Δίκτυα 6_1-6_5 Ανεπίσημο Βοήθημα

8/3/2019 Δίκτυα 6_1-6_5 Ανεπίσημο Βοήθημα

http://slidepdf.com/reader/full/-61-65- 1/31

M e t d o s h D e d o m è n w n k a i D Ð k t u a U p o l o g i s t ¸ n -

T o A n e p Ð s h m o B o j h m a

M a n ¸ l h c K i a g i c , MSc

Q Q / Q Q / 2 0 0 8



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K j e g n s i o a n t Ð t u p o f è r e i t h n u p o g r a f t o u s u g g r a f è a :

1 h ' E k d o s h Q a n i , Q Q / Q Q / 2 0 0 8

D o k i m a s t i k Web Edition

[ Q w r Ð c A r Ð j m h s h ]

c2 0 0 8 M a n ¸ l h c K i a g i c

Copyright c2008 Manolis Kiagias. Permission is granted to copy,

distribute and/or modify this document under the terms of theGNU Free Documentation License, Version 1.2 or any later ver-sion published by the Free Software Foundation; with no InvariantSections, no Front-Cover Texts, and no Back-Cover Texts. A copyof the license is included in the section entitled “GNU Free Docu-mentation License”.

Copyright c2 0 0 8 M a n ¸ l h c K i a g i c . D Ð n e t a i d e i a a n t i g r a f c , d i a -

n o m c / k a i t r o p o p o Ð h s h c a u t o Ô t o u e g g r f o u k t w a p ì t o u c ì r o u c

t h c ' A d e i a c E l e Ô j e r h c T e k m h r Ð w s h c GNU

, ' E k d o s h 1 . 2 o p o i a s -

d p o t e e p ì m e n h c , ì p w c e k d Ð d e t a i a p ì t o ' I d r u m a E l e Ô j e r o u L o g i -

s m i k o Ô ; q w r Ð c S t a j e r T m m a t a , q w r Ð c K e Ð m e n a E m p r ì s j i o u E x w -

f Ô l l o u , k a i q w r Ð c K e Ð m e n a O p Ð s j i o u E x w f Ô l l o u . ' E n a a n t Ð g r a f o

t h c d e i a c a u t c p e r i l a m b n e t a i s t o t m m a m e t Ð t l o “GNU FreeDocumentation License”

.

T o b i b l Ð o a u t ì s t o i q e i o j e t j h k e s e LATEX2 e s e l e i t o u r g i k s u s t m a t a Linuxk a i

FreeBSD. O p h g a Ð o c k ¸ d i k a c t o u e Ð n a i d i a j è s i m o c s t i c d i k t u a k è c t o p o j e s Ð e c

p o u a n a f è r o n t a i p a r a k t w k a i m è s w mercurial repository .

E p i s k e f j e Ð t e t o d i k t u a k ì t ì p o t o u m a j m a t o c k a i k a t e b s t e t h n t e l e u t a Ð a è k d o s h

t o u b i b l Ð o u k a i d i o r j ¸ s e i c :

http://diktia.dyndns.org

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T o b i b l Ð o a u t ì a f i e r ¸ n e t a i s e ì s o u c k n o u n a u t ì p o u p i s t e Ô o u n k a i ì q i

a u t ì p o u n o m Ð z o u n o i l l o i s w s t ì . . .

O m ì n o c a l h j i n ì c n ì m o c e Ð n a i e k e Ð n o c p o u o d h g e Ð s t h n e l e u j e r Ð a ,

e Ð p e o I w n j a n ; D e n u p r q e i l l o c .

O G l r o c I w n j a n L Ð b i n g k s t o n , Richard Bach



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E i s a g w g s t h n P r ¸ t h ' E k d o s h t o u N è o u B o h -

j m a t o c

K a l ¸ c l j a t e s t h n p r ¸ t h è k d o s h t o u n è o u a n e p Ð s h m o u b o h j m a t o c g i a t o

m j h m a M e t d o s h D e d o m è n w n k a i D Ð k t u a U p o l o g i s t ¸ n t o o p o Ð o d i d s k e t a i

w c P a n e l l a d i k e x e t a z ì m e n o s t h n G ' T x h t w n E p a g g e l m a t i k ¸ n L u k e Ð w n . T o

b i b l Ð o a u t ì k a l Ô p t e i t h n e x e t a z ì m e n h Ô l h ì p w c a n a k o i n ¸ j h k e a p ì t o U p o u r -

g e Ð o P a i d e Ð a c g i a t o s q o l i k ì è t o c 2 0 0 8 - 2 0 0 9 . T o n è o a n e p Ð s h m o b o j h m a ,

m e a p l o p o i h m è n h a l l r t i a t e q n i k g l ¸ s s a , e u e l p i s t e Ð n a k a l Ô y e i t i c a t è -

l e i e c t o u s q o l i k o Ô e g q e i r i d Ð o u k a i n a b o h j s e i t o u c a p o f a s i s m è n o u c m a j h t è c

n a p e t Ô q o u n s t i c e x e t s e i c . H e p i t u q Ð a t o u a r q i k o Ô b o h j m a t o c , m e t è s s e r i c

s u n o l i k e k d ì s e i c , m a c o d h g e Ð n a p i s t e Ô o u m e ì t i o s t ì q o c a u t ì c e Ð n a i e f i k t ì c .

H è k d o s h a u t k u k l o f o r e Ð w c e l e Ô j e r h m e b s h t h n d e i a GNU FreeDocumentation License

p o u m p o r e Ð t e n a d i a b s e t e s t o P a r r t h m a B .

P r ì l o g o c t h c P r ¸ t h c ' E k d o s h c t o u a r q i k o Ô

b o h j m a t o c

P r o l o g Ð z e i o A n t ¸ n h c A j a n a s k h c , k a j h g h t c s t o n T o m è a O i -

k o n o m Ð a c , s u n d e l f o c t o u s u g g r a f è a s t o T E E K i s m o u .

K j e a p ì p e i r a a g w g c k a t a l g e i s e s q è s h m e t a x Ô p r o s ¸ p w n . H d i d a s k a l Ð a ,

d e n e Ð n a i e n è r g e i a k a t t h n o p o Ð a e p i k o i n w n o Ô n m ì n o o i e g k è f a l o i , a l l p o r e Ð a

p r o s w p i k c e p i k o i n w n Ð a c k a i a m o i b a Ð a c p r o s p j e i a c .

T o e g ¸ p o u d e n è q e i a p è n a n t Ð t o u k a n è n a s u g k e k r i m è n o e s Ô , a l l e Ð n a i

p e r i s t o i q i s m è n o a p ì m i a p l h j ¸ r a p e r i e q o m è n w n , d e n e Ð n a i d i ì l o u p a r ì n k a i h

s t i g m t o u e Ð n a i s t e r h m è n h a p ì p a r o u s Ð a . M i a p a r o u s Ð a ì m w c d e n e Ð n a i k t i

p o u x e f e Ô g e i k a i g l i s t r e i a l l e Ð n a i e k e Ð n o p o u k a t o i k e Ð a p è n a n t Ð m a c k a i

p e r i m è n e i t h n s u n n t h s h .

A n h p r a g m a t i k s u n n t h s h e Ð n a i h p o r e Ð a , k a t t h n o p o Ð a è n a c n j r w p o c

a g g Ð z e i è n a n l l o n n j r w p o s t o n p u r n a t o u , t ì t e o i m a j h t è c t o u M a n ¸ l h

e Ð q a n f è t o c m i a t r o m e r e u k a i r Ð a .

