PDU Header Format
IS-IS packets are encapsulated into link layer frames. The Protocol Data Unit (PDU) consists of two parts, the headers and the variable length fields. The headers comprise the PDU common header and the PDU specific header. All PDUs have the same PDU common header.
Layers of TCP/IP Model
The TCP/IP model is based on a five-layer model for networking. From bottom (the link) to top (the user application), these are the physical, data link, net- work, transport, and application layers.
OSI Model
In the OSI reference model, the communications between a computing system are split into seven different abstraction layers: Physical, Data Link, Network, Transport, Session, Presentation, and Application.
Layer 6 of OSI Model
Layer 6 of The OSI Model: Presentation Layer is the layer of the ISO Open Systems Interconnection (OSI) model that establishes context between application-layer entities, in which the higher-layer entities may use different syntax and semantics if the presentation service provides a mapping between them.
Layer 7 in Networking
Layer 7 refers to the outermost seventh layer of the Open Systems Interconnect (OSI) Model. This highest layer, also known as the application layer, supports end-user applications and processes. This layer is closest to the end user and is wholly application-specific.
Layer 7 Firewall
What is a Layer 7 Firewall? A layer 7 firewall, as the name suggests, is a type of firewall that operates on the OSI model’s 7 layers. Rather than filtering traffic based on IP addresses, layer 7 firewalls can investigate the contents of data packets to determine whether they include malware or other cyber dangers.