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Configuring I/O Modules

Extreme Networks Consolidated Hardware Guide 269

• Permanent Virtual Circuits (PVCs) may be associated with one or more VLANs

• Routed and bridged encapsulations on the same PVC

• Jumbo frames

• QoS and DiffServ features, including support for:

— Eight ingress queues and eight egress queues per interface

— Ingress and egress rate shaping and limiting

— IEEE 802.1p VLAN priorities

— WRED congestion avoidance algorithm

— Assured Forwarding and Expedited Forwarding RFCs

• Service provider specific features, such as:

— Flexible remapping of DiffServ codepoints

— Flexible remapping of IEEE 802.1Q VLAN IDs

— VLAN tunneling via nested 802.1Q tags

Function Summary

The following sections provide brief descriptions of the key functions provided by the ATM module.

For more information on how to configure the ATM modules, see the ExtremeWare Software User Guide

and the ExtremeWare Command Reference Guide.

ATM. ATM is a connection-oriented packet transmission technique that is widely used in existing

telecommunications networks to transport voice, video, and data. ATM uses fixed size data packets

called “cells” which are 53-bytes long and have a header that includes a connection identifier. The

connection identifier makes it possible to support more than one point-to-point connection on a single

physical ATM connection. The switches in an ATM network use the connection identifier in each cell to

forward the cell to the next hop.

SONET and SDH. SONET and SDH are the two terms used to identify a time division multiplexing

technology that is optimized for transporting voice traffic across a digital optical network, but that is

also capable of providing high-speed capacity for transporting data.

The term SONET is used to identify the technology used within the North American digital network. Its

standards are published by Bellcore and the American National Standards Institute (ANSI). The term

SDH is used to identify the equivalent standard approved by the International Telecommunication

Union (ITU) for use in Europe and elsewhere in the global digital network. Because SDH evolved out of

SONET, the two standards are closely related and have been widely accepted as a dominant choice for

implementations requiring high transport capacity and resistance to failure. The term 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.

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