QoS Device Manager

Introduction

This month we take a look at Cisco's QoS Device Manager (QDM) application. This is a free application you download from Cisco. I've previously described QDM as "training wheels for QoS". That's perhaps dismissing it a little too quickly. The tool looks very useful for light management of QoS as well. It might be useful in both the test lab and for determining or revising your QoS policy. 

How To Use QDM

QDM installs in flash on the supported routers and switches. These models include the 1700, 2600, 3600, 7100, 7200, 7600, and VIP-enabled 7500 series of routers. The 6500 switch is also now supported in QDM 2.1. The documentation isn't clear whether Hybrid IOS is required or whether you just run QDM on the MSFC. I haven't had a chance to test this yet. Anybody that wants to donate a 6500 for my home lab is welcome to contact me at any time!

To access QDM, you do have to enable the built-in IOS web access. Point your web browser at the router or switch. There should be a link to QDM, if you installed the download file into flash with the required name. Click on the link. QDM is Java that runs on your PC, accessing the Cisco Class Based MIB (MIB data for Class Based Weighted Fair Queueing, CBWFQ). For more about CBWFQ, see the article New Quality of Service Features in Cisco IOS 12.1 , at http://www.netcraftsmen.net/welcher/papers/newqos121.html .

The rest of this article is a sample of what Cisco QDM can do. One reason for doing so is that QDM has little documentation, so there's no easy way for you to look at a PDF documentation file to see what QDM can do. That might tend to discourage people from actually using it, since it takes work and there's no immediately apparent value to expending the effort. 

This article is heavy on screen captures. Note how easy QDM is to use. Yes, it is a limited tool focused on QoS, so the User Interface has limited options. There are some CBWFQ QoS features not supported by QDM, documented in the Release Notes. Among them, applying a CBWFQ policy via sub-interface or FR traffic shaping is not currently supported. Older QoS techniques such as Committed Access Rate (CAR) are also not supported.

Getting Started with QDM 

You'll then see the QDM Main Screen, shown below.
 

On the main screen, there are the four main QDM tabs: System, Configure, Monitor (Graph), IOS CLI Access. 

The above screen capture shows what you see when you click on the System tab. There are auxiliary sub tabs or hotspots: Home Page, QDM Console, Help (not much!), About, Logout. The sub tab QDM Console shows a console for the Java Virtual Machine running QDM. These other tabs in the auxiliary list are fairly self-explanatory, so we will say nothing more about them. There is not hing else you can do from this tab, other than access the auxiliary sub tabs. Well, you can also click on the four colored boxes to bring up a legend. The interface list is not clickable.

QDM Configure Tab

 
Note the five sub tabs under Configure: Traffic Class, Traffic Policy, Apply to Interface, QoS for VPNs, Commit Config Changes. These are typically used from left to right. See below for what happens when you click on each one.

QDM Configure, Traffic Class Sub Tab

 

The Traffic Class sub tab lets you add new CBWFQ/MQC (Class-Based Weighted Fair Queuing / Modular QoS CLI) class definitions, or modify or delete existing ones. Click on Add to use a form to add a new class. You will be asked to name the class, optionally give it a description, and to then define the match criteria, for what network traffic constitutes the class. 

QDM Configure, Traffic Policy Sub Tab

This sub tab lets you add a new CBWFQ policy, or edit or delete an existing one. The following screen captures show adding a new policy. 

QDM Configure, Traffic Policy Sub Tab (2)

 

This shows the screen for adding a new policy and its description. Fill in the name and description, then click on Next to advance to the next form (see the next capture below).

QDM Configure, Traffic Policy Sub Tab (3)

 
You then select which classes are used in the policy. Note they can be re-ordered. When done putting classes into the policy, click Next to advance to the next screen. You then are asked to specify how each class is to be handled (not shown). The choices are priority (LLQ), bandwidth, police, shape, etc. 

QDM Configure, Apply to Interface Sub Tab

This screen specifies which interface(s) to apply the new QoS policy to, in what direction it is to be applied in, and whether to enable recording of QoS metrics or NBAR protocol discovery on the interface. 

Select an interface and specify per-interface settings (in/out policy to apply, whether to keep metrics history, and whether to enable NBAR protocol discovery on the interface). Clicking OK configures the router.

QDM Configure, Commit Config Changes Sub Tab

 
Commit saves the QoS configuration changes to NVRAM in the device.

QDM Monitor Main Screen

 
Monitor is a fancy word for "Graphs". This is the main Monitor screen, showing the graphs that have been defined. You can add new graphs or edit or delete existing graphs. You can also select a graph and click on the "Graph It!" button to graph it. 

QDM Monitor (2)

 
If you select an interface, you can create a graph showing some or all of the five quantities shown in the capture: packet rates, bit rates, byte counts, packet counts, or protocol discovery.

QDM Monitor -- Protocol Discovery Graph

 

The NBAR discovery graph shows top or selected applications identified on the interface (inbound only in Cisco IOS 12.2 (12a) and QDM 2.1.2). Note you can select which NBAR discovery data to graph.

QDM Monitor -- Tabular View

 

Every graph can also be viewed in tabular form. Click on the Table tab to see the data in tabular form.

QDM Monitor -- Per-Class Graphs

If a CBWFQ Policy is selected to the left of the screen, up to six other kinds of information can be graphed. They include the per-class queue depth, pre-policy packet count, pre-policy byte count or bit rate, per-class drop bit rate, and per-class post-policy bit rate. The point to these is that a class may have more offered traffic coming into the router than the policy or current congestion level allows out, especially if you're doing policing or shaping. Graphing them can help you understand what's happening within the router to the various classes of traffic. 

Note that QDM must have installed the policy into the router in order for it to know the policy exists and allow graphing. You won't see the policy to the left of the screen unless QDM installed it.

QDM Monitor -- Per-Class Graphs (2)

 
The graph shows per-policy data, specifically per-class bit rates.

QDM Monitor -- Per-Class Graphs (3)

 
Each policy graph can be toggled to tabular form by selecting the Table tab. 

QDM Monitor -- Single Class Graphs

Each single class of traffic can also be selected, with up to four items available for graphing. The items are pre-policy packet and byte counts, bit rates, and Low Latency Queuing (LLQ) data.

QDM Monitor -- Single Class Graphs (2)

 

This shows the results of watching the class class-default (all other traffic). You should be able to see the impact of a policy with the graph of pre/post bit rate data: how much traffic is being dropped by the policy.

QDM IOS CLI Interface

This tab gives access to some canned HTML show commands and CLI interface. This tab is basically a convenience hook into the router web interface, which is why I don't include a screen capture of it.

Saving Graphs

QDM does not have a built-in way to save graphs you define for the next session. Instead, you bookmark them in your browser to save them.

Conclusion

Dr. Peter J. Welcher (CCIE #1773, CCSI #94014) is a Senior Consultant with Chesapeake NetCraftsmen. NetCraftsmen is a high-end consulting firm and Cisco Premier Partner dedicated to quality consulting and knowledge transfer. NetCraftsmen has nine CCIE's, with expertise including large network high-availability routing/switching and design, VoIP, QoS, MPLS, network management, security, IP multicast, and other areas. See http://www.netcraftsmen.net for more information about NetCraftsmen. Pete's links start at http://www.netcraftsmen.net/welcher . New articles will be posted under the Articles link. Questions, suggestions for articles, etc. can be sent to pjw@netcraftsmen.net .