Foundation Summary 177
Foundation Summary
The Foundation Summary is a collection of tables and figures that provides a convenient review
of many key concepts in this chapter. For those of you already comfortable with the topics in
this chapter, this summary can still help you recall a few details. For those of you who just read
this chapter, this review should help solidify some key facts. For any of you doing your final
preparation before the exam, these tables and figures are a convenient way to review the day
before the exam.
Table 6-6 summarizes the ISDN service offerings.
Table 6-7 summarizes ISDN protocols.
Table 6-6
ISDN Services
Service
B Channels
D Channel
Bandwidth
BRI
2 x 64 kbps
1 x 16 kbps
144 kbps
T1 PRI
23 x 64 kbps
1 x 64 kbps
1.544 Mbps
E1 PRI
30 x 64 kbps
1 x 64 kbps
2.048 Mbps
Table 6-7
ISDN Protocols
Layer
Protocol
Description
1
I.430/T1.601
This layer is the physical layer dealing with connectivity. I.430 specifies
framing between TE1 and NT1. T1.601 specifies framing between
TE and the LE.
2
Q.921
Q.921 institutes an addressing scheme for ISDN.
3
Q.931
Q.931 is used between the TE and the local ISDN switch. Call setup is
handled by Q.931 as well.