draft-ietf-dnsop-respsize-09.txt   draft-ietf-dnsop-respsize-10.txt 
Internet Engineering Task Force P. Vixie Internet Engineering Task Force P. Vixie
Internet-Draft Internet Systems Consortium Internet-Draft Internet Systems Consortium
Intended status: Informational A. Kato Intended status: Informational A. Kato
Expires: June 20, 2008 The University of Tokyo/WIDE Expires: August 27, 2008 The University of Tokyo/WIDE
Project Project
December 18, 2007 February 24, 2008
DNS Referral Response Size Issues DNS Referral Response Size Issues
draft-ietf-dnsop-respsize-09 draft-ietf-dnsop-respsize-10
Status of this Memo Status of this Memo
By submitting this Internet-Draft, each author represents that any By submitting this Internet-Draft, each author represents that any
applicable patent or other IPR claims of which he or she is aware applicable patent or other IPR claims of which he or she is aware
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Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
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This Internet-Draft will expire on June 20, 2008. This Internet-Draft will expire on August 27, 2008.
Copyright Notice Copyright Notice
Copyright (C) The IETF Trust (2007). Copyright (C) The IETF Trust (2008).
Abstract Abstract
With a mandated default minimum maximum UDP message size of 512 With a mandated default minimum maximum UDP message size of 512
octets, the DNS protocol presents some special problems for zones octets, the DNS protocol presents some special problems for zones
wishing to expose a moderate or high number of authority servers (NS wishing to expose a moderate or high number of authority servers (NS
RRs). This document explains the operational issues caused by, or RRs). This document explains the operational issues caused by, or
related to this response size limit, and suggests ways to optimize related to this response size limit, and suggests ways to optimize
the use of this limited space. Guidance is offered to DNS server the use of this limited space. Guidance is offered to DNS server
implementors and to DNS zone operators. implementors and to DNS zone operators.
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responses by mutual agreement of the requester and responder (see responses by mutual agreement of the requester and responder (see
[RFC2671] 2.3, 4.5), and it is recommended to support EDNS. The 512 [RFC2671] 2.3, 4.5), and it is recommended to support EDNS. The 512
octets UDP message size limit will remain in practical effect until octets UDP message size limit will remain in practical effect until
virtually all DNS servers and resolvers support EDNS. virtually all DNS servers and resolvers support EDNS.
Since DNS responses include a copy of the request, the space Since DNS responses include a copy of the request, the space
available for response data is somewhat less than the full 512 available for response data is somewhat less than the full 512
octets. Negative responses are quite small, but for positive and octets. Negative responses are quite small, but for positive and
referral responses, every octet must be carefully and sparingly referral responses, every octet must be carefully and sparingly
allocated. While the response size of positive responses is also a allocated. While the response size of positive responses is also a
concern[RFC3226], this document specifically addresses referral concern in [RFC3226], this document specifically addresses referral
response size. response size.
1.2. Requirements Language
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 [RFC2119].
2. Delegation Details 2. Delegation Details
2.1. Relevant Protocol Elements 2.1. Relevant Protocol Elements
A delegation response will include the following elements: A delegation response will include the following elements:
Header Section: fixed length (12 octets) Header Section: fixed length (12 octets)
Question Section: original query (name, class, type) Question Section: original query (name, class, type)
Answer Section: empty, or a CNAME/DNAME chain Answer Section: empty, or a CNAME/DNAME chain
Authority Section: NS RRset (nameserver names) Authority Section: NS RRset (nameserver names)
Additional Section: A and AAAA RRsets (nameserver addresses) Additional Section: A and AAAA RRsets (nameserver addresses)
If the total size of the UDP response exceeds 512 octets or If the total size of the UDP response exceeds 512 octets or the size
advertised size in EDNS, and if the data that does not fit was advertised in EDNS, and if the data that does not fit was "required",
"required", then the TC bit will be set (indicating truncation). then the TC bit will be set (indicating truncation). This will
This will usually cause the requester to retry using TCP, depending usually cause the requester to retry using TCP, depending on what
on what information was desired and what information was omitted. information was desired and what information was omitted. For
For example, truncation in the authority section is of no interest to example, truncation in the authority section is of no interest to a
a stub resolver who only plans to consume the answer section. If a stub resolver who only plans to consume the answer section. If a
retry using TCP is needed, the total cost of the transaction is much retry using TCP is needed, the total cost of the transaction is much
higher. See [RFC1123] 6.1.3.2 for details on the requirement that higher. See [RFC1123] 6.1.3.2 for details on the requirement that
UDP be attempted before falling back to TCP. UDP be attempted before falling back to TCP.
