Glossary
GL-4
Cisco CRS-1 Series Carrier Routing System Getting Started Guide
DPT
Dynamic Packet Transport. DPT rings are dual, counter-rotating fiber rings. Both fibers are used
concurrently to transport both data and control traffic.
DS-3
digital signal level 3. A 45 Mbps asynchronous communications format that supports 28 T1 lines. The
Cisco CRS-1 Series routing system queuing supports communications links down to DS-3.
dSC
designated shelf controller. The physical shelf controller that serves the entire Cisco CRS-1 Series
routing system as the designated master SC. The dSC is selected from among the Route Processors
(RPs) installed in the line card chassis.
dSCp
The designated shelf controller process running on the dSC node. The dSCp running on all the non-dSC
nodes is referred as the auxiliary designated shelf controller process or adSCp. See also adSCp.
DWDM
dense wavelength division multiplexing. Optical transmission of multiple signals over closely spaced
wavelengths in the 1550 nm region. (Wavelength spacings are usually 100 GHz or 200 GHz, which
corresponds to 0.8 nm or 1.6 nm.)
E
eBGP
external Border Gateway Protocol. BGP sessions are established between routers in different
autonomous systems. eBGPs communicate among different network domains.
ECC
error correction code. ECC is used to correct errors within memories on the Cisco CRS-1 Series routing
system.
EEPROM ID
Electrically erasable programmable read-only memory that contains board assembly and test history.
The backplane EEPROM ID is used to map a rack to a rack number. This rack number is then assigned
a dSC priority.
EGP
Exterior Gateway Protocol. Internet protocol for exchanging routing information between different
autonomous systems. EGP is an obsolete protocol that was replaced by BGP. See also BGP.
egress
Outgoing channel.
Ethernet
Baseband LAN specification invented by Xerox Corporation and developed jointly by Xerox, Intel, and
Digital Equipment Corporation. Ethernet networks use CSMA/CD and run over a variety of cable types at
10 Mbps. Ethernet standards are defined by the IEEE 802.3 specification.
F
fabric
Connectivity between all line cards. Also referred to as switch fabric.
failover
A backup operation that automatically switches to a standby database, server, or network if the primary
system fails or is temporarily shut down for servicing. Failover is an important fault tolerance function of
mission-critical systems that rely on constant accessibility. Failover automatically redirects requests from
the failed or down system to the backup system that mimics the operations of the primary system.
fan trays
A module carrying fans that can be inserted in a Line Card Chassis (LCC) or a Switch Fabric Chassis
(SFC). Two fan trays will go in every LCC or every SFC. Each type of chassis uses a different type of
fan tray.
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