Network Support Encyclopedia 15/novell-nsepro-1992-vol15.iso/download/wan.txt

Text File | 1991-06-24 | 18KB | 269 lines

                   INTERNETWORKING YOUR NETWARE LANS
                       Connecting the PC Workgroup to the World

The ability to connect independent networks is of key importance to any organization.  This document looks
at how organizations can evaluate their internetworking needs and how Novell products provide LAN-to-LAN
solutions.

As LAN technology has continued to evolve so have users expectations.   Users realize that if sending an
electronic file to a colleague down the hall is convenient, sending a file across the country will help
productivity even more: if sharing a database among the staff in the corporate office simplifies and speeds
order processing, sharing that same database with branch offices could streamline the entire order processing
system.

Novell recognized these needs early on, so over the past several years each new Novell product introduction
has offered NetWare users increased levels of connectivity.  NetWare products connect more than workgroups
they also incorporate many workgroup networks into large Wide Area Networks (WANs).  A Wide Area
Network allows workstations on different LANs to transfer files, send electronic mail, access data files, and
access applications on PCs, Macintoshes and host mainframes across the office, across the country and across
the world.

LAN-to-LAN Basics
Novell defines WANs in its broadest sense: a network connection or a series of connections that lets workstation
users access remote resources including other LANs and mainframe hosts.

LAN-to-LAN connections can be classified according to the type of transmission medium used to send the data.
Services offered by telecommunications companies include point-to-point voice grade lines, packet switched
services using X.25, and high speed synchronous lines including Digital Data Service (DDS) and T1 lines.  Speed
and cost are the primary factors that differentiate the transmission types.

LAN-to-LAN connections are also classified according to the different data-link protocols that the network can
accommodate.  Some connections link LANs that share the same physical topology, data packet protocols and
network operating system.  Other connections incorporate LANs that differ in one or more of these aspects.

LAN-to-LAN connection products provide hardware for connecting the LAN to the WAN and software to
supervise the data transfer process.  These products can be a special standalone box, or they can be an interface
board that fits into a PC or file server and the associated software.

Novell offers a family of NetWare LAN-to-LAN products to link workgroups via WANs:
     -NetWare Async Router
     -NetWare Link/X.25
     -NetWare Link/64
     -NetWare Link/T1




Defining the Level of LAN-to-LAN Connectivity
Since no two users are exactly alike in the way they use their PCs and other workstations, no two
PC/workstation workgroups are exactly alike in their need for WAN connectivity.  Each has its own needs
expectations and resources.  NetWare communication products accommodate the full range of WAN connectivity
needs.  The following seven questions will help you evaluate the type of WAN connectivity a workgroup will
need so you can choose the right level of connectivity.

1. What kind of work will be done across the WAN Link?
2. How much data will be transferred and how often?
3. How many sites must be connected and where are the located
4. What are the cost constraints?
5. What kind of technical expertise is available at the different sites?
6. How much growth will the system need to accommodate?
7. Overall, what services will the WAN Offer users?

There are four kinds of WAN use.  Each makes different demands on the WAN.  Reviewing the needs of your
workgroup in each of the four areas will help you estimate the volume of data that the WAN must support.

What Kind of Work Will be Crossing the Link?
> FILE TRANSFER: File transfers usually place relatively little strain on the network.  Sending a file between
workstations or between the workstation and the file server involves only one way communication.  The
sending workstation can complete the transaction without waiting for a reply from the receiving workstation
hence no realtime interaction between the two stations is needed.  However, if the network is busy and the
file is very large, the file transfer may take several hours for the data transmission to occur.

> ELECTRONIC MAIL: Electronic mail systems allow users to transfer memos and documents from one
workstation to another.  Time is not usually a factor.  Once a mail message has been sent the user's
workstation is available immediately to perform other activities--mail is expected to be delivered in a few
minutes or hours.  Again, without real time interaction between the workstations the load placed on the
network is light.  If the electronic mail system is used extensively, however, some systems can get sluggish.

> REMOTE APPLICATION USE: The use of an application which resides on a file  server on the other side
of the link puts a very heavy load on the WAN as the entire operational kernel of the application must be
uploaded by the local PC.  In addition, many applications assume that access to the file server will be almost
instantaneous and swap portions of the program between the drive and the PC every few minutes.  With most
applications this makes the use of anything slower than a T1 line impractical even then, program operation can
seem slow.  However, careful planning can frequently avoid this situation and if not, the NetWare Access
described below is an attractive alternative.

Novell has developed special server products, including the NetWare SQL Database, that reduce the amount
of data that is sent across the WAN during data base use.