RRsets are never sent partially unless the TC bit is set to indicate RRsets are never sent partially unless the TC bit is set to indicate
truncation. When the TC bit is set, the final apparent RRset in the truncation. When the TC bit is set, the final apparent RRset in the
final non-empty section must be considered "possibly damaged" (see final non-empty section must be considered "possibly damaged" (see
[RFC1035] 6.2, [RFC2181] 9). [RFC1035] 6.2, [RFC2181] 9).
With or without truncation, the glue present in the additional data With or without truncation, the glue present in the additional data
section should be considered "possibly incomplete", and requesters section should be considered "possibly incomplete", and requesters
should be prepared to re-query for any damaged or missing RRsets. should be prepared to re-query for any damaged or missing RRsets.
Note that truncation of the additional data section might not be Note that truncation of the additional data section might not be
signaled via the TC bit since additional data is often optional (see signaled via the TC bit since additional data is often optional (see
discussion in [RFC4472] B). discussion in [RFC4472] B).
DNS label compression allows the component labels of a domain name to DNS label compression allows the component labels of a domain name to
be instantiated exactly once per DNS message, and then referenced be instantiated exactly once per DNS message, and then referenced
with a two-octet "pointer" from other locations in that same DNS with a two-octet "pointer" from other locations in that same DNS
message (see [RFC1035] 4.1.4). If all nameserver names in a message message (see [RFC1035] 4.1.4). If all nameserver names in a message
share a common parent (for example, all ending in ".ROOT- share a common parent (for example, all of them are in "ROOT-
SERVERS.NET"), then more space will be available for incompressible SERVERS.NET." zone), then more space will be available for
data (such as nameserver addresses). incompressible data (such as nameserver addresses).
The query name can be as long as 255 octets of network data. In this The query name can be as long as 255 octets of network data. In this
worst case scenario, the question section will be 259 octets in size, worst case scenario, the question section will be 259 octets in size,
which would leave only 240 octets for the authority and additional which would leave only 240 octets for the authority and additional
sections (after deducting 12 octets for the fixed length header) in a sections (after deducting 12 octets for the fixed length header) in a
referral. referral.
2.2. Advice to Zone Owners 2.2. Advice to Zone Owners
Average and maximum question section sizes can be predicted by the Average and maximum question section sizes can be predicted by the
zone owner, since they will know what names actually exist, and can zone owner, since they will know what names actually exist and can
measure which ones are queried for most often. Note that if the zone measure which ones are queried for most often. Note that if the zone
contains any wildcards, it is possible for maximum length queries to contains any wildcards, it is possible for maximum length queries to
require positive responses, but that it is reasonable to expect require positive responses, but that it is reasonable to expect
truncation and TCP retry in that case. For cost and performance truncation and TCP retry in that case. For cost and performance
reasons, the majority of requests should be satisfied without reasons, the majority of requests should be satisfied without
truncation or TCP retry. truncation or TCP retry.
Some queries to non-existing names can be large, but this is not a Some queries to non-existing names can be large, but this is not a
problem because negative responses need not contain any answer, problem because negative responses need not contain any answer,
authority or additional records. See [RFC2308] 2.1 for more authority or additional records. See [RFC2308] 2.1 for more
information about the format of negative responses. information about the format of negative responses.
The minimum useful number of name servers is two, for redundancy (see The minimum useful number of name servers is two, for redundancy (see
[RFC1034] 4.1). A zone's name servers should be reachable by all IP [RFC1034] 4.1). A zone's name servers should be reachable by all IP
protocols versions (e.g., IPv4 and IPv6) in common use. As long as protocols versions (e.g., IPv4 and IPv6) in common use. As long as
the servers are well managed, the server serving IPv6 might be the servers are well managed, the server serving IPv6 might be
different from the server serving IPv4 sharing the same server name. different from the server serving IPv4 sharing the same server name.
