Understanding the network.pdf - Back to Home

encapsulation, framing, and line signaling protocols must be also be specified. Cisco,
as mentioned earlier, uses HDLC for the default framing protocol. Alternatively, PPP
(with or without authentication) can also be used. Serial interfaces are configured
using the global configuration command .
Framing and line signaling are only configured if the serial interface is an integrated
DSU/CSU. Otherwise, framing and signaling are configured on the external
DSU/CSU.
NOTE
On Cisco 4xxx and 7xxx routers, integrated DSU/CSU interfaces are called
. On 16xx, 25xx, and 36xx series routers, they are referred to as
.
Transport-1 supports two framing and signaling combinations: D4-ESF/B8ZS,
which is the default, and D4-SF/AMI. You must specify the type of framing and
signaling you want to use when you order your circuit from your RBOC or CLEC.
Signaling and framing are configured on integrated controllers using the interface
configuration subcommands and
. When using an integrated
controller, the number of timeslots or T1 channels must be specified. Channels are
a carryover from the early days of data communications. At one time, "channelized"
T1 service was easily available. With channelized or fractional T1 service, it's
possible to order a T1 and only pay for using part of the circuit. The service was sold
in 128K blocks. Today, most carriers only offer fractional data rate service using
Frame Relay. Point-to-point dedicated service is sold only as dedicated 56K (DS0),
T1, and T3. Channel specification is performed using the interface configuration
subcommand .
If the circuit is a dedicated 56Kbps, only one channel is specified; if a T1 is in use,
either or can be used. You might also be required to provide timing for
your circuit; if this is the case, only one side is configured as the clock source. To
configure the integrated controller to provide the network clock, use the interface
configuration subcommand . By default, the
controller expects the circuit to provide the clock. Here is an integrated DSU/CSU
control configuration example:
persephone(config)# interface serial0/0
persephone(config-if)#ip address 172.16.30.1 255.255.255.252
persephone(config-if)#no shutdown
persephone(config-if)#encapsulation ppp
persephone(config-if)#service-module t1 framing esf