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 11.1.X - QUALITY OF SERVICE CONFIGURATION GUIDE 3-21-2010 Configuration Manual

For example, a LAG instance can specify a shaping rate of 100 Mbps on an Ethernet
port or a group node. The system shapes all Ethernet ports or group nodes to the
same rate within the LAG. Using load balancing, the system strives to balance the
traffic each link equally.

QoS and Ethernet Link Redundancy

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.
Related Topics
Hashed Load Balancing for 802.3ad Link Aggregation Groups Overview on
page 186
Subscriber Load Balancing for 802.3ad Link Aggregation Groups Overview on
page 186
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 191
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 229
QoS for 802.3ad Link Aggregation Interfaces Overview
Chapter 21: Configuring QoS for 802.3ad Link Aggregation Groups
185