Internet Protocol Formats IP V 4 Packet byte

Internet Protocol Formats

IP (V 4) Packet byte 0 byte 1 IHL Length Serv. Type Version Identifcation TTL Protocol byte 2 byte 3 Total flags Fragment Offset Header Checksum source address destination address options. . . data. . . – up to 65 K including heading info Unused Padding

IP (V 6) Packet byte 0 byte 1 Version Traffic Class (16) Payload Length byte 2 byte 3 Flow Label (20 bits) Next source address destination address data – up to 65 K Hops

UDP Header byte 0 byte 1 byte 2 byte 3 Source Port Destination Port Length Checksum data. . This sites in the data portion of the IP packet. LIterally, its the next layer.

TCP Header byte 0 byte 1 Source Port byte 2 byte 3 Dest. Port Sequence Number Acknowlegement Number Offset Reserved UAPRSF Checksum Window Urgent Pointer options. . . Unused Padding Data. . . . Like UDP. . . All this sits inside the data area of an IP packet

ICMP (basic) byte 0 byte 1 Type Code byte 2 byte 3 Checksum

ICMP Type 3 – Dest. Unreachable byte 0 Type byte 1 byte 2 Code byte 3 Checksum Unused Internet Header + 64 bits of original datagram

ICMP Types 8 (echo) 0 (echo Reply) byte 0 byte 1 Type Code Identifier byte 2 byte 3 Checksum Sequence Number Data. .

ICMP Timestamp and Reply (Types 13, 14 ) byte 0 byte 1 Type Code Identifier byte 2 byte 3 Checksum Sequence Number Original Timestamp @dest receipt Timestamp @ dest. reply