Specifications
112 ExtremeWare XOS 11.0 Concepts Guide
Quality of Service
NOTE
The source port and VLAN QoS apply only to untagged packets, and 802.1P QoS applies only to
tagged packets.
ACL-Based Traffic Groupings
ACL-based traffic groupings are based on any combination of the following items:
• IP source or destination address
• IP protocol
• TCP flag
• TCP/UDP or other Layer 4 protocol
• TCP/UDP port information
• MAC source or destination address
• Ethertype
ACL-based traffic groupings are defined using access lists. Access lists are discussed in detail in
Chapter 10. By supplying a named QoS profile on an ACL rule, you can prescribe the bandwidth
management and priority handling for that traffic grouping. This level of packet filtering has no impact
on performance.
Explicit Class of Service (802.1p and DiffServ) Traffic Groupings
This category of traffic groupings describes what is sometimes referred to as explicit packet marking, and
refers to information contained within a packet intended to explicitly determine a class of service. That
information includes:
• Prioritization bits used in IEEE 802.1p packets
• IP Differentiated Services (DiffServ) code points, formerly known as IP Type of Service (TOS) bits
An advantage of explicit packet marking is that the class of service information can be carried
throughout the network infrastructure, without repeating what can be complex traffic grouping policies
at each switch location. Another advantage is that endstations can perform their own packet marking
on an application-specific basis. Extreme Networks switch products have the capability of observing
and manipulating packet marking information with no performance penalty.
The documented capabilities for 802.1p priority markings or DiffServ capabilities (if supported) are not
impacted by the switching or routing configuration of the switch. For example, 802.1p information can
be preserved across a routed switch boundary and DiffServ code points can be observed or overwritten
across a Layer 2 switch boundary.
Configuring 802.1p Priority
Extreme Networks switches support the standard IEEE 802.1p priority bits that are part of a tagged
Ethernet packet. The 802.1p bits can be used to prioritize the packet and to assign that packet to a
particular QoS profile.
When a tagged packet arrives at the switch, the switch examines the 802.1p priority field and maps the
packet to a specific hardware queue when subsequently transmitting the packet. The 802.1p priority