Cisco Cisco IOS Software Release 12.0(19)S

There are three primary leased line termination applications for the ISE line cards:

DS-3 lease-line termination

OC-3c lease-line termination

OC-12c leased-line termination

 shows four different DS-3 deployment scenarios that could be used with the ISE line 

cards. 

In scenario 1, SONET add drop multiplexer (ADM) passes through the OC-12 from the 12000 series 
router to the remote digital access and crossconnect system (DACS). The receiving DACS demultiplexes 
the OC-12 to 12 DS-3s, or the OC-12 into OC-3s. These 12 DS-3s or 4 OC-3s are then deployed directly 
to the remote sites. The remote DACS is responsible for directly terminating the remote DS3 or OC-3 
circuits.

In scenario 2, the SONET ADM directly terminates the OC-12 and demultiplexes the OC-12 to 12 DS-3. 
The DS-3 is then connected to a Frame Relay switch. The Frame Relay switch is used as an aggregation 
device responsible for mapping the edge data link connection identifiers (which are based on DS1 or DS0 
connections to the Frame Relay network), to the DS-3 connected to the SONET ADM. The ADM then 
maps the unchannelized DS-3 into a channelized OC-12/STM-4. The IP packets transverse the SONET 
ADM network within a channelized OC-12/STM-4. The ISE line cards strip off the SONET framing and 
route the IP packets to their destination.

In scenario 3, the role of the SONET ADM takes on a more active role and is no longer a pass-through 
device. The SONET ADM demultiplexes the optical interface and provides the DS-3 interface directly 
to the remote user.

In scenario 4, the channelized OC-12/STM-4 is used as a handoff to a long-distance carrier. This type of 
deployment is dependent upon the ability of the network provider to obtain channelized OC-12 
interfaces from the long-distance carrier.