Classification and Marking Tools 189
Unlike most other IOS features, you can upgrade NBAR without changing to a later IOS version. Cisco uses a feature called packet descriptor language modules (PDLMs) to define new protocols that NBAR should match. When Cisco decides to add one or more new protocols to the list of protocols that NBAR should recognize, it creates and compiles a PDLM. You can then download the PDLM from Cisco, copy it into Flash memory, and add the ip nbar pdlm pdlmname command to the configuration, where pdlm-name is the name of the PDLM file in Flash memory. NBAR can then classify based on the protocol information from the new PDLM.
CB Marking show Commands
CB marking provides only one show command that provides statistical information: show policy-map interface. The statistics do provide some good insight to the packet volumes being marked by CB marking. The next sample configuration includes a new configuration and several variations of the show policy-map command.
The same network is used for the next example as was used in the other CB marking examples, but with different marking criteria. In this case, traffic is generated so that the show command output is more meaningful. The following traffic is generated:
•Two G.711 VoIP calls between R4 and R1 using Foreign Exchange Station (FXS) cards on these two routers. Voice Activation Detection (VAD) is disabled.
•One FTP connection from the client PC to the server, with an FTP get of a 40-MB file called big.zip.
•One Microsoft NetMeeting video/audio conference between the client and server.
•One web page download from the server to the client. The web page has a few small objects. The web page includes two panes, each with a different JPG file: one called important.jpg; the other called not-so.jpg. The JPGs are exact copies of each other, and each JPG is 687 KB. In later examples, the differing performance of the download of these examples is used to demonstrate the behavior of other QoS tools.
Figure 3-13 depicts the same familiar network, and lists the criteria in with the figure for easy reference.
The new criteria for Example 3-4 is as follows:
•VoIP payload is marked with DSCP EF.
•NetMeeting voice and video from Server 1 to Client 1 is marked with DSCP AF41.
•Any HTTP traffic whose URL contains the string “important” anywhere in the URL is marked with AF21.
•Any HTTP traffic whose URL contains the string “not-so” anywhere in the URL is marked with AF23.
•All other traffic is marked with DSCP Default.
190 Chapter 3: Classification and Marking
Figure 3-13 Three Classification and Marking Placement Strategies
Mark
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Mark VoIP as DSCP EF
Mark NetMeeting as AF41
Mark URLs with “Important” as AF21
Mark URLs with “Not” as AF23
Mark All Else with DSCP Default
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R4
1001 1002
3001 3002
Example 3-4 shows the configuration, including the appropriate show commands.
Example 3-4 CB Marking Sample 4, with show Command output
ip cef
!
interface fastethernet 0/0 ip nbar protocol-discovery
!
access-list 101 permit udp host 192.168.3.101 gt 16383 192.168.1.0 0.0.0.255 gt 16383
!
class-map voip-rtp
match ip rtp 16384 16383
!
class-map http-impo
match protocol http url "*important*"
!
class-map http-not
match protocol http url "*not-so*"
!
