draft-ietf-dnsop-ipv6-dns-configuration-06.txt revision e3c0f34cba09741486b31db3814fc3a26227547b
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob AusteinDNS Operations WG J. Jeong, Ed.
4a14ce5ba00ab7bc55c99ffdcf59c7a4ab902721Automatic UpdaterInternet-Draft ETRI/University of Minnesota
4610465ed9408cbe434dbfb8be8ea53f48969c91Bob HalleyExpires: November 6, 2005 May 5, 2005
8a66318e41ed14c5a88130e8c362610e8faa2121Mark Andrews IPv6 Host Configuration of DNS Server Information Approaches
8a66318e41ed14c5a88130e8c362610e8faa2121Mark AndrewsStatus of this Memo
8a66318e41ed14c5a88130e8c362610e8faa2121Mark Andrews This document is an Internet-Draft and is subject to all provisions
8a66318e41ed14c5a88130e8c362610e8faa2121Mark Andrews of Section 3 of RFC 3667. By submitting this Internet-Draft, each
4610465ed9408cbe434dbfb8be8ea53f48969c91Bob Halley author represents that any applicable patent or other IPR claims of
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein which he or she is aware have been or will be disclosed, and any of
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein which he or she become aware will be disclosed, in accordance with
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2eeb74d1cf5355dd98f6d507a10086e16bb08c4bTinderbox UserCopyright Notice
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein Copyright (C) The Internet Society (2005).
b2f07642fd712c8fda81a116bcdde229ab291f33Tinderbox User This document describes three approaches for IPv6 recursive DNS
b2f07642fd712c8fda81a116bcdde229ab291f33Tinderbox User server address configuration. It details the operational attributes
b2f07642fd712c8fda81a116bcdde229ab291f33Tinderbox User of three solutions: RA option, DHCPv6 option, and Well-known anycast
2eeb74d1cf5355dd98f6d507a10086e16bb08c4bTinderbox User addresses for recursive DNS servers. Additionally, it suggests the
b2f07642fd712c8fda81a116bcdde229ab291f33Tinderbox User deployment scenarios in four kinds of networks, such as ISP,
b2f07642fd712c8fda81a116bcdde229ab291f33Tinderbox User Enterprise, 3GPP, and Unmanaged networks, considering multi-solution
b2f07642fd712c8fda81a116bcdde229ab291f33Tinderbox User resolution. Therefore, this document will give the audience a
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60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob AusteinInternet-Draft IPv6 Host Configuration of DNS Server May 2005
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein guideline for IPv6 host DNS configuration.
6d45011a65dfc43f476ca15c3fd9ee5227eb968fTinderbox UserJeong Expires November 6, 2005 [Page 2]
2eeb74d1cf5355dd98f6d507a10086e16bb08c4bTinderbox UserInternet-Draft IPv6 Host Configuration of DNS Server May 2005
fd2597f75693a2279fdf588bd40dfe2407c42028Tinderbox UserTable of Contents
fd2597f75693a2279fdf588bd40dfe2407c42028Tinderbox User 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 5
659d063f23a35d77ad5826e6556d3137672bb937Tinderbox User 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 6
fd2597f75693a2279fdf588bd40dfe2407c42028Tinderbox User 3. IPv6 DNS Configuration Approaches . . . . . . . . . . . . . . 7
c247e3f281613fabe1af362e9f3157e35ebbe52cMark Andrews 3.1 RA Option . . . . . . . . . . . . . . . . . . . . . . . . 7
fd2597f75693a2279fdf588bd40dfe2407c42028Tinderbox User 3.1.1 Advantages . . . . . . . . . . . . . . . . . . . . . . 8
659d063f23a35d77ad5826e6556d3137672bb937Tinderbox User 3.1.2 Disadvantages . . . . . . . . . . . . . . . . . . . . 8
659d063f23a35d77ad5826e6556d3137672bb937Tinderbox User 3.1.3 Observations . . . . . . . . . . . . . . . . . . . . . 9
659d063f23a35d77ad5826e6556d3137672bb937Tinderbox User 3.2 DHCPv6 Option . . . . . . . . . . . . . . . . . . . . . . 9
659d063f23a35d77ad5826e6556d3137672bb937Tinderbox User 3.2.1 Advantages . . . . . . . . . . . . . . . . . . . . . . 11
2eeb74d1cf5355dd98f6d507a10086e16bb08c4bTinderbox User 3.2.2 Disadvantages . . . . . . . . . . . . . . . . . . . . 12
659d063f23a35d77ad5826e6556d3137672bb937Tinderbox User 3.2.3 Observations . . . . . . . . . . . . . . . . . . . . . 12
659d063f23a35d77ad5826e6556d3137672bb937Tinderbox User 3.3 Well-known Anycast Addresses . . . . . . . . . . . . . . . 12
2eeb74d1cf5355dd98f6d507a10086e16bb08c4bTinderbox User 3.3.1 Advantages . . . . . . . . . . . . . . . . . . . . . . 13
659d063f23a35d77ad5826e6556d3137672bb937Tinderbox User 3.3.2 Disadvantages . . . . . . . . . . . . . . . . . . . . 14
659d063f23a35d77ad5826e6556d3137672bb937Tinderbox User 3.3.3 Observations . . . . . . . . . . . . . . . . . . . . . 14
659d063f23a35d77ad5826e6556d3137672bb937Tinderbox User 4. Interworking among IPv6 DNS Configuration Approaches . . . . . 15
659d063f23a35d77ad5826e6556d3137672bb937Tinderbox User 5. Deployment Scenarios . . . . . . . . . . . . . . . . . . . . . 16
659d063f23a35d77ad5826e6556d3137672bb937Tinderbox User 5.1 ISP Network . . . . . . . . . . . . . . . . . . . . . . . 16
659d063f23a35d77ad5826e6556d3137672bb937Tinderbox User 5.1.1 RA Option Approach . . . . . . . . . . . . . . . . . . 16
659d063f23a35d77ad5826e6556d3137672bb937Tinderbox User 5.1.2 DHCPv6 Option Approach . . . . . . . . . . . . . . . . 17
fd2597f75693a2279fdf588bd40dfe2407c42028Tinderbox User 5.1.3 Well-known Anycast Addresses Approach . . . . . . . . 17
