Full Classification Of Packets And Fabric Ingress Queueing; Egress Queues On The 40-Port Sfp+ Line Card; Understanding Priority-Based Flow Control; Reliability Of Packet Delivery In Standard Ethernet Networks And In Layer - Juniper JUNOS OS 10.4 - FOR EX REV 1 Manual

Complete Software Guide for Junos

Egress Queues on the 40-port SFP+ Line Card

Related
Documentation

Understanding Priority-Based Flow Control

Reliability of Packet Delivery in Standard Ethernet Networks and in Layer 2 Networks
3398
®
OS for EX Series Ethernet Switches, Release 10.4

Full Classification of Packets and Fabric Ingress Queueing

When the packets from a port group reach the Packet Forwarding Engine, it performs
full packet classification, along with other actions such as multifield (MF) classification,
traffic policing, and storm control. It then schedules and queues the packets for ingressing
the fabric. The fabric priority associated with the forwarding class determines whether
packets are sent to the low priority or high priority fabric ingress queues.
As with all EX Series switch interfaces, each interface on the 40-port SFP+ line card
supports eight egress CoS queues. You can map up to 16 forwarding classes to these
queues.
All interfaces in a port group also share a single set of eight egress chassis queues at the
Packet Forwarding Engine. Egress traffic is fanned out from the Packet Forwarding Engine
chassis queues to the corresponding queues for the individual ports. For this reason, the
interfaces in a port group must share the same scheduler map configuration. If you
configure different scheduler map configurations for the different interfaces in a port
group, an error is logged to the system log and the default scheduler map is used for the
ports in the port group.
Understanding Junos OS CoS Components for EX Series Switches on page 3376
Understanding CoS Schedulers on page 3387
Understanding CoS Forwarding Classes on page 3384
Example: Configuring CoS on EX Series Switches on page 3401
Configuring CoS Traffic Classification for Ingress Queuing on 40-port SFP+ Line Cards
(CLI Procedure) on page 3453
Priority-based flow control (PFC), IEEE standard 802.1Qbb, is a link-level flow control
mechanism. The flow control mechanism is similar to that used by IEEE 802.3x Ethernet
PAUSE, but it operates on individual priorities. Instead of pausing all traffic on a link, PFC
allows you to selectively pause traffic according to its class.
This topic describes:

Reliability of Packet Delivery in Standard Ethernet Networks and in Layer 2

Networks on page 3398
Calculations for Buffer Requirements When Using PFC PAUSE on page 3399
How PFC and Congestion Notification Profiles Work on page 3399
Standard Ethernet does not guarantee that a packet injected into the network will arrive
at its intended destination. Reliability is provided by upper-layer protocols. Generally, a
network path consists of multiple hops between the source and destination. A problem
Copyright © 2010, Juniper Networks, Inc.