idnits 2.17.1 draft-ietf-dna-simple-07.txt: Checking boilerplate required by RFC 5378 and the IETF Trust (see https://trustee.ietf.org/license-info): ---------------------------------------------------------------------------- ** The document seems to lack a License Notice according IETF Trust Provisions of 28 Dec 2009, Section 6.b.i or Provisions of 12 Sep 2009 Section 6.b -- however, there's a paragraph with a matching beginning. Boilerplate error? (You're using the IETF Trust Provisions' Section 6.b License Notice from 12 Feb 2009 rather than one of the newer Notices. See https://trustee.ietf.org/license-info/.) Checking nits according to https://www.ietf.org/id-info/1id-guidelines.txt: ---------------------------------------------------------------------------- No issues found here. Checking nits according to https://www.ietf.org/id-info/checklist : ---------------------------------------------------------------------------- -- The draft header indicates that this document updates RFC4861, but the abstract doesn't seem to mention this, which it should. Miscellaneous warnings: ---------------------------------------------------------------------------- == The copyright year in the IETF Trust and authors Copyright Line does not match the current year == The document seems to use 'NOT RECOMMENDED' as an RFC 2119 keyword, but does not include the phrase in its RFC 2119 key words list. (Using the creation date from RFC4861, updated by this document, for RFC5378 checks: 2004-07-16) -- The document seems to lack a disclaimer for pre-RFC5378 work, but may have content which was first submitted before 10 November 2008. If you have contacted all the original authors and they are all willing to grant the BCP78 rights to the IETF Trust, then this is fine, and you can ignore this comment. If not, you may need to add the pre-RFC5378 disclaimer. (See the Legal Provisions document at https://trustee.ietf.org/license-info for more information.) -- The document date (July 2, 2009) is 5405 days in the past. 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(See RFCs 3967 and 4897 for information about using normative references to lower-maturity documents in RFCs) == Outdated reference: A later version (-04) exists of draft-ietf-dna-tentative-01 ** Obsolete normative reference: RFC 3315 (Obsoleted by RFC 8415) ** Obsolete normative reference: RFC 3736 (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: January 3, 2010 July 2, 2009 8 Simple procedures for Detecting Network Attachment in IPv6 9 draft-ietf-dna-simple-07 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 January 3, 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 . . . . . . . . . . . . . . . . . . . . . . 3 61 2.3. Link Identification model . . . . . . . . . . . . . . . . 4 62 2.4. DNA Roles . . . . . . . . . . . . . . . . . . . . . . . . 4 63 2.5. Working Assumptions . . . . . . . . . . . . . . . . . . . 4 64 3. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 5 65 4. Host Operations . . . . . . . . . . . . . . . . . . . . . . . 5 66 4.1. Host data structures . . . . . . . . . . . . . . . . . . . 6 67 4.2. Steps involved in detecting link change . . . . . . . . . 6 68 4.3. Link-Layer Indication . . . . . . . . . . . . . . . . . . 6 69 4.4. Sending Neighbor Discovery probes . . . . . . . . . . . . 6 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 . . . . . . . . . . . . . . . . . . 8 74 4.7. Response Gathering . . . . . . . . . . . . . . . . . . . . 9 75 4.8. Further Host Operations . . . . . . . . . . . . . . . . . 10 76 4.9. Recommended retransmission behavior . . . . . . . . . . . 10 77 5. Router Operations . . . . . . . . . . . . . . . . . . . . . . 11 78 5.1. DHCPv6 Router/Server Operations . . . . . . . . . . . . . 12 79 6. Pseudocode for Simple DNA . . . . . . . . . . . . . . . . . . 12 80 7. Constants . . . . . . . . . . . . . . . . . . . . . . . . . . 14 81 8. Relationship to DNAv4 . . . . . . . . . . . . . . . . . . . . 14 82 9. Open Issues . . . . . . . . . . . . . . . . . . . . . . . . . 15 83 10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 15 84 11. Security Considerations . . . . . . . . . . . . . . . . . . . 15 85 12. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 16 86 13. References . . . . . . . . . . . . . . . . . . . . . . . . . . 16 87 13.1. Normative References . . . . . . . . . . . . . . . . . . . 16 88 13.2. Informative References . . . . . . . . . . . . . . . . . . 17 89 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 17 91 1. Requirements notation 93 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 94 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 95 document are to be interpreted as described in [RFC2119]. 