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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: February 26, 2011 NetStar Networks 6 August 25, 2010 8 Simple procedures for Detecting Network Attachment in IPv6 9 draft-ietf-dna-simple-17 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 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). Note that other groups may also distribute 26 working documents as Internet-Drafts. The list of current Internet- 27 Drafts is at http://datatracker.ietf.org/drafts/current/. 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 This Internet-Draft will expire on February 26, 2011. 36 Copyright Notice 38 Copyright (c) 2010 IETF Trust and the persons identified as the 39 document authors. All rights reserved. 41 This document is subject to BCP 78 and the IETF Trust's Legal 42 Provisions Relating to IETF Documents 43 (http://trustee.ietf.org/license-info) in effect on the date of 44 publication of this document. Please review these documents 45 carefully, as they describe your rights and restrictions with respect 46 to this document. Code Components extracted from this document must 47 include Simplified BSD License text as described in Section 4.e of 48 the Trust Legal Provisions and are provided without warranty as 49 described in the Simplified BSD License. 51 Table of Contents 53 1. Requirements notation . . . . . . . . . . . . . . . . . . . . 3 54 2. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 55 2.1. Goals . . . . . . . . . . . . . . . . . . . . . . . . . . 3 56 2.2. Applicability . . . . . . . . . . . . . . . . . . . . . . 4 57 2.3. Link Identification model . . . . . . . . . . . . . . . . 4 58 2.4. DNA Overview . . . . . . . . . . . . . . . . . . . . . . . 4 59 2.5. Working Assumptions . . . . . . . . . . . . . . . . . . . 5 60 3. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 6 61 4. The Simple DNA Address Table (SDAT) . . . . . . . . . . . . . 7 62 5. Host Operations . . . . . . . . . . . . . . . . . . . . . . . 7 63 5.1. On receipt of a Router Advertisement . . . . . . . . . . . 7 64 5.2. After assignment of a DHCPv6 address . . . . . . . . . . . 8 65 5.3. Steps involved in detecting link change . . . . . . . . . 8 66 5.4. Link-Layer Indication . . . . . . . . . . . . . . . . . . 8 67 5.5. Sending Neighbor Discovery probes . . . . . . . . . . . . 9 68 5.5.1. Sending Router Solicitations . . . . . . . . . . . . . 9 69 5.5.2. Sending Neighbor Solicitations . . . . . . . . . . . . 9 70 5.5.3. Concurrent sending of RS and NS probes . . . . . . . . 9 71 5.5.4. Initiating DHCPv6 exchange . . . . . . . . . . . . . . 9 72 5.6. Contents of the Neighbor Discovery messages . . . . . . . 11 73 5.6.1. Neighbor Solicitation messages . . . . . . . . . . . . 11 74 5.6.2. Router Solicitation messages . . . . . . . . . . . . . 11 75 5.7. Response Gathering . . . . . . . . . . . . . . . . . . . . 12 76 5.7.1. Receiving Neighbor Advertisements . . . . . . . . . . 12 77 5.7.2. Receiving Router Advertisements . . . . . . . . . . . 12 78 5.7.3. Conflicting results . . . . . . . . . . . . . . . . . 12 79 5.8. Further Host Operations . . . . . . . . . . . . . . . . . 12 80 5.9. On connecting to a new point of attachment . . . . . . . . 13 81 5.10. Periodic Maintenance of the SDAT . . . . . . . . . . . . . 13 82 5.11. Recommended retransmission behavior . . . . . . . . . . . 13 83 6. Pseudocode for Simple DNA . . . . . . . . . . . . . . . . . . 15 84 7. Constants . . . . . . . . . . . . . . . . . . . . . . . . . . 16 85 8. Relationship to DNAv4 . . . . . . . . . . . . . . . . . . . . 17 86 9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 17 87 10. Security Considerations . . . . . . . . . . . . . . . . . . . 17 88 11. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 18 89 12. References . . . . . . . . . . . . . . . . . . . . . . . . . . 18 90 12.1. Normative References . . . . . . . . . . . . . . . . . . . 18 91 12.2. Informative References . . . . . . . . . . . . . . . . . . 19 92 Appendix A. Issues with confirming manually assigned addresses . 19 93 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 20 95 1. Requirements notation 97 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 98 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 99 document are to be interpreted as described in [RFC2119]. 