[JUNOS] Class of Service – Queuing and Scheduling

 

CoS Process

 

Why we need Queuing process and when we use it?

Queuing and scheduling control the prioritization of traffic flows

    <> Queue priority – which forwarding class (FC) gets more/less access to the outbound interface

    <> Transmission rate – how much bandwidth each FC gets.

    <> Delay buffer – how many packets can be held during congestion

    <> Congestion management – which flows get dropped during congestion.

 

[JUNOS] Class of Service – Policing

 

CoS Process

 

Why Policing?

Policing controls inbound traffic burstiness

   <> Defines what is considered ‘too much’ traffic

   <> Can be applied to an entire interface

   <> Can be applied to a specific traffic flow

   <> Traffic exceeding threshold can be dropped or given lower priority

 

JunOS have 3 type of policing

     1. Single-Rate Two-Color Marking

     2. Single-Rate Three-Color Marking

     3. Two-Rate Three-Color Marking

[JUNOS] Class of Service – Classification

 

CoS process

 

What is Classification?

Classifier assigns inbound traffic to forwarding classes

# can identify and separate traffic based on incoming packet’s header fields

     <> CoS bits

     <> Protocol, port, addresses, etc.

# Forwarding classes are linked to physical queues in the devices.

# Classifiers also specify loss priority (drop precedence)

     <> Used by policer and scheduler to help determine which traffic to drop under congestion

 

2 types of classification

  # Multifield (MF) classification

     <> Can separate incoming traffic based on packet header field. (ex: IP, ports number, etc)

     <> Configured using a firewall filter; apply to an interface/VLAN.

  # Behavior Aggregation (BA) classification

     <> Can separate incoming traffic based on CoS marking

     <> Configured using a “classifiers”; apply to an interface/VLAN.