97 2. Introduction 99 Hosts require procedures to simply and reliably identify if they have 100 moved to a different IP network to the one which they have been 101 recently connected. In order to detect change, router and neighbour 102 discovery messages are used to collect reachability and configuration 103 information. This information is used to detect whether the existing 104 router and address prefixes are likely to be present. 106 This document incorporates feedback from host and router operating 107 systems implementors, which seeks to make implementation and adoption 108 of IPv6 change detection procedures simple for general use. 110 2.1. Goals 112 The goal of this document is to specify a simple procedure for 113 detecting network attachment (Simple DNA) that has the following 114 characteristics. 116 o Routers do not have to be modified to support this scheme. 118 o Handle only the simplest and most likely use cases. 120 o Work at least as quickly as standard neighbor discovery. 122 o False positives are not acceptable. A host should not conclude 123 that there is no link change when there is one. 125 o False negatives are acceptable. A host can conclude that there is 126 a link change when there is none. 128 2.2. Applicability 130 The Simple DNA protocol provides substantial benefits in some 131 scenarios and does not provide any benefit at all in certain other 132 scenarios. This is intentional as Simple DNA was designed for 133 simplicity rather than completeness. In particular, the Simple DNA 134 protocol provides maximum benefits when a host moves between a small 135 set of known links. When a host moves to a completely new link that 136 is previously unknown, the performance of the Simple DNA protocol 137 will be identical to that using standard neighbor discovery 138 procedures [RFC4861]. 140 2.3. Link Identification model 142 Earlier methods of detecting network attachment, e.g. the procedure 143 defined in [I-D.ietf-dna-protocol], relied on detecting whether the 144 host was still connected to the same link. If the host was attached 145 to the same link, all information related to the link such as the 146 routers, prefixes and configuration parameters was considered to be 147 valid. The Simple DNA protocol follows an alternate approach where 148 it relies on probing each previously known router to determine 149 whether to use information learnt from THAT router. This allows 150 simple DNA to probe routers learnt from multiple earlier attachments 151 to optimize movement between a known set of links. 153 2.4. DNA Roles 155 Detecting Network Attachment is performed by hosts by sending IPv6 156 neighbour discovery and router discovery messages to routers after 157 connecting to a network. 159 It is desirable that routers adopt procedures which allow for fast 160 unicast Router Advertisement (RA) messages. Routers that follow the 161 standard neighbor discovery procedure described in [RFC4861] will 162 delay the router advertisement by a random period between 0 and 163 MAX_RA_DELAY_TIME (defined to be 500ms) as described in Section 6.2.6 164 of [RFC4861]. This delay can be significant and may result in 165 service disruption. Please note that support for fast unicast RAs is 166 not necessary since the simple dna procedure can continue to work 167 using the NS/NA exchange, which will complete earlier than the RA 168 arrives. 170 The host detects that the link-layer may have changed, and then 171 simultaneously probes the network with Router Solicitations (RSs) and 172 Neighbour Solicitations (NSs). The host uses advertisements to 173 determine if the routers it currently has configured are still 174 available. 176 Additionally, on links with no statelessly configured addresses, the 177 host may make use of DHCPv6 procedures to identify an operable 178 address. 180 2.5. Working Assumptions 182 There are a series of assumptions about the network environment which 183 underpin these procedures. 185 o The combination of the link layer address and the link local IPv6 186 address of a router is unique across links. 188 o Hosts receive indications when a link-layer comes up. Without 189 this, they would not know when to commence the DNA procedure. 191 If these assumptions do not hold, host change detection systems will 192 not function optimally. In that case, they may occasionally detect 193 change spuriously, or experience some delay in detecting network 194 attachment. The delays so experienced will be no longer than those 195 caused by following the standard neighbor discovery procedure 196 described in [RFC4861]. 198 If systems do not meet these assumptions or if systems seek 199 deterministic change detection operations they are directed to follow 200 the complete dna procedure as defined in [I-D.ietf-dna-protocol]. 