T o m ì n o p o u q r e i z o n t a i e Ð n a i t h n i k a n ì t h t a g i a a n t a p ì k r i s h . G i a t Ð h

e l e u j e r Ð a m è s a s t h n a g w g , e Ð n a i t o n a m p e i c s e d e s m ì . T o a n t Ð j e t o t o u e x a -

n a g k a s m o Ô , s Ô m f w n a m e t o n Buter

d e n e Ð n a i h e l e u j e r Ð a , a l l o d e s m ì c . D e n

j a m p o r o Ô s a m e q w r Ð c e l e u j e r Ð a , a l l a p ì m ì n h t h c d e n e Ð n a i q r h s i m o p o i s i m h .



vi



P e r i e q ì m e n a

I B i b l Ð o J e w r Ð a c 1

6 D Ð k t u a E u r e Ð a c P e r i o q c 3

6 . 1 E p e k t e Ð n o n t a c t o D Ð k t u o . . . . . . . . . . . . . . . . . . . . . 3

6 . 2 E p i l e g ì m e n e c T h l e f w n i k è c G r a m m è c . . . . . . . . . . . . . . . 4

6 . 3 M i s j w m è n e c G r a m m è c . . . . . . . . . . . . . . . . . . . . . . . 6

6 . 4 Q . 2 5 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

6 . 5 ISDN

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 0

II P a r a r t m a t a 1 3

A þ

GNU Free Documentation License1 5

1. APPLICABILITY AND DEFINITIONS . . . . . . . . . . . . . 162. VERBATIM COPYING . . . . . . . . . . . . . . . . . . . . . . 173. COPYING IN QUANTITY . . . . . . . . . . . . . . . . . . . . 174. MODIFICATIONS . . . . . . . . . . . . . . . . . . . . . . . . . 185. COMBINING DOCUMENTS . . . . . . . . . . . . . . . . . . . 196. COLLECTIONS OF DOCUMENTS . . . . . . . . . . . . . . . 197. AGGREGATION WITH INDEPENDENT WORKS . . . . . . 208. TRANSLATION . . . . . . . . . . . . . . . . . . . . . . . . . . 209. TERMINATION . . . . . . . . . . . . . . . . . . . . . . . . . . 2010. FUTURE REVISIONS OF THIS LICENSE . . . . . . . . . . 20ADDENDUM: How to use this License for your documents . . . . 20



viiiP E R I E Q O M E N A



K a t l o g o c S q h m t w n

6 . 1 S Ô n d e s h u p o l o g i s t ¸ n m è s w d i k t Ô o u PSTN

. . . . . . . . . . . 5

6 . 2 D Ð k t u o Q . 2 5 . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

6 . 3 D i e p a f è c b a s i k o Ô k a i p r w t e Ô o n t o c r u j m o Ô s t o ISDN

. . . . . 1 2



xK A T A L O G O S S Q H M A T W N



M è r o c I

B i b l Ð o J e w r Ð a c



K e f l a i o 6

D Ð k t u a E u r e Ð a c P e r i o q c

E i s a g w g

H e p i k r t h s h t h c q r s h c t w n m i k r o u p o l o g i s t ¸ n ( p r o s w p i k ¸ n u p o l o g i s t ¸ n )

s t i c e p i q e i r s e i c , o d g h s e g r g o r a s t h d h m i o u r g Ð a p o l l ¸ n t o p i k ¸ n d i k t Ô w n ,

m i k r o Ô m e g a l Ô t e r o u m e g è j o u c . W s t ì s o , k a j ¸ c k j e e p i q e Ð r h s h a n a p t Ô s s e -

t a i , g r g o r a d h m i o u r g e Ð t a i h a n g k h g i a e p i k o i n w n Ð a k a i m e t d o s h d e d o m è n w n

m e t a x Ô t w n u p o k a t a s t h m t w n t h c . H a n g k h a u t k a l Ô p t e t a i s m e r a a p ì t a

D Ð k t u a E u r e Ð a c P e r i o q c ( D E P ) . S t o m j h m a t h c B ' T x h c , e x e t s a m e d h

è n a m è r o c t o u e x o p l i s m o Ô p o u q r h s i m o p o i e Ð t a i s e a u t t a d Ð k t u a . S t o k e f l a i o

a u t ì j a a n a f e r j o Ô m e p l è o n s t i c t e q n o l o g Ð e c m e t d o s h c p o u q r h s i m o p o i o Ô n -

t a i s t a D E P , e x e t z o n t a c t ì s o t i c k l a s i k è c ( e p i l e g ì m e n o t h l e f w n i k ì d Ð k t u o ,

Q 2 5 k l p . ) ì s o k a i t i c p i o s Ô g q r o n e c ( Frame Relay, xDSL

, k l p ) .

6 . 1 E p e k t e Ð n o n t a c t o D Ð k t u o

T a t o p i k d Ð k t u a a p o t e l o Ô n m i a p o l Ô k a l l Ô s h e p i k o i n w n Ð a c s e p e r Ð p t w s h

p o u t o m è g e j o c t o u d i k t Ô o u e Ð n a i s q e t i k m i k r ì k a i k a t a l a m b n e i p e r i o r i s m è n h

g e w g r a f i k è k t a s h . G i a p a r d e i g m a m i a e t a i r Ð a p o u d i a j è t e i m ì n o è n a p o l u ì -

r o f o k t Ð r i o s e m i a p ì l h , e x u p h r e t e Ð t a i a p o t e l e s m a t i k a p ì è n a t o p i k ì d Ð k t u o .

' O t a n ì m w c h d r a s t h r i ì t h t a t h c e p e k t a j e Ð s e g e i t o n i k è c p ì l e i c , h a n g k h e p i -

k o i n w n Ð a c m e t a x Ô t w n u p o k a t a s t h m t w n t h c , a p a i t e Ð t h q r s h e n ì c D E P . T a

D E P e Ð n a i g n w s t k a i m e t o n A g g l i k ì ì r o Wide Area Networks (WAN)

.

Q r h s i m o p o i ¸ n t a c è n a D E P , e Ð n a i d u n a t ì n n a d i a s u n d è s o u m e m e t a x Ô t o u c

t a t o p i k d Ð k t u a k j e u p o k a t a s t m a t o c . G i a t o s k o p ì a u t ì q r h s i m o p o i e Ð t a i

k a t l l h l o c d i k t u a k ì c e x o p l i s m ì c ( g r a m m è c s Ô n d e s h c , modem

, d r o m o l o g h t è c

k . a . ) . S t i c g r a m m è c e n ì c D E P m p o r e Ð n a q r h s i m o p o i o Ô n t a i d Ð k t u a m e t a g w g c

( k u k l ¸ m a t o c p i o s u q n p a k è t o u ) , d o r u f o r i k è c k a i m i k r o k u m a t i k è c s u n d è s e i c ,

o p t i k è c Ð n e c , a k ì m a k a i s u s t m a t a k a l w d i a k c t h l e ì r a s h c .

O q r s t h c p o u q r h s i m o p o i e Ð è n a D E P d e n p r è p e i n a k a t a l a b a Ð n e i k a m m i

d i a f o r w c p r o c t o n t r ì p o q r s h c s e s q è s h m e è n a t o p i k ì d Ð k t u o . A u t ì



4 D Ð k t u a E u r e Ð a c P e r i o q c

s h m a Ð n e i ì t i t o D E P e Ð n a i d i f a n o w c p r o c t h l e i t o u r g Ð a t o u .

