288 these addresses in the candidate set for NS based probing. 290 For each of the addresses in the candidate set, the host looks up the 291 SDAT to find out the link-local and MAC addresses of the router that 292 advertised the prefix used to form the address. It then sends an 293 unicast Neighbor Solicitations to each router's link-local address it 294 obtained from the lookup on the SDAT. The host SHOULD NOT send 295 unicast Neighbor Solicitations to a test node corresponding to an 296 IPv6 address that is no longer valid. 298 Please note that the Neighbor Solicitations SHOULD be sent in 299 parallel with the Router Solicitations. Since sending NSs is just an 300 optimization, doing the NSs and RSs in parallel ensures that the 301 procedure does not run slower than it would if it only used an RS. 303 4.5. Contents of the Neighbor Discovery messages 305 4.5.1. Neighbor Solicitation messages 307 This section describes the contents of the neighbor solicitation 308 probe messages sent during the probing procedure. 310 Source Address: A link-local address assigned to the 311 probing host. 313 Destination Address: The link-local address of the router being 314 probed as learnt from the SDAT. 316 Hop Limit: 255 318 ND Options: 320 Target Address: The link-local address of the router being 321 probed as learnt from the SDAT. 323 Link Layer Header: 325 Destination Address: The link-layer (MAC) address of the router 326 being probed as learnt from the SDAT. 328 The probing node SHOULD NOT include the Source link-layer address 329 option in the probe messages. 331 4.5.2. Router Solicitation messages 333 This section describes the contents of the router solicitation probe 334 message sent during the probing procedure. 336 Source Address: A link-local address assigned to the 337 probing host. 339 Destination Address: The all-routers multicast address. 341 Hop Limit: 255 343 The probing node SHOULD include a Source link-layer address option in 344 the probe messages if the address was obtained using DHCPv6 and the 345 lease has not expired. Otherwise the probing node SHOULD NOT include 346 the Source link-layer address option in the probe messages. 348 4.6. Sending DHCPv6 probes 350 Where the host has acquired addresses from DHCPv6 or the host does 351 not have a global prefix, it MAY prefer to use DHCPv6 probe messages 352 in parallel with the Neighbor Discovery probing. The DHCPv6 probing 353 procedures described in this document do not imply any changes to the 354 DHCPv6 protocol or state machine. 356 In that case, when the host receives a link-layer indication, it 357 sends a DHCPv6 SOLICIT to All_DHCP_Relay_Agents_and_Servers. This 358 message contains an Identity Association for either a Temporary 359 Address (IA_TA) or Non-Temporary Address (IA_NA) [RFC3315]. Where an 360 existing valid address is being tested for operability, this address 361 should be placed in the Identity Association's IAADDR element, and 362 the DUID associated with that address should be copied to the DHCP 363 SOLICIT from the SDAT. 365 In order to quickly acquire a new address in the case that link 366 change has occurred, this SOLICIT message MAY contain the Rapid- 367 Commit option. 369 Where the Rapid-Commit option has not been used, a present DHCP 370 server will respond with an ADVERTISE message. The IP address 371 contained in the Identity Association (IA_TA or IA_NA) will contain 372 an IP Address which is operable for the link. 374 Where Rapid-Commit option has been sent, a DHCPv6 server will respond 375 with REPLY. In addition to being operable, this address is allocated 376 to the host for the lease duration indicated in the Identity 377 Association. 379 4.7. Response Gathering 381 When a responding Neighbor Advertisement is received from a test 382 node, the host MUST verify that both the IPv6 and link layer (MAC) 383 addresses of the test node match the expected values before utilizing 384 the configuration associated with the detected network (prefixes, MTU 385 etc.). 387 On reception of a Router Advertisement or advertising DHCPv6 message 388 (a REPLY or ADVERTISE) which contains prefixes that intersect with 389 those previously advertised by a known router, the host utilizes the 390 configuration associated with the detected network. 