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Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Network Working Group DY Kim 3 Internet-Draft Independent 4 Intended status: Experimental March 3, 2019 5 Expires: September 4, 2019 7 Subnet ID Deprecation for IPv6 8 draft-dykim-6man-sid6-01 10 Abstract 12 Deprecation of the subnet ID in IPv6 networking is proposed; the 13 subnet ID is set to zero so that all nodes in a site carry the same 14 prefix. While the procedures for neighbor discovery and duplicate 15 address detection have to be changed, possible simplification gains 16 in IPv6 networking including that of intra-site host- and subnet- 17 mobility might be worth the modification. Site-external behaviors 18 don't change through this modification, enabling incremental 19 deployment of the proposal. Sites of manageable sizes for which 20 scalability is not much a critical issue might consider the mode of 21 operation proposed in this document. 23 Status of This Memo 25 This Internet-Draft is submitted in full conformance with the 26 provisions of BCP 78 and BCP 79. 28 Internet-Drafts are working documents of the Internet Engineering 29 Task Force (IETF). Note that other groups may also distribute 30 working documents as Internet-Drafts. The list of current Internet- 31 Drafts is at https://datatracker.ietf.org/drafts/current/. 33 Internet-Drafts are draft documents valid for a maximum of six months 34 and may be updated, replaced, or obsoleted by other documents at any 35 time. It is inappropriate to use Internet-Drafts as reference 36 material or to cite them other than as "work in progress." 38 This Internet-Draft will expire on September 4, 2019. 40 Copyright Notice 42 Copyright (c) 2019 IETF Trust and the persons identified as the 43 document authors. All rights reserved. 45 This document is subject to BCP 78 and the IETF Trust's Legal 46 Provisions Relating to IETF Documents 47 (https://trustee.ietf.org/license-info) in effect on the date of 48 publication of this document. Please review these documents 49 carefully, as they describe your rights and restrictions with respect 50 to this document. Code Components extracted from this document must 51 include Simplified BSD License text as described in Section 4.e of 52 the Trust Legal Provisions and are provided without warranty as 53 described in the Simplified BSD License. 55 Table of Contents 57 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 58 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3 59 3. SID6 Construction . . . . . . . . . . . . . . . . . . . . . . 3 60 3.1. IPv6 Address . . . . . . . . . . . . . . . . . . . . . . 4 61 3.2. Neighbor Discovery . . . . . . . . . . . . . . . . . . . 5 62 3.3. Duplicate Address Detection . . . . . . . . . . . . . . . 7 63 3.4. Interior Gateway Protocols . . . . . . . . . . . . . . . 8 64 3.5. Other Address-Related Protocols . . . . . . . . . . . . . 8 65 3.6. Generalization . . . . . . . . . . . . . . . . . . . . . 8 66 4. Consequencies . . . . . . . . . . . . . . . . . . . . . . . . 9 67 4.1. No Locator/ID Separation . . . . . . . . . . . . . . . . 9 68 4.2. Inherent Interior Mobility . . . . . . . . . . . . . . . 10 69 4.3. Faster Interior Mobility . . . . . . . . . . . . . . . . 10 70 4.4. Legacy Exterior Mobility . . . . . . . . . . . . . . . . 11 71 4.5. Legacy Migration and Multihoming . . . . . . . . . . . . 11 72 4.6. Incremental Deployability . . . . . . . . . . . . . . . . 12 73 4.7. Prefix Aggregation and Scalability . . . . . . . . . . . 12 74 4.8. Incentives for Deployment . . . . . . . . . . . . . . . . 12 75 5. Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . 12 76 6. Security Considerations . . . . . . . . . . . . . . . . . . . 13 77 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 14 78 8. References . . . . . . . . . . . . . . . . . . . . . . . . . 14 79 8.1. Normative References . . . . . . . . . . . . . . . . . . 14 80 8.2. Informartive References . . . . . . . . . . . . . . . . . 