Understanding Cos Forwarding Classes; Default Forwarding Classes - Juniper JUNOS OS 10.4 - FOR EX REV 1 Manual

Complete Software Guide for Junos

Understanding CoS Forwarding Classes

Default Forwarding Classes

3384
®
OS for EX Series Ethernet Switches, Release 10.4
It is helpful to think of forwarding classes as output queues. In effect, the end result of
classification is the identification of an output queue for a particular packet. For a classifier
to assign an output queue to each packet, it must associate the packet with one of the
following forwarding classes:
expedited-forwarding (ef)—Provides a low loss, low latency, low jitter, assured
bandwidth, end-to-end service.
assured-forwarding (af)—Provides a group of values you can define and includes four
subclasses: AF1, AF2, AF3, and AF4, each with two drop probabilities: low and high.
best-effort (be)—Provides no service profile. Loss priority is typically not carried in a
class-of-service (CoS) value.
network-control (nc)—Supports protocol control and thus is typically high priority.
multicast best-effort (mcast-be)—Used for high-priority multicast packets.
multicast assured-forwarding (mcast-af)—Provides two drop profiles, high and low,
for multicast packets.
multicast best-effort (mcast-be)—Provides no service profile for multicast packets.
NOTE: The forwarding classes multicast expedited-forwarding, multicast
assured-forwarding, and multicast best-effort are applicable only to Juniper
Networks EX8200 Ethernet Switches.
Juniper Networks EX Series Ethernet Switches support up to 16 forwarding classes, thus
allowing granular packet classification. For example, you can configure multiple classes
of EF traffic such as EF, EF1, and EF2.
EX Series switches support up to eight output queues. Therefore, if you configure more
than eight forwarding classes, you must map multiple forwarding classes to single output
queues.
Default Forwarding Classes on page 3384
Table 442 on page 3385 shows the four default forwarding classes defined for unicast
traffic, and Table 443 on page 3385 shows the three default forwarding classes defined
for multicast traffic.
NOTE: The default forwarding classes for multicast traffic are applicable
only to EX8200 switches.
If desired, you can rename the forwarding classes associated with the queues supported
on your switch. Assigning a new class name to an output queue does not alter the default
Copyright © 2010, Juniper Networks, Inc.