392 When the host receives an advertisement containing only prefixes 393 which are disjoint from known advertised prefixes, the host MUST 394 determine whether the solicited advertisement corresponds to any of 395 the routers probed via NS. If it does, then the host SHOULD conclude 396 that the IPv6 addresses corresponding to that router are no longer 397 valid. Since any NS probes to that router will no longer provide 398 useful information, further probing of that router SHOULD be aborted. 400 Where the conclusions obtained from the Neighbor Solicitation/ 401 Advertisement from a given router and the RS/RA exchange with the 402 same router differ, the results obtained from the RS/RA will be 403 considered definitive. 405 When the host receives a Router Advertisement in reply to the Router 406 Solicitation it sent, the host SHOULD look for a Neighbor Cache entry 407 for the sending router and SHOULD mark that router's Neighbor Cache 408 Entry as REACHABLE if one was found. The host SHOULD add a new 409 Neighbor Cache Entry in the REACHABLE state for the sending router if 410 one does not currently exist. 412 4.7.1. Conflicting results 414 It is possible that the DHCPv6 based probes and the neighbor 415 discovery based probes complete with conflicting results. In this 416 case, the host SHOULD use the following rules to determine the final 417 result. 419 o If the DHCPv6 exchange was authenticated, use the result from the 420 DHCPv6 probe. 422 o If the DHCPv6 exchange was not authenticated and the neighbor 423 discovery exchange was protected by SEND [RFC3971], use the result 424 from the neighbor discovery probe. 426 o If both the DHCPv6 and neighbor discovery exchanges were not 427 authenticated, use the result from the DHCPv6 probe 429 4.8. Further Host Operations 431 Operations subsequent to detecting network attachment depend upon 432 whether change was detected. 434 After confirming the reachability of the associated router using an 435 NS/NA pair, the host performs the following steps. 437 o The host SHOULD rejoin any solicited nodes' multicast groups for 438 addresses it continues to use. 440 o The host SHOULD select a default router as described in [RFC4861]. 442 If the host has determined that there has been no link change, it 443 SHOULD NOT perform duplicate address detection on the addresses that 444 have been confirmed to be operable. 446 If the NS based probe with a router did not complete or if the RS 447 based probe on the same router completed with different prefixes than 448 the ones in the SDAT the host MUST unconfigure all the existing 449 addresses received from the given router, and MUST begin address 450 configuration techniques, as indicated in the received Router 451 Advertisement [RFC4861][RFC4862]. 453 4.9. Recommended retransmission behavior 455 In situations where Neighbor Solicitation probes and Router 456 Solicitation probes are used on the same link, it is possible that 457 the NS probe will complete successfully, and then the RS probe will 458 complete later with a different result. If this happens, the 459 implementation SHOULD abandon the results obtained from the NS probe 460 of the router that responded to the RS and the implementation SHOULD 461 behave as if the NS probe did not successfully complete. If the 462 confirmed address was assigned manually, the implementation SHOULD 463 NOT unconfigure the manually assigned address and SHOULD log an error 464 about the mismatching prefix. 466 Where the NS probe does not complete successfully, it usually implies 467 that the host is not attached to the network whose configuration is 468 being tested. In such circumstances, there is typically little value 469 in aggressively retransmitting unicast neighbor solicitations that do 470 not elicit a response. 472 Where unicast Neighbor Solicitations and Router Solicitations are 473 sent in parallel, one strategy is to forsake retransmission of 474 Neighbor Solicitations and to allow retransmission only of Router 475 Solicitations or DHCPv6. In order to reduce competition between 476 unicast Neighbor Solicitations and Router Solicitations and DHCPv6 477 retransmissions, a DNAv6 implementation that retransmits may utilize 478 the retransmission strategy described in the DHCPv6 specification 479 [RFC3315], scheduling DNAv6 retransmissions between Router 480 Solicitation or DHCPv6 retransmissions. 482 If a response is received to any unicast Neighbor Solicitation, 483 Router Solicitation or DHCPv6 message, pending retransmissions MUST 484 be canceled [RFC3315][RFC3736]. A Simple DNA implementation SHOULD 485 NOT retransmit a Neighbor Solicitation more than twice. To provide 486 damping in the case of spurious Link Up indications, the host SHOULD 487 NOT perform the Simple DNA procedure more than once a second. 