16 81 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 16 83 1. Introduction 85 The idea of IPv4 subnet has been imported intact into IPv6 networking 86 so that each subnet (link) in an IPv6 site is assigned a separate 87 subnet ID (SID). As a result, the IPv6 host has to change the link 88 prefix every time it moves from one link to another even within the 89 same site or routing domain; you have to install MIPv6 agents [MIPv6] 90 on every intra-site router and a MIP6 client on every mobile node in 91 order to provide intra-site node mobility. It might be challenged 92 whether this legacy way of IPv6 operation should continue to be the 93 best way in networking environments ever evolving to a form vastly 94 different from that of the past. 96 For one thing, scalability, one of the main reasons for subnetting, 97 might bear different implications from the past. Moor's Law has 98 continued to be relevant for decades since the time IPv6 was first 99 conceived, and cost or performance concerns for memories and 100 processors have been dramatically relaxed. There might be many 101 potential network administrators who would consider to weigh the 102 burden of managing SIDs and the associated MIPv6 infrastructure 103 against that of inherent mobility support by link-state routing. 105 This document proposes to change the operation of IPv6 networking by 106 deprecating the SID. That is, the value of SID shall be set to zero. 107 This results in all intra-site nodes carrying the same prefix and the 108 mobile nodes keeping the same address as long as the mobility is 109 confined within a given site. 111 A number of operational efficiency might result from this change. 112 The price to pay might be some changes in the procedures for neighbor 113 discovery (ND) and duplicate address detection (DAD). This document 114 presents how this new operational paradigm, to be abbreviated as 115 SID6, could be constructed and discusses possible impacts from this 116 change. 118 It is to be noted that this document limits its SID6 discussions to 119 the case of a site consisting of a single routing area; there are no 120 Level 2 routers in the site under discussion. The multi-area case is 121 left for further study. 123 2. Terminology 125 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 126 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 127 document are to be interpreted as described in [KEYWORDS]. 129 This document introduces the following terminology. 131 DA: Duplicate Advertisement. A unicast message, back to the source 132 address of the previous DS message received, to report the duplicity 133 of the target address in the DS message. 135 DS: Duplicate Solicitation. A site-wide multicast message to solicit 136 the response from a node in possession of the same address as the 137 target address in this message. 139 3. SID6 Construction 140 3.1. IPv6 Address 142 The IPv6 address type of interest is the Global Unicast address (GUA) 143 which contains the SID and interface ID (IID) [v6ADDR]: 145 IPv6 GUA 147 = (interface address) 149 = (subnet prefix, IID) 151 = (global routing prefix, SID, IID) 153 Now, we reset the SID, and the IPv6 GUA will no longer depend on the 154 SID; it doesn't change as a node moves across subnets (links) within 155 a site: 157 IPv6 GUA 159 = (interface address) 161 = (subnet prefix, IID) 163 = (global routing prefix, null, IID) 165 Furthermore, we change the use of the IID as the node ID (NID). That 166 is, each node is associated with an NID unique within a site. When a 167 node has multiple interfaces, there would be multiple IIDs 168 associated. In that case, we enforce all IIDs to be the same, thus 169 ensuring a unique NID per node. The result is: 171 IPv6 GUA 173 = (node address) 175 = (subnet prefix, NID) 177 = (global routing prefix, null, NID) 179 This unique NID is invariant within a site or routing domain. The 180 address is now a node address, not an interface address. 182 When a site is multihomed on multiple upstream networks, it would be 183 associated with multiple site prefixes and hence every intra-site 184 node would be associated with multiple addresses. For seamless site- 185 multihoming in such an instance, a node should be able to receive 186 inbound packets destined to any of its multiple addresses, and also 187 be able to source outbound packets with one of such multiple 188 addresses as appropriate [DASv6]. 