Mark Wilkinson writes:
> We have a parallel email system using Lotus cc:Mail and I'm pre-empting our
> requirements
> and saying we may need to bridge the two. Since we have no DNS on the IP
> Network, how will
> the mail routing be performed. I presume you need DNS to get the recipient
> machine's IP address
> so you know which node to forward undelivered mail onto - or am
> misunderstanding the way
> Internet email works here...I'm relatively new to all this Networking
> stuff...<g>
Well, Internet e-mail addressing syntax does allow you to specify numeric
machine IP addresses, but it's darn ugly and hard to remember. I've only
needed to do that when the target machine's DNS server is acting bizarrely.
> DNS has always puzzled me I'm afraid. AFAIK, it's just a way to translate a
> name to an IP
> address, but how does the machine requesting the conversion know where the
> machine
> with the "database" is? How does this work on the Internet? Is there a
> giant server some-
> where with all the domain names and IP addresses on it? <g>
DNS is a distributed hierarchical database.
At the "root" of DNS are pointers to the DNS servers that handle each of the
major top-level domains such as .edu, .com, .net, etc, plus the international
country codes such as .au, .uk, .us etc.
Anybody running a DNS server needs a config file with the IP addresses of the
root DNS servers. This file is available from rs.internic.net (and probably
other places), and looks like this:
; This file holds the information on root name servers needed to
; initialize cache of Internet domain name servers
; (e.g. reference this file in the "cache . <file>"
; configuration file of BIND domain name servers).
;
; This file is made available by InterNIC registration services
; under anonymous FTP as
; file /domain/named.root
; on server FTP.RS.INTERNIC.NET
; -OR- under Gopher at RS.INTERNIC.NET
; under menu InterNIC Registration Services (NSI)
; submenu InterNIC Registration Archives
; file named.root
;
; last update: Aug 22, 1997
; related version of root zone: 1997082200
;
;
; formerly NS.INTERNIC.NET
;
. 3600000 IN NS A.ROOT-SERVERS.NET.
A.ROOT-SERVERS.NET. 3600000 A 198.41.0.4
;
; formerly NS1.ISI.EDU
;
. 3600000 NS B.ROOT-SERVERS.NET.
B.ROOT-SERVERS.NET. 3600000 A 128.9.0.107
;
; formerly C.PSI.NET
;
. 3600000 NS C.ROOT-SERVERS.NET.
C.ROOT-SERVERS.NET. 3600000 A 192.33.4.12
;
; formerly TERP.UMD.EDU
;
. 3600000 NS D.ROOT-SERVERS.NET.
D.ROOT-SERVERS.NET. 3600000 A 128.8.10.90
;
; formerly NS.NASA.GOV
;
. 3600000 NS E.ROOT-SERVERS.NET.
E.ROOT-SERVERS.NET. 3600000 A 192.203.230.10
;
; formerly NS.ISC.ORG
;
. 3600000 NS F.ROOT-SERVERS.NET.
F.ROOT-SERVERS.NET. 3600000 A 192.5.5.241
;
; formerly NS.NIC.DDN.MIL
;
. 3600000 NS G.ROOT-SERVERS.NET.
G.ROOT-SERVERS.NET. 3600000 A 192.112.36.4
;
; formerly AOS.ARL.ARMY.MIL
;
. 3600000 NS H.ROOT-SERVERS.NET.
H.ROOT-SERVERS.NET. 3600000 A 128.63.2.53
;
; formerly NIC.NORDU.NET
;
. 3600000 NS I.ROOT-SERVERS.NET.
I.ROOT-SERVERS.NET. 3600000 A 192.36.148.17
;
; temporarily housed at NSI (InterNIC)
;
. 3600000 NS J.ROOT-SERVERS.NET.
J.ROOT-SERVERS.NET. 3600000 A 198.41.0.10
;
; housed in LINX, operated by RIPE NCC
;
. 3600000 NS K.ROOT-SERVERS.NET.
K.ROOT-SERVERS.NET. 3600000 A 193.0.14.129
;
; temporarily housed at ISI (IANA)
;
. 3600000 NS L.ROOT-SERVERS.NET.
L.ROOT-SERVERS.NET. 3600000 A 198.32.64.12
;
; housed in Japan, operated by WIDE
;
. 3600000 NS M.ROOT-SERVERS.NET.
M.ROOT-SERVERS.NET. 3600000 A 202.12.27.33
; End of File
Say you need to resolve the hostname of one of the mail servers here,
ponyexpress.gwc.cccd.edu. Your DNS client code first asks the above root
servers about ".edu". You then ask the .edu server about .cccd.edu, and it
tells you that I run several DNS servers here at various IP addresses. You
then ask one of my servers about .gwc.cccd.edu, and it turns out that is
handled by a different campus DNS server. So finally you ask the campus DNS
server about ponyexpress.gwc.cccd.edu and the IP address is obtained.
Because this can take a fair amount of time to traverse multiple levels of
servers like this, DNS servers cache the information that is retrieved, making
subsequent lookups much faster.
On an MPE machine, you can modify RESLVCNF.NET.SYS to tell your 3000 to use
another machine's DNS server to do your lookups, or you can run my port of the
BIND DNS server, in which case you get your own local cache, plus the ability
to provide DNS information about your own domains.
For more info about BIND/iX, see:
http://www.cccd.edu/~markb/bindix.html
--
Mark Bixby E-mail: [log in to unmask]
Coast Community College Dist. Web: http://www.cccd.edu/~markb/
District Information Services 1370 Adams Ave, Costa Mesa, CA, USA 92626-5429
Technical Support +1 714 438-4647
"You can tune a file system, but you can't tune a fish." - tunefs(1M)
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