! $# "
100VG-AnyLAN provides a 100-Mbit/s data rate with guaranteed
bandwidth and maximum access delay for time-critical applications such
as multimedia, using existing building wiring. It uses demand priority
protocol. Developed by Hewlett-Packard and now supported by over 30
companies ranging from integrated circuit vendors to systems suppliers,
demand priority is well on its way to becoming the IEEE 802.12 standard.
# $A2= -7 % 2); ,-+,A74))( %((-8-32 83 7
(:%2')!8%'/ 03'%0 %6)% 2)8;36/ 463(9'8 +6394 8 -7
%2 )'3231-'%00= )**)'8-:) 94+6%() 4%8, *36 '32+)78)(
A&-87 %7)A" 8,)62)8 %2( A&-87 83/)2 6-2+ 2)8A
;36/7 8 463:-()7 % A&-87 (%8% 6%8) ;-8, +9%6%28))(
&%2(;-(8, %2( &392()( %'')77 ()0%= *36 8-1)A'6-8-'%0 %440-A
'%8-327 97-2+ )<-78-2+ &9-0(-2+ ;-6-2+ ",-7 463:-()7 ,-+,
4)6*361%2') *36 86%(-8-32%0 (%8% 86%27*)6 %440-'%8-327 8 %073
463:-()7 )1)6+-2+ 1908-1)(-% %440-'%8-327 79', %7 -28)6%'A
8-:) :-()3 ;-8, 8,) 03; ()0%=7 8,)= 6)59-6) 8 ()0-:)67 8,-7
4)6*361%2') 3:)6 8,) 1378 '31132 2)8;36/-2+ 1)(-91
A4%-6 927,-)0()( 8;-78)(A4%-6 #" 8)0)4,32) ;-6)
$A2= 97)7 8,) ()1%2( 46-36-8= 46383'30 ;,-',
;%7 ():)034)( %7 % .3-28 )**368 &= );0)88A%'/%6( %&36%83A
6-)7 -2 6-7830 2+0%2( %2( 8,) 37):-00) )8;36/7 -:-A
7-32 -2 %0-*362-% 3; 7944368)( &= 3:)6 '314%2-)7
6%2+-2+ *631 -28)+6%8)( '-6'9-8 :)2(367 83 7=78)17 79440-)67
()1%2( 46-36-8= -7 ;)00 32 -87 ;%= 83 &)'31-2+ 8,) 78%2(%6(
",) $A2= %68-'0)7 -2 8,-7 -779) 033/ %8 8,) ():)034A
1)28 3* 8,) ()1%2( 46-36-8= 46383'30 %2( 8,) $A2=A
463(9'8 7)8
" #
)*36) 8,) -2-8-%0 ():)0341)28 3* 03'%0 %6)% 2)8;36/-2+ -2
8,) 0%8) 7 8,) 8)0)4,32) 7=78)1 ;%7 8,) 320= +)2)6%00=
%:%-0%&0) (%8% '31192-'%8-327 348-32 %2(;-(8, /> 32
% :3-')A+6%() 0-2) ;%7 '0)%60= % 463&0)1 %2( % 291&)6 3*
(-**)6)28 8=4)7 3* 2); (%8% 2)8;36/7 ;)6) 463437)( ";3
8,)62)8
%2( 83/)2 6-2+ ,%:) )1)6+)( 83 (31-2%8) 8,)
03'%0 %6)% 2)8;36/-2+ 1%6/)8
Ethernet (IEEE 802.3). 8,)62)8 ;%7 ():)034)( -2 8,) 0%8)
7 %7 % A&-87 %27;)6 83 8,) 0-1-8%8-327 3* 8,) 8)0)A
4,32) 7=78)1 8 &)'%1) %2 78%2(%6( -2 00
23()7 ;)6) '322)'8)( 83 % 7-2+0) ')286%0 '3%< &97 ;,-',
463:)( 83 &) 731);,%8 -2*0)<-&0) %7 97)67 ',%2+) 03'%8-327
36 %6) %(()( 83 8,) 2)8;36/
9+978 );0)88A%'/%6( 3962%0
",) 8,)62)8 %'')77 430-'= -7 ! ;,-', 78%2(7 *36
'%66-)6 7)27) 1908-40) %'')77 ;-8, '300-7-32 ()8)'8-32 8
%003;7 %2= 23() 83 86%271-8 % 4%'/)8 ;-8, 94 83 &=8)7
3* (%8% %2=8-1) -8 ()8)'87 7-0)2') 23 7-+2%0 32 8,) 2)8A