190 Remember all we do here is to reset the SID. And that, it is not any 191 change in the definition of the IPv6 address format, but is just an 192 operational choice. All other effects are natural corollaries 193 thereof; the basic IPv6 mechanisms remain the same. We will 194 subsequently see how other parts of the IPv6 networking continue to 195 work correctly as usual, with minimal modifications where necessary. 197 3.2. Neighbor Discovery 199 Addresses involved in ICMPv6-derived [ICMPv6] ND messages [NDv6] are 200 either All-Nodes multicast addresses (FF02:0:0:0:0:0:0:1) or All- 201 Routers multicast addresses (FF02:0:0:0:0:0:0:2), both of which being 202 agnostic to SID. Otherwise, the involved addresses are unicast or 203 anycast addresses which are not anymore dependent on SID as 204 prescribed by SID6. The resulting link prefixes (global routing 205 prefix + null) advertised by all routers within a site are the same, 206 except for the inter-router point-to-point links [p2p127]. Although 207 substantially simplifying router configuration in regard to prefix 208 loading, this SID deprecation necessitates a change in on-link 209 determination. The original ND [NDv6] specifies that an address is 210 considered to be on-link if: 212 1. it is covered by one of the link's prefixes (e.g., as indicated 213 by the on-link flag in the Prefix Information option), or 215 2. a neighboring router specifies the address as the target of a 216 Redirect message. 218 3. a (solicited) Neighbor Advertisement message is received for the 219 (target) address, or 221 4. any ND message is received from the address. 223 The latter two, however, have been deprecated by [v6SUBNET]. 225 Criterion 2 should continue to be valid in SID6. However, Criterion 226 1 is of no more use since all links share the same prefix(es) 227 throughout the site, except for the inter-router point-to-point links 228 [p2p127]. Hence, a prefix with the on-link flag set is not a 229 guarantee that a neighbor address with the very prefix is on-link. 231 Since on-link determination cannot be done through prefixes provided 232 by a pair procedure of Router Solicitation (RS) and Router 233 Advertisement (RA), some other means has to be secured. We propose 234 to use the Reachability test for the purpose and thus to accommodate 235 the following procedure to the ND protocol for on-link determination: 237 o When a node is first injected into a site and attaches to a link, 238 it might acquire the prefix information through a pair of RS and 239 RA, and auto-configure itself with a node address sanitary-checked 240 through DAD described in Section 3.3. If the node comes from a 241 different link in the same site, these steps should be skipped. 243 o It then multicasts an unsolicited Neighbor Advertisement (NA) to 244 the link-local All-Nodes address, FF02:0:0:0:0:0:0:1, to 245 explicitly notify all other nodes on the same link of its 246 emergence. The source address of this NA SHALL be the node 247 address of the new node, and its link-layer address SHALL also be 248 included as an option. In addition, a new option SHALL be 249 incorporated to indicate that every recipient of this unsolicited 250 NA SHOULD return a unicast NS back to the sender. Since NA 251 transmission is unreliable, it can be repeated 252 MAX_NEIGHBOR_ADVERTISEMENT times [NDv6] . The first NA SHOULD be 253 issued after a random delay between 0 and 254 MAX_RTR_SOLICITATION_DELAY [NDv6] to avoid race condition among 255 multiple newly emerging nodes. 257 o On receipt of this unsolicited NA, other nodes on the link SHOULD 258 return Neighbor Solicitation (NS) back to the new node. In this 259 action, issuing of each NS SHOULD be random delayed to avoid race 260 condition. Also, the link-layer address of the responding node 261 SHALL be included in each NS. Duplicate NAs received through 262 retransmission SHALL be silently ignored. 