Network and Communications - ACS Publications - American

5 Network and Communications D O U G L A S ST.

CLAIR

Downloaded by RUTGERS UNIV on January 2, 2018 | http://pubs.acs.org Publication Date: October 5, 1984 | doi: 10.1021/bk-1984-0265.ch005

Digital Equipment Corporation, Stow, MA 01775

Frequently the data communications s o l u t i o n i s addressed independently of other o r g a n i z a t i o n a l communications needs. The knowledgeable user considers Data P r o c e s s i n g Networks a PART of the communications problem and rightly so. The entire communications for the o r g a n i z a t i o n c o n s i s t s of v o i c e , FAX, written, e t c . A l a r g e number of new s e r v i c e s are becoming a v a i l a b l e on the "computer network" that augment or replace e x i s t i n g systems. I n t e r o f f i c e mail for example has an analogue in the E l e c t r o n i c Mail systems a v a i l a b l e on computers. T h i s paper will a d d r e s s v a r i o u s a s p e c t s o f computer networks independently of the total communications s o l u t i o n for an o r g a n i z a t i o n . But, thought should be g i v e n to integration o f all c o m m u n i c a t i o n s i n your o r g a n i z a t i o n based on a v a i l a b l e resources and your unique needs. There are two p r i m a r y definitions f o r the term Network. One definition for a network d e s c r i b e s a few computers with l o t s of t e r m i n a l s . Such installations frequently have grown from a batch environment with a l a r g e c e n t r a l mainframe computer to which t e r m i n a l s have been added. The t e r m d a t a communications i s used to describe terminal (or terminal like) communications b e t w e e n t h e t e r m i n a l and h o s t . T h i s i s p e r h a p s t h e most mature communications a r e a . I t was d e v e l o p e d initially to support Teletype Equipment over telephone lines. Once computers began to support terminals this t e c h n o l o g y was a n a t u r a l adaptation. The s e c o n d more modern d e f i n i t i o n d e s c r i b e s a N e t w o r k c o m p r i s e d o f more c o m p u t e r s t i e d t o g e t h e r with r e l a t i v e l y f e w t e r m i n a l s on e a c h c o m p u t e r . T h i s second f o r m o f n e t w o r k became a r e a l i t y w i t h t h e m i n i computer r e v o l u t i o n was s p u r r e d by a c c e p t a n c e D i g i t a l s P D P - 8 and PDP-11 M i n i c o m p u t e r s i n the 1960s and d e v e l o p m e n t of Digitals Network A r c h i t e c t u r e (DNA) i n t h e 1970s. In order to c l a r i f y the distinction lets call the first f o r m o f " n e t w o r k " D a t a C o m m u n i c a t i o n s and t h e s e c o n d type a D i g i t a l Computer Network. 0097-6156/84/0265-0037$06.00/0 © 1984 American Chemical Society

Liscouski; Computers in the Laboratory ACS Symposium Series; American Chemical Society: Washington, DC, 1984.


38

C O M P U T E R S IN T H E

LABORATORY

A primary consideration for networking i s resource sharing. The n e w t w o r k i s c l e a r l y b e c o m i n g m o r e a n d m o r e like what was formerly the system. The various functions once l o c a t e d with i n a s i n g l e system (mass storage, computation, p r i n t i n g , etc) are now being s h a r e d and c a l l e d f i l e s e r v e r s , compute s e r v e r s , p r i n t servers, etc. If resources are cheap t h e n t h e y can be replicated. I f they are expensive resources must be shared. This law of economics dictates putting c o m p u t i n g power at t h e d e s k and s h a r i n g p r i n t i n g , and storage. The need for storage i s not related to computing power. Laboratory problems with t r i v i a l c o m p u t a t i o n a l need can acquire l a r g e amounts of data. S t o r a g e c o s t s a r e not as a m e n a b l e t o p r i c e r e d u c t i o n s as CPU power. T h e r e f o r e the network should offer the economy of large disks as a shared resource. An e f f i c i e n t n e t w o r k i n g scheme w o u l d a l s o a l l o w t h e u s e r t o e i t h e r move t h e e n t i r e f i l e o v e r t h e n e t w o r k o r o n l y the r e c o r d s on i n t e r e s t f r o m t h e f i l e . The s e c o n d a p p r o a c h , moving records, i s apt t o be preferred because i t minimizes t o t a l storage r e q u i r e m e n t s ( o n l y one copy of t h e f i l e i n t h e n e t ) and s i m p l i f i e s p r o c e d u r e s s i n c e the one c o p y i s u p d a t e d and there i s no q u e s t i o n about g e t t i n g and " o l d " c o p y . Level

