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Is this intentional? -- Found something which looks like a code comment -- if you have code sections in the document, please surround them with '' and '' lines. 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 153, but not defined == Unused Reference: 'RFC3736' is defined on line 675, but no explicit reference was found in the text ** Obsolete normative reference: RFC 3736 (Obsoleted by RFC 8415) ** Obsolete normative reference: RFC 3315 (Obsoleted by RFC 8415) Summary: 3 errors (**), 0 flaws (~~), 4 warnings (==), 3 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 Intended status: Standards Track G. Daley 5 Expires: August 18, 2010 NetStar Networks 6 February 14, 2010 8 Simple procedures for Detecting Network Attachment in IPv6 9 draft-ietf-dna-simple-14 11 Abstract 13 Detecting Network Attachment allows hosts to assess if its existing 14 addressing or routing configuration is valid for a newly connected 15 network. This document provides simple procedures for detecting 16 network attachment in IPv6 hosts, and procedures for routers to 17 support such services. 19 Status of this Memo 21 This Internet-Draft is submitted to IETF in full conformance with the 22 provisions of BCP 78 and BCP 79. 24 Internet-Drafts are working documents of the Internet Engineering 25 Task Force (IETF), its areas, and its working groups. Note that 26 other groups may also distribute working documents as Internet- 27 Drafts. 29 Internet-Drafts are draft documents valid for a maximum of six months 30 and may be updated, replaced, or obsoleted by other documents at any 31 time. It is inappropriate to use Internet-Drafts as reference 32 material or to cite them other than as "work in progress." 34 The list of current Internet-Drafts can be accessed at 35 http://www.ietf.org/ietf/1id-abstracts.txt. 37 The list of Internet-Draft Shadow Directories can be accessed at 38 http://www.ietf.org/shadow.html. 40 This Internet-Draft will expire on August 18, 2010. 42 Copyright Notice 44 Copyright (c) 2010 IETF Trust and the persons identified as the 45 document authors. All rights reserved. 47 This document is subject to BCP 78 and the IETF Trust's Legal 48 Provisions Relating to IETF Documents 49 (http://trustee.ietf.org/license-info) in effect on the date of 50 publication of this document. Please review these documents 51 carefully, as they describe your rights and restrictions with respect 52 to this document. Code Components extracted from this document must 53 include Simplified BSD License text as described in Section 4.e of 54 the Trust Legal Provisions and are provided without warranty as 55 described in the BSD License. 57 Table of Contents 59 1. Requirements notation . . . . . . . . . . . . . . . . . . . . 3 60 2. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 61 2.1. Goals . . . . . . . . . . . . . . . . . . . . . . . . . . 3 62 2.2. Applicability . . . . . . . . . . . . . . . . . . . . . . 4 63 2.3. Link Identification model . . . . . . . . . . . . . . . . 4 64 2.4. DNA Overview . . . . . . . . . . . . . . . . . . . . . . . 4 65 2.5. Working Assumptions . . . . . . . . . . . . . . . . . . . 5 66 3. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 5 67 4. Host Operations . . . . . . . . . . . . . . . . . . . . . . . 6 68 4.1. Host data structures . . . . . . . . . . . . . . . . . . . 6 69 4.1.1. SDAT Maintenance . . . . . . . . . . . . . . . . . . . 6 70 4.2. Steps involved in detecting link change . . . . . . . . . 7 71 4.3. Link-Layer Indication . . . . . . . . . . . . . . . . . . 7 72 4.4. Sending Neighbor Discovery probes . . . . . . . . . . . . 7 73 4.5. Contents of the Neighbor Discovery messages . . . . . . . 9 74 4.5.1. Neighbor Solicitation messages . . . . . . . . . . . . 9 75 4.5.2. Router Solicitation messages . . . . . . . . . . . . . 9 76 4.6. DHCPv6 operation . . . . . . . . . . . . . . . . . . . . . 10 77 4.7. Response Gathering . . . . . . . . . . . . . . . . . . . . 10 78 4.7.1. Conflicting results . . . . . . . . . . . . . . . . . 11 79 4.8. Further Host Operations . . . . . . . . . . . . . . . . . 11 80 4.9. Recommended retransmission behavior . . . . . . . . . . . 