Medianet Reference Guide - Cisco

Cisco Network Analysis Module
Chapter 6
Medianet Management and Visibility Design Considerations
Finally, when multiple redundant equal-cost paths exist within the medianet infrastructure, Cisco
Express Forwarding (formerly known as CEF) load balances the traffic across the equal-cost paths using
a hash of the source and destination IP addresses for each session. Each router and switch along the path
independently creates its Cisco Express Forwarding table based on IP routing protocols, and load
balances sessions across its interfaces that represent equal-cost paths to the next hop along the path to
the destination. An IPSLA probe generated by a switch or router has a different IP source address than
the actual video device that is being pre-assessed. Therefore, the path taken by the IPSLA probes within
a highly redundant network infrastructure may not be exactly the path taken by the actual video traffic
from the device. The use of dedicated routers to perform an IPSLA network assessment eases this issue
slightly, because the routers can be configured to use the actual IP addresses that the video endpoints
will ultimately use. However, any changes to the Cisco Express Forwarding tables, brought about
through routing changes or reloading of the switches/routers along the path, may result in a slightly
different path established for the traffic when the actual video devices are installed. You should be aware
of these limitations of IPSLA within a highly redundant medianet infrastructure.
IPSLA as an Ongoing Performance Monitoring Tool
If configured with careful consideration, IPSLAs can also be used as an ongoing performance
monitoring tool. Rather than simulating an actual medianet video flow, IPSLA operations can be used to
periodically send small amounts of traffic between two points within the network, per service class, to
assess parameters such as packet loss, one-way latency, and jitter. Figure 6-20 shows an example of such
a deployment between two branches.
Figure 6-20
Example of IPSLA Used for Ongoing Performance Monitoring
Campus #1
Campus #2
SNMP
Threshold
Traps
QFP
Metro-Ethernet
or
MPLS Service
IPSLA Operation
QFP
Branch #1 Branch #2
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Medianet Reference Guide
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