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein 5.2 Enterprise Network . . . . . . . . . . . . . . . . . . . . 17
fd2597f75693a2279fdf588bd40dfe2407c42028Tinderbox User 5.3 3GPP Network . . . . . . . . . . . . . . . . . . . . . . . 18
fd2597f75693a2279fdf588bd40dfe2407c42028Tinderbox User 5.3.1 Currently Available Mechanisms and Recommendations . . 19
fd2597f75693a2279fdf588bd40dfe2407c42028Tinderbox User 5.3.2 RA Extension . . . . . . . . . . . . . . . . . . . . . 19
fd2597f75693a2279fdf588bd40dfe2407c42028Tinderbox User 5.3.3 Stateless DHCPv6 . . . . . . . . . . . . . . . . . . . 20
2eeb74d1cf5355dd98f6d507a10086e16bb08c4bTinderbox User 5.3.4 Well-known Addresses . . . . . . . . . . . . . . . . . 21
2eeb74d1cf5355dd98f6d507a10086e16bb08c4bTinderbox User 5.3.5 Recommendations . . . . . . . . . . . . . . . . . . . 21
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein 5.4 Unmanaged Network . . . . . . . . . . . . . . . . . . . . 22
fd2597f75693a2279fdf588bd40dfe2407c42028Tinderbox User 5.4.1 Case A: Gateway does not provide IPv6 at all . . . . . 22
0ccb0e98c77a9b9636a036f8f64f5679a430aaf4Tinderbox User 5.4.2 Case B: A dual-stack gateway connected to a
0ccb0e98c77a9b9636a036f8f64f5679a430aaf4Tinderbox User dual-stack ISP . . . . . . . . . . . . . . . . . . . . 22
fd2597f75693a2279fdf588bd40dfe2407c42028Tinderbox User 5.4.3 Case C: A dual-stack gateway connected to an
395c95214142142854509945adf3293c0270e1c5Tinderbox User IPv4-only ISP . . . . . . . . . . . . . . . . . . . . 22
395c95214142142854509945adf3293c0270e1c5Tinderbox User 5.4.4 Case D: A gateway connected to an IPv6-only ISP . . . 23
fd2597f75693a2279fdf588bd40dfe2407c42028Tinderbox User 6. Security Considerations . . . . . . . . . . . . . . . . . . . 24
395c95214142142854509945adf3293c0270e1c5Tinderbox User 6.1 RA Option . . . . . . . . . . . . . . . . . . . . . . . . 25
395c95214142142854509945adf3293c0270e1c5Tinderbox User 6.2 DHCPv6 Option . . . . . . . . . . . . . . . . . . . . . . 25
2eeb74d1cf5355dd98f6d507a10086e16bb08c4bTinderbox User 6.3 Well-known Anycast Addresses . . . . . . . . . . . . . . . 25
395c95214142142854509945adf3293c0270e1c5Tinderbox User 7. Contributors . . . . . . . . . . . . . . . . . . . . . . . . . 26
395c95214142142854509945adf3293c0270e1c5Tinderbox User 8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 28
395c95214142142854509945adf3293c0270e1c5Tinderbox User 9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 29
395c95214142142854509945adf3293c0270e1c5Tinderbox User 9.1 Normative References . . . . . . . . . . . . . . . . . . . 29
395c95214142142854509945adf3293c0270e1c5Tinderbox User 9.2 Informative References . . . . . . . . . . . . . . . . . . 29
395c95214142142854509945adf3293c0270e1c5Tinderbox User Author's Address . . . . . . . . . . . . . . . . . . . . . . . 31
fd2597f75693a2279fdf588bd40dfe2407c42028Tinderbox User A. Link-layer Multicast Acknowledgements for RA Option . . . . . 32
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395c95214142142854509945adf3293c0270e1c5Tinderbox User Intellectual Property and Copyright Statements . . . . . . . . 33
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2eeb74d1cf5355dd98f6d507a10086e16bb08c4bTinderbox User1. Introduction
fd2597f75693a2279fdf588bd40dfe2407c42028Tinderbox User Neighbor Discovery (ND) for IP Version 6 and IPv6 Stateless Address
395c95214142142854509945adf3293c0270e1c5Tinderbox User Autoconfiguration provide the ways to configure either fixed or
fd2597f75693a2279fdf588bd40dfe2407c42028Tinderbox User mobile nodes with one or more IPv6 addresses, default routes and some
395c95214142142854509945adf3293c0270e1c5Tinderbox User other parameters [3][4]. To support the access to additional
fd2597f75693a2279fdf588bd40dfe2407c42028Tinderbox User services in the Internet that are identified by a DNS name, such as a
395c95214142142854509945adf3293c0270e1c5Tinderbox User web server, the configuration of at least one recursive DNS server is
fd2597f75693a2279fdf588bd40dfe2407c42028Tinderbox User also needed for DNS name resolution.
395c95214142142854509945adf3293c0270e1c5Tinderbox User This document describes three approaches of recursive DNS server
395c95214142142854509945adf3293c0270e1c5Tinderbox User address configuration for IPv6 host: (a) RA option [8], (b) DHCPv6
fd2597f75693a2279fdf588bd40dfe2407c42028Tinderbox User option [5]-[7], and (c) Well-known anycast addresses for recursive
395c95214142142854509945adf3293c0270e1c5Tinderbox User DNS servers [9]. Also, it suggests the applicable scenarios for four
fd2597f75693a2279fdf588bd40dfe2407c42028Tinderbox User kinds of networks: (a) ISP network, (b) Enterprise network, (c) 3GPP
395c95214142142854509945adf3293c0270e1c5Tinderbox User network, and (d) Unmanaged network.
395c95214142142854509945adf3293c0270e1c5Tinderbox User This document is just an analysis of each possible approach, and does
fd2597f75693a2279fdf588bd40dfe2407c42028Tinderbox User not make any recommendation on a particular one or on a combination
395c95214142142854509945adf3293c0270e1c5Tinderbox User of particular ones. Some approaches may even not be adopted at all
4f9cb7bd58e2c0a7407fee3758ea265aee329ac6Tinderbox User as a result of further discussion.