12 81 5. Pseudocode for Simple DNA . . . . . . . . . . . . . . . . . . 13 82 6. Constants . . . . . . . . . . . . . . . . . . . . . . . . . . 15 83 7. Relationship to DNAv4 . . . . . . . . . . . . . . . . . . . . 15 84 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 15 85 9. Security Considerations . . . . . . . . . . . . . . . . . . . 15 86 10. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 16 87 11. References . . . . . . . . . . . . . . . . . . . . . . . . . . 16 88 11.1. Normative References . . . . . . . . . . . . . . . . . . . 16 89 11.2. Informative References . . . . . . . . . . . . . . . . . . 17 90 Appendix A. Issues with confirming manually assigned addresses . 17 91 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 18 93 1. Requirements notation 95 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 96 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 97 document are to be interpreted as described in [RFC2119]. 99 2. Introduction 101 Hosts require procedures to simply and reliably identify if they have 102 moved to a network to which they had been recently connected. In 103 order to detect reconnection to a previously visited network, router 104 and neighbor discovery messages are used to collect reachability and 105 configuration information. This information is used to detect if the 106 host has attached to a link for which it may still have valid address 107 and other configuration information, and which it can use until it 108 receives confirmation through either through the Neighbor Discovery 109 protocol or DHCPv6. 111 This document incorporates feedback from host and router operating 112 systems implementors, which seeks to make implementation and adoption 113 of IPv6 change detection procedures simple for general use. 115 2.1. Goals 117 The goal of this document is to specify a simple procedure for 118 detecting network attachment (Simple DNA) that has the following 119 characteristics. 121 o Routers do not have to be modified to support this scheme. 123 o The most common use cases are optimized. 125 o In the worst case, detection latency is equal to that of standard 126 neighbor discovery so that performance is never degraded. 128 o False positives are not acceptable. A host MUST NOT wrongly 129 conclude that it has reattached to a previouly visited network. 131 o False negatives are acceptable. A host MAY fail to identify a 132 previously visited link correctly and attempt to acquire fresh 133 addressing and configuration information. 135 2.2. Applicability 137 The Simple DNA protocol provides substantial benefits over standard 138 neighbor discovery procedures [RFC4861] in some scenarios and does 139 not provide any benefit at all in certain other scenarios. This is 140 intentional as Simple DNA was designed for simplicity rather than 141 completeness. In particular, the Simple DNA protocol provides 142 maximum benefits when a host moves between a small set of known 143 links. When a host moves to a completely new link that is previously 144 unknown, the performance of the Simple DNA protocol will be identical 145 to that using standard neighbor discovery procedures [RFC4861]. In 146 this case the main benefit of the Simple DNA protocol is to 147 immediately flush out the inoperable addresses and configuration 148 instead of timing them out. The Simple DNA procedure provides 149 support for addresses configured using either IPv6 Stateless Address 150 Autoconfiguration [RFC4862] or DHCPv6 [RFC3315]. It does not support 151 manually configured addresses since they are not widely used and can 152 cause unpredictable results and/or aggressive probing behavior 153 [Appendix A]. 155 2.3. Link Identification model 157 Earlier methods of detecting network attachment, e.g. the procedure 158 defined in [I-D.ietf-dna-protocol], relied on detecting whether the 159 host was still connected to the same link. If the host was attached 160 to the same link, all information related to the link such as the 161 routers, prefixes and configuration parameters was considered to be 162 valid. The Simple DNA protocol follows an alternate approach where 163 it relies on probing each previously known router to determine 164 whether to use information learnt from THAT router. This allows 165 simple DNA to probe routers learnt from multiple earlier attachments 166 to optimize movement between a known set of links. 