101 2. Introduction 103 Hosts require procedures to simply and reliably identify if they have 104 moved to a network to which they had been recently connected. In 105 order to detect reconnection to a previously visited network, router 106 and neighbor discovery messages are used to collect reachability and 107 configuration information. This information is used to detect if the 108 host has attached to a link for which it may still have valid address 109 and other configuration information, and which it can use until it 110 receives confirmation through either through the Neighbor Discovery 111 protocol or DHCPv6. 113 This document incorporates feedback from host and router operating 114 systems implementors, which seeks to make implementation and adoption 115 of IPv6 change detection procedures simple for general use. 117 2.1. Goals 119 The goal of this document is to specify a simple procedure for 120 detecting network attachment (Simple DNA) that has the following 121 characteristics. 123 o Routers do not have to be modified to support this scheme. 125 o The most common use cases are optimized. 127 o In the worst case, detection latency is equal to that of standard 128 neighbor discovery so that performance is never degraded. 130 o False positives are not acceptable. A host must not wrongly 131 conclude that it has reattached to a previouly visited network. 133 o False negatives are acceptable. A host may fail to identify a 134 previously visited link correctly and attempt to acquire fresh 135 addressing and configuration information. 137 2.2. Applicability 139 The Simple DNA protocol provides substantial benefits over standard 140 neighbor discovery procedures [RFC4861] in some scenarios and does 141 not provide any benefit at all in certain other scenarios. This is 142 intentional as Simple DNA was designed for simplicity rather than 143 completeness. In particular, the Simple DNA protocol provides 144 maximum benefits when a host moves between a small set of known 145 links. When a host moves to a completely new link that is previously 146 unknown, the performance of the Simple DNA protocol will be identical 147 to that using standard neighbor discovery procedures [RFC4861]. In 148 this case the main benefit of the Simple DNA protocol is to 149 immediately flush out the inoperable addresses and configuration 150 instead of timing them out. The Simple DNA procedure provides 151 support for addresses configured using either IPv6 Stateless Address 152 Autoconfiguration [RFC4862] or DHCPv6 [RFC3315]. It does not support 153 manually configured addresses since they are not widely used and can 154 cause unpredictable results and/or aggressive probing behavior 155 [Appendix A]. 157 2.3. Link Identification model 159 Earlier methods of detecting network attachment, e.g. the procedure 160 defined in [I-D.ietf-dna-protocol], relied on detecting whether the 161 host was still connected to the same link. If the host was attached 162 to the same link, all information related to the link such as the 163 routers, prefixes and configuration parameters was considered to be 164 valid. The Simple DNA protocol follows an alternate approach where 165 it relies on probing each previously known router to determine 166 whether to use information learnt from THAT router. This allows 167 simple DNA to probe routers learnt from multiple earlier attachments 168 to optimize movement between a known set of links. 170 2.4. DNA Overview 172 Detecting Network Attachment is performed by hosts after detecting a 173 link-layer "up" indication. The host uses a combination of unicast 174 Neighbor Solicitations (NSs) and multicast Router Solicitations (RSs) 175 in order to determine whether previously encountered routers are 176 present on the link, in which case an existing configuration can be 177 reused. If previously encountered routers are not present then 178 either IPv6 Stateless Address Autoconfiguration and/or DHCPv6 is used 179 for configuration. 181 Hosts implementing simple DNA may also send DHCPv6 packets, as 182 described in Section 5.5.4. Since simple DNA does not modify the 183 DHCPv6 protocol or state machine, the operation of DHCPv6 is 184 unchanged. 