Extreme Networks BlackDiamond 6800 Installation And User Manual page 22

Overview
SONET is used through out this guide. In instances where there are differences between
SONET and SDH, the differences are explicitly called out.
Jumbo Frames
The ATM module ports provide jumbo frame support that is similar to that provided by
Ethernet ports on a BlackDiamond 6800 series switch.
Jumbo frames are Ethernet frames that are larger than 1522 bytes, including four bytes
used for the cyclic redundancy check (CRC). Extreme products that use the "i" chipset
support switching and routing of jumbo frames at wire-speed on all ports.
Jumbo frames are used between endstations that support larger frame sizes for more
efficient transfers of bulk data. Both endstations involved in the transfer must be
capable of supporting jumbo frames.
QoS and Differentiated Services
The ATM module supports eight ingress queues and eight egress queues per port. The
scheduling parameters for these queues (minimum bandwidth, maximum bandwidth,
priority level, etc.) are controlled by QoS profiles that you can customize for individual
ingress or egress queues on a specific ATM port.
You can assign frames to queues based on IEEE 802.1p priorities, Differentiated Services
Code Points (DSCPs), or by configuring a QoS profile for the port or VLAN. You can
tailor the DSCP-to-queue mapping on a per-port basis. Most of the existing ingress
classification functions, along with the DiffServ replacement functions, are also
supported for ATM ports.
The supported DiffServ functions maximize user flexibility while providing all of the
features needed to support the standard per-hop behaviors (PHBs), including:
• Default
• Class Selector
• Assured Forwarding
• Expedited Forwarding
The ATM module also provides flexible support for the well-known Weighted RED
(WRED) congestion avoidance algorithm.
1-8 Asynchronous Transfer Mode (ATM) Module Installation and User Guide