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Q: What will happen to ISDN devices, which are
expensive and can be hard to configure, now that 56Kbps modems are available?
Compared with other connection methods, ISDN has several important
advantages that will ensure its place in the industry for a while. ISDN provides
rapid (several seconds) logon times and guaranteed bandwidth (you get either
64Kbps or 128Kbps connections). You can purchase an ISDN router that lets you
easily provide a network-wide connection and conceal your company's internal IP
systems. ISDN devices will continue to compete with modems because you can now
turn most ISDN devices on and off and use them on demand (i.e., in a dial-up
mode, like you can with a conventional modem).
Q: I plan to purchase a router, but
I have some concerns about Network Address Translation (NAT). Can you explain NAT?
NAT helps you simplify and conserve IP addresses because it minimizes the
number of leased IP addresses you need. NAT enables private internal networks
that use unregistered IP addresses to connect to the Internet. Specifically, NAT
operates on a router, usually connecting two networks, and translates private
(unregistered) IP addresses in the internal network into legal (registered) IP
addresses before sending packets to another network (such as the Web). As part
of this functionality, you can configure NAT to advertise only one IP address
for the entire network to the outside world. This approach increases security
because that one IP address effectively hides your entire internal network from
other networks.
Companies typically implement NAT in remote access environments because you
can easily control which IP addresses are used. A NAT router answers Address
Resolution Protocol (ARP) requests for IP addresses inside a company's dynamic
pool and even functions with Domain Name System (DNS) servers on the Internet.
NAT can save you considerable hassle in assigning and maintaining IP addresses.
Q: I recently read that sales of asynchronous
transfer mode (ATM) networks are down, in part because of the perception that ATM is difficult
to set up. How hard is ATM to configure?
ATM is more difficult to configure than other networks because you must set
the switches and NICs to the same protocol. To establish protocols and basic
port configurations, you connect the NICs to the switches. For example, on most
switches, you can dictate control port by port (e.g., you can set up a port as
full duplex or half duplex). You also have to establish user and password
information on the switches to configure them.
Configuring the Switch
You usually make the initial connection to the switch via a com port. Start
by attaching a reversed cable to the machine com port and then connecting the
cable to the switch com port. Open Hyperterminal in Windows NT, and select any
of the available accounts, such as the HyperTerminal account. In the Connect To
dialog box, change the connection to the appropriate com port (e.g., COM1). The
system will use the built-in accounts (see the switch manuals for the
default value) to log you on to the switch.
The major component you have to set up is the User Network Interface (UNI).
You can use version 3.0 or version 3.1 of this protocol (I suggest you use the
latest version, 3.1). The rest of the setup is a matter of choice. If you stack
switches, you must properly configure the stack modules. For example, Screen 1
shows a partial display of the parameters of one of my switches. Notice the
amount of detail, including the IP address and the temperature inside the
switch. Screen 2 shows the setup for the
ATM switching. Notice the use of UNI 3.1, stacking (Whitetree 2500 and 3000), and the use of ATM 155 backbones. After
you assign all necessary parameters, you simply restart or reboot your switches.