Subtitles of the Movie

There are many different roles the network Server can perform, and the same Server box can perform more than one role. But many times especially in larger networks each Server is dedicated to a single purpose. Some of the roles that a network Server can perform include a Gateway. A Gateway is a translator that translates one protocol to another. An example of a Gateway Server would be an SNA Gateway that fits in-between an IBM mainframe or an NT or Windows 2000 network. It allows the mainframe and the network to communicate with each other by translating. A router transfers packets from one network to another. routers communicate with each other, and routers can be dedicated boxes. Routers themselves are computers, but we can also make a computer into a router. In other words if we install software such as Windows 2000, we can then make a computer into a router and even put the security features into the router and do this with a computer that we already have - thus saving the company a tremendous amount of money. A Bridge allows us to segment network traffic. And a Bridge works by recording the MAC addresses and the section of the network, or the subnet of the network where that address or that MAC address came from. So Bridges allow us to segment network traffic, but they do it in a different way than a Router does. And computers as servers can be made to act like a Bridge, since a Bridge just forms a table of MAC addresses, and uses that to segment network traffic. A firewall protects things from coming into the network as well as things getting out of the network. We can configure a firewall so that people can't get access to certain resources through the network, or can't send large files out of our organization. This can be as much of a security threat as the security threat of the Internet coming into our organization; we can configure a firewall to do both of these things. A network address translator (NAT) protects a company by hiding the real addresses that we use inside of our network. When a person uses Internet resources, they are using the address of the Router. And that's the address that will be issued on the network, or that's the address that will be seen on the Internet. So a Network Address Translator allows us to hide our real private network addresses, and therefore be able to maintain security. A Network Address Translator allows us also to only have one real public network address, and to have many different computers with different private network addresses be able to use that same public network address to contact the Internet. A proxy takes it one step further. A proxy provides a Network Address Translation service, but a proxy can also provide additional information for clients. A proxy can provide for the administrator a list of all of the people who access certain resources through the network and exactly when they did it, and for clients a proxy can provide a cache of information. So that if a person in the same subnet has gone out to a site that normally they would not have gone to or that is not one that they go to everyday, and that has to be resolved through the DNS servers, through the Internet. Now that IP address will be stored in the proxy. So when the next person wants to go out to that site, they will immediately get a connection to that site and will not have to have that resolution through the Internet using the DNS servers. So a proxy provides Network Address Translation as well as caching and information and reports. And a proxy can also provide a firewall. A Microsoft proxy, the Microsoft proxy products also provides a firewall in addition to all of the other services. We will continue taking a look at network Server roles in our next lesson.