395c95214142142854509945adf3293c0270e1c5Tinderbox User Therefore, the objective of this document is to help the audience
395c95214142142854509945adf3293c0270e1c5Tinderbox User select the approaches suitable for IPv6 host configuration of
395c95214142142854509945adf3293c0270e1c5Tinderbox User recursive DNS servers.
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659d063f23a35d77ad5826e6556d3137672bb937Tinderbox User2. Terminology
659d063f23a35d77ad5826e6556d3137672bb937Tinderbox User This document uses the terminology described in [3]-[9]. In
659d063f23a35d77ad5826e6556d3137672bb937Tinderbox User addition, a new term is defined below:
659d063f23a35d77ad5826e6556d3137672bb937Tinderbox User o Recursive DNS Server (RDNSS): A Recursive DNS Server is a name
2eeb74d1cf5355dd98f6d507a10086e16bb08c4bTinderbox User server that offers the recursive service of DNS name resolution.
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395c95214142142854509945adf3293c0270e1c5Tinderbox User3. IPv6 DNS Configuration Approaches
395c95214142142854509945adf3293c0270e1c5Tinderbox User In this section, the operational attributes of the three solutions
fd2597f75693a2279fdf588bd40dfe2407c42028Tinderbox User are described in detail.
395c95214142142854509945adf3293c0270e1c5Tinderbox User The RA approach is to define a new ND option called the RDNSS option
659d063f23a35d77ad5826e6556d3137672bb937Tinderbox User that contains a recursive DNS server address. Existing ND transport
fd2597f75693a2279fdf588bd40dfe2407c42028Tinderbox User mechanisms (i.e., advertisements and solicitations) are used. This
2eeb74d1cf5355dd98f6d507a10086e16bb08c4bTinderbox User works in the same way that nodes learn about routers and prefixes.
659d063f23a35d77ad5826e6556d3137672bb937Tinderbox User An IPv6 host can configure the IPv6 addresses of one or more RDNSSes
fd2597f75693a2279fdf588bd40dfe2407c42028Tinderbox User via RA message periodically sent by a router or solicited by a Router
61ab11c0ec845606f85452b2c9f2e223772aae00Tinderbox User Solicitation (RS) [8].
61ab11c0ec845606f85452b2c9f2e223772aae00Tinderbox User This approach needs RDNSS information to be configured in the routers
61ab11c0ec845606f85452b2c9f2e223772aae00Tinderbox User doing the advertisements. The configuration of RDNSS addresses can
61ab11c0ec845606f85452b2c9f2e223772aae00Tinderbox User be performed manually by an operator or other ways, such as automatic
f5c27ecceb6dcba6ad8b75172fe5f9823d7a6d42Tinderbox User configuration through a DHCPv6 client running on the router. When
fd2597f75693a2279fdf588bd40dfe2407c42028Tinderbox User advertising more than one RDNSS option, an RA message includes as
659d063f23a35d77ad5826e6556d3137672bb937Tinderbox User many RDNSS options as RDNSSes.
659d063f23a35d77ad5826e6556d3137672bb937Tinderbox User Through the ND protocol and RDNSS option along with a prefix
659d063f23a35d77ad5826e6556d3137672bb937Tinderbox User information option, an IPv6 host can perform its network
659d063f23a35d77ad5826e6556d3137672bb937Tinderbox User configuration of its IPv6 address and RDNSS simultaneously [3][4].
659d063f23a35d77ad5826e6556d3137672bb937Tinderbox User The RA option for RDNSS can be used on any network that supports the
659d063f23a35d77ad5826e6556d3137672bb937Tinderbox User However, it is worth noting that some link layers, such as Wireless
659d063f23a35d77ad5826e6556d3137672bb937Tinderbox User LANs (e.g., IEEE 802.11 a/b/g), do not support reliable multicast,
659d063f23a35d77ad5826e6556d3137672bb937Tinderbox User which means that they cannot guarantee the timely delivery of RA
659d063f23a35d77ad5826e6556d3137672bb937Tinderbox User messages [25]-[28]. This is discussed in Appendix A.
2eeb74d1cf5355dd98f6d507a10086e16bb08c4bTinderbox User The RA approach is useful in some mobile environments where the
659d063f23a35d77ad5826e6556d3137672bb937Tinderbox User addresses of the RDNSSes are changing because the RA option includes
659d063f23a35d77ad5826e6556d3137672bb937Tinderbox User a lifetime field that allows client to use RDNSSes nearer to the
659d063f23a35d77ad5826e6556d3137672bb937Tinderbox User client. This can be configured to a value that will require the
659d063f23a35d77ad5826e6556d3137672bb937Tinderbox User client to time out the entry and switch over to another RDNSS address
fd2597f75693a2279fdf588bd40dfe2407c42028Tinderbox User [8]. However, from the viewpoint of implementation, the lifetime
2eeb74d1cf5355dd98f6d507a10086e16bb08c4bTinderbox User field would seem to make matters a bit more complex. Instead of just
659d063f23a35d77ad5826e6556d3137672bb937Tinderbox User writing to a DNS configuration file, such as resolv.conf for the list
659d063f23a35d77ad5826e6556d3137672bb937Tinderbox User of RDNSS addresses, we have to have a daemon around (or a program
659d063f23a35d77ad5826e6556d3137672bb937Tinderbox User that is called at the defined intervals) that keeps monitoring the
659d063f23a35d77ad5826e6556d3137672bb937Tinderbox User lifetime of RDNSSes all the time.
659d063f23a35d77ad5826e6556d3137672bb937Tinderbox User The preference value of RDNSS, included in the RDNSS option, allows
659d063f23a35d77ad5826e6556d3137672bb937Tinderbox User IPv6 hosts to select primary RDNSS among several RDNSSes; this can be
659d063f23a35d77ad5826e6556d3137672bb937Tinderbox User used for the load balancing of RDNSSes [8].
