OSI Model | Packets | Glossaries | IPv4 Address Classes | Subnetting | Powershell
Transport Layer
| TCP Segment | |||||||||||||||||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | 21 | 22 | 23 | 24 | 25 | 26 | 27 | 28 | 29 | 30 | 31 | 32 |
| Source port(16) | Destination port(16) | ||||||||||||||||||||||||||||||
| Sequence number(32) | |||||||||||||||||||||||||||||||
| Acknowledgement number(32) | |||||||||||||||||||||||||||||||
| Header length(4) | empty(6) | Control flags(6) | Window(16) | ||||||||||||||||||||||||||||
| checksum(16) | Urgent(16) | ||||||||||||||||||||||||||||||
| Options(0 or 16 if any) | Padding | ||||||||||||||||||||||||||||||
| Data payload(varies) | |||||||||||||||||||||||||||||||
Control Flags:
URG (urgent)
ACK (acknowledged)
PSH (push)
RST (reset)
SYN (synchronize)
FIN (finish)
Network Layer
| IP Datagram | |||||||||||||||||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | 21 | 22 | 23 | 24 | 25 | 26 | 27 | 28 | 29 | 30 | 31 | 32 |
| Version(4) | Header Len(4) | Service Type(8) | Total Len(16) | ||||||||||||||||||||||||||||
| Identification(16) | Flags(3) | Fragment Offset(13) | |||||||||||||||||||||||||||||
| TTL(8) | Protocol(8) | Header Checksum(16) | |||||||||||||||||||||||||||||
| Source IP Address(32) | |||||||||||||||||||||||||||||||
| Destination IP Address(32) | |||||||||||||||||||||||||||||||
| Options | Padding | ||||||||||||||||||||||||||||||
Data Link Layer
| 802.3 Ethernet packet and frame structure | |||||||||
|---|---|---|---|---|---|---|---|---|---|
| Layer | Preamble | Start Frame Delimiter(SFD) | MAC Destination | MAC Source | 802.1Q tag (optional) | Ethertype or length | Payload | Frame check sequence | Interpacket gap |
| 7 octets | 1 octets | 6 octets | 6 octets | 4 octets | 2 octets | 46-1500 octets | 4 octets | 12 octets | |
Preamble: Indicates starting of the frame and allow sender and receiver to establish bit synchronization
Start Frame Delimiter(SFD): This is a 1-Byte field that is always set to 10101011. SFD indicates that upcoming bits are starting the frame, which is the destination address
MAC Destination Address: This is a 6-Byte field that contains the MAC address of the machine for which data is destined
MAC Source Address: This is a 6-Byte field that contains the MAC address of the source machine. As Source Address is always an individual address (Unicast), the least significant bit of the first byte is always 0
Ethertype or Length: Length is a 2-Byte field, which indicates the length of the entire Ethernet frame. This 16-bit field can hold a length value between 0 to 65534, but length cannot be larger than 1500 Bytes because of some own limitations of Ethernet
Payload: Both IP header and data will be inserted here if Internet Protocol is used over Ethernet. The maximum data present may be as long as 1500 Bytes
Frame Check Sequence: An error-detecting code added to a frame in a communication protocol
Interpacket Gap: A pause which may be required between network packets or network frames depending on the physical layer protocol or encoding used
| 802.11 packet and frame structure | |||||||||
|---|---|---|---|---|---|---|---|---|---|
| Frame Control(2) | Duration/ID(2) | Address 1(6) | Address 2(6) | Address 3(6) | Sequence Control(2) | Address 4(6) | Data Payload | FCS(4) | |