Cisco Cisco MGX-FRSM-HS2 B Serial Frame Service Module Libro blanco
Deployment Guide
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Scenario 6: Using NAM to Monitor QoS/DiffServ
Differentiated Services (DiffServ) provides insight into how the traffic is being classified by QoS and detects
incorrectly marked or unauthorized traffic. NAM identifies the application/protocol based on the type of service (ToS)
bits setting. The administrator must configure DiffServ profiles based on templates provided or create one (Figure
18). The voice template can be used to monitor whether voice traffic is marked properly. Figure 19 displays the
DiffServ application statistics for DSCP value 0. Looking at this you’ll notice that RTP and Skinny Client Control
Protocol (SCCP) are listed, which indicates that they are not being correctly marked throughout its path.
Deployment: IT has deployed QoS to prioritize VoIP traffic to improve voice quality across the network. The NAMs
are deployed in the data center and branches and utilized to monitor the DSCP to validate QoS policies.
Step 1. Access the NAM and create a DiffServ profile for voice in Setup -> Monitor -> DiffServ Profile. Select the
desired DSCP value such as 46 for RTP and 24 for SCCP signaling.
Figure 18. Creating DiffServ Monitor Profile
Step 2. Access the DiffServ monitoring screen to display the protocols detected on each of the DSCP values.
Notice that rtp and sccp are highlighted in Figure 19. The protocols are listed for DSCP 0, which is incorrect
since the standard classification for voice traffic is DSCP 46 and for signaling is DSCP 24. This informs the
administrator that some of the voice traffic is misclassified on the network. The administrator can also view
the branch NAMs to investigate whether voice traffic is being misclassified.