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3GE-GBIC-SC Line Card Features Flexible and Expandable Packet Buffer Memory
Depending on the network topology, sufficient buffering must be available on Layer 3 line cards to satisfy queuing
requirements for the network at gigabit rates. The largest queuing requirement would be 120 MB of memory. The
Cisco 12000 series line cards implement the buffering memory with SDRAM modules, giving users the flexibility to
install the requirements for their applications and to upgrade their requirement when necessary. The Cisco 12000
series Gigabit Ethernet line cards provide 256-MB and 512-MB SDRAM options. Other features include:
• Multiple virtual output queues, eliminating head-of-line blocking
• ASICs-based queuing, providing line-rate queue performance
• Layer 3 QoS support, providing differentiated services
The packet memory option on the Cisco 12000 series Internet router three-port Gigabit Ethernet line cards will be
different from some existing line cards. The memory on the Gigabit Ethernet line card runs at 100 MHz, versus 50
MHz for some existing line cards. (See Table 3.)
Cisco 12000 Series Internet Router Gigabit Ethernet Line Cards Feature Flexible and
Expandable Routing Table Memory
These line cards support Cisco Express Forwarding (CEF). This technique implements a distributed architecture
within the platform whereby each line card can make its own decision in forwarding packets in the network. Away
from the data path, the route processor card maintains the routing tables and transports a full image of its routing
table to every line card.
As the number of networks that make up the Internet grows, the number of entries in the routing tables will grow as
well. The Cisco 12000 Gigabit Ethernet line cards implement an expandable routing table with the addition of
DRAM modules, which provide flexibility to the user. The expandable DRAM options range from 128 MB to 256
MB. The forwarding table can accommodate up to one million forwarding entries. (See Table 4.)
Switch Card Requirement
At minimum, full bandwidth fabric cards must be installed in your Cisco 12000 series Internet router (which is one
clock scheduler and three switch fabric cards).
Table 3 Packet Memory Options
Part Numbers Description
Default- 256 MB 128/128 Tx/Rx line-card buffer memory (4 x 64 MB)
MEM-PKT-512-UPG(=) Option upgrade 256/256 Tx/Rx line-card buffer memory (4 x 128 MB)
Table 4 Route Memory Options
Part Number Description
MEM-DFT-LC-2X64 128-MB line card program/route memory (2 x 64 MB)
MEM-GRP/LC-128 Option upgrade 128-MB GRP and line-card route memory (1 x 128 MB)
MEM-GRP/LC-256 Option upgrade 256-MB GRP and line-card program/route memory (2 x 128 MB)
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