E Ð n a i a r k e t d Ô s k o l o ( e i d i k a p ì p o y h c k ì s t o u c ) g i a m i a e t a i r e Ð a n a e g -

k a t a s t s e i k a i n a d i a q e i r Ð z e t a i a p ì m ì n h t h c g r a m m è c e n ì c D E P . S u n j w c

e Ð n a i e u k o l ì t e r o n a n o i k i s e i t h q r s h t o u c a p ì k p o i o f o r è a p o u e i d i k e Ô e -

t a i s t i c e p i k o i n w n Ð e c ( p . q . t o n O T E ) o o p o Ð o c s u n j w c è q e i d h è t o i m h t h n

k a l w d i a k u p o d o m k a i m p o r e Ð n a k a l Ô y e i k j e s h m e Ð o t h c q ¸ r a c . O i t e q n o l o -

g Ð e c p o u q r h s i m o p o i o Ô n t a i s t i c u p h r e s Ð e c d i k t Ô w n e u r e Ð a c p e r i o q c ( u p h r e s Ð e c

WAN) ì p w c p a r è q o n t a i a p ì t o u c f o r e Ð c t h l e p i k o i n w n i ¸ n m p o r e Ð n a e Ð n a i :

• O i k l a s i k è c :

–E p i l e g ì m e n e c t h l e f w n i k è c g r a m m è c ( t o k l a s i k ì t h l e f w n i k ì d Ð k t u o )

–M ì n i m e c m i s j w m è n e c g r a m m è c

–G r a m m è c p o u q r h s i m o p o i o Ô n t o p r ì t u p o Q . 2 5

• a l l k a i o i p i o s Ô g q r o n e c :

– Frame Relay

– ISDN

– ATM

– xDSL

S h m e Ð w s h : A p ì t o 2 0 0 1 , u p r q e i s t h q ¸ r a m a c p l r h a p e l e u j è r w -

s h t w n t h l e p i k o i n w n i ¸ n . ' E t s i p l è o n k j e e t a i r Ð a m p o r e Ð n a e g k a j i s t

k a i n a d i a q e i r Ð z e t a i e x o p l i s m ì k a i g r a m m è c k a t l l h l e c g i a D E P . L ì g w

t o u a u x h m è n o u a n t a g w n i s m o Ô , u p r q e i k a i a n t Ð s t o i q h b e l t Ð w s h s t h n

p o i ì t h t a ( k a i t o k ì s t o c ) t w n p a r e q ì m e n w n t h l e p i k o i n w n i a k ¸ n u p h r e -

s i ¸ n .

6 . 2 E p i l e g ì m e n e c T h l e f w n i k è c G r a m m è c

T o g n w s t ì m a c t h l e f w n i k ì d Ð k t u o , t o o p o Ð o q r h s i m o p o i o Ô m e e d ¸ k a i p o l l

q r ì n i a g i a m e t d o s h f w n c , m p o r e Ð e p Ð s h c n a q r h s i m o p o i h j e Ð g i a m e t d o s h

d e d o m è n w n . T o t h l e f w n i k ì d Ð k t u o e Ð n a i g n w s t ì d i e j n ¸ c k a i m e t h n o n o m a s Ð a

PSTN, Public Switched Telephone Network , t o o p o Ð o j a m p o r o Ô s a m e n a m e -

t a f r s o u m e w c D h m ì s i o T h l e f w n i k ì E p i l o g i k ì ( M e t a g w g c )

D Ð k t u o . H è n n o i a t o u e p i l o g i k o Ô s q e t Ð z e t a i m e t h n d u n a t ì t h t a p o u è q o u -

m e n a e p i l è x o u m e m e p o i o s u n d r o m h t j a s u n o m i l s o u m e , s q h m a t Ð z o n t a c t o n

k a t l l h l o a r i j m ì k l s h c . J e w r ¸ n t a c t o w c d Ð k t u o m e t a g w g c , j a l è g a m e

ì t i a n k e i s t h n k a t h g o r Ð a t h c m e t a g w g c k u k l ¸ m a t o c e n ¸ o i s u n d è s e i c p o u

d h m i o u r g o Ô m e e Ð n a i p r o s w r i n è c .

M è s w t o u t h l e f w n i k o Ô d i k t Ô o u , m p o r o Ô m e n a è q o u m e m e t d o s h d e d o m è n w n

m e t a x Ô u p o l o g i s t ¸ n , q r h s i m o p o i ¸ n t a c t i c g r a m m è c t o u g i a n a d h m i o u r g s o u -

m e è n a D E P . U p r q o u n w s t ì s o k p o i o i p e r i o r i s m o Ð : T o t h l e f w n i k ì d Ð k t u o



6 . 2 E p i l e g ì m e n e c T h l e f w n i k è c G r a m m è c 5

s q e d i s t h k e g i a t h m e t d o s h f w n c , a n a l o g i k ¸ n d h l . d e d o m è n w n , k a i m l i s t a

m e m i k r ì e Ô r o c s u q n o t t w n ( ì s o q r e i z e t a i g i a n a m e t a d Ð d e t a i k a i n a a n a -

g n w r Ð z e t a i h a n j r ¸ p i n h f w n ) e n ¸ o i u p o l o g i s t è c m e t a d Ð d o u n g e n i k y h f i a k

s m a t a . G i a n a x e p e r s o u m e a u t ì t o n p e r i o r i s m ì , q r h s i m o p o i o Ô m e e i d i k è c s u -

s k e u è c g i a t h n s Ô n d e s h t w n u p o l o g i s t ¸ n m e t o t h l e f w n i k ì d Ð k t u o , t a g n w s t

m a c modem

.

T a modems

, g i a t a o p o Ð a è q o u m e a n a f e r j e Ð k a i s t o m j h m a t h c B ' t x h c ,

e Ð n a i s u s k e u è c o i o p o Ð e c m e t a t r è p o u n t o y h f i a k ì s m a t w n u p o l o g i s t ¸ n s e

a n a l o g i k ì t o o p o Ð o m p o r e Ð n a m e t a d o j e Ð m è s w t h c t h l e f w n i k c g r a m m c . T o

modemp o u b r Ð s k e t a i s t h n l l h m e r i t h c s Ô n d e s h c a n a l a m b n e i t h n a k r i b ¸ c

a n t Ð s t r o f h d i a d i k a s Ð a . A n è q e t e q r h s i m o p o i s e i modem

g i a t h n s Ô n d e s h s a c

s t o Internet

j a è q e t e p i j a n ì n a k o Ô s e i t o n q a r a k t h r i s t i k ì q o p o u p a r g e t a i

a p ì t h n m e t a t r o p ( d i a m ì r f w s h ) t o u s m a t o c s e a n a l o g i k ì . O u s i a s t i k t o

modemm e t a t r è p e i t o y h f i a k ì s m a s e q o p o u m p o r e Ð n a m e t a d o j e Ð m è s w t h c

t h l e f w n i k c g r a m m c .

S q m a 6 . 1 : S Ô n d e s h u p o l o g i s t ¸ n m è s w d i k t Ô o u PSTN

O l l o c p e r i o r i s m ì c t w n e p i l o g i k ¸ n t h l e f w n i k ¸ n s u n d è s e w n e Ð n a i o s q e t i -

k m i k r ì c r u j m ì c m e t d o s h c d e d o m è n w n p o u m p o r e Ð n a e p i t e u q j e Ð . H t a q Ô t h t a

d e n e Ð n a i s t a j e r k a j ¸ c e x a r t t a i a p ì p a r g o n t e c ì p w c h p o i ì t h t a t h c g r a m -

m c k a i t o u k u k l ¸ m a t o c p o u è q e i s q h m a t i s t e Ð m e t a x Ô t w n d Ô o u p o l o g i s t ¸ n

p o u e p i k o i n w n o Ô n . H m è g i s t h p r a k t i k t a q Ô t h t a m e t d o s h c p o u è q e i e p i t e u -

q j e Ð s e d Ð k t u o

PSTNe Ð n a i s m e r a t a 5 6

Kbps. P r è p e i n a s h m e i ¸ s o u m e ì t i h

t e q n o l o g Ð a a u t è q e i s t a m a t s e i n a a n a p t Ô s s e t a i , k a j ¸ c è q e i a n t i k a t a s t a j e Ð

a p ì p i o s Ô g q r o n e c k a i è t s i d e n a n a m è n e t a i n a a u x h j e Ð h t a q Ô t h t a t h c s t o

m è l l o n .

