Some fun facts:

RAS (Remote Access Server) has both a Server end and a Client end. The Server side is called RAS, which runs as a service on the RAS Server so that clients can use telephone lines to connect to the server.

The client side of RAS is called "DUN" or Dial Up Networking. It is DUN that allows a client machine to connect to the RAS server.

In order to ensure secure communications, you can set the level of security required on both the client and the server side. By default, whenever a Microsoft client machine connects to an NT RAS Server, the passwords are transmitted via Microsoft Challenge/Handshake Protocol.

If you are calling into a RAS server from a machine that is NOT running a Microsoft operating system, you can still have the passwords encrypted by choosing “Accept any authentication including clear text” in the security tab.

If you are calling in from an operating system that is not a Microsoft system and are not able to connect via encrypted password authentication, then you should set encryption settings to allow any type of authentication, including "clear text". Clear text is just UUENCODE, which is not really encrypted and can be read by anybody with a network sniffer.

Now, just because our passwords are encrypted doesn't mean that the data is encrypted. You must choose to have data encryption if you want all data passing though the line to be encrypted. OK? You must choose it because it is NOT a default setting.

Keep in mind that when we are connecting as RAS clients, we are just another member of the network. Just as if we were in the office and connected to the network via a regular Ethernet connection.

Another type of security available with RAS is “callback” security. With callback security, the person calls into the server using DUN, and then the RAS server hangs up and calls them back. What types of callback are available?

Can We Buy Large Hard Drives?

How do client machines find IP addresses of computers they want to communicate with if there is not WINS server?

Protocol "overhead" involves things such as "error correction" and "data compression" and security settings. All this extra features increase the amount of information that must be transferred back and forth over the network, which can slow communications down a bit. One of the things about SLIP and TFTP is that although they aren't as "robust" as some of the other protocols, that are a bit faster on low bandwidth connections because of their lower "overhead".

Something interesting about network communications is how protocols determine the interaction between the computers talking to each other.

In the real world, the "protocol" is determined by the occasion. If we go to the White House, there is a protocol that must be followed. If we go to the doctor's office, there is a protocol that must be followed. It seems in the "real" world that its the "other" side that determines the protocol.

The computer network world is DIFFERENT. In the Network World, the CLIENT determines the protocol that is going to be used. When a network client connects to another computer, IT determines the protocol that will be used to communicate.

For example, let's say that our network uses both NetBEUI and TCP/IP. If our client has NetBEUI on top of its binding order and connects to a server that is also using both NetBEUI and TCP/IP, the protocol that will be used for communcation between these two computers is going to be NetBEUI. That is because the CLIENT determines which protocol is going to be used; and the NetBEUI protocol is on top of this client's binding order!