One document matched: draft-hain-6to4-scaling-00.txt



NGtrans                                                         T. Hain 
Internet Draft                                                Microsoft 
Document: draft-hain-6to4-scaling-00.txt                      July 2000 
Category:                                                               
 
 
                     6to4-relay discovery and scaling 
 
 
Status of this Memo 
    
   This document is an Internet-Draft and is in full conformance with 
   all provisions of Section 10 of RFC2026 [1].  
    
   Internet-Drafts are working documents of the Internet Engineering 
   Task Force (IETF), its areas, and its working groups. Note that 
   other groups may also distribute working documents as Internet-
   Drafts. Internet-Drafts are draft documents valid for a maximum of 
   six months and may be updated, replaced, or obsoleted by other 
   documents at any time. It is inappropriate to use Internet- Drafts 
   as reference material or to cite them other than as "work in 
   progress."  
   The list of current Internet-Drafts can be accessed at 
   http://www.ietf.org/ietf/1id-abstracts.txt  
   The list of Internet-Draft Shadow Directories can be accessed at 
   http://www.ietf.org/shadow.html. 
    
    
    
Abstract 
    
   The mechanism for 6to4-router scaling described in the 6to4 draft 
   [2][6to4] raises concerns when the matrix of IPv4 connected systems, 
   communicating across to the native IPv6 connected systems, are on 
   the order of tens to hundreds of millions. This document will 
   address those concerns, offer additional mechanisms for resolving 
   them, and identify the scenario for link-local addressing postulated 
   in section 3.1.  
    
    














  
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Table of Contents 
   Status of this Memo................................................1 
   Abstract...........................................................1 
   Table of Contents..................................................2 
   Terms..............................................................2 
   Overview and assumptions...........................................3 
   Scenarios..........................................................5 
     Fig. 1...........................................................5 
     Sequence Scenario 1:.............................................6 
     Sequence Scenario 2:.............................................7 
   NS syntax..........................................................9 
   NA syntax..........................................................9 
   Redirect syntax...................................................10 
     Protection from random redirects:...............................11 
   Additional Requirements...........................................11 
   Additional Thoughts...............................................12 
   Security Considerations...........................................12 
   References........................................................12 
   Acknowledgments...................................................13 
   Author's Addresses................................................13 
    
    
   Conventions used in this document 
    
   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 
   "SHOULD", "SHOULD NOT", "RECOMMENDED",  "MAY", and "OPTIONAL" in 
   this document are to be interpreted as described in RFC-2119 [3]. 
    
    
    
Terms 
   (expanding slightly on the definitions in [6to4]) 
    
   6to4-router: an IPv6 router supporting a 6to4 pseudo-interface. It 
   is normally the border router between an IPv6 site and a wide-area 
   IPv4 network. When not acting as a relay, it advertises 
   [2002:IPv4::/48] as an attached prefix on IPv6 enabled interfaces. 
    
   Relay router: a 6to4-router configured to support transit routing 
   between 6to4 addresses and native IPv6 addresses. Advertises the 
   [2002::/16] as an attached prefix on native IPv6 enabled interfaces. 
   (referred to as 6to4-relay in this document) 
    
   6to4 normal host: an IPv6 host, which happens to have at least one 
   6to4 address learned from a 6to4-router. In all other respects it is 
   a standard IPv6 host. 
    
   6to4 integrated host: an IPv6 host that generates at least one 6to4 
   address and supporting 6to4 pseudo-interface from an IPv4 address. 
   It interacts directly with relays, but in all other respects it is a 
   standard IPv6 host. 
    
    
    
     
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Overview and assumptions 
    
   The intent of this approach is to use the mechanism defined in 
   [6to4] as a simplifier for providing IPv6 services to any node with 
   a public IPv4 address. (While IPv4-compatible IPv6 addresses would 
   be another option, there have been questions raised related to their 
   use and the scaling impact on the IPv6 routing tables.) The 
   technical aspects of creating the appropriate addresses are not an 
   issue, but there is an area of concern related to discovery of the 
   path from 6to4 nodes to native-IPv6 nodes. Several schemes have been 
   proposed, and the approach described here does not preclude any of 
   them. What it does is provide an alternative that automates the 
   process on a massive scale, without requiring the 6to4 routers to 
   participate directly in a global routing process.  
    