264 o Successful receipt of such a returning NS confirms the forward 265 reachability from the new node's perspective; the responding 266 address is declared to be on-link. The new node creates an entry 267 for the responding address in Neighbor Cache, with the on-link 268 flag set. This is done for each responding address. 270 o For each of such returning NSs, the new node unicasts an NA to the 271 responding address. Successful receipt of this NA by each 272 responding node confirms reachability from the responding node's 273 perspective; the address of the new node is on-link. The 274 responding node then creates an on-link entry for the new node's 275 address in its own Neighbor Cache. 277 o Addresses in Neighbor Cache of a node acquired only through this 278 procedure SHOULD be considered and flagged as on-link. 280 This new procedure differs from the existing ND procedure in that on- 281 link determination is made not through Prefix List (for prefixes with 282 on-link flag set) but through Reachability tests between neighbors. 283 The role of Prefix List reduces simply to providing the common 284 prefix(es) for the given site. Another difference is in regard to 285 the semantics of the source address for NA and NS; whereas it is the 286 sender's interface address in the original ND, it is its node address 287 in SID6. 289 With the introduction of this revised procedure for on-link 290 determination, it follows that Criterion 3 of the original on-link 291 determination SHOULD be revived: 293 When a solicited NA message is received for the target address, 294 the address is confirmed to be on-link. 296 Criterion 4 remains deprecated. 298 3.3. Duplicate Address Detection 300 DAD per IPv6 Stateless Address Autoconfiguration (SLAAC) is done for 301 all unicast addresses by use of a pair of link-local ND messages, 302 namely, NS and NA [SLAAC]. NSs are musticast to link-local 303 Solicited-Node address [v6ADDR]: 305 link-local Solicited-Node address: FF02:0:0:0:0:1:FFXX:XXXX 307 In SID6, however, DAD should be done site-wide, and hence new site- 308 local messages should be introduced to do the job. 310 We name the new pair of ICMPv6 messages as Duplicate Solicitation 311 (DS) and Duplicate Advertisement (DA). Also, we introduce a new type 312 of multicast address named site-local Solicited-Node address defined 313 in a way similar to the (link-local) Solicited-Node multicast address 314 [v6ADDR]: 316 site-local Solicited-Node address: FF05:0:0:0:0:1:FFXX:XXXX 318 A site-local Solicited-Node address is formed by taking the low-order 319 24 bits of an (unicast or anycast) address and appending those bits 320 to the prefix FF05:0:0:0:0:1:FF00::/104 resulting in a multicast 321 address in the range 323 FF05:0:0:0:0:1:FF00:0000 ~ FF05:0:0:0:0:1:FFFF:FFFF 325 A DS is multicast to a site-local Solicited-Node address formed with 326 the unicast or anycast address of the target node. If the target 327 address of the returning DA is tentative, it is an indication that 328 the address is a duplicate. Both nodes SHOULD then refresh their 329 addresses and repeat DAD until no duplicates are observed. An 330 address is considered site-unique if none of the tests equivalent to 331 the ones in Sec. 5.4 of [SLAAC] indicate the presence of a duplicate 332 address within RetransTimer milliseconds after having sent 333 DupAddrDetectTransmits DSs. A natural corollary of this site-wide 334 DAD is that uniqueness of the NID(s) is confirmed site-wide. 336 3.4. Interior Gateway Protocols 338 A link-state Interior Gateway Protocols (IGP) is to be used in SID6; 339 OSPFv3 [OSPFv3] or IS-IS for IPv6 [ISISv6][ISISv4]. The most 340 important impact of SID6 on these link-state routing protocols is the 341 way routers locate the hosts; they are not anymore locatable by link 342 prefixes. 344 In SID6 operation of OSPFv3, host routes are to be included in intra- 345 area-prefix-LSAs. For each of these host routes, the PrefixOptions 346 LA-bit SHOULD be set and the PrefixLength SHOULD be set to a host 347 PrefixLength; see Sec. 4.4.3.9 of [OSPFv3]. In SID6 operation of IS- 348 IS for IPv6, host routes are to be included in the IPv6 Reachability 349 entries, and will be handled in the same way as other IPv6 350 Reachability entries [ISISv6][ISISv4]. 