draft-ietf-ngtrans-ipv6-smtp-requirement-02.txt   draft-ietf-ngtrans-ipv6-smtp-requirement-03.txt 
Internet Engineering Task Force Motonori Nakamura Internet Engineering Task Force Motonori Nakamura
INTERNET-DRAFT Kyoto University INTERNET-DRAFT Kyoto University
Expires: January 13, 2002 Jun-ichiro itojun Hagino Expires: April 24, 2002 Jun-ichiro itojun Hagino
IIJ Research Laboratory IIJ Research Laboratory
July 13, 2001 October 24, 2001
IPv6 SMTP operational requirements IPv6 SMTP operational requirements
draft-ietf-ngtrans-ipv6-smtp-requirement-02.txt draft-ietf-ngtrans-ipv6-smtp-requirement-03.txt
Status of this Memo Status of this Memo
This document is an Internet-Draft and is in full conformance with all This document is an Internet-Draft and is in full conformance with all
provisions of Section 10 of RFC2026. provisions of Section 10 of RFC2026.
Internet-Drafts are working documents of the Internet Engineering Task Internet-Drafts are working documents of the Internet Engineering Task
Force (IETF), its areas, and its working groups. Note that other groups Force (IETF), its areas, and its working groups. Note that other groups
may also distribute working documents as Internet-Drafts. may also distribute working documents as Internet-Drafts.
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and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference material time. It is inappropriate to use Internet-Drafts as reference material
or to cite them other than as ``work in progress.'' or to cite them other than as ``work in progress.''
To view the list Internet-Draft Shadow Directories, see To view the list Internet-Draft Shadow Directories, see
http://www.ietf.org/shadow.html. http://www.ietf.org/shadow.html.
Distribution of this memo is unlimited. Distribution of this memo is unlimited.
The internet-draft will expire in 6 months. The date of expiration will The internet-draft will expire in 6 months. The date of expiration will
be January 13, 2002. be April 24, 2002.
Abstract Abstract
The memo lists operational requirements for IPv6 SMTP, and IPv6-capable The memo lists operational requirements for IPv6 SMTP, and IPv6-capable
MX DNS records. As we deploy IPv6 SMTP servers, it became apparent that MX DNS records. As we deploy IPv6 SMTP servers, it became apparent that
we need certain configuration in IPv6-capable MX DNS record, for stable we need certain configuration in IPv6-capable MX DNS record, for stable
dual-stack (IPv4 and IPv6) SMTP operations. The document tries to dual-stack (IPv4 and IPv6) SMTP operations. The document tries to
clarify the problems we have in transition period between IPv4 SMTP and clarify the problems we have in transition period between IPv4 SMTP and
IPv6 SMTP, and operational requirements for stable IPv4/v6 SMTP IPv6 SMTP, and operational requirements for stable IPv4/v6 SMTP
operation. operation.
The document does not try to define any new protocol. The document does not try to define any new protocol.
1. Summary of IPv4 MX operation 1. Summary of IPv4 MX operation
For reference purpose, the section outlines how mail message delivery is For reference purpose, the section outlines how mail message delivery is
performed in IPv4-only environment [Partridge, 1986] . performed in IPv4-only environment [Partridge, 1986] .
DRAFT IPv6 SMTP operational requirements July 2001 DRAFT IPv6 SMTP operational requirements October 2001
In IPv4 SMTP operation, we register MX records like below, for In IPv4 SMTP operation, we register MX records like below, for
"example.org." domain: "example.org." domain:
example.org. IN MX 1 mx1.example.org. example.org. IN MX 1 mx1.example.org.
IN MX 10 mx10.example.org. IN MX 10 mx10.example.org.
mx1.example.org. IN A 1.0.0.1 mx1.example.org. IN A 1.0.0.1
mx10.example.org. IN A 1.0.0.2 mx10.example.org. IN A 1.0.0.2
When an MTA delivers a message to a particular destination (say it is to When an MTA delivers a message to a particular destination (say it is to
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For simplicity, the document lists DNS records for IPv6 address as AAAA For simplicity, the document lists DNS records for IPv6 address as AAAA
records, not as A6 records [Crawford, 2000] . In reality, we can use a records, not as A6 records [Crawford, 2000] . In reality, we can use a
chain of A6 records, instead of AAAA records. chain of A6 records, instead of AAAA records.
There are couple of technologies defined for IPv4 and IPv6 transition. There are couple of technologies defined for IPv4 and IPv6 transition.
The document concentrates on issues with dual stack environment. The document concentrates on issues with dual stack environment.