168 2.4. DNA Overview 170 Detecting Network Attachment is performed by hosts after detecting a 171 link-layer "up" indication. The host simultaneously sends multicast 172 Router Solicitations (RSs) and unicast Neighbor Solicitations (NSs) 173 in order to determine whether previously encountered routers are 174 present on the link. 176 Hosts implementing simple DNA may also send DHCPv6 packets, as 177 described in Section 4.6. Since simple DNA does not modify the 178 DHCPv6 protocol or state machine, the operation of DHCPv6 is 179 unchanged. 181 Routers that follow the standard neighbor discovery procedure 182 described in [RFC4861] will delay the router advertisement by a 183 random period between 0 and MAX_RA_DELAY_TIME (defined to be 500ms) 184 as described in Section 6.2.6 of [RFC4861]. Hosts implementing 185 simple DNA can detect the presence of a previously encountered router 186 using unicast Neighbor Solicitations. As a result, where the host 187 with a valid configuration is returning to a previously encountered 188 link, delays in the sending of a Router Advertisement (RA) will not 189 delay configuration as long as NS probing is successful. However in 190 situations where the host is attaching to a link for the first time, 191 or where it does not have a valid IP address on the link, it will be 192 dependent on the receipt of an RA for stateless auto-configuration. 193 In these situations delays in the receipt of an RA can be significant 194 and may result in service disruption. 196 2.5. Working Assumptions 198 There are a series of assumptions about the network environment which 199 underpin these procedures. 201 o The combination of the link layer address and the link local IPv6 202 address of a router is unique across links. 204 o Hosts receive indications when a link-layer comes up. Without 205 this, they would not know when to commence the DNA procedure. 207 If these assumptions do not hold, host change detection systems will 208 not function optimally. In that case, they may occasionally detect 209 change spuriously, or experience some delay in detecting network 210 attachment. The delays so experienced will be no longer than those 211 caused by following the standard neighbor discovery procedure 212 described in [RFC4861]. 214 3. Terminology 216 +---------------------+---------------------------------------------+ 217 | Term | Definition | 218 +---------------------+---------------------------------------------+ 219 | Valid IPv6 address | An IPv6 address configured on the node that | 220 | | has a valid lifetime greater than zero. | 221 | | | 222 | Operable IPv6 | An IPv6 address configured on the node that | 223 | address | can be used safely on the current link. | 224 +---------------------+---------------------------------------------+ 226 Table 1: Simple DNA Terminology 228 4. Host Operations 230 On connecting to a new point of attachment, the host performs the 231 detecting network attachment procedure in order to determine whether 232 the existing addressing and configuration information are still 233 valid. 235 4.1. Host data structures 237 In order to correctly perform the procedure described in this 238 document the host needs to maintain a data structure called the 239 Simple DNA address table (SDAT). The host needs to maintain this 240 data structure for each interface on which it performs Simple DNA. 241 Each entry in the SDAT table consists of at least the following 242 parameters. 244 o IPv6 address and its related parameters like valid lifetime, 245 preferred lifetime etc. 247 o Prefix from which the address was formed. 249 o Link-local IPv6 address(es) of the router(s) that advertised the 250 prefix. 252 o Link-layer (MAC) address(es) of the router(s) that advertised the 253 prefix. 255 o Flag indicating whether the address was obtained using SLAAC or 256 DHCPv6. 