Juniper JUNOSE 11.2.X IP SERVICES, Configuration Manual

Page: 118 / 356

Aggregation Caches
Data from flow cache entries is summarized to build aggregated views or aggregation
caches. Aggregation caches are created and maintained along with the main cache.
Aggregation caches have their own history area where the aging aggregation cache
records are collected. Aggregation caches have a set of configuration parameters: number
of entries, active and inactive time out, and export destination.
Types of aggregation caches include:
• AS-Aggregates flow data based on source and destination AS, and ingress and egress
interface values.
•
Destination Prefix-Aggregates flow data based on the destination address, mask,
destination AS, and egress interface.
• Prefix-Aggregates flow data based on source prefix, destination prefix, source mask,
destination mask, source AS, destination AS, ingress interface, and egress interface.
•
Protocol Port-Aggregates flow data based on protocol, source port, and destination
port.
• Source Prefix-Aggregates flow data based on source address, source mask, source
AS, and ingress interface.
Aggregation caches contain a subset of the fields collected in the raw flow data. For
example, TCP flags, Next Hop Address, and ToS values are not maintained in any of the
aggregation caches. Unlike the main cache, aggregation caches are not enabled by
default.
Flow Collection
The JunosE J-Flow functionality allows statistics collection at the VR/VRF level. This
means that each virtual router (VR)/VPN routing and forwarding (VRF) table has its own
main cache for statistics gathering.
Although you can export flow statistics only at the VR level, VRF data is rolled up for each
VR. The reason for supporting export flow at the VR level is that existing export formats
cannot discriminate between VRs and VRFs. However, even though export formats do
not allow for segregation, the JunosE CLI commands do. Segregating each collection by
VR removes any ambiguity and aliasing that may occur with overlapping address spaces
(as may occur in virtual private network [VPN] configurations).
Main Flow Cache Contents
The following 7-tuple distinguishes an entry in the flow cache for a VR:
• Source IP address (SA)
•
Destination IP address (DA)
•
Source port number (SP)
• Destination port number (DP)
• Layer 3 protocol type
Copyright © 2010, Juniper Networks, Inc. 92
JunosE 11.2.x IP Services Configuration Guide