All Categories :
Intranets
Chapter 11
How Converting IPX Networks to
an Intranet Works
CONTENTS
It's rare that an entire intranet will be built completely from
scratch. It is more likely that an existing network, such as a
Novell NetWare network, will be converted to an intranet. At a
corporation there can be many networks already in existence before
an intranet comes in, often connected in a company-wide Wide Area
Network (WAN). There may be a variety of different network technologies
connected to the WAN. One way of converting a network to an intranet
is to take it piece by piece and convert individual department
LANs to an intranet, and then build from there.
Often, the single most important factor in convincing a corporation
to start an intranet is that people within the company will gain
access to the Internet and its resources. So the first step in
creating the intranet will often be giving easy access to the
Internet from an existing corporate network. It's much faster
for people to get at the Internet over a network instead of having
to dial in via modem-and it also saves money in the long run.
But when that Internet access is provided, it's also important
that all the existing network services be maintained as well.
A simple solution is to have people run software needed both for
the existing network as well as for the Internet. Let's take a
NetWare network as an example. In order to use NetWare and get
access to its services such as electronic mail and others, computers
on the network need to run the IPX (Internet Packet Exchange)
protocol. Don't be confused about the name-IPX doesn't allow access
to the Internet, but instead to a NetWare network's resources.
When people want access to the Internet as well, they can run
a TCP/IP stack-software that will allow them to access
the Internet. The TCP/IP stack and IPX will both be running simultaneously
on their computers. When they need to access a NetWare resource,
IPX allows them to do it. When they want to access the Internet,
TCP/IP does the job. The problem with this is that it is not as
simple as it sounds because the protocol stacks take up considerable
memory and sometimes there is not enough memory left to start
applications without unloading one of the protocols.
Internet requests go via TCP/IP to an intranet router, which is
connected to an Internet Service Provider via a Channel Service
Unit/Data Service Unit (CSU/DSU). Especially in large companies
with many people on a network, this connection will be made via
a leased high-speed digital line, such as a T1 line. There needs
to be a CSU/DSU and a router on the other end, and the requests
travel through them in reverse order, that is into the CSU/DSU
and then to the router. The CSU/DSU units are used to assure quality
digital signals over digital phone lines.
In this kind of setup, people can access an intranet as well as
the Internet. In this way, a company can slowly build up an intranet
while keeping an existing Novell network. People on the network
will be able to access intranet resources since they're running
TCP/IP stacks, and NetWare resources, since they're running IPX.
Most intranets aren't built from scratch-many are existing networks,
such as Novell NetWare, that have to be converted into an intranet.
Often, the first step in moving toward an intranet is to give
Internet access to users on an existing network. At some later
point, intranet technology can then be brought inside the network
itself and it can be turned into an intranet. This illustration
shows that first step: how an existing network, such as a NetWare-based
one, can be given access to the Internet, yet still keep access
to the NetWare architecture.
- When a computer on the network wants to connect to the Internet
and request information from it, a request is sent to a router
on the intranet. This router will send the request to the proper
Internet destination.
- On a NetWare network, the NetWare operating system is used
to handle network traffic and administration. As a way to route
packets across the network, NetWare uses the IPX (Internet Packet
Exchange) protocol. Note that although IPX is called Internet
Packet Exchange, it doesn't actually provide Internet access or
transport Internet information. Workstations attached to the NetWare
network-and servers on the network-need to have IPX loaded in
memory in order to use the network.
- In order for workstations on the Novell network to gain access
to the Internet or intranet, they need to run the TCP/IP protocols
that form the basis of the Internet. To do that, a TCP/IP stack
must be installed on each computer that will allow it to access
the Internet. That means that each computer will have both IPX
and a TCP/IP stack installed on it, to allow it to access the
Internet as well as the Ethernet network. Basically, this results
in "RAM cram" and is one of the biggest headaches for
anyone trying to run both protocol stacks.
- A Channel Service Unit/Data Service Unit (CSU/DSU) makes the
physical connection between the intranet router and an Internet
Service Provider (ISP). The ISP provides the actual Internet connection
and services. A variety of digital lines can connect the CSU/DSU
to the ISP, including a 56 Kbps leased line, a high-speed T1 line,
or an even higher-speed T3 line.
- The requested information is sent back through the CDU/DSU
and router, and is then routed to the computer that requested
the information.
- If the information is instead located on an intranet inside
the company, the router will send the request to the proper host,
which will then send the information back to the requester.
- Some products such as NetWare/IP will allow computers on a
NetWare network to access both NetWare services and servers and
the Internet. That means they don't have to run both the IPX and
TCP/IP protocols, eliminating the memory problems resulting from
the multiple stacks.
Contact
reference@developer.com with questions or comments.
Copyright 1998
EarthWeb Inc., All rights reserved.
PLEASE READ THE ACCEPTABLE USAGE STATEMENT.
Copyright 1998 Macmillan Computer Publishing. All rights reserved.
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