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659d063f23a35d77ad5826e6556d3137672bb937Tinderbox User3.1.1 Advantages
659d063f23a35d77ad5826e6556d3137672bb937Tinderbox User The RA option for RDNSS has a number of advantages. These include:
659d063f23a35d77ad5826e6556d3137672bb937Tinderbox User 1. The RA option is an extension of existing ND/Autoconfig
fd2597f75693a2279fdf588bd40dfe2407c42028Tinderbox User mechanisms [3][4], and does not require a change in the base ND
659d063f23a35d77ad5826e6556d3137672bb937Tinderbox User 2. This approach, like ND, works well on a variety of link types
659d063f23a35d77ad5826e6556d3137672bb937Tinderbox User including point-to-point links, point-to-multipoint, and
659d063f23a35d77ad5826e6556d3137672bb937Tinderbox User multipoint-to-multipoint (i.e., Ethernet LANs), etc. RFC 2461
fd2597f75693a2279fdf588bd40dfe2407c42028Tinderbox User [3] states, however, that there may be some link types on which
2eeb74d1cf5355dd98f6d507a10086e16bb08c4bTinderbox User ND is not feasible; on such links, some other mechanisms will be
659d063f23a35d77ad5826e6556d3137672bb937Tinderbox User needed for DNS configuration.
659d063f23a35d77ad5826e6556d3137672bb937Tinderbox User 3. All of the information a host needs to run the basic Internet
659d063f23a35d77ad5826e6556d3137672bb937Tinderbox User applications such as the email, web, ftp, etc., can be obtained
659d063f23a35d77ad5826e6556d3137672bb937Tinderbox User with the addition of this option to ND and address
659d063f23a35d77ad5826e6556d3137672bb937Tinderbox User autoconfiguration. The use of a single mechanism is more
659d063f23a35d77ad5826e6556d3137672bb937Tinderbox User reliable and easier to provide than when the RDNSS information is
659d063f23a35d77ad5826e6556d3137672bb937Tinderbox User learned via another protocol mechanism. Debugging problems when
659d063f23a35d77ad5826e6556d3137672bb937Tinderbox User multiple protocol mechanisms are being used is harder and much
659d063f23a35d77ad5826e6556d3137672bb937Tinderbox User more complex.
395c95214142142854509945adf3293c0270e1c5Tinderbox User 4. This mechanism works over a broad range of scenarios and
395c95214142142854509945adf3293c0270e1c5Tinderbox User leverages IPv6 ND. This works well on links that support
395c95214142142854509945adf3293c0270e1c5Tinderbox User broadcast reliably (e.g., Ethernet LANs) but not necessarily on
395c95214142142854509945adf3293c0270e1c5Tinderbox User other links (e.g., Wireless LANs): Refer to Appendix A. Also,
fd2597f75693a2279fdf588bd40dfe2407c42028Tinderbox User this works well on links that are high performance (e.g.,
395c95214142142854509945adf3293c0270e1c5Tinderbox User Ethernet LANs) and low performance (e.g., Cellular networks). In
395c95214142142854509945adf3293c0270e1c5Tinderbox User the latter case, by combining the RDNSS information with the
fd2597f75693a2279fdf588bd40dfe2407c42028Tinderbox User other information in the RA, the host can learn all of the
395c95214142142854509945adf3293c0270e1c5Tinderbox User information needed to use most Internet applications, such as the
395c95214142142854509945adf3293c0270e1c5Tinderbox User web in a single packet. This not only saves bandwidth where this
395c95214142142854509945adf3293c0270e1c5Tinderbox User is an issue, but also minimizes the delay needed to learn the
395c95214142142854509945adf3293c0270e1c5Tinderbox User RDNSS information.
395c95214142142854509945adf3293c0270e1c5Tinderbox User 5. The RA approach could be used as a model for other similar types
2eeb74d1cf5355dd98f6d507a10086e16bb08c4bTinderbox User of configuration information. New RA options for other server
2eeb74d1cf5355dd98f6d507a10086e16bb08c4bTinderbox User addresses, such as NTP server address, that are common to all
2eeb74d1cf5355dd98f6d507a10086e16bb08c4bTinderbox User clients on a subnet would be easy to define.
2eeb74d1cf5355dd98f6d507a10086e16bb08c4bTinderbox User3.1.2 Disadvantages
395c95214142142854509945adf3293c0270e1c5Tinderbox User 1. ND is mostly implemented in the kernel of operating system.
659d063f23a35d77ad5826e6556d3137672bb937Tinderbox User Therefore, if ND supports the configuration of some additional
fd2597f75693a2279fdf588bd40dfe2407c42028Tinderbox User services, such as DNS servers, ND should be extended in the
395c95214142142854509945adf3293c0270e1c5Tinderbox UserJeong Expires November 6, 2005 [Page 8]
2eeb74d1cf5355dd98f6d507a10086e16bb08c4bTinderbox UserInternet-Draft IPv6 Host Configuration of DNS Server May 2005
395c95214142142854509945adf3293c0270e1c5Tinderbox User kernel, and complemented by a user-land process. DHCPv6,
fd2597f75693a2279fdf588bd40dfe2407c42028Tinderbox User however, has more flexibility for the extension of service
395c95214142142854509945adf3293c0270e1c5Tinderbox User discovery because it is an application layer protocol.
2eeb74d1cf5355dd98f6d507a10086e16bb08c4bTinderbox User 2. The current ND framework should be modified to facilitate the
c0cbdeedb5e119c640f098da1851cb1b9adcc739Tinderbox User synchronization between another ND cache for RDNSSes in the
c0cbdeedb5e119c640f098da1851cb1b9adcc739Tinderbox User kernel space and the DNS configuration file in the user space.
c0cbdeedb5e119c640f098da1851cb1b9adcc739Tinderbox User Because it is unacceptable to write and rewrite to the DNS
c0cbdeedb5e119c640f098da1851cb1b9adcc739Tinderbox User configuration file (e.g., resolv.conf) from the kernel, another
c0cbdeedb5e119c640f098da1851cb1b9adcc739Tinderbox User approach is needed. One simple approach to solve this is to have
fd2597f75693a2279fdf588bd40dfe2407c42028Tinderbox User a daemon listening to what the kernel conveys, and to have the
395c95214142142854509945adf3293c0270e1c5Tinderbox User daemon do these steps, but such a daemon is not needed with the
fd2597f75693a2279fdf588bd40dfe2407c42028Tinderbox User current ND framework.
fd2597f75693a2279fdf588bd40dfe2407c42028Tinderbox User 3. It is necessary to configure RDNSS addresses at least at one
395c95214142142854509945adf3293c0270e1c5Tinderbox User router on every link where this information needs to be
fd2597f75693a2279fdf588bd40dfe2407c42028Tinderbox User configured via the RA option.