1

Central. This highest level provides resources that are v i a b l e i n t e r m s o f t h e i r c o s t when t h e b e n e f i t s are realistic when s p r e a d a c r o s s the entire organization. I t i s a l s o the l e v e l at which i n f o r m a t i o n which i s of greatest s e n s i t i v i t y should reside. Level

2

D i v i s i o n . T h i s l e v e l merges the r e s o u r c e s necessary to s u p p o r t t w o o r m o r e d e p a r t m e n t s . The e m p h a s i s i s m o v i n g t o w a r d more m a n a g e r i a l f u n c t i o n s . H o w e v e r , i t i s a l s o the l o g i c a l l e v e l f o r resources whose b e n e f i t s are s u c h t h a t t h e c o s t i s o n l y r e a l i s t i c when s p r e a d a c r o s s a l l lower l e v e l s . Level

3

Laboratory. The l e v e l p r o v i d e s s u p p o r t t o m o r e t h a n one group. I t i s a s s u m e d t h a t d a t a c o l l e c t e d by several g r o u p s w i t h i n t h e d e p a r t m e n t i s n e c e s s a r i l y r e l a t e d and therefore resources at t h i s l e v e l support c o l l a t i n g and a n a l y z i n g data from s e v e r a l groups. In a d d i t i o n the i s the lowest l e v e l at which a d m i n i s t r a t i v e , f i n a n c i a l , and management f u n c t i o n s r e s i d e .


5.

ST. C L A I R

Level

Network

and

Communications

4

Department. A department i s l a r g e enough t o c o n t a i n more t h a n one g r o u p . S o m e t h i n g on t h e o r d e r o f s e v e n members a s a p r a c t i c a l minimum. The d e p a r t m e n t i s t h e l e v e l a t w h i c h a d m i n i s t r a t i o n and management become required.


Level

5

G r o u p . The g r o u p i s t h e s m a l l e s t u n i t t h a t c a n f u n c t i o n with essentially no a d m i n i s t r a t i v e o v e r h e a d . Groups therefore consist of approximately 3 members. P e o p l e a t t h i s l e v e l a r e i m p l e m e n t o r s . They p e r f o r m t h e t a s k s a s s o c i a t e d w i t h c o l l e c t i n g raw d a t a and l a b o r a t o r y a n a l y s i s . The o n l y f u n c t i o n t o p r o b a b l y bridge between g r o u p a n d d e p a r t m e n t w o u l d be c l e r i c a l . P r o j e c t or Task. This i s the smallest f u n c t i o n a l unit in the organization. One p e r s o n c o u l d b e r e s p o n s i b l e for several p r o j e c t s . There a r e three primary measures o f performance f o r a communications channel. They a r e d i s t a n c e , s p e e d , and cost. Speed and d i s t a n c e a r e c o n v e r s e l y r e l a t e d t o one another. That i s you can have speed o r d i s t a n c e b u t n o t both Cost i s d i r e c t l y r e l a t e d t o both. That i s t o say i f you want e i t h e r speed o r d i s t a n c e you a r e g o i n g t o pay f o r i t . unfortunately t h e r e l a t i o n s h i p i s n o t l i n e a r and i n c r e a s e s i n speed r e s u l t i n dramatic increases i n cost. The cost distance relationship i s not quite so dramatically non-linear. Laboratory