186 Routers that follow the standard neighbor discovery procedure 187 described in [RFC4861] will delay the router advertisement by a 188 random period between 0 and MAX_RA_DELAY_TIME (defined to be 500ms) 189 as described in Section 6.2.6 of [RFC4861]. In addition, consecutive 190 RAs sent to the all-nodes multicast address are rate limited to no 191 more than one advertisement every MIN_DELAY_BETWEEN_RAS (defined to 192 be 3 seconds). This will result in a worst-case delay of 3.5 seconds 193 in the absence of any packet loss. 195 Hosts implementing simple DNA can detect the presence of a previously 196 encountered router using unicast Neighbor Solicitations. As a 197 result, where the host with a valid configuration is returning to a 198 previously encountered link, delays in the sending of a Router 199 Advertisement (RA) will not delay configuration as long as NS probing 200 is successful. However in situations where the host is attaching to 201 a link for the first time, or where it does not have a valid IP 202 address on the link, it will be dependent on the receipt of an RA for 203 stateless auto-configuration. In these situations delays in the 204 receipt of an RA can be significant and may result in service 205 disruption. 207 2.5. Working Assumptions 209 There are a series of assumptions about the network environment which 210 underpin these procedures. 212 o The combination of the link layer address and the link local IPv6 213 address of a router is unique across links. 215 o Hosts receive indications when a link-layer comes up. Without 216 this, they would not know when to commence the DNA procedure. 218 If these assumptions do not hold, host change detection systems will 219 not function optimally. In that case, they may occasionally detect 220 change spuriously, or experience some delay in detecting network 221 attachment. The delays so experienced will be no longer than those 222 caused by following the standard neighbor discovery procedure 223 described in [RFC4861]. 225 3. Terminology 227 +---------------------+---------------------------------------------+ 228 | Term | Definition | 229 +---------------------+---------------------------------------------+ 230 | Valid IPv6 address | An IPv6 address configured on the node that | 231 | | has a valid lifetime greater than zero. | 232 | | | 233 | Operable IPv6 | An IPv6 address configured on the node that | 234 | address | can be used safely on the current link. | 235 | | | 236 | Router identifier | Identifier formed using the link-local | 237 | | address of a router along with its | 238 | | link-layer address. | 239 | | | 240 | D-Flag | Flag indicating whether the address was | 241 | | obtained using SLAAC or DHCPv6. If it is | 242 | | set to 0, then SLAAC was used to configure | 243 | | the address. If it is set to 1, then DHCPv6 | 244 | | was used to configure the address. | 245 | | | 246 | O-Flag | Flag indicating whether the address is | 247 | | operable. If it is set to 0, the address is | 248 | | inoperable. If it is set to 1, the address | 249 | | is operable. | 250 | | | 251 | S-Flag | Flag indicating whether SEND [RFC3971] was | 252 | | used in the Router Advertisement that | 253 | | resulted in the creation/modification of | 254 | | this SDAT entry. If it is set to 0, then | 255 | | SEND was not used. If it is set to 1, then | 256 | | SEND was used. | 257 | | | 258 | Candidate Router | A router address in the SDAT that is | 259 | Address | associated with at least one valid address. | 260 | | | 261 | Candidate Router | A set of router addresses that has been | 262 | Set | identified for NS based probing. | 263 +---------------------+---------------------------------------------+ 265 Table 1: Simple DNA Terminology 267 4. The Simple DNA Address Table (SDAT) 269 In order to correctly perform the procedure described in this 270 document the host needs to maintain a data structure called the 271 Simple DNA address table (SDAT). The host needs to maintain this 272 data structure for each interface on which it performs Simple DNA. 273 Each entry in the SDAT table will be indexed by the router identifier 274 (link-local + link layer address of the router) and consists of at 275 least the following parameters. Fields tagged as [S] are used for 276 addresses configured using SLAAC. Fields tagged as [D] are used for 277 addresses obtained using DHCPv6. Fields tagged as [S+D] are used in 278 both cases. 280 o [S+D]Link-local IPv6 address of the router(s) 282 o [S+D]Link-layer (MAC) address of the router(s) 284 o [S+D]Flag indicating whether the address was obtained using SLAAC 285 or DHCPv6.(The D-Flag) 287 o [S+D]IPv6 address and its related parameters like valid lifetime, 288 preferred lifetime etc. 290 o [S]Prefix from which the address was formed. 