Technical data

Scenario Description
Dial Solutions Quick Configuration Guide
1-2
Figure 1-2 shows some of the physical elements present at layer 1 of the Open System
Interconnection (OSI) reference model. The public switched telephone network (PSTN) provides
the core interconnecting fabric between devices.
Figure 1-2 OSI Layer 1 Elements
In this scenario, a single Cisco AS5300 supports 96 concurrent modem and ISDN connections using
four T1 PRI lines and 96 integrated modems. Modem connections are established via the Cisco IOS
lines and corresponding asynchronous interfaces. Digital ISDN connections are established via the
Cisco IOS channelized serial interfaces.
Figure 1-3 shows the layer 2 and layer 3 elements. The links going across the PSTN use the
Point-to-Point Protocol (PPP). In this case study scenario PPP negotiates the link control protocol
(LCP), CHAP or PAP authentication, and IP Control Protocol (IPCP) to bring up IP over PPP.
IPCP is the network control protocol (NCP) used in this case study. IPCP is the mechanism that
opens the links and negotiates the IP parameters.
Headquarters
network
Cisco AS5300
point-of-presence
POTS
line
BRI
line
BRI
line
PSTN/ISDN
15986
Cisco 766
Cisco 1604
LAN
LAN
Modem
RS-232
Remote PC
Four T1 PRI lines