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 neighbour 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 as 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 needs to pick a subset of operable IPv6 286 addresses (candidate set) that it wishes to use. How this subset of 287 addresses is picked is based on host configuration. e.g. The host 288 may select configured addresses from each of zero, one or two 289 previously connected links. If the addresses obtained from a 290 previous router are no longer valid, the host does not include these 291 addresses in the candidate set for NS based probing. 293 For each of the addresses in the candidate set, the host looks up the 294 SDAT to find out the link-local and MAC addresses of the router that 295 advertised the prefix used to form the address. It then sends an 296 unicast Neighbor Solicitations to each router's link-local address it 297 obtained from the lookup on the SDAT. The host SHOULD NOT send 298 unicast Neighbor Solicitations to a test node corresponding to an 299 IPv6 address that is no longer valid. 301 Please note that the Neighbour Solicitations SHOULD be sent in 302 parallel with the Router Solicitations. Since sending NSs is just an 303 optimization, doing the NSs and RSs in parallel ensures that the 304 procedure does not run slower than it would if it only used an RS. 306 Be aware that each unicast solicitation which is not successful may 307 cause packet flooding in bridged networks, if the networks are not 308 properly configured. This is further described in Section 9. Where 309 flooding may cause performance issues within the LAN, host SHOULD 310 limit the number of unicast solicitations. 312 4.5. Contents of the Neighbor Discovery messages 314 4.5.1. Neighbor Solicitation messages 316 This section describes the contents of the neighbor solicitation 317 probe messages sent during the probing procedure. 319 Source Address: A link-local address assigned to the 320 probing host. 322 Destination Address: The link-local address of the router being 323 probed as learnt from the SDAT. 325 Hop Limit: 255 327 ND Options: 329 Target Address: The link-local address of the router being 330 probed as learnt from the SDAT. 332 The probing node SHOULD include a Source link-layer address option in 333 the probe messages. If the node believes that the source address of 334 the NS may not be unique on the newly attached link, it MAY omit the 335 Source link-layer address option in the probe messages. 337 4.5.2. Router Solicitation messages 339 This section describes the contents of the router solicitation probe 340 message sent during the probing procedure. 342 Source Address: A link-local address assigned to the 343 probing host. 345 Destination Address: The all-routers multicast address. 347 Hop Limit: 255 349 The probing node SHOULD NOT include a Source link-layer address 350 option if it has not performed duplicate address detection [RFC4862], 351 for the source address of the NS, on the newly attached link. 353 4.6. Sending DHCPv6 probes 355 Where the host has acquired addresses from DHCPv6 or the host does 356 not have a global prefix, it MAY prefer to use DHCPv6 messages either 357 before or simultanously with Neighbour Discovery probing. 359 In that case, when the host receives a link-layer indication, it 360 sends a DHCPv6 SOLICIT to All_DHCP_Relay_Agents_and_Servers. This 361 message contains an Identity Addociation for either a Temporary 362 Address (IA_TA) or Non-Temporary Address (IA_NA) [RFC3315]. Where an 363 existing valid address is being tested for operability, this address 364 should be placed in the Identity Association's IAADDR element, and 365 the DUID associated with that address should be copied to the DHCP 366 SOLICIT from the SDAT. 368 In order to quickly acquire a new address in the case that link 369 change has occurred, this SOLICIT message MAY contain the Rapid- 370 Commit option. 372 Where the Rapid-Commit option has not been used, a present DHCP 373 server will respond with an ADVERTISE message. The IP address 374 contained in the Identity Association (IA_TA or IA_NA) will contain 375 an IP Address which is operable for the link. 377 Where Rapid-Commit option has been sent, a DHCPv6 server will respond 378 with REPLY. In addition to being operable, this address is allocated 379 to the host for the lease duration indicated in the Identity 380 Association. 382 4.7. Response Gathering 384 When a responding Neighbour Advertisement is received from a test 385 node, the host MUST verify that both the IPv6 and link layer (MAC) 386 addresses of the test node match the expected values before utilizing 387 the configuration associated with the detected network (prefixes, MTU 388 etc.). 