Case Study: Your Turn to Use Your New Quality of Service Tools

Case Study: Your Turn to Use Your New "Quality of Service" Tools

In Chapter 3, "Paving the Pathway to a Voice over IP Network," you recommended an amount of bandwidth to interconnect XYZ Headquarters with XYZ Remote Office 1 and XYZ Remote Office 2. Based on your bandwidth recommendations from the Chapter 3 case study, in the following space, specify appropriate QoS mechanisms to deploy on the XYZ Headquarters router, XYZ Remote Office 1 router, and XYZ Remote Office 2 router.

QoS Recommendation for XYZ Company:

Suggested Solution

The suggested solution provided in Chapter 3 specified two T1 circuits (1.544 Mbps each) between XYZ Headquarters and XYZ Remote Office 1. The suggested bandwidth between XYZ Headquarters and XYZ Remote Office 2 was 512 kbps, as shown in Figure 6-27.

Figure 6-27. XYZ Company's Suggested Solution

Link efficiency mechanisms, such as LFI and cRTP, benefit slower link speeds (that is, less than 768 kbps). Based on the suggested bandwidth amounts, this solution recommends the following QoS mechanisms:

Link between XYZ Headquarters and XYZ Remote Office 1

• LLQ

• WRED

Link between XYZ Headquarters and XYZ Remote Office 2

• LLQ

• WRED

• cRTP

• MLP

WRED causes TCP packets to retransmit. However, RTP uses UDP. Therefore, while WRED benefits data traffic classes, WRED should not be applied to the voice traffic class. Also, note the suggested solution contains no policing or shaping mechanisms. However, if you determined that an application at one of XYZ Company's sites dominates the WAN bandwidth, a policing or shaping mechanism might be appropriate.