Translators do not need special consideration from SMTP point of view; Translators do not need special consideration from SMTP point of view;
If we have SMTP traffic from IPv6 MTA to IPv4 MTA over an IPv6-to-IPv4 If we have SMTP traffic from IPv6 MTA to IPv4 MTA over an IPv6-to-IPv4
DRAFT IPv6 SMTP operational requirements July 2001 DRAFT IPv6 SMTP operational requirements October 2001
translator, the traffic will be considered as a normal IPv4 SMTP translator, the traffic will be considered as a normal IPv4 SMTP
traffic, from the IPv4 MTA point of view. We may, however, need some traffic, from the IPv4 MTA point of view. We may, however, need some
consideration on translators for protocols like IDENT [StJohns, 1993] . consideration on translators for protocols like IDENT [StJohns, 1993] .
3. SMTP sender algorithm in dual stack environment 3. SMTP sender algorithm in dual stack environment
When we lookup MX records for the domain in IPv4/v6 dual stack When we lookup MX records for the domain in IPv4/v6 dual stack
environment, we will see records like below: environment, we will see records like below:
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(5) Reorder queried result based on implementation-dependent preference (5) Reorder queried result based on implementation-dependent preference
between A and AAAA records. If you would like to encourage the between A and AAAA records. If you would like to encourage the
transition from IPv4 SMTP to IPv6 SMTP, AAAAs should take transition from IPv4 SMTP to IPv6 SMTP, AAAAs should take
precedence. precedence.
(6) Loop steps from (7) to (8), for all the addresses (or part of the (6) Loop steps from (7) to (8), for all the addresses (or part of the
list of addresses) we have. If no reachable destination is found, list of addresses) we have. If no reachable destination is found,
and if we are going through a list of MX records, go back to (3) and if we are going through a list of MX records, go back to (3)
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and try the next MX record. If we do not have a list of MX and try the next MX record. If we do not have a list of MX
records, or we have reached the end of the list of MX records, records, or we have reached the end of the list of MX records,
raise temporary delivery failure (finish). raise temporary delivery failure (finish).
(7) Try to make a TCP connection to the destination. If it fails, try (7) Try to make a TCP connection to the destination. If it fails, try
the next address we have. If it succeeds, go to step (8). the next address we have. If it succeeds, go to step (8).
(8) Try a SMTP protocol negotiation. If SMTP protocol negotiation (8) Try a SMTP protocol negotiation. If SMTP protocol negotiation
fails with TEMPFAIL (4xx), go back to (3) and try the next MX fails with TEMPFAIL (4xx), go back to (3) and try the next MX
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The easiest possible configuration is to configure the primary MX host The easiest possible configuration is to configure the primary MX host
as an IPv4/v6 dual stack node. By doing so, secondaries will have no as an IPv4/v6 dual stack node. By doing so, secondaries will have no
problem reaching the primary MX host. problem reaching the primary MX host.
; the configuration works just fine. ; the configuration works just fine.
; emails reaches from secondary MX to primary with no trouble. ; emails reaches from secondary MX to primary with no trouble.
example.org. IN MX 1 mx1.example.org. ; IPv4/v6 dual stack example.org. IN MX 1 mx1.example.org. ; IPv4/v6 dual stack
IN MX 10 mx10.example.org. ; IPv4 only IN MX 10 mx10.example.org. ; IPv4 only
IN MX 100 mx100.example.org. ; IPv6 only IN MX 100 mx100.example.org. ; IPv6 only
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There are many other ways to ensure the reachability between secondary There are many other ways to ensure the reachability between secondary
MX and primary MX. For example, we could configure secondary MX to MX and primary MX. For example, we could configure secondary MX to
route emails statically, without considering DNS MX configuration. Or route emails statically, without considering DNS MX configuration. Or
we could estalish alternative email routing path (i.e. UUCP, or via we could estalish alternative email routing path (i.e. UUCP, or via
IPv4/v6 translator) between secondary MX and the primary MX. IPv4/v6 translator) between secondary MX and the primary MX.
5. Operational experiences 5. Operational experiences
Many of the existing IPv6-ready MTAs seem to work in the way documented Many of the existing IPv6-ready MTAs seem to work in the way documented
in section 3. in section 3.
>From past experiments and operatinal experiences, it is known that none >From past experiments and operational experiences, it is known that most
of the existing IPv4-only MTAs will get confused by AAAA records, of the existing IPv4-only MTAs will not get confused by AAAA records,
registered for MX hostnames. No experiments were conducted with A6 registered for MX hostnames. No experiments were conducted with A6
records. records.
There were, however, cases where IPv6-ready MTAs get confused by broken
DNS servers. When attempting to canonify a hostname, some broken name
servers will return SERVFAIL (a temporary failure) on AAAA record
lookups. Upon this temporary failure, the mail is queued up for a later
attempt. These broken DNS servers should get fixed, for this issue as
well as for other IPv6 operations.
6. Open issues 6. Open issues
o How to interpret scoped address on MTAs. As we relay emails between o How to interpret scoped address in email addresses, on MTAs. As we
MTAs, interpretation of scoped address can be different between MTAs, relay emails between MTAs, interpretation of scoped address can be
as intermediate MTAs may be in different scope zone as the originator. different between MTAs, as intermediate MTAs may be in different scope
If we get scoped IPv6 address as a result of DNS lookups, how MTAs zone as the originator. If we get scoped IPv6 address as a result of
should behave? DNS lookups, how MTAs should behave?