Front

Ends

The l a b o r a t o r y f r o n t e n d d e v i c e l o o k s c o n s p i c u o u s l y like a personal computer t o a network. In fact there are other interesting parallels between t h e growth of terminals to personal c o m p u t e r s and t h e e v o l u t i o n o f laboratory f r o n t ends. A t t h i s t i m e t h e m o s t common interfaces a r e RS-232, RS-422, IEEE-488, and p a r a l l e l interfaces. Many o f t h e s e a r e c l e a r l y a d o p t i o n s of t e r m i n a l i n t e r f a c e s made t o a d a p t t h e s e d e v i c e s t o "automatic data entry". However, t h e s e i n t e r f a c e s were never designed t o allow f o r Networking. They were i n t e n d e d t o make t h e d e v i c e s l o o k l i k e dumb t e r m i n a l s t o the host. But t h e advent o f micro processors and t h e i r implementation i n l a b o r a t o r y equipment c l e a r l y i n d i c a t e s their d i r e c t i o n continues t o p a r a l l e l the path followed by t h e t e r m i n a l t o w a r d a p e r s o n a l computer. They w i l l very quickly require t h e same s e r v i c e s t h a t personal computers r e q u i r e . The n e x t g e n e r a t i o n o f L a b d e v i c e s w i l l h a v e i n c r e a s e d mass s t o r a g e to fuller u t i l i z e the intelligence buried inside.


39

C O M P U T E R S IN T H E L A B O R A T O R Y

40 Personal

Computers

( D i s k Based

Systems)

A s i g n i f i c a n t d i f f e r e n c e i n communications requirements i s e x p e c t e d when s t o r a g e m e d i a i s d i s t r i b u t e d a l o n g w i t h personal computer systems. These configurations i n t r o d u c e a r e q u i r e m e n t f o r n e t w o r k i n g ( h o s t t o h o s t ) as opposed to data communications (terminal to host).


File

T r a n s f e r And

Task

To

Task

Communications

P e r s o n a l c o m p u t e r s w i l l r e q u i r e f i l e t r a n s f e r and t a s k to t a s k communications traffic from the network. The c h a r a c t e r i s t i c s o f n e t w o r k i n g are t h e r e f o r e marked by c o n s i d e r a b l e i n c r e a s e s i n b o t h t h e s p e e d and q u a n t i t y o f data to t r a n s f e r . In a d d i t i o n i t i s not the speed and power o f t h e c o m p u t e r s but t h e s i z e o f t h e s t o r a g e a t the ends o f the network link that dictate networking requirements. Mass S t o r a g e

Devices

In L a b o r a t o r y

Systems

The i n c l u s i o n o f mass S t o r a g e D e v i c e s i n L a b o r a t o r y instruments. The l a b o r a t o r y f r o n t e n d m a n u f a c t u r e s are c o n s i d e r i n g i n t r o d u c t i o n o f mass s t o r a g e i n t o their devices. The backup of these d e v i c e s i s g e n e r a l l y assumed t o t a k e p l a c e from W i n c h e s t e r D i s k s t o floppy diskettes ο streaming tapes. A cop out s o l u t i o n i s t o add a s e c o n d W i n c h e s t e r and p r o d u c e a shadow v o l u m e and h o p e b o t h d i s k s d o n ' t go b e l l y u p a t t h e s a m e t i m e . However, a communications link to a larger host i s c l e a r l y a v a s t l y s u p e r i o r s o l u t i o n t o any o f t h e local mass storage approaches (floppies, streaming tapes, shadow v o l u m e s ) . Problems

