RE: address with brackets
- From: "Mulnick, Al" <Al.Mulnick@xxxxxxxxxx>
- To: "'[ExchangeList]'" <exchangelist@xxxxxxxxxxxxx>
- Date: Mon, 15 Sep 2003 16:15:00 -0400
I've read that as well, but I still don't see the value of the
domain-literal addressing sequence and this doesn't help to explain it.
From that RFC (which, as far as I'm concerned is really ineffectual since
many hosts are still only RFC 821/822 compliant and don't know of 2821/2822
comments yet):
4.1.3 Address Literals
Sometimes a host is not known to the domain name system and
communication (and, in particular, communication to report and repair
the error) is blocked. To bypass this barrier a special literal form
of the address is allowed as an alternative to a domain name. For
IPv4 addresses, this form uses four small decimal integers separated
by dots and enclosed by brackets such as [123.255.37.2], which
indicates an (IPv4) Internet Address in sequence-of-octets form. For
IPv6 and other forms of addressing that might eventually be
standardized, the form consists of a standardized "tag" that
identifies the address syntax, a colon, and the address itself, in a
format specified as part of the IPv6 standards [17].
Specifically:
IPv4-address-literal = Snum 3("." Snum)
IPv6-address-literal = "IPv6:" IPv6-addr
General-address-literal = Standardized-tag ":" 1*dcontent
Standardized-tag = Ldh-str
; MUST be specified in a standards-track RFC
; and registered with IANA
Snum = 1*3DIGIT ; representing a decimal integer
; value in the range 0 through 255
Let-dig = ALPHA / DIGIT
Ldh-str = *( ALPHA / DIGIT / "-" ) Let-dig
IPv6-addr = IPv6-full / IPv6-comp / IPv6v4-full / IPv6v4-comp
IPv6-hex = 1*4HEXDIG
IPv6-full = IPv6-hex 7(":" IPv6-hex)
IPv6-comp = [IPv6-hex *5(":" IPv6-hex)] "::" [IPv6-hex *5(":"
IPv6-hex)]
; The "::" represents at least 2 16-bit groups of zeros
; No more than 6 groups in addition to the "::" may be
; present
IPv6v4-full = IPv6-hex 5(":" IPv6-hex) ":" IPv4-address-literal
IPv6v4-comp = [IPv6-hex *3(":" IPv6-hex)] "::"
[IPv6-hex *3(":" IPv6-hex) ":"] IPv4-address-literal
; The "::" represents at least 2 16-bit groups of zeros
; No more than 4 groups in addition to the "::" and
; IPv4-address-literal may be present
In theory, this sounds great and everybody should go away happy. In
practice, if I have the IP address, where'd it come from? If I have an A RR
why can't I route to the domain that way? How do I scale that with mulitple
mail hosts?
I suppose I can answer my question by putting a link on my web page for
abuse such as abuse@[....] but that begs the question of how people get to
my web page without my DNS? It starts to become circular logic after a
brief amount of thought. About the only place I could put this address
would be on my WHOIS records, and that can be hacked (and has) and often
isn't up to date anyway. Why bother? I don't see the value.
I'd love it if somebody can point out the value and useful implementations
of such an address. 'Till then I'll continue to believe this is wrong and
the world is flat ;)
Al
-----Original Message-----
From: Mark Fugatt [mailto:mark@xxxxxxxxx]
Sent: Monday, September 15, 2003 2:57 PM
To: [ExchangeList]
Subject: [exchangelist] RE: address with brackets
http://www.MSExchange.org/
I would recommend taking a look at this RFC:
http://www.faqs.org/rfcs/rfc2821.html
Mark Fugatt
MCT, MCSE, Microsoft Exchange MVP
Pentech Office Solutions Inc
Tel: 585 586 3890
Cell: 585 576 4750
Fax: 585 249 0316
www.4mcts.com
www.exchangetrainer.com
-----Original Message-----
From: Mulnick, Al [mailto:Al.Mulnick@xxxxxxxxxx]
Sent: Monday, September 15, 2003 12:06 PM
To: [ExchangeList]
http://www.MSExchange.org/
I'm starting to wonder if I'm reading the same RFC :)
I see this part of the RFC :
6.2.3. DOMAIN TERMS
A domain-ref must be THE official name of a registry, network,
or host. It is a symbolic reference, within a name sub-
domain. At times, it is necessary to bypass standard mechan-
isms for resolving such references, using more primitive
information, such as a network host address rather than its
associated host name.
To permit such references, this standard provides the domain-
literal construct. Its contents must conform with the needs
of the sub-domain in which it is interpreted.
Domain-literals which refer to domains within the ARPA Inter-
net specify 32-bit Internet addresses, in four 8-bit fields
noted in decimal, as described in Request for Comments #820,
"Assigned Numbers." For example:
[10.0.3.19]
Note: THE USE OF DOMAIN-LITERALS IS STRONGLY DISCOURAGED. It
is permitted only as a means of bypassing temporary
system limitations, such as name tables which are not
complete.
The names of "top-level" domains, and the names of domains
under in the ARPA Internet, are registered with the Network
Information Center, SRI International, Menlo Park, California.
And especially notice the NOTE section which strongly discourages the use of
domain literals. I have to question the use of that by any
blacklist/blocklist/blockhead that says you have to have one of those,
especially since that concept doesn't really scale well, does it? Multiple
MX records are needed and if DNS is inoperable, then I suppose that reverse
DNS checks would also be broken, right?
I'm not trying to rant about this, but it makes no sense!! What is the
value of a domain-literal/implicitly defined FQDN for host delivery? Better
yet, is that not a bigger problem to specify such a thing with little
return? I'd have to give away half the addresses (which arguably should be
public, but the situation is if DNS is down). I think that the further use
of the RFC which says that you should be able to fall back to trying an A RR
for a domain is a far better use of the system than is domain-literal
acceptance.
Al
-----Original Message-----
From: Mark Fugatt [mailto:mark@xxxxxxxxx]
Sent: Monday, September 15, 2003 10:27 AM
To: [ExchangeList]
Subject: [exchangelist] RE: address with brackets
http://www.MSExchange.org/
Here is a link that should help you out: http://tinyurl.com/g8vq
Mark Fugatt
MCT, MCSE, Microsoft Exchange MVP
Pentech Office Solutions Inc
Tel: 585 586 3890
Cell: 585 576 4750
Fax: 585 249 0316
www.4mcts.com
www.exchangetrainer.com
-----Original Message-----
From: giordanocontigiani@xxxxxxxxxxxxxxxxx
[mailto:giordanocontigiani@xxxxxxxxxxxxxxxxx]
Sent: Saturday, September 13, 2003 3:48 AM
To: [ExchangeList]
http://www.MSExchange.org/
RFC 822 require that SMTP server accept addres like "name@[1.2.3.4]", where
mail domain is a dtext within brackets. My exchange 2000 server dont accept
this type of address (there is a manner to configure this?), second question
outlook client dont permit to send to this address (outlook express permit
it) thanks for any info regards giordano contigiani sys admin
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