S m e r a , o i e p i l o g i k è c s u n d è s e i c q r h s i m o p o i o Ô n t a i g i a m e t d o s h d e d o m è n w n

p e r i o r i s m è n h c q r o n i k d i r k e i a c , ì t a n d e n d i k a i o l o g e Ð t a i t o e p i p l è o n k ì s t o c

q r s h c a f i e r w m è n h c g r a m m c k p o i a c l l h c p i o s Ô g q r o n h c t e q n o l o g Ð a c .




P l e o n e k t m a t a M e i o n e k t m a t a B a s i k Q r s h

U y h l D i a j e s i m ì t h t a M i k r T a q Ô t h t a A p o m a k r u s m è n h P r ì -

s b a s h

M i k r T a q Ô t h t a M e t a b l h t P o i ì t h t a

k a i A x i o p i s t Ð a

E f a r m o g è c q w r Ð c a p a i -

t s e i c u y h l c t a q Ô t h -

t a c

P Ð n a k a c 6 . 1 : Q a r a k t h r i s t i k e p i l e g ì m e n w n g r a m m ¸ n

G n w s t è c e f a r m o g è c t h c e Ð n a i h p r ì s b a s h s t o Internet

s e l l e c on-line

u p h r e s Ð e c q a m h l c t a q Ô t h t a c , h s Ô n d e s h k p o i o u a p o m a k r u s m è n o u u p o l o g i -

s t ( p . q . e n ì c f o r h t o Ô ) m e t o t o p i k ì d Ð k t u o m i a c e t a i r Ð a c , k a j ¸ c k a i h t l e -

e r g a s Ð a . A k ì m a , o i e p i l o g i k è c s u n d è s e i c q r h s i m o p o i o Ô n t a i s u q n w c e f e d r i k è c

s e p e r Ð p t w s h b l b h c m i a c m ì n i m h c g r a m m c .

6 . 3 M i s j w m è n e c G r a m m è c

S t i c e p i l e g ì m e n e c g r a m m è c , h s Ô n d e s h d h m i o u r g e Ð t a i k a t a p a Ð t h s h , ì t a n d h l .

p r ì k e i t a i n a q r h s i m o p o i h j e Ð . A n j è l o u m e ì m w c n a è q o u m e s u n è q e i a m i a s Ô n d e -

s h m e t a x Ô d Ô o s h m e Ð w n , m p o r o Ô m e n a q r h s i m o p o i s o u m e m i a m i s j w m è n h g r a m -

m . O i m i s j w m è n e c ( m ì n i m e c ) g r a m m è c , p r o s f è r o n t a i g i a e n o i k Ð a s h a p ì t o u c

d i f o r o u c t h l e p i k o i n w n i a k o Ô c f o r e Ð c .

O i m i s j w m è n e c g r a m m è c e Ð n a i g e n i k d i a j è s i m e c 2 4 ¸ r e c t o 2 4 w r o , 7 m è r e c

t h b d o m d a k a i e Ð n a i k a t l l h l e c g i a p e r i p t ¸ s e i c p o u q r e i a z ì m a s t e a d i l e i p t h

s Ô n d e s h m e t a x Ô d Ô o s h m e Ð w n . S t h g l ¸ s s a t w n t h l e p i k o i n w n i ¸ n , o i g r a m m è c

a u t è c o n o m z o n t a i k a i e u j e Ð e c g i a t Ð s e a n t Ð j e s h m e t i c e p i l e g ì m e n e c , t a s h m e Ð a

p o u e n ¸ n o u n e Ð n a i s t a j e r ( d e n u p r q e i h d u n a t ì t h t a k l s h c l l o u s u n d r o m h -

t ) . M i s j w m è n e c g r a m m è c q r h s i m o p o i o Ô n t a i p . q . s e e t a i r Ð e c g i a s Ô n d e s h t w n

u p o k a t a s t h m t w n m e t a x Ô t o u c , s t i c t r p e z e c g i a s Ô n d e s h m e t o u c k e n t r i k o Ô c

u p o l o g i s t è c k l p . k a i a k ì m a g i a t h s Ô n d e s h m e g l w n e t a i r i ¸ n m e t o Internet

.

G e n i k , u p r q o u n d Ô o k a t h g o r Ð e c m i s j w m è n w n g r a m m ¸ n :

•O i a n a l o g i k è c m i s j w m è n e c g r a m m è c : G i a n a l e i t o u r g s o u n , q r e i z e t a i

h q r s h modem

ì p w c k a i s t i c a n t Ð s t o i q e c e p i l o g i k è c . S e s q è s h m e

t i c e p i l o g i k è c w s t ì s o , p r o s f è r o u n k a l Ô t e r h p o i ì t h t a k a i a x i o p i s t Ð a ,

t o o p o Ð o m e t a f r z e t a i k a i s e m e g a l Ô t e r e c t a q Ô t h t e c . W s t ì s o h q r s h

t h c a n a l o g i k c t e q n o l o g Ð a c a n a g k a s t i k d h m i o u r g e Ð s a f ì r i a s t a p a -

r a p n w q a r a k t h r i s t i k . O i g r a m m è c a u t è c e Ð n a i s q e t i k a k r i b è c g i a t Ð o

f o r è a c e p i k o i n w n i ¸ n p o u p a r è q e i t h n u p h r e s Ð a a n a g k z e t a i n a d e s m e Ô s e i

m ì n i m a k p o i o u c p ì r o u c g i a t h l e i t o u r g Ð a t h c , k a i a u t o Ð d e n m p o r o Ô n n a

q r h s i m o p o i h j o Ô n g i a k a n è n a l l o s k o p ì .



6 . 3 M i s j w m è n e c G r a m m è c 7

• O i y h f i a k è c m i s j w m è n e c g r a m m è c q r h s i m o p o i o Ô n t a i ì t a n a p a i t e Ð t a i u y h -

l ì t e r h p o i ì t h t a k a i t a q Ô t h t a e p i k o i n w n Ð a c k a i e u k o l ì t e r h d i a q e Ð r i s h .

O i t a q Ô t h t e c t w n y h f i a k ¸ n g r a m m ¸ n k u m a Ð n o n t a i a p ì 1 9 , 2 Kbps

w c k a i

4 5 Mbps

. U p r q e i g e n i k h k a t h g o r Ð a g r a m m ¸ n E p o u a f o r t o E u r w -

p a i k ì p r ì t u p o , k a i h s e i r T p o u a f o r t o A m e r i k a n i k ì . M i a s u q n

e p i l o g g i a t h n E u r ¸ p h e Ð n a i h g r a m m E 1 m e t a q Ô t h t a 2 , 0 4 8 Mbps

e n ̧

g i a t h n B . A m e r i k k a i I a p w n Ð a h g r a m m T1

m e t a q Ô t h t a 1,544Mbps

.

G i a m i k r ì t e r e c t a q Ô t h t e c m p o r e Ð n a q r h s i m o p o i h j e Ð p o s o s t ì k p o i a c

g r a m m c E 1 T 1 s e p o l l a p l s i a t w n 64Kbps

.