It is important to ensure that a zone should have servers reachable It is important to ensure that a zone has servers reachable by all IP
by all IP protocol in common use (e.g., IPv4 and IPv6). protocol in common use (e.g., IPv4 and IPv6).
The best case is no truncation at all. This is because many The best case is no truncation at all. This is because many
requesters will retry using TCP immediately, or will automatically requesters will retry using TCP immediately, or will automatically
requery for RRsets that are possibly truncated, without considering requery for RRsets that are possibly truncated, without considering
whether the omitted data was actually necessary. whether the omitted data was actually necessary.
Anycasting[RFC3258] is a useful tool for performance and reliability Anycasting[RFC3258] is a useful tool for performance and reliability
without increasing the size of referral response. without increasing the size of referral responses.
While it is irrelevant to the response size issue, all zones have to While it is irrelevant to the response size issue, all zones have to
be served via IPv4 as well to avoid name space be served via IPv4 as well to avoid name space fragmentation
fragmentation[RFC3901]. [RFC3901].
2.3. Advice to Server Implementors 2.3. Advice to Server Implementors
Each NS RR for a zone will add 12 fixed octets (name, type, class, Each NS RR for a zone will add 12 fixed octets (name, type, class,
ttl, and rdlen) plus 2 to 255 variable octets (for the NSDNAME). ttl, and rdlen) plus 2 to 255 variable octets (for the NSDNAME).
Each A RR will require 16 octets, and each AAAA RR will require 28 Each A RR will require 16 octets, and each AAAA RR will require 28
octets. octets.
While DNS distinguishes between necessary and optional resource While DNS distinguishes between necessary and optional resource
records, this distinction is according to protocol elements necessary records, this distinction is according to protocol elements necessary
to signify facts, and takes no official notice of protocol content to signify facts, and takes no official notice of protocol content
necessary to ensure correct operation. For example, a nameserver necessary to ensure correct operation. For example, a nameserver
name that is in or below the zone cut being described by a delegation name that is in or below the zone cut being described by a delegation
is "necessary content", since there is no way to reach that zone is "necessary content", since there is no way to reach that zone
unless the parent zone's delegation includes "glue records" unless the parent zone's delegation includes "glue records"
describing that name server's addresses. describing that name server's addresses.
Recall that the TC bit is only set when the required RRset can not be Recall that the TC bit is only set when a required RRset can not be
included in its entirety (see [RFC2181] 9). Even when some of the included in its entirety (see [RFC2181] 9). Even when some of the
RRsets to be included in the additional section are not fit in the RRsets to be included in the additional section don't fit in the
response size, the TC bit isn't set. These RRsets may be important response size, the TC bit isn't set. These RRsets may be important
for a referral. Some DNS implementations try to resolve these for a referral. Some DNS implementations try to resolve these
missing glue records separately which will introduce extra queries missing glue records separately which will introduce extra queries
and extra time to resolve a given name. and extra time to resolve a given name.
A delegation response should prioritize glue records as follows. A delegation response should prioritize glue records as follows.
first: first:
All glue RRsets for one name server whose name is in or below the All glue RRsets for one name server whose name is in or below the
zone being delegated, or which has multiple address RRsets zone being delegated, or which has multiple address RRsets
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Alternate between adding all glue RRsets for any name servers Alternate between adding all glue RRsets for any name servers
whose names are in or below the zone being delegated, and all whose names are in or below the zone being delegated, and all
glue RRsets for any name servers who have multiple address RRsets glue RRsets for any name servers who have multiple address RRsets
(currently A and AAAA); (currently A and AAAA);
thence: thence:
All other glue RRsets, in any order. All other glue RRsets, in any order.
Whenever there are multiple candidates for a position in this Whenever there are multiple candidates for a position in this
priority scheme, one should be chosen on a round-robin or fully priority scheme, one should be chosen on a round-robin or fully
random basis. The goal of this priority scheme is to offer random basis. The goal of this priority scheme is to offer
"necessary" glue first, avoiding silent truncation for this glue if "necessary" glue first to fill into the response if possible.
possible.
