Introduction to the Junos Operating System Chapter 2: Junos Operating System Fundamentals

Chapter Objectives After successfully completing this chapter, you will be able to: Describe the Junos operating system and its basic design architecture Explain traffic processing for transit and exception traffic Identify and provide a brief overview of Junos devices

Agenda: Junos Operating System Fundamentals The Junos OS Traffic Processing Overview of Junos Devices

The Junos OS Robust, modular operating system Provides industry-leading performance and scalability Based on the FreeBSD UNIX operating system

Single Software Train A single software train for all platforms running the Junos OS Eases management overhead by providing a consistent set of features that are implemented in a consistent manner 12.0 12.1 … J2320 TX Matrix

Separation of Control and Forwarding All platforms running the Junos OS share a common design goal: Clean separation of control and forwarding functions Routing Engine RT FT The Junos OS Control Plane Internal Link Forwarding Plane FT Frames/Packets In Frames/Packets Out Packet Forwarding Engine

Packet Forwarding Engine Routing Engine Maintains routing and forwarding tables Controls and monitors the chassis Manages the PFE Routing Engine RT FT The Junos OS Control Plane Forwarding Plane Packet Forwarding Engine

Packet Forwarding Engine Uses Layer 2 and Layer 3 forwarding tables, provided by the RE, to forward traffic toward its destination Implements various services such as policing, stateless firewall filtering, and class of service Routing Engine Control Plane Forwarding Plane FT Frames/Packets In Frames/Packets Out Packet Forwarding Engine

Agenda: Junos Operating System Fundamentals The Junos OS Traffic Processing Overview of Junos Devices

Transit Traffic Processing Transit traffic is forwarded through the local system PFE uses the forwarding table provided by the RE Examples of transit traffic include unicast and multicast traffic Routing Engine CPU Control Plane Forwarding Plane FT Frames/Packets In Frames/Packets Out Packet Forwarding Engine

Exception Traffic Processing (1 of 2) Exception traffic is processed by the local system Traffic destined for the local system is processed by RE CPU In most cases, the PFE processes traffic requiring the generation of ICMP messages, such as TTL expired Routing Engine CPU Control Plane Forwarding Plane Frames/Packets In Frames/Packets Out Packet Forwarding Engine

Exception Traffic Processing (2 of 2) Exception traffic is rate-limited on the internal link to protect the RE from potential DoS attacks Control traffic is given preference when congestion exists Routing Engine CPU Control Plane Built-In Rate Limiting Forwarding Plane Frames/Packets In Packet Forwarding Engine

Agenda: Junos Operating System Fundamentals The Junos OS Traffic Processing Overview of Junos Devices

Overview of Junos Devices Platforms running the Junos OS span switching, routing, and security roles and are suited for small to large networks in both enterprise and service provider environments Routing Switching Security

Junos Routing Devices M Series LN Series ACX Series PTX Series MX Series T Series

Junos Switching Devices QFX Series EX Series

Junos Security Devices J Series SRX Series

Summary In this chapter, we: Described the Junos OS and its basic design architecture Explained how transit and exception traffic is processed Identified and provided a brief overview of Junos devices

Review Questions What are some advantages of the Junos OS? What are the primary functions of the control plane and the forwarding plane on Junos devices? How are transit and exception traffic processed? Name three platforms that run the Junos OS.