S h m e Ð w s h : H y h f i a k g r a m m E 1 e p i t r è p e i t h m e t d o s h 3 2 k a -

n a l i ¸ n d e d o m è n w n m è s w d i s Ô r m a t h c t h l e f w n i k c g r a m m c . S e k j e

k a n l i g Ð n e t a i d e i g m a t o l h y Ð a ( l a m b n e t a i d h l . t i m ) 8 0 0 0 f o r è c t o

d e u t e r ì l e p t o ( R u j m ì c d e i g m a t o l h y Ð a c 8Khz

) . T o k j e d e Ð g m a k w -

d i k o p o i e Ð t a i q r h s i m o p o i ¸ n t a c 8bits

. ' E t s i è q o u m e s u n o l i k r u j m ì

8000 X 8 bits = 64000 bpsd h l .

64Kbps. S u n o l i k h g r a m m m p o -

r e Ð n a m e t a d ¸ s e i 32X64Kbps=2,048Mbps

.


U y h l D i a j e s i m ì t h t a M e g l o m h n i a Ð o p g i o

t è l o c

D i a s Ô n d e s h t o p i k ¸ n

d i k t Ô w n p o u b r Ð s k o n t a i

s e m e g l h a p ì s t a s h

A s f l e i a , k a j ¸ c h

g r a m m a n k e i a p o k l e i -

s t i k s t o q r s t h

H y h f i a k g r a m m d e n

m p o r e Ð n a l e i t o u r g s e i

s e q a m h l ì t e r h t a q Ô t h -

t a s e p e r Ð p t w s h b l -

b h c , r a e Ð n a i d Ô s k o l h

h e f e d r e Ð a .

M ì n i m h s Ô n d e s h s t o

Internet

S e p e r Ð p t w s h d i a r k c

m e t d o s h c m e g l h c p o -

s ì t h t a c d e d o m è n w n , h

q r s h m p o r e Ð n a e Ð -

n a i o i k o n o m i k s u m f è -

r o u s a .

U y h l è c t a q Ô t h t e c m e -

t d o s h c

P Ð n a k a c 6 . 2 : Q a r a k t h r i s t i k m i s j w m è n w n g r a m m ¸ n

K a j ¸ c h m e t d o s h s t i c g r a m m è c T k a i E e Ð n a i e x ì l o k l r o u y h f i a k , d e n

g Ð n e t a i q r s h modem

. G i a t h n s Ô n d e s h t w n s t a j m ¸ n t o u d i k t Ô o u p n w s t h

g r a m m k a j ¸ c k a i t h m e t a t r o p t w n y h f i a k ¸ n d e d o m è n w n p o u p a r g o u n s e

m o r f k a t l l h l h g i a m e t d o s h , q r h s i m o p o i e Ð t a i m i a s u s k e u p o u o n o m z e t a i

M o n d a E x u p h r è t h s h c K a n a l i o Ô - D e d o m è n w n , (Channel Service Unit / Data

Service Unit, CSU/DSU . T o y h f i a k ì s m a p o u a p a i t e Ð t a i a p ì t i c g r a m m è c




e Ð n a i d i p o l i k ì , a n t i p r o s w p e Ô e i d h l . t o 0 k a i t o 1 m e d i a m e t r i k a n t Ð j e t e c

t i m è c t s h c ( p . q . + 3 k a i - 3 V ) . T o CSU/DSU p a r è q e i e p Ð s h c h l e k t r o n i k

k u k l ¸ m a t a p r o s t a s Ð a c t o u e x o p l i s m o Ô t o u p a r o q è a t h c u p h r e s Ð a c .

' E n a b a s i k ì m e i o n è k t h m a t w n y h f i a k ¸ n m i s j w m è n w n g r a m m ¸ n , e Ð n a i h a d u -

n a m Ð a t o u c n a l e i t o u r g s o u n s e q a m h l ì t e r h t a q Ô t h t a s e p e r Ð p t w s h b l b h c

( k t i p o u e Ð n a i p o l l è c f o r è c d u n a t ì n s e a n a l o g i k g r a m m ) . A n t Ð j e t a , h

l e i t o u r g Ð a t o u c d i a k ì p t e t a i t e l e Ð w c .

H k o s t o l ì g h s h t h c m i s j w m è n h c g r a m m c g Ð n e t a i a n l o g a m e t h n a p ì s t a s h

t w n s h m e Ð w n p o u s u n d è e i k a i t h n e p i j u m h t m è g i s t h t a q Ô t h t a , k a i ì q i m e t o n

ì g k o t w n d e d o m è n w n p o u k i n o Ô n t a i . S e p e r i p t ¸ s e i c p o u q r e i z e t a i n a s u n d è -

s o u m e m i k r ì a r i j m ì s h m e Ð w n , k a i o i s u n d è s e i c p r ì k e i t a i n a q r h s i m o p o i o Ô n t a i

g i a p o l l è c ¸ r e c t h n h m è r a , o i m i s j w m è n e c g r a m m è c m p o r e Ð n a e Ð n a i s u m f è r o u s e c

a p ì p o y h k ì s t o u c . T a q a r a k t h r i s t i k t o u c f a Ð n o n t a i s t o n p Ð n a k a 6 . 2 .

6 . 4 Q . 2 5

T o Q . 2 5 e Ð n a i m i a t e q n o l o g Ð a m e t a g w g c p a k è t w n , t a d e d o m è n a d h l . m e t a d Ð -

d o n t a i s t o d Ð k t u o s e p o l l m i k r k o m m t i a . ' E n a d Ð k t u o Q . 2 5 a p o t e l e Ð t a i a p ì

p o l l o Ô c k ì m b o u c m e t a g w g c p a k è t w n ( Packet Switching Nodes

) , o i o p o Ð o i

d r o m o l o g o Ô n t a p a k è t a ¸ s t e n a f t s o u n s t o n p r o o r i s m ì t o u c .

H d i e p a f ( o t r ì p o c p o u s u n d è o n t a i ) o e x o p l i s m ì c t o u q r s t h m e t o d Ð -

k t u o m e t a g w g c p a k è t w n Q . 2 5 p e r i g r f e t a i a p ì t o p r ì t u p o Q . 2 5 t o o p o Ð o k a i

l e i t o u r g e Ð s t a t r Ð a k a t ¸ t e r a e p Ð p e d a t o u m o n t è l o u OSI. S t o Q . 2 5 o e x o p l i -

s m ì c t o u q r s t h ( t o t e r m a t i k ì t o u ) a n a f è r e t a i w c T e r m a t i k ì c E x o p l i s m ì c

D e d o m è n w n Data Terminal Equipment, DTE

e n ¸ o k ì m b o c m e t a g w g c p a -

k è t w n s t o n o p o Ð o s u n d è e t a i t o DTE

o n o m z e t a i DCE, Data Communication

Equipment E x o p l i s m ì c E p i k o i n w n Ð a c D e d o m è n w n . A p a r a Ð t h t h p r o u p ì j e s h

g i a n a s u n d e j e Ð t e r m a t i k ì c e x o p l i s m ì c q r s t h s t o Q . 2 5 e Ð n a i n a è q e i d u n a -

t ì t h t a d h m i o u r g Ð a c p a k è t w n . S u n j w c t a a s Ô g q r o n a ( s e i r i a k ) t e r m a t i k

d e n è q o u n a u t t h d u n a t ì t h t a k a i g i a t o s k o p ì a u t ì q r h s i m o p o i o Ô m e g i a t h

s Ô n d e s h t o u c m i a M o n d a S u n a r m o l ì g h s h c / A p o s u n a r m o l ì g h s h c P a k è t w n

g n w s t k a i w c PAD, Packet Assembler Dissambler

.