A s s o c i a t e d With

Local

Storage

In t h e c a s e o f f l o p p y d i s k e t t e s t h e backup p r o c e d u r e i s c l e a r l y cumbersome. A r c h i v a l s t o r a g e on s t r e a m i n g t a p e i s an u n k n o w n q u a n t i t y . I t i s necessary to handle 1/2 i n c h t a p e e v e r y 18 t o 24 m o n t h s t o a v o i d p r i n t through and m e c h a n i c a l p r o b l e m s . I t i s not c l e a r t h a t streaming t a p e s a r e n o t immune t o t h e same p r o b l e m s and will probably require the same t y p e o f h a n d l i n g . This handling is at this time not supported either by equipment, knowledge, or procedures f o r the streaming tape media. L o c a l b a c k u p o f W i n c h e s t e r d i s k s t o mass media a l s o o f f e r s the p r o s p e c t of i n c r e d i b l e l a b o r c o s t s with the proposed p r o l i f e r a t i o n of these d e v i c e s . A Networked

Solution

To

Distributed

Storage

If the a p p r o p r i a t e communications link existed there i s tremendous p o t e n t i a l f o r i t s a p p l i c a t i o n l a r g e number o f t h e s e W i n c h e s t e r b a s e d systems.


then in a

5.

ST. C L A I R

Networking

Network

and

Effects

41

Communications

on Data

Manipulation

A D i g i t a l Computer N e t w o r k a l l o w s t h e u s e r s t o p l a c e an i m p r e s s i v e amount o f c o m p u t e r power a n y w h e r e . In the research environment this allows the researcher to control t h e experiment, verify the data, e x t r a c t and record at t h e experiment site. The d r a m a t i c reduction i n t h e c o s t o f d a t a m a n i p u l a t i o n a l l o w s o n e t o p u t many computers where ever they a r e needed.


Networking

Effects

On D a t a

Access

The researcher can store the data at the point of c a p t u r e o r send t h e i n f o r m a t i o n over a Network t o a larger department l e v e l machine. Since the cost of storage i s considerable relative to the cost of computation every attempt should be made t o m i n i m i z e this cost. The c o s t of networking tends t o take a d v a n t a g e o f t h e same t e c h n o l o g y as data manipulation t h e r e f o r e t h e t r a n s p o r t o f i n f o r m a t i o n over t h e D i g i t a l C o m p u t e r N e t w o r k t o l a r g e r more e c o n o m i c a l s t o r a g e on d e p a r t m e n t l e v e l m a c h i n e s makes s e n s e . In addition the use o f a s m a l l m a c h i n e on s i t e a l l o w t h e amount o f d a t a t o be r e d u c e d by s e l e c t i n g t h e d a t a b e f o r e t r a n s m i s s i o n . A l s o use o f t h e departments machine t o c e n t r a l i z e t h e c o s t s o f backup and r e s t o r a t i o n o f data p r e v e n t s e r r o r s c a u s e d by a s c i e n t i s t t r y i n g t o do a c o m p u t e r o p e r a t o r s job. Wide Than

Area Networks 3000 M e t e r s )

Characteristics

(Distances

Greater

Wide area n e t w o r k s a r e d e f i n e d as t h o s e u t i l i z i n g t h e s e r v i c e s p r o v i d e d when t h e u s e r does n o t c o n t r o l t h e channel. F o r example few u s e r s c a n p u r c h a s e t h e r i g h t s to i n s t a l l a wire from a f a c i l i t y i n Boston, MA t o c o n n e c t a f a c i l i t y i n S t L o u i s , MO. T h e same t e c h n o l o g y i s g e n e r a l l y used i f you need t o communicate a c r o s s town or a c r o s s t h e s t r e e t you buy i t as a s e r v i c e . The d i v e s t a t u r e o f ATT may p r o d u c e a s t e p f u n c t i o n i n l o n g l i n e s c o s t s i n t h e near f u t u r e . The c o s t s o f wide a r e a n e t w o r k s e r v i c e s f r o m t h e t e l e p h o n e company have c a u s e d a number o f l a r g e u s e r s t o s t o p u s i n g t h e s e s e r v i c e s a n d buy s a t e l l i t e communications t o r e p l a c e l o n g l i n e s and broadband networks t o replace t h e s e r v i c e with i n a campus like facility. Cost o f these services i s regulated and s e t by t a r i f f . Recently the operating company i n Oklahoma requested a rate increase f o r residential telephone service attaching personal computers t o p u b l i c data base s e r v i c e s . The c o s t o f connection would i n c r e a s e t h e b a s i c r a t e approximately 5 t i m e s t h e v o i c e o n l y r a t e t h e r e i s no a p p a r e n t c h a n g e i n the a c t u a l s e r v i c e being p r o v i d e d . A similar rate f i l i n g i s b e i n g made i n T e x a s .