292 o [S]Flag indicating whether SEND was used.(The S-Flag) 294 o [D]DHCP specific information in case DHCPv6 [RFC3315] was used to 295 acquire the address. This information includes DUID, IA_ID, a 296 flag indicating IA_NA/IA_TA, configuration information such as DNS 297 server address, NTP server address etc. 299 o [S+D]Flag indicating whether the address is operable.(The O-Flag) 301 5. Host Operations 303 On connecting to a new point of attachment, the host performs the 304 detecting network attachment procedure in order to determine whether 305 the existing addressing and configuration information are still 306 valid. 308 5.1. On receipt of a Router Advertisement 310 When the host receives a Router Advertisement and the router 311 identifier of the sending router is not present in the SDAT, the host 312 processes the Router Advertisement as specified in Section 6.3.4. of 313 [RFC4861]. Additionally, the host performs the following operations. 315 If the Router Advertisement is protected by SEND the S-Flag MUST be 316 set to 1 in the SDAT entries created/modified by this RA. 318 o The host configures addresses out of the autoconfigurable prefixes 319 advertised in the RA, as specified in [RFC4862]. The host MUST 320 add an SDAT entry (indexed by this router identifier) for each 321 such address the host configures. 323 o The host might have already configured addresses out of the 324 autoconfigurable prefixes advertised in the RA. This could be a 325 result of receiving the prefix in an RA from another router on the 326 same link. The host MUST add an SDAT entry (indexed by this 327 router identifier) for each such address the host had already 328 configured. 330 o The host might have DHCPv6 assigned addresses that are known to be 331 operable on the link. The host MUST add an SDAT entry (indexed by 332 this router identifier) for each such DHCPv6 address. 334 5.2. After assignment of a DHCPv6 address 336 After the host is assigned an address by a DHCPv6 server, it needs to 337 associate the address with the routers on link. The host MUST create 338 one SDAT entry for each of the on-link routers associated with the 339 DHCPv6 assigned address. 341 5.3. Steps involved in detecting link change 343 The steps involved in basic detection of network attachment are: 345 o Link-Layer Indication 347 o Sending of neighbor discovery probes 349 o Response gathering and assessment 351 These steps are described below. 353 5.4. Link-Layer Indication 355 In order to start Detection of network attachment procedures, a host 356 typically requires a link-layer indication that the medium has become 357 available [RFC4957]. 359 After the indication is received, the host MUST mark all currently 360 configured (non-tentative) IP addresses as inoperable until the 361 change detection process completes. It MUST also set all Neighbor 362 Cache entries for the routers on its Default Router List to STALE. 364 This is done to speed up the acquisition of a new default router in 365 case the host attaches to a previously unvisited link. 367 5.5. Sending Neighbor Discovery probes 369 5.5.1. Sending Router Solicitations 371 When a host receives a link-layer "up" indication, it SHOULD 372 immediately send a Router Solicitation (as specified in as specified 373 in section 6.3.7 of [RFC4861]). The Router Solicitation is sent to 374 the All-routers multicast address using a link-local address as the 375 source address [RFC4861]. Even if the host is in possession of more 376 than one valid IPv6 address, it MUST send only one router 377 solicitation using a valid link-local address as the source address. 379 5.5.2. Sending Neighbor Solicitations 381 The host iterates through the SDAT to identify a set of candidate 382 routers for NS based probing. Each router in the SDAT that is 383 associated with at least one valid address is added to the candidate 384 router set exactly once. For each router in the candidate router set 385 the host MUST send an unicast Neighbor Solicitation to the router's 386 link-local address it obtained from the lookup on the SDAT. The host 387 MUST set link-layer destination address in each of these neighbor 388 solicitations to the link-layer address of the router stored in the 389 SDAT. The host MUST NOT send unicast Neighbor Solicitations to a 390 router that is not associated to a valid address in the SDAT. If at 391 least one entry in the SDAT for a given router had the S-Flag set, 392 the host SHOULD use SEND to secure the NS probe being sent to the 393 router. 