If any "necessary content" is silently truncated, then it is If any "necessary content" is not able to fill in the response, then
advisable that the TC bit be set in order to force a TCP retry, it is advisable that the TC bit be set in order to force a TCP retry,
rather than have the zone be unreachable. Note that a parent rather than have the zone be unreachable. Note that a parent
server's proper response to a query for in-child glue or below-child server's proper response to a query for in-child glue or below-child
glue is a referral rather than an answer, and that this referral must glue is a referral rather than an answer, and that this referral must
be able to contain the in-child or below-child glue, and that in be able to contain the in-child or below-child glue, and that in
outlying cases, only EDNS or TCP will be large enough to contain that outlying cases, only EDNS or TCP will be large enough to contain that
data. data.
3. Analysis 3. Analysis
An instrumented protocol trace of a best case delegation response is An instrumented protocol trace of a best case delegation response is
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K.GTLD-SERVERS.NET. 86400 A 192.52.178.30 ;; @480 K.GTLD-SERVERS.NET. 86400 A 192.52.178.30 ;; @480
L.GTLD-SERVERS.NET. 86400 A 192.41.162.30 ;; @496 L.GTLD-SERVERS.NET. 86400 A 192.41.162.30 ;; @496
M.GTLD-SERVERS.NET. 86400 A 192.55.83.30 ;; @512 M.GTLD-SERVERS.NET. 86400 A 192.55.83.30 ;; @512
;; MSG SIZE sent: 80 rcvd: 512 ;; MSG SIZE sent: 80 rcvd: 512
Figure 1 Figure 1
For longer query names, the number of address records supplied will For longer query names, the number of address records supplied will
be lower. Furthermore, it is only by using a common parent name be lower. Furthermore, it is only by using a common parent name
(which is "GTLD-SERVERS.NET" in this example) that all 13 addresses (which is "GTLD-SERVERS.NET." in this example) that all 13 addresses
are able to fit, due to the use of DNS compression pointers in the are able to fit, due to the use of DNS compression pointers in the
last 12 occurrences of the parent domain name. The following outputs last 12 occurrences of the parent domain name. The outputs from the
shown in Figure 2 and Figure 3 from a response simulator in response simulator in Appendix A (written in perl [PERL]) shown in
Appendix A written in perl[PERL] demonstrate these properties. Figure 2 and Figure 3 demonstrate these properties.
% perl respsize.pl a.dns.br b.dns.br c.dns.br d.dns.br % perl respsize.pl a.dns.br b.dns.br c.dns.br d.dns.br
a.dns.br requires 10 bytes a.dns.br requires 10 bytes
b.dns.br requires 4 bytes b.dns.br requires 4 bytes
c.dns.br requires 4 bytes c.dns.br requires 4 bytes
d.dns.br requires 4 bytes d.dns.br requires 4 bytes
# of NS: 4 # of NS: 4
For maximum size query (255 byte): For maximum size query (255 byte):
only A is considered: # of A is 4 (green) only A is considered: # of A is 4 (green)
A and AAAA are considered: # of A+AAAA is 3 (yellow) A and AAAA are considered: # of A+AAAA is 3 (yellow)
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A and AAAA are considered: # of A+AAAA is 4 (green) A and AAAA are considered: # of A+AAAA is 4 (green)
preferred-glue A is assumed: # of A is 4, # of AAAA is 4 (green) preferred-glue A is assumed: # of A is 4, # of AAAA is 4 (green)
Figure 3 Figure 3
Here we use the term "green" if all address records could fit, or Here we use the term "green" if all address records could fit, or
"yellow" if two or more could fit, or "orange" if only one could fit, "yellow" if two or more could fit, or "orange" if only one could fit,
or "red" if no address record could fit. It's clear that without a or "red" if no address record could fit. It's clear that without a
common parent for nameserver names, much space would be lost. For common parent for nameserver names, much space would be lost. For
these examples we use an average/common name size of 15 octets, these examples we use an average/common name size of 15 octets,
befitting our assumption of GTLD-SERVERS.NET as our common parent befitting our assumption of "GTLD-SERVERS.NET." as our common parent
name. name.
We're assuming a medium query name size of 64 since that is the We're assuming a medium query name size of 64 since that is the
typical size seen in trace data at the time of this writing. If typical size seen in trace data at the time of this writing. If
Internationalized Domain Name (IDN) or any other technology which Internationalized Domain Name (IDN) or any other technology which
results in larger query names be deployed significantly in advance of results in larger query names be deployed significantly in advance of
EDNS, then new measurements and new estimates will have to be made. EDNS, then new measurements and new estimates will have to be made.