A r q i k , t a d Ð k t u a Q . 2 5 q r h s i m o p o i o Ô s a n a p l è c t h l e f w n i k è c g r a m m è c g i a

t h n m e t d o s h t w n d e d o m è n w n . O i t h l e f w n i k è c g r a m m è c d e n p a r è q o u n k a l

a x i o p i s t Ð a k a i d h m i o u r g o Ô n p o l l l j h k a t t h m e t d o s h . T o p r ì t u p o Q . 2 5

p r o b l è p e i a u t t h n p i j a n ì t h t a k a i d i a j è t e i a r k e t p o l Ô p l o k o u c m h q a n i s m o Ô c

a n Ð q n e u s h c k a i d i ì r j w s h c t w n l a j ¸ n . T o m e i o n è k t h m a t w n m e j ì d w n a u t ¸ n

e Ð n a i ì t i k a t a n a l ¸ n o u n s q e t i k m e g l o m è r o c t o u c e Ô r o u c z ¸ n h c t h c g r a m m c

k a i e p i d r è t s i a r n h t i k s t h n t a q Ô t h t a m e t d o s h c . S t i c m è r e c m a c , o i g r a m m è c

e p i k o i n w n Ð a c e Ð n a i a r k e t p i o a x i ì p i s t e c , k a i m p o r o Ô m e s t h n p r a g m a t i k ì t h t a

n a q r h s i m o p o i s o u m e p r w t ì k o l l a m e p o l Ô l i g ì t e r o u c e l è g q o u c ( e x è l i x h t o u



6 . 4 Q . 2 5 9

S q m a 6 . 2 : D Ð k t u o Q . 2 5

Q . 2 5 e Ð n a i t o Frame Relay

p o u j a d o Ô m e p a r a k t w ) .

T a d Ð k t u a Q . 2 5 p a r è q o u n u p h r e s Ð e c m e q r s h n o h t o Ô k u k l ¸ m a t o c , d h l .

m e s Ô n d e s h ( connection oriented

) . ' O p w c x è r o u m e , ì t a n q r h s i m o p o i e Ð t a i n o h -

t ì k Ô k l w m a , o i k ì m b o i p r i n x e k i n s o u n n a m e t a d Ð d o u n d e d o m è n a b r Ð s k o u n m i a

s u g k e k r i m è n h d i a d r o m m è s a a p ì t o u c e n d i m e s o u c k ì m b o u c t o u d i k t Ô o u , t h n

o p o Ð a k a i a k o l o u j o Ô n ì l a t a p a k è t a t h c m e t d o s h c .

T o Q . 2 5 e p i t r è p e i t h n Ô p a r x h t ì s o p r o s w r i n ¸ n ( m e t a g ¸ g i m w n ) n o h t ¸ n

k u k l w m t w n ( g n w s t k a i w c SVC, Switched Virtual Circuits

) ì s o k a i m ì -

n i m w n n o h t ¸ n k u k l w m t w n

PVC, Permanent Virtual Circuit . K j e n o h t ì

k Ô k l w m a p r o s d i o r Ð z e t a i a p ì è n a m o n a d i k ì a r i j m ì VCI, Virtual Channel Iden-

tifier, k a i m p o r e Ð n a e x u p h r e t e Ð m i a d i a f o r e t i k s Ô n d e s h . A p ì t h n Ð d i a f u s i k

s Ô n d e s h m p o r e Ð n a q r h s i m o p o i e Ð t a i a p ì p o l l n o h t k u k l ¸ m a t a , m e t h q r s h

P o l u p l e x Ð a c s t o Q r ì n o . ' E t s i è q o u m e k a l Ô t e r h e k m e t l l e u s h t o u d i a j è s i m o u

e Ô r o u c z ¸ n h c .

S h m e Ð w s h : T a p r o s w r i n n o h t k u k l ¸ m a t a ( SVC

) d h m i o u r g o Ô n t a i

ì t a n a p a i t e Ð t a i s Ô n d e s h k a i t e r m a t Ð z o n t a i m e t h l x h t h c m e t d o s h c

d e d o m è n w n , ì p w c s u m b a Ð n e i k a i s t i c t h l e f w n i k è c k l s e i c . K j e t e r -

m a t i k s u s k e u ( DTE

) è q e i è n a m o n a d i k ì a n a g n w r i s t i k ì a r i j m ì ( d i e Ô -

j u n s h ) p o u q r h s i m o p o i e Ð t a i ì p w c k a i è n a c t h l e f w n i k ì c a r i j m ì c . G i a

t h n a p o k a t s t a s h t h c s Ô n d e s h c , t o a p o m a k r u s m è n o DTE

k a l e Ð t o

l l o q r h s i m o p o i ¸ n t a c t o n a r i j m ì a u t ì k a i a k o l o u j e Ð m i a d i a d i k a s Ð a

e Ô r e s h c t h c d i a d r o m c ( n o h t o Ô k u k l ¸ m a t o c ) p o u j a a k o l o u j s o u n t a

p a k è t a t h c m e t d o s h c . M e t h l x h t h c m e t d o s h c t o n o h t ì k Ô k l w m a

k a t a r g e Ð t a i . T a m ì n i m a ( PVC

) n o h t k u k l ¸ m a t a d e n a p a i t o Ô n k l s h

g i a n a l e i t o u r g s o u n . D h m i o u r g o Ô n t a i a p ì t o f o r è a p o u p a r è q e i t h n

u p h r e s Ð a k a i p a r a m è n o u n s u n è q e i a s e l e i t o u r g Ð a ( ì p w c k a i o i m ì n i m e c

m i s j w m è n e c g r a m m è c ) .

T o k ì s t o c t o u Q . 2 5 e Ð n a i p r o s i t ì , a f o Ô h q r è w s h g Ð n e t a i a n l o g a m e t h n



1 0 D Ð k t u a E u r e Ð a c P e r i o q c

p o s ì t h t a t w n d e d o m è n w n p o u d i a k i n j h k e . T o k ì s t o c e Ð n a i m i k r ì , e f o s o n

m e t a d Ð d o u m e m i k r p o s ì t h t a d e d o m è n w n s e a r a i d i a s t m a t a . S t i c m è r e c m a c

u p r q o u n f u s i k p i o s Ô g q r o n e c t e q n o l o g Ð e c m e t d o s h c ( ì p w c t o Frame Relay

k a i t o ISDN

) a l l t o Q . 2 5 e Ð n a i a k ì m a s e e u r e Ð a q r s h s e p o l l m è r h t o u

k ì s m o u , k a j ¸ c h t e q n o l o g Ð a t o u e Ð n a i k a l g n w s t , p r o s i t , k a i p o l l è c f o r è c

h m ì n h d i a j è s i m h . T a q a r a k t h r i s t i k t o u Q . 2 5 f a Ð n o n t a i s t o n p Ð n a k a 6 . 3 .


