Which Layer Does This? — TechKnowSurge

About this interactive

Layers 5 to 7 (application, presentation, session): for a protocol such as HTTP these act as one layer, an application such as Chrome talking to one such as Apache. The unit is data. HTTPS adds TLS encryption to HTTP. Layer 4, transport (segment): TCP breaks data into segments and numbers them, sets up and closes connections with the three-way handshake, addresses the service with a port number (80 for HTTP, 443 for HTTPS), resends what was lost and controls the flow. UDP is a simpler layer 4 protocol that does not do all of this. Layer 3, network (packet): IPv4, IPv6 and ICMP. The IP header carries the source and destination IP addresses, and routers use the destination to choose the next hop. Layer 2, data link (frame): local delivery, with MAC addresses and a header and trailer that each router strips and rebuilds for the next link. Layer 1, physical (bits): the ones and zeros as signals on the medium, starting with the preamble, which lets the receiving card synchronise to the signal. The card then discards the preamble, which is why Wireshark never shows it.

What you'll learn

Assign a job, or a field from a Wireshark capture, to the OSI layer responsible for it: application data at layers 5 to 7, ports, sequencing and connections at layer 4, IP addressing and routing at layer 3, local MAC delivery at layer 2, and signals at layer 1
Name the protocol data unit at each layer: data, segment, packet, frame and bits

Aligned to

CompTIA Network+

1.1 Explain concepts related to the Open Systems Interconnection (OSI) reference model.

Cisco CCNA

1.1 Explain the role and function of network components

Cisco CyberOps Associate

4.8 Interpret the fields in protocol headers as related to intrusion analysis

ISC2 CC

4.1 Understand network security

Cisco CCST Networking

1.1 Identify the fundamental conceptual building blocks of networks

Key terms

Open Systems Interconnection Model: A conceptual framework that standardizes network communication into seven distinct layers.
Transport Layer: Layer 4 of the OSI model, responsible for end-to-end communication, flow control, and error recovery.
Network Layer: Layer 3 of the OSI model, responsible for logical addressing and routing data packets between networks.
Data Link Layer: Layer 2 of the OSI model responsible for node-to-node data transfer and error detection on a single network segment.
Physical Layer: Layer 1 of the OSI model, responsible for the transmission of raw bits over a physical medium.
Protocol Data Unit: The unit of information passed between peer entities at the same OSI layer, with layer-specific names: segment or datagram at the Transport layer, packet at the Network layer, frame at the Data Link layer, and bit at the Physical layer. Understanding PDU terminology is fundamental to troubleshooting network communication at each layer.
Preamble: A 7-octet sequence of alternating 1s and 0s transmitted at the start of an Ethernet packet to synchronize the clock timing between communicating devices.

Topics

Open Systems Interconnection Model Transport Layer Network Layer Data Link Layer Physical Layer Interactive Categorize

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