258 o DHCP specific information in case DHCPv6 [RFC3315] was used to 259 acquire the address. This information includes DUID, IA_ID, a 260 flag indicating IA_NA/IA_TA, configuration information such as DNS 261 server address, NTP server address etc. 263 4.1.1. SDAT Maintenance 265 The host SHOULD maintain the SDAT table by periodically cleaning out 266 entries whose valid lifetimes have expired. The host MAY also 267 maintain the table by allowing SDAT entries from "n" previously 268 visited links. When the host attaches to a previously unknown link 269 and the SDAT already contains entries from the previous "n" attached 270 links,it will discard all the SDAT entries corrsponding to the least 271 recently attached link. 273 4.2. Steps involved in detecting link change 275 The steps involved in basic detection of network attachment are: 277 o Link-Layer Indication 279 o Sending of neighbor discovery and/or DHCPv6 probes 281 o Response gathering and assessment 283 These steps are described below. 285 4.3. Link-Layer Indication 287 In order to start Detection of network attachment procedures, a host 288 typically requires a link-layer indication that the medium has become 289 available [RFC4957]. 291 After the indication is received, the host considers all currently 292 configured (non-tentative) IP addresses to be deprecated until the 293 change detection process completes. It MUST also set all Neighbor 294 Cache entries for the routers on its Default Router List to STALE. 295 This is done to speed up the acquisition of a new default router when 296 link change has occurred. 298 4.4. Sending Neighbor Discovery probes 300 When a host receives a link-layer "up" indication, it SHOULD 301 immediately send both a Router Solicitation (as specified in as 302 specified in section 6.3.7 of [RFC4861]) and if it retains at least 303 one valid IPv6 address, one or more unicast Neighbor Solicitations. 304 The Router Solicitation is sent to the All-routers multicast address 305 using a link-local address as the source address [RFC4861]. Even if 306 the host is in possession of more than one valid IPv6 address, it 307 MUST send only one router solicitation using a valid link-local 308 address as the source address. 310 For each of the addresses in the SDAT, the host looks up the SDAT to 311 find out the link-local and MAC addresses of the router(s) that 312 advertised the prefix used to form the address. It then sends an 313 unicast Neighbor Solicitations to each router's link-local address it 314 obtained from the lookup on the SDAT. The host MUST NOT send unicast 315 Neighbor Solicitations to a test node corresponding to an IPv6 316 address that is no longer valid. 318 Please note that the Neighbor Solicitations SHOULD be sent in 319 parallel with the Router Solicitation. Since sending NSs is just an 320 optimization, doing the NSs and the RS in parallel ensures that the 321 procedure does not run slower than it would if it only used an RS. 323 NOTE: A Simple DNA implementation SHOULD limit its probing to at most 324 six previously seen routers 326 4.5. Contents of the Neighbor Discovery messages 328 4.5.1. Neighbor Solicitation messages 330 This section describes the contents of the neighbor solicitation 331 probe messages sent during the probing procedure. 333 Source Address: A link-local address assigned to the 334 probing host. 336 Destination Address: The link-local address of the router being 337 probed as learnt from the SDAT. 339 Hop Limit: 255 341 ND Options: 343 Target Address: The link-local address of the router being 344 probed as learnt from the SDAT. 346 Link Layer Header: 348 Destination Address: The link-layer (MAC) address of the router 349 being probed as learnt from the SDAT. 351 The probing node SHOULD include the Source link-layer address option 352 in the probe messages. 354 4.5.2. Router Solicitation messages 356 This section describes the contents of the router solicitation probe 357 message sent during the probing procedure. 359 Source Address: A link-local address assigned to the 360 probing host. 362 Destination Address: The all-routers multicast address. 364 Hop Limit: 255 366 The probing node SHOULD NOT include the Source link-layer address 367 option in the probe messages. 