1. Internet Protocol Formats
(seen as data structure diagrams)

2. IP (V4) Packet source address destination address
byte byte byte byte 3 4 8
Version IHL Serv. Type Total Length
Identifcation flags Fragment Offset
TTL Protocol Header Checksum 12 16 20
source address
destination address
options Unused Padding
data ... – up to 65 K including heading info

3. IP (V6) Packet source address destination address data – up to 65K
byte byte byte byte 3 4 8
Version Traffic Class (16) Flow Label (20 bits)
Payload Length Next Hops
source address 24 40
destination address
data – up to 65K

4. UDP Header IP Header UDP Header Data…. Source Port Destination Port
IP Header UDP Header Data….
UDP Header
byte byte byte byte 3 4 8
Source Port Destination Port
Length Checksum
data

5. TCP Header Sequence Number Acknowlegement Number U A P R S F Window
byte byte byte byte 3
Source Port Dest. Port
Sequence Number
Acknowlegement Number
U A P R S F Window
Offset Reserved
Checksum Urgent Pointer
options Unused Padding
Data
Like UDP... All this sits inside the data area of an IP packet

6. TFTP Protocol OpCode message RRQ/WRQ filename…
The opcode is one of: RRQ (read), WWQ (write), Data, ACK or ERROR
RRQ/WRQ filename…
DATA Block # data: 0–512 bytes (size in TCP header)
ACK Block #
ERROR Error # message
This is stored in the data area of the TCP header

7. RTPC (incomplete)
byte byte byte byte 3
Type Code Checksum

8. BOOTP
Source:

9. SMTP (basic)
byte byte byte byte 3
Type Code Checksum

10. ICMP (basic)
byte byte byte byte 3
Type Code Checksum

11. ICMP Type 3 – Dest. Unreachable
byte byte byte byte 3
Type Code Checksum
Unused
Internet Header + 64 bits of original datagram

12. ICMP Types 8 (echo) 0 (echo Reply)
byte byte byte byte 3
Type Code Checksum
Identifier Sequence Number
Data ....

13. ICMP Timestamp and Reply (Types 13,14 )
byte byte byte byte 3
Type Code Checksum
Identifier Sequence Number
Original Timestamp
receipt
Timestamp @ dest. reply