;36/ ",-7 '%2 0)%( 83 4%'/)8 '300-7-327 -* 8;3 36 136)
23()7 2))( 83 86%271-8 %2( ()8)'8 7-0)2') %8 8,) 7%1) 8-1)
%', -2:30:)( 23() -7 6)59-6)( 83 &%'/ 3** ')%7) 86%271-8A
8-2+ -11)(-%8)0= %*8)6 % '300-7-32 -7 ()8)'8)( &98 8-1) -7
'32791)( %2( 8,) %:%-0%&0) &%2(;-(8, -7 )**)'8-:)0= 6)(9')(
(96-2+ ,-+,A86%**-' 4)6-3(7
",) 46383'30 %073 6)59-6)7 )%', 23() 83 132-836 8,) 2)8A
;36/ 86%**-' %2( 83 ()'3() *-08)6 8,) ()78-2%8-32 %((6)77 3*
)%', 4%'/)8 83 ()8)61-2) ;,)8,)6 -8 7,390( &) 6)')-:)( &=
8,) 23() %'/)87 ;-8, 8,) 23()7 -2(-:-(9%0 36 +6394 %(A
(6)77 %6) '34-)( -283 1)136= %2( 4%'/)87 ;-8, 2321%8',A
-2+ %((6)77)7 %6) -+236)(
",) %7)A" 78%6 834303+= ;%7 463437)( &= );0)88A
%'/%6( -2 %2( &)'%1) 4%68 3* 8,) 78%2(%6( -2 ",) ')28)6 3* 8,) 78%6 -7 % 2)8;36/ '32')286%836 ,9& ;,-',
-7 8=4-'%00= 03'%8)( -2 % ;-6-2+ '037)8 %', 23() -7 '32A
2)'8)( 83 8,) ,9& &= :3-')A+6%() 8;-78)(A4%-6 '%&0)
%7)A" 6)8%-27 8,) &%7-' *)%896)7 %2( %'')77 430-'= 3* 8,)
&97 2)8;36/ %2( %073 %((7 % 0):)0 3* *%908 830)6%2') -2/
*%9087 %8 -2(-:-(9%0 23()7 %6) -730%8)( &= 8,) ,9& %2( (3 238
8%/) (3;2 8,) )28-6) 2)8;36/ %7)A" ,%7 &)'31) 8,)
1378 '31132 2)8;36/ '32*-+96%8-32
Token Ring (IEEE 802.5). "3/)2 6-2+ ;%7 463437)( %7 %
A&-87 73098-32 83 8,) 8,)62)8 '300-7-32 463&0)1 %2(
&)'%1) %2 78%2(%6( -2 0%8) ",) 36-+-2%0 2)8;36/
7869'896) -7 % 6-2+ %6392( ;,-', &38, 83/)27 %2( -2*361%8-32
4%'/)87 94 83 (%8% &=8)7 %6) 4%77)( ",) 2)8;36/
1)(-91 -7 8=4) 7,-)0()( 8;-78)(A4%-6 !" '%&0)
"3/)2 6-2+ 2)8;36/7 %6) %073 23; '311320= -278%00)( -2
78%6 '32*-+96%8-327
",)@83/)2 6-2+ %'')77 430-'= -7 ()7-+2)( 83 &) &38, '300-7-32A
*6)) %2( 46-36-8=A&%7)( 8 46):)287 %2= 23() 8,%8 (3)7 238
'966)280= ?3;2 8,) 83/)2 *631 86%271-88-2+ % (%8% 4%'/)8
%2( -8 463:-()7 )-+,8 46-36-8= 0):)07 83 %003; 731) '0%77)7 3*
(%8% 83 8%/) 46)')()2') 3:)6 38,)6 '0%77)7
00 (%8% 4%'/)87 %2( 83/)27 '328%-2 %2 %'')77 '328630 *-)0(
8,%8 %003;7 8,) 79'')77-:) 23()7 32 8,) 2)8;36/ &38, 83
6)7)6:) 8,) 83/)2 %2( 83 -2(-'%8) 8,)-6 6)7)6:%8-32 46-36-8=
0):)0 #,) 23() 8,%8 '966)280= 3;27 8,) 83/)2 86%271-87 -87
(%8% 4%'/)8 ;-8, 8,) 6)7)6:%8-32 &-87 -2 8,) %'')77 '328630
*-)0( 7)8 83 1-2-191 46-36-8= %', 79'')77-:) 23() *36;%6(7
8,) 4%'/)8 %7 -8 -7 &)-2+ 6)')-:)( 8 %073 -28)663+%8)7 8,)
()78-2%8-32 %((6)77 *-)0( 83 ()8)61-2) ;,)8,)6 -8 7,390(
'34= 8,) (%8% *6%1) %2( 8,) %'')77 '328630 *-)0( 83 ()8)6?
1-2) 8,) '966)28 6)7)6:%8-32 0):)0 * 8,) 23() 2))(7 83 7)2(
% (%8% 4%'/)8 %2( 8,) 6)7)6:)( 46-36-8= 0):)0 -7 0)77 8,%2 8,)
23()7 0):)0 8,) 23() -2(-'%8)7 -87 2))( &= ',%2+-2+ 8,)
:%09) 3* 8,) 6)7)6:%8-32 &-87 -2 8,) *36;%6()( 4%'/)8
#,) 7)2(-2+ 23() 6)13:)7 8,) 4%'/)8 *631 8,) 2)8;36/ %2(
86%271-87 % 2); 83/)2 ;-8, 8,) 46-36-8= &-87 3* 8,) %'')77
'328630 *-)0( 7)8 83 8,) 46-36-8= 0):)0 -2(-'%8)( -2 8,) 6)8962)(
4%'/)8 #,) 83/)2 8,)2 '-6'90%8)7 83 8,) 23() 8,%8 *-678 6)?
7)6:)( 8,%8 46-36-8= #,%8 23() 6)13:)7 8,) 83/)2 %2( 86%27?
1-87 % (%8% 4%'/)8 #,) 83/)2 '-6'90%8)7 '328-293970= %8
1-2-191 46-36-8= -2 %2 -(0) 2)8;36/
Category 4: 20-MHz bandwidth, used in 4-pair groups for each link.
28)62%8-32%0 %8% 36436%8-32 % 1%6/)8 6)7)%6', *-61
6)43687 8,%8 8,) ;360(;-() -278%00)( 8,)62)8 &%7) %8 8,) )2(
3* ;%7 23()7 94 *631 #,)=
46)(-'8 %2 -278%00)( &%7) 3* 3:)6 &= 8,) )2( 3*
46)(31-2%280= %7)?#
#,) 83/)2 6-2+ ;360(;-() -278%00)( &%7) ;%7 %8
8,) )2( 3* 94 *631 46)(-'87 8,%8 8,)
83/)2 6-2+ -278%00)( &%7) ;-00 %4463%', &= 8,)
)2( 3* Cables can be categorized in various ways: according to their physical structure,
the material used for transmitting signals, and the uses for which they are suitable.
Common types are listed below.
UTP: Unshielded twisted-pair, 100-ohm balanced cable. The lack of shielding
makes UTP cable very low-cost, but introduces problems of cross talk when the
pairs are in close proximity.
Category 3: Voice-grade cable, such as telephone wire, with 16-MHz bandwidth,
used in 4-pair groups for each link. 25-pair bundles of Category 3 UTP are common in existing LANs. This is an important consideration when designing a network protocol.
Category 5: Data-grade cable with 100-MHz bandwidth, used in 2-pair or 4-pair
groups for each link.
Optical-Fiber: Cable consisting of a minimum of two strands of optical fiber running parallel within a protective jacket. Each fiber is usually composed of glass
125 m in diameter, and has a 62.5-m core. Transmission is by light beam at
850-nm or 1330-nm wavelength.
STP: 150-ohm balanced shielded twisted-pair cable. Usually used in 2-pair groups
for each link.
#,) 7-89%8-32 ;-00 6%4-(0= ;367)2 ;-8, 8,) %'')0)6%8)( ():)0?
341)28 3* 8-1)?7)27-8-:) 1908-1)(-% %440-'%8-327 !)%0?8-1)
%9(-3 %2( :-()3 *36 :-()3 '32*)6)2'-2+ %2( -28)6%'8-:)
:-()3 6)59-6) 8,%8 4%'/)87 3* (%8% &) 86%27*)66)( '328-29?
3970= ;-8, 1-2-1%0 ()0%= #,)= '%2238 %**36( 83 ,%:) %2=
4%'/)8 ()0%=)( 36 (6344)( &)'%97) 3* % '300-7-32 36 '32+)7?
8-32 32 8,) 2)8;36/
#,) 0%78 8)2 =)%67 ,%7 7))2 % ,92(6)(*30( -2'6)%7) -2 8,)
#,) 463&0)1 46)7)28)( 83 7 2)8;36/ ()7-+2 8)%1 '32?
74))( 3* '31498)67 %2( 8,) 7->) 3* *-0)7 '6)%8)( &= 734,-78-?
8%-2)( 7):)6%0 1%.36 +3%07 %2( '327-()6%8-327
'%8)( %440-'%8-327 )%2;,-0) 8,) (%8% 86%27*)6 6%8) 3* 1378 • "4))( #,) '966)28 2)8;36/7 %6) '0)%60= 833 703; 1%.36
2)8;36/7 ,%7 6)1%-2)( '3278%28 %8 &-877 83 &-877
-1463:)1)28 ;390( &) 83 -2'6)%7) 8,) 74))( 3* 8,) 2)8?
;36/ &-877 ;390( %003; 8)2 8-1)7 8,) %13928 3*
#,) *-678 7-+27 3* 2)8;36/ 786%-2 %6) 97)67 '3140%-2-2+ 8,%8
86%**-'
4)6*361%2') -7 *%00-2+ 3** %2( 6)74327) 8-1)7 %6) 6-7-2+ #,)
•
9%6%28))( '')77 $,-0) 1908-1)(-% %2( 38,)6 8-1)?7)27-?
'%97) -7 %01378 %0;%=7 '32+)78-32@833 1%2= 97)67 833
8-:) %440-'%8-327 6)59-6) 8,) -2'6)%7)( 838%0 &%2(;-(8, 8,%8
19', -2*361%8-32 )8;36/?'322)'8)( ,-+,?4)6*361%2')
&-877 ;390( 463:-() 8,)= %073 2))( +9%6%28))7 8,%8
()7/834 7=78)17 %6) -28)2()( 83 +-:) 97)67 -278%28 %'')77 83
-2*361%8-32 ;-00 +)8 8,639+, ;-8,-2 % 78%8)( ()0%= ;-2(3;
%2= %446346-%8) -2*361%8-32 %2=;,)6) -2 8,) 36+%2->%8-32
;,%8):)6 8,) 86%**-' 32 8,) 2)8;36/
%8 %2= 8-1) %2( 8,-7 +)2)6%8)7 ,-+, 0):)07 3* 86%**-'
• 378 <-78-2+ 2)8;36/7 ,%:) %06)%(= 6)59-6)( 1%.36 -2:)78?
"31)8-1)7 2)8;36/ &3880)2)'/7 %6-7) *631 -2(-:-(9%0 %440-?
1)287 -2 8,) ;-6-2+ 7869'896) #,) 2); 2)8;36/ 7,390( &)
'%8-327 )<'))(-2+ 8,) &%2(;-(8, 3* 8,) 2)8;36/ %8%?-28)2? %&0) 83 34)6%8) 3:)6 +)2)6-' 8;-78)(?4%-6 &9-0(-2+ ;-6-2+
7-:) %440-'%8-327 79', %7 (%8%&%7) %'')77 -1%+) %2%0=7-7
-&)6?348-' '%&0-2+ 7,390( %073 &) %003;)(
()7/834 49&0-7,-2+ 2)8;36/ 46-28-2+ %2( 6)59-6) 8,%8 • #34303+= #3 &) '314%8-&0) ;-8, )<-78-2+ ;-6-2+ 8,) 2);
:)6= 0%6+) %139287 3* -2*361%8-32 &) 86%27*)66)( -2 % 7-2+0)
2)8;36/ 1978 97) % 78%6 834303+= #,) %003;)( 2)8;36/
&9678 36 )<%140) % ()7/834 49&0-7,-2+ %440-'%8-32 1-+,8
(-%1)8)6 7,390( &) %8 0)%78 /1 ;-8, 8,6)) 36 136) 0):)07
6)59-6) 1)+%&=8)7 *36 % 7-2+0) 4%+) -2'36436%8-2+ 7):)6%0
3* ,9& '%7'%(-2+
8=4)*%')7 % &-81%44)( 03+3 %2( *396?'3036 +6%4,-'7 2 % • "3*8;%6) 314%8-&-0-8= #,) 2)8;36/ 7,390( &) '314%8-&0)
8=4-'%0 8,)62)8 36 83/)2 6-2+ 2)8;36/ -8 '390( 8%/) %7 032+
;-8, &38, 8,)62)8 %2( 83/)2 6-2+ *6%1) *361%87 %2( 7,390(
%7 7)'32(7 83 6)86-):) 8,%8 32) 4%+) 1908-4%+) (3'9?
46)7)6:) )<-78-2+ -2:)781)287 -2 2)8;36/ %2( %440-'%8-327
1)28 '390( 8%/) % 1-298) 36 8;3 83 6)86-):)
73*8;%6)
9+978 );0)88? %'/%6( 3962%0
Level-1 (Root) Hub
Cascade Port
Local Ports
Node
Level-2
Hub
Level-3
Hub
Level-2
Hub
Level-3
Hub
,*;,*-.- ;<*: 6.<?7:3
• ::7: %=;,.8<2+242<A *6- .<.,<276 &1. 2584.5.6<*<276
;17=4- 1*>. * 81A;2,*4 4*A.: +2< .::7: :*<. 7/ 4.;; <1*6
*6- * ,7-260 ;,1.5. <1*< ?244 0=*:*6<.. -.<.,<276 7/
.::7:; 26 *6A <1:.. +2<; ?2<126 <1. -*<* /:*5. ?2<17=< ,75C
8:752;260 <1. ,A,42, :.-=6-*6,A ,1.,3 $ -./26.- /7:
<1. *6- /:*5. /7:5*<;
• #:2>*,A 7<1 <1.:6.< *6- <73.6 :260 8:7>2-. *--:.;; /24<.:C
260 *< <1. 67-. 4.>.4 .//.,<2>.4A *447?260 *6A 67-. <7 ,78A
*6A -*<* 8*,3.< ;.6< 76 <1. 6.<?7:3 &7 .61*6,. <1. 8:2C
>*,A 7/ -*<* ,755=62,*<276; *--:.;; /24<.:260 7/ 26-2>2-=C
*44A *--:.;;.- 8*,3.<; ;17=4- +. 8:7>2-.- *; *6 78<276
?2<126 <1. 1=+
• $7+=;< "8.:*<276 76<26=7=; 78.:*<276 7/ <1. 6.<?7:3 2;
:.9=2:.- #1A;2,*4 ,766.,<276; ;17=4- +. <.;<.- +./7:. *4C
47?260 67-.; <7 .6<.: <1. 6.<?7:3 *6- 8:7>2;276 ;17=4- +.
5*-. <7 *447? <1. 2-.6<2/2,*<276 *6- :.57>*4 7/ -2;:=8<2>.
67-.;
• !.<?7:3 *6*0.5.6< 6 78<276*4 6.<?7:3 5*6*0.5.6<
,*8*+242<A ;17=4- +. 8:7>2-.- <7 5762<7: 6.<?7:3 8.:/7:C
5*6,. 2;74*<. /*=4<; *6- ,76<:74 6.<?7:3 ,76/20=:*<276
! "!
&1. 8:7<7,74 /7: <1. 6.? 6.<?7:3 2; -.5*6- 8:27:2<A <
,75+26.; <1. +.;< ,1*:*,<.:2;<2,; 7/ +7<1 <1.:6.< ;2584.
/*;< *,,.;; *6- <73.6 :260 ;<:760 ,76<:74 ,7442;276 *>72-C
*6,. *6- -.<.:5262;<2, -.4*A
&1. # 8:7-=,< 2; (C6A! < 2; +*;.- 76 ,128 <.,1C
67470A -.>.478.- +A # *6- && <1*< -.42>.:; *6 .//.,<2>.
-*<* :*<. 7/ +2<;
; 7>.: ;.>.:*4 -2//.:.6< 4263 ,76/20=:*C
<276; C8*2: *<.07:A =6;12.4-.- <?2;<.-C8*2: '&# ,*+4.
C8*2: ;12.4-.- <?2;<.-C8*2: %&# ,*+4. 7: C8*2: /2+.:C78<2,
,*+4. '&# %&# *6- /2+.:C78<2, ,*+4. ,*6 +. 26<.:52@.- 76
<1. ;*5. 6.<?7:3 (C6A! ,*6 *4;7 78.:*<. ?2<1 <1.
C8*2: +=6-4.- ,*+4. <1*< 2; =;.- 26 5*6A *;.C& 6.<C
?7:3; *; 4760 *; 1=+; *:. 67< ,766.,<.- <1:7=01 +=6-4.,*+4.
!
&1. +*;2, <787470A =;.- +A (C6A! 6.<?7:3; 2; <1.
;<*: ,76/20=:*<276 *,1 1=+ 1*; <?7 7: 57:. 47,*4 87:<; *6,*6 78<276*44A 1*>. 76. ,*;,*-. 87:< /7: ,766.,<276 <7 *
1201.:C4.>.4 1=+ !7-.; ,*6 +. =;.: ;<*<276; +:2-0.; <7
7<1.: 6.<?7:3; ! *6*4AB.:; 7: 47?.:C4.>.4 1=+;
=0=;< .?4.<<C#*,3*:- 7=:6*4
6.<?7:3 ,*6 ,76<*26 ;.>.:*4 4.>.4; 7/ 1=+; 26<.:,766.,<.26 * ,*;,*-. *; ;17?6 26 20 &1. <7857;< 1=+ 2; -.;20C
6*<.- *; <1. 4.>.4 :77< 1=+ =+; 26 47?.: 4.>.4; 7/ <1.
,*;,*-. *:. -.;206*<.- +A <1. 6=5+.: 7/ 4263; +.<?..6
<1.5 *6- <1. :77< 1=+ &1. 4.>.4 6=5+.: 7/ *6A 8*:<2,=4*:
1=+ ,*6 +. -.<.:526.- +A <1. .9=*<276
=+ .>.4 6=5+.: 7/ 4263 ;.05.6<; *?*A /:75 <1.
:77< 1=+
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&1. 5*@25=5 6=5+.: 7/ 67-.; <1*< ,*6 +. ,766.,<.- <7
<1. 6.<?7:3 2; -.8.6-.6< 76 <1. 4.>.4 *6- /:.9=.6,A 7/
<:*//2, .*,1 67-. 0.6.:*<.; &1. 5*@25=5 <787470A -2*5.C
<.:; *6- <1. 6=5+.: 7/ 4.>.4; 7/ ,*;,*-260 *:. 4252<.- +A <1.
*447?*+4. -.4*A +.<?..6 <1. 67-. *6- <1. :77< 1=+ *6,*6 +. ,*4,=4*<.- /7: *6A 8:787;.- ,76/20=:*<276 )1.6
<1.:. 2; 764A 76. 26<.:5.-2*<. 1=+ +.<?..6 <1. :77< 1=+
*6- <1. 67-. /7: .@*584. <1. 5*@25=5 -2;<*6,. +.<?..6
* 67-. *6- <1. :77< 1=+ 2; 35 *,1 *--2<276*4 26<.:5.-2C
*<. 1=+ :.-=,.; <1. 1=+C<7C67-. -2;<*6,. +A 35 :.;=4<C
260 26 * 5*@25=5 7/ /7=: 26<.:5.-2*<. 1=+; *6- * :77<C1=+C
<7C67-. -2;<*6,. 7/ 35
7,*4 1=+C<7C67-. -2;<*6,.; -.8.6- 76 <1. <A8. 7/ 5.-2*
=;.- /7: <1. 4263 C8*2: '&# 4263; ,76/20=:.- ?2<1 *<.07:A
7: *<.07:A ,*+4. *6- 4263; ,76/20=:.- ?2<1 %&# ,*+4.