4. Conclusions 4. Conclusions
The current practice of giving all nameserver names a common parent The current practice of giving all nameserver names a common parent
(such as GTLD-SERVERS.NET or ROOT-SERVERS.NET) saves space in DNS (such as "GTLD-SERVERS.NET." or "ROOT-SERVERS.NET.") saves space in
responses and allows for more nameservers to be enumerated than would DNS responses and allows for more nameservers to be enumerated than
otherwise be possible, since the common parent domain name only would otherwise be possible, since the common parent domain name only
appears once in a DNS message and is referred to via "compression appears once in a DNS message and is referred to via "compression
pointers" thereafter. pointers" thereafter.
If all nameserver names for a zone share a common parent, then it is If all nameserver names for a zone share a common parent, then it is
operationally advisable to make all servers for the zone thus served operationally advisable to make all servers for the zone thus served
also be authoritative for the zone of that common parent. For also be authoritative for the zone of that common parent. For
example, the root name servers (?.ROOT-SERVERS.NET) can answer example, the root name servers (?.ROOT-SERVERS.NET.) can answer
authoritatively for the ROOT-SERVERS.NET zone. This is to ensure authoritatively for the ROOT-SERVERS.NET. zone. This is to ensure
that the zone's servers always have the zone's nameservers' glue that the zone's servers always have the zone's nameservers' glue
available when delegating, and will be able to respond with answers available when delegating, and will be able to respond with answers
rather than referrals if a requester who wants that glue comes back rather than referrals if a requester who wants that glue comes back
asking for it. In this case the name server will likely be a asking for it. In this case the name server will likely be a
"stealth server" -- authoritative but unadvertised in the glue zone's "stealth server" -- authoritative but unadvertised in the glue zone's
NS RRset. See [RFC1996] 2 for more information about stealth NS RRset. See [RFC1996] 2 for more information about stealth
servers. servers.
Thirteen (13) is the effective maximum number of nameserver names Thirteen (13) is the effective maximum number of nameserver names
usable with traditional (non-extended) DNS, assuming a common parent usable with traditional (non-extended) DNS, assuming a common parent
domain name, and given that implicit referral response truncation is domain name, and given that implicit referral response truncation is
undesirable in the average case. undesirable in the average case.
More than one address records in a protocol family per a server is More than one address record in a protocol family per server is
inadvisable since the necessary glue RRsets (A or AAAA) are inadvisable since the necessary glue RRsets (A or AAAA) are
atomically indivisible, and will be larger than a single resource atomically indivisible, and will be larger than a single resource
record. Larger RRsets are more likely to lead to or encounter record. Larger RRsets are more likely to lead to or encounter
truncation. truncation.
More than one address records across protocol families is less likely More than one address record across protocol families is less likely
to lead to or encounter truncation, partly because multiprotocol to lead to or encounter truncation, partly because multiprotocol
clients, which are required to handle larger RRsets such as AAAA RRs, clients, which are required to handle larger RRsets such as AAAA RRs,
are more likely to speak EDNS which can use a larger UDP response are more likely to speak EDNS which can use a larger UDP response
size limit, and partly because the resource records (A and AAAA) are size limit, and partly because the resource records (A and AAAA) are
in different RRsets and are therefore divisible from each other. in different RRsets and are therefore divisible from each other.
Name server names which are at or below the zone they serve are more Name server names which are at or below the zone they serve are more
sensitive to referral response truncation, and glue records for them sensitive to referral response truncation, and glue records for them
should be considered "more important" than other glue records, in the should be considered "more important" than other glue records, in the
assembly of referral responses. assembly of referral responses.
If a zone is served by thirteen (13) name servers having a common If a zone is served by thirteen (13) name servers having a common
parent name (such as ?.ROOT-SERVERS.NET) and each such name server parent name (such as ?.ROOT-SERVERS.NET.) and each such name server
has a single address record in some protocol family (e.g., an A RR), has a single address record in some protocol family (e.g., an A RR),
then all thirteen name servers or any subset thereof could have then all thirteen name servers or any subset thereof could have
address records in a second protocol family by adding a second address records in a second protocol family by adding a second
address record (e.g., an AAAA RR) without reducing the reachability address record (e.g., an AAAA RR) without reducing the reachability
of the zone thus served. of the zone thus served.
