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Subject:Re: Bitnet vs. Internet From:Lynn Ward <ward -at- UX1 -dot- CSO -dot- UIUC -dot- EDU> Date:Tue, 23 Mar 1993 10:18:11 -0600
>According to my misunderstanding, they are two separate networks
>interconnected by gateways at a lot of institutions. A person
>on one net can send mail to the other by specifying a "bang path"
>(a lot of wizardly mumblings interspersed with exclamation points)
>to one of these gateways. Unfortunately, the folks downstairs met
>their transparency goal too well, so I've never found out exactly
>how you do this! But there are a lot of gateways, and surely
>someone on this list (or one of the books mentioned earlier) will
>cite one.
The difference between Internet and BITNET addressing is that each BITNET
node has a unique node name of eight characters or less. BITNET uses
"store and forward" messaging meaning that messages are forwarded from one
node to another until they reach their destination. And of course, the two
networks use entirely different transport protocols.
Internet mail is sent directly from the source to the destination. It is
not stored at intermediary nodes. Internet addresses are based on the
domain name system, which is a hierarchical method of naming a host. The
domain at the far right, usually "edu" for educational instututions, is
called the top level domain. As one moves one step further to the left,
the domain is further qualified. The name just to the right of the "@"
sign is the name of the host itself. TCP/IP packets, however, do not uses
domain name to find their way from source to destination. They use IP
numbers. Every fully-qualified domain name has an associated IP number (4
binary octets that are usually expressed in decimal form, separated by
periods, e.g. 128.174.18.13). When a domain name is used instead of an IP
address (to send mail or open a telnet session), a query is sent to a local
domain name resolver to identify the IP number associated with the name.
The local resolver looks at its own table of IP numbers and associated IP
addresses to see if it can resolve the name. If not, it sends the query on
to a top level dns resolver such as the one for the "edu" domain, which in
turn sends a query to the domain server for the next lower level of the
domain and so on, until finally the IP address of the destination node can
be identified and used in the packet headers.
Bang paths are used with UUCP (Unix to Unix Copy Program) mail, not
Internet or BITNET mail. A UUCP mail address might look something like
this: uunet!tomatoe!quayle (quayle is the name of the recipient, "tomatoe"
is the UUCP node name of the machine on which he receives mail, and "uunet"
is a well-known UUCP gateway that knows about alot of UUCP nodes). Note
that the address proceeds from the general to the specifical, unlike
Internet address which proceed from the general to the specific.
My predecessor here at UIUC wrote a very nice piece called "Understanding
e-mail Addresses." I'll see if I can dredge up the original file and
convert it to ASCII for this group.
Lynn
________________
Lynn Ward, Network Design Office
University of Illinois at Urbana-Champaign
1541 DCL, 1304 West Springfield Ave., Urbana, IL 61801
(217)244-0681, ward -at- ux1 -dot- cso -dot- uiuc -dot- edu
