Discard Eligible Bit; Differences Between Shaping Mechanisms - Cisco WS C4224V 8FXS - 200Mbps Ethernet Switch Software Configuration Manual

About Traffic Shaping

Discard Eligible Bit

Differences Between Shaping Mechanisms

Catalyst 4224 Access Gateway Switch Software Configuration Guide
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You can specify which Frame Relay packets have low priority or low time
sensitivity. These packets are the first to be dropped when a Frame Relay switch
is congested. The Discard Eligible (DE) bit allows a Frame Relay switch to
identify such packets.
You can define DE lists that identify the characteristics of packets to be eligible
for discarding, and you can also specify DE groups to identify the data-link
connection identifier (DLCI) that is affected.
You can specify DE lists based on the protocol or the interface. You can also
specify DE lists that are based on characteristics such as fragmentation of the
packet, a specific TCP or User Datagram Protocol (UDP) port, an access list
number, or a packet size.
GTS, Class-Based Shaping, DTS, and FRTS are similar in implementation,
sharing the same code and data structures, but they differ in regard to their CLIs
and the queue types they use.
Here are a few ways in which these mechanisms differ:
For GTS, the shaping queue is a weighted fair queue. For FRTS, the queue
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can be a weighted fair queue (configured by the frame-relay fair-queue
command), a strict priority queue with weighted fair queueing (WFQ)
(configured by the frame-relay ip rtp priority command in addition to the
frame-relay fair-queue command), custom queueing (CQ), priority
queueing (PQ), or first-in, first-out queueing (FIFO).
For Class-Based Shaping, GTS can be configured on a class, rather than only
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on an access control list (ACL). You must first define traffic classes based on
match criteria including protocols, ACLs, and input interfaces. You can then
apply traffic shaping to each defined class.
FRTS supports shaping on a per-DLCI basis; GTS and DTS are configurable
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per interface or subinterface.
DTS supports traffic shaping based on a variety of match criteria, including
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user-defined classes, and differentiated services code point (DSCP).
Chapter 10 Traffic Shaping
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