42 Local

C O M P U T E R S IN T H E

Area

LABORATORY

Networks

T h e s e n e t w o r k s a r e l i m i t e d t o d i s t a n c e s g r e a t e r t h a n 45 m e t e r s and l e s s t h a n 3000 m e t e r s . Examples of the t e c h n i q u e s e m p l o y e d i n c l u d e , PABX, E t h e r n e t , Broadband, F i b e r o p t i c s , and M i c r o w a v e . Clusters


T h i s d i s t a n c e , l e s s t h a n 45 m e t e r s , i s r o u g h l y 3 times the distance minicomputer i n t e r n a l busses ran in the 1960s. A b u s i s t h e name f o r t h e c o m m u n i c a t i o n s c h a n n e l i n s i d e the machine. Data r a t e f o r the Ethernet i s 10 m i l l i o n b i t s per second.

Broadband Connecting terminals t o h o s t s a p p e a r s t o be the most w i d e l y used area f o r broadband. A l l o w s t h e same c h a n n e l t o c a r r y v o i c e and v i d e o s i g n a l s . The s i g n a l r a t e s f o r broadband are not i m p r e s s i v e f o r data communications at t h i s time under 1 million b i t s per second f o r most applications. Fiber

Optics

This technology is attractive from a number of standpoints. E v e r y o n e w o u l d l i k e t o see c o o r d i n a t i o n of the material and c o n n e c t o r s so that migration in the field could take place as follows. For example a customer obtains a f i b e r o p t i c terminal to host link. Then r e p l a c e s t h e T e r m i n a l w i t h a Professional/Personal Computer. The s i n g l e P r o f e s s i o n a l / P e r s o n a l Computer i s replace by a c l u s t e r of several Professional/Personal Computers. The c l u s t e r expands to c o n t a i n a machine of the VAX class which is connected to the Professional/Personal C o m p u t e r s by E t h e r n e t and into a high performance cluster (a very high performance C l u s t e r o f l a r g e m a c h i n e s ) v i a t h e same F i b e r Optic Link. At each stage the terminal through High performance c l u s t e r the same f i b e r optic cable could handle the traffic. Planning ahead the r i g h t fiber optics material will allow migration s u c h as this to take place. Historical

Development

The development follows.

of

Of

Laboratory

Laboratory

Communications

Devices

has

proceeded

as

Phase 1 Manual Data E n t r y . Data i s keypunched manually and entered v i a c a r d s or paper tape to the computer. L a t e r Data i s entered v i a a t e r m i n a l to the computer.


5.