369 4.6. DHCPv6 operation 371 Simple DNA does not require a host to implement DHCPv6, nor does it 372 imply any changes to the DHCPv6 protocol or state machine. Hosts MAY 373 attempt to obtain IPv6 configuration via DHCPv6 in parallel with 374 simple DNA probing. This ensures that the simple DNA procedure will 375 not result in additional delay in the case where reachability tests 376 fail, or where a DHCPv6 exchange completes more quickly than the 377 reachability tests. 379 In situations where both simple DNA and DHCPv6 are used on the same 380 link, it is possible that simple DNA probing will complete 381 successfully, and then DHCPv6 will complete later with a different 382 result. If this happens, the procedure described in Section 4.7.1 383 are utilized. 385 The host attempts to verify its DHCPv6-obtained information in 386 parallel with simple DNA. On receiving a link-layer "up" indication, 387 it will initiate a DHCPv6 exchange when and as specified in [RFC3315] 388 in order to verify whether the addresses and configuration obtained 389 using DHCPv6 are still usable on the link. 391 4.7. Response Gathering 393 When a responding Neighbor Advertisement is received from a test 394 node, the host MUST verify that both the IPv6 and link layer (MAC) 395 addresses of the test node match the expected values before utilizing 396 the configuration associated with the detected network (prefixes, MTU 397 etc.). 399 On reception of a Router Advertisement that contains prefixes that 400 intersect with those previously advertised by a known router, the 401 host utilizes the addresses in the SDAT associated with the detected 402 network. 404 If the host receives a router advertisement from a router containing 405 only prefixes that are disjoint from the prefixes associated with the 406 same router in the SDAT, then the host MUST conclude that the IPv6 407 addresses corresponding to that router are no longer valid. Since 408 any NS probes to that router will no longer provide useful 409 information, further probing of that router MUST be aborted. 410 Furthermore, the host MUST remove all the SDAT entries corresponding 411 to this router. 413 Where the conclusions obtained from the Neighbor Solicitation/ 414 Advertisement from a given router and the RS/RA exchange with the 415 same router differ, the results obtained from the RS/RA will be 416 considered definitive. In case the Neighbor Advertisement was 417 secured using SEND and the Router Advertisement was not, the host 418 MUST wait for SEND_NA_GRACE_TIME to see if a SEND-secured RA is 419 received. If a SEND-secured RA is not received, the conclusions 420 obtained from the NS/NA exchange will be considered definitive. 422 When the host receives a Router Advertisement from a given router, 423 the host MUST look for a Neighbor Cache entry for the sending router 424 and MUST mark that router's Neighbor Cache Entry as REACHABLE if one 425 was found. The host MUST add a new Neighbor Cache Entry in the 426 REACHABLE state for the sending router if one does not currently 427 exist. 429 4.7.1. Conflicting results 431 In situations where Neighbor Solicitation probes and Router 432 Solicitation probes are used on the same link, it is possible that 433 the NS probe will complete successfully, and then the RS probe will 434 complete later with a different result. If this happens, the 435 implementation SHOULD abandon the results obtained from the NS probe 436 of the router that responded to the RS and the implementation SHOULD 437 behave as if the NS probe did not successfully complete. 439 4.8. Further Host Operations 441 Operations subsequent to detecting network attachment depend upon 442 whether or not the host has reconnected to a previously visited 443 network. 445 After confirming the reachability of the associated router using an 446 NS/NA pair, the host performs the following steps. 448 o The host SHOULD rejoin any solicited nodes' multicast groups for 449 addresses it continues to use. 451 o The host SHOULD select a default router as described in Section 452 6.3.6 of [RFC4861]. 454 If the host has determined that it has reattached to a previously 455 visited link, it SHOULD NOT perform duplicate address detection on 456 the addresses that have been confirmed to be operable. 