TCP/IP OSI Model

Segment

TCP Segment

Source Port	Destination Port	Sequence Number	Acknowledgement Number	Header Length	Reserved	Control Bits	Window Size	Checksum	Urgent	Options	Application Layer Data
2 bytes	2 bytes	32 bits	32 bits	4 bits	6 bits	6 bits	2 bytes	2 bytes	2 bytes	Size Varies	Size Varies

UDP Datagram

Source Port	Destination Port	Length	Checksum	Application Layer Data
2 bytes	2 bytes	2 bytes	2 bytes	Size Varies

Packet

IPv4 Packet Fields

Version

Internet Header Length

Differentiated Services (DS)

Total Length

Identification

Flags

Fragment Offset

Time-to-Live

Protocol

Header Checksum

Source IP Address

Destination IP Address

Options

Padding

4 bits

DSCP

ECN

2 bytes

3 bits

13 bits

1 byte

2 bytes

32 bits

Variable maximum
40 bytes padded with 0’s

6 bits

2 bits

IPv6 Packet Fields

Version	Traffic Class	Flow Label	Payload Length	Next Header	Hop Limit	Source Address	Destination Address
4 bits	1 byte	2 bytes	2 bytes	1 byte	1 byte	128 bits	128 bits

Frame

Generic Frame Fields

Header	Packet	Trailer
Frame Start	Addressing	Type	Control	Data	Error Detection	Frame Stop

Ethernet II Frame Fields

Preamble	Destination Address	Source Address	Protocol Type	Data	Frame Check Sequence
8 bytes	6 bytes	6 bytes	2 bytes	46 – 1500 bytes	4 bytes

IEEE 802.3 Frame Fields

Preamble	Destination Address	Source Address	Length	802.2 Header and Data	Frame Check Sequence
8 bytes	6 bytes	6 bytes	2 bytes	46 – 1500 bytes	4 bytes

IEEE 802.3ac Frame Fields

Preamble	Destination Address	Source Address	802.1Q VLAN Tag	802.2 Header and Data	Frame Check Sequence
8 bytes	6 bytes	6 bytes	2 bytes	46 – 1500 bytes	4 bytes

802.1Q VLAN Tag
Tag Protocol ID 0x8100	User Priority	Canonical Format Indicator	VLAN ID
2 bytes	3 bits	1 bit	12 bits

PPP Frame Fields

Flag	Address	Control	Protocol	Data	Frame Check Sequence
1 byte	1 byte	1 byte	2 bytes	variable	2 or 4 bytes

Wireless Frame Fields:

Frame Control	Duration/ID	Destination Address	Source Address	Receiver Address	Sequence Control	Transmitter Address	Frame Body	Frame Check Sequence
Fragment Number	Sequence Number
2 bytes	2 bytes	6 bytes	6 bytes	6 bytes	4 bits	12 bits	6 bytes	0-2312 bytes	4 bytes

Frame Control
Protocol Version	Type	Subtype	To DS	From DS	More Fragments	Retry	Power Management	More Data	WEP	Order
2 bits	2 bits	4 bits	1 bit	1 bit	1 bit	1 bit	1 bit	1 bit	1 bit	1 bit