JN0-335 Exam Dumps : Security, Specialist (JNCIS-SEC)

References:

• [SRX] Behavior of active sessions when modifying a security policy1

• Referring to the SRX Series flow module diagram shown in the exhibit, application security is processed at the Services ALGs stage. Application Layer Gateways (ALGs) are software components that enable the SRX Series device to provide application-level security for specific protocols and applications1.
• ALGs inspect the application layer payload of packets and perform various actions, such as modifying the payload, opening pinholes, creating sessions, applying security policies, and enforcing application-specific behavior12.
• ALGs are required for protocols and applications that embed IP address information or port numbers in the application layer data, that open secondary connections, or that are dynamically assigned ports1. Some examples of protocols and applications that require ALGs are FTP, SIP, H.323, RTSP, PPTP, and DNS2.
• ALGs are configured as part of the security policy and are applied to the traffic that matches the policy criteria. ALGs can also be enabled or disabled globally or per zone12.

References:

• 1: Application Layer Gateways Overview
• 2: Application Layer Gateways Feature Guide for Security Devices

An Application Layer Gateway (ALG) is a software component that is designed to manage specific protocols such as Session Initiation Protocol (SIP) or FTP on Juniper Networks devices running Junos OS. The ALG module is responsible for Application-Layer aware packet processing on switches1. The ALG can perform various functions such as modifying the payload and header of packets, opening secondary connections, translating addresses and ports, and applying security policies1. The ALG does not use software processes for permitting or disallowing specific IP address ranges, as this is the function of firewall filters or security zones2. The ALG does not use software that is used by a single TCP session using the same port numbers as the application, as this is the definition of a stateful firewall3. The ALG does not contain protocols that use one application session for each TCP session, as this is the characteristic of some application protocols such as HTTP or SMTP4. References:

• 1: ALG Overview | Junos OS | Juniper Networks
• 2: Firewall Filters Overview | Junos OS | Juniper Networks
• 3: Stateful Firewall Overview | Junos OS | Juniper Networks
• 4: Application Layer Protocols | Junos OS | Juniper Networks