   One way to look at this approach is an automated tunnel broker that 
   is tied to the current routing infrastructure. Existing tunnel 
   broker models expect manual interaction and basically set up a 
   default route to the entire native IPv6 infrastructure. If the 
   native IPv6 network partitions, the communications will fail even 
   though the IPv4 network is intact. The approach presented here would 
   theoretically allow for islands of native IPv6 to exist around the 
   edge of the IPv4 cloud, as long as the regional relays know the 
   current prefix to IPv4 mapping for the relays. 
    
   Another way to look at this approach is a default route that only 
   handles one packet per prefix, and then redirects each node directly 
   attached to the IPv4 network to the appropriate native-IPv6-ISP 
   6to4-relay for subsequent packets.  
    
   The default route approach works because from the perspective of the 
   6to4-router (or integrated host), the entire IPv4 Internet appears 
   to be a single-subnet link-layer. While section 3.1 of [6to4] 
   discusses the formation of addresses in a link-local context, it 
   questions the utility of such addresses. The mechanism described 
   here answers the question by taking advantage of the format for 
   communicating with a well-known relay, as well as in the redirect 
   messages sent by relays. A final point to make is that in addition 
   to appearing as a single link-layer, the IPv4 Internet does not 
   provide multicast to all points, so it should be considered an NBMA 
   network. Since the IPv4 Internet appears to be a single link to 6to4 
   nodes, all rules in section 8 of [4][ND] apply to redirects 
   described here, EXCEPT the one at the end of 8.2 that prohibits 
   routers from updating routes based on redirects. It should also be 
   noted that part of a previously reserved field is now defined. 
    
   A basic assumption is that a 6to4 based IPv6 deployment will not 
   rely on ANY support from IPv4 only ISP's. If a 6to4-relay (willing 
   to take the traffic) exists, a site 6to4-router may be configured to 
   use that path as the default route to the native IPv6 infrastructure 
   through a tunnel broker, or other means. If there is no configured 
   relay, the default behavior of 6to4-routers SHOULD be to use a well-

     
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   known starting point to find a 6to4-relay that will get it to the 
   native IPv6 endpoint. 
    
   Another assumption is that each ISP providing native IPv6 services 
   will be motivated to provide a relay service for their customers to 
   communicate with 6to4 sites. At the same time, these ISPs will 
   generally not want to be the 'default' route between 6to4 & native 
   IPv6 infrastructures. They will also not be excited about managing a 
   massive manually configured tunnel array (no matter which end the 
   manual effort is applied to). Once a 6to4-router (integrated host) 
   acquires a prefix to relay mapping, it SHOULD send NS messages to 
   maintain the mapping until idle for 2 lifetimes. To aid with 
   scaling, there is no need for the relay to maintain a mapping to the 
   6to4-router (integrated host) as the required information is in the 
   destination address of each packet header.  
    
   Consumer systems (ie:dial-up) will be completely automated 6to4 
   integrated hosts. To make this automation work, a well-known relay 
   service needs to exist and be capable of handling greater than 10M 
   clients. This results in scaling issues that are comparable to the 
   DNS root.  
    
   Maintaining a static database with full IPv6 addresses of the 
   current ISP relays is operationally complex. As only the IPv4 
   address are required when using link-local [FE80::IPv4] format 
   addresses, this has better scaling properties for database 
   maintenance. (The Anycast address [2002:IPv4::0] would be a 
   comparable alternative, but redirect messages require use of a link-
   local address).  
    
   The regional access relays described below are currently assumed to 
   be geographical, but the native-IPv6-ISP ones they redirect to are 
   assumed to be topologically near the native IPv6 end. 





















     
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Scenarios 
    
   1. A Consumer system dials into their preferred ISP and only 
   receives IPv4 service. Using the 6to4 mechanisms as defined, the 
   system creates IPv6 addresses for its interface. Later an 
   application attempts to connect to a system that is connected to a 
   native IPv6 network (non-2002::). The consumer system forwards the 
   first packet to the well-known relay 6to4-relay.ipv6.org, and 
   verifies the redirect it receives for the destination prefix. 
   Further communications are directed to the native-IPv6-ISP 6to4-
   relay. NS messages SHOULD be sent to the native-IPv6-ISP 6to4-relay 
   to maintain this Prefix / IPv4 address / Lifetime mapping until idle 
   for at least two lifetimes. 
    
   2. An IPv6 only system initiates a connection to a 6to4 web site. 
   The native-IPv6-ISP 6to4-relay extracts the IPv4 address from the 
   destination IPv6 address, and tunnels per the 6to4 specification. 
   The 6to4-router will use the response from the web site to establish 
   the mapping between the native-IPv6 prefix, and its 6to4-relay via 
   the well-known 6to4-relay. NS messages SHOULD be sent to the native-
   IPv6-ISP 6to4-relay to maintain this Prefix / IPv4 address / 
   Lifetime mapping information until idle for at least two lifetimes.  
    
    
                                         -----     ------------ 
                                        |     |   | 6to4-relay.| 
                                        | DNS |   |AR.ipv6.org | 
                                         -----     ------------ 
                                           |       | 
       -------------     ------------     -----------     ---------- 
      | Native IPv6 |   | 6to4-relay |   | IPv4 only |   | Consumer | 
      |     system  |-/-|   IPv6 ISP |---| Internet  |-/-| system   | 
       -------------     ------------     -----------     ---------- 
                                               | 
                                          -------------     ----- 
                                         | 6to4-router |   | Web | 
                                         |             |---| site| 
                                          -------------     ----- 
                                      
                                   ----- 
                                  Fig. 1 













     
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Sequence Scenario 1: 
    
      1) The 6to4 process in a consumer system automatically looks up 
          the IPv4 address of the well-known relay 6to4-relay.ipv6.org 
          for any non-2002:: destination that does not match a prefix 
          in the routing cache, using IPv4. 
       
      2) DNS returns a Cname based on the RIR of the requestors IPv4. 
       
      3) The 6to4 process then automatically looks up 6to4-
          relay.RIR.ipv6.org 
       
      4) DNS returns a traditional IPv4 round-robin for relays per 
          region.  
       
      5) The 6to4 process uses 6to4 rules for link-local and tunnels 
          the initial packet to the regional relay.  
       
      6) Regional Registries have collected IPv4 addresses of ISP 
          6to4-relays as each IPv6 prefix is allocated. 
       
      7) Regional access and ISP relays participate in the global BGP 
          mesh.  
       
      8) Regional access relay sends IPv6 prefix-based redirect to the 
          Consumer system, pointing it to the native-IPv6-ISP 6to4-
          relay having the longest match. It then forwards the original 
          packet to the identified native-IPv6-ISP 6to4-relay. 
       
      9) The 6to4 process builds a routing table cache from the 
          redirect messages. It first verifies the redirect through the 
          new 'Tunnel Ident' field (IPv4 Identifier in original tunnel 
          packet). Subsequent tunneling is based on longest match on 
          prefix. Once it knows the neighbor, the 6to4-router, or 
          integrated host, SHOULD send NS to the ISP relay it was 
          redirected to for maintenance of the mapping. 
       
      10) The 6to4 process resends first packet, now tunneled to the 
          native-IPv6-ISP 6to4-relay topologically closest to the 
          native IPv6 end of this traffic flow. 
       
      11) Destination ISP relay forwards within the IPv6 network. (It 
          SHOULD already be advertising the return route to 2002::/16.) 
       
      12) The Native-IPv6 system sends an Ack for first packet via the 
          nearest relay advertising 2002::/16. 
       
      13) The Native-IPv6-ISP 6to4-relay extracts the IPv4 from 
          destination in packet header and tunnels the packet across 
          the IPv4 logical link. 
       
   ------ 


     
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Sequence Scenario 2: 
    
      1. The Native-IPv6 system looks up the name 6to4-web-site.   
       
      2. DNS MAY return a 2002:: record in a traditional round-robin 
          for the web site. 
       
      3. The native-IPv6 system sends its first packet via the nearest 
          relay advertising 2002::/16. 
       
      4. The native-IPv6-ISP 6to4-relay extracts the IPv4 from 
          destination in packet header and tunnels the packet across 
          the IPv4 logical link.  
       
      5. The 6to4-router for the web site forwards the packet to the 
          destination web site. 
       
      6. The Web site sends an ACK via its 6to4-router. 
       
      7. The 6to4 process in the 6to4-router looks up the IPv4 address 
          of the well-known relay 6to4-relay.ipv6.org for any non-
          2002:: destination that does not match a prefix in the 
          routing cache, using IPv4. 
    
      8. DNS returns a Cname based on the RIR of the requestors IPv4. 
       
      9. The 6to4 process then automatically looks up 6to4-
          relay.RIR.ipv6.org 
       
      10. DNS returns a traditional IPv4 round-robin for relays per 
          region.  
       
      11. The 6to4 process uses 6to4 rules for link-local and tunnels 
          the packet to the regional relay. 
       
      12. Regional Registries have collected IPv4 addresses of ISP 
          6to4-relays as each IPv6 prefix is allocated. 
       
      13. Regional access and ISP relays participate in the global BGP 
          mesh. 
       
      14. Regional access relay sends IPv6 prefix-based redirect to the 
          6to4 router, pointing it to the native-IPv6-ISP 6to4-relay 
          having the longest match.  
       
      15. The 6to4-router builds a routing table cache from the 
          redirect messages. It first verifies the redirect through the 
          new 'Tunnel Ident' field (IPv4 Identifier in original tunnel 
          packet). Subsequent tunneling is based on longest match on 
          prefix. Once it knows the neighbor, the 6to4-router, or 
          integrated host, SHOULD send NS to the ISP relay it was 
          redirected to for maintenance of the mapping. 
       
     
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      *** This creates a perceived problem : -router responding to 
          redirect- Actually RFC 1812 [5][routerreq] 5.2.7.2 states 
          'MAY consider redirect when not running a routing protocol', 
          which is the case at hand; at least with other parties 
          involved with this logical link.  
       
      16. 6to4-router forwards to native-IPv6-ISP 6to4-relay based on 
          the longest match. 
       
      17. Native-IPv6-ISP 6to4-relay forwards to Native-IPv6 system. 
       
   ------- 










































     
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NS syntax 
    
   0                   1                   2                   3 
   0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
   |    Type (135) |    Code (0)   |          Checksum             | 
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
   |                           Reserved                            | 
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
   |                                                               | 
   ~                       Target Address    (FE80::IPv4)          ~ 
   |                                                               | 
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
   |     Type (2)  |    Length (1) |            MUST be 0          | 
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
   |             Link-Layer Address (IPv4 of 6to4-router)          | 
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
    
    
NA syntax 
    
   0                   1                   2                   3 
   0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
   |    Type (136) |    Code (1)   |          Checksum             | 
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
   |R|S|O|                     Reserved                            | 
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
   |                                                               | 
   ~                       Target Address    (FE80::IPv4)          ~ 
   |                                                               | 
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
   |     Type (2)  |    Length (1) |            MUST be 0          | 
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
   |             Link-Layer Address (IPv4 of 6to4-relay)           | 
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
   |     Type (3)  |    Length (4) | Prefix Length |L|A| Reserved1 | 
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
   |                         Valid Lifetime                        | 
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
   |                       Preferred Lifetime                      | 
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
   |                           Reserved2                           | 
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
   |                                                               | 
   ~             Prefix (from table for this target)               ~ 
   |                                                               | 
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
    
   Code is set to 1 to identify new message with prefix information 
    
   R-bit is set as the 6to4-relay is logically a router 
   S-bit is set in response to solicitation 
   O-bit is cleared to prevent thrashing 
     
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Redirect syntax 
    
   (Expands scope for redirect from host to prefix) 
    
   0                   1                   2                   3 
   0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
   |    Type (137) |    Code (0)   |          Checksum             | 
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
   |                           Reserved                            | 
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
   |                                                               | 
   ~                       Target Address (FE80::IPv4)             ~ 
   |                                                               | 
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
   |                                                               | 
   ~                     Destination Address                       ~ 
   |                                                               | 
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
   |     Type (2)  |    Length (1) |            MUST be 0          | 
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
   |             Link-Layer Address (IPv4 of 6to4-relay)           | 
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
   |     Type (3)  |    Length (4) | Prefix Length |L|A| Reserved1 | 
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
   |                         Valid Lifetime                        | 
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
   |                       Preferred Lifetime                      | 
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
   |                           Reserved2                           | 
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
   |                                                               | 
   ~             Prefix (from table for this target)               ~ 
   |                                                               | 
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
   |     Type  (4) |    Length     |        Tunnel Ident           | 
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
   |                           Reserved                            | 
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
   |                                                               | 
   ~                       IP header + data                        ~ 
   |                                                               | 
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
    
   IP header + data is the original packet truncated to ensure that the 
   size of the redirect message does not exceed 1280 octets. 
    
   Valid lifetime and Preferred lifetime are set to the time remaining 
   until next scheduled BGP update  
    
   'Tunnel Ident' is used for spoof protection, and is filled in from 
   the Identity field from the IPv4 header of the 6to4 packet.  
    

     
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Protection from random redirects: 
    
   For simple spoof protection, the upper 16 bits of the 'Tunnel Ident' 
   field (previously reserved) in the Redirected Header option are used 
   to reflect the Identifier field from the outer IPv4 header of the 
   original packet sent to the Regional Relay. This combined with the 
   original packet contents mitigate guessing or flooding attacks, and 
   virtually require access to the packet path to generate a valid 
   spoof.  
    
    
Additional Requirements 
    
   Regional relays are run as ipv6.org named service by the Regional 
   Internet Registries (RIRs).  
    
   Registration of native-IPv6-ISP relays is handled through RIRs, 
   because a trust model exists and it appears to be an easy addition 
   to the allocation process. 
    
   Regional relays SHOULD address scaling to support the number of 
   directly attached IPv4 systems in their area, and forward any 
   packets received to the same ISP relay it identified in the prefix-
   based redirect defined above. Severe rate limiting MAY be imposed to 
   discourage 6to4-routers and integrated hosts from ignoring these 
   redirect messages.  
    
   6to4 integrated hosts, routers, and relays MUST recognize and 
   respond to ICMP messages targeted for [FE80::IPv4] that are received 
   on the 6to4 interface. 
    
   6to4-routers SHOULD establish NUD (as defined in section 3.8 of 
   [6][mech]) with 6to4-relays they are redirected to, and avoid 
   thrashing if multiple relays exist for a given prefix. The ISP 
   relays MAY establish NUD with the routers if desired, though this 
   will create scaling concerns with the only marginal benefit being 
   the rapid removal of access to nodes behind the an individual IPv4 
   address.  
    
   6to4-routers MAY choose to time out this prefix entry if there is no 
   traffic for two valid lifetimes. 
    
   6to4-relays SHOULD address scaling for both traffic handling and NUD 
   exchanges. 
    
   6to4-relays MAY send prefix based redirects to provide load 
   balancing among relays not directly identified via BGP. 
    
   Neighbor solicitation (type 135) is sent when the lifetime expires. 
   The 6to4-relay SHOULD answer if it is still willing to forward with 
   a Neighbor Advertisement (type 136) including the options defined 
   for redirect. 
    
    
     
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Additional Thoughts 
    
   Separate regional relays are not required if native-IPv6-ISPs are 
   willing to have their relays act as the first packet top-level 
   redirectors for non-customers. The only requirements are 
   establishing who manages the round-robin DNS entries for each 
   regions relay name; and that all systems in that list be 
   participants in the global BGP mesh, as well as willing and capable 
   of generating the prefix based redirects.  
    
    
Security Considerations 
 
   This document does not introduce any new security concerns, and 
   attempts to add some level of protection from spoofed redirects 
   received over the 6to4 interface. Basic protection from spoofed 
   redirects is provided unless the routing path infrastructure is 
   penetrated. Additional protection of the redirect is possible using 
   IPsec. This approach is not used by default, as the case where it is 
   necessary is rare, and the cost is relatively high. 
    
   Denial-of-Service attacks are possible against the common 
   infrastructure in the Regional Relays. If such an attack is detected 
   the targeted relay MAY choose to stop forwarding packets and only 
   issue redirects. This will impact application responsiveness as 
   packets are discarded, but not as dramatically as loosing all 
   ability to find the native IPv6 relays should the regional relays 
   become inundated.  
    
   Denial-of-service attacks against other components described here 
   are beyond the scope of this document, as those components are not 
   common infrastructure and their defense is a local matter.  
    
    
References 
    
 
   1  [RFC-2026], Bradner, S., " The Internet Standards Process -- 
      Revision 3", BCP 9, RFC 2026, October 1996. 
    
   2  [6to4], Carpenter, B., "Connection of IPv6 Domains via IPv4 
      Clouds without Explicit Tunnels", draft-ietf-ngtrans-6to4-06.txt, 
      June 2000 
    
   3  [RFC-2119], Bradner, S., "Key words for use in RFCs to Indicate 
      Requirement Levels", BCP 14, RFC 2119, March 1997 
    
   4  [ND], Narten, T., Nordmark, E., Simpson, W., "Neighbor Discovery 
      for IP Version 6", RFC 2461, December 1998 
    
   5  [routerreq] Baker, F., "Requirements for IP Version 4 Routers", 
      RFC-1812, June 1995 
    
 
     
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   6  [mech], Nordmark, E., Gilligan, R. E., "Transition Mechanisms for 
      IPv6 Hosts and Routers", April 14, 2000 
    
    
    
    
Acknowledgments 
    
   Thanks for critique of this document provided by Christian Huitema, 
   David Thaler, Fred Baker and Brian Carpenter.  
    
    
Author's Addresses 
    
   Tony Hain 
   Microsoft 
   One Microsoft Way 
   Redmond, Wa. USA  98052 
   Email: tonyhain@microsoft.com 
    

































     
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