458 If the NS based probe with a router did not complete or if the RS 459 based probe on the same router completed with different prefixes than 460 the ones in the SDAT the host MUST begin address configuration 461 techniques, as indicated in a received Router Advertisement 462 [RFC4861][RFC4862]. 464 4.9. Recommended retransmission behavior 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 Solicitations or DHCPv6 retransmissions. 482 If a response is received to any unicast Neighbor Solicitation or 483 Router Solicitation message, pending retransmissions MUST be 484 canceled. A Simple DNA implementation SHOULD NOT retransmit a 485 Neighbor Solicitation more than twice. To provide damping in the 486 case of spurious Link Up indications, the host SHOULD NOT perform the 487 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 NOTE: This section does not include any pseudo-code for sending of 586 the DHCPv6 packets since the DHCPv6 exchange is orthogonal to the 587 simple DNA process. 589 6. Constants 591 SEND_NA_GRACE_TIME 593 Definition: An optional period to wait after Neighbor 594 Solicitation before adopting a non-SEND RA's link change 595 information. 597 Value: 40 milliseconds 599 7. Relationship to DNAv4 601 DNAv4 [RFC4436] specifies a set of steps that optimize the (common) 602 case of re-attachment to an IPv4 network that one has been connected 603 to previously by attempting to re-use a previous (but still valid) 604 configuration. This document shares the same goal as DNAv4 (that of 605 minimizing the handover latency in moving between points of 606 attachment) but differs in the steps it performs to achieve this 607 goal. Another difference is that this document also supports 608 stateless autoconfiguration of addresses in addition to addresses 609 configured using DHCPv6. 611 8. IANA Considerations 613 There are no changes to IANA registries required in this document. 615 9. Security Considerations 617 A host may receive Router Advertisements from non-SEND devices, after 618 receiving a link-layer indications. While it is necessary to assess 619 quickly whether a host has moved to another network, it is important 620 that the host's current secured SEND [RFC3971] router information is 621 not replaced by an attacker which spoofs an RA and purports to change 622 the link. 624 As such, the host SHOULD send a Neighbor Solicitation to the existing 625 SEND router upon link-up indication as described above in 626 Section 4.3. The host SHOULD then ensure that unsecured router 627 information does not cause deletion of existing SEND state, within 628 MIN_DELAY_BETWEEN_RAS, in order to allow for a present SEND router to 629 respond. 631 If the current default router is a SEND-secured router, the host 632 SHOULD wait SEND_NA_GRACE_TIME after transmission before adopting a 633 new default router. 635 Even if SEND signatures on RAs are used, it may not be immediately 636 clear if the router is authorized to make such advertisements. As 637 such, a host SHOULD NOT treat such devices as secure until and unless 638 authorization delegation discovery is successful. 640 Unless SEND or other form of secure address configuration is used, 641 the DNA procedure does not in itself provide positive, secure 642 authentication of the router(s) on the network, or authentication of 643 the network itself, as e.g. would be provided by mutual 644 authentication at the link layer. Therefore when such assurance is 645 not available, the host MUST NOT make any security-sensitive 646 decisions based on the DNA procedure alone. In particular, it MUST 647 NOT decide that it has moved from an untrusted to a trusted network, 648 and MUST NOT make any security decisions that depend on the 649 determination that such a transition has occurred. 