489 5. Pseudocode for Simple DNA 491 /* Link up indication received on INTERFACE */ 492 /* Start Simple DNA process */ 494 /* Mark All Addresses as deprecated */ 495 Configured_Address_List=Get_Address_List(INTERFACE); 496 foreach Configured_Address in Configured_Address_List 497 { 498 if (Get_Address_State(Configured_Address)!=AS_TENTATIVE) 499 { 500 Set_Address_State(Configured_Address,AS_DEPRECATED); 501 } 502 } 504 /* Mark all routers' NC entries as STALE to speed up */ 505 /* acquisition of new router if link change has occurred */ 506 foreach Router_Address in DEFAULT_ROUTER_LIST 507 { 508 NCEntry=Get_Neighbor_Cache_Entry(Router_Address); 509 Set_Neighbor_Cache_Entry_State(NCEntry,NCS_STALE); 510 } 512 /* Thread A : Send Router Solicitation */ 513 RS_Target_Address=FF02::2; 514 RS_Source_Address=Get_Any_Link_Local_Address(INTERFACE); 515 Send_Router_Solicitation(RS_Source_Address,RS_Target_Address); 517 /* Thread B : Send Neighbor Solicitation(s) */ 518 Previously_Known_Router_List=Get_Router_List_from_SDAT(); 519 NS_Source_Address=Get_Any_Link_Local_Address(INTERFACE); 521 foreach Router_Address in Previously_Known_Router_List 522 { 523 if (Get_Any_Valid_Address_from_SDAT(Router_Address)) 524 { 525 Send_Neighbor_Solicitation(NS_Source_Address,Router_Address); 526 } 527 } 529 /* Thread C : Response collection */ 531 /* Received Router Advertisement processing */ 532 /* Only for RAs received as response to DNA RSs */ 534 L3_Source=Get_L3_Source(RECEIVED_MESSAGE); 535 L2_Source=Get_L2_Source(RECEIVED_MESSAGE); 536 SDAT_Entry_List=Get_Entries_from_SDAT_L2L3(L3_Source,L2_Source)); 537 foreach SDAT_Entry in SDAT_Entry_List 538 { 539 if (Exists_PIO(RECEIVED_MESSAGE,Get_Prefix(SDAT_Entry))) 540 { 541 /* Address is operable. Configure on Interface */ 542 /* Rejoin solicited-node multicast group for address */ 543 } 544 else 545 { 546 /* If address is configured on interface, remove it */ 547 /* This could be because of a NA arriving before RA */ 548 } 549 } 551 /* Mark router as reachable */ 552 NCEntry=Get_Neighbor_Cache_Entry(L3_Source); 553 if (NCEntry is not NULL) 554 { 555 Set_Neighbor_Cache_Entry_State(NCEntry,NCS_REACHABLE); 556 } 557 else 558 { 559 Create_Neighbor_Cache_Entry(L3_Source,NCS_REACHABLE); 560 } 562 /* Ignore further NAs from this router */ 563 Add_Router_to_NA_Ignore_List(L3_Source); 565 /* Received Neighbor Advertisement processing */ 566 /* Only for NAs received as response to DNA NSs */ 568 L3_Source=Get_L3_Source(RECEIVED_MESSAGE); 569 L2_Source=Get_L2_Source(RECEIVED_MESSAGE); 571 if (Is_Router_on_NA_Ignore_List(L3_Source)) { 572 /* Ignore message and wait for next message */ 573 continue; 574 } 576 SDAT_Entry_List=Get_Entries_from_SDAT_L2L3(L3_Source,L2_Source)); 578 foreach SDAT_Entry in SDAT_Entry_List 579 { 580 /* Address is operable. Configure on Interface */ 581 } 583 Figure 1: Pseudocode for Simple DNA 585 6. Constants 587 SEND_NA_GRACE_TIME 589 Definition: An optional period to wait after Neighbor 590 Solicitation before adopting a non-SEND RA's link change 591 information. 593 Value: 40 milliseconds 595 7. Relationship to DNAv4 597 DNAv4 [RFC4436] specifies a set of steps that optimize the (common) 598 case of re-attachment to an IPv4 network that one has been connected 599 to previously by attempting to re-use a previous (but still valid) 600 configuration. This document shares the same goal as DNAv4 (that of 601 minimizing the handover latency in moving between points of 602 attachment) but differs in the steps it performs to achieve this 603 goal. Another difference is that this document also supports 604 stateless autoconfiguration of addresses in addition to addresses 605 configured using DHCPv6. 607 8. IANA Considerations 609 There are no changes to IANA registries required in this document. 611 9. Security Considerations 613 A host may receive Router Advertisements from non-SEND devices, after 614 receiving a link-layer indications. While it is necessary to assess 615 quickly whether a host has moved to another network, it is important 616 that the host's current secured SEND [RFC3971] router information is 617 not replaced by an attacker which spoofs an RA and purports to change 618 the link. 620 As such, the host SHOULD send a Neighbor Solicitation to the existing 621 SEND router upon link-up indication as described above in 622 Section 4.3. The host SHOULD then ensure that unsecured router 623 information does not cause deletion of existing SEND state, within 624 MIN_DELAY_BETWEEN_RAS, in order to allow for a present SEND router to 625 respond. 