395c95214142142854509945adf3293c0270e1c5Tinderbox User3.1.3 Observations
395c95214142142854509945adf3293c0270e1c5Tinderbox User The proposed RDNSS RA option along with the IPv6 ND and
fd2597f75693a2279fdf588bd40dfe2407c42028Tinderbox User Autoconfiguration allows a host to obtain all of the information it
395c95214142142854509945adf3293c0270e1c5Tinderbox User needs to access the basic Internet services like the web, email, ftp,
0ccb0e98c77a9b9636a036f8f64f5679a430aaf4Tinderbox User etc. This is preferable in the environments where hosts use RAs to
fd2597f75693a2279fdf588bd40dfe2407c42028Tinderbox User autoconfigure their addresses and all the hosts on the subnet share
395c95214142142854509945adf3293c0270e1c5Tinderbox User the same router and server addresses. If the configuration
659d063f23a35d77ad5826e6556d3137672bb937Tinderbox User information can be obtained from a single mechanism, it is preferable
fd2597f75693a2279fdf588bd40dfe2407c42028Tinderbox User because it does not add additional delay, and it uses a minimum of
395c95214142142854509945adf3293c0270e1c5Tinderbox User bandwidth. The environments like this include the homes, public
2eeb74d1cf5355dd98f6d507a10086e16bb08c4bTinderbox User cellular networks, and enterprise environments where no per host
395c95214142142854509945adf3293c0270e1c5Tinderbox User configuration is needed, but exclude public WLAN hot spots.
395c95214142142854509945adf3293c0270e1c5Tinderbox User DHCPv6 is preferable where it is being used for address configuration
395c95214142142854509945adf3293c0270e1c5Tinderbox User and if there is a need for host specific configuration [5]-[7]. The
659d063f23a35d77ad5826e6556d3137672bb937Tinderbox User environments like this are most likely to be the enterprise
fd2597f75693a2279fdf588bd40dfe2407c42028Tinderbox User environments where the local administration chooses to have per host
395c95214142142854509945adf3293c0270e1c5Tinderbox User configuration control.
2eeb74d1cf5355dd98f6d507a10086e16bb08c4bTinderbox User The observation section is based on what the proponents of each
2eeb74d1cf5355dd98f6d507a10086e16bb08c4bTinderbox User approach think makes a good overall solution.
395c95214142142854509945adf3293c0270e1c5Tinderbox User3.2 DHCPv6 Option
fd2597f75693a2279fdf588bd40dfe2407c42028Tinderbox User DHCPv6 [5] includes the "DNS Recursive Name Server" option, through
395c95214142142854509945adf3293c0270e1c5Tinderbox User which a host can obtain a list of IP addresses of recursive DNS
fd2597f75693a2279fdf588bd40dfe2407c42028Tinderbox UserJeong Expires November 6, 2005 [Page 9]
2eeb74d1cf5355dd98f6d507a10086e16bb08c4bTinderbox UserInternet-Draft IPv6 Host Configuration of DNS Server May 2005
395c95214142142854509945adf3293c0270e1c5Tinderbox User servers [7]. The DNS Recursive Name Server option carries a list of
395c95214142142854509945adf3293c0270e1c5Tinderbox User IPv6 addresses of RDNSSes to which the host may send DNS queries.
395c95214142142854509945adf3293c0270e1c5Tinderbox User The DNS servers are listed in the order of preference for use by the
659d063f23a35d77ad5826e6556d3137672bb937Tinderbox User DNS resolver on the host.
2eeb74d1cf5355dd98f6d507a10086e16bb08c4bTinderbox User The DNS Recursive Name Server option can be carried in any DHCPv6
659d063f23a35d77ad5826e6556d3137672bb937Tinderbox User Reply message, in response to either a Request or an Information
fd2597f75693a2279fdf588bd40dfe2407c42028Tinderbox User request message. Thus, the DNS Recursive Name Server option can be
395c95214142142854509945adf3293c0270e1c5Tinderbox User used either when DHCPv6 is used for address assignment, or when
3e240d6559605696cadf630668683708b18de871Tinderbox User DHCPv6 is used only for other configuration information as stateless
659d063f23a35d77ad5826e6556d3137672bb937Tinderbox User Stateless DHCPv6 can be deployed either using DHCPv6 servers running
fd2597f75693a2279fdf588bd40dfe2407c42028Tinderbox User on general-purpose computers, or on router hardware. Several router
2eeb74d1cf5355dd98f6d507a10086e16bb08c4bTinderbox User vendors currently implement stateless DHCPv6 servers. Deploying
659d063f23a35d77ad5826e6556d3137672bb937Tinderbox User stateless DHCPv6 in routers has the advantage that no special
fd2597f75693a2279fdf588bd40dfe2407c42028Tinderbox User hardware is required, and should work well for networks where DHCPv6
395c95214142142854509945adf3293c0270e1c5Tinderbox User is needed for very straightforward configuration of network devices.
fd2597f75693a2279fdf588bd40dfe2407c42028Tinderbox User However, routers can also act as DHCPv6 relay agents. In this case,
395c95214142142854509945adf3293c0270e1c5Tinderbox User the DHCPv6 server need not be on the router - it can be on a general
395c95214142142854509945adf3293c0270e1c5Tinderbox User purpose computer. This has the potential to give the operator of the
2eeb74d1cf5355dd98f6d507a10086e16bb08c4bTinderbox User DHCPv6 server more flexibility in how the DHCPv6 server responds to
395c95214142142854509945adf3293c0270e1c5Tinderbox User individual clients - clients can easily be given different
395c95214142142854509945adf3293c0270e1c5Tinderbox User configuration information based on their identity, or for any other
395c95214142142854509945adf3293c0270e1c5Tinderbox User reason. Nothing precludes adding this flexibility to a router, but
395c95214142142854509945adf3293c0270e1c5Tinderbox User generally in current practice, DHCP servers running on general-
395c95214142142854509945adf3293c0270e1c5Tinderbox User purpose hosts tend to have more configuration options than those that
659d063f23a35d77ad5826e6556d3137672bb937Tinderbox User are embedded in routers.