A x i o p i s t Ð a M i k r t a q Ô t h t a E f a r m o g è c t e r m a t i k o Ô

p r o c k e n t r i k ì u p o l o g i -

s t

M i k r ì k ì s t o c s e p e r Ð -

p t w s h s p o r a d i k c q r -

s h c

A r g a p ì k r i s h

D i a j è s i m h p a n t o Ô K a t l l h l h m ì n o g i a

u p h r e s Ð e c d e d o m è n w n

H d i a q e Ð r i s h t o u d i -

k t Ô o u e u r e Ð a c p e r i o q c

g Ð n e t a i a p ì t o n f o r è a

P Ð n a k a c 6 . 3 : Q a r a k t h r i s t i k Q . 2 5

6 . 5 ISDN

E k t ì c a p ì t i c k l a s i k è c u p h r e s Ð e c t h l e f w n Ð a c ( f w n c ) , t a t e l e u t a Ð a q r ì n i a

p a r o u s i s t h k e m e g l h z t h s h g i a p a r o q k a i l l w n u p h r e s i ¸ n ( m e t d o s h d e -

d o m è n w n , e i k ì n a c , video

) , O i d i f o r o i f o r e Ð c t h l e p i k o i n w n Ð w n a n a g k s t h k a n

n a d h m i o u r g s o u n e x e i d i k e u m è n a d Ð k t u a ( e k t ì c a p ì t o t h l e f w n i k ì p o u u p r -

q e ) g i a t h n m e t d o s h t w n a n t Ð s t o i q w n d e d o m è n w n . G i a p a r d e i g m a , o O T E

a n è p t u x e t a d Ð k t u a Hellaspac

k a i Hellascom

g i a m e t d o s h d e d o m è n w n u p o -

l o g i s t ¸ n . A k ì m a d h m i o u r g j h k a n d Ð k t u a g i a m e t d o s h d e d o m è n w n k e i m è n o u

( telex

, t o o p o Ð o ì m w c è q e i p l è o n k a t a r g h j e Ð ) , d Ð k t u a k a l w d i a k c t h l e ì r a s h c

k . a . H a n p t u x h x e q w r i s t ¸ n d i k t Ô w n g i a k j e d i a f o r e t i k ì e Ð d o c u p h r e s Ð a c ,

è q e i m e i o n e k t m a t a ì p w c :

•M e g l o k ì s t o c d i a q e Ð r i s h c k a i s u n t r h s h c t w n d i a f o r e t i k ¸ n t e q n o l o -

g i ¸ n a p ì k j e t h l e p i k o i n w n i a k ì f o r è a .

• A u x h m è n o k ì s t o c g i a t o n t e l i k ì q r s t h , o o p o Ð o c p r è p e i n a s u n t h r e Ð

d i a f o r e t i k ì e x o p l i s m ì g i a k j e u p h r e s Ð a , k a i n a p l h r ¸ n e i s u n d r o m

s t o n t h l e p i k o i n w n i a k ì f o r è a . M e d e d o m è n o ì t i o f o r è a c è q e i p o l l

è x o d a g i a t a d Ð k t u a a u t , o i t i m è c t w n s u n d r o m ¸ n e Ð n a i a n t Ð s t o i q a a r k e t

a u x h m è n e c .



6 . 5 ISDN

1 1

• T a p a r a p n w o d h g o Ô n s u n j w c s e a p o j r r u n s h t h c e m p o r i k c a n p t u -

x h c .

T a p a r a p n w p r o b l m a t a è r q e t a i n a l Ô s e i t o Y h f i a k ì D Ð k t u o E n o p o i h -

m è n w n U p h r e s i ¸ n Integrated Services Digital Network, ISDN

. T o ISDN

e p i t r è p e i t h m e t d o s h f w n c , e i k ì n a c , video

k a i d e d o m è n w n s e y h f i a k m o r f

q r h s i m o p o i ¸ n t a c t h n u p r q o u s a u p o d o m d i s Ô r m a t w n t h l e f w n i k ¸ n k a l w d Ð w n .

E p i s m a n s h : T a d i s Ô r m a t a t h l e f w n i k k a l ¸ d i a ( t a k o i n t h l e f w -

n i k k a l ¸ d i a t o u O T E p o u k a t a l g o u n s t a s p Ð t i a m a c ) a p o t e l o Ô n m i a

t e r s t i a u p o d o m p o u a n a p t Ô q j h k e s e d i s t h m a p o l l ¸ n e t ¸ n g i a n a

e x u p h r e t s e i t i c a n g k e c t h c k l a s i k c t h l e f w n Ð a c ( g n w s t k a i w c

POTS, Plain Old Telephone System, t o a p l ì d h l . t h l e f w n i k ì d Ð -

k t u o ) . O i g r a m m è c a u t è c d e n è q o u n s q e d i a s t e Ð e i d i k g i a m e t d o s h

d e d o m è n w n , k a j ¸ c t o t h l e f w n i k ì d Ð k t u o m e t a d Ð d e i f w n m e k a j a r

a n a l o g i k ì t r ì p o ( k a i m e a r k e t m i k r ì e Ô r o c z ¸ n h c , a p ì 3 0 0 HZ

w c

3 4 0 0 HZ

) . W s t ì s o , h a n p t u x h t o u ISDN

e p i t r è p e i t h n q r s h t w n

k l a s i k ¸ n g r a m m ¸ n g i a m e t d o s h k a j a r y h f i a k ¸ n s h m t w n , t a o p o Ð a

p l e o n e k t o Ô n s h m a n t i k s e s q è s h m e t a a n a l o g i k ( P w c ? ' A s k h s h g i a

t o n a n a g n ¸ s t h ) .

M e t h n b o j e i a t o u ISDN

, t o t h l e p i k o i n w n i a k ì d Ð k t u o g Ð n e t a i a n e x r t h -

t o a p ì t o e Ð d o c t h c p l h r o f o r Ð a c p o u d i a k i n e Ð t a i , a f o Ô m è s a a p ì a u t ì ( k a i m e

k a j a r y h f i a k m o r f ) , m p o r e Ð p l è o n n a d i a k i n h j o Ô n d e d o m è n a u p o l o g i s t ¸ n ,

f w n , video. A n t Ð s t o i q a , t u p o p o i e Ð t a i k a i t o e Ð d o c t h c d i a s Ô n d e s h c d i f o -

r w n s u s k e u ¸ n ( a p ì d i f o r o u c k a t a s k e u a s t è c ) s t o d Ð k t u o , k a i d e n q r e i z e t a i

e i d i k ì c ( Ð s w c a k r i b ì c ) e x o p l i s m ì c g i a t h n p r o s a r m o g t o u c .

T a b a s i k s t o i q e Ð a p o u q a r a k t h r Ð z o u n t o ISDN

e Ð n a i :

• Y h f i a k M e t d o s h : ' O l a t a d e d o m è n a s t o d Ð k t u o ISDN

k i n o Ô n t a i s e

y h f i a k m o r f . A k ì m a k a i h f w n ( t h l e f w n i k s u n d i l e x h ) y h f i o p o i e Ð -

t a i p r i n s t a l e Ð s t h g r a m m .

• H s h m a t o d o s Ð a g Ð n e t a i m è s w i d i a Ð t e r o u k a n a l i o Ô ( common channel si-

gnaling) . H s h m a t o d o s Ð a p e r i l a m b n e i t a b o h j h t i k s m a t a m e t a o p o Ð a

g Ð n e t a i h d i a q e Ð r i s h m i a c e p i k o i n w n Ð a c ( p . q . t o k o u d o Ô n i s m a s e m i a t h l e -

f w n i k k l s h , h d i a d i k a s Ð a è n a r x h c k a i l x h c m i a c s Ô n d e s h c k . l . p . )

• O e n i a Ð o c t r ì p o c m e t o n o p o Ð o s u n d è o n t a i s u s k e u è c k a i q r s t e c s t o

d Ð k t u o : O i u p h r e s Ð e c t o u d i k t Ô o u e Ð n a i ì l e c d i a j è s i m e c m è s w e n ì c k a i

m ì n o t Ô p o u s Ô n d e s h c ( a p ì t h n Ð d i a a p ì l h x h ( p r Ð z a } .