627 If the current default router is a SEND-secured router, the host 628 SHOULD wait SEND_NA_GRACE_TIME after transmission before adopting a 629 new default router. 631 Even if SEND signatures on RAs are used, it may not be immediately 632 clear if the router is authorized to make such advertisements. As 633 such, a host SHOULD NOT treat such devices as secure until and unless 634 authorization delegation discovery is successful. 636 10. Acknowledgments 638 This document is the product of a discussion the authors had with 639 Bernard Aboba, Thomas Narten, Erik Nordmark and Dave Thaler at IETF 640 69. The authors would like to thank them for clearly detailing the 641 requirements of the solution and the goals it needed to meet and for 642 helping to explore the solution space. The authors would like to 643 thank the authors and editors of the complete DNA specification for 644 detailing the overall problem space and solutions. The authors would 645 like to thank Jari Arkko for driving the evolution of a simple and 646 probabilistic DNA solution. The authors would like to thank Bernard 647 Aboba, Thomas Narten, Jari Arkko, Sathya Narayan, Julien Laganier, 648 Domagoj Premec, Jin Hyeock-Choi, Alfred Hoenes and Frederic Rossi for 649 performing reviews on the document and providing valuable comments to 650 drive the document forward. 652 11. References 654 11.1. Normative References 656 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 657 Requirement Levels", BCP 14, RFC 2119, March 1997. 659 [RFC3736] Droms, R., "Stateless Dynamic Host Configuration Protocol 660 (DHCP) Service for IPv6", RFC 3736, April 2004. 662 [RFC3315] Droms, R., Bound, J., Volz, B., Lemon, T., Perkins, C., 663 and M. Carney, "Dynamic Host Configuration Protocol for 664 IPv6 (DHCPv6)", RFC 3315, July 2003. 666 [RFC3971] Arkko, J., Kempf, J., Zill, B., and P. Nikander, "SEcure 667 Neighbor Discovery (SEND)", RFC 3971, March 2005. 669 [RFC4861] Narten, T., Nordmark, E., Simpson, W., and H. Soliman, 670 "Neighbor Discovery for IP version 6 (IPv6)", RFC 4861, 671 September 2007. 673 11.2. Informative References 675 [I-D.ietf-dna-protocol] 676 Narayanan, S., "Detecting Network Attachment in IPv6 677 Networks (DNAv6)", draft-ietf-dna-protocol (work in 678 progress), June 2007. 680 [RFC4957] Krishnan, S., Montavont, N., Njedjou, E., Veerepalli, S., 681 and A. Yegin, "Link-Layer Event Notifications for 682 Detecting Network Attachments", RFC 4957, August 2007. 684 [RFC4862] Thomson, S., Narten, T., and T. Jinmei, "IPv6 Stateless 685 Address Autoconfiguration", RFC 4862, September 2007. 687 [RFC4436] Aboba, B., Carlson, J., and S. Cheshire, "Detecting 688 Network Attachment in IPv4 (DNAv4)", RFC 4436, March 2006. 690 Appendix A. Issues with confirming manually assigned addresses 692 Even though DNAv4 [RFC4436] supports verification of manually 693 assigned addresses this feature of DNAv4 has not been widely 694 implemented or used. There are two major issues that come up with 695 confirming manually assigned addresses using Simple DNA. 697 o When DHCPv6 or SLAAC addresses are used for probing, there is no 698 need to aggressively retransmit lost probes. This is because the 699 address configuration falls back to vanilla DHCPv6 or SLAAC and 700 the host will eventually obtain an address. This is not the case 701 with manually assigned addresses. If the probes are lost, the 702 host runs the risk of ending up with no addresses at all. Hence 703 agressive retransmissions are mandated. 705 o Another issue comes up when the host moves between two networks, 706 one where manual addressing is being used (say NET1)and the other 707 where dynamic addressing (DHCPv6) is being used (say NET2). When 708 the host moves to NET1 from NET2 it tries to confirm both the 709 manual address and the dynamic address in parallel. If the probe 710 for the manually assigned address is lost, the DHCPv6 probe will 711 succeed and the host will incorrectly end up using the DHCPv6 712 assigned address (from NET2) on NET1. 714 Given these issues, it is NOT RECOMMENDED to use manual addressing 715 with Simple DNA. 717 Authors' Addresses 719 Suresh Krishnan 720 Ericsson 721 8400 Decarie Blvd. 722 Town of Mount Royal, QC 723 Canada 725 Phone: +1 514 345 7900 x42871 726 Email: suresh.krishnan@ericsson.com 728 Greg Daley 729 NetStar Networks 730 Level 9/636 St Kilda Rd 731 Melbourne, Victoria 3004 732 Australia 734 Phone: +61 3 8532 4042 735 Email: gdaley@netstarnetworks.com