395c95214142142854509945adf3293c0270e1c5Tinderbox User DHCPv6 currently provides a mechanism for reconfiguring DHCPv6
2eeb74d1cf5355dd98f6d507a10086e16bb08c4bTinderbox User clients that use a stateful configuration assignment. To do this,
395c95214142142854509945adf3293c0270e1c5Tinderbox User the DHCPv6 server sends a Reconfigure message to the client. The
395c95214142142854509945adf3293c0270e1c5Tinderbox User client validates the Reconfigure message, and then contacts the
395c95214142142854509945adf3293c0270e1c5Tinderbox User DHCPv6 server to obtain updated configuration information. Using
395c95214142142854509945adf3293c0270e1c5Tinderbox User this mechanism, it is currently possible to propagate new
395c95214142142854509945adf3293c0270e1c5Tinderbox User configuration information to DHCPv6 clients as this information
fd2597f75693a2279fdf588bd40dfe2407c42028Tinderbox User The DHC Working Group is currently studying an additional mechanism
2eeb74d1cf5355dd98f6d507a10086e16bb08c4bTinderbox User through which configuration information, including the list of
11e9368a226272085c337e9e74b79808c16fbdbaTinderbox User RDNSSes, can be updated. The lifetime option for DHCPv6 [10] assigns
fd2597f75693a2279fdf588bd40dfe2407c42028Tinderbox User a lifetime to configuration information obtained through DHCPv6. At
eaaf00efc02fdd4965f747afb51f881ac5a389d2Tinderbox User the expiration of the lifetime, the host contacts the DHCPv6 server
0ccb0e98c77a9b9636a036f8f64f5679a430aaf4Tinderbox User to obtain updated configuration information, including the list of
fd2597f75693a2279fdf588bd40dfe2407c42028Tinderbox User RDNSSes. This lifetime gives the network administrator another
659d063f23a35d77ad5826e6556d3137672bb937Tinderbox User mechanism to configure hosts with new RDNSSes by controlling the time
659d063f23a35d77ad5826e6556d3137672bb937Tinderbox User at which the host refreshes the list.
9d557856c2a19ec95ee73245f60a92f8675cf5baTinderbox UserJeong Expires November 6, 2005 [Page 10]
659d063f23a35d77ad5826e6556d3137672bb937Tinderbox UserInternet-Draft IPv6 Host Configuration of DNS Server May 2005
659d063f23a35d77ad5826e6556d3137672bb937Tinderbox User The DHC Working Group has also discussed the possibility of defining
659d063f23a35d77ad5826e6556d3137672bb937Tinderbox User an extension to DHCPv6 that would allow the use of multicast to
fd2597f75693a2279fdf588bd40dfe2407c42028Tinderbox User provide configuration information to multiple hosts with a single
2eeb74d1cf5355dd98f6d507a10086e16bb08c4bTinderbox User DHCPv6 message. Because of the lack of deployment experience, the WG
659d063f23a35d77ad5826e6556d3137672bb937Tinderbox User has deferred consideration of multicast DHCPv6 configuration at this
2eeb74d1cf5355dd98f6d507a10086e16bb08c4bTinderbox User time. Experience with DHCPv4 has not identified a requirement for
659d063f23a35d77ad5826e6556d3137672bb937Tinderbox User multicast message delivery, even in large service provider networks
659d063f23a35d77ad5826e6556d3137672bb937Tinderbox User with tens of thousands of hosts that may initiate a DHCPv4 message
659d063f23a35d77ad5826e6556d3137672bb937Tinderbox User exchange simultaneously.
659d063f23a35d77ad5826e6556d3137672bb937Tinderbox User3.2.1 Advantages
2eeb74d1cf5355dd98f6d507a10086e16bb08c4bTinderbox User The DHCPv6 option for RDNSS has a number of advantages. These
2eeb74d1cf5355dd98f6d507a10086e16bb08c4bTinderbox User 1. DHCPv6 currently provides a general mechanism for conveying
659d063f23a35d77ad5826e6556d3137672bb937Tinderbox User network configuration information to clients. So configuring
659d063f23a35d77ad5826e6556d3137672bb937Tinderbox User DHCPv6 servers allows the network administrator to configure
659d063f23a35d77ad5826e6556d3137672bb937Tinderbox User RDNSSes along with the addresses of other network services, as
659d063f23a35d77ad5826e6556d3137672bb937Tinderbox User well as location-specific information like time zones.
9d557856c2a19ec95ee73245f60a92f8675cf5baTinderbox User 2. As a consequence, when the network administrator goes to
659d063f23a35d77ad5826e6556d3137672bb937Tinderbox User configure DHCPv6, all the configuration information can be
659d063f23a35d77ad5826e6556d3137672bb937Tinderbox User managed through a single service, typically with a single user
659d063f23a35d77ad5826e6556d3137672bb937Tinderbox User interface and a single configuration database.
659d063f23a35d77ad5826e6556d3137672bb937Tinderbox User 3. DHCPv6 allows for the configuration of a host with information
659d063f23a35d77ad5826e6556d3137672bb937Tinderbox User specific to that host, so that hosts on the same link can be
659d063f23a35d77ad5826e6556d3137672bb937Tinderbox User configured with different RDNSSes as well as with other
659d063f23a35d77ad5826e6556d3137672bb937Tinderbox User configuration information. This capability is important in some
659d063f23a35d77ad5826e6556d3137672bb937Tinderbox User network deployments such as service provider networks or WiFi hot
659d063f23a35d77ad5826e6556d3137672bb937Tinderbox User 4. A mechanism exists for extending DHCPv6 to support the
659d063f23a35d77ad5826e6556d3137672bb937Tinderbox User transmission of additional configuration that has not yet been
659d063f23a35d77ad5826e6556d3137672bb937Tinderbox User 5. Hosts that require other configuration information such as the
659d063f23a35d77ad5826e6556d3137672bb937Tinderbox User addresses of SIP servers and NTP servers are likely to need
2eeb74d1cf5355dd98f6d507a10086e16bb08c4bTinderbox User DHCPv6 for other configuration information.
659d063f23a35d77ad5826e6556d3137672bb937Tinderbox User 6. The specification for configuration of RDNSSes through DHCPv6 is
2eeb74d1cf5355dd98f6d507a10086e16bb08c4bTinderbox User available as an RFC. No new protocol extensions such as new
659d063f23a35d77ad5826e6556d3137672bb937Tinderbox User options are necessary.