390 On reception of a Router Advertisement or advertising DHCPv6 message 391 (a REPLY or ADVERTISE) which contains prefixes that intersect with 392 those previously advertised by a known router, the host utilizes the 393 configuration associated with the detected network. 395 When the host receives an advertisement containing only prefixes 396 which are disjoint from known advertised prefixes, the host MUST 397 determine whether the solicited advertisement corresponds to any of 398 the routers probed via NS. If it does, then the host SHOULD conclude 399 that the IPv6 addresses corresponding to that router are no longer 400 valid. Since any NS probes to that router will no longer provide 401 useful information, further probing of that router SHOULD be aborted. 403 Where the conclusions obtained from the Neighbor Solicitation/ 404 Advertisement from a given router and the RS/RA exchange with the 405 same router differ, the results obtained from the RS/RA will be 406 considered definitive. 408 When the host receives a Router Advertisement in reply to the Router 409 Solicitation it sent, the host SHOULD look for a Neighbor Cache entry 410 for the sending router and SHOULD mark that router's Neighbor Cache 411 Entry as REACHABLE if one was found. The host SHOULD add a new 412 Neighbor Cache Entry in the REACHABLE state for the sending router if 413 one does not currently exist. 415 4.8. Further Host Operations 417 Operations subsequent to detecting network attachment depend upon 418 whether change was detected. 420 After confirming the reachability of the associated router using an 421 NS/NA pair, the host performs the following steps. 423 o The host SHOULD rejoin any solicited nodes' multicast groups for 424 addresses it continues to use. 426 o The host SHOULD select a default router as described in [RFC4861]. 428 If the host has determined that there has been no link change, it 429 SHOULD NOT perform duplicate address detection on the addresses that 430 have been confirmed to be operable. 432 If the NS based probe with a router did not complete or if the RS 433 based probe on the same router completed with different prefixes than 434 the ones in the SDAT the host MUST unconfigure all the existing 435 addresses received from the given router, and MUST begin address 436 configuration techniques, as indicated in the received Router 437 Advertisement [RFC4861][RFC4862]. 439 4.9. Recommended retransmission behavior 441 In situations where Neighbor Solicitation probes and Router 442 Solicitation probes are used on the same link, it is possible that 443 the NS probe will complete successfully, and then the RS probe will 444 complete later with a different result. If this happens, the 445 implementation SHOULD abandon the results obtained from the NS probe 446 of the router that responded to the RS and the implementation SHOULD 447 behave as if the NS probe did not successfully complete. If the 448 confirmed address was assigned manually, the implementation SHOULD 449 NOT unconfigure the manually assigned address and SHOULD log an error 450 about the mismatching prefix. 452 Where the NS probe does not complete successfully, it usually implies 453 that the host is not attached to the network whose configuration is 454 being tested. In such circumstances, there is typically little value 455 in aggressively retransmitting unicast neighbor solicitations that do 456 not elicit a response. 458 Where unicast Neighbor Solicitations and Router Solicitations are 459 sent in parallel, one strategy is to forsake retransmission of 460 Neighbor Solicitations and to allow retransmission only of Router 461 Solicitations or DHCPv6. In order to reduce competition between 462 unicast Neighbor Solicitations and Router Solicitations and DHCPv6 463 retransmissions, a DNAv6 implementation that retransmits may utilize 464 the retransmission strategy described in the DHCPv6 specification 465 [RFC3315], scheduling DNAv6 retransmissions between Router 466 Solicitation or DHCPv6 retransmissions. 468 If a response is received to any unicast Neighbor Solicitation, 469 Router Solicitation or DHCPv6 message, pending retransmissions MUST 470 be canceled [RFC3315][RFC3736]. A Simple DNA implementation SHOULD 471 NOT retransmit a Neighbor Solicitation more than twice. To provide 472 damping in the case of spurious Link Up indications, the host SHOULD 473 NOT perform the Simple DNA procedure more than once a second. 475 5. Router Operations 477 Hosts checking their network attachment are unsure of their address 478 status, and may be using Tentative link-layer addressing information 479 in their router or neighbour solicitations. 481 A router which desires to support hosts' DNA operations MUST process 482 Tentative Options from unicast source addressed Router and Neighbour 483 Solicitations, as described in [I-D.ietf-dna-tentative]. 