395 5.5.3. Concurrent sending of RS and NS probes 397 The host SHOULD send the Neighbor Solicitation based unicast probes 398 in parallel with the multicast Router Solicitation. Since sending 399 NSs is just an optimization, doing the NSs and the RS in parallel 400 ensures that the procedure does not run slower than it would if it 401 only used an Router Solicitation. 403 NOTE: A Simple DNA implementation SHOULD limit its NS based probing 404 to at most six previously seen routers 406 5.5.4. Initiating DHCPv6 exchange 408 On receiving a link-layer "up" indication, the host will initiate a 409 DHCPv6 exchange when and as specified in [RFC3315] in order to verify 410 whether the addresses and configuration obtained using DHCPv6 are 411 still usable on the link. Note that DHCPv6, as specified today, only 412 attempts to confirm addresses obtained on the most recently attached 413 link. 415 5.6. Contents of the Neighbor Discovery messages 417 5.6.1. Neighbor Solicitation messages 419 This section describes the contents of the neighbor solicitation 420 probe messages sent during the probing procedure. 422 Source Address: A link-local address assigned to the 423 probing host. 425 Destination Address: The link-local address of the router being 426 probed as learned from the SDAT. 428 Hop Limit: 255 430 ND Options: 432 Target Address: The link-local address of the router being 433 probed as learnt from the SDAT. 435 Link Layer Header: 437 Destination Address: The link-layer (MAC) address of the router 438 being probed as learnt from the SDAT. 440 The probing node SHOULD include the Source link-layer address option 441 in the probe messages. 443 5.6.2. Router Solicitation messages 445 This section describes the contents of the router solicitation probe 446 message sent during the probing procedure. 448 Source Address: A link-local address assigned to the 449 probing host. 451 Destination Address: The all-routers multicast address. 453 Hop Limit: 255 455 The probing node SHOULD NOT include the Source link-layer address 456 option in the probe messages. 458 5.7. Response Gathering 460 5.7.1. Receiving Neighbor Advertisements 462 When a Neighbor Advertisement is received from a router in response 463 to a NS probe, the host MUST verify that both the IPv6 and link layer 464 (MAC) addresses of the router match the expected values before 465 utilizing the configuration associated with the detected network 466 (prefixes, MTU etc.). The host MUST then go through the SDAT and 467 mark the addresses (both SLAAC and DHCPv6 acquired) associated with 468 the router as operable. 470 5.7.2. Receiving Router Advertisements 472 On reception of a Router Advertisement the host MUST go through the 473 SDAT and mark all the addresses associated with the router (both 474 SLAAC and DHCPv6 acquired) as inoperable. The host MUST then process 475 the Router Advertisement as specified in Section 6.3.4. of [RFC4861]. 477 5.7.3. Conflicting results 479 5.7.3.1. Conflicting results between RS and NS probes 481 Where the conclusions obtained from the Neighbor Solicitation/ 482 Advertisement from a given router and the RS/RA exchange with the 483 same router differ, the results obtained from the RS/RA will be 484 considered definitive. In case the Neighbor Advertisement was 485 secured using SEND and the Router Advertisement was not, the host 486 MUST wait for SEND_NA_GRACE_TIME to see if a SEND-secured RA is 487 received. If a SEND-secured RA is not received, the conclusions 488 obtained from the NS/NA exchange will be considered definitive. 490 5.7.3.2. Conflicting results between DHCPv6 and NS probes 492 Where the conclusions obtained from the Neighbor Solicitation/ 493 Advertisement for a given DHCPv6-assigned address and the conclusions 494 obtained from the DHCPv6 exchange differ, the results obtained from 495 the DHCPv6 exchange will be considered definitive. 497 5.8. Further Host Operations 499 Operations subsequent to detecting network attachment depend upon 500 whether or not the host has reconnected to a previously visited 501 network. 503 After confirming the reachability of the associated router using an 504 NS/NA pair, the host performs the following steps. 