2eeb74d1cf5355dd98f6d507a10086e16bb08c4bTinderbox User 7. Interoperability among independent implementations has been
659d063f23a35d77ad5826e6556d3137672bb937Tinderbox User demonstrated.
eaaf00efc02fdd4965f747afb51f881ac5a389d2Tinderbox UserJeong Expires November 6, 2005 [Page 11]
eaaf00efc02fdd4965f747afb51f881ac5a389d2Tinderbox UserInternet-Draft IPv6 Host Configuration of DNS Server May 2005
fd2597f75693a2279fdf588bd40dfe2407c42028Tinderbox User3.2.2 Disadvantages
fd2597f75693a2279fdf588bd40dfe2407c42028Tinderbox User The DHCPv6 option for RDNSS has a few disadvantages. These include:
2eeb74d1cf5355dd98f6d507a10086e16bb08c4bTinderbox User 1. Update currently requires message from server (however, see
395c95214142142854509945adf3293c0270e1c5Tinderbox User 2. Because DNS information is not contained in RA messages, the host
fd2597f75693a2279fdf588bd40dfe2407c42028Tinderbox User must receive two messages from the router, and must transmit at
395c95214142142854509945adf3293c0270e1c5Tinderbox User least one message to the router. On networks where bandwidth is
2eeb74d1cf5355dd98f6d507a10086e16bb08c4bTinderbox User at a premium, this is a disadvantage, although on most networks
2eeb74d1cf5355dd98f6d507a10086e16bb08c4bTinderbox User it is not a practical concern.
395c95214142142854509945adf3293c0270e1c5Tinderbox User 3. Increased latency for initial configuration - in addition to
fd2597f75693a2279fdf588bd40dfe2407c42028Tinderbox User waiting for an RA message, the client must now exchange packets
395c95214142142854509945adf3293c0270e1c5Tinderbox User with a DHCPv6 server; even if it is locally installed on a
395c95214142142854509945adf3293c0270e1c5Tinderbox User router, this will slightly extend the time required to configure
fd2597f75693a2279fdf588bd40dfe2407c42028Tinderbox User the client. For clients that are moving rapidly from one network
395c95214142142854509945adf3293c0270e1c5Tinderbox User to another, this will be a disadvantage.
2eeb74d1cf5355dd98f6d507a10086e16bb08c4bTinderbox User3.2.3 Observations
395c95214142142854509945adf3293c0270e1c5Tinderbox User In the general case, on general-purpose networks, stateless DHCPv6
395c95214142142854509945adf3293c0270e1c5Tinderbox User provides significant advantages and no significant disadvantages.
fd2597f75693a2279fdf588bd40dfe2407c42028Tinderbox User Even in the case where bandwidth is at a premium and low latency is
fd2597f75693a2279fdf588bd40dfe2407c42028Tinderbox User desired, if hosts require other configuration information in addition
395c95214142142854509945adf3293c0270e1c5Tinderbox User to a list of RDNSSes or if hosts must be configured selectively,
fd2597f75693a2279fdf588bd40dfe2407c42028Tinderbox User those hosts will use DHCPv6 and the use of the DHCPv6 DNS recursive
395c95214142142854509945adf3293c0270e1c5Tinderbox User name server option will be advantageous.
395c95214142142854509945adf3293c0270e1c5Tinderbox User However, we are aware of some applications where it would be
395c95214142142854509945adf3293c0270e1c5Tinderbox User preferable to put the RDNSS information into an RA packet; for
fd2597f75693a2279fdf588bd40dfe2407c42028Tinderbox User example, on a cell phone network, where bandwidth is at a premium and
395c95214142142854509945adf3293c0270e1c5Tinderbox User extremely low latency is desired. The final DNS configuration draft
395c95214142142854509945adf3293c0270e1c5Tinderbox User should be written so as to allow these special applications to be
fd2597f75693a2279fdf588bd40dfe2407c42028Tinderbox User handled using DNS information in the RA packet.
395c95214142142854509945adf3293c0270e1c5Tinderbox User3.3 Well-known Anycast Addresses
395c95214142142854509945adf3293c0270e1c5Tinderbox User Anycast uses the same routing system as unicast [11]. However,
395c95214142142854509945adf3293c0270e1c5Tinderbox User administrative entities are local ones. The local entities may
395c95214142142854509945adf3293c0270e1c5Tinderbox User accept unicast routes (including default routes) to anycast servers
395c95214142142854509945adf3293c0270e1c5Tinderbox User from adjacent entities. The administrative entities should not
2eeb74d1cf5355dd98f6d507a10086e16bb08c4bTinderbox User advertise their peers routes to their internal anycast servers, if
395c95214142142854509945adf3293c0270e1c5Tinderbox User they want to prohibit external access from some peers to the servers.
395c95214142142854509945adf3293c0270e1c5Tinderbox User If some advertisement is inevitable (such as the case with default
395c95214142142854509945adf3293c0270e1c5Tinderbox User routes), the packets to the servers should be blocked at the boundary
fd2597f75693a2279fdf588bd40dfe2407c42028Tinderbox UserJeong Expires November 6, 2005 [Page 12]
fd2597f75693a2279fdf588bd40dfe2407c42028Tinderbox UserInternet-Draft IPv6 Host Configuration of DNS Server May 2005
395c95214142142854509945adf3293c0270e1c5Tinderbox User of the entities. Thus, for this anycast, not only unicast routing
395c95214142142854509945adf3293c0270e1c5Tinderbox User but also unicast ND protocols can be used as is.
395c95214142142854509945adf3293c0270e1c5Tinderbox User First of all, the well-known anycast addresses approach is much
395c95214142142854509945adf3293c0270e1c5Tinderbox User different from that discussed at IPv6 Working Group in the past [9].
395c95214142142854509945adf3293c0270e1c5Tinderbox User It should be noted that "anycast" in this memo is simpler than that
fd2597f75693a2279fdf588bd40dfe2407c42028Tinderbox User of RFC 1546 [11] and RFC 3513 [12] where it is assumed to be
2eeb74d1cf5355dd98f6d507a10086e16bb08c4bTinderbox User prohibited to have multiple servers on a single link sharing an
395c95214142142854509945adf3293c0270e1c5Tinderbox User anycast address. That is, on a link, an anycast address is assumed
fd2597f75693a2279fdf588bd40dfe2407c42028Tinderbox User to be unique. DNS clients today already have redundancy by having
395c95214142142854509945adf3293c0270e1c5Tinderbox User multiple well-known anycast addresses configured as RDNSS addresses.
fd2597f75693a2279fdf588bd40dfe2407c42028Tinderbox User There is no point in having multiple RDNSSes sharing an anycast
395c95214142142854509945adf3293c0270e1c5Tinderbox User address on a single link.