352 It is to be noted that SID6 of this document focuses on a single-area 353 operation in a site. The multi-area case is left for further study. 355 3.5. Other Address-Related Protocols 357 DHCPv6 [DHCPv6] is not affected since most addresses involved there 358 are link-local. The site-local All_DHCP_Servers multicast address in 359 the case of Relay Agent is also intact for correct operation. 361 Default Address Selection [DASv6] is not affected, either. One thing 362 to note is in regard to the scope comparison in selecting a source 363 address for a multicast destination address; see Sec. 3.1 of [DASv6]. 364 The scope of the node address as defined in SID6 is global as well as 365 site. Hence, the same source node address would be selected for a 366 multicast destination address of site scope as well as of global 367 scope as appropriate. 369 No other IPv6-address related protocols are affected, to the best 370 knowledge of the author. 372 3.6. Generalization 374 The description of SID6 so far has been based on nullifying the SID. 375 Alternatively, the same field can be used in a way similar to Unique 376 IPv6 Prefix Per Host [Uv6pH]. The field originally occupied by SID 377 can be populated by random numbers to render intra-site local 378 prefixes. Each node in the site is then assigned a unique (global || 379 local) prefix: 381 IPv6 GUA 383 = (node address) 385 = (prefix, NID) 387 = (global prefix, local prefix, NID) 389 How to use this local prefix is up to the discretion of each node. 390 If a node is a host, it can generate a 128-bit address by use of the 391 combined (global || local) prefix and SLAAC as described in [Uv6pH]. 392 If a node is a router, it is in fact the border router of a child 393 site wherein all internal nodes share the same specific unique 394 (global || local) prefix given to the router. 396 It is to be noted that, although SID is not there anymore, subnets do 397 exist. The only difference is that, with SID6, a subnet is not 398 identified by its SID but by the NID of the Default Router (DR). DR 399 keeps, in its Neighbor Cache, the list of intra-subnet (on-link) 400 hosts for relaying packets in and out across the subnet boundary. 401 There may, of course, be multiple routers associated with the same 402 subnet, and one of them would act as DR as usual. 404 As a result of the described generalization, the architecture of SID6 405 could be summarized as follows: 407 o A site is a collection of (virtual) nodes wherein all nodes share 408 the same prefix. 410 o A subset of directly connected intra-site nodes bordered by one or 411 more router(s) is called a subnet. Thus, a site can also be 412 defined as a collection of subnets. Each subnet is identified by 413 the NID of DR. 415 o Intra-site mobility is provided by a link-state routing protocol, 416 whereas inter-site mobility is by MIPv6 agents installed on one or 417 more site border router(s). 419 4. Consequencies 421 4.1. No Locator/ID Separation 423 SID6 does not introduce a separate number space extra to that already 424 existing IPv6 address space; no locator/ID separation (LIS) is 425 pursued. Within a site, the NID identifies a node whose locality is 426 determined through an interior link-state routing protocol. Between 427 sites, the site prefix both identifies and locates a site. 429 4.2. Inherent Interior Mobility 431 The most important consequence of SID6 is that the node address is 432 invariant across links as long as the node resides within a given 433 site. Since the node address is used for transport connections, the 434 latter do not break while nodes move around within a site. That is, 435 intra-site node mobility is inherently provided. Locating a given 436 node is done through a normal link-state routing protocol like OSPFv3 437 or IS-IS for IPv6. No extra locators are incorporated in SID6. 439 When a given node is a router, node mobility essentially means subnet 440 mobility. A whole subnet, along with the router(s) and attached 441 hosts, can move around within a site without losing reachability and 442 transport connections. Instantaneous event-driven link-state updates 443 will keep tight track of the moving subnet and its associated nodes. 445 A following consequence is that no Mobile IP protocol like MIPv6 446 [MIPv6] is necessary for intra-site mobile nodes. A MIPv6 client 447 would be enabled only when a node visits a foreign site, and MIPv6 448 agents need be installed only on site border routers, not on every 449 intra-site routers. This simplification may stand for a substantial 450 resource saving in providing intra-site mobility. 452 4.3. Faster Interior Mobility 454 Now a valid question might be whether the intra-site mobility 455 provided by link-state routing protocols should be faster or slower 456 than that provided by MIPv6-installed intra-site routers. First of 457 all, movement detection by a mobile node should be the same for both 458 cases; any of link-layer indication, DR not reachable, or a new 459 prefix heard from RA, etc.; see Sec. 11.5.1 of [MIPv6]. Differences, 460 if any, should be with the actions taken thereafter. Typical actions 461 by a mobile node after movement detection, in accordance with MIPv6, 462 should be: 464 1. Send RS (if no RA heard) 466 2. Receive RA 468 3. Create addresses including care-of-address 470 4. DAD for all unicast addresses 472 5. Register care-of-address with Home Agent (HA) 473 Since the prefix acquired in Step 2 should be the same as the one 474 already installed on the SID6 mobile node, Step 3 is to be skipped in 475 SID6. Step 4 is not necessary, either, since uniqueness of the 476 NID(s) has already been guaranteed by a previous site-wide DAD before 477 the move, in accordance with the new DAD procedure introduced in 478 Section 3.3. Saving a DAD could be substantial since it would 479 involve a number of message exchanges appended by possible 480 retransmissions. 482 As for the last step, registering with a MIPv6 HA may consume several 483 Binding message exchanges. In the case of SID6, the modified ND 484 procedure described in Section 3.2 would be executed, which would 485 then be immediately followed by DR flooding an event-driven link- 486 state update to inform all other intra-site routers of the successful 487 arrival of the visiting mobile node. Time lapses caused by the two 488 schemes could be considered approximately equal. 490 As a result, the time saving in SID6 should be what the address 491 creation and a DAD would consume. Thus, the intra-site mobility 492 provided by SID6 should be faster by as much than that by MIPv6. 493 This faster mobility would be an advantage in many disruptive 494 applications wherein nodes might experience frequent changes in link 495 attachment. 497 4.4. Legacy Exterior Mobility 499 Exterior mobility would be done through MIPv6 as usual. MIPv6 agents 500 need be installed only on site border routers. 502 4.5. Legacy Migration and Multihoming 504 Renumbering at migration can be done seamlessly as usual. The site 505 would first be multihomed on the old as well as the new upstream 506 networks. Once all nodes are successfully renumbered and 507 corresponding DNS records are updated, the old addresses would be 508 removed and the site would be single-homed on the new upstream 509 network. 511 If a host is multihomed on different links within a single-homed 512 site, the node would be associated with only one node address since 513 the prefixes would be the same for all different links. The node can 514 be reached through any of these links. With the usual IPv6 or some 515 LIS protocols [HIP][ILNP], each interface of the node would be given 516 a distinct locator so that the peer node should choose between 517 multiple locators to reach the same node, which task being either 518 arbitrary or complicated. With SID6, however, the node is associated 519 with a single node address so that there'd be no confusion or extra 520 work burden on the part of the peer node. 522 If a host is multihomed on different sites, the node would possess 523 multiple node addresses each derived from different site prefixes. 524 Each of such node addresses is used to reach the node via the 525 corresponding site network. 527 If a subnet is multihomed on different sites, only the nodes within 528 the very subnet would be given multiple node addresses each derived 529 from prefixes of the different sites. Nodes in other subnets would 530 not be affected. 532 If a site is multihomed on different upstream networks, all internal 533 nodes, either hosts or routers, would be given multiple node 534 addresses derived from different site prefixes assigned by different 535 upstream networks. 537 4.6. Incremental Deployability 539 SID6 can be deployed incrementally. A site can adopt SID6, yet the 540 external behaviors exposed to DFZ remain the same as with a legacy 541 IPv6 site and so cause no disturbance to DFZ. 543 4.7. Prefix Aggregation and Scalability 545 Prefix aggregation in DFZ is done as usual. That is, DFZ routing 546 scalability of SID6 is as good as the legacy IPv6 networking. 548 4.8. Incentives for Deployment 550 An apparent incentive to deploy SID6 should be that transport 551 connection resilience for intra-site mobile nodes can be provided 552 with no extra infrastructure like mapping servers found in most LIS 553 protocols [HIP][ILNP][LISP], resulting in a significant resource 554 saving. An equivalent incentive in comparison with the legacy IPv6 555 networking would be that intra-site mobility, and that faster, can be 556 provided inherently by any interior link-state protocols, with no 557 hassle of installing MIPv6 functionalities on every router in a site. 558 Considering that a site can be arbitrarily large, this can be a 559 considerable additional resource saving in terms of network 560 operation. 562 5. Conclusions 564 A new IPv6 networking paradigm called SID6 is introduced, wherein the 565 IPv6 SID is deprecated, that is, set to zero or replaced by a local 566 prefix tuple. As a result, a node is associated with a site-local 567 NID, instead of one or more link-local IIDs as with the legacy IPv6 568 networking. 570 With SID6, the task of simultaneous identification and location of a 571 node, wrestled with by other LIS solutions through separate (ID and 572 locator) number spaces, is accomplished without introducing a number 573 space extra to that already available for node addresses. 574 Furthermore, the job is done stepwise across two adjacent tiers; 575 intra-site and inter-site: 577 o Within a site (intra-site), identification is provided through the 578 NID or the local prefix while location is through an intra-domain 579 link-state routing protocol. 581 o Across sites (inter-site), identification is provided through 582 (global) node addresses while location is by the site prefix. 584 With SID6, there's no need for deployment and management of the 585 mapping servers (IDs versus locators), which should be a substantial 586 resource saving over usual LIS solutions. 588 An additional advantage of SID6 is that intra-site mobility is 589 provided inherently by a link-state protocol, and that faster and 590 more efficiently than with MIPv6. Moreover, MIPv6 agents need be 591 installed only on site border routers, not on every intra-site 592 router, thus resulting in another notable resource saving. 594 Behaviors of a SID6 site externally exposed to DFZ remain the same as 595 with usual legacy IPv6 sites, enabling incremental deployment. 597 This document has presented SID6 only for the case of a single-area 598 routing domain. The case of a multi-area domain is for further 599 study. Application of the equivalent idea to IPv4 networking is also 600 left for further study. 602 6. Security Considerations 604 SID6 should be as secure or insecure as the legacy IPv6 networking. 605 As for privacy, there are documents for hiding node locality within a 606 site [SLAACPRIV][IIDSv6][IIDOPAQUE]. Randomizing IIDs works fine 607 with SID6 since randomizing takes place only at node 608 (re-)initialization once or not frequently enough [SLAACPRIV]. 