5. Security Considerations 5. Security Considerations
The recommendations contained in this document have no known security The recommendations contained in this document have no known security
implications. implications.
6. IANA Considerations 6. IANA Considerations
This document does not call for changes or additions to any IANA This document does not call for changes or additions to any IANA
registry. registry.
7. Acknowledgement 7. Acknowledgement
The authors thank Peter Koch, Rob Austein, Joe Abley, Mark Andrews, The authors thank Peter Koch, Rob Austein, Joe Abley, Mark Andrews,
Kenji Rikitake, Stephane Bortzmeyerand, Olafur Gudmundsson, and Kenji Rikitake, Stephane Bortzmeyer, Olafur Gudmundsson, and Alfred
Alfred Hines for their valuable comments and suggestions. Hoenes for their valuable comments and suggestions.
This work was supported by the US National Science Foundation This work was supported by the US National Science Foundation
(research grant SCI-0427144) and DNS-OARC. (research grant SCI-0427144) and DNS-OARC.
8. Normative References 8. Normative References
[PERL] Wall, L., Christiansen, T., and j. Orwant, "Programing [PERL] Wall, L., Christiansen, T., and J. Orwant, "Programming
Perl", July 2000. Perl, 3rd ed.", ISBN 0-596-00027-8, July 2000.
[RFC1034] Mockapetris, P., "Domain names - concepts and facilities", [RFC1034] Mockapetris, P., "Domain names - concepts and facilities",
STD 13, RFC 1034, November 1987. STD 13, RFC 1034, November 1987.
[RFC1035] Mockapetris, P., "Domain names - implementation and [RFC1035] Mockapetris, P., "Domain names - implementation and
specification", STD 13, RFC 1035, November 1987. specification", STD 13, RFC 1035, November 1987.
[RFC1123] Braden, R., "Requirements for Internet Hosts - Application [RFC1123] Braden, R., "Requirements for Internet Hosts - Application
and Support", STD 3, RFC 1123, October 1989. and Support", STD 3, RFC 1123, October 1989.
[RFC1996] Vixie, P., "A Mechanism for Prompt Notification of Zone [RFC1996] Vixie, P., "A Mechanism for Prompt Notification of Zone
Changes (DNS NOTIFY)", RFC 1996, August 1996. Changes (DNS NOTIFY)", RFC 1996, August 1996.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC2181] Elz, R. and R. Bush, "Clarifications to the DNS [RFC2181] Elz, R. and R. Bush, "Clarifications to the DNS
Specification", RFC 2181, July 1997. Specification", RFC 2181, July 1997.
[RFC2308] Andrews, M., "Negative Caching of DNS Queries (DNS [RFC2308] Andrews, M., "Negative Caching of DNS Queries (DNS
NCACHE)", RFC 2308, March 1998. NCACHE)", RFC 2308, March 1998.
[RFC2671] Vixie, P., "Extension Mechanisms for DNS (EDNS0)", [RFC2671] Vixie, P., "Extension Mechanisms for DNS (EDNS0)",
RFC 2671, August 1999. RFC 2671, August 1999.
[RFC3226] Gudmundsson, O., "DNSSEC and IPv6 A6 aware server/resolver [RFC3226] Gudmundsson, O., "DNSSEC and IPv6 A6 aware server/resolver
skipping to change at page 13, line 7 skipping to change at page 13, line 7
The University of Tokyo/WIDE Project The University of Tokyo/WIDE Project
Information Technology Center, 2-11-16 Yayoi Information Technology Center, 2-11-16 Yayoi
Bunkyo, Tokyo 113-8658 Bunkyo, Tokyo 113-8658
JP JP
Phone: +81 3 5841 2750 Phone: +81 3 5841 2750
Email: kato@wide.ad.jp Email: kato@wide.ad.jp
Full Copyright Statement Full Copyright Statement
Copyright (C) The IETF Trust (2007). Copyright (C) The IETF Trust (2008).
This document is subject to the rights, licenses and restrictions This document is subject to the rights, licenses and restrictions
contained in BCP 78, and except as set forth therein, the authors contained in BCP 78, and except as set forth therein, the authors
retain all their rights. retain all their rights.
This document and the information contained herein are provided on an This document and the information contained herein are provided on an
"AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST AND OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST AND
THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS
OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF
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