395c95214142142854509945adf3293c0270e1c5Tinderbox User The approach with well-known anycast addresses is to set multiple
fd2597f75693a2279fdf588bd40dfe2407c42028Tinderbox User well-known anycast addresses in clients' resolver configuration files
395c95214142142854509945adf3293c0270e1c5Tinderbox User from the beginning, say, as factory default. Thus, there is no
fd2597f75693a2279fdf588bd40dfe2407c42028Tinderbox User transport mechanism and no packet format [9].
2eeb74d1cf5355dd98f6d507a10086e16bb08c4bTinderbox User An anycast address is an address shared by multiple servers (in this
395c95214142142854509945adf3293c0270e1c5Tinderbox User case, the servers are RDNSSes). A request from a client to the
395c95214142142854509945adf3293c0270e1c5Tinderbox User anycast address is routed to a server selected by the routing system.
fd2597f75693a2279fdf588bd40dfe2407c42028Tinderbox User However, it is a bad idea to mandate "site" boundary on anycast
395c95214142142854509945adf3293c0270e1c5Tinderbox User addresses, because most users just do not have their own servers and
fd2597f75693a2279fdf588bd40dfe2407c42028Tinderbox User want to access their ISPs' across their site boundaries. Larger
395c95214142142854509945adf3293c0270e1c5Tinderbox User sites may also depend on their ISPs or may have their own RDNSSes
395c95214142142854509945adf3293c0270e1c5Tinderbox User within "site" boundaries.
395c95214142142854509945adf3293c0270e1c5Tinderbox User3.3.1 Advantages
395c95214142142854509945adf3293c0270e1c5Tinderbox User The basic advantage of the well-known addresses approach is that it
fd2597f75693a2279fdf588bd40dfe2407c42028Tinderbox User uses no transport mechanism. Thus,
395c95214142142854509945adf3293c0270e1c5Tinderbox User 1. There is no delay to get the response and no further delay by
fd2597f75693a2279fdf588bd40dfe2407c42028Tinderbox User packet losses.
395c95214142142854509945adf3293c0270e1c5Tinderbox User 2. The approach can be combined with any other configuration
395c95214142142854509945adf3293c0270e1c5Tinderbox User mechanisms, such as the RA-based approach and DHCP based
395c95214142142854509945adf3293c0270e1c5Tinderbox User approach, as well as the factory default configuration.
395c95214142142854509945adf3293c0270e1c5Tinderbox User 3. The approach works over any environment where DNS works.
395c95214142142854509945adf3293c0270e1c5Tinderbox User Another advantage is that the approach needs to configure DNS servers
395c95214142142854509945adf3293c0270e1c5Tinderbox User as a router, but nothing else. Considering that DNS servers do need
395c95214142142854509945adf3293c0270e1c5Tinderbox User configuration, the amount of overall configuration effort is
fd2597f75693a2279fdf588bd40dfe2407c42028Tinderbox User proportional to the number of the DNS servers and scales linearly.
2eeb74d1cf5355dd98f6d507a10086e16bb08c4bTinderbox User It should be noted that, in the simplest case where a subscriber to
395c95214142142854509945adf3293c0270e1c5Tinderbox User an ISP does not have any DNS server, the subscriber naturally
fd2597f75693a2279fdf588bd40dfe2407c42028Tinderbox UserJeong Expires November 6, 2005 [Page 13]
fd2597f75693a2279fdf588bd40dfe2407c42028Tinderbox UserInternet-Draft IPv6 Host Configuration of DNS Server May 2005
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein accesses DNS servers of the ISP even though the subscriber and the
fd2597f75693a2279fdf588bd40dfe2407c42028Tinderbox User ISP do nothing and there is no protocol to exchange DNS server
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein information between the subscriber and the ISP.
fd2597f75693a2279fdf588bd40dfe2407c42028Tinderbox User3.3.2 Disadvantages
fd2597f75693a2279fdf588bd40dfe2407c42028Tinderbox User Well-known anycast addresses approach requires that DNS servers (or
fd2597f75693a2279fdf588bd40dfe2407c42028Tinderbox User routers near it as a proxy) act as routers to advertise their anycast
fd2597f75693a2279fdf588bd40dfe2407c42028Tinderbox User addresses to the routing system, which requires some configuration
fd2597f75693a2279fdf588bd40dfe2407c42028Tinderbox User (see the last paragraph of the previous section on the scalability of
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein3.3.3 Observations
fd2597f75693a2279fdf588bd40dfe2407c42028Tinderbox User If other approaches are used in addition, the well-known anycast
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein addresses should also be set in RA or DHCP configuration files to
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein reduce the configuration effort of users.
the address of the RDNSS. Before IP-based services (e.g., web
manually in his/her UE. The use of well-known addresses is briefly
UEs, e.g., WLAN, and 3GPP-specific DNS configuration mechanisms (such
RA message sent by its default router (GGSN), i.e., RDNSS option for
than RDNSS addresses, e.g., SIP server addresses.
draft-jeong-dnsop-ipv6-dns-discovery-04.txt (Work in Progress),
draft-ohta-preconfigured-dns-01.txt (Work in Progress),
Option for DHCPv6", draft-ietf-dhc-lifetime-03.txt (Work in
draft-ietf-v6ops-ent-scenarios-05.txt (Work in Progress),
Networks", draft-ietf-v6ops-3gpp-analysis-11.txt (Work in
[25] ANSI/IEEE Std 802.11, "Part 11: Wireless LAN Medium Access
[28] IEEE P802.11g/D8.2, "Part 11: Wireless LAN Medium Access
draft-ietf-ipv6-ra-mo-flags-01.txt (Work in Progress),
ETRI/Department of Computer Science and Engineering
(STA), which is specific to CSMA/CA of WLAN, such as IEEE 802.11
"AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS