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
! 4&-&$5"#-& "/% "%"15&34 "/% "3& "%"15&3 $"3%4 8*5)
0/& < $0//&$503 '03 <#*54 "4&< "/% "/05)&3 '03
<#*54 !</: )& "%"15&34 "650."5*$"--:
4&/4& 8)*$) /&5803, 5)&: "3& $0//&$5&% 50 "/% 4&-&$5 5)&
$033&$5 .0%& 0' 01&3"5*0/
!</: "3& "%"15&34
'03 &3*&4 803,45"5*0/4 )&: 4611035
$0//&$5*0/ 50 &*5)&3 <#*54 "4&< 03 <#*54
!</: )& "%"15&34 "650."5*$"--: 4&/4& 8)*$)
/&5803, 5)&: "3& $0//&$5&% 50 "/% 4&-&$5 5)& $033&$5 .0%&
0' 01&3"5*0/
!</: %&7&-01.&/5 4:45&. *4 "
%&7&-01.&/5 4:45&. '03 %&4*(/&34 "/% 01&3"5034 0' !<
/: /&5803, 130%6$54 5 '*/%4 5)& 3005 $"64& 0' "/:
%&4*(/ "/% */5&301&3"#*-*5: 130#-&.4
/ .045 $"4&4 /05 "-- 0' 5)& /&5803, 8*-- )"7& 50 #& 61<
(3"%&% "5 5)& 4".& 5*.& 0/4*%&3 '03 &9".1-& "/ &9*45*/(
"4&< /&5803, 8*5) " .*9 0' )*()<53"''*$ "/% -08<53"''*$
64&34 5)"5 "-- /&&% 50 "$$&44 '*-& 4&37&34 "/% 13*/5&34 )&
'*345 1)"4& *4 50 *%&/5*': 5)& )*()<53"''*$ 64&34 50 %&5&3.*/&
)08 ."/: /0%&4 /&&% 50 #& 61(3"%&% )*4 8*-- %&5&3.*/&
5)& /6.#&3 0' !</: )6# 10354 "/% /&5803,
"%"15&34 5)"5 8*-- #& 3&26*3&% */$-6%*/( /&5803, '*-& 4&37&34
"/% 13*/5&34
)& $633&/5 !</: 130%6$5 4&5 1307*%&4 " 4.005)
45&1<#:<45&1 8": '03 $6450.&34 8)0 8*4) 50 61(3"%& 5)&*3
&9*45*/( "4&< 5)&3/&5 /&5803,4 )& 0/-: 3&26*3&% &-&<
.&/54 "3& /&8 )6#4 '03 5)& /&5803, "/% /&8 "%"15&3 $"3%4
'03 &"$) /0%& 9*45*/( /&5803, ."/"(&.&/5 */5&3'"$&4
01&3"5*/( 4:45&.4 #3*%(&4 "/% 3065&34 $"/ 3&."*/
!</: )6#4 "3& */45"--&% "%+"$&/5 50 5)& &9*45*/(
"4&< )6#4 5)"5 4&37*$& )*()<53"''*$ 64&34 )& /&5803,
$"#-&4 50 &"$) 61(3"%&% /0%& "3& %*4$0//&$5&% '30. 5)&
"4&< ;)6#;"/% $0//&$5&% 50 " !</: )6# 40.&
3&"33"/(&.&/5 0' 5)& "4&< /0%&<50<)6# $0//&$5*0/4
6(645 &8-&55<"$,"3% 063/"-
)& 4&$0/% 1)"4& *4 50 "$26*3& 5)& /&$&44"3: !</:<
)6#4 "/% /&5803, "%"15&3 $"3%4 0/& )6# '03 &"$) /0%&4 *' %7"/$&5"$, !</: )6#4 "3& 64&%
"/% 50 */45"-- 5)&. */ 5)& /&5803, "4 %&1*$5&% */ *( )&
-*/, $"#-& *4 %*4$0//&$5&% '30. &"$) /0%& 5)"5 )"4 #&&/
*%&/5*'*&% '03 61(3"%*/( " 3&1-"$&.&/5 "%"15&3 $"3%
*4 */45"--&% "/% 5)& -*/, $"#-& *4 3&$0//&$5&%