;17=4- 67< .@,..- 5 *<.07:AC 4263; ,*6 +. =8 <7 5 4760 2+.:C78<2, 4263; ,*6 +. .>.6 4760.: 5 ?2<1
C65 <:*6;,.2>.:; *6- 5 ?2<1 C65 <:*6;,.2>.:;
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ISO
Open Systems
Interconnection
Reference Model
Network Layers
Application
Presentation
Session
Transport
Network
Data Link
Physical
IEEE 802.12 Model
LLC End Node
Hub
LME
LLC
MAC
MAC
RMAC
PMI
PMI
PMI
PMI
PMI
MII
MII
MII
MII
MII
MII
PMD
PMD
PMD
PMD
PMD
PMD
MDI
MDI
MDI
MDI
Cascade Port
Local Ports
PMI
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FDDI. Fiber Distributed Data Interface (FDDI) networks run at a standard
100-Mbit/s transfer rate using multimode optical-fiber cabling. The purchase cost is
high, partly because it necessitates new cabling for existing networks. FDDI is also
available as a high-speed backbone network connecting LANs.
A twisted-pair version, TP-PMD (twisted-pair physical medium dependent) FDDI,
is under development, using Category 5 UTP and STP copper cables. This version is sometimes called Copper Distributed Data Interface (CDDI).
ATM. Asynchronous transfer mode (ATM) is a new network technology particularly
suitable for wide area networks and campus backbones. It is intended to allow
seamless integration of campus LAN backbones into the wide area network.
Ethernet and Token Ring Switching. Switching is also being introduced
into Ethernet and token ring networks. To increase overall throughput, LANs are
segmented. Hubs switch packets dynamically between connected segments
allowing simultaneous transmissions among pairs of network segments. This
increases bandwidth by two or more times that of individual segments.
100Base-T. 100Base-T is a scaling of CSMA/CD to 100 Mbits/s. There is no
migration path or accommodation for existing token ring users. The technique
cannot emulate 10Base-T topologies since the maximum topology is two repeaters.
Table II
System Comparisons
ATM uses cell switching (53 bytes per cell) similar to high-speed telephone switching over existing UTP or optical-fiber cabling. It runs at 25 to 622 Mbits/s.
FDDI
ATM
100Base-T
Demand
Priority
Yes
Yes
No
Yes
Node management is
expensive
Segmentation or reassembly
of frames
is expensive
Low
Low
Ethernet 802.3 networks can be upgraded without software changes?
No
No
Yes
Yes
Token ring 802.5 networks can be upgraded without software changes?
No
No
No
Yes
Supports multimedia
with guaranteed
delay and bandwidth?
Table I
Cabling and Topological Comparisons
FDDI
ATM
100Base-T
Demand
Priority
100-Mbit/s Category
3 cable supported?
No
50 Mbits/s
with complex coding
Yes
Yes
Bundled cables
supported?
No
No
No
Yes
Multiple cascades
supported without
bridging or routing?
Yes
Yes
No
Yes
Cost
High
High
Medium
Low
End-node adapter
card complexity
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Bridge
Adapter
10Base-T Hub
10Base-T Hub
100VG-AnyLAN
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Information TechnologyĊLocal and Metropolitan Area NetĆ
worksĊPart 3: Carrier Sense Multiple Access with Collision Detection
(CSMA/CD) Access Method and Physical Specifications ?
Information TechnologyĊTelecommunications and Information
Exchange between SystemsĊLocal and Metropolitan Area NetĆ
worksĊLAN/MAN Specific RequirementsĊPart 5: Token Ring Access
Method and Physical Layer Specifications ?
Local Area NetworksĊAnalysis of the Intelligent Hub Market 28)6?
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