Qos And Ethernet Link Redundancy; Active Link Failure And Qos; Administratively Disabling A Link And Qos; Adding A New Link To The Lag And Qos - Juniper JUNOSE SOFTWARE FOR E SERIES 11.3.X - QUALITY OF SERVICE CONFIGURATION GUIDE 2010-09-22 Configuration Manual

QoS and Ethernet Link Redundancy

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Documentation

Hashed Load Balancing for 802.3ad Link Aggregation Groups Overview

Copyright © 2010, Juniper Networks, Inc.
You can configure Ethernet link redundancy for LAG interfaces. When you configure QoS
for those links, be sure to consider the following behaviors.

Active Link Failure and QoS

When an active link fails, traffic that is hashed-load balanced is redirected onto the
remaining active links in the LAG. Traffic that is hashed-load balanced might be lost on
the disabled link, but from the moment of switchover, traffic arriving from the fabric on
the egress line module is directed towards one of the remaining hashed load-balanced
queues.
Subscriber loadbalanced traffic takes more time to reestablish on active links because
of the amount of computation (approximately 3 ms per subscriber). During this time
period, traffic directed to the disabled link might be lost.

Administratively Disabling a Link and QoS

When a link is administratively disabled, the system immediately redirects traffic from
the link to other links in the LAG.

Adding a New Link to the LAG and QoS

When you add a new link to the LAG, the system immediately sends traffic that is
hashed-load balanced to the link. Traffic that is subscriber-load balanced moves to the
new link as new subscribers log in. The system automatically rebalances traffic to the
new link based on the load rebalance configuration for the LAG.
Hashed Load Balancing for 802.3ad Link Aggregation Groups Overview on page 177
Subscriber Load Balancing for 802.3ad Link Aggregation Groups Overview on page 178
For more information about configuring the lag-default QoS profile for default subscriber
load balancing, see Enabling Default Subscriber Load Balancing for 802.3ad Link
Aggregation Groups on page 183
For more information about Ethernet link redundancy, see JunosE Link Layer
Configuration Guide
For more information about configuring QoS parameters, see Parameter Definition
Attributes for QoS Administrators Overview on page 215
For more information about the munge algorithm, see Munged QoS Profile Overview
on page 130
For a list of modules that support 802.3ad link aggregation, see the ERX Module Guide
and the E120 and E320 Module Guide
To configure hashed load balancing, you configure a scheduler hierarchy with Ethernet
queues and the system replicates the queues for each link within the LAG. The system
Chapter 21: Configuring QoS for 802.3ad Link Aggregation Groups
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