ST. C L A I R

Network

and

Communications

43


P h a s e 2 A n a l o g To D i g i t a l I n T h e H o s t . T h e l a b o r a t o r y manufacturers follow by connecting their devices directly to t h e data processing system. These Laboratory devices provide and analog signal. The Laboratory Device relies entirely on t h e h o s t f o r intelligence. The h o s t provides both control f o r an a n a l o g t o d i g i t a l (A/D) C o n v e r t e r and p r o c e s s i n g o f t h e data. A moderate improvement i n e f f i c i e n c y i s achieved by m u l t i p l e x i n g s e v e r a l A n a l o g s i g n a l s t o a s i n g l e A/D in t h e computer. P h a s e 3 D i g i t a l To H o s t . A/D c o n v e r s i o n m o v e s i n t o t h e l a b o r a t o r y d e v i c e a n d BCD o r A S C I I d i g i t s a r e s e n t i n s e r i a l or p a r a l l e l to the host. The l a b o r a t o r y d e v i c e now l o o k s l i k e a t e r m i n a l . The c o n t r o l l e r o p e r a t e s i n character i n t e r r u p t mode. Logical extensions of this technology have followed t h e manner i n which we interface terminals. The f i r s t interface i s a single c a r d i n t e r f a c e s and then m u l t i p l e i n t e r f a c e s p e r c a r d . However, both a r e i n t e r r u p t driven and c o n s i d e r a b l y l o a d t h e C P U . T h e n e x t l o g i c a l s t e p i s a DMA o r s i l o c o n t r o l l e r . T h e r e a r e " s t a n d a r d s " t h e R S - 2 3 2 - C ( i n many v a r i a t i o n s ) and t h e IEEE-488. Phase 4 I n t e l l i g e n t Lab Devices. Laboratory device manufactures offer intelligent devices with dedicated CPUs. To d o t h i s t h e y h a v e d e v e l o p e d s o f t w a r e e x p e r t i s e T h e s e l a b o r a t o r y d e v i c e s r e l a y on CPU manufacturers hardware and software. The laboratory device manufactures include a micro processor c h i p i nt h e device with s u f f i c i e n t power t o do t h e j o b t h a t o n c e took a PDP-8. I n a d d i t i o n t h e machine t r o u b l e - s h o o t s the p r o c e s s and o f f e r s r e m e d i a l a c t i o n t o t h e o p e r a t o r . This s u b s t a n t i a l l y changes t h e communications i n t e r f a c e . The data moved to the host i s substantially pre-processed. T h e a n a l y z e r i s now c a p a b l e o f s e n d i n g "packets" o f pre-processed data t o the host f o r more general analysis. Increased storage i s also made available. The a n a l y t i c a l d e v i c e now b e g i n s t o look more l i k e a d i s k t h a n a t e r m i n a l i n t e r m s o f p o t e n t i a l data t r a n s f e r rates. P h a s e 5 M u l t i p l e CPUs And I n t e l l i g e n t L a b o r a t o r y Devices On T h e N e t w o r k . Computer m a n u f a c t u r e r s have developed systems with multiple CPUs and m u l t i p l e operating systems ( i . e . A Network). The c o n s t r u c t i o n o f n e t w o r k s comprised completely of intelligent laboratory devices is a real possibility with the a v a i l a b i l i t y ofthe Ethernet Specification. Small l o c a l area networks o f l a b o r a t o r y d e i c e s w i l l d e v e l o p u s i n g E t h e r n e t and o t h e r technologies. Later these local networks will be interconnected probably v i a r o u t e r s and gateways t o broadband, S a t e l l i t e , and t e l e p h o n e facilities.


C O M P U T E R S IN T H E LABORATORY

44 Conclusions

The p a t h t h e d a t a p r o c e s s i n g m a n u f a c t u r e r s have taken i s b e i n g f o l l o w e d by t h e L a b o r a t o r y d e v i c e manufacturers. The laboratory devices are becoming increasingly intelligent. This trend implies that the personal c o m p u t e r may h a v e come t o o l a t e f o r many instruments. They w i l l u s e t h e c h i p s i n s t e a d . Manufacturers a r e now i n t e g r a t i n g c h i p s i n t o t h e i r d e v i c e s and w i l l soon n o t be satisfied with less than true host to host communications c a p a b i l i t y .


R E C E I V E D July 13, 1984


Network and Communications - ACS Publications - American

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