User guide

3-60 Packet Over SONET Module Installation and User Guide
Configuring the PoS Module
Configuring and Monitoring Flow Statistics
Each PoS port can maintain and export traffic statistics for the flows that traverse the
associated SONET link. A flow is defined as a unidirectional sequence of packets
between a particular source device and destination device that share the same protocol
and transport-layer information. Flows are defined by the following fields: source IP
address, destination IP address, source port, destination port, protocol type, and SONET
interface. Per-flow statistics are useful for many management purposes, including:
• Accounting and billing
• Network capacity planning and trend analysis
• Network monitoring
• Workload characterization
• User profiling
• Data warehousing and mining
Flow Statistics Background Information
Each PoS module can maintain two million flow records. Per-flow statistics are exported
in the NetFlow Version 1 record format described in Table 3-12. NetFlow records are
unidirectional in nature, which implies that two flow records are maintained for a
typical TCP connection: one record for flow in the ingress direction; a second for the
flow in the egress direction. Also, records are maintained only for TCP and UDP flows.
Table 3-12: NetFlow Version 1 Record Format
Field Name Octets Field Description
srcaddr 4 Source IP address
dstaddr 4 Destination IP address
nexthop 4 IP address of next-hop router; set to zero for per-flow
statistics; set to xFFFF for filter-based aggregated statistics
input 2 Input interface index; set to index of PoS interface for
ingress flows received from the SONET link; set to zero for
egress flows that are being transmitted over the SONET link
output 2 Output interface index; set to index of PoS interface for
egress flows that are being transmitted over the SONET link;
set to zero for ingress flows received from the SONET link