WHY ISDN

WHY ISDN
INSTEAD
OF ANALOG

KINDS OF ISDN
EQUIPMENT

FEATURES

TO CONNECT
2 THE NET

BUFFER DELIVERS
THE MAIL

SETTING UP
YOUR OWN INTRANET

Buffer and I live in a very small community called Silver City. One day, Buffer decided to do our tiny community a favor by delivering the mail. Don't ask me how he got ahold of it, but within hours I had 70 or so assorted pieces of mail at our house. When I asked Buffer why he brought all the mail to me he said simply, "I didn't know where else to bring it". And that folks is how The Internet works.

On the Internet, everybody gets an address. everybody gets packages a.k.a packets, or improperly spelled, pkts. A package either belongs to you (your address) or it doesn't. When it belongs to you...

"I open it!" interrupted Buffer.

"That's right, but quit interrupting. If it doesn't belong to you Buffer then what do you do with it?"

Buffer shrugged dropping a package.

I picked it up. "This package belongs to someone in Cabin Cove! Boy, when you deliver the mail Buffer, you really take charge. Run this down to Cabin Cove. Here take this one too."

I began sorting mail. With Buffer gone I continued explaining. "You forward packages whose address you know, and send everything else whose address you don't know to a place called, interestingly enough, The Default Route. Buffer thinks our house is the default route. Our delivery system uses Buffer. The Internet uses IP. Whenever IP goes over a Wide Area Network (WAN) connection like, a modem or an ISDN adapter, a second carrier, or protocol, is used called PPP. It's the same as putting one package *inside* another.

Just then there was a knock at the door. "Who is it?" I called.

"It's me, Buffer. I locked myself out."

"You're back already?"

"I forgot some of the packages."

Buffer began picking up packages and dropping others.

"Buffer, that's too many packages for you to take at once, just take five."

"No," Buffer said, "I can carry more."

"No, you can't. Let's compress some of these into one package."

Buffer agreed and soon I had him on his way. Now where were we? Oh, connecting through an ISDN (WAN) to The Internet. When a remote Host wishes to establish a connection, an agreed protocol has to be used for our carrier Buffer, I mean IP. When Buffer knocks on the door and asks to come in, he is using a "knock to come in protocol". IP uses the PPP protocol. I let Buffer in, but first I made him identify himself. So does PPP. That's called Authentication. Buffer, our carrier, wants to know how much he can carry as does PPP. I suggested to Buffer that he might carry more if he compressed packages together, so does PPP. Get it?

There are some differences between Buffer and PPP: First, Buffer asks to come in (authenticates) before I decide how much he can carry. PPP, on the other hand, first agrees about its compression and how much it can carry in its packets,then authenticates.

The important things to remember are:

1. Remote (WAN) connections to The Internet use PPP (Stands for Point to Point Protocol). You and I need a PPP "stack" if we want to connect to The Internet.
2. PPP has different phases we need to know just a little about. They are:
   1. LCP, (How much we carry, how we carry it, etc.) (Stands for Link Control Protocol)

   2. Authentication, (We tell the RAS Remote Access Server who we are)

   3. NCP, (IP has to do what PPP did. Don't worry about this for now.)

The only phase we plain folk need care about is authentication and only then if configuring an ISDN bridge or router. It's important because if the name, password or type of authentication used don't match on both bridges/routers, the bridges and routers won't talk to one another at all.

You must have the following on any Host or Router connected to The Internet.

1. An IP address. It's an address your Host gets assigned.

2. A Net Mask. A mask your host can look through to see if it needs to pay any attention at all to a particular address.
   
3. A default route. The address your Host can send packets to when its clue less as to where they really belong.
   

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