The Hop

Addresses Stay Put

The toy hop leaves source, destination, and protocol fields alone.

highlighted = computed this step

The endpoint fields stay put

This toy hop does not change the source address, destination address, or protocol field.

protocol=6\text{protocol}=6
What stays putThe before and after IPv4 headers are shown as exact field strips.Before header160 bits / 20 bytes0x4500003c1c4640004006b1e6ac100a63ac100a0cbyte 0byte 1byte 2byte 301000101000000000000000000111100byte 4byte 5byte 6byte 700011100010001100100000000000000byte 8byte 9byte 10byte 1101000000000001101011000111100110byte 12byte 13byte 14byte 1510101100000100000000101001100011byte 16byte 17byte 18byte 1910101100000100000000101000001100version4ihl5dscp-ecn0x00total-length60identification0x1c46fragment-offset0ttl64protocol6->TCPheader-checksum0xb1e6source172.16.10.99destination172.16.10.12reserved: clear df: set mf: clearAfter header160 bits / 20 bytes0x4500003c1c4640003f06b2e6ac100a63ac100a0cbyte 0byte 1byte 2byte 301000101000000000000000000111100byte 4byte 5byte 6byte 700011100010001100100000000000000byte 8byte 9byte 10byte 1100111111000001101011001011100110byte 12byte 13byte 14byte 1510101100000100000000101001100011byte 16byte 17byte 18byte 1910101100000100000000101000001100version4ihl5dscp-ecn0x00total-length60identification0x1c46fragment-offset0ttl63protocol6->TCPheader-checksum0xb2e6source172.16.10.99destination172.16.10.12reserved: clear df: set mf: clear

Source address

The source remains 172.16.10.99.

source=172.16.10.99\text{source}=172.16.10.99
What stays putThe before and after IPv4 headers are shown as exact field strips.Before header160 bits / 20 bytes0x4500003c1c4640004006b1e6ac100a63ac100a0cbyte 0byte 1byte 2byte 301000101000000000000000000111100byte 4byte 5byte 6byte 700011100010001100100000000000000byte 8byte 9byte 10byte 1101000000000001101011000111100110byte 12byte 13byte 14byte 1510101100000100000000101001100011byte 16byte 17byte 18byte 1910101100000100000000101000001100version4ihl5dscp-ecn0x00total-length60identification0x1c46fragment-offset0ttl64protocol6->TCPheader-checksum0xb1e6source172.16.10.99destination172.16.10.12reserved: clear df: set mf: clearAfter header160 bits / 20 bytes0x4500003c1c4640003f06b2e6ac100a63ac100a0cbyte 0byte 1byte 2byte 301000101000000000000000000111100byte 4byte 5byte 6byte 700011100010001100100000000000000byte 8byte 9byte 10byte 1100111111000001101011001011100110byte 12byte 13byte 14byte 1510101100000100000000101001100011byte 16byte 17byte 18byte 1910101100000100000000101000001100version4ihl5dscp-ecn0x00total-length60identification0x1c46fragment-offset0ttl63protocol6->TCPheader-checksum0xb2e6source172.16.10.99destination172.16.10.12reserved: clear df: set mf: clear

Destination address

The destination remains 172.16.10.12. Payload bytes are not modeled in this header-only toy.

destination=172.16.10.12\text{destination}=172.16.10.12
What stays putThe before and after IPv4 headers are shown as exact field strips.Before header160 bits / 20 bytes0x4500003c1c4640004006b1e6ac100a63ac100a0cbyte 0byte 1byte 2byte 301000101000000000000000000111100byte 4byte 5byte 6byte 700011100010001100100000000000000byte 8byte 9byte 10byte 1101000000000001101011000111100110byte 12byte 13byte 14byte 1510101100000100000000101001100011byte 16byte 17byte 18byte 1910101100000100000000101000001100version4ihl5dscp-ecn0x00total-length60identification0x1c46fragment-offset0ttl64protocol6->TCPheader-checksum0xb1e6source172.16.10.99destination172.16.10.12reserved: clear df: set mf: clearAfter header160 bits / 20 bytes0x4500003c1c4640003f06b2e6ac100a63ac100a0cbyte 0byte 1byte 2byte 301000101000000000000000000111100byte 4byte 5byte 6byte 700011100010001100100000000000000byte 8byte 9byte 10byte 1100111111000001101011001011100110byte 12byte 13byte 14byte 1510101100000100000000101001100011byte 16byte 17byte 18byte 1910101100000100000000101000001100version4ihl5dscp-ecn0x00total-length60identification0x1c46fragment-offset0ttl63protocol6->TCPheader-checksum0xb2e6source172.16.10.99destination172.16.10.12reserved: clear df: set mf: clear

Summary

This one-hop model changes TTL and checksum, while source, destination, protocol, and payload idea stay outside the edit.

changed header fields=2\text{changed header fields}=2
What stays putThe before and after IPv4 headers are shown as exact field strips.Before header160 bits / 20 bytes0x4500003c1c4640004006b1e6ac100a63ac100a0cbyte 0byte 1byte 2byte 301000101000000000000000000111100byte 4byte 5byte 6byte 700011100010001100100000000000000byte 8byte 9byte 10byte 1101000000000001101011000111100110byte 12byte 13byte 14byte 1510101100000100000000101001100011byte 16byte 17byte 18byte 1910101100000100000000101000001100version4ihl5dscp-ecn0x00total-length60identification0x1c46fragment-offset0ttl64protocol6->TCPheader-checksum0xb1e6source172.16.10.99destination172.16.10.12reserved: clear df: set mf: clearAfter header160 bits / 20 bytes0x4500003c1c4640003f06b2e6ac100a63ac100a0cbyte 0byte 1byte 2byte 301000101000000000000000000111100byte 4byte 5byte 6byte 700011100010001100100000000000000byte 8byte 9byte 10byte 1100111111000001101011001011100110byte 12byte 13byte 14byte 1510101100000100000000101001100011byte 16byte 17byte 18byte 1910101100000100000000101000001100version4ihl5dscp-ecn0x00total-length60identification0x1c46fragment-offset0ttl63protocol6->TCPheader-checksum0xb2e6source172.16.10.99destination172.16.10.12reserved: clear df: set mf: clear