610 IID hashing is a function of not only the global routing prefix but 611 also SID [IIDSv6][IIDOPAQUE]; when a node moves to a foreign link, a 612 new IID would be generated to hide the locality of the node from 613 other hosts. In SID6, the hashed NID would not change at such an 614 intra-site move, and hence its locality would be exposed. However, 615 this exposure is only to the routers which keep locality information 616 of nodes in their routing tables which are opaque to hosts. Hosts 617 have no clues which link other nodes reside in or have moved to, 618 except for on-link nodes in Neighbor Cache. Hosts would simply rely 619 on DRs for packet deliveries to off-link nodes. Therefore, the 620 privacy offered by [IIDSv6][IIDOPAQUE] would be scarcely affected. 622 7. IANA Considerations 624 There are no requests to IANA at the current stage of the document. 626 8. References 628 8.1. Normative References 630 [DASv6] Thaler, D., Ed., Draves, R., Matsumoto, A., and T. Chown, 631 "Default Address Selection for Internet Protocol Version 6 632 (IPv6)", RFC 6724, DOI 10.17487/rfc6724, Sep. 2012, 633 . 635 [DHCPv6] Droms, R., Ed., Bound, J., Volz, B., Lemon, T., Perkins, 636 C., and M. Carney, "Dynamic Host Configuration Protocol 637 for IPv6 (DHCPv6)", RFC 3315, DOI 10.17487/rfc3315, Jul. 638 2003, . 640 [ICMPv6] Conta, A., Deering, S., and M. Gupta, Ed., "Internet 641 Control Message Protocol (ICMPv6) for the Internet 642 Protocol Version 6 (IPv6) Specification", RFC 4443, 643 DOI 10.17487/rfc4443, Mar. 2006, 644 . 646 [IIDOPAQUE] 647 Gont, F., "A Method for Generating Semantically Opaque 648 Interface Identifiers with IPv6 Stateless Address 649 Autoconfiguration (SLAAC)", RFC 7217, 650 DOI 10.17487/rfc7217, Apr. 2014, 651 . 653 [IIDSv6] Gont, F., Cooper, A., Thaler, D., and W. Liu, 654 "Recommendation on Stable IPv6 Interface Identifiers", 655 RFC 8064, DOI 10.17487/rfc8064, Feb. 2017, 656 . 658 [ISISv4] Callon, R., "Use of OSI IS-IS for Routing in TCP/IP and 659 Dual Environments", RFC 1195, DOI 10.17487/rfc1195, Dec. 660 1990, . 662 [ISISv6] Hopps, C., "Routing IPv6 with IS-IS", RFC 5308, 663 DOI 10.17487/rfc5308, Oct. 2008, 664 . 666 [KEYWORDS] 667 Bradner, S., "Key words for use in RFCs to Indicate 668 Requirement Levels", BCP 14, RFC 2119, 669 DOI 10.17487/rfc2119, March 1997, 670 . 672 [MIPv6] Perkins, C., Ed., Johnson, D., and J. Arkko, "Mobility 673 Support in IPv6", RFC 6275, DOI 10.17487/rfc6275, Jul. 674 2011, . 676 [NDv6] Narten, T., Nordmark, E., Simpson, W., and H. Soliman, 677 "Neighbor Discovery for IP version 6 (IPv6)", RFC 4861, 678 DOI 10.17487/rfc4861, Sep. 2007, 679 . 681 [OSPFv3] Coltun, R., Ferguson, D., Moy, J., and A. Lindem, Ed., 682 "OSPF for IPv6", RFC 5340, DOI 10.17487/rfc5340, Jul. 683 2008, . 685 [p2p127] Kohno, M., Nitzan, B., Bush, R., Matsuzaki, Y., Colitti, 686 L., and T. Narten, "Using 127-Bit IPv6 Prefixes on Inter- 687 Router Links", RFC 6164, DOI 10.17487/rfc6164, Apr. 2011, 688 . 690 [SLAAC] Thomson, S., Narten, T., and T. Jinmei, "IPv6 Stateless 691 Address Autoconfiguration", RFC 4862, 692 DOI 10.17487/rfc4862, Sep. 2007, 693 . 695 [SLAACPRIV] 696 Narten, T., Draves, R., and S. Krishnan, "Privacy 697 Extensions for Stateless Address Autoconfiguration in 698 IPv6", RFC 4941, DOI 10.17487/rfc4941, Sep. 2007, 699 . 701 [Uv6pH] Brzozowski, J. and G. Van De Velde, "Unique IPv6 Prefix 702 per Host", RFC 8273, DOI 10.17487/rfc8273, December 2017, 703 . 705 [v6ADDR] Hinden, R. and S. Deering, "IP Version 6 Addressing 706 Architecture", RFC 4291, DOI 10.17487/rfc1149, Feb. 2006, 707 . 709 [v6SUBNET] 710 Singh, H. and W. Nordmark, "IPv6 Subnet Model: The 711 Relationship between Links and Subnet Prefixes", RFC 5942, 712 DOI 10.17487/rfc5942, Jul. 2010, 713 . 715 8.2. Informartive References 717 [HIP] Moskowitz, R. and P. Nikander, "Host Identity Protocol 718 (HIP) Architecture", RFC 4423, DOI 10.17487/rfc4423, May 719 2006, . 721 [ILNP] Atkinson , R., Bhatti, S., and U. Andrews, "ILNP 722 Architectural Description", RFC 6740, 723 DOI 10.17487/rfc6740, Nov. 2012, 724 . 726 [LISP] Farinacci, D., Fuller, V., Meyer, D., and D. Lewis, 727 "Locator/ID Separation Protocol (LISP)", RFC 6830, 728 DOI 10.17487/rfc6830, Jan. 2013, 729 . 731 [SID6P] Kim, YH., Kim, DY., and JW. Park, "IPv6 Networking with 732 Subnet ID Deprecated", Journal of Computing Science and 733 Engineering , vol. 11, no. 2, pp. 49-57, June 2017, 734 . 736 Author's Address 738 DY Kim 739 Independent 740 Gangwon 741 South KOREA 743 Email: dykim6@gmail.com