T o d Ð k t u o d i a j è t e i d Ô o t r ì p o u c p r ì s b a s h c , t h n d i e p a f b a s i k o Ô r u j m o Ô

k a i t h n d i e p a f p r w t e Ô o n t o c r u j m o Ô .

H d i e p a f b a s i k o Ô r u j m o Ô Basic Rate Interface, BRI

p a r è q e i d Ô o k a n l i a

m e t d o s h c d e d o m è n w n ( 2 k a n l i a - B ) k a i è n a k a n l i s h m a t o d o s Ð a c ( 1 k a n l i - D

) .



1 2 D Ð k t u a E u r e Ð a c P e r i o q c

K j e k a n l i B e p i t u g q n e i r u j m ì m e t d o s h c 6 4 KBps

k a i m e t a f è r e i y h f i a k

d e d o m è n a . H f w n ( t h l e f w n i k k l s h ) m e t a f è r e t a i a f o Ô p r ¸ t a y h f i o p o i h j e Ð

m e r u j m ì d e i g m a t o l h y Ð a c 8 0 0 0 HZ

k a i d e Ð g m a t a 8 bit

. T o k a n l i D

è q e i r u j m ì

m e t d o s h c 1 6 KBps

k a i q r h s i m o p o Ð e i t a i g i a t i c b o h j h t i k è c l e i t o u r g Ð e c ( è n a r x h

/ l x h s Ô n d e s h c ) . O i q r s t e c è q o u n t h d u n a t ì t h t a n a q r h s i m o p o i o Ô n t o è n a

k a i t a d Ô o k a n l i a B t a u t ì q r o n a . A u t ì s h m a Ð n e i ì t i m p o r o Ô n n a q r h s i m o -

p o i o Ô n t o è n a k a n l i g i a m e t d o s h d e d o m è n w n k a i t o l l o g i a f w n , k a i t a

d Ô o g i a d e d o m è n a , t è l o c k a i t a d Ô o g i a f w n . M e t o ISDN

e Ð n a i d u n a t ì n

n a è q o u m e t a u t ì q r o n a d Ô o t h l e f w n i k è c s u n d i a l è x e i c m è s w t h c Ð d i a c g r a m m c .

A n s u n d u s o u m e k a i t a d Ô o k a n l i a g i a m e t d o s h d e d o m è n w n , e p i t u g q n o u m e

s u n o l i k ì r u j m ì m e t d o s h c 1 2 8 KBps

. M a z Ð m e t o k a n l i D

( t o o p o Ð o w s t ì -

s o d e n m e t a f è r e i q r s i m a d e d o m è n a q r s t h ) o r u j m ì c m e t d o s h c f t n e i t a

1 4 4 KBps.

S q m a 6 . 3 : D i e p a f è c b a s i k o Ô k a i p r w t e Ô o n t o c r u j m o Ô s t o ISDN



M è r o c II

P a r a r t m a t a



P a r r t h m a A þ

GNU Free Documentation

License



16 GNU Free Documentation License

GNU Free Documentation Li-

cense

Version 1.2, November 2002Copyright c2000,2001,2002 Free Software

Foundation, Inc.

51 Franklin St, Fifth Floor, Boston, MA02110-1301 USA

Everyone is permitted to copy anddistribute verbatim copies of this license

document, but changing it is not allowed.

Preamble

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This License is a kind of ”copyleft”,

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19

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leased under this License, and replace theindividual copies of this License in the vari-ous documents with a single copy that is in-cluded in the collection, provided that youfollow the rules of this License for verbatimcopying of each of the documents in all otherrespects.

You may extract a single documentfrom such a collection, and distribute it in-dividually under this License, provided youinsert a copy of this License into the ex-tracted document, and follow this License in




all other respects regarding verbatim copy-

ing of that document.

7. AGGREGATION WITHINDEPENDENT WORKS

A compilation of the Document or itsderivatives with other separate and inde-pendent documents or works, in or on a vol-ume of a storage or distribution medium, iscalled an ”aggregate” if the copyright re-sulting from the compilation is not used tolimit the legal rights of the compilation’susers beyond what the individual works per-mit. When the Document is included in an

aggregate, this License does not apply tothe other works in the aggregate which arenot themselves derivative works of the Doc-ument.

If the Cover Text requirement of section3 is applicable to these copies of the Docu-ment, then if the Document is less than onehalf of the entire aggregate, the Document’sCover Texts may be placed on covers thatbracket the Document within the aggregate,or the electronic equivalent of covers if theDocument is in electronic form. Otherwisethey must appear on printed covers that

bracket the whole aggregate.

8. TRANSLATION

Translation is considered a kind of mod-ification, so you may distribute transla-tions of the Document under the termsof section 4. Replacing Invariant Sectionswith translations requires special permis-sion from their copyright holders, but youmay include translations of some or all In-variant Sections in addition to the originalversions of these Invariant Sections. Youmay include a translation of this License,

and all the license notices in the Docu-ment, and any Warranty Disclaimers, pro-vided that you also include the original En-glish version of this License and the originalversions of those notices and disclaimers. Incase of a disagreement between the transla-tion and the original version of this Licenseor a notice or disclaimer, the original ver-sion will prevail.

If a section in the Document is En-titled ”Acknowledgements”, ”Dedications”,or ”History”, the requirement (section 4) to

Preserve its Title (section 1) will typically

require changing the actual title.

9. TERMINATION

You may not copy, modify, sublicense,or distribute the Document except as ex-pressly provided for under this License. Anyother attempt to copy, modify, sublicense ordistribute the Document is void, and willautomatically terminate your rights underthis License. However, parties who have re-ceived copies, or rights, from you under thisLicense will not have their licenses termi-nated so long as such parties remain in full

compliance.

10. FUTURE REVISIONS OFTHIS LICENSE

The Free Software Foundation maypublish new, revised versions of the GNUFree Documentation License from time totime. Such new versions will be similar inspirit to the present version, but may differin detail to address new problems or con-cerns. See http://www.gnu.org/copyleft/.

Each version of the License is given adistinguishing version number. If the Doc-

ument specifies that a particular numberedversion of this License ”or any later version”applies to it, you have the option of follow-ing the terms and conditions either of thatspecified version or of any later version thathas been published (not as a draft) by theFree Software Foundation. If the Documentdoes not specify a version number of thisLicense, you may choose any version everpublished (not as a draft) by the Free Soft-ware Foundation.

ADDENDUM: How to use thisLicense for your documents

To use this License in a document youhave written, include a copy of the Licensein the document and put the following copy-right and license notices just after the titlepage:

Copyright cYEAR YOURNAME. Permission is grantedto copy, distribute and/ormodify this document underthe terms of the GNU Free



2 1

Documentation License, Ver-

sion 1.2 or any later versionpublished by the Free Soft-ware Foundation; with no In-variant Sections, no Front-Cover Texts, and no Back-Cover Texts. A copy of thelicense is included in the sec-tion entitled ”GNU Free Doc-umentation License”.

If you have Invariant Sections, Front-Cover Texts and Back-Cover Texts, replacethe ”with...Texts.” line with this:

with the Invariant Sectionsbeing LIST THEIR TITLES,

with the Front-Cover Texts

being LIST, and with theBack-Cover Texts being LIST.

If you have Invariant Sections withoutCover Texts, or some other combination of the three, merge those two alternatives tosuit the situation.

If your document contains nontrivial

examples of program code, we recommend

releasing these examples in parallel under

your choice of free software license, such as

the GNU General Public License, to permit

their use in free software.

Δίκτυα 6_1-6_5 Ανεπίσημο Βοήθημα

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