Drag and Drop Question Refer to the exhibit. Drag and drop the steps in the TCP/IP encapsulation process from the left onto the corresponding layer on the right. Answer:

The correct answer is adds a header to the user data; groups the data into segments and adds a header; groups the transport data into packets, adding a network header; groups the data into frames, adding a header and FCS trailer. TCP/IP Encapsulation: Layer-by-Layer Explanation The four steps map to the four layers of the TCP/IP model, top-down, as data travels from the application toward the physical medium. --- The Correct Order (Top → Bottom) | # | Step | TCP/IP Layer | |---|------|-------------| | 1…

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Question

Exhibit

Answer Area

Drag items

groups the data into frames, adding a header and FCS trailergroups the transport data into packets, adding a network headergroups the data into segments and adds a headeradds a header to the user data

Correct arrangement

adds a header to the user data
groups the data into segments and adds a header
groups the transport data into packets, adding a network header
groups the data into frames, adding a header and FCS trailer

Explanation

TCP/IP Encapsulation: Layer-by-Layer Explanation

The four steps map to the four layers of the TCP/IP model, top-down, as data travels from the application toward the physical medium.

The Correct Order (Top → Bottom)

#	Step	TCP/IP Layer
1	adds a header to the user data	Application
2	groups the data into segments and adds a header	Transport
3	groups the transport data into packets, adding a network header	Internet (Network)
4	groups the data into frames, adding a header and FCS trailer	Network Access (Data Link)

Why Each Item Goes Where It Does

1. "adds a header to the user data" → Application Layer

The Application layer is the entry point for user-generated data. Protocols like HTTP, DNS, and FTP prepend a protocol-specific header to raw user data. No segmentation or addressing happens yet - this is the simplest form of encapsulation. The result is called data or a message.

2. "groups the data into segments and adds a header" → Transport Layer

The keyword here is segments - the protocol data unit (PDU) unique to the Transport layer (TCP). TCP breaks the application data into manageable chunks and adds a header containing source/destination port numbers, sequence numbers, and acknowledgment numbers. UDP calls its PDU a datagram, but the concept is the same. Nothing below this layer uses the term "segment."

3. "groups the transport data into packets, adding a network header" → Internet Layer

The keyword is packets - the PDU of the Internet/Network layer. IP takes the transport segment and encapsulates it into a packet by adding a header with source and destination IP addresses. Notice the description says "network header," confirming this is the layer responsible for logical addressing and routing.

4. "groups the data into frames, adding a header and FCS trailer" → Network Access Layer

Two clues identify this as the bottom layer:

"frames" - the PDU of the Data Link / Network Access layer, containing MAC addresses in the header.
"FCS trailer" - the Frame Check Sequence is a CRC value appended at the end of the frame for error detection. This is the only layer in the TCP/IP model that adds a trailer, not just a header.

Common Mistakes and Misconceptions

Mistake	Correction
Confusing packets and segments	Segments = Transport; Packets = Network. These terms are not interchangeable on an exam.
Forgetting the FCS trailer	Students often think encapsulation only adds headers. The Data Link layer is unique in adding a trailer as well.
Skipping the Application layer	The Application layer does encapsulate - it adds a protocol header to user data. It's easy to think encapsulation only starts at Transport.
Mixing OSI and TCP/IP layers	In OSI there are 7 layers; in TCP/IP there are 4. "Network Access" in TCP/IP combines OSI's Data Link and Physical layers. Don't apply OSI numbering to a TCP/IP question.
Reversing the order	Encapsulation goes down (Application → Network Access). De-encapsulation on the receiving end goes up.

The mnemonic: Each layer wraps the layer above it - like envelopes within envelopes. The PDU names (data → segment → packet → frame) are the fastest way to identify which layer is being described on an exam.

Topics

#TCP/IP encapsulation#OSI layers#data encapsulation#network protocols

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