OTJNR Mod 02

Module 2: JUNOS Software Architecture 2-1

Module 2: JUNOS Software Architecture

Operation & Troubleshooting Juniper Networks Routers


Module Objectives

l After successfully completing this module, you will be able to:

– Identify the software components and architecture of the JUNOS software

– State how the software components work together– Describe the tools available to monitor and troubleshoot

Juniper Networks routers and JUNOS software

This Module Discusses:– JUNOS software architecture and components;– How the various components work together; and– The tools available to monitor and troubleshoot Juniper Networks routers

and JUNOS software.


Software Features

l Where we are going…– JUNOS Internet software runs on the Routing Engine and

consists of:§ JUNOS Kernel§ Routing Protocol Process§ Interface Process§ Chassis Process§ SNMP Process§ Management Process§ Command-Line Interface

– Software monitoring tools– Management ports

JUNOS Internet Software FeaturesThe following pages discuss the JUNOS software features.


Software Processes

User

RoutingTables

RoutingProtocol Process

InterfaceProcess

Command-LineInterface (CLI)

ChassisProcess

SNMP

ForwardingTable Kernel

ForwardingTable

InterfaceProcess

ChassisProcess

Microkernel

DistributedASICs

JUNOS Internet SoftwareRoutingEngine

Embedded Microkernel

PacketForwardingEngine

Software Processes OverviewThe software consists of a series of system processes that handle the router’s management processes, routing protocols, and control functions. The JUNOS kernel, which is responsible for scheduling and device control, underlies and supports these processes. The JUNOS architecture is a multi-module design, with each process running in protected memory to guard against system crashes and to ensure runaway applications do not corrupt each other. This modular design makes it significantly easier to restart or upgrade a specific module because you do not have to reboot the entire chassis. The introduction of services is a highly reliable process because the failure of one module does not impact the entire operating system adversely. Between these independent modules, there are clean, well-defined interfaces, which provide interprocess communication, resulting in a highly reliable software architecture.JUNOS software resides in the Routing Engine, which runs an Intel-based PCI platform. The Routing Engine has a dedicated 100 Mbps internal connection to the Packet Forwarding Engine, which is responsible for packet flow through the router.The Routing Engine connects directly to the Packet Forwarding Engine. This separation of routing and forwarding performance ensures that the Routing Engine never processes transit packets. Of the traffic that goes to the Routing Engine, Data Link Layer Keepalives and routing protocol updates receive the highest priority to ensure that adjacencies never go down—regardless of the load—thereby preventing failures from cascading through the network.Additionally, the JUNOS software passes incremental changes in the forwarding tree to the Packet Forwarding Engine so that high rates of change are handled quickly and cleanly. Together, the nearly instantaneous routing updates and the JUNOS software ensure that the Packet Forwarding Engine continues to forward packets at wire-rate speeds during times of heavy route fluctuations.


JUNOS Kernel

l JUNOS kernel– Provides the underlying infrastructure for all the JUNOS

software processes§ Provides the link between the routing tables and the Routing Engine's

forwarding table§ Responsible for all communication with the Packet Forwarding Engine,

including keeping the Packet Forwarding Engine’s copy of the forwarding table synchronized


InterfaceProcess

Command-Line

Interface (CLI)ChassisProcess

ForwardingTable Kernel

JUNOS KernelThe Routing Engine (JUNOS) kernel provides the underlying infrastructure for all the JUNOS software processes. In addition, the kernel provides the link between the routing tables and the Routing Engine's forwarding table. It is also responsible for all communication with the Packet Forwarding Engine, which includes keeping the Packet Forwarding Engine's copy of the forwarding table synchronized with the master copy in the Routing Engine


Kernel Robustness

l Fully independent software processes– Routing, interface control, management, chassis

management, SNMP, CLI, APS, VRRP– Protected memory environment

§ Serious error in one module does not impact other modules or packet forwarding

l Serious errors result in automatic memory snapshot (core) for examination by Juniper Networks TAC personnel

Independent Modular DesignSoftware modules inside the JUNOS software (called processes) are separated by hardware-assisted memory protection, which prevents one software process from accessing memory being used by another. This arrangement allows the system to recover from errors quickly and divides the software debugging tasks into manageable pieces. For example, a failure in the network management software module does not impact any of the routing protocols or the forwarding performance.

Serious Errors Result in Core DumpsAnother feature allows detailed failure information to be saved for the Juniper Technical Assistance Center. If a module fails, this feature logs the failure, generates a memory snapshot for use by the Juniper Technical Assistance Center, and restarts the module automatically—without interrupting packet forwarding. The memory snapshot is a file describing the exact state of the system when the error occurred. The snapshot allows Juniper engineering personnel to re-create the conditions causing the failure.


