Chapter 14 Configuring The Switching Database Manager; Understanding The Sdm; Sdm Regions - Cisco ONS 15454 Software Feature And Configuration Manual

Configuring the Switching Database Manager
This chapter describes the switching database manager (SDM) features built into the ML100T-12 and
ML1000-2 cards. This section contains the following major sections:
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Understanding the SDM

ML-Series cards use the forwarding engine and ternary content-addressable memory (TCAM) to
implement high-speed forwarding. The high-speed forwarding information is maintained in TCAM. The
SDM is the software subsystem that manages the switching information maintained in TCAM.
SDM organizes the switching information in TCAM into application-specific regions and configures the
size of these application regions. SDM enables exact-match and longest-match address searches, which
result in high-speed forwarding. SDM manages TCAM space by partitioning application-specific
switching information into multiple regions.
TCAM identifies a location index associated with each packet forwarded and conveys it to the
forwarding engine. The forwarding engine uses this location index to derive information associated with
each forwarded packet.
The key benefits of SDM in switching are its ability to organize the switching information in TCAM into
application-specific regions and its ability to configure the size of these application regions. SDM
enables exact-match and longest-match address searches, which result in high-speed forwarding.

SDM Regions

SDM partitions TCAM space into multiple application-specific regions and interacts with the individual
application control layers to store switching information. SDM consists of the following types of
regions:
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Cisco ONS 15454 SONET/SDH ML-Series Multilayer Ethernet Card Software Feature and Configuration Guide, R4.0
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Understanding the SDM, page 14-1
Configuring SDM, page 14-2
Exact-match region—The exact-match region consists of entries for multiple application regions
such as IP adjacencies.
Longest-match region—Each longest-match region consists of multiple buckets or groups of
Layer 3 address entries organized in decreasing order by mask length. All entries within a bucket
share the same mask value and key size. The buckets can change their size dynamically by
borrowing address entries from neighboring buckets. Although the size of the whole application
region is fixed, you can reconfigure it.
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