Configuring Quality of Service

Quality of Service rules evaluate and prioritize network traffic types. For example, you can prioritize phone calls (VoIP) or prioritize traffic from a certain department (group, VLANs) in a company. This chapter describes QoS settings for Wireless LAN System.

Configuring QoS Rules With the Web UI

To configure QoS rules from the GUI, follow these steps:

1. Click Configuration > QoS Settings > QoS and Firewall Rules (tab).
2. Click Add. The screen below appears.

Figure 69: Add a QoS Rule — change..

3. In the ID field, type a unique numeric identifier for the QoS rule. The valid range is from 0 to 6000.
4. In the Destination IP fields, type the destination IP address to be used as criteria for matching the QoS rule. The destination IP address is used with the destination subnet mask to determine matching.
5. In the Destination Netmask fields, type the subnet mask for the destination IP address.
6. In the Destination Port field, type the TCP or UDP port to be used as criteria for matching the QoS rule. To specify any port, type 0 (zero).
7. In the Source IP fields, type the source IP address to be used as the criteria for matching the QoS rule. The source IP address is used with the source subnet mask to determine matching.
8. In the Source Netmask fields, type the subnet mask for the source IP address.
9. In the Source Port field, type the TCP or UDP port to be used as criteria for matching the QoS rule. To specify any port, type 0 (zero).

10.In the Network Protocol field, type the protocol number of the flow protocol for the QoS rule. The protocol number can be a number 0 through 255. The protocol number of TCP is 6, and the protocol number for UDP is 17. For a list of protocol numbers, see http:// www.iana.org/assignments/protocol-numbers.

If you are also using a QoS protocol detector, you must match the network protocol with the type of QoS protocol. Use the following network protocol and QoS protocol matches:

• UDP: SIP
• TCP: H.323 or SIP

 

11.In the Firewall Filter ID field, enter the filter-ID to be used (per-user or per-ESS), if Policy Enforcement Module configuration is enabled (optional feature). This ID must be between 1 and 16 alphanumeric characters.

12.In the Packet minimum length field, specify the size of the minimum packet length needed to match the rule. (Valid range: 0-1500.)

13.In the Packet maximum length field, specify the size of the maximum packet length needed to match the rule. (Valid range: 0-1500.)

14.In the QoS Protocol dropdown list, select one of the following:

• SIP
• 323
• Other
• None

For capture rules, the QoS protocol determines which QoS protocol detector automatically derives the resources needed for the flow (implicitly). Select Other if you want to specify the resource requirements for matched flows explicitly. The QoS protocol value is ignored for non-capture rules.

15.In the Average Packet rate box, type the average flow packet rate. The rate can be from 0 through 200 packets/second.

16.In the Action list, select the action the rule specifies: • Forward: A flow is given an explicit resource request, bypassing the QoS protocol detector and regardless of whether a QoS protocol was specified.

• Capture: The system, using a QoS protocol detector, analyzes the flow for its resource requirements.
• Drop: The flow is dropped.

17.In the Token Bucket Rate box, type the rate (in Kbps or Mbps, depending on the option checked) at which tokens are placed into an imaginary token bucket. Each flow has its own bucket, to which tokens are added at a fixed rate. To send a packet, the system must remove the number of tokens equal to the size of the packet from the bucket. If there are not enough tokens, the system waits until enough tokens are in the bucket.

18.In the Priority box, type the priority at which the flow is placed in a best-effort queue. Packets in a higher priority best-effort queue are transmitted by access points before packets in lower-priority queues, but after packets for reserved flows.

Priority can be a value from 0 through 8, with 0 specifying no priority and 8 specifying the highest priority. The default value is 0. If you enable priority (specify a non-zero value), you cannot specify an average packet rate or token bucket rate.

19.In the Traffic Control list, select one of the following:

• On
• Off

For all types of flows (explicit, detected, and best-effort), selecting On for traffic control restricts the flow to the rate you specified. Packets above that rate are dropped.

20.In the DiffServ Codepoint list, select the appropriate DiffServ setting, if applicable.

21.In the QoS Rule Logging list, select whether to enable or disable logging activity for this QoS rule:

• On Off

22.In the QoS Rule Logging Frequency field, change the default collection interval in which packets related to this rule are logged, if QoS Logging is enabled. The interval must be a number between 30 and 60 (seconds).

23.Match Checkbox: For any field with the corresponding Match checkbox selected, the action mentioned in the ACTION field is performed on the matched packets. If the match checkbox is not checked, packets with any value are matched regardless of the data in the field and the action mentioned in the ACTION field is not performed on the packets. Also see “More About the Match Checkbox and Flow Class Checkbox” on page 383.

24.Flow Class Checkbox: Flow Class options are relevant only for Flow Control rules (rules with Traffic Control enabled and Token Bucket Rate specified) and Firewall rules. This is typically rate limiting. When Flow Class is checked for a field, if a packet has matched a rule (either Flow Control or Firewall types), these fields are stored in the Flow Class entry. A Flow Class entry is used by the system for aggregating a set of flows so that they can be subjected to similar behavior, be it dropping the packets, or rate limiting them.

For example, if a rule has a Src IP address of 0.0.0.0 and the Flow Class box checked, and Token Bucket Rate set to 10 kbytes/sec, all packets passing through the system must match this rule, and each flow will be allowed a maximum throughput of 10000 bytes/sec. If the rule were to have Src IP address of 10.0.0.10 and the Flow Class box checked, with a Token Bucket Rate of 10 kbytes/sec, all packets coming from a machine with IP address 10.0.0.10, must match this rule, and the cumulative throughput allowed for this machine shall be no more than 10000bytes/sec. Also see “More About the Match Checkbox and Flow Class Checkbox” on page 383.

25.To add the QoS rule, click OK.

QoS Rules for Bridge Mode Traffic

QoS rules support bridge mode traffic (IPv4). For bridge mode traffic the following conditions are matched to either Forward or Drop packets.

• Destination IP
• Destination Port
• Source IP
• Source Port
• Network Protocol: A QoS rule for bridge mode traffic must mandatorily include the network protocol if the destination or source port is specified.

The following are some points to consider while creating QoS rules for bridge mode traffic: • You can specify ports only for the protocols that support specifying ports. Protocols that do not have port specifications (example, ICMP etc.,) will be ignored by the AP.

• QoS rules with firewall filter-ID are ignored.
• Any rule with match value set to ‘0’ will be considered as a wildcard and will match ANY traffic.
• The QoS rules for bridge mode traffic do not support any other conditions including the Capture action. If application visibility is enabled, and if either QoS rule OR the app-visibility policy dictates a DROP action for a packet, the packet is going to be dropped. Packet is forwarded only if BOTH QoS and app-visibility allow it.

NOTES:

• Any rules that block traffic between controller and AP will cause AP – controller dis-connectivity and such rules should not be created.
• If the number of QoS rules exceed 50, it may affect overall system performance.

More About the Match Checkbox and Flow Class Checkbox

The two checkboxes Match and Flow Class operate independently from each other; they perform two different functions. Match will almost always be used because checking this box indicates that the setting on the left must match – this sets the matching criteria for the QoS rule. You can check more than one matching criteria. Matching is the first phase of QoS rule execution – see the green box in Figure 70.

After criteria are matched, the action phase of the QoS rule is executed. This phase is enclosed in the orange box in Figure 70. Here are the directions that describe what to do with the matched packet from phase 1, Matching. For example, the rule can capture the packet from a named source and drop it. Action is phase 2 of QoS rule execution.

The Flow Class column is all about rate limiting. If a rule involves rate limiting, the actions Traffic Control and Token Bucket Rate must have been turned on. When the QoS rule executes traffic control, it looks at the check marks in the flow class column. If there are no check marks at all, the rate limiting is applied to everything. If Destination, Source, or Network Protocol have Flow Class checked, the following happens:

• Destination Flow Class – Each destination flow is limited to the rate.
• Source Flow Class – All source flows combined must be less than or equal to the rate.
• Network Protocol Flow Class – Any data transported using this protocol is limited to the rate.

Figure 70: How QoS Rules Work — change