506 o The host SHOULD rejoin any solicited nodes' multicast groups for 507 addresses it continues to use. 509 o The host SHOULD select a default router as described in Section 510 6.3.6 of [RFC4861]. 512 If the host has determined that it has reattached to a previously 513 visited link, it SHOULD NOT perform duplicate address detection on 514 the addresses that have been confirmed to be operable. 516 If the NS based probe with a router did not complete or if the RS 517 based probe on the same router completed with different prefixes than 518 the ones in the SDAT the host MUST begin address configuration 519 techniques, as indicated in a received Router Advertisement 520 [RFC4861][RFC4862]. 522 5.9. On connecting to a new point of attachment 524 A host usually maintains SDAT entries from some number of previously 525 visited networks. When the host attaches to a previously unknown 526 network it MAY need to discard some older SDAT entries. 528 5.10. Periodic Maintenance of the SDAT 530 The host SHOULD maintain the SDAT table by removing entries when the 531 valid lifetime for the prefix and address expires, that is, at the 532 same as as the prefix is removed from the Prefix List in [RFC4861]. 533 The host SHOULD also remove a router from a SDAT entry when that 534 router stops advertising a particular prefix. When three consequtive 535 RAs from a particular router have not included a prefix, then the 536 router should be removed from the corresponding SDAT entry. 537 Likewise, if a router starts advertising a prefix for which there 538 already exists a SDAT entry then that router should be added to the 539 SDAT entry. 541 5.11. Recommended retransmission behavior 543 Where the NS probe does not complete successfully, it usually implies 544 that the host is not attached to the network whose configuration is 545 being tested. In such circumstances, there is typically little value 546 in aggressively retransmitting unicast neighbor solicitations that do 547 not elicit a response. 549 Where unicast Neighbor Solicitations and Router Solicitations are 550 sent in parallel, one strategy is to forsake retransmission of 551 Neighbor Solicitations and to allow retransmission only of Router 552 Solicitations or DHCPv6. In order to reduce competition between 553 unicast Neighbor Solicitations and Router Solicitations and DHCPv6 554 retransmissions, a DNAv6 implementation that retransmits may utilize 555 the retransmission strategy described in the DHCPv6 specification 556 [RFC3315], scheduling DNAv6 retransmissions between Router 557 Solicitations or DHCPv6 retransmissions. 559 If a response is received to any unicast Neighbor Solicitation, 560 pending retransmissions of the same MUST be canceled. A Simple DNA 561 implementation SHOULD NOT retransmit a Neighbor Solicitation more 562 than twice. To provide damping in the case of spurious Link Up 563 indications, the host SHOULD NOT perform the Simple DNA procedure 564 more than once a second. 566 6. Pseudocode for Simple DNA 568 /* Link up indication received on INTERFACE */ 569 /* Start Simple DNA process */ 571 /* Mark All Addresses as inoperable */ 572 Configured_Address_List=Get_Address_List(INTERFACE); 573 foreach Configured_Address in Configured_Address_List 574 { 575 if (Get_Address_State(Configured_Address)!=AS_TENTATIVE) 576 { 577 Set_Address_State(Configured_Address,AS_INOPERABLE); 578 } 579 } 581 /* Mark all routers' NC entries as STALE to speed up */ 582 /* acquisition of new router if link change has occurred */ 583 foreach Router_Address in DEFAULT_ROUTER_LIST 584 { 585 NCEntry=Get_Neighbor_Cache_Entry(Router_Address); 586 Set_Neighbor_Cache_Entry_State(NCEntry,NCS_STALE); 587 } 589 /* Thread A : Send Router Solicitation */ 590 RS_Target_Address=FF02::2; 591 RS_Source_Address=Get_Any_Link_Local_Address(INTERFACE); 592 Send_Router_Solicitation(RS_Source_Address,RS_Target_Address); 594 /* Thread B : Send Neighbor Solicitation(s) */ 595 Previously_Known_Router_List=Get_Router_List_from_SDAT(); 596 NS_Source_Address=Get_Any_Link_Local_Address(INTERFACE); 598 foreach Router_Address in Previously_Known_Router_List 599 { 600 if (Get_Any_Valid_Address_from_SDAT(Router_Address)) 601 { 602 Send_Neighbor_Solicitation(NS_Source_Address,Router_Address.L3_Address, 603 Router_Address.L2_Address); 604 } 605 } 607 /* Thread C : Response collection of RAs */ 609 /* Received Router Advertisement processing */ 610 /* Only for RAs received