aghhhh!

Electronic mail-- email for short-- allows you to exchange messages with users on remote hosts without actually having to know how to access these hosts. 

"TCP/IP traces its origins to a research project funded by the United States DARPA (Defense Advanced Research Projects Agency) in 1969. This was an experimental network, the ARPANET, which was converted into an operational one in 1975, after it had proven to be a success."

"Of course, IP also requires a hardware-independent addressing scheme. This is achieved by assigning each host a unique 32-bit number, called the IP-address. An IP-address is usually written as four decimal numbers, one for each 8-bit portion, separated by dots. For example, quark might have an IP-address of 0x954C0C04, which would be written as 149.76.12.4. This format is also called dotted quad notation."

cache  =TTL

lo
The local loopback interface. It is used for testing pur- poses, as well as a couple of network applications. It works like a closed circuit in that any datagram written to it will be immediately returned to the host's networking layer. There's always one loopback device present in the kernel, and there's little sense in having fewer or more.

  ------------------------------------------------------
      +--------------+-------------------------------------+
      |Board         | Addresses probed for                |
      +--------------+-------------------------------------+
      |WD/SMC        | 0x300, 0x280, 0x380, 0x240          |
      |SMC 16 Ultra  | 0x300, 0x280                        |
      |3c501         | 0x280                               |
      |3c503         | 0x300, 0x310, 0x330, 0x350, 0x250,  |
      |              | 0x280, 0x2a0, 0x2e0                 |
      |NEx000        | 0x300, 0x280, 0x320, 0x340, 0x360   |
      |HP            | 0x300, 0x320, 0x340, 0x280, 0x2C0,  |
      |              | 0x200, 0x240                        |
      |DEPCA         | 0x300, 0x320, 0x340, 0x360          |
      +--------------+-------------------------------------+
      +--------------+-------------------------------------+
 
   --------------------------------
      +-----------+-----------+------+
      |Interface  | I/O Port  | IRQ  |
      +-----------+-----------+------+
      |plip0      | 0x3BC     | 7    |
      |plip1      | 0x378     | 7    |
      |plip2      | 0x278     | 5    |
      +-----------+-----------+------+
      +-----------+-----------+------+
      
 SLIP (Serial Line IP), and PPP (Point-to-Point Protocol) are a widely used protocol for sending IP-packets over a serial link. A number of institutions offer dial-up SLIP and PPP access to machines that are on the Internet, thus providing IP-connectivity to private persons (something that's otherwise hardly affordable).
 
 # mknod -m 666 /dev/cua1 c 5 65
           # chown root.root /dev/cua1
< /pre>
Some people suggest making /dev/modem a symbolic link to your
modem device, so that casual users don't have to remember the somewhat
un-intuitive cua1. However, you cannot use modem in one
program, and the real device file name in another. This is because
these programs use so-called lock files to signal that the
device is used. By convention, the lock file name for cua1, for
instance, is LCK..cua1.  Using different device files for the
same port means that programs will fail to recognize each other's lock
files, and will both use the device at the same time. As a result, both
applications will not work at all.

ifconfig interface [[-net|-host] address [parameters]]

What is a Mail Message?

A Mail message generally consists of a message body, which is the text the sender wrote, and special data specifying recipients, transport medium, etc., very much like what you see when you look at a letter's envelope.

INTERESTINGGGGG: "It's been said that you aren't a real Unix system administrator until you've edited a sendmail.cf file. It's also been said that you're crazy if you've attempted to do so twice:-)"