The JUNOS software running on the Routing Engine and Packet Forwarding Engine consists of multiple processes that are responsible for individual functions. The separation of functions provides operational stability, because each process accesses its own protected memory space. In addition, because each process is a separate software package, you can selectively upgrade all or part of the JUNOS software, for added flexibility. The information below describes the main software processes that are running on EX-series switches platforms.

EX-series switches software are running the following main processes for the different functions on the switch. Each process, also known as daemon, is running as an independent software module.

chassisd - The chassis process.
chassisd process controls the chassis and its components as follows:

• Detects hardware on the system that is used to configure network interfaces.
• Monitors the physical status of hardware components and field-replaceable units (FRUs), detecting when environment sensors such as temperature sensors are triggered. 
• Relays signals and interrupts—for example, when devices are taken offline, so that the system can close sessions and shut down gracefully.

dcd - Interface process, also called device control process
dcd process Configures and monitors network interfaces by defining physical characteristics such as link encapsulation, hold times, and keepalive timers.
    
fwdd - Forwarding process
fwdd process is responsible for most of the packet transmission through an routing platform. The overall performance of the device is largely determined by the effectiveness of the forwarding process.
   
mgd - Management process
mgd process manages the system as follows:

• Provides communication between the other processes and an interface to the configuration database.
• Populates the configuration database with configuration information and retrieves the information when queried by other processes to ensure that the system operates as configured. 
• Interacts with the other processes when commands are issued through one of the user interfaces on the router.

rpd -  Routing protocol process
rpd process defines how routing protocols such as RIP, OSPF, and BGP operate on the device, including selecting routes and maintaining fowarding tables. 

• To monitor system process, use the command 'show system processes'. For example to monitor mgd process:

In this example, the management process is running through the command ' /usr/sbin/mgd -N' with process number 515.