485 5.1. DHCPv6 Router/Server Operations 487 DHCPv6 Server operations occur in accordance with the DHCPv6 RFC 488 [RFC3315]. 490 6. Pseudocode for Simple DNA 492 /* Link up indication received on INTERFACE */ 493 /* Start Simple DNA process */ 495 /* Mark All Addresses as deprecated */ 496 Configured_Address_List=Get_Address_List(INTERFACE); 497 foreach Configured_Address in Configured_Address_List 498 { 499 if (Get_Address_State(Configured_Address)!=AS_TENTATIVE) 500 { 501 Set_Address_State(Configured_Address,AS_DEPRECATED); 502 } 503 } 505 /* Mark all routers' NC entries as STALE to speed up */ 506 /* acquisition of new router if link change has occurred */ 507 foreach Router_Address in DEFAULT_ROUTER_LIST 508 { 509 NCEntry=Get_Neighbor_Cache_Entry(Router_Address); 510 Set_Neighbor_Cache_Entry_State(NCEntry,NCS_STALE); 511 } 513 /* Thread A : Send Router Solicitation */ 514 RS_Target_Address=FF02::2; 515 RS_Source_Address=Get_Any_Link_Local_Address(INTERFACE); 516 Send_Router_Solicitation(RS_Source_Address,RS_Target_Address); 518 /* Thread B : Send Neighbor Solicitation(s) */ 519 Previously_Known_Router_List=Get_Router_List_from_SDAT(); 520 NS_Source_Address=Get_Any_Link_Local_Address(INTERFACE); 522 foreach Router_Address in Previously_Known_Router_List 523 { 524 if (Get_Any_Valid_Address_from_SDAT(Router_Address)) 525 { 526 Send_Neighbor_Solicitation(NS_Source_Address,Router_Address); 527 } 528 } 530 /* 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)); 538 foreach SDAT_Entry in SDAT_Entry_List 539 { 540 if (Exists_PIO(RECEIVED_MESSAGE,Get_Prefix(SDAT_Entry))) 541 { 542 /* Address is operable. Configure on Interface */ 543 /* Rejoin solicited-node multicast group for address */ 544 } 545 else 546 { 547 /* If address is configured on interface, remove it */ 548 /* This could be because of a NA arriving before RA */ 549 } 550 } 552 /* Mark router as reachable */ 553 NCEntry=Get_Neighbor_Cache_Entry(L3_Source); 554 if (NCEntry is not NULL) 555 { 556 Set_Neighbor_Cache_Entry_State(NCEntry,NCS_REACHABLE); 557 } 558 else 559 { 560 Create_Neighbor_Cache_Entry(L3_Source,NCS_REACHABLE); 561 } 563 /* Ignore further NAs from this router */ 564 Add_Router_to_NA_Ignore_List(L3_Source); 566 /* Received Neighbor Advertisement processing */ 567 /* Only for NAs received as response to DNA NSs */ 569 L3_Source=Get_L3_Source(RECEIVED_MESSAGE); 570 L2_Source=Get_L2_Source(RECEIVED_MESSAGE); 572 if (Is_Router_on_NA_Ignore_List(L3_Source)) { 573 /* Ignore message and wait for next message */ 574 continue; 575 } 577 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 7. Constants 587 These constants are described as in [I-D.ietf-dna-protocol]. 589 UNICAST_RA_INTERVAL 591 Definition: The interval corresponding to the maximum average 592 rate of Router Solicitations that the router is prepared to 593 service with unicast responses. This is the interval at which 594 the token bucket controlling the unicast responses is 595 replenished. 597 Value: 50 milliseconds 599 MAX_UNICAST_RA_BURST 601 Definition: The maximum size burst of Router Solicitations that 602 the router is prepared to service with unicast responses. This 603 is the maximum number of tokens allowed in the token bucket 604 controlling the unicast responses. 606 Value: 20 608 SEND_NA_GRACE_TIME 610 Definition: An optional period to wait after Neighbour 611 Solicitation before adopting a non-SEND RA's link change 612 information. 614 Value: 40 milliseconds 616 8. Relationship to DNAv4 618 DNAv4 [RFC4436] specifies a set of steps that optimize the (common) 619 case of re-attachment to an IPv4 network that one has been connected 620 to previously by attempting to re-use a previous (but still valid) 621 configuration. This document shares the same goal as DNAv4 (that of 622 minimizing the handover latency in moving between points of 623 attachment) but differs in the steps it performs to achieve this 624 goal. Another difference is that this document also supports 625 stateless autoconfiguration of addresses in addition to addresses 626 configured using DHCPv6. 628 9. Open Issues 630 This section documents issues that are still outstanding within the 631 document, and the simple DNA solution in general. 633 Rate limitation for solicitations. 635 Hosts MAY implement hysteresis mechanisms to pace solicitations 636 where necessary to prevent damage to a particular medium. 637 Implementors should be aware that when such hysteresis is 638 triggered, Detecting Network Attachment may be slowed, which may 639 affect application traffic. 641 10. IANA Considerations 643 There are no changes to IANA registries required in this document. 