from routers in the SDAT */ 612 L3_Source=Get_L3_Source(RECEIVED_MESSAGE); 613 L2_Source=Get_L2_Source(RECEIVED_MESSAGE); 614 SDAT_Entry_List=Get_Entries_from_SDAT_L2L3(L3_Source,L2_Source)); 616 /* Mark all the addresses associated with the router as inoperable */ 617 foreach SDAT_Entry in SDAT_Entry_List 618 { 619 Set_Address_State(SDAT_Entry,AS_INOPERABLE); 620 } 622 /* Ignore further NAs from this router */ 623 /* after delaying for x milliseconds */ 624 Add_Router_to_NA_Ignore_List(L3_Source,SEND_NA_GRACE_PERIOD); 626 /* Perform Standard RA processing as per RFC4861/RFC4862 */ 628 /* Thread D : Response collection of NAs */ 630 /* Received Neighbor Advertisement processing */ 631 /* Only for NAs received as response to DNA NSs */ 633 L3_Source=Get_L3_Source(RECEIVED_MESSAGE); 634 L2_Source=Get_L2_Source(RECEIVED_MESSAGE); 636 if (Is_Router_on_NA_Ignore_List(L3_Source)) { 637 /* Ignore message and wait for next message */ 638 continue; 639 } 641 SDAT_Entry_List=Get_Entries_from_SDAT_L2L3(L3_Source,L2_Source)); 643 foreach SDAT_Entry in SDAT_Entry_List 644 { 645 /* Address is operable. */ 646 Set_Address_State(SDAT_Entry,AS_OPERABLE); 647 /* Configure on Interface */ 648 } 650 Figure 1: Pseudocode for Simple DNA 652 NOTE: This section does not include any pseudo-code for sending of 653 the DHCPv6 packets since the DHCPv6 exchange is orthogonal to the 654 simple DNA process. 656 7. Constants 657 SEND_NA_GRACE_TIME 659 Definition: An optional period to wait after Neighbor 660 Solicitation before adopting a non-SEND RA's link change 661 information. 663 Value: 40 milliseconds 665 8. Relationship to DNAv4 667 DNAv4 [RFC4436] specifies a set of steps that optimize the (common) 668 case of re-attachment to an IPv4 network that one has been connected 669 to previously by attempting to re-use a previous (but still valid) 670 configuration. This document shares the same goal as DNAv4 (that of 671 minimizing the handover latency in moving between points of 672 attachment) but differs in the steps it performs to achieve this 673 goal. Another difference is that this document also supports 674 stateless autoconfiguration of addresses in addition to addresses 675 configured using DHCPv6. 677 9. IANA Considerations 679 There are no changes to IANA registries required in this document. 681 10. Security Considerations 683 A host may receive Router Advertisements from non-SEND devices, after 684 receiving a link-layer indications. While it is necessary to assess 685 quickly whether a host has moved to another network, it is important 686 that the host's current secured SEND [RFC3971] router information is 687 not replaced by an attacker which spoofs an RA and purports to change 688 the link. 690 As such, the host SHOULD send a Neighbor Solicitation to the existing 691 SEND router upon link-up indication as described above in 692 Section 5.4. The host SHOULD then ensure that unsecured router 693 information does not cause deletion of existing SEND state, within 694 MIN_DELAY_BETWEEN_RAS, in order to allow for a present SEND router to 695 respond. 697 If the current default router is a SEND-secured router, the host 698 SHOULD wait SEND_NA_GRACE_TIME after transmission before adopting a 699 new default router. 701 Even if SEND signatures on RAs are used, it may not be immediately 702 clear if the router is authorized to make such advertisements. As 703 such, a host SHOULD NOT treat such devices as secure until and unless 704 authorization delegation discovery is successful. 706 Unless SEND or other form of secure address configuration is used, 707 the DNA procedure does not in itself provide positive, secure 708 authentication of the router(s) on the network, or authentication of 709 the network itself, as e.g. would be provided by mutual 710 authentication at the link layer. Therefore when such assurance is 711 not available, the host MUST NOT make any security-sensitive 712 decisions based on the DNA procedure alone. In particular, it MUST 713 NOT decide that it has moved from an untrusted to a trusted network, 714 and MUST NOT make any security decisions that depend on the 715 determination that such a transition has occurred. 717 11. Acknowledgments 719 This document is the product of a discussion the authors had with 720 Bernard Aboba, Thomas Narten, Erik Nordmark and Dave Thaler at IETF 721 69. The authors would like to thank them for clearly detailing the 722 requirements of the solution and the goals it needed to meet and for 723 helping to explore the solution space. The authors would like to 724 thank the authors and editors of the complete DNA specification for 725 detailing the overall problem space and solutions. The authors would 726 like to thank Jari Arkko for driving the evolution of a simple and 727 probabilistic DNA solution. The authors would like to thank Bernard 728 Aboba, Thomas Narten, Jari Arkko, Sathya Narayan, Julien Laganier, 729 Domagoj Premec, Jin Hyeock-Choi, Alfred Hoenes, Frederic Rossi, Ralph 730 Droms, Ted Lemon, Erik Nordmark, Lars Eggert, Brian Carpenter and 731 Yaron Sheffer for performing reviews on the document and providing 732 valuable comments to drive the document forward. 734 12. References 736 12.1. Normative References 738 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 739 Requirement Levels", BCP 14, RFC 2119, March 1997. 741 [RFC3736] Droms, R., "Stateless Dynamic Host Configuration Protocol 742 (DHCP) Service for IPv6", RFC 3736, April 2004. 744 [RFC3315] Droms, R., Bound, J., Volz, B., Lemon, T., Perkins, C., 745 and M. Carney, "Dynamic Host Configuration Protocol for 746 IPv6 (DHCPv6)", RFC 3315, July 2003. 748 [RFC3971] Arkko, J., Kempf, J., Zill, B., and P. Nikander, "SEcure 749 Neighbor Discovery (SEND)", RFC 3971, March 2005. 751 [RFC4861] Narten, T., Nordmark, E., Simpson, W., and H. Soliman, 752 "Neighbor Discovery for IP version 6 (IPv6)", RFC 4861, 753 September 2007. 755 12.2. Informative References 757 [I-D.ietf-dna-protocol] 758 Narayanan, S., "Detecting Network Attachment in IPv6 759 Networks (DNAv6)", draft-ietf-dna-protocol (work in 760 progress), June 2007. 762 [RFC4957] Krishnan, S., Montavont, N., Njedjou, E., Veerepalli, S., 763 and A. Yegin, "Link-Layer Event Notifications for 764 Detecting Network Attachments", RFC 4957, August 2007. 766 [RFC4862] Thomson, S., Narten, T., and T. Jinmei, "IPv6 Stateless 767 Address Autoconfiguration", RFC 4862, September 2007. 769 [RFC4436] Aboba, B., Carlson, J., and S. Cheshire, "Detecting 770 Network Attachment in IPv4 (DNAv4)", RFC 4436, March 2006. 772 Appendix A. Issues with confirming manually assigned addresses 774 Even though DNAv4 [RFC4436] supports verification of manually 775 assigned addresses this feature of DNAv4 has not been widely 776 implemented or used. There are two major issues that come up with 777 confirming manually assigned addresses using Simple DNA. 779 o When DHCPv6 or SLAAC addresses are used for probing, there is no 780 need to aggressively retransmit lost probes. This is because the 781 address configuration falls back to vanilla DHCPv6 or SLAAC and 782 the host will eventually obtain an address. This is not the case 783 with manually assigned addresses. If the probes are lost, the 784 host runs the risk of ending up with no addresses at all. Hence 785 agressive retransmissions are necessary. 787 o Another issue comes up when the host moves between two networks, 788 one where manual addressing is being used (say NET1)and the other 789 where dynamic addressing (stateless autoconfig or DHCPv6) is being 790 used (say NET2). Since the host can obtain a dynamic address in 791 some situations, it will need to send simple DNA probes and may 792 also engage in a DHCPv6 exchange. In a situation where the host 793 moves to NET1 and the NS probes are lost and in addition an RA is 794 not received, the host will not be able to confirm that it 795 attached to NET1, and therefore that it should use the manual 796 configuration for that network. As a result, if DHCPv6 is enabled 797 on NET1, then the host could mistakenly obtain a dynamic address 798 and configuration instead of using the manual configuration. To 799 prevent this problem, simple DNA probing needs to continue even 800 after the DHCPv6 exchange has completed, and DNA probes need to 801 take precedence over DHCPv6, contrary to the advice provided in 802 Section 5.7.3 804 Given these issues, it is NOT RECOMMENDED to use manual addressing 805 with Simple DNA. 807 Authors' Addresses 809 Suresh Krishnan 810 Ericsson 811 8400 Decarie Blvd. 812 Town of Mount Royal, QC 813 Canada 815 Phone: +1 514 345 7900 x42871 816 Email: suresh.krishnan@ericsson.com 818 Greg Daley 819 NetStar Networks 820 Level 9/636 St Kilda Rd 821 Melbourne, Victoria 3004 822 Australia 824 Phone: +61 3 8532 4042 825 Email: gdaley@netstarnetworks.com