Interactive · Scroll-driven · Reversible

TCP/IP Encapsulation

Watch a TFTP file transfer travel down the OSI stack. Each layer drags the packet in from above and appends its own header around it. Scroll down to transmit, scroll up to reverse.

TFTPUDPIPv4Ethernet IISignals
start scrolling
↓
L7
Application Layer
TFTP · PDU: Message
OSI Layer 7

Data origination — application generates request/data

TFTP HEADER GENERATION✓ built
FILE DATA
firmware.bin · block #1 · 512 B
4649524D5741524500010000000055AA ···
+ TFTP HEADER ↓
Opcode
0x03 (DATA)
2B
Block #
0x0001
2B
PDU:
TFTP
DATA ██████
↓ scroll — UDP layer encapsulates this
↓TFTP hands off to UDP↓
L4
Transport Layer
UDP · PDU: Datagram
OSI Layer 4

End-to-end delivery — port-based multiplexing, no connection overhead

UDP HEADER GENERATION✓ built
TFTP
Message · handed down ↓
Opcode
0x03 (DATA)
Block #
0x0001
DATA →File Data (512 bytes)
+ UDP HEADER ↓
Src Port
61234
2B
Dst Port
69 (TFTP)
2B
Length
524 bytes
2B
Checksum
0xA4F2
2B
PDU:
UDP
TFTP
DATA ██████
↓ scroll — IPv4 layer encapsulates this
↓UDP hands off to IPv4↓
L3
Network Layer
IPv4 · PDU: Packet
OSI Layer 3

Logical addressing — routes datagrams across networks

IPv4 HEADER GENERATION✓ built
UDP
Datagram · handed down ↓
Src Port
61234
Dst Port
69 (TFTP)
Length
524 bytes
Checksum
0xA4F2
DATA →TFTP Packet (516 bytes)
+ IPv4 HEADER ↓
Ver / IHL
0x45
1B
TTL
64
1B
Protocol
17 (UDP)
1B
Src IP
192.168.1.10
4B
Dst IP
192.168.1.1
4B
PDU:
IPv4
UDP
TFTP
DATA ██████
↓ scroll — Ethernet II layer encapsulates this
↓IPv4 hands off to Ethernet II↓
L2
Data Link Layer
Ethernet II · PDU: Frame
OSI Layer 2

Physical addressing — local LAN delivery via MAC

Ethernet II HEADER GENERATION✓ built
IPv4
Packet · handed down ↓
Ver / IHL
0x45
TTL
64
Protocol
17 (UDP)
Src IP
192.168.1.10
Dst IP
192.168.1.1
DATA →UDP Datagram (524 bytes)
+ Ethernet II HEADER ↓
Dst MAC
AA:BB:CC:DD:EE:FF
6B
Src MAC
11:22:33:44:55:66
6B
EtherType
0x0800 (IPv4)
2B
FCS
0x1A2B3C4D
4B
PDU:
Ethernet II
IPv4
UDP
TFTP
DATA ██████
↓ scroll — Signals layer encapsulates this
↓Ethernet II hands off to Signals↓
L1
Physical Layer
Signals · PDU: Bits
OSI Layer 1

Bit transmission — electrical / optical / radio signals

BIT STREAM →
10101010 10101011 00000001 00000110 01000101 01000000 00010001 11000000 10101000 00000001 ...
Signals HEADER GENERATION✓ built
Ethernet II
Frame · handed down ↓
Dst MAC
AA:BB:CC:DD:EE:FF
Src MAC
11:22:33:44:55:66
EtherType
0x0800 (IPv4)
DATA →IP Datagram (544 bytes)
+ Signals HEADER ↓
Encoding
Manchester / NRZ-L
—
Medium
Cat6 / Fiber / WiFi
—
Bitrate
1 Gbps
—
PDU:
Signals
Ethernet II
IPv4
UDP
TFTP
DATA ██████
✓ Frame ready for transmission
✓ TRANSMISSION COMPLETE

Complete Encapsulation

The TFTP data payload has been wrapped by 4 protocol headers and is ready for physical transmission as an Ethernet frame.

Ethernet
IPv4
UDP
TFTP
DATA ████████████
FCS
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