645 11. Security Considerations 647 When providing fast responses to router solicitations, it is possible 648 to cause collisions with other signaling packets on contention based 649 media. This can cause repeated packet loss or delay when multiple 650 routers are present on the link. 652 As such the fast router advertisement system is NOT RECOMMENDED in 653 this form for media which are susceptible to collision loss. Such 654 environments may be better served using the procedures defined in 655 [I-D.ietf-dna-protocol]. 657 A host may receive Router Advertisements from non SEND devices, after 658 receiving a link-layer indications. While it is necessary to assess 659 quickly whether a host has moved to another network, it is important 660 that the host's current secured SEND [RFC3971] router information is 661 not replaced by an attacker which spoofs an RA and purports to change 662 the link. 664 As such, the host SHOULD send a Neighbour Solicitation to the 665 existing SEND router upon link-up indication as described above in 666 Section 4.3. The host SHOULD then ensure that unsecured router 667 information does not cause deletion of existing SEND state, within 668 MIN_DELAY_BETWEEN_RAS, in order to allow for a present SEND router to 669 respond. 671 The host MAY delay SEND_NA_GRACE_TIME after transmission before 672 adopting a new default router, if it is operating on a network where 673 there is significant threat of RA spoofing. 675 Even if SEND signatures on RAs are used, it may not be immediately 676 clear if the router is authorized to make such advertisements. As 677 such, a host SHOULD NOT treat such devices as secure until and unless 678 authorization delegation discovery is successful. 680 It is easy for hosts soliciting without SEND to deplete a SEND 681 router's fast advertisement token buckets, and consume additional 682 bandwidth. As such, a router MAY choose to preserve a portion of 683 their token bucket to serve solicitations with SEND signatures. 685 12. Acknowledgments 687 This document is the product of a discussion between the authors had 688 with Bernard Aboba, Thomas Narten, Erik Nordmark and Dave Thaler at 689 IETF 69. The authors would like to thank them for clearly detailing 690 the requirements of the solution and the goals it needed to meet and 691 for helping to explore the solution space. The authors would like to 692 thank the authors and editors of the complete DNA specification for 693 detailing the overall problem space and solutions. The authors would 694 like to thank Jari Arkko for driving the evolution of a simple and 695 probabilistic DNA solution. The authors would like to thank Bernard 696 Aboba, Thomas Narten, Sathya Narayan, Julien Laganier, Domagoj 697 Premec, Jin Hyeock-Choi, Alfred Hoenes and Frederic Rossi for 698 performing reviews on the document and providing valuable comments to 699 drive the document forward. 701 13. References 703 13.1. Normative References 705 [I-D.ietf-dna-tentative] 706 Daley, G., Nordmark, E., and N. Moore, "Tentative Options 707 for IPv6 Neighbour Discovery", draft-ietf-dna-tentative-01 708 (work in progress), July 2007. 710 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 711 Requirement Levels", BCP 14, RFC 2119, March 1997. 713 [RFC3315] Droms, R., Bound, J., Volz, B., Lemon, T., Perkins, C., 714 and M. Carney, "Dynamic Host Configuration Protocol for 715 IPv6 (DHCPv6)", RFC 3315, July 2003. 717 [RFC3736] Droms, R., "Stateless Dynamic Host Configuration Protocol 718 (DHCP) Service for IPv6", RFC 3736, April 2004. 720 [RFC3971] Arkko, J., Kempf, J., Zill, B., and P. Nikander, "SEcure 721 Neighbor Discovery (SEND)", RFC 3971, March 2005. 723 [RFC4861] Narten, T., Nordmark, E., Simpson, W., and H. Soliman, 724 "Neighbor Discovery for IP version 6 (IPv6)", RFC 4861, 725 September 2007. 727 13.2. Informative References 729 [I-D.ietf-dna-protocol] 730 Narayanan, S., "Detecting Network Attachment in IPv6 731 Networks (DNAv6)", draft-ietf-dna-protocol (work in 732 progress), June 2007. 734 [RFC4957] Krishnan, S., Montavont, N., Njedjou, E., Veerepalli, S., 735 and A. Yegin, "Link-Layer Event Notifications for 736 Detecting Network Attachments", RFC 4957, August 2007. 738 [RFC4862] Thomson, S., Narten, T., and T. Jinmei, "IPv6 Stateless 739 Address Autoconfiguration", RFC 4862, September 2007. 741 [RFC4436] Aboba, B., Carlson, J., and S. Cheshire, "Detecting 742 Network Attachment in IPv4 (DNAv4)", RFC 4436, March 2006. 744 Authors' Addresses 746 Suresh Krishnan 747 Ericsson 748 8400 Decarie Blvd. 749 Town of Mount Royal, QC 750 Canada 752 Phone: +1 514 345 7900 x42871 753 Email: suresh.krishnan@ericsson.com 754 Greg Daley 755 NetStar Networks 756 Level 9/636 St Kilda Rd 757 Melbourne, Victoria 3004 758 Australia 760 Phone: +61 3 8532 4042 761 Email: gdaley@netstarnetworks.com