651 10. Acknowledgments 653 This document is the product of a discussion the authors had with 654 Bernard Aboba, Thomas Narten, Erik Nordmark and Dave Thaler at IETF 655 69. The authors would like to thank them for clearly detailing the 656 requirements of the solution and the goals it needed to meet and for 657 helping to explore the solution space. The authors would like to 658 thank the authors and editors of the complete DNA specification for 659 detailing the overall problem space and solutions. The authors would 660 like to thank Jari Arkko for driving the evolution of a simple and 661 probabilistic DNA solution. The authors would like to thank Bernard 662 Aboba, Thomas Narten, Jari Arkko, Sathya Narayan, Julien Laganier, 663 Domagoj Premec, Jin Hyeock-Choi, Alfred Hoenes, Frederic Rossi, Ralph 664 Droms, Ted Lemon, Erik Nordmark, Lars Eggert, Brian Carpenter and 665 Yaron Sheffer for performing reviews on the document and providing 666 valuable comments to drive the document forward. 668 11. References 670 11.1. Normative References 672 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 673 Requirement Levels", BCP 14, RFC 2119, March 1997. 675 [RFC3736] Droms, R., "Stateless Dynamic Host Configuration Protocol 676 (DHCP) Service for IPv6", RFC 3736, April 2004. 678 [RFC3315] Droms, R., Bound, J., Volz, B., Lemon, T., Perkins, C., 679 and M. Carney, "Dynamic Host Configuration Protocol for 680 IPv6 (DHCPv6)", RFC 3315, July 2003. 682 [RFC3971] Arkko, J., Kempf, J., Zill, B., and P. Nikander, "SEcure 683 Neighbor Discovery (SEND)", RFC 3971, March 2005. 685 [RFC4861] Narten, T., Nordmark, E., Simpson, W., and H. Soliman, 686 "Neighbor Discovery for IP version 6 (IPv6)", RFC 4861, 687 September 2007. 689 11.2. Informative References 691 [I-D.ietf-dna-protocol] 692 Narayanan, S., "Detecting Network Attachment in IPv6 693 Networks (DNAv6)", draft-ietf-dna-protocol (work in 694 progress), June 2007. 696 [RFC4957] Krishnan, S., Montavont, N., Njedjou, E., Veerepalli, S., 697 and A. Yegin, "Link-Layer Event Notifications for 698 Detecting Network Attachments", RFC 4957, August 2007. 700 [RFC4862] Thomson, S., Narten, T., and T. Jinmei, "IPv6 Stateless 701 Address Autoconfiguration", RFC 4862, September 2007. 703 [RFC4436] Aboba, B., Carlson, J., and S. Cheshire, "Detecting 704 Network Attachment in IPv4 (DNAv4)", RFC 4436, March 2006. 706 Appendix A. Issues with confirming manually assigned addresses 708 Even though DNAv4 [RFC4436] supports verification of manually 709 assigned addresses this feature of DNAv4 has not been widely 710 implemented or used. There are two major issues that come up with 711 confirming manually assigned addresses using Simple DNA. 713 o When DHCPv6 or SLAAC addresses are used for probing, there is no 714 need to aggressively retransmit lost probes. This is because the 715 address configuration falls back to vanilla DHCPv6 or SLAAC and 716 the host will eventually obtain an address. This is not the case 717 with manually assigned addresses. If the probes are lost, the 718 host runs the risk of ending up with no addresses at all. Hence 719 agressive retransmissions are necessary. 721 o Another issue comes up when the host moves between two networks, 722 one where manual addressing is being used (say NET1)and the other 723 where dynamic addressing (stateless autoconfig or DHCPv6) is being 724 used (say NET2). Since the host can obtain a dynamic address in 725 some situations, it will need to send simple DNA probes and may 726 also engage in a DHCPv6 exchange. In a situation where the host 727 moves to NET1 and the NS probes are lost and in addition an RA is 728 not received, the host will not be able to confirm that it 729 attached to NET1, and therefore that it should use the manual 730 configuration for that network. As a result, if DHCPv6 is enabled 731 on NET1, then the host could mistakenly obtain a dynamic address 732 and configuration instead of using the manual configuration. To 733 prevent this problem, simple DNA probing needs to continue even 734 after the DHCPv6 exchange has completed, and DNA probes need to 735 take precedence over DHCPv6, contrary to the advice provided in 736 Section 4.7.1 738 Given these issues, it is NOT RECOMMENDED to use manual addressing 739 with Simple DNA. 741 Authors' Addresses 743 Suresh Krishnan 744 Ericsson 745 8400 Decarie Blvd. 746 Town of Mount Royal, QC 747 Canada 749 Phone: +1 514 345 7900 x42871 750 Email: suresh.krishnan@ericsson.com 752 Greg Daley 753 NetStar Networks 754 Level 9/636 St Kilda Rd 755 Melbourne, Victoria 3004 756 Australia 758 Phone: +61 3 8532 4042 759 Email: gdaley@netstarnetworks.com