> HOST ACCESS: A workstation can act as a terminal for accessing applications on a remote mainframe.
Terminal emulation requires a moderate level of interaction between the workstation and the host.  The
terminal must communicate with the host in real time, but since both the application and the data file are
on the host computer, the volume of data being transferred is small compared to remote application use.
How Much Data Will be Transferred and How Often?
In each of the above, the volume and frequency of data transfer have a direct impact on the type of LAN-to-
link needed.  For instance, even though remote application use is slow over a DDS line, if usage is light and
access is infrequent and the application small a DDS line may be adequate.  On the other hand if the company
only sends electronic mail over the network, but does so frequently and the users number in the ten thousands
a T1 line will be necessary to address the volume.

The following table gives some rules of thumb for determining the type of transmission medium most
appropriate for different types of use.  The table compares three types of lines: voice grade telephone or X.25
lines, which transfer data at up to 19.2 kbits/s: DDS lines which can go up to 56 kbit/s, (USA) and 64 kbits/s
(Europe) and t1 LINES AT 1.544 mBITS/S (USA) and CEPT lines at 2.048 Mbit/s (Europe).

As the frequency, volume, and complexity of data transfer go up the type of line used to carry the data requires
greater speeds.

                      Voice or X.25   DDS          T1
                      <=19 2 kbts     56 kbits     1.5 Mbits(USA)
                                                   64 kbits     2.0 Mbits
-------------------------------------------------------------------
File Transfer          Yes            Yes          Yes
Simultaneous Sess.     1.3            3.8          75
-------------------------------------------------------------------
Electronic Mail        Yes            Yes          Yes
Number of Users        500            <3,000       No Limit
Simultaneous Sess.     N/A            N/A
-------------------------------------------------------------------
Remote Application Use No             Very Slow    Adequate

-------------------------------------------------------------------
Host Access            Yes              Yes          Yes
Simultaneous Sess.     16               64           1,000
-------------------------------------------------------------------

What Kind of Sites Must be Connected and Where are They Located?
The number of possible variations is almost infinite.  Here are 3 common types:

1. Central Hub With Branch Offices
Each branch office could be connected to headquarters by a link with no direct connection between the
branches.  This configuration can often use voice grade lines but, in heavy traffic situations, it can benefit
from high speed DDS connections.







2. Several Regional Hubs
It is likely that each regional hub would like to be directly connected to every other regional hub.  This type
of configuration requires that the systems analyst give some thought as to which remote sites need to
communicate with each other.  It can be expensive to give everyone on the network equal access to everyone
else, and it usually isn't necessary.
A voice grade or DDS synchronous connections can be used to connect the branch offices to the hubs and
DDS or T1 synchronous connections to connect the regional hubs with the home office.

3. Two Major Sites
If two major sites would like to share data as if they were one large site a substantial volume of data would
have to pass through a central WAN backbone.  If the traffic was fairly light the WAN could be based on DDS
lines.  However, even moderately high volume situations would benefit from a T1 or fractional T1 line.

What are the Cost Constraints?
Many companies would like to provide all the communication and data sharing resources that are available.
In practice, however, the cost of hardware and telecommunications company charges force the systems analyst
to set priorities.

Many users are used to sending and receiving data at 2400 baud expect 19.2kbits or 56kbits to provide almost
instant transfer of data.  However, LAN-to-LAN connections are used for more demanding tasks than access to
a BBS or a service such as CompuServe and require fast transmission speeds for even moderate levels of
volume.
                            Voice or X.25     DDS          T1
                            <=19.2 kbts       56 kbits     1.5 Mbits(USA)
                                                 64 kbits     2.0 Mbits
Line Installation      $100              $300         $2,500
Monthly Rent           $20+              $90-500+     $300-2,600+
                       $3 per mile       $6 per mile  $14 per mile
$/Month for 500 miles  $100              $3,000       $9600
(The $ will vary with vendor, place, time, and volume)

Many companies have T1 lines installed already for voice communications.  One WAN connectivity option is
to use one channel of the line for data in order to evaluate whether a dedicated T1 line for data
communications is necessary.

The cost of installing a LAN-to-LAN link is offset by the increased productivity of people who communicate
better and the savings in other types of communications services such as facsimile express courier and voice.

How Much Technical Support is Available at Different Sites?
An asynchronous connection which uses voice grade phone lines with a remote product (like ONLAN which
comes with NetWare Access Server) requires almost no system maintenance at the branch office  site.  For a
branch office with no computer support staff, this is very important.  At the other end of the spectrum a wide
area network connecting two major sites, many minor sites dozens of file servers and thousands of workstations
requires an entire systems maintenance department.  Most wide area network sites fall in between these two
extremes.

