21. ISDN:
The ISDN Primary Rate Interface
(PRI, also known as 23B+D1)
service delivers 23 B channels
and one 64KBPS D channel for a
total bit rate of up to 1.544
MBPS.
ISDN BRI will have 2B + 1D
channels, the total bandwidth is
64X2 +16 = 144 KBPS
22. The most important design
rule for 100MBPS Ethernet is
that the round trip collision
delay must not exceed 512 bit
times, which is same as that of
10BaseT. However, a bit time in
100BaseT is 10 times smaller.
Therefore, a bit time on a 100
MBPS Ethernet is 0.01
microseconds, compared to 0.1
microseconds on a 10 MBPS
Ethernet. Therefore, the maximum
round trip delay for a 100 MBPS
Ethernet is 5.12 microseconds
whereas that of 10BaseT is 51.2
microseconds.