The Routing Protocol Process

l Where we are going…– The routing protocol daemon (rpd) provides the following

services:§ Core functions§ Industrial-strength protocols § Routing and Forwarding Tables

The Routing Protocol Daemon (rpd)The following pages describe each of the responsibilities of the routing protocol process.


Routing Protocol Process

l Core functions– Controls routing protocols running on router– Starts all configured protocols– Handles all routing messages– Maintains routing tables– Implements routing policy

RoutingTables


Kernel

rpd Core FunctionsThe routing protocol process controls the routing protocols running on the router. It starts all configured routing protocols and handles all routing messages. It also maintains one or more routing tables, also called the Routing Information Base (RIB), which consolidate the routing information learned from all routing protocols into common tables.From this routing information, the routing protocol process determines the active routes to network destinations and installs these routes into the Routing Engine's forwarding table, also called the Forwarding Information Base (FIB). Finally, it implements routing policy, which allows you to control the routing information that is transferred between the routing protocols and the routing table. Using routing policy, you can filter routing information so that only some of it is transferred, and you also can set properties associated with the routes.The JUNOS software implements full IP routing functionality, providing support for IP Version 4 (IPv4). The routing protocols are fully interoperable with existing IP routing protocols; they are developed to provide the scale and control necessary for the Internet core.


Industrial-Strength Protocols

l Unicast routing protocols– Intermediate System-to-Intermediate System (IS-IS)– Open Shortest Path First (OSPF)– Routing Information Protocol (RIP)– Border Gateway Protocol (BGP)

l Multicast routing protocols– Distance Vector Multicast Routing Protocol (DVMRP) – Protocol-Independent Multicast (PIM)– Multicast Source Discovery Protocol (MSDP)– Internet Group Management Protocol (IGMP) – Session Announcement Protocol and Session Description

Protocol (SAP/SDP)l MPLS application protocols

– Multiprotocol Label Switching (MPLS)– Resource Reservation Protocol (RSVP)– Label Distribution Protocol (LDP)

Unicast Routing Protocols– IS-IS: Intermediate System-to-Intermediate System (IS-IS) is an interior

gateway (IGP), link-state routing protocol for IP networks. – OSPF: Open Shortest Path First (OSPF), Version 2, is an IGP that was

developed for IP networks by the Internet Engineering Task Force (IETF). OSPF is a link-state protocol that makes routing decisions based on the SPF algorithm.

– RIP: Routing Information Protocol (RIP), Version 2, is a distance-vector IGP for IP networks based on the Bellman-Ford algorithm.

– BGP: Border Gateway Protocol (BGP), Version 4, is an exterior gateway protocol (EGP) that guarantees loop-free exchange of routing information between routing domains, also called autonomous systems.

Multicast Protocols– DVMRP: Distance Vector Multicast Routing Protocol (DVMRP) is a dense-

mode, or flood-and-prune, multicast routing protocol.– PIM-Sparse Mode and PIM-Dense Mode: Protocol-Independent Multicast

(PIM) is a multicast routing protocol. PIM-Sparse Mode routes to multicast groups that can span wide-area and interdomain internets. PIM-Dense Mode is a flood-and-prune protocol.

– MSDP: Multicast Source Discovery Protocol (MSDP) allows multiple PIM-Sparse Mode domains to be joined. A rendezvous point (RP) in a PIM-Sparse Mode domain has a peering relationship with an RP in another domain, enabling it to discover multicast sources from other domains.

– IGMP: Internet Group Management Protocol (IGMP), Versions 1 and 2, are used to manage membership in multicast groups.

Continued on next page.


MPLS Applications Protocols– MPLS: Multiprotocol Label Switching (MPLS), formerly known as tag

switching, allows you to configure label-switched paths (LSPs) through a network manually or dynamically. It lets you direct traffic through particular paths rather than rely on the IGP's least-cost algorithm to choose a path.

– RSVP: The Resource Reservation Protocol (RSVP), Version 1, provides a mechanism for engineering network traffic patterns that is independent of the shortest path decided upon by a routing protocol. RSVP itself is not a routing protocol; it operates with current and future unicast and multicast routing protocols. The primary purpose of the JUNOS RSVP software is to support dynamic signaling for MPLS LSPs.

– LDP: The Label Distribution Protocol (LDP) provides a mechanism fordistributing labels in non-traffic-engineered applications.


RIB/FIB Consistency

l Routing and Forwarding Tables– Routing protocol process maintains the Routing Engine's

routing tables – Determines the active routes to network destinations– Installs active routes into the Routing Engine's forwarding

table– JUNOS kernel copies the forwarding table to the Packet

Forwarding Engine

JUNOS Software Routing TablesA major function of the JUNOS software routing protocol process is to maintain the Routing Engine's routing tables and from these tables to determine the active routes to network destinations. The routing protocol process installs these routes into the Routing Engine's forwarding table. The JUNOS kernel then copies this forwarding table to the Packet Forwarding Engine.The routing protocol process maintains multiple routing tables. By default, no routing tables are created until the protocols and processes that use them are activated. The most common JUNOS software routing tables are:

– Unicast routing table: The inet.0 table stores routing information for all unicast routing protocols running on the router. IS-IS, OSPF, RIP, and BGP all store their routing information in this routing table. You can configure additional routes, such as static routes, to be included in this routing table.

– Multicast routing table (cache): The inet.1 table stores routing information for all the running multicast protocols. DVMRP and PIM both store their routing information in this routing table. You also can configure additional routes to be included in this routing table.

– MPLS routing table for path information: The inet.3 table stores MPLS path and label information for signaled LSPs.

– MPLS routing table: The mpls.0 table stores the label and next hop information needed for MPLS switching.


Interface Process

l The device control daemon (dcd) Allows you to configure and control the router’s physical and logical interfaces

– Interface location– Interface encapsulation– Interface-specific properties

l Communicates with the Packet Forwarding Engine.

InterfaceProcessKernel

Micro KernelMicro Kernel InterfaceProcess

RE

PFE

Interface ProcessThe JUNOS software interface process allows you to configure and control the physical interface devices and logical interfaces present in a router. You can configure various interface properties, such as the interface location, (or in which slot the FPC is installed in and in which location on the FPC the PIC is installed), the interface encapsulation, and interface-specific properties. You can configure the interfaces currently present in the router as well as interfaces currently not present but that you might add at a future time.

Interaction with Packet Forwarding Engine Micro KernelThe JUNOS software interface process communicates, through the JUNOS software kernel, with the interface process in the Packet Forwarding Engine, thus enabling the JUNOS software to track the status and condition of the router's interfaces.


Chassis Process

l The chassis daemon (chassisd) allows you to configure and control the properties of the router

– Conditions that trigger alarms– Clock sources

l Communicates directly with chassis process in Packet Forwarding Engine

ChassisProcessKernel

Micro KernelMicro Kernel ChassisProcess

RE

PFE

Chassis ProcessThe JUNOS software chassis process allows you to configure alarm management and the system reference clock. You configure various properties, such as the primary reference clock source or the mappings between particular alarms, and the severity of the alarm they eventually generate.

Interaction with Packet Forwarding Engine Micro KernelThe chassis process keeps track of the state of each chassis component by gathering that information from its twin process running on the Packet Forwarding Engine, thus enabling the JUNOS software to track the status and condition of the router’s chassis components.


SNMP Processes

l Simple Network Management Protocol (SNMP) master agent and various subagents (snmpd)

– Supports SNMP v1 and v2– Read-only capability: Get, GetNext, GetBulk– Set command limited in support


InterfaceProcess

ChassisProcess

SNMP

SNMP Process and SubagentsThe JUNOS software supports SNMP, which helps administrators monitor the state of a router. The software supports SNMP Version 1 and Version 2, also known as Version 2c, or v2c.The JUNOS software implementation of SNMP does not include any of the security features that were originally included in the IETF SNMP drafts, but were later dropped because of the inability to standardize on a particular method. The SNMP software is controlled by the JUNOS SNMP and MIB II processes, which consist of an SNMP master agent and various subagents. For security reasons, Juniper Networks has decided not to support the SNMP setcommand. However, we do support the Proxy ping MIB and traceroute MIB which allows routers in the network to ping each other to measure response quality. You use SNMP commands to start ping tests, collect results, and handle error conditions. The MIB supports RFC 2925 with proprietary extensions.


Management Process

l Management process (mgd) is responsible for the CLI– Configuration access to system– Manages the CLI– CLI is client of mgd

Management ProcessWithin the JUNOS software, mgd is responsible for starting the CLI, which is the primary tool you use to control and monitor the JUNOS Internet software. This management process starts the CLI when the router boots.


Command-Line Interface

l Command-line interface (CLI) is the primary interface to:

– Configure the JUNOS software– Monitor and troubleshoot the software, network connectivity,

and router hardware

Command-Line InterfaceThe command-line interface (CLI) is the interface to the JUNOS software that you use whenever you access the router from the console or through a remote network connection. The CLI provides commands that perform various tasks, including configuring the JUNOS software, monitoring and troubleshooting the software, connecting to the network, and configuring the router hardware.The CLI is a straightforward command interface. You type commands on a single line, and the commands are executed when you press the Enter key. The CLI provides command help and command completion, and it also provides EMACS-style keyboard sequences that allow you to move around on a command line and scroll through a buffer that contains recently executed commands.


Software Monitoring Tools

l CLI– Displays information and checks network connectivity

l SNMP– Supports MIB II SNMP version 1 traps and version 2

notifications– Supports SNMP version 1 Get and GetNext requests and

version 2 GetBulk requestsl Tracing and logging

– Sys-logging records high-level operations– Tracing records detailed messages about the operation of

routing protocols (debug)l Port mirroring

– Allows you to configure next-hop sampling of a packet stream

Monitoring with the CLIThe primary method of monitoring and troubleshooting the software, routing protocols, network connectivity, and the router hardware is to enter commands from the CLI. The CLI lets you display information in the routing tables, display routing protocol-specific information, and check network connectivity using ping and traceroute.

SNMPThe JUNOS software includes SNMP software, which allows you to manage routers. The SNMP software consists of an SNMP master agent and a MIB II agent; it supports MIB II SNMP version 1 traps and version 2 notifications, SNMP version 1 Get and GetNext requests, and version 2 GetBulk requests.

Tracing and LoggingThe software also supports tracing and logging operations so that you can track events that occur in the router (both normal router operations and error conditions) and track the packets that are generated by, or pass through, the router. Logging operations use a syslog-like mechanism to record system-wide, high-level operations, such as interfaces going up or down, and users logging into or out of the router. Tracing operations record more detailed messages about the operation of routing protocols, such as the various types of routing protocol packets sent and received, and routing policy actions.

Mirroring PortsMirroring ports allows you to configure next-hop sampling of a packet stream, whereby you direct the output to a specific interface or next-hop router. To configure, include the port-mirroring statement at the [edit forwarding-options sampling output] hierarchy level and specify either an interface name (for point-to-point links) or a next-hop address along with the interface name (for nonpoint-to-point links).


Network Management Ports

l Ports available for network management:– Console port

§ Pre-configured– Auxiliary port– Ethernet management port

Network Management PortsBelow is a listing of the ports available for network management.

– Console port: Connects a system console using an EIA/TIA-232 serial cable. This port is the only port that comes pre-configured on the router.

– Auxiliary port: Connects a laptop or modem using an EIA/TIA-232 serial cable. It is actually the same as the console port, but it is disabled by default.

– Ethernet management port: Connects the Routing Engine to a management LAN or any other device that plugs into an Ethernet connection, for out-of-band management of the router. The Ethernet port is 10/100 Mbps autosensing and requires an RJ45 connector.


End-of-Life Procedures

l Software EOL– Software support covers most recent release and two

previous (that is, Releases 5.3, 5.2, 5.1)– New releases schedule for first revenue shipment (FRS) every

three months– Major release—six month notice of EOL

l Hardware EOL– Notification 180 days in advance– Can continue to purchase during notification period– Repaired or replaced up to three years after EOL date

Software EOLOur software support covers three major releases, including the most recent release and the two previous releases (that is, Releases 5.3, 5.2, 5.1). New major releases are scheduled for first revenue shipment (FRS) every three months. Juniper Networks provides six month's notice of the EOL of a major release.

Hardware EOLJuniper Networks provides an EOL policy notification for discontinued systems to the customer, either directly or through the Customer Support Center (CSC), at least 180 days in advance of the EOL date. During the notification period, the customer can continue to purchase such systems (subject to availability), provided that delivery is taken within 180 days of the EOL effective date. EOL systems shall be repaired, or replaced with similar products, at Juniper Networks' discretion for up to three years after the EOL effective date. If such repair or replacement is not covered under warranty, the customer is charged Juniper Networks' then-standard rates.


Review Questions

1. Which process maintains the routing tables and implements routing policy?

2. Which process tracks the status and conditions of a Juniper Networks router?

3. What is the purpose of the command-line interface and how do you access it?

4. What methods can be used to troubleshoot and monitor JUNOS software processes?

This Module Discussed:– JUNOS software architecture and components;– How the various components work together; and– The tools available to monitor and troubleshoot JUNOS software processes.

Documents

OTJNR Mod 02