About QoS settings
QoS settings are under Networking > Network Services: Quality of Service.
Before configuring QoS, we recommend that you add any applications to which you want to apply QoS that are not already defined in the default list. And all in-path interfaces are enabled for inbound and outbound QoS with the same link rate.
Enable Outbound QoS Shaping
Enables QoS classification to control the prioritization of different types of network traffic and to ensure that the appliance gives certain network traffic (for example, Voice over IP) higher priority than other network traffic. Traffic is not classified until at least one WAN interface is enabled. The system enables inbound and outbound QoS on all in-path interfaces by default.
Enable Inbound QoS Shaping
Enables QoS classification to allocate bandwidth and prioritize traffic flowing into the LAN network behind the SteelHead. Inbound QoS provides the benefits of QoS for environments that can’t meet their QoS requirements with outbound QoS.
Enable Outbound QoS Marking
Identifies outbound traffic using header parameters such as VLAN, DSCP, and protocols. You can also use Layer-7 protocol information through application definition inspection to apply DSCP marking. The DSCP or IP ToS marking only has local significance. You can set the DSCP or IP ToS values on the server-side appliance to values different to those set on client-side appliances.
Managing QoS settings per interface
By default, the system enables inbound and outbound QoS on all in-path interfaces except the primary interface. You can only enable outbound QoS on the primary interface. Inbound QoS supports in-path interfaces only; it doesn’t support primary or auxiliary interfaces.
Local site uplink bandwidth
Specifies the inbound (down) and outbound (up) bandwidth for local site uplinks. The appliance uses the bandwidth to precompute the end-to-end bandwidth for QoS. The appliance automatically sets the bandwidth for the default site to this value.
You can also access and edit these settings values, in addition to site-specific tasks such as adding an uplink, in the Networking > Topology: Sites & Networks page.
If you want to add an uplink, the settings here are identical to those under sites and networks.
About QoS class settings
Classes are organized in a hierarchical tree structure. All default classes are editable (except root), and you can add custom classes to the tree. QoS classes indicate how delay-sensitive a traffic class is to the QoS scheduler. They define minimum service guarantees; if better service is available, it’s provided. For example, if a class is specified as low priority and the higher-priority classes aren’t active, then the low-priority class receives the highest possible available priority for the current traffic conditions. This parameter controls the priority of the class relative to the other classes.
The service class describes only the delay sensitivity of a class, not how important the traffic is compared to other classes.
If you create QoS profiles, you can modify classes and combine them with rules to define the profile. Below is list of default classes.
• Use RealTime for your highest-priority, bandwidth intensive traffic such as VoIP or video conferencing.
• Interactive is primarily used for interactive traffic class such as Citrix, RDP, telnet, and SSH.
• Use BusinessCritical for high-priority traffic such as thick client applications, ERP, and CRM traffic.
• Use Normal for normal-priority traffic such as internet browsing, file sharing, and email.
• Use LowPriority for low-priority traffic such as FTP, backup, replication, other high-throughput data transfers, and recreational applications such as audio file sharing.
• Use BestEffort for your lowest priority applications.
Class Name
Specify a name for the QoS class.
Minimum Bandwidth %
Specify the minimum amount of bandwidth (as a percentage) to guarantee to a traffic class when there’s bandwidth contention. All of the classes combined can’t exceed 100 percent. During contention for bandwidth, the class is guaranteed the amount of bandwidth specified. The class receives more bandwidth if there’s unused bandwidth remaining.
Excess bandwidth is allocated based on the relative ratios of minimum bandwidth. The total minimum guaranteed bandwidth of all QoS classes must be less than or equal to 100 percent of the parent class.
A default class is automatically created with minimum bandwidth of 10 percent. Traffic that doesn’t match any of the rules is put into the default class. We recommend that you change the minimum bandwidth of the default class to the appropriate value.
You can adjust the value as low as 0 percent.
Maximum Bandwidth %
Specify the maximum allowed bandwidth (as a percentage) a class receives as a percentage of the parent class minimum bandwidth. The limit’s applied even if there’s excess bandwidth available.
Outbound Queue Type
SFQ—Shared Fair Queueing (SFQ) is the default queue for all classes. Determines SteelHead behavior when the number of packets in a QoS class outbound queue exceeds the configured queue length. When SFQ is used, packets are dropped from within the queue in a round-robin fashion, among the present traffic flows. SFQ ensures that each flow within the QoS class receives a fair share of output bandwidth relative to each other, preventing bursty flows from starving other flows within the QoS class.
FIFO—Transmits all flows in the order that they’re received (first in, first out). Bursty sources can cause long delays in delivering time-sensitive application traffic and potentially to network control and signaling messages.