Part of the decision to implement a wide area network involves the allocation of technical support personnel.
In some cases, even though a 56 to 64kbit/s X.25 synchronous line might increase the speed of data
transmission, the additional cost of supporting the X.25 link located at the remote site does not justify moving
from the voice grade line to the X.25 line.  In other cases the increased ability to communicate and share data
more than offsets the cost of technical personnel.

How Flexible Does The System Need To Be?
A flexible system is easily upgraded or changed.  LANS and other resources can be added and deleted without
major disruptions.  A flexible system also means that as users needs change users can get the information they
need without a great deal of extra expense.

Setting up inexpensive point-to-point voice grade connections can be a good way to get started but the system
can get very complex if the company connects a large number of branch offices without ever establishing
central or regional hubs for information sharing.  As more connections are required, what started as an easy
solution becomes complex and difficult to maintain as point-to-point voice grade connections are no longer
adequate.  At this point a WAN backbone may be needed.

Some extra expense in the beginning establishing a flexible system based on WAN backbone can pay off in
the long run for organizations whose systems are bound to grow.  Establishing regional hubs and a simple
topology offers increased flexibility.  Existing workstations can be given new access rights new workstations
can be added to a LAN and new LANs can be added to the wide area network.

As your network continues to expand, however, point-to-point connections centered around regional hubs
may become too complicated to manage.  As a next phase of WAN development you may need a network
service to manage the virtual connections on the WAN for you.  Then if the surcharges for relying on such
a service become too high, it may be more cost effective to set up your own private data network to manage
your WAN connections.

What are the Overall Goals of the Network?
Defining the goals of the WAN system is critical not only to the success of the system but to its cost
effectiveness and ability to accommodate change and growth.  Ultimately, the configuration of the wide area
network needs to reflect the goals of the organization as a whole.  Perhaps the engineers would be more in
touch with the needs of the marketplace if there were an E-mail system connecting the sales force and the
engineers. or maybe orders could be filled faster if there were a direct DDS line from a regional office to the
corporate headquarters so sales personnel could enter orders directly int the corporate mainframe.

Since it is often too expensive to connect everybody to everybody else for all types of data transfer the system
needs to reflect the strategic decisions made at the top management level.

After looking at all of these questions the analyst has a good profile of projected system and some of the
constraints involved.

The next step is to look at the Novell solutions.



NOVELL SOLUTIONS
> Point-to-Point voice grade lines
To connect LANs over voice grade telephone lines, Novell offers the NetWare Async Router.  The Async Router
is commonly used to connect branch offices to a regional hub or home office and with a WNIM board can
support speeds up to 19.2kbit/s.

> Multipoint X.25 Connections
NetWare LINK/X.25 allows multiple connections at up to 64kbit/s via an X.25 packet switching network.  In
the latter case, each regional office needs only a line into the nearest public data network (PDN) node saving
long distance telecommunications charges.  The PDN system then takes care of routing the data to the
destination site.  This type of link offers the advantage of flexibility without additional network management.
Link/X.25 is designed for use in PDN based multipoint wide area networks.

> High Speed Point-to-Point Connections
Novell offers two high speed LAN-to-LAN products for internetworking,  LINK/64 and Link/T1.  Link/64 is a
cost effective solution for those who expect their LAN-to-LAN connection speeds to remain at 64kbit/s and
below, while LINK/T1 offers a high performance solution for the full range of data transmission speeds from
9.6 kbit/s to 2 Mbit/s.

LINK/64 offers the same functionality as LINK/T1 but at a reduced maximum data rate.  Link/T1 is designed
to be used in high volume situations to connect remote hubs.  The LINK/T1 connections can become a high-
speed WAN backbone supporting a variety of configurations for home, regional and branch office.

A Different Method
Much of the functionality of a WAN can be attained by instead using a NetWare Access Server connected to
a NetWare LAN.  Each Access Server can be used to provide up to 16 connections and 16 DOS session to
remote sites.  The connections can be through individual dial up lines, multiplexers, X.25 service, or via IPX
across a synchronous line.  In each case, because Access Server only requires keystrokes and screen updates
to cross the lines an acceptable rate of speed can be attained for a lower line cost than a straight WAN
solution.  In particular, it makes "remote application use" feasible in situations that would otherwise require
a T1 line.

FOR FURTHER INFORMATION
       In Netwire Library 9 (communications)
               - TN6RUL.TXT for the "Rules of Thumb" for LINK/64 and LINK/T1.
               - ARORUL.TXT for the "Rules of Thumb" for the Asynch Router.
               - ACERU2.TXT for the "Rules of Thumb" for Access Server
       Call 800-NETWARE and ask for "Communications Product Information".