Foundation Summary 601
Figure 8-34
ISDN Function Groups and Reference Points
Table 8-44 lists the function groups and reference points shown in Figure 8-34.
Table 8-45 summarizes these types of permanent connections and lists some of the strengths
and weaknesses.
Table 8-44
Figure 8-34 Function Groups and Reference Point Summary
Router
Function Group(s)
Connected to Reference
Point(s)
A
TE1, NT1
U
B
TE1
S/T (combined S and T)
C
TE2
R
D
TE1
S
Table 8-45
Comparison of Leased Versus Packet Switching
Type of WAN
Service
Data Link
Protocols
Strengths and Weaknesses
Leased
Offers pervasive availability. Can be expensive for long
circuits. Is more expensive for providers to engineer than are
packet services.
PPP
Can improve speed of routing protocol convergence. Allows
multivendor interoperability. Offers error recovery option.
A
U
B
NT1
S/T
U
C
D
TA
NT1
R
S/T
U
NT2
NT1
S
T
U
Telco
continues
ch08.fm Page 601 Monday, March 20, 2000 5:17 PM