If we consider scoped address in ``route-addr'' specification If we consider scoped address in ``route-addr'' specification
[Crocker, 1982] like [Crocker, 1982] like
<@kame.net,@[fec0::1]:itojun@itojun.org> <@kame.net,@[fec0::1]:itojun@itojun.org>
it gets more trickier. Luckily, route-addr form was obsoleted by it gets more trickier. Luckily, route-addr form was obsoleted by
RFC2822 [Resnick, 2001] . RFC2822 [Resnick, 2001] .
7. Security consideration 7. Security consideration
As presented in ``Open issues'' section, it could be problematical if As presented in ``Open issues'' section, it could be problematical if
route-addr email address format is used across multiple scope zones. route-addr email address format is used across multiple scope zones.
MTAs would need to reject emails with improper route-addr email address MTAs would need to reject emails with improper route-addr email address
formats. A possible example of improper route-addr format would be like formats. A possible example of improper route-addr format would be like
this: an email from outside of the site border, which carries numeric this: an email from outside of the site border, which carries numeric
site-local address in route-addr format. site-local address in route-addr format.
DRAFT IPv6 SMTP operational requirements October 2001
References References
Partridge, 1986. Partridge, 1986.
C. Partridge, "Mail routing and the domain system" in RFC974 (January C. Partridge, "Mail routing and the domain system" in RFC974 (January
1986). ftp://ftp.isi.edu/in-notes/rfc974.txt. 1986). ftp://ftp.isi.edu/in-notes/rfc974.txt.
DRAFT IPv6 SMTP operational requirements July 2001
Elz, 1997. Elz, 1997.
R. Elz and R. Bush, "Clarifications to the DNS Specification" in RFC2181 R. Elz and R. Bush, "Clarifications to the DNS Specification" in RFC2181
(July 1997). ftp://ftp.isi.edu/in-notes/rfc2181.txt. (July 1997). ftp://ftp.isi.edu/in-notes/rfc2181.txt.
Thomson, 1995. Thomson, 1995.
S. Thomson and C. Huitema, "DNS Extensions to support IP version 6" in S. Thomson and C. Huitema, "DNS Extensions to support IP version 6" in
RFC1886 (December 1995). ftp://ftp.isi.edu/in-notes/rfc1886.txt. RFC1886 (December 1995). ftp://ftp.isi.edu/in-notes/rfc1886.txt.
Crawford, 2000. Crawford, 2000.
M. Crawford, C. Huitema, and S. Thomson, "DNS Extensions to Support IPv6 M. Crawford, C. Huitema, and S. Thomson, "DNS Extensions to Support IPv6
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00 -> 01 00 -> 01
Correct email address notation for source-routed emails, based on a Correct email address notation for source-routed emails, based on a
comment from Gregory Neil Shapiro. comment from Gregory Neil Shapiro.
01 -> 02 01 -> 02
Refer RFC2822, not 822. Use example.org, not sample.org. Based on Refer RFC2822, not 822. Use example.org, not sample.org. Based on
comments from Arnt Gulbrandse. Add Operational experiences comments from Arnt Gulbrandse. Add Operational experiences
section. Clarify MX-points-to-CNAME, based on comments from Mohsen section. Clarify MX-points-to-CNAME, based on comments from Mohsen
Souissi. Souissi.
02 -> 03
Some cases, IPv6-ready MTAs gets troubled by wrong DNS server
responses for AAAA queries. From Gregory Neil Shapiro.
DRAFT IPv6 SMTP operational requirements October 2001
Acknowledgements Acknowledgements
The draft was written based on discussions with Japanese IPv6 users, and The draft was written based on discussions with Japanese IPv6 users, and
help from WIDE research group. help from WIDE research group. Here are a (probably incomplete) list of
people contributed to the draft: Gregory Neil Shapiro, Arnt Gulbrandse,
and Mohsen Souissi.
Author's address Author's address
DRAFT IPv6 SMTP operational requirements July 2001
Motonori NAKAMURA Motonori NAKAMURA
Center for Information and Multimedia Studies, Kyoto University Center for Information and Multimedia Studies, Kyoto University
Yoshida-nihonmatsu-cho, Sakyo, Kyoto 606-8501, JAPAN Yoshida-nihonmatsu-cho, Sakyo, Kyoto 606-8501, JAPAN
Tel: +81-75-753-9063 Tel: +81-75-753-9063
Fax: +81-75-753-9056 Fax: +81-75-753-9056
Email: motonori@media.kyoto-u.ac.jp Email: motonori@media.kyoto-u.ac.jp
Jun-ichiro itojun HAGINO Jun-ichiro itojun HAGINO
Research Laboratory, Internet Initiative Japan Inc. Research Laboratory, Internet Initiative Japan Inc.
Takebashi Yasuda Bldg., Takebashi Yasuda Bldg.,
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