MX-TCP—Has very different use cases than the other queue parameters. MX-TCP also has secondary effects that you must understand before configuring:
When optimized traffic is mapped into a QoS class with the MX-TCP queuing parameter, the TCP congestion-control mechanism for that traffic is altered on the SteelHead. The normal TCP behavior of reducing the outbound sending rate when detecting congestion or packet loss is disabled, and the outbound rate is made to match the guaranteed bandwidth configured on the QoS class.
You can use MX-TCP to achieve high-throughput rates even when the physical medium carrying the traffic has high-loss rates. For example, MX-TCP is commonly used for ensuring high throughput on satellite connections where a lower-layer-loss recovery technique is not in use.
Rate pacing for satellite deployments combines MX-TCP with a congestion-control method.
Another use of MX-TCP is to achieve high throughput over high-bandwidth, high-latency links, especially when intermediate routers don’t have properly tuned interface buffers. Improperly tuned router buffers cause TCP to perceive congestion in the network, resulting in unnecessarily dropped packets, even when the network can support high-throughput rates.
You must ensure the following when you enable MX-TCP:
• The QoS rule for MX-TCP must be at the top of QoS rules list.
• Only use MX-TCP for optimized traffic. MX-TCP doesn’t work for unoptimized traffic.
• Do not classify a traffic flow as MX-TCP and then subsequently classify it in a different queue.
• There is a maximum bandwidth setting for MX-TCP that allows traffic in the MX class to burst to the maximum level if the bandwidth is available.
Outbound DSCP
Selects the default DSCP mark for the class. QoS rules can then specify Inherit from Class for outbound DSCP to use the class default.
Select Preserve or a DSCP value from the drop-down list. This value is required when you enable QoS marking. The default setting is Preserve, which specifies that the DSCP level or IP ToS value found on pass-through and optimized traffic is unchanged when it passes through the SteelHead.
The DSCP marking values fall into these classes:
• Expedited forwarding (EF) class—In this class, packets are forwarded regardless of link share of other traffic. The class is suitable for preferential services requiring low delay, low packet loss, low jitter, and high bandwidth.
• Assured forwarding (AF) class—This class is divided into four subclasses. The QoS level of the AF class is lower than that of the EF class.
• Class selector (CS) class—This class is derived from the IP ToS field
Priority
Select a latency priority from 1 through 6, where 1 is the highest and 6 is the lowest. Optionally, add a new class and enter the values for the new class.
• To add an additional class as a peer with the existing classes, click add class at the bottom of the tree.
• To add an additional class as a subclass of an existing class, click add class to the right of the existing class.
Use a hierarchical tree structure to:
• divide traffic based on flow source or destination and apply different shaping rules and priorities to each leaf-class.
• effectively manage and support remote sites with different bandwidth characteristics.
The Management Console supports the configurations of three hierarchy levels. If you need more levels of hierarchy, you can configure them using the CLI. See the documentation for the qos profile class command in the Riverbed Command-Line Interface Reference Manual.
To remove the class, click the x at the corner of the window. To remove a parent class, delete all rules for the corresponding child classes first. When a parent class has rules or children, the x for the parent class is unavailable.
QoS rules
QoS rules assign traffic to a particular QoS class.
You can create multiple QoS rules for a profile. When multiple QoS rules are created for a profile, the rules are followed in the order in which they’re shown in the QoS Profile page and only the first matching rule is applied to the profile.
Appliances support up to 2000 rules and up to 500 sites. When a port label is used to add a QoS rule, the range of ports can’t be more than 2000 ports.
If a QoS rule is based on an application group, it counts as a single rule. Using application groups can significantly reduce the number of rules in a profile.
QoS rules assign traffic to a particular QoS class. Including the QoS rule in the profile prevents the repetitive configuration of QoS rules, because you can assign a QoS profile to multiple sites.
Make sure that you place the more granular QoS rules at the top of the QoS rules list. Rules from this list are applied from top to bottom. As soon as a rule is matched, the list is exited.
Application or Application Group
Specify the application or application group. We recommend using application groups for the easiest profile configuration and maintenance.
QoS Class
Select a service class for the application from the drop-down list, or select Inherit from Default Rule. Choose Inherit from Default Rule to use the class that is currently set for the default rule. The default setting is LowPriority
Outbound DSCP
Select Inherit from Class, Preserve, or a DSCP value from the drop-down list. This value is required when you enable QoS marking. The default setting is Inherit from Class.
Preserve specifies that the DSCP level or IP ToS value found on pass-through and optimized traffic is unchanged when it passes through the SteelHead.
When you specify a DSCP marking value in a rule, it either takes precedence over or inherits the value in a class.
After you save your changes, the newly created QoS rule displays in the QoS rules table of the QoS profile.