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Zorluk: OrtaEncapsulation and De-encapsulation

A network administrator is inspecting a packet capture file on a host receiving an automated file transfer. As the destination host de-encapsulates the incoming data unit from the physical network interface up to the application process, the protocol stack must inspect specific header fields to identify which higher-layer protocol or service should receive the payload next. Which of the following correctly identifies the sequential order of header fields evaluated at Layer 2, Layer 3, and Layer 4 to route the payload to the correct application process?

  1. EtherType in the Ethernet frame header, Protocol field in the IPv4 packet header, and Destination Port in the Transport segment headerCevap
  2. B
    Source MAC address in the Ethernet frame header, Time to Live (TTL) in the IPv4 packet header, and Source Port in the Transport segment header
  3. C
    Frame Check Sequence (FCS) in the Ethernet frame trailer, Header Checksum in the IPv4 packet header, and Sequence Number in the Transport segment header
  4. D
    Protocol field in the IPv4 packet header, EtherType in the Ethernet frame header, and Destination Port in the Transport segment header

Cevap

EtherType in the Ethernet frame header, Protocol field in the IPv4 packet header, and Destination Port in the Transport segment header
De-encapsulation is a bottom-up process where each OSI layer evaluates specific header fields to demultiplex and route the payload to the next higher layer protocol. At Layer 2 (Data Link), the EtherType field specifies the Layer 3 protocol (such as IPv4 or IPv6). At Layer 3 (Network), the Protocol field specifies the Layer 4 transport protocol (such as TCP or UDP). At Layer 4 (Transport), the Destination Port number identifies the target service or process at the Application layer.

Adım Adım Çözüm

1
Analyze Layer 2 de-encapsulation requirements
The network interface card processes the Ethernet frame header and evaluates the EtherType field (e.g., 0x0800 for IPv4) to determine which Network layer protocol driver should process the frame payload.
Layer 2 headers use EtherType to demultiplex traffic to the proper Layer 3 protocol.
2
Analyze Layer 3 de-encapsulation requirements
The Internet Protocol driver processes the IPv4 packet header and evaluates the Protocol field (e.g., 6 for TCP, 17 for UDP) to determine which Transport layer protocol module receives the packet payload.
Layer 3 headers use the Protocol field to demultiplex traffic to the proper Layer 4 protocol.
3
Analyze Layer 4 de-encapsulation requirements
The Transport layer protocol processes the segment header and evaluates the Destination Port number to direct the data payload to the specific socket/application bound to that port.
Layer 4 headers use port numbers to direct data to the correct application layer process.

Anahtar Kavram

De